Note: Descriptions are shown in the official language in which they were submitted.
s
This application is a division of Serial No. 334,639,
filed August 27, 1979.
The present invention relates to hollow microspheres
formed from inorganic film forming materials and having a gaseous
material under high pressure within the contained volume of the
microsphere. Preferably, the inorganic film forming material is
glass and the invention is hereinafter described in that context.
The present invention also relates to hollow glass micro-
spheres having a gaseous material under high pressure within the
contained volume of the microspheres and having a metal coating
deposited on the inner wall surface of the microsphere.
The present invention also relates to the use of the
hollow glass microspheres and the hollow glass microspheres
having a transparent or reflective coatiny deposited on the inner
wall surface thereof for the handl:ing and storage of gaseous
materials under high pressure. The hollow glass microspheres of
the present invention, depending on their diameter and their wall
thickness and the particular glass composition from which they
are made, are capable of withstanding very high internal gas
pressures. The hollow glass microspheres are resistant to high
temperatures, stable to many chemical agents and weathering
conditions. These characteristics make them suitable for the
handling and storage of gaseous materials generally and particular-
ly for toxic and corrosive gaseous materials at high pressures.
~'
.
~s~rss
The hollow glass microspheres of the present invention,
depending on their diameter and their wall thickness and the
particular glass composition from which they are made~ are
capable of withstanding relatively high internal pressures and/or
external weight.
BACKGROU`~D OF THE I~VEMTION
5 5
In recent ~lears, the substantial increases in
the costs o~ handling and storage of gaseous
macerials has created an incentive for improved
methods of handling and storage of gaseous
materials. The manufacture of highly to~ic,
corrosive and/o~ poisonous gases or waste gases
has created a serious problem of handling and
storage of ~he materials and/or of disposal of
unwanted materials. Environmental problems have
been created by che need to find adequate and
safe means or handling and storing radioactive
atomic energv fuel and fuel waste materials.
There has also developed a need in inertial con-
finement fusion systems ror a means of obtainingunder high pressure small target fuel materials
contained in a material from which they do not
difuse or do not dif~use at a high rate.
Hollow glass microspheres have been used as
micro-containers ~or mixtures of hydrogen isotope
gases which were used as laser targets to obtain
or attempt to obtain thermonuclear reac~ions.
However, the method of making the glass micro-
spheres, the microspheres themselves and tne
method or ~illi~g the microspheres have several
disadvan~ages. The commerciallv available gl2ss
microspneres are made bv grinding glass ~o a
desired particle size and heating the ground
particles to a high temperature to "blow" the
3~ particles into hollow glass microspheres. The
"blowing" gas in the known procedure is gas
that had been trapped in the glass during the
manufacture of the glass. The microspher~s
that are obtained are of non-uniform size,
shape and wall thickness and have contained
in the walls thereof small trapped gas bubbles.
-- 3 --
~ ~3~ ~ 5
....
The microsphere3 that are to be used as laser
~uel targets must be of uniform size and wall
~hickness as a consequence of whicn only a very
small proportion of the comme-ciall~ produced
microspheres can be used, for e~ample, one in a
million. Further, the gas used to blow the micro-
spheres mus~ be purged and the desired h~Jdrogen
. isotope gases introduced into the microspheres.
The method now used to introduce the hydrogen
isotope gases into the microspheres involves
relatively nigh temperature and very high pressure
gas permeation or diffusion techniques. The hydro-
gen gases under high pressure are made to slowly
diffuse through the "pores" of the glass micro-
sphere and displace the internal gas in the micro-
sphere. Cooling the microspheres and maintaining
the microspheres under refrigeraticn can sub-
stantially reduce loss of the gases thus co~l-
pressed into the microspheres. Over a long
period of time, however, signi~icant amounts of
the compressed gases dirLuse out of the micro-
spheres wnich results in a loss of the hydrogen
gases fuel and efficiency of the thermonuclear
~ eaccion.
.~ S The known methods ror produci~g nollow
glass mic-osphere~ have not been successful in
producing microspheres of relativelv unifor~
si~e or uniform thin walls which makes it very
dirricul~ to~produce hollow glass microspheres
or controlled and predictable characteristics
and quality and strength or at low cost which
are capable of containing elevated internal
gas pressures without significant pressure loss.
- 4 -
An inherent problem with the known method of
ma~ing microspheres is that since the glass micro-
spheres had to be su~ficiently porous tc allow the
gases to diffuse into the mîcrospheres some of the
pressurized gases will diffuse ou~ of the micro-
spheres. Another problem is that the method is
limi~ed to the use of low molecular weight gases
for diffusing into the microspheres. There is
the additional problem that the prior art
pressurized microspheres are required to be
maintained under re rigeration to minimi2e outward
diffusion of the oressurized gases.
A serious problem that e~ists with the known
mechod is that t:ne small gas bubbles that are
trapped in the walls of the microspheres during
manufacture of the microspneres weakens the
microspheres, thus limiting to some exten~ the
amount oE hydrogen isotope gases or other gases,
that is the pressure of the gases, that can be
coneained in the microspheres.
The ~nown methods of producing hollow glass
microspheres, for e~Yample t as disclosed in the
Veacch e~ al U.S. Patent 2,797,201 or Beck et al
U.S. Paten~ 3,365,315, involve disoersing a
liquid and/or solid gas-~hase ?recursor material
in the gla-~s material to be blown to form the
microspheres. The glass material containing
the solid or liquid gas-phase precursor enclosed
therein is then heated to convert the solid
and/or liquid gas-phase precursor material into
a gas and is further heated ~o expand the gas
and produce ~he hollow glass microsphere con-
taining therein the expanded gas. This proce~s
is~ understandably, dif~icult to control and of
.~ _ _ _ . . . _
-
s
necessity, i.e. inherently, produces glass
microspheres of random size and wall thickness,
microspheres with walls that have sectlons
or portions of the walls that are relatively
thin, walls that have holes, small trapped
bubbles, trapped or dissolved gases, any
one or more of which will resul~ in a sub-
stantial weakening of the microspheres,
and a subs~antial number or proportion of
microspheres which are not suitable foruse which must be scrapped or recycled.
Also, the relatively high cos~ and the
relatively small size of the prior art
microspheres has limited their use.
Further, the known methods fo~ pro-
ducing hollow glass microspheres usually
rely on high sod~ content ~lass compositions
because of their relatively low melting
temperatures. These glass compositions,
however, were found to have poor long term
weathering characteristics and a relatively
high mean atomic number.
In addition, applican~ round in his initial
attempts to use an inert blor.~ing gas to blow a
thin molcen glass ~ilm to form a microsphe~e
thac the rormation of the ~lass microsphere
was extremely sensitive and that unstable glass
.. . . . .... . . .. .. ... . . . .
films were produced which burst into minute sprays
of droplets before a molten glass film could be
blown into a microsphere and detached from a blowing
nozzle. There was also a tendency for the molten
glass fluid to creep up the blowing nozzle under
the action of wetting forces. Thus, the initial
attempts to blow hollow glass microspheres from
thin molten glass films were unsuccessful.
In addition, in some applications, the use
of low density microspheres presents a serious
~roblem because chey are difficult to handle
si.nce thev are readily elutriated and tend to
blow aboue. In situations of this type, the
filamented microspheres of the present invention
provide a convenient and safe method of handling
the microspheres.
.1~51~ ~5S
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention, there are provided hollow
inorganic film forming material microspheres of substantially
uniform diameter of 200 to 10,000 microns and of substantially
uniform wall thickness of 0.1 to 1,000 microns and having a
contained gas pressure above 15 p.s.i.g. at ambient temperature,
wherein said microspheres are free of latent solid or liquid
blowing gas materials or gases and the walls of said microspheres
are substantially free of holes, relatively thinned wall portions
or sections, sealing tips and bubbles.
According to a further aspect of the present invention, there
are provided filamented, hollow inorganic film forming material
microspheres having a diameter of 200 to 10,000 microns, having a
wall thickness of 0.1 to 1,000 microns and having a contained gas
pressure above 15 p.s.i.g. at ambient temperature, wherein said
microspheres are connected to each other by filament portions
which are continuous with the microspheres and are of the same
inorganic film forming material from ~hich the microspheres are
made.
Preferably the inorganic film forming material is glass and,
as stated above, the invention is discussed herein in that context.
The microspheres are made from a glass composition selected
for the particular gaseous material to be contained therein. ThP
microsphere can also be made to contain a metal coating deposited
on the inner wall surface of the microspheres. The metal coating,
depending on its thickness, can be transparent or reflective.
_ ~ _
S
The glass microspheres of the present invention can be
used to handle and store gaseous materials, generally such as
oxygen, hydrogen, nitrogen and carbon dioxide; toxic, corrosive
and/or poisonous and/or waste gases and radioactive atomic energy
fuel material
- 8a -
r3~,55
and fuel waste material and in the handling and
storage of unstable gases. ~he microspheres can
be used in the manufacture of laser fuel targets
for hydrogen fusion reactor research and reactors.
An advantageous use of the hollow microspheres
is in the manufacture of laser ~uel targets for
inertial confinement fusion systems and reactors.
Par~icular and advantageous uses of the
hollow glass microspheres are for the storage
of a~omic fuel waste materials and the ~anufacture
of laser ruel targets ~or inertial confinement
fusion systems and reactors.
The hollow glass microspheres of the present
invention are preferably made by forming a liauid film of
molten glass across a coaxial blowing nozzle,
applying the blowing gas at a positive pressure
on the inner surface o the glass film to blow~
the ilm and Eorm an elongated cylinder shaped
liquid film of molten glass which is closed at
its outer end. The hollow glass microspheres
of the present invention can also be made by
using as the blowing gas a gas containing a metal
vapor, dispersed metal particles and/or an organo
metal co~pound. .~ balancing but slightly lower
gas p.essure is provided :in the area oE
~ the blowing nozzle into which the elongated
-; cylinder shaped liquid ~ilm is blown.
` A transverse jet is used to direct an inert
entraining fluid over and around the blowing
nozzle a~ an angle to the axis of the blowing
nozzle. T~e entraining fluid as it passes
over and around the blowing nozzle and the
elongated cylinder ~luid dynamically induces a
pulsating or fluctuating pressure field at
the opposite or lee side o~ the blowing nozzle
. . .
in the wake or shadow o~ the blowing nozzle.
The fluctuating pressure field has regular
periodic laceral oscillations similar to those
of a flag flapping in a breeze. The transverse
jet entraining fluid can also be pulsed at
regular intervals to assist in controlling
~he size of the microspheres and in separating
the microspheres from the blowing nozzle
and the distance or spacing between micro-
spheres.
The entraining fluid envelops and actsasymmetrically on the elongated cylinder and
causes the cylinder to flap, fold, pinch and
close-off at its inne- end at a point pro~ima~e
to the coaxial blowing nozzle. The continued
movement of the entraining fluid over the
elongated cylinder produces fluid drag forces
on the cylinder and detaches the elongated
cylinder fro~ the coaxial blowing nozzle to have
it fall from the blowing nozzle. The surface
tension ~orces of the molten glass act on the
now free falling elongated cylinder and cause
the cylinder to seek a minimum su~face are~ and
to form a spherical shape.
Quench nozzles are disposed below and on
either side of the blowing nozzle and direct
cooling fluid at and into contact with the
molten ~lass microspheres ~o rapidly cool and
solidify ~he molten glass and ~orm a hard,
smooth hollow glass microsphere. Where a metal
vapor in ad~ixture wi~h a blowin~ gas is used
to blow the microspheres, the quench fluid
cools and condenses the metal vapor and causes
the metal vapor to deposit on the inner wall
surface of the microsphere as a transparent
-- 10 --
;;r~d~55
metal coating or a thin refleccive metal coating.
