CA2187330A1 - Process for producing membranes from nanoparticulate powders - Google Patents
Process for producing membranes from nanoparticulate powdersInfo
- Publication number
- CA2187330A1 CA2187330A1 CA002187330A CA2187330A CA2187330A1 CA 2187330 A1 CA2187330 A1 CA 2187330A1 CA 002187330 A CA002187330 A CA 002187330A CA 2187330 A CA2187330 A CA 2187330A CA 2187330 A1 CA2187330 A1 CA 2187330A1
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- Canada
- Prior art keywords
- powder
- accordance
- layer
- porous structure
- ceramic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000000843 powder Substances 0.000 title claims abstract description 69
- 239000012528 membrane Substances 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 49
- 239000011148 porous material Substances 0.000 claims abstract description 40
- 239000002245 particle Substances 0.000 claims abstract description 31
- 238000009694 cold isostatic pressing Methods 0.000 claims abstract description 4
- 239000000919 ceramic Substances 0.000 claims description 36
- 239000002184 metal Substances 0.000 claims description 16
- 229910052751 metal Inorganic materials 0.000 claims description 16
- 239000011362 coarse particle Substances 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 10
- 238000005056 compaction Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000000654 additive Substances 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 10
- 238000000926 separation method Methods 0.000 description 9
- 238000009826 distribution Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 238000005266 casting Methods 0.000 description 3
- 229910010293 ceramic material Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000007569 slipcasting Methods 0.000 description 3
- 238000003980 solgel method Methods 0.000 description 3
- 239000010457 zeolite Substances 0.000 description 3
- 229910021536 Zeolite Inorganic materials 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 239000006259 organic additive Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000001612 separation test Methods 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 101100182661 Arabidopsis thaliana LUL2 gene Proteins 0.000 description 1
- 241001527806 Iti Species 0.000 description 1
- 101100240353 Mus musculus Nectin4 gene Proteins 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 210000004124 hock Anatomy 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0041—Inorganic membrane manufacture by agglomeration of particles in the dry state
- B01D67/00413—Inorganic membrane manufacture by agglomeration of particles in the dry state by agglomeration of nanoparticles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0041—Inorganic membrane manufacture by agglomeration of particles in the dry state
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
- B01D39/2027—Metallic material
- B01D39/2031—Metallic material the material being particulate
- B01D39/2034—Metallic material the material being particulate sintered or bonded by inorganic agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
- B01D39/2068—Other inorganic materials, e.g. ceramics
- B01D39/2072—Other inorganic materials, e.g. ceramics the material being particulate or granular
- B01D39/2075—Other inorganic materials, e.g. ceramics the material being particulate or granular sintered or bonded by inorganic agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0041—Inorganic membrane manufacture by agglomeration of particles in the dry state
- B01D67/00411—Inorganic membrane manufacture by agglomeration of particles in the dry state by sintering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/05—Cermet materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/11—Making porous workpieces or articles
- B22F3/1103—Making porous workpieces or articles with particular physical characteristics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
- B22F7/002—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of porous nature
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
- B01D2323/081—Heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/10—Specific pressure applied
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mechanical Engineering (AREA)
- Geology (AREA)
- Composite Materials (AREA)
- Materials Engineering (AREA)
- Ceramic Engineering (AREA)
- Nanotechnology (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
A process for producing a membrane having a plurality of Angstrom-size pores in which a powder comprising nanometer-size particles is compacted to form a consolidated powder porous membrane. In accordance with a preferred embodiment, the powder is compacted by cold-isostatic pressing.
Description
Wo 95l27556 2 1 8 7 3 3 0 ~ ~llU~ r ~ ~c~
PROCESS FOR PRODUCING MF~MRRANF~S
FROM NANOPARTICULATE POWDERS
RA~ K-~uNl~ OF THE INVENTION
Field of the Invention This invention relates to a process for producing structures, in particular, ~, having Al~y~LL size pores. Membranes, in particular, prepared in ac-:uL-la~lce with the process of this invention are suitable for use in applications such as high t~ -- aLuL~ gas separation and as :-uL~LL.,Le materials for the deposition of ultra-thin ceramic or metal films.