The microspheres can be made from glass
compositions selected for their desired optical
and chemical properties and for the particular
gaseous material to be contained therein.
T.~ere a gas containing dispersed metal
particles is used to blow the microspheres, a
metal layer is deposited on the inner wall
surface of the microsphere as a thin metal
coating. Whêre a gaseous organo metal compound
is used to deposit the metal laver, a gaseous
organo metal compound is used as or with the
blowing gas tO blcw the microspheres. The
organo metal compound can be decomposed just
prior to blowing the microspheres or after
the microspheres are formed by, for e~ample,
subjectin~ the blowing gas or the microspheres
to heat and/or an electrical discharge means.
The filamented microspheres are preferably made in a
manner such that they are connected or attached
to each other by a thin continuous glass fila-
ment. The filamented microspheres also assist
in handling and preventing sca~cering of micro-
spheres, particularly r~here very s;nall diameter
~5 microspheres or low densiry microsp'neres are
produced.
-
THE ADVANT.~GES
5 5
The present invention overcomes many o~ theproblems associated wi~h prior attempts to pro-
duce hollow glass microspheres containing and/or
to con~ain gaseous materials at high pressures.
The process and apparatus of the present invention
allows the production of hollow gl2ss microspheres
having ~redetermined diameters, wall thicknesses,
strength and resistance to chemical agents and
weathering and gas permeability such that imDroved
systems can be designed, manufactured and tailor
made ~or storage and handling of contained gases
to suit a particular desired use. The diameter,
wall chickness and unirormity and the strength
and resistance to chemical agents characteristics
or the microspheres can be determined by carefully
selecting the cons~ituents of the glass
composicion and controlling the blowing gas
pressure and temperature and viscosity and
thickness of the molten glass film from wnich
the microspheres are fonned. The inner volume
o~ the microspheres contains at high pressure
the gaseous material used to Slow the micro-
sphere which is to be ma:intained with the micro-
2S sphere. The hollow glass microspheres can havea transparent or a reflective metal coating
deposited on the inner wall surface of the
microsphere. The reflective metal coating
re~lects light and reduces the possibility
of photochemically induced chemical reactions
occurring in ~he high pressure gaseous
materials contained within the microspheres~
iO55
BRIEF DESCRIPTION OF THE DRAWING5
The attached drawings illustrate exemplary forms of
a method and apparatus ~or making microspheres according
to the invention for use in compressing gases at high
pressure in.a contained volume.
The Figure 1 of the drawings shows in
cross-section an appara~us having multi?le
coa~ial blowing nozzle means fo~ supplying the
gaseous materials for blowing hollow glass micro-
spheres, a transverse jet providing an entraininCrluid to assist in the formation and de~achmenc
or the microspheres from tne blowing nozzles,
and means for supDl~Jing a quench fluid to cool
the microspheres.
The Figure ~ of the drawings is an enlarged
detailed c~oss-section of the nozzle means of
appa~atus shown in Figure 1.
The Figure 3a of the drawings is a detailed
cross-section of a modi ied fo~m of the nozzle
means sho~n in Figure ? in which the lower end
of the nozzle means is tapered inwardly and
showing a de~ailed cross-section of a modified
transverse jet entraining means having a fla~ened
orifice opening.
The Figure 3b of the drawings is a top plane
view of the modified transverse jet entraining
means and the nozzle means illustrated in Figure
3a of the drawings.
The Figure 3c of the drawings illustrates the
use of the apparatus of Figure 3b to make fila-
mented hollow glass microspheres.
DETAILED D I S CUS ~ IO~I
OF THE DRAt~l~GS
Referring to Figures 1 and 2 of the drawings,
there is illustrated a vessel 1, made of suitable
refractory ~aterial and ~eated by means not shown
lS ror holding molten glass 2. The bottom floor 3
of vessel 1 con~ains a pl.urality of openings 4
throu~h ~vhich molten glass 2 is red to coaxial
blowing nozzles S. The coaxial blowing nozzle S
can be made separatel~ or can be formed b~ a
downwida extension of the. bo~tom 3 of vessel 1.
The coa~ial blowing nozzle S consises of an
inner nozzle 6 having an orifice 6a for a gaseous
material blowing gas and/or metal vapor and an
outer nqæzle 7 having an orifice 7a for molten
glass. The inner nozzle 6 is disposed wit~in
and coaxial ~o outer nozzle 7 ~o orm annular
space 8 between nozzles 6 and 7, which annular
space provides a flow path for molten ~lass 2.
The orifice 6a of inner nozzle 6 terminates at
or a short dis~ance above the plane or orifice
- 14 -
_.
,
~ ~ 5~3~ 5 5
7a of outer nozzle 7.
The molten glass 2 at about a~mospheric pressure
or at elevated pressure fl~s downwardly through
annula~ s?ace 8 and fills the area between orifices
6a and 7a. The surface tension forces in molten
glass 2 form a thin liquid mol~en glass rilm 9
across orifices 6a and 7a.
A gaseous material blowing gas lQ, and/o. a
gas concaining a metal vapor, dispersed metal
oarticles or an organo metal comoound which is
at or below ambient temperature or which is heated
by means not shown to about the temperature of
the molten glass and which is at a pressure
above the molten glass oressure at the blowing
nozzle, is fed through distribution conduit 11
and inner coaxial nozzle 6 and brought into
contact with the inner surface of molten glass
film 9. The gaseous material blowing gas e~Prts
a positive pressure on the molten glass film to
blow and distend the film outwardly to for~ an
elongated cylinder shaped liquid film 12 of molten
glass ~illed with the inert blowing gas and/or metal
vapor 10. The elongated cylinder 12 is closed
a~ its outer end and is ccnnected at its inner
end to outer nozzle 7 at the oeripheral edge of
ori~ice 7a. A balancing ~ressure of an inert
~as, i.e. a slightly lower pressure, is pro-
vided in tne area of the blowing nozzle into
which the elongated cylinder shaped liquid
film is blown.
The illus~rated coa~ial noz~le, Figure 2,
can be used to produce microspheres having
diameters three to five times the size of the
inside diameter of orifice 7a and is us2ful
- 15 -
.
~ 5
in blcwing low viscosity glass materials, i.e.
glass compositions at low viscosities.
A transverse jet 13 is used to direct an
; inert entraining fluid 14, which is heated to
about, below or above the temperature of the
molten glass 2, by means not shown. The
.entraining 1uid 14 is fed through distribution
conduit 15, nozzle 13 and transverse jet nozzle
j orifice 13a and directed at the coa~ial blowing
nozzle 5. The transverse jet 13 is aligned to
direc~ ~'ne flow of ent~aining rluid 14 o~er and
around blowing nozzle 7 in the microsphere rorming
region at and behind the orifice 7a. The
entraining fluid 14 as it passes over and around
blowin~ nozzle 5 fluid dynamically induces a
pulsating or fluctuating pressure field in the
entraining fluid 14 at the opposite or lee side
of blowing nozzle 5 in its wake or shadow.
The entraining fluid 14 envelops and acts
on the elongated cylinder 12 in such a manner
as to cause the cylinder to flap, fold, pinch
and close-off at its inner end at a point 16
proximate to the ori~ice 7a of outer nozzle 7.
T~e continued movement or the entraining fluid
14 over .he elongated cylinder 1 produces
fluid drag forces on the cylinder 1~ and
detaches it rrom the orifice 7a of the outer
nozzle 7 to allow the cylinder to fall, i.e.
to be en~rai~ed and transported away frcm
nozzle 7. The surface tension forces o
the molten glass act on the entrained,
ralling elongated cylinder 12 and cause the
cvlinder to seek a minimum surface area and to
form a s~herical shape hollow molten glass
- 16 -
S~55
microsphere 17.
Quench nozzles 18 having oririces 18a
are disposed below and on both sides of coaxial
blowing nozzle 5 and direct cooling fluid 19
at and into contact with the molten glass
microsphere 17 to rapidly cool and solidify
the molten glass and for~ a hard, smooth hollow
glass microsphere. The quench fluid 19 also
serves to carry the hollow glass microsphere
away from the coaxial blowing nozzle 5.
Where a ~etal vapor is used with the blowing
gas, the quench fluid cools and condenses
the metal vapor to deposit the metal vapor
on the inner wall surface of the microsphere
as a transparent o`r ~a reflective metal coating
20. Additional cooling time, ir necessary,
can be provided by using a fluidized bed,
liquid carrier or belt carrier system for the
hollow glass microspheres to harden the micro-
spheres wlth substantiallv little or no dis-
tortion or eff~ct on the size or shape of the
microspheres. The cooled and solidified hollow
glass microspheres are collected by suitable
means not shown.
The Figure 3a o~ the drawings illustrates
a prererred embodiment or ~he invention in
which the lower portion of the outer coaxia
nozzle 7 is ~apered downwardly and inwardly
a~ 21. This embodiment as in the previous
embodiment comprises coa~ial blowing nozzle 5which consists of inner nozzle 6 wich orifice
6a and outer nozzle 7 with orifice 7a'. The
Figure of the drawings also sh~ws elongated
cylinder shaped liquid film 12 with a pinched
- 17 -
portion 16.
The use of the tapered nozzle 21 construction was found to
substantially assist in the formation of a thin molten glass ~ilm 9'
in the area between orifice ~a of inner nozzle 6 and orifice 7a' of
outer nozzle 7. The inner wall surface 22 of the taper portion 21
of the outer nozzle 7 when pressure is applied to molten glass 2
forces the molten glass 2 to squeeze through a fine gap formed he-
tween the outer edge of orlfice 6a, i.e. the outer edge of inner
nozzle 6, and the inner surface 22 to form the thin molten glass
film 9' across orifices 6a and 7a~. Thus, the formation of the
molten film ~' does not in this embodiment rely solely on the sur-
face tension properties of the molten glass.
The illustrated coaxial nozzle can be used to produce
microspheres having diameters three to five times tha size of the
diameter of orifice 7a of coaxial nozzle 7 and allows making micro-
spheres of smaller diameter than those made using in Figure 2
apparatus and is particularly useful in blowing high viscosity glass
materials.
The diameter of the microsphere is determined by the diam-
eter of orifice 7a'. This apparatus allows the use of larger innerdiameters of outer nozzle 7 and larger inner diameters of inner
nozzle 6, both of which reduce the possibility of pluggin~ of the
coaxial nozzles when in use. These features are particularly
advantageous when the blowing gas contains dispersed metal particles
and/or the glass compositions contain additive material particles.
- 18 -
,
`'~,. ~ 3i 5~~55i
In Figures 3a and 3b of the drawings,
the outer portion of the transverse jet
13 is flattened to form a generally rectangular
or oval shaped orifice opening 13a. The orifice
opening 13a can be disposed at an angle .elative
to a line drawn through the central a~is o~
coaxial nozzle 5. The preferred anOle, however,
is that as illustrated in the drawing. That is,
ac an angle of about 90 to the cent~al axis
of the coa~ial nozzle 5.
The use of the flattened transverse jet
entraining fluid was found, at a given velocity,
to concentrate ~he effect or the fluctuating
pressure field and to inc~ease ~he amplitude of
the pressure fluctuations induced in the region
ot ~lle formation of the hollow microspheres a~
the opposite or lee side of the blowing nozzle 5.
By the use of the flattened transverse ~et and
increasing the ampli~ude of the pressurc fluc-
tuations, the pinching action exerted on thecylinder 12 is increased~ This action facili~
tates the closing Off Or the cylinder 12 a~
its inner pinc~ed end 16 and detaching of
the cylinder 13 ~rom ~he ori~ice 7a or the
cen~er nozzle 7.
The F.igure 3c of the drawings illustrates
apparatus in~which a high viscosity glass
material is used to blow hollow glass fila-
men~ed microspheres. In this Figure, the
elon~ated shaped cylinder 12 and glass micro-
spheres 17a, 17b and 17c are connected to each
other bv thin glass filaments 17d. As can be
-- lg --
.
,
5 5
seen in the drawing, as the microspheres 17a,
17b and 17c progress away from blowing nozzle 5
surface tension forces act on the elonOated
cylinder 12 tO effect the gradual change of the
elongated shaped cylinder 12 to the generally
spherical shape 17a, more spherical shape 17b
and finally the spherical shape microsphere
17c. The same surface tension forces cause
a gradual reduction in the diameter of the
connecting filaments 17d, as the distance
between the microspheres and ~ilaments and
the blowing nozzle 5 increases. The hollow
glass microspheres 17a, 17~ and 17c that are
obcained are connected by thin filament por-
tions 17d that are substantially of equallength and that are continuous with theglass microsphere.
The operation oE the apparatus illustrated
in Figures 3a, 3b and 3c is ocherwise
2~ essentially the same as t:hat discussed above
with regard to Figures 1 and 2 of the
drawings.
The apparatus confi~urations illustrated
in the Fi~ures of the dra.wings can be used
singlY or in various com~inations as the
si~uation may require. ~he entire apparatus
can be enclosed in a high pressure containmen~
vessel, not sho~n, which allows ~he process to
be carried out at elevated pressures.
~ 20 -
.
. .
INORGANIC FIL~I FOR~ G 2~'~TERIAL
: AND GL~SS COMPOSITIONS
,, _
- ~ ~ S~3~ 5 5
The inorganic rilm ~orming material and
compositions and particularly the glass compo-
sitions ~rom which the hollow glass microspheresof the present invention are made can be widely
varied to obtain the desired physical charac-
teristics for heating, blowing, forming,
cooling and hardening the microspheres and the
10 desired strength, gas permeability and light
transmissicn characteristics o~ the glass
microspheres produced.
The constituents of the glass compositions
can be selected ar.d blended to have high
resistance to corrosive gaseous materials,
high resistance to gaseous chemical agents,
high resistance to alkali and weather, low
susceptibility to diffusion OL gaseous materials
into and out of the glass microspheres, to be
free o~ trapped gas bubbles or dissolved gases
in the walls of the microspheres which can
form bubbles and to have surficien~ strength
when cooled, hardened and solidified to,
when the microsphere contains a gaseous
material compressed under very high pressure,
withstand ~he contained pressure. The molten
glass composition ~orms hard microspheres wh'ch
are capable or con~acting adjacent microspheres
without significan~ wear or de~erioration at
che poincs of contact and are resistant to
deterioration ~ro~ e.xposure to moisture,
heat and/or weathering.
The constituents of the glass compositions
can var~ widely, depending on the intended
end uses, and can include naturally occurring
and synthetically produced glass materials.
- 21 -
~ (3~ ~ 5
The glass compositions preferably contain
relatively large amounts oE silicon dioxide,
alumina, lithium, zirconia, and lime and
relatively small amounts of soda. Calcium can
j be added to assis~ in melting the glass and
boric oxide can be added to improve the
weathering properties of the glass. The glass
compositions are ~ormulated to have relatively
high melting and rluid flow temperatures with
a relatively na~row temperature difference
bet~een the melting and fluid flow ~empera-
tures. The glass compositions are formulated
such that they have a high rate of viscosity
increase with decreasing temperature so that
the microsphere walls will solidify, harden
and strengthen before the blowing gas within
the sphere decreases in volume and pressure
a su~icient amount to cause the microsphere
to collapse. I~here it is desirous to maintain
a high pressure in the contained vol~e of
the microspheres, the per~eability to gases
such as helium (ambient) requires a reduction
of the ne~worl~ formers, such as silica, and
~he inclusion o~ network modifiers, such
as alumina. Other means for decreasing the
permeability oE the hollow glass microspheres
to gases, for e~ample by the addition of plane-
orientable laminal flow particles, a~e
discussed be`low.
- 22 -
: ~. . - . ,
'
5 5
The glass compositlons suitable for use in
the present invention can have the range of
proportions of the constituen~s listed below
in Col~mns .~, B and C, in percent by weight.
T~BLE 1
A B C
(Alumina) ~ithium) (Zirconia)
SiO2 46-~4 58-85 40-48
~123 10-22 0-25 6-1
Li2O - 8-25. -
Zirconia - - 8-20
CaO 5-18 0-2 1-3
~g~ 0-12 0-2 0-4
B2O3 4-12 2-6 0-6
Na2O 0-1 0-1.0 0-2.5
BaO 0-2.0 0-2.0 0-2.0
~2 0-2.0 0-2.0 0_?,0
~O 0-0.7 0-0.7 ~.5-1.5
: The compositions of Colu~ns A and B do not
. 20 contain zirconia whereas the compositions of
Col~nn C are relatively high in zirconia content.
The Column A glass compositions can be
used for con~aining under high pressure gases
sucn as o~gen, hydrogen, nit~ogen, carbon
25~ monoxide, car~on dioxide, ammonia, acetylene,
methane, and natural gas.
::: `
~ ' ,
- 23 -
:
_ . . . . - -
'
'.
:
'' .
ass
The Column B glass compositions can be
used for containing under high pressure gases
such as helium, hydrogen, deuterium, tri~ium,
argon and neon. These glass compositions are,
S however, particularly useful for containing
inertial confinement fusion fuel target gases
such as deuterium, tritium, and mixtures thereof
inasmuch as the Column B glass ccmpositions are
substantially resistant to diffusion of gases
into and/or out of the glass microspheres and
are or low average atomic number.
The Column C glass compositions can be
used for containing under high pressure gases
such as ~enon, radon, krypton, argon, deuterium
lS and tritium~ These glass compositions are also
particularl~ useful for the storage of atomic
fuel waste gaseous products. The microspheres
made rom the Column C glass compositions can
be stored in concrete or geological storage
~acilities inasmuch as the compositions are
resistant to attack by al~ali.
The use of glass com~positions containing
a relati~ely high alumina content and a rela-
tivel~J low soda content was found to produce
a rapid hardening of the glass microspheres,
which facilitated the production of the glass
microspheres.
The Table 2 below shows in Column I a
high alumina content glass composition of the
present invention and in Column II a high soda
content glass composition heretofore used to
make glass microspheres.
- 24 -
5 5
The glass microspheres made from the Columns
I and II glass composi~ion are made in accordance
with the present invention by blowing the glass
with nitrogen as the blowin~ gas.
TABLE 2
I II
(Alumina) (Soda)
SiO2 57.0 72,2
~123 20.5 1.~
CaO 5.5 8.3
~gO 12 3.3
B203 4
Na~O 1.0 14.2
The Table 3 below compares the increase ir.
viscosity on cooling of the high alumina con~ent
(I) and the hign soda content (II) glass compo-
sitions of Table 2,
TABLE 3
Tem~erature ~iscosity-Poises
20High ~lumina Comp. 2700F.30
(I~ 1830F.lOxL05
1470~.lOx101
High Soda Comp. 2700F.100
(iI) 1830F.lOx103
1~70F.lOx105
.
The Table 3 shows that the high alumina
con~ent glass has a substantially faster hardening
rate than the hi~h soda content glass sucn that
in the first 1300F. or chilling, the high
alumina content ~lass had a viscosity or 10x105
times greater than that of the high soda con-
tent glass.
For certain uses rela~ively low temperature
melting glass compositions can be used. The low
melting glass compositions can contain relatively
large amounts of lead. Naturally occurring
glass materials such as basaltic mineral co~po-
sitions can also be used. The use of ~ese
naturally occurring glass composicions can in
l; some cases substantially reduce che cost o~ the
raw materials used.
Suitable lead containing glass compositions
and basaltic mineral composi.tions are iTI Table 4
TABL,E 4
D E
(I,ead) (Basalt)
SiO2 3~-70 40-55
A12O3 0-2 13-17
2S Pb 10-60
Fe23 ~ 2-16
FeO - 1-12
CaO 0-5 7-14
~gO 0-3 4-12
~a2O 0-9 2-4
K2O 0-9 1 2
H2O - 0.5-4
Ti2 0.~-4
.. . . , . . _ . .. . .
t~See G.L. Sheldon, Forming Fibres from Basalt Rock,
Platinu~ ~etals Review, pages 18 to 34, 1978.
- 26 -
.
. . ..,, . ---- - -- -
5 5
The discussions in the present applica~ion
with respect to glass compositions is applicable
to the various glass compositions mentioned
including the naturally occurring basaltic
mineral compositions.
To assist in the blowing and formation of
the glass microspheres and to control the surface
tension and viscosity of the s~neres suitable
surface active agents, such as colloidal
particles o~ insoluble substances and viscosity
stabilizers can be added to che glass compo-
sitions as additives. These additives can affect
the viscosity o~ the sur.ace film of the micro-
sphere to stabilize the film during the micro-
sphere formation.
A distinct and advantageous ~eature of thepresent invention is that latent solid or
latent liquid blowing gases are not used or
required and that ~he microspheres that are
produced are free o latenc solid or latent
liquid blowing gas materials or gases.
The glass compositions from which the
hollow glass microspheres can be made are,
dependin~ on the particular glass materi.als
used, to some degree permeable to the gas
materials used to blow the microspheres and/or
to t~e gases present in the medium surrounding
the microspheres. The gas permeability of
the gl2ss compositions can be controlled,
modified and/or reduced or substantially
s
eliminated by the addition, prior to blowing
the microspheres, to the glass composition of
very small inert laminal plane-orientable
additive material particles. Suitable
S additive particles are copper, gold and
aluminum leaf powders. When any one or more
of these laminal plane-orientable additive
material particles are added to a glass compo-
sition prior to the blowing and formation of
the hollow glass microsphere, the process
of making the microsphere aligns the laminal
particles, as the glass film is stretched
in passing, i.e. extruded, through the conical
blowing nozzle, with the walls of the hollow
glass microsphere and normal to the gas
difusion direction. The presence of the
laminal plane particles in the microsphere
walls substantially diminishes the gas
permeability of the glass film. The sizes
of the additive particles are advantageously
selected to be less than one-half the thick-
ness of the wall of the microspheres.
BLOWING GASES
The hollow microspheres, particularl~ the
hollow glass microspheres can be blown with the
desired blowing gas or with a gas containing
a metal vapor, dispersed metal particles or an
organo metal compound or mixtures thereof.
The desired gaseous material blowing
gases are those for which ease in handling and
storage are sought.
- 28 -
q~5S
The process and apparatus described above
can be used to compress a wide
variety o~ gaseous materials in hollow glass
microspheres ~.~hich greatly facilitate the
handling, processing, use, storage and dis-
posal of the gaseous materials.
Examples of such gaseous materials
are reusable gases such as oxygen,
hydrogen, nitrogen, carbon monoxide, carbon
dio~ide, air, helium, ammonia, neon, and
acetylene.
The gases can readily be released from
the microspheres merely by feeding the micro-
sphere in an enclosed container be~ween twocounter rotating small steel drums. Where
the contained gas is used as a ~uel, the
microspheres can be ~ed directly into the
combustion region. The surface of the drums
can be slightly roughened so as to grasp and
crush the microspheres ancl release the con-
tained pressurized gases.
The microspheres can also be used to
uniformlv mix t~.~o chemical reactant gases,
separatel~f contained in m:icros~heres, or
a chemically reactant g2S and a liquid prior
to initiacing che chemical reaction.