Description of Prior Art Nembrane t ~Qrhnnlogy is rapidly h ~ ; n~ ~n ~ OLLallL research area in rhQmi~ Qn~inQQring, ~ pQci~lly in the separation of gases. ~QpQn~in~ on the LLU~:LUL~: and nature of the materials, LLe~na~oLL of fluids, solutes or molecules through membranes can occur by one of several different --h;lnir ~. The transport of any species through es ~ which is similar to any separation process in chemical engineering, is driven by the difference in free energy or rhQmi~ ~l potential of that species across the membrane. In actual use, the membranes encounter various combinations of harsh rhQmirll environments and high temperatures. Thus, it is critical to evaluate the effects of changes in the thermal rh~mic~l properties and dimension w0 95/27s56 2 1 8 7 3 3 0 r~ o ~
st~bility of membrane materials on separation performance under dif ferent operating conditionfi .
The primary def iciency of the current generation of ceramic membranes is their poor damage tolerance and long-term reliability. On the other hand, the main atlvallLag~s of ceramic materials over conventional metals in the primary ~Lr u~.Lulcll applications are their superior ~LLe.lYUI and, at high temp~:L~tu~as, good thermal stress resistance, and ~Yrol 1 ~nt oxidation, corrosion, and erosion resistance. Unfortunately, the brittleness of ceramics has restricted their use in these applications where materials ~"~ cs is an; L~I~L criterion. In addition, ceramic materials are susceptible to thermal ~7L~ abnas and thermal ~hock failure, failures often occurring at t~ ~ c.tu,e:s that are lower than the service t~ clLu~ ~=s during heating and cooling.
Nembrane processes have aLL- c.-;Led much attention from an energy conservation stand-point in industrial gas separation processes. The separation -- ~ni ~ ~ of gases by porous solid membranes are conventionally classif ied into four types: 1) Knudsen diffusion, 2) surface diffusion, 3) rAri~ ry con~l~ncation with liquid flow, and 4) molecular sieving. In general, a narrow pore size distribution in a membrane system is needed in order to obtain a high degree of separation of mixtures, the re~uired modal size ~ r~n~l i n~
on the type of mixture to be separated.
~YO 95/2~556 ~) 2 1 8 7 3 3 0 rcrn1sss/0~3s~
Conventional preparation of ceramic ~aterials starts uith powders produced either from synthetic reactions ithout stric~ chemical process control or by grinding up naturally occurring minerals To prepare the final cerzmics, powders zre consolidated into porous compacts, then sintered into strong, dense ceramics. During these transformations, the grain size increases, pore shapes change, and the interior pores become smaller or ~;CApp~Ar completely .
WO-A-90/00685 describes a process using particle sizes of 50 microns. The membrane is considered to be used as oil bearing. EP-A-0 ' 580 ' 134 shows a process using particle sizes of 1 to 3 microns and achieves therefore pore sizes larger than 100 A.
Ceramic membranes having ultra-fine pores are typically formed by so-called "wet processes, n that is, DroceSSeS requiring the use of a solvent. Such processes include slip casting, gel casting, extrusion, and the sol-gel process. The slip casting and gel casting processes utilize large amounts of solvents as well as dispersing agents to form z slurry which is then cast in a mold to form the desired membrane. Extrusion typically involves the addition of a solvent along with die lubricants and an organic polymeric binder to a cera=ic powder to form a mixture which is then extruded to form, typically, tubular membranes. In the sol-gel process, a solution of organo-metallic material is formed and then gelled. The solvent in the gel is then removed alld the re-- i n i n~ structure heat treated .