The hollow glass microspheres may
contain under pressure poisonous, toxic,
3~ corroslve and radioactive waste gaseous
materials. Because the gaseous materials can
be compressed under high pressure in the
contained volume of the microspheres,
- 2~ -
a~s~ss
relatively large volumes of ~he gaseous materials
can be contained in relatively small microspheres.
The present invention avoids the use and need
for heavy metal containers, complex valving
systems and corrosion resistant alloys. The
present invention finds particular and advan-
tageous use in the handling and storage of
poisonous gaseous materials such as hydrogen,
cyanide, chlorine, bromine, and carbon monoxide
gases and of radioactive waste gaseous materials
such as radon, tritium, krypton and xenon.
The use o~ the microspheres to contain
the gaseous materials renders the toxic,
corrosive and radioactive waste gaseous
materials relatively safe and easy to
handle. These materials can be safely stored,
as appropriate, in steel or lead containers,
geological formations or mixed with and
stored in concre~,e.
The hollow ~lass microspheres may
contain under pressure gaseous laser ~uel
materials such as tritium, deuterium, and
mixtures thereof. The invention has particular
utilicy in the manufacture of inertial
confinement fuel targets for hydrogen fusion
research and reactors.
- 30 -
.
3~ 5 5
The metal vapor when used in combination
with the blowing ~as can deposit a metal
coating on the inner wall surface of the
hollow glass microsphere. The thickness of
and nature of the metal coating deposited
will determine whether the metal coatin~
is transparent or reflective of visible light.
The metal vapor when used with the
blowing gas to blow the hollow glass micro-
spheres is selected to have the desired
vaporization cemperature, latent heat capaci~y
and vapor pressure at the blowing temperature,
and to have the desired vapor pressure at the
solidification temperature and ambient tem-
perature. The condensing and depositing of
the metal vapor within the hollow glass
microsphere ?roduces a vapor pressure af
the metal vapor equivalent to the vapor
pressure of the metal at room temperature,
i.e. abou~ zero vapor pressure. The overall
pressure contained within the microsphere
will be that o the blowing gas (after
cooling), e.g. lO0 to 1000 p.s.i.g. The
thickness of the deposited metal coating
will de?end ~o some e~tent upon ~he metal
vapor partial pressure in the gas used ~o
blow ~he microsphere, the si~é or the micro-
sphere and the temperature of the molten
glass.
The metal vapors of metals such as
zinc, antimony, barium, cadmium, bismuth,
selenium, li~hium, magnesium, and potassium
can be used. Zinc and selenium, however,
are preferred.
- 31 -
~ 5 5
A blowing gas containing dispersed
metal ?articles can be used to obtain in
the contained volume of the microsphere
a deposit of a thir. metal coating on the
inner wall surface of the hollow glass
microsphere. The metal used to coat the
inner wall surface of the hollow glass
microspheres is selected to have the
desired cr.aracteristics, and to adhere
to the inner wall surface of the glass
microspheres. The thickness or. the
deposited metal coacing will depend to
some e.~ten~ upon the met~l, the par~icle
size of the metal used, the size of the
microspheres and the amount of dispersed
metal particles used.
- 32 -
}
~ `3~ S 5
The dispersed metal particle size can be
25A to lO,OOOA, preferably 50A to 5,000A and
O O
more preferably lOOA to 1, OOOA. A sufficient
amount of the metal is dispersed -in the blowing
gas to obtain the desired thickness of the
deposited metal. The dispersed metal particles
can advantageously be provided with an electro-
static charge tO assist in deposi~ing ~hem on
- the inner wall surface of the microspheres.
~letal particles such as aluminum, silver,
nic~el, zinc, antimony, bariu~, cadmium,
cesium, bismuth, selenium, lithium, magnesium,
potassium, and gold can be used. Aluminum,
zinc and nickel, however, are preferred.
~ispersed metal oxide particles can in a
similar manner be used to obtain si~ilar
effects to that of the metals.
The thin metal coating can also be
deposited on the inner ~all surrace of the
microsphere by using as or with blowing gas
organo me.al compounds th,at are gases at the
blowing temperatures. ~f the organo metal
compounds available, the organo car~onyl
compounds are ?reerred. Suitable organo
~5 metal ca-bonyl compounds are nickel and iron.
The organo metal compounds can be
decomposed by heating just prior to blowing
the microspheres ~.o ob~ain finely dispersed
metal particles and a decG~position product, e.g. a gas.
The decomposition gas, if present, can be
used to assist in blowing ~he microspheres.
The dispersed metal particles from decompo-
sition or the organo metal compound, as
before, deposit to form the thin metal
3~ layer. .~lternatively, the microsphere,
- 33
r
after being ~ormed and containing the gaseous
organo metal compound blowing gas, can be
subjec~ed to an "elec~ric discharge" means
which decomposes the organo metal compound
to fo~m the finely dispersed me~al par~icles
and the decomposition product.
The thickness of the deposited metal
layer will depend prlmarily on the par~ial
press~re of the gasecus organo metal blowing
gas and the inside diame~er of the micro-
sphere.
In each of the above discussed embodimen~s,
the specific me~al ~sed 2S well as the
thickness and nature of metal coating
deposited will determine ~hether the
metal coating is transparent or reflective
of visible light.
Blowing gases can also be selec~ed that
react r.~ith the inorganic ~ilm forming material
or composition, e.g. the glass microspheres,
for e~ample, to assist in the hardening of
the microspheres or to make the microsphere
less per~eable to the contained blowing gases.
The blowing gases can also be selected to
react with the deposited ~hin metal layer.
A second blowing gas can advantageously
be used in combination with the principle
blowing gas to assist in the control of the
cooling and`solidification of the hollow
molten glass mlcrosphere, to react with
the principle gas and/or to stabilize or
initiate chemical degradation to a less
to~ic or less poi.sonous ror~ such that the
gaseous materials by passage of time become
- 34 -
5 ~
less hazardous. The auxiliary blowing gas
can assist in the control of the cooling
and solidification of the microspheres by
maintaining the partial pressure of the
auxiliary blowing gas in the microsphere
for a sufficient period o time to allow
the molten glass microsphere to solidify,
harden and strengthen while the microsphere
is cooled and hardened.
The entraining fluid can be a gas at a
high or low temperature and can be selected
to react with or be inert to the glass compo-
sition. The entraining fluid, e.g. an inert
entraining fluid, can be a high temperature
gas. Suitable entraining fluids are
nitrogen, air, steam, argon and xenon.
The gas in the area surroun~ing the
blowing nozzle can be any suitable inert gas
such as those that can be used as the
entraining fluid, e.g. nitrogen, air, argon,
and xenon.
An important feature of the present
invention is the use of the transverse jet
to direct the inert entraining fluid over
and around the coaxial blowing nozzle. The
entraining fluid assists in the formation and
detaching of ~he hollow molten glass miero-
sphere Crom the coaxial blowing nozzle.
- 35 -
The quench fluid can be a liquid, a liquid
dispersion or a gas. Suitable quench fluids
are ethylene glycol vapor or liquid, steam,
a fine water spray, air, nitrogen or mixtures
thereof. The hollow molten glass microspheres
immediately after they are formed are rapidly
quenched and cooled to solidify, harden and
strengthen the glass microspheres before
the internal gas pressure is reduced to such
a low value that the microsphere coilapses.
The selection of a speciric quench fluid
and quench temperature depends to some
extent on the glass composition ~rom which
the microsphere was formed and on the
blowing gas or metal vapor used to blo~
the microsphere and on the metal and
nature or the deposited mecal ~ilm desired.
PROCESS ONDITIONS
The inorganic film forming materials and/or composi-
tions from which the microspheres are formed are inliquid form at the desired blowing temperature
and during the blo~ing operation. The inorganic
film forming materials and/or compositions
are heated to a temperature of about 1800 to
3100F. and maintained in a liquid, fluid
rorm during ~he blowing operation. The glass
compositions are ~eated to a ~emperature of
20Q0 to 280bF., preferably 2300 to 2750F.
; and more prererablv 2400 to 2700F., depending
on the constituen~s of the composition. The
lead containing glass compositions can be
neated to a tempera~ure of, for example,
about 1~00 to 2900 F~ The basaltic mineral
glass composi~ions can be heated to a tem-
perature of, for example, about 2100 ~o
-- 36 --
._r
3C~553100F,
The glass compositions ac these tempera-
~ures, i.e. the blowing temperatures, is ~olten,
fluid and flows easily. The molten glass just
prior to the blowing operation has a viscosity
of lO to 600 poises, prererably 20 to 350
and more preferablY 30 to 200 poises. The
molcen lead containing glass compositions
just prior to the blowing operation have a
viscosity or, for example, 10 to 500 poises.
The molten basaltic mineral glass composition
just prior to the blowing operation can have
a viscosity of, ror example, 15 tO 400 poises.
~ere the ?rocess is used to make non-filamented
lS microspheres, the liquid glass just prior
to the blowing operation can have a viscosity
of 10 to 200 poises, preferably ?0 to 100
poises, and more preferably 25 ~o 75 poises.
I~here the process is used to make fila-
mented microspheres, the liquid glass justprior to the blowing operation can have a
viscositv of 50 to 600 poises, pre~erably
100 to 400 poises, and mor.e preferably 150
~o 300 poises.
~S A critical feature of the process
is that the formation of the hollow
microspheres can be carried out at low
viscosities relative to the viscosities
heretorore used in the prior art processes
~0 that utili~ed latent.liquid or solid blowing
agents dispersed throughout or contained
in the glass compositions used to blcw the
microspheres. Because or the abilicy to
utilize comparatively low viscosities,
applicanc is able to obtain hollow glass
- 37 -
microspheres, the walls of which are free of
any entrapped or dissolved gases or bubbles.
With the low viscosities used by applicant,
any entrapped or dissolved gases di~fuse out
and escape from the glass film surface during
the bubble formation. With the high vis-
cosities required to be used in the prior
are processes, any dissolved gases or bubbles are
trapped in the walls of the glass micro-
spheres as they are formed because of the
high viscosities required to be used.
The glass during the blowing operacion
exhibits a surface tension of 150 to 400
dynes/cm, preferably 200 to 350 dynes/cm
and ~ore ?referably 250 to 325 dynes/cm.
The molten glass fed to the coaxial
blowing nozzle can be at ambient pressure
or can be at an eleva~ed pressure. The
molten or liquid glass feed can be at a
pressure of l to 20,000 p.s.i.g., usuall~
3 to 10,~00 p.s.i.g. and rnore usually 5 to
5,000 p.s.i.g. Where the process is used
to encapsulate gases a~ elevated pressures,
the molten glass can be at: a pressure of
1 to 15,000 p.s.i.g., preferably lO0 to
6,000 p.s.i.g. and more prererably 500
to 3,000 p.s.i.g. The molten glass is
continuously fed to the coaxial blowing
nozzle durin~ the blowing operation to pre-
ven~ premature breaking and detaching of the
elongated cylinder shaped molten glass liquid
film 2S i~ iS being formed by the blowing gas.
- 38 ~
~ 5 5
The blowing gas, gaseous material blowing
gas and me~al vapor, dispersed ~etal particles
or organo metal compound can be at about the
same temperature as the molten glass being blo~n.
The gaseous material blowing gas tempera~ure
can, however, be at a higher temperature than
the molten glass to assist in maintaining
the fluidity of ~he hollow molten glass micro--
sphere during the blowing operation or can
be at a lower temperature than the molten
glass to assis. in the solidi~ication and
hardening of the hollow molten glass micro-
sphere as it iS formed.
The pressure of ~he gaseous material
lS blowing gas or gaseous material blowing
gas including metal vapor, dispersed metal
particles or organo metal compounds is
suf~icient to blow the m:icrosphere and will
be slightly above the pressure of molten glass
at the orifice 7a o the outer nozzle 7.
The gaseous material blowing gas can be a~ a
pressure of 1 ~o ~0,000 p.s.i.g., usually
3 to 10,000 p.s.i.g. and more usually S to
5,000 p.s.i.g. The gaseous material when
used to encapsulate gases at elevated pressures
can also be at a pressure of 1 to 15,000
p.s.i.g., preferably 100 to 6,000 p.s.i.g.
and more preferably 500 to 3,000 p.s.i.g.
Depending on the particular gaseous material
blowing gas used, the blowing gas or
gaseous material blowing gas can be at a
pressure of 50 to 20,000 p.s.i.g.,
prererabl~J more than 100, e.g. 200 to
lO,OOO p~s.i.g. and more preferably
S00 to 5,000 p.s.i.g. The blowing gas
- 39 -
-
3S~
pressure will also depend on and be slightly
above the ambient pressure external to
the blowing nozzle.
The pressure of the gaseous material
blowing gas is sufficient to blow the micro-
sphere and will be slightly above the pres-
sure of the liauid glass at the orifice 7a
of the outer nozzle 7.
The temperature of the gaseous
material blowin~ gas will o~ course also
depend on what che macerial is and its
chemical decomposi~ion temperature and
will be below its decomposition temperature.
The blowing gas temperacure will also
depend on the viscosity-temperature-shear
relationship of the glass materials used
to make the microspheres. The temperature
is obviously not a problem with gaseous
materials which are themselves one o~
the basic elements.
- 40 -
-
. .
The metal vapor blowing gas temperature
will be sl-fficient to vaporize the metal and
will be a~ about the same temperature as the
molten glass being blo~n. The me~al vapor
blowing gas temperature can. however, be at
a higher temperature than the molten glass to
assist in maintaining the fluidity of the
hollow molten glass microsphere during the
blowing operation or can be at a lower tem- -
perature than the molten glass to assist in
the solidification and hardening or the hollow
molten glass microsphere as it is formed.
The pressure of the metal vapor blowing gas
is suff cient in combination with the
principle blowing gas to blow the micro-
sphere and will be slightly above the pres-
sure of molten glass at the orifice 7a of the
outer nozzle 7. The pressure of the combined
mixture of the blowing gases will also
depend on and be slightly above the ambient
pressure e:cternal to the blowing nozzle.
The ambient pressu~e external to the
blowing nozzle can be at about atmospheric
pressure or can be at super-atmospheric
pressure. I~ere it is desired to ha~e a
; relatively or high pressure of contained gas
in the microsphere or to deposit a relatively
thick coating o~ metal within a ~icrosphere,
t~e ambient pressure external to the blowing
nozzle is maintained at a super-atmospheric
pressure. The ambient pressure externai to
the blowing noæzle will be such that it sub-
stantially balances (i.e. is about equal to),
but is slightly less than the blowing gas pressure.
Thus, the ambient gas pressure external to the
blowing
~ 3S 5
nozzle will be about but slightly less than
1 to 15,000 p.s.i.g., preferably 100 to
6,000 p.s.i.g. and more preferably 500 to
3,000 p.s.i.g. The ambient pressure can
also be about but slightly less than 50 to
20,000 p.s.i.g., preferably 100, e.g. 200,
to 10,000 p.s.i.g. and more pre~erably
S00 to 5,0~ p.s.i.g.
The transverse jet inert entraining
fluid ~hich is directed over and around the
coa~ial blowing nozzle to assist in the
for~ation and detaching of the hollow molten
glass microsphere from the coaxial blowing
nozzle can be at about the temperature of
the molten glass being blown. The entraining
fluid can, however, be at a higher temperature
than the molcen glass to assist in maintaining
the fluidity of the hollow molten glass
microspnere during the blowing operation or
can be at a lower temperature than the
molten glass to assist in the stabilization
of the forming film and the solidification
and hardening of the hollo~ mol~en glass
microsphere as it is formed.
~5 The transverse jet entraining fluid
can have a linear velocity in the region
o microsphere formation of 1 to 120
ft/sec, usually 5 to 80 ft/sec and more
usually 10 to oO ft/sec.
- 42 -
1.~ 5~
Where the process if used to make non-
filamented microspheres, the linear velocity
of the transverse jet fluid in the region of
microsphere formation can be 30 to 120 ft/sec,
preferably 40 to lO0 ft/sec and more preferably
50 to 80 ft/sec.
Ilhere the process is used to make fila-
mented microspheres, the linear velocity of
the transverse jet fluid in the region of
microsphere ror~ation can be 1 to 50 ft/sec,
preferably S to 40 ft/sec and more preferably
10 to 30 ft/see.
Further, it is found (Figures 2.to 4) that
pulsing che transverse jet entraining fluid
at a rate of 2 to 1500 pulses/sec, preferably
50 to 1~00 pulses/sec and more preferably
lO0 to 500 pulses/sec assists in controlling
the diameter or the microsphe~es and the
length of the filament portion of the ila-
mented microspheres and detaching the micro-
spheres from the coaxial blowing nozzle.
The distance between filamented micro-
spheres depends to some extent on che vis-
cosity of the glass and che linear velocity
or the transverse je~ entraining fluid.
- 43 -
._
3'~ 5
The quench fluid is at a ~emperature such
that it rapidly cools the hollow molten glass
microsphere to solidify, harden and strengthen
the molten glass before the inner gas pressure
or metal vapor pressure decreases to a value
at which the glass microsphere would colla?se.
The quench fluid can be at a temperature of
O tO 500F., preferably 40 to 200F. and
more preferably 50 to 100F., depending to
some exten~ on the glass composition.
The quench fluid very rapidly cools the
outer molten glass surface of the microsphere
with which it is in direct contact and
more slowly cools the blowing gas or metal
vapor enclosed within the microsphere
because of the lower thermal conductivity
o~ the gas or vapor. This cooling process
allows sufficient time ~or the glass walls
~0 of the microspheres to st:reng~hen before
t~e gas is cooled and/or ~he me~al vapor is
cooled and the pressure w:ithin the glass
mi~rosphere is substantia:lly reduced.
The time elapsed frorn commencemenc of
the blowing of the glass microspheres to the
coolin~ and hardening or ~he microspheres
can be .0001 to 1.0 second, preferably .0010
to 0.50 second and more preferably 0.010
to 0.10 second.
The rilamented microsphere embodiment
of the invention provides a ~.eans by which
the microspheres ~ay be suspended and allowed
to harden and strengthen without being
brought into contact wi th any surface.
- 44 -
,~.,. _
The filamen~ed microspheres are simply drawn on
a blanket or dru~ and are suspended between the
biowing nozzle and the blanket or drurn for a
suficient period of time for them to harden
and strengthen.
APPA~TUS
Referring to ~igures 1 and 2 of the drawings,
the reractory vessel 1 is constructed to main-
tain the molten glass at the desired operating
~emperatures. The molten glass 2 is ed to
coaxial blowing nozzle 5. The coa~ial blowing
nozzle 5 consists of an inner nozzle 6 having
an outside diameter of 0.32 to 0.010 inch,
preferably 0.20 to 0.015 inch and ~ore preferably
0.10 to 0.020 inch and an outer nozzle 7 having
an inside diameter of 0.420 to 0.020 inch,
preferably 0.260 to 0.025 and more preferablv
0.130 to 0.030 inch. The inner nozzle 6 and
outer no7zle 7 form annular space 8 which
provides a flow path through which the molten
glass 2 is extruded. The distance between
the inner nozzle 6 and out:er nozzle 7 can be
0.050 to 0.004, preferably 0.030 to 0.005
and more preLer~bly O.Q15 to 0.008 inch.
The orifice 6a of inner nozzle k
terminates a short distance above the plane
of oriice 7a of outer nozzle 7. The
oriice 6a can be spaced above orifice 7a
at a distance of 0.001 to 0.125 inch,
preferably 0.902 to 0.050 inch and more
preferably 0.003 to 0.025 inch. The mol~en
glass 2 flows downwardly through annular
space 8 and fills the area between orifices
6a and 7a. The orifices 6a and 7a can
- 45 -
~ ~ .
be made from stainless steel, platinum alloys, or fused alumina.
The surface tension forces in the molten glass 2 form a thin liquid
molten glass film 9 across orifices 6a and 7a which has about the
same or a smaller thickness as the distance of orifice 6a is spaced
above orifice 7a. The molten glass film 9 can be 25 to 3175 microns,
preferably 50 to 1270 microns and more preferably 76 to 635 microns
thick.
A gaseous material blowing gas is fed through inner coaxial
nozzle 6 and brought into contact with the inner surface of molten
glass film 9. The blowing gas and/or metal vapor exerts a positive
pressure on the molten glass film to blow and distend the film
outwardly and downwardly to form an elongated cylinder shaped liquid
film 12 of molten glass filled with the blowing gas l~. The
elongated cylinder 12 is closed at its outer end and is connected
to outer nozzle 7 at the peripheral edge of orifice 7a.
The Figure 2 blowing nozzl~e can be used to blow molten
glass at relatlvely low viscosities, for example, of 10 to 60 poises,
and to blow hollow glass microspheres of relatively thick wallsize,
for example, of 20 to 100 microns or more.
The transverse jet 13 is used to direct an inert entraining
fluid 14 through nozzle 13 and transverse jet nozzle orifice 13a at
the coaxial blowing nozzle S. The
- 46 -
.
5 S
coaxial blowing nozzle 5 has an outer
diameter of 0.52 to 0.030 inch, prererablv
0.36 to 0.035 inch and more preferablv 0.140
tO 0. 040 inch.
~he process was
found to be very sensitive to the distance of
the transverse jet 13 from the orifice 7a
of outer nozzle 7, the angle at which the
transverse jet was directed at coaxial blowing
nozzle 5 and the point at which a line drawn
through the center a~is of transverse jet 13
intersects with a line drawn through the
center axis of coaxial nozzle 5. The trans-
verse jet 13 is aligned to direct the flow
of entraining fluid 14 over and around outer
nozzle 7 in the microsphere forming region
of the orifice 7a. The orifice 13a of trans-
verse jee 13 is located a distance of 0.5
to 14 times, prererably 1 to 10 times and
more preferably 1.5 to 8 t:imes and still
more preferably 1.5 to 4 times the outside
diameter of coaYial blowing nozzle S away
from the point of intersect of a line
drawn along the center a.Yis of transverse
jet 13 and a line drawn a1ong t~e center
aYis of coaxial blowing nozzle j. The
center a~is of transverse jet 13 is aligned
at an angle of 15 to 85, preferably 25
to /5 and more preferably 35 to 55 relative
to the center a~Yis of the coaYial blowing
nozzle 5. The orilice 13a can be circular
: in shape and have an inside diameter of
` 0.32 to 0.010 inch, preferably 0.20 to
0.015 inch and more prererably 0.10 to
0.020 inch.
- 47 -
~ 3~ S 5
The line drawn through the center axis
of transverse jet 13 intersects the line drawn
through the center axis of coaxial blowing
nozzle 5 at a point above the orifice 7a of
S outer nozzle 7 which is.S to 4 times, pre-
ferably 1.~ to 3.5 times and more preferably
2 eo 3 times the outside diameter of the
coaxial blowing nozzle 5. The transverse
jet entraining fluid acts on the elongated
shaped cylinder 12 to flap and pinch it
closed and to detach it form the orifice 7a
of the outer nozzle 7 to allow the cylinder
to fall free, i.e. be transported away
from the outer nozzle 7 by the entraining `
fluid.
The transverse jet entraining fluid as
it passes over and around the blowing nozzle
fluid dynamically induces a periodic pul-
sating or fluctuating pressure field at
the opposite or lee side of the blowing
nozzle in the wake or shadow of the coa~ial
blowing nozzle. A similar periodic pul-
sating or ~luctuating pressure field can
be produced by a pulsating sonic pressure
field directed at the coaxial blowing nozzle.