Each of the slip casting, gel casting, extrusion and sol-gel processes utilize solvents and most of these processes utilize organic additives which must later be A~IJiJ'., ~n~T
Woss/2755~ 2 1 87330 F~l~ o~c7 removed. This greatly limits the minimum size o~ the pores, typically submicron size, which can be formed in the resulting :7LL~I~ LUL~ due to the requirement that the removal of solvents or organics requires that the pore size in the I~LU. LUL2 be larger than the molecules being removed.
In addition, the removal of solvents produces CArillAry stresses in the D~Lu~:LuL~: which increase as the pore size of the structure decreases. To avoid cracks in the submicron pore size D~Lu LUL~8, elaborate and expensive drying schemes are re~uired. When n~nnci~e or AnYDLLI size pores are desired, the problem become8 e-~cDnt;:~lly ;n Lable due to the l L~ ' capillary stresses encountered. See Hsieh, H.P. et al., ~Mi~:LuuuLuus Ceramic Nembranes", Polvmer Journ~l. Volume 23, No. 5, pages 407-415 (1991? which teaches ConvPntinn~1 ceramic forming t~Drhn;5~uDc such as extrusion, ession and injection molding which can be used to produce ceramic membranes with Dy ~ ic DLLLl~iLUIt:S and large pores from particles of well controlled size distributions. See also Chan K. et al., "Ceramic Membranes-Growth FLu~ua. LD and 0,UUUL Lu..ities'', Ceramic Bullet;n, Volume 70, No. 4, (1991) which teaches the use of the sol-gel prûcess for producing membranes having submicron pore sizes; Zievers, J. F. et al., "Porous Ceramic# For Gas Filtration", CerAm;r Bullet;n. Volume 70, No. 1, pages 108-111, (1991) which teaches the use of layered porous ceramic filter elements for gas filtration; and Breck, D. W. et al., "Nolecular Sieves", Scientific American (1959) which teaches ~ v~O95fl7556 2187330 ~crf~Sg~0435l the use of molecular sieves for separating very similar mo l ecul es .
Zeolites are a group of minerals, both naturally occurring and synthetically prepared, whose crystal structures contain pores on the order of about 3 to 20 AnyaLLI ~ in size. However, the preparation of monolithic discs or sheets of material using zeolite with only 3 to 20 Anu,~LLu_ size rnnnPc~p~ pores is not possible because the resulting micron size powder would contain crystals of zeolite which form shapes containing micron size pores with A~ .LL~ size pores within the crystals.
EP-A-0 ~ 426 ' 546 and FR-A-2150390 disclose processes for producing membranes using additives or solvents The membranes achieved by these processes have pores sizes larger than 100 A
SUM~L~RY 0~ ~E IN~rENTION
Accordingly, it is an objection of this invention to provide a process for producing a monolithic structure having An~:,LL, size and nanosize pores.
It is another object of this invention to produce ceramic and/or metal membranes having n;~nnsi 7e and Angstrom-size pores.
It is yet another obj ect of this invention to provide a process for producing ceramic andJor metal membranes which requires no solvents or dispersants which can require elaborate and expensive drying schemes to avoid cracks in the resulting submicron ~L~u-,LuLe:.
It is yet another obj ect of this invention to provide a process for producing ceramic and/or metal membranes which avoids the use of organic additives or solvents which must be removed during the manufacturing -tr Wo ss/27ss6 2 1 8 7 3 3 0 I/L_ _ 'O ~ IC'~
process and, thus, limit the minimum pore ~ize obtainable to the size of the molecules being removed from the final product .
These and other objects of this invention are achieved by a process f or producing a membrane having a plurality of Allg~L size pores comprising the steps of forming a loose powder layer of at least one of a metal powder and a ceramic powder comprising a plurality of subst~ntjAlly all nanometer-size particles and compacting said loose powder layer of said at least one of said metal powder and said ceramic powder to form a con~ol 1~9Ated powder porous membrane. By "subs~An~;Ally all r-- ~r-size particles, " we mean a powder having greater than about 959 nanometer-size particles. A critical feature of this process is the requirement that nanometer-size ceramic powders be utilized. In a preferred '-';- L of the process of this invention, compacting of the nanometer-size particles is carried out by cold-isostatic pressing.