; T'ne entraining fluid assists in the formation
and detaching of-the hollow glass micro-
sph.ere from the coaxial blowing nozzle.
The use of the transverse jet and entraining
fluid in ~he manner described also dis-
courages wetting of the outer wall surface
of the coa~ial blowing nozzle 5 by the
molten glass being blown. The wetting of
the outer wall can otherwise disrupt and
interfer with blowing the microsphere.
- 48 -
..
.. , , ~ . .. .... .. . . .
,
, ~
5 5
The quench nozzles 18 are disposed below
and on both sides of coaxial blowing nozzle 5
a sufficient distance apar~ to allow che
microspheres 17 to fall between the quench
nozzles 18. The inside diameter of quench
nozzle orifice 18a can be 0.1 to 0.75 inch,
preferably 0.2 to 0.6 inch and more preferably
0.3 to 0.5 inch. The quench nozzles 18 direct
cooling fluid 19 at and into contact with
the molten glass microspheres 17 at a velocity
of 2 to 14, preferably 3 to 10 and more
preferably 4 to 8 ft/sec to rapidly cool
and solidify the molten glass and form a
hard, smooth hollow glass microsphere.
Referring to Figure 3a, it
is fcund ~hat in blowing high viscosity
molten glass co~positions, i.e. molten
glass compositions at high viscosities,
that it was advantageous to immediately
prior to blowing the molten glass to provide
by extrusion a very thin molten glass liquid
film for blowinO into the elonga~ed cylinder
shape liquid ~ilm 12. Thle thin molten
glass li.quid film 9' is provided by having
~he lower portion o~ the outer coa~ial
nozzle 7 tapered downwardly and inwardly
at 21. The tapered portion 21 and inner
wall surface~22 ~hereo can be at an angle
of 15 to 75, preferably 30 to 60 and more
prererably about 45 relative to the
center axis of coaxial blowing nozzle 5.
The orifice 7a' can be 0.10 to 1.5 times,
preferably 0.20 to 1.1 times and more
. - 49 -
3~ ~ 5
pre~erabl~ 0.25 to .8 times the inner diameter
of orifice 6a of inner nozzle 6.
The thickness o~ the molten glass liquid
film 9' can be varied by adjusting the
distance of orifice 6a of inner nozzle 6
above orifice 7a of outer no7zle 7 such that
the distance between the peripheral edge of
orifice 6a and the inner wall sur.ace 22 of
tapered nozzle 21 can be varied. By controlling
the distance between the peripheral edge of
orifice 6a and ~he inner wall surface 22 of
the tapered nozzle to form a very fine gap
and by controlling the pressure applied ~o
feed che ~olten glass 2 through annular
space 8 the ~olten glass 2 can be squeezed
and e~truded through the very fine gap to
form a relatively thin molten glass liq~id
film 9'.
The proper ga? can best be determined ~y
pressing the inner coaxial nozzle 6 downward
with sur~icient pressure to complecely
block-of the flow of glass, and co then
very slowly raise the inner coaxial nozzle
6 until a scable system is obtained, i.e.
until the microspheres are being formed.
The ~apered nozzle construction
illustrated in Figure 3a can be used to blow
glass compositions at relatively high viscosities
as well as to blow glass compositions at the
relatively low viscosities referred to with
regard to Figure 2 of the drawings. The ~igure 3a
construction is of particular advantage
- 50 -
in blowing the thin walled microspheres.
~ hen blowing high viscosity glass compo-
sitions, it was ~ound to be advantageous to
obtain the very thin molten glass fluid film
and ~o continue during the blcwing operation
to supply molten glass to the elongated
cylinder shapea liquid film as i~ was formed.
r~here a high pressure is used to squeeze,
i.e. extrude, the molten glass through the
very thin gap, the pressure of the blcwing g~
and/or blowing gas and ~etal va~or is generall-~ less
than the molten glass feed pressure, but
slightly above the pressure of the molten
glass at the coa~ial blowing nozzle.
The tapered nozzle configuration of
Figure 3a is also particularly useful in
aligning the laminal plane-orientable glass
additive materials. The passage o~ the
glass material through the fine or narrow
gap serves to align the additive ~aterials
with the walls o~ the microspheres as the
microspheres are being formed.
The Figures 3a and 3b o~ the drawings
also illustrate preferred configurations
in which the transverse jet
13 is flattened to form a generally
rectangular or oval shape. The orifice
13a can also be flattened to form a
generally oval or rectangular shape. The
width o the orifice can be 0.96 to 0.030
inch, preferably 0~0 to 0.045 inch and
more preerably 0.30 to 0.060 inch. The
height o~ the orifice can be 0.32 to 0.010
inch, preferably 0.~0 to 0.015 inch and
more preferably 0.10 to 0.0~0 inch.
. .
The Fi~ure 3c of the drawings illustra~es
a conEiguration in
which a glass material or composition a~ high
viscosity is used to blow filamented hollow
glass microspheres. The drawing shows the
formation of the uniform diame~er micro-
spheres space~ about equal distances apart.
The numbered items in this àrawing have
~he same meanings as discussed above with
reference to Figures 1, 2, 3a and 3b.
DESCRIPTION OF THE ~IICROSPHER~S
.. ..
The hollow microspheres made in accordance
with the present invention can be made from
a wide variety of inorganic film forming
materials and compositions, ~articularly
glass compositions.
The hollow microspheres made in accordance
with the present invention can be made from
suitable inorganic film forming composi~ions.
The compositions are preferably resistant
to high temperatures and chemical at~ack,
resistant to corrosi~e and alkali and
resistant to weathering as the situation may
require,
The inorganic film forming compositions
that can be used are those that have the
necessary viscosi~ies, as mentioned above,
when being blown to ~orm stable films and
which have a rapid change from the molten
or liquid state to the solid or hard state
with a relatively narrow temperature change.
That is, thev change from liquid to solid
within a relatively narrowly defined tempera-
ture range.
- 52 -
.
~ 3~ ~ 5
. ~
The hollow glass microspheres made in
accordance with the present invention are
preerably made from glass compositions.
The glass microspheres are substantially
uniform in diameter and wall thickness, and
have a clear, hard, smooth surface. The
walls o~ the microspheres are free of any holes
and substantially free of any relativel~
thinned wall portions or sections, sealing
tips, trappea gas bubbles or sufficient
amounts of dissolved gases to form bubbles.
The microspheres are also rree of any latent
solid or liquid blowing gas materials or
gases. The preferred glass compositions
are those that are resistant to al~ali,
chemical attack, high temperatures,
~eathering and diffusion of gases into
and/or out of the microspheres. Where the
gases to be encapsulated may decompose
at elevated temperatures, glass compo-
sitions that are molten below ~he decompo-
sition temperatures of the gases can be
used.
The microspheres after being formed
can be reheated to soften the glass and
enlarge the microspheres and/or to improve
the sur~ace smoothness of the microspheres.
On reheating, the internal gas pressure
will increase and cause the microsphere
to increase in size. After reheating to
the desired size, for example, in a
"shot tower", the microspheres are rapidly
cooled to retain the increase in size.
- 53 -
;t~5i5
The glass microspheres can be made in various diameters and
wall thickness, dependlng upon the desired end use of the micro-
spheres. The microspheres can have an outer diameter of 200 to
10,000 microns, preferably 500 to 6,000 microns, e.g, 500 to 2,000
microns, and more preferably 1,000 to 4,000 microns. The micro-
spheres can have a wall thickness of 0.1 to 1,000 microns, prefer-
ably 0.5 to 400 microns, e.g. 10 to 100 microns, and more prefer-
ably 1 to 100 microns. Where a particular use or need requires it,
the microspheres can also be made to have a wall thickness o~ 10 to
1,000 microns, preferably 20 to 400 microns and more preferably 50
to 100 microns.
The microspheres, because the walls are free of any holes
and substantially free of any thinned wall sections, trapped gas
bubbles, ancl/or sufficient amounts of dissolved gases to form trap-
ped bubbles, are substantially stronger than those heretofore pro-
duced. The absence of a sealing tip also makes the microspheres
stronger.
The high pressure gas containing microspheres a~ter cooling
to ambient temperatures can contain a gaseous material at about
ambient pressure or at superatmospheric pressure in the enclosed
volume. The microspheres can have a contained gas pressure of about
5 to 8,000 p.s.i.g., usually 15 to 1,600 or 2,000 p.s.i.g. and more
usually 90 to 1,000 p.s.i.g. The contained gaseous
- 54 -
5S
materials can also be at pressures of l to
2,000 p.s.i.g., and 100 to 1800 p.s.i.g.
The contained gas pressures are preferably
at 800 to 1200 p.s.i.g., depending on the
contained gaseous materials. Depending on
the glass composition, diameter and wall
thickness of the microspheres, the micro-
spheres can contain gases under pressures
of up to and/or greater than 3,00C to
5,000 p.s.i.g.
The microspheres can contain a metal
coating on the inner wall surface of the
hollow microspheres when a metal vapor,
dispersed metal paxticles and/or an organo
metal compound is mixed with the gaseous
material blowing gas.
The thickness of the metal vapor
coating deposited on the inner wall
sur~ace of the microsphere will depend
on the metal vapor used to blow the micro-
sphere, the pressure of t:he metal vapor
and the size o~ the microsphere. The
thickness o~ the ~etal coating can be 25
to lO,000~, prererablv 50 to S,OOOA and
more preferably 100 to l,000~. The thickness
o the metal coating can also be 25 to 1, OOOA,
preferably 50 to 600A and more preferably
100 to 400A.
The microspheres can also contain a thin
metal layer deposited on the inner wall
surface of the microsphere where the blowing
gas CQntainS dispersed metal particles or an
~ organo metal compound. The thickness of the
; thin metal coating deposited on the inner wall
- 55 -
... . ~ , :
` ~ '
;5
sur~ace of the microsphere will depend on the
amount and particle size o~ the dispersed
metal particles or partial pressure of organo
metal blowing gas tha~ are used and the
diameter o~ the microsphere. The thickness
of the thin metal coating can be 25 to
lO,OOOA, preferably 50 to 5,000A and more
preferably 100 to l,OOOA.
~lhen it is desired that the deposited
metal coating be transparent, the coating
can ~e less than lOOA and preferably less
than SOA. The transparent metal coated
microspheres can have a deposited metal
coating 25 to 95A and preferably 50 to
80A thick. The microspheres, though
transparent to visible light, are sub-
stantially reflective of in~rared
radiation.
I~hen it is desired that the ~eposited
metal coating be reflective, the coating
can be more than 100A and preferably more
than 150A thick. The ref:Lective metal
coated microspheres can have a deposited
metal coating 105 to 600A and pre~erably
150 to 400A thick and more preferably
150 to 250A thick.
The microspheres can be fonmed in
. ~
a manner such that they are connected by
continuous thin glass filaments, that
is they are made in the rorm of filamented
microspheres. The length of the connecting
filaments can be 1 to 40, usually 2 to 20
and more usuallv 3 to 15 times the diame~er
of the microspheres. The diameter, that
; 35 is the thickness o~ the connecting filaments,
- 56 -
can be 1/5000 to 1/10, usually 1/25C0 to 1/~0
and more usually 1/1000 ~o 1/30 of ~he diameter
of the microspheres.
In an embodiment of the invention, the
S ratio of the diameter to the wall thickness
of the microspheres is selected such that
the microspheres are flexible, i.e. can be
deformed under pressure without breaking.
The diameter and wall thickness of
the hollow microspheres ~ill o~ course
effect the average bulk density of the
microspheres. The glass microspheres pre-
pared in accordance with the invention will
have an average bulk density of 0.2 tO 15
lb/ft3, preferably O.S to 10 lb/ft3 and
more preferably 0~75 to 6 lb/ft3. r.~ere
increase strength is desired, the micro-
spheres can have an average bulk density
of 1.0 to lS lb/ft3, preferably 1.5 to
12 lb/ft3 and more preferably 2 to 9 lb/ft3.
The hollow glass microspheres of ~he
present invention can be used to, for example,
contain o~ygen gas (at ambient temperature)
under a pressure oE 100 ~o 3,000 p.s.i.g.,
pre~erably 100 to 1,000 p.s.i.g. and
hydrogen under a pressure or 50 to 4,000
p.s.i.g., preferably 50 to 2,000 p.s.~.g.
(a~ ambien~ pressures). The respective gases -
can be placed in relatively light weight
3~ containers and used for under water oxygen
torch cutting or welding. The oxygen con-
tainer and hydrogen container can each contain
a small "roller drum" mill to which is fed
necessary amounts or the respective microspheres
~o obtain and maintain a desired operating
pressure ~or each of the gases. The oxygen con~aining
.
- 57 -
5~
glass microspheres can also be used in sub-
mersible vessels for emergency oxygen supply.
This procedure avoids the need of heavy pres-
sure resistant metal cylinders and complex
valve and metering systems.
Microspheres containing oxygen under high
pressure can be stored separately than mixed
or can be directly mixed with a solid, powdered
or liquid fuel such as used in rocket engines.
The solid or liquid fuel and/or oxvgen con-
taining microspheres are fed directly into a
combustion chamber, the oxygen released and
anv remaining portion or the microspheres
expelled with the combustion e~haust pro-
ducts.
The mic~ospheres can also be used todesign low pollution exhal~st combustion engines.
The o~vgen containing microspheres can be
used with methane or hydrogen con~aining
; 20 microspheres. The respective microspheres
would be crushed to release the contained
gases, the gases mixed and burned to drive
a turbine or "conventional" internal com
bustion engine Any unburned remains of the
crushed microspkeres are collecced and later
removed fro~ the engine.
he hollow glass microspheres are made
which contain a mixture of deuterium and
tritium gases at a pressure of 1000 to 1500
p.s.i.g. (ambient temperature) which find
particular use as targets in laser hydrogen
fusion reactors and/or research. These
microspheres can be stored at about ambient
- 58 - -
.
~s~s~
temperatures ~ithout any significant diffusion of the high pressure
gases out of the microspheres.
The hollow glass microspheres may contain carbon monoxide
gas at pressures of 500 to 3000 p.s.i.g., preferably 500 to 1000
p.s.i.g. (ambient temperature) which greatly facilitates the
handling and/or storage of this gas.
The hollow glass microspheres may contain an unstable
gas, for example, acetylene at pressures of 10 to 750 p.s.i.g.
(ambient temperature). The use of microspheres to contain the
acetylene gas is found to stabilize the gas by limiting the
contact between adjacent gas molecules such that chain decomposi-
tion reactions of the gas molecules do not occur.
Radioactive fuel waste gases such as xenon and iodine
may be encapsulated in the hollow glass microspheres at contained
gas pressure o~ 400 to 600 p.s.i.g. (ambient temperature). These
microspheres can be stored in geological formations or mixed
with concrete, surrounded by a lead shield and safely stored in
any suitable location.
The microspheres may contain oxygen under high pressure
and can be uniformly mixed with solid, plastic, liquid or gaseous
explosive materials to make a stable premixed explosive
- 59 -
-
lr,~ 55
composition with a self contained oxident.
Since the oxvgen is contained in the micro-
sphere, it is completely separated from the
explosive material and until time of detona-
tion the e~plosive mixtures are very stable.
The mix~ure is detonated bv a conventional
percussion cap. The present invention thus
avoids the need of nonstable and e~pensive
oxidents.
The simplicity, controllability and low
cost of the microsphere system of the present
invention allows for the storage, shipment
and uses of gases under high pressure wit~ the
same ease of handling as liquids and/or free
flowing powders. A particular advantage of
the disclosed system would be in reacting
tr~o or more gaseous materials or a reactant
gas and a liquid. For ex~mple, the reactant
gases could be first homogeneously mi~ed
and the reaction carried out by ~eeding the
mi~ture to a reaction vessel in which the
mi~ed microspheres would be crus~ed at a
controlled rate.
The hollow glass microspheres are dry,
inert, free ~lowing and can be safely handled
and processed, and do not require special
storage or handling ~acilities. Further,
since the volume and pressure o eac~
microsphere is controlled, the weighc of
a given amount of gas is easily measured.
The hollow glass microspheres o~ the
present invention have a distinct advantage
of being very strong and capable of
supporting a substantial amount of weight.
~`
- 60 -
. . .
s
They can thus be used to make simple inexpensive
self-supporting or load bearing handling and
storage systems.
A specific and advantageous use of the
hollcw glass micros?heres of the invention is in
manufacture of inertial confinement fuel
target systems and systems for the storage
of radioactive atomic waste materials.
EX~PLES
E~ample 1
A glass composition (Col. A) comprising
the following constituents is used to make
hollow glass microspheres.
2 A123 CaO ~gO B2o3 Na20
W~% 55-57 18-22 5-7 10-12 4-5 1-2
The glass composition is heated to a
temperature of 2650 to 2750F. t.o form a fLuid
molten gl~s ~avmg a viscosity of 10 to 60 poises, e.g. 35 to 60
poises and a surface tens:ion of 275 to 325
dynes per cm.
The molten glass is i.ed to the apparacus
of Figures 1 and 2 of the drawings. The
molcen glass passes through annular space
8 of blowing nozzle 5 and forms a thin
liquid molten glass film across the orifices
6a and 7a. The blowing nozzle 5 has an
outside diamèter of 0.040 inch and orifice
7a has an insi~e diameter of 0.030 inch.
The thin liquid molcen glass film has a
diamecer or 0.030 inch and a thickness of
O.005 inch. An oxygen gaseous material
blowing gas at a temperature or 2650F. and
- 61 -
3~55
at a pressure of 6000 to 3000 p.s.i.g. is
applied to the inner surface of the molten
glass film causing the film to distend down
wardly into an elongated cylinder shape with
its outer end closed and its inner end
attached to the outer edge of orifice 7a.
- The pressure in the area of the blowing
nozzle is maintained at slightly less ~han
6000 to 8000 p.s.i.g.
The transverse jet is used to di~ect
an inert entraining fluid which consists of
nitrogen at a temperature of ~600F. over
and around the blowing nozzle 5 which
entraining fluid assists in the ~or~ation
and closing of the elongated cylinder shape
and the detaching of the cylinder from the
blowing nozzle and causing che cylinder to
fall free of the blowing nozzle. The trans-
verse jet is aligned at an angle of 35 to
~0 50 relative ~o the blowing nozzle and a
line dra~n through the center axis of ~he
transverse jet intersects a line drawn
through the center a~is of the blowing
nozzle 5 at a point ~ to 3 ~imes the ou~-
side diameter of the coa~ial blowingno~le 5 above the orifice 7a.
The free falling elongated cylinders
filled wi~h o~ygen gas quickly assume a
spherical sh`ape and are rapidly cooled to
about ambient temperature by a quench
fluid consisting of a fine water spray
at a temperature of 90 to 150~. which
quicklY cools, solidifies and hardens ~he
glass microspheres.
- 62 -
.. . . . .. . .
5 ~
Clear, uniformed size, smooth hollow glass
microspheres having a 20C0~o 3000 micron
diameter, a 3 to 10 micron, preferably a
20 to 30 micron, wall thickness and filled
with oxygen gas at an internal contained
pressure of 1025 to 1370 p.s.i.g. are obtained.
The microspheres are closely e:~amined and
the walls are found to be free of any trapped
gas bubbles.
Exam~le 2
A glass composition (Col. B) comprising
the following constituents is used to make
transparent hollow glass microspheres.
2 123 Li2 MgO B2O3 Na2O K2O
~t% 6~-64 6-8 14-16 0-2 2-3 1-2 0.5-1
The glass composition is heated ~o a
tempera~ure of 2650 to 2750F. to form a fluid
molten glass having a viscositv of 35 to 60
poises and a surace tension of 275 to 325
dynes per cm.
The molten glass is ~ed to the apparatus
of Figures 1 and 3a of the drawings. The
molten ~lass is passed through annular
space 8 of blowing nozzle 5 and into
tapered portion 21 o outer nozzle 7~ The
molten glass under pressure is squeezed
through a fine gap formed between the
outer edge of oririce 6a and the inner
surface 22 of the tapered portion 21 of
outer nozzle 7 and forms a thin liquid
molten glass film across the orifices 6a
and 7a'. The blowing nozzle S has an out-
side diameter of 0.04 inch and orifice 7a'
- 63 -
5 5
has an inside diameter of 0.01 inch. The
thin liquid molten glass film has a diamecer
of 0.01 inch and thickness of 0.003 inch.
A mixture of deuterium and tritium gases,
for manufacture of inertial confinement
system targets, is used as the blowing gas
at a temperature of 2700F. and at a pres-
sure o~ 1~,000 to 14,000 p.s.i.g. is
applied to the inner surface of the molten
glass film causing the ~ilm to distend
outwardly into an elongated cylinder shape
~ith its outer end closed and its inner
end attached to the outer edge of orifice
:~ 7a'. The pressure in the area of the
blowing nozzle is maintained at slightly
less than 12,000 to 14,000 p.s.i.g.
The transverse jet is used to direct
an inert entraining ~luid which consists
of nitrogen at a temperature of 2600F.
over and around the blowing nozæle 5
~hich entraining fluid assi.sts in the
formation and closing of~ of the elongated
: cylinder shape and the detaching of the
cylinder ~rom the blowing nozzle and causing
~5 the cylinder to rall free of the blowing
nozzle. The transverse jet is aligned
at an angle of 35 to 50 relative to
the blowing nozzle and a line drat~n
through the cènter axis of the trans-
verse jet intersects a line drawnthrough the center axis of the blo~ing
nozzle 5 a~ a point 2 to 3 times the
outside diameter of the coaxial blowing
nozzle 5 above orifice 7a'.
. - 64 -
5 S
The free falling elongated cylinders
filled with the inertial confinement fuel gas
quickly assume a spherical shape. The micro-
spheres are contacted with a quench fluid
S consisting of a fine water spray at a tem-
perature of 90 to 150F. which quickly
cools, solidifies and hardens the microspheres.
Clear, uniformed size, smooth, hollow
glass microspheres having an about 800
to 900 micron diameter, a 8 tO 20 micron
wall thickness and an internal contained
pressure of laser target fuel of 2040 to
2380 p.s.i.g. The thin walls of the micro-
spheres are free of any trapped gas bubbles.
Exam~
The glass composition (Col. C) comprising
the ~ollowing constituents is used to make
hollow glass microspheres.
SiO2 A12O3 Zirconla CaO MgO B203 Na2O K2O
Wt% 45-55 8-10 16-18 1-2 0-1 1-2 1-2 0-1
The glass composition is heated to a
temperature of 2650 to 27S0F. to form a
; fluid molten glass having a viscosity of
35 to 60 poises and a surface tension of
275 to 325 dynes per cm.
The molten glass is fed to the apparatus
of Figures l and 3a of the drawings. The
molten giass is passed through annular
space 8 of blowing nozzle S and into
tapered portion 21 of outer nozzle 7. The
molten ~lass under pressure is squeezed
through a fine gap between the outer edge
of orifice 6a and the inner surface 22 of
- 65 -
~ 5 S
,~,
the tapered portion 21 of outer nozzle 7 and
forms a thin liquid molten glass fil~ across
the orifices 6a and 7a'. The blowing nozzle
5 has an outside diameter or O.OS inch and
orifice 7a' has an inside diameter of 0.03
inch. The thin liquid molten glass film
has a diameter of 0.03 inch and a thickness
of 0.01 inch. A gaseous atomic energy
fuel waste product consisting of tritium
blowing gas at a temperature of 260QF.
and at a pressure of 5000 to 6000 p.s.i.g.
is applied to the inner surface of the
molten glass film causing the film to
distend out~ardlv into an elongated
cylinder shape with its outer end closed
and itS inner end attached to the outer
edge of orifice 7a'. The pressure in the
area of the blowing nozzle is maintained
at slightly less than S000 to 60~0 p.s.i~g.
~ 20 The transverse jet is used to direct
`; an inert encraining ~luid which consists
o nitrogen gas at a temperature of 2500F.
over and around the blowing nozzle 5 which
entraining Cluid assists in the formation
~5 and closing or the elongated cylinder shape
and the detaching of ~he cylinder from the
- blowing nozzle and causing the cylinder
to fall free of the blowing nozzle. The
transverse j`et is aligned at an angle of
35 to 50 relative to the blowing nozzle
and a line drawn through the center axis
of the transversè jet intersects a line
drawn through the center a~is of the
blowing nozzle 5 at a point 2 ~o 3 times
- 66 -
3~ 5 S
~;
the outside diameter of rhe coa~ial blowing
nozzle 5 above orifice 7a'.
The rree falling elongated cylinders
filled with the gaseous atomic waste material
quickly assume a spherical shape. The
microspheres are contac~ed with a quench
fluid consisting of an ethylene glycol
spray at a temperature of 0 to 15F. which
quickly cools, solidifies and hardens the
glass microspheres.
Clear, uniformed size, smooth, hollow
glass microspheres having an about 3000
to 4000 micron diameter, a 10 to 20 micron
wall thickness and an internal contained
lS pressure or the atomic gas waste material
of 850 to 102n p.s.i.g. are obtained. ~ne glass compo-
sition from which these microspheres are
made are alkali resistant: and the micro-
spheres can ~e convenient:ly stored in
concrete.
E~am~e 4
A hollow glass microsphere containlng
hydrogen gas under pressure is made using
the same glass composition, appara'us and
?rocedure described in E~zmple l with the
following differences. Hydrogen gas is used
as the gaseous material blowing gas a~ a
temperature~o~ 2400F. and a pressure of
4000 co 5000 p. s . i. g. is applied to the
inner surface of the molten glass film
causing the film to distend downwardly
into an elongated cylinder shape with its
outer end closed and its inner end attached
to the oucer edge of orifice 7a. The
- 67 -
_
~1 ~5I~55
pressure in the area of the blowing nozzle is
main~ained ac slightlv less than 4000 to
5000 p.s.i.g.
The transverse jet as beore is used to
direct an inerc en~raining fluid which con-
sists of nitrogen at a temperature of 2400F.
over and around the blowing nozzle 5 which
entraining fluid assists in the formation
and closing of the elongated cylinder snape
and the detaching of the cylinder from the
blowlng nozzle and causing the cylinder to
fall free of the blowing nozzle.
The free falling elongated cylinders
filled with hydrogen gas quickly assume a
spherical shape and are rapidly cooled as
before to about ambient temperature by a
quench fluid which quickly cools, solidiies
and hardens the glass micr.ospheres.
Clear, uniformed size, s~ooth, hollow
glass microspheres having a 2000 to 3000
micron diameter, a S to 10 micron wall
thi~kness and filled with hydrogen gas
at an internal concained plressure of about
750 to 950 p.s.i.g. are obtained. The
hydrogen gas containing mic-ospheres can
be used to store and handle hydrogen
gas and can themselves be used as a
fuel in an hydrogen-oxygen combustion
svstem.
- 68 -
~ 5
Example 5
.
A hollow glass microsphere con~aining
carbon dioxide gas under pressure is made
using the same glass composition, apparatus
and procedure described in Example l wi~h
the follo~ing differences. Carbon dio~ide
gas is used as the gaseous material blowing
gas at a temperature o~ 2400F. and a pres-
. sure of 4000 to S000 p.s.i.g. is applied to
the inner surface of the molten glass filmcausin~ the film to distend outwardly into
an elongaced cylinder shape with i~s outer
end closed and its inner end attached to
the outer edge of orifice 7a. The pressure
in the area of the blowing nozzle is main-
tained at slightly less than 4000 to S000
p.s.i.g.
The transverse jet as before is used
to direct an inert entrai.ning fluid which
consists or nitrogen a~ a temperature of
2400F. over and around the blowing nozzle
5 which entraining luid assists in the
formation and closing o~ of the elongated
cylinder shape and the detaching of the
cylinder from the blowing noz71e and
causing the cylinder to fall free of the
blowin~ nozzle.
The free falling elongated cylinders
filled with carbon dio~ide gas q~ic'~ly
assume a spherical shape and are rapidly
coole& as before to about ambient tem-
perature by a quench fluid which quickly
cools, solidifies and hardens the micro-
spheres.
~ - 69 -
, . . ...... . . . _ _
Clear, uniformed size, srnooth, hollow glass microspheres
having a 2noo to 3000 micron diameter, a 5 to 10 micron wall thick-
ness and filled with carbon dioxide gas at an internal pressure o
about 750 to 950 p.s.l.g. are obtained. The carban dioxide con-
taining microspheres can be used to store and handle carbon diaxide
gas and can themselves be used in a "dry powder" fire extinguisher
system as the fire extinguishing ingredient.
A transparent or reflective metal coating can be deposited
on the inner wall surface of the microspheres produced in accordance
with the above Examples by the addition to the blowing gas of a
metal vapor, e.g. zinc vapor, dispersed metal particles~ e.g~
aluminum powder or an organo metal compound, e.g. nickel carbonyl.
The microspheres can also be made in a non-filamented as well as a
filamented form by following the teachings of the presen~ invention.
Further, applicant in his copending application Serial No. 334,618
filed August 27, 1979 has presented specific Examples for making
microspheres having a thin metal layer deposited on the inner wall
surface thereof ~rom a blowing gas consisting a metal vapor and
from a blowing gas containlng dispersed metal particles and ~or
making non~filamented microspheres and filamented microspheres
- UTILITY
The hollow glass microspheres of the present invention have
many uses including the handling and storage of oxygen, hydrogen,
nitrogen and carbon dioxide at high pressures in light easy to
handle containers
The process and apparatus described herein can also be used
to encapsula~e and store gaseous materials in hollow glass micro-
spheres of a suitable non-interacting composition, thereby allowing
- 70 ~
ss
handling or storage of gases generally, and of corrosive and toxic
or otherwise hazardous gases specifically. Because of the relative
great strength of the microspheres, the gases may be encapsulated
ln the microspheres and stored at high contained gas pxessures. In
the case where disposal by geological storage is desired, for
example, for poisonous and/or other toxic gases, the gases can be
encapsulated in very durable alumina silicate composition or æircon-
ia composition glass microspheres which can subsequently be embed-
ded, if desired, in a concrete structure. The glass microspheres
of the present invention, because they can be made ~o contain gases
under high pressure, can be used to manufactur~ fuel targets for
inertial confinement fusion reactor systems.
- 71 -
S
The microspheres can be used to manu-
acture inertial confinement fusion fuel
targets for use in hydrogen fusing reactors
and/or research. Because of the abilicy
of manufacturing microspheres of specific
diameters and wall thicknesses in which
there is contained the target fuel under
predetermined high pressure and because
the microspheres can be produced with
glass compositions ~hich substantially
prevent diffusion of gases into or out
of the microspheres and glass compositions
which have the desired acomic constituents,
the microspheres find particuLar and
advantageous use in the manufacture of
the inertial confinement targets.
The present invention also has
particular utility for encapsulating
toxic, corrosive and/or radioactive gaseous
materials in a manner such thac chey can
be compressed at a high pressure to a sub-
stantially reduced volume and pu~ into a
form concained in the mic:rospheres in
which they are safe and easv co handle.
The constituents of the g:Lass composition
can be selected to be resistant to attack
bY che material encapsulated and can be
made resistant to alkali such that the
microspheres`can be mixed with and stored
in concrete bloc~s. The concrete blocks
can be safely shipped to geological sites
for permanent storage.
- 72 -
The process and apparatus described
above can be used to blow microspheres
from any suitable molten material having
sufficient viscosity and surface tension
a~ the temperature at which the microspheres
are blo~n to form the elongated cylinder
shape of the material being blown and to
subsequently be detached to form the
spherical shape microspheres.
~here the gases to be encapsulated are
unstable at high temperatures, low tempera-
ture melting glass compositions can be used
such as those containing relatively high
concentrations of lead and/or thallium.
The microspheres, because they are
made from very stable glass compositions,
are not subject to degradation by out-
gassing, aging, moisture, weathering
or biological at~ack and the glass from
~0 whic~ the microspheres are made do not
produce toxic fumes when exposed to
very high temperatures or fire.
The glass compositions can be trans-
parent, translucent or opaque. A suitable
coloring material can be added to the
glass compositions to aid in identifi-
cation o~ microspheres of speciried size,
wall thickness and contained gaseous
material. The coloring materials can
also be used to identify the contained
- gas pressures.
The glass compositions can also be
selected to produce microspheres that
will be selectively permeable to
specific gases and/or organic molecules.
.
~.~5i~`4355
These microspheres can then be used as semi-
permeable membranes to separate gaseous or
liquid mixtures.
The process and apparatus
can also be use~ to form
microspheres from ther~osetting and thermo-
plastic resin materials such as polyethylene,
polypropylene, polystyrene, polyesters,
polyurethanes, phenolformaldehyde resins
and silicone and carbonate resins. The
lower temperature melting resins are
particularly useful for encapsulating gases
that are unstable at high temperatures.
The process and apparatus
can also be used to form microspheres
from metals such as iron, steel, copper,
zinc, tin, brass, lead, aluminum, and
magnesium~ In order to form microspher~s
from these materials, suitable additives
are used which provide at the film
surface of the microsphere a sufficiently
high viscosity that a stable microsphere
can be formed.
In carrying out the process,
the molten material to be
used ~o torm ~he microspheres is selected and
can be ~rea~ed and/or mixed with other
materials to adjust their viscosity and
surface tension characteristics sucn that
at the desired blowing temperatures they are
capable of forming hollow mlcrospheres of
the desired size and wall thickness.
- 74 -
3~;;5
..... ~
The process can
also be carried out in a centrifuge apparatus
in which the coaxial blowing nozzles are dis-
posed in the outer circumferal surface of
the centriruge at an angle of 15 to 75 away
from the direction of rota~ion. ~olten glass
is fed into the centrifuge and because of
centrifugal forces rapidly coats and wets
the inner wall surface of the outer wall of
the centrifuge. The molten glass is fed
into the outer coaxial nozzle. The inlet
~o the inner coa~ial nozzle is disposed
above the coating of molten glass. The
blowing gas is as before fed into the
lS inner coaxial nozzle. The transverse jet
entraining fluid is provided by the
action of the ambient gas outside or the
cencrifuge as che centri~uge rotates
about its central axis. ~n e~ternal gas
can be directed along the longitudinal
a.Yis of the centrifuge. to assist in
removing the microspheres from the
vicini~y of the centri~uge as they are
~ormed. Quench fluid can be provided
as before~
These and other uses of the present
invention.will become apparent to those
skilled in the art rrom the foregoing
description and the following appended
claims.
It ~ill be understood that various
changes and modifications may be made in
the invention and that the scope thereof
is no~ to be limited except as set ~orth
in the claims.