To form membranes having highly uniform nanometer-size pores, it is generally desired that the nanoparticulate powder be relatively uniform in size. In addition, the mean pore size of the membranes produced in accordance with the process of this invention can be controlled based upon the mean particle size of the powder being pressed. That is, the smaller the mean particle size of the powder, the smaller will be the mean pore size of the resulting .e. Membranes ~Luduc~d in accordance with this ~ wossn~ss6 2 ~ ~ 7330 : Pcr~llss~lo~l~7 process have a higher porosity than those produced }~y other known processes for producing membranes, in particular, ceramic membranes.
D~SCRIPTION OF ~ u ~M~ODTlrFNTS
In accordance with a preferred ~hoA;-- ~ of this invention, c.nes having a plurality o~ AnyaL~ ~ size pores are produced by compacting at least one of a metal powder and a ceramic powder comprising substantially all n:-~ t~r-size particles to form ~ roncnl i~Ated porous layer of powder, that is, a cnncol ;A~ted powder porous membrane, the compacting being carried out by cold-isostatic pressing.
To eliminate large pores f rom within the resulting ~L .,~ Lu,æ, that is, pores greater than about three t3) times the particle size employed, compaction ~Le:aa~LæS between abou~(l5,000 psi) and about~,~300,000~si~ are preferred.
"'03 To produce a membrane having uniform pore sizes in accordance with the process of this invention, nanometer size particles having a narrow particle size distribution are desirable. In particular, it is preferred that the metal and/or ceramic powder comprise at least about 98 n;l- ~t~r-Size particles an~ that at least 95% of the nanometer-size particles be less than about 30 nanometers.
In a particularly preferred ~"hoAir L, the particle size of the nanometer-size particles is in the range of about 2 nanometers to about 30 n;~- ' F.rS.
The consolidated powder porous membranes produced in accordance with this process are strong, the particles WOgS/27556 2 l 8 7 3 3 0 r~l" ~c~c7 being bonded ~c a result of cold welding and electrostatic forces. In accordance with another preferred ~ t of this invention, the ~LLt~ Lil of the membrane can be in-;L-ased by fast-firing the ~ nncnl i~l~ted porous layer of powder. However, there are two; L~.l.L heating conditions which must be observed - a low sintering t~ cltULe: and a short hold time. A low sintering t~ cltuLe: minimi7~c the amount of d~ncif;c~tion taking place and, thu5, r-~nt~;rc the large porosity present in the membrane. A short hold time m1n;m;7Ac the amount of particle growth and, thus, reduces the amount of pore growth in the resulting - c-l.e.
For ceramic ~ ' anes, sintering ~ -tuL~s required by the process of this invention are typically a few hundred degrees lower than the temperatures reguired to densify the ceramic. For example, alumina can be _ l~t~ly densiried at 1550-C, but membranes produced in accordance with this process by compacting a ceramic powder comprising n ~r-size particles of alumina may be fired at lOoO-C
to strengthen it. In a preferred: ~ ir L of the process of this invention, the concol;~l~ted porous layer of ceramic material resulting from compaction of the ceramic powder i5 fired at a temperature between about 800-C and about 2000-C.
In accordance with a preferred: ir L of this invention, the hold time for the membrane within the firing process is less than 30 minutes and, preferably less than 5 minutes. CULL~ >~ in~ly~ a heating rate of about 0.5-C/minute to about 2000-C/minute is preferred. Upon Wo95~27~6 2 1`873~0. ` PCr/~159s~ C2 completion of the iring process, the resulting =e~rane is cooled, preferably as quickly as possible without causing da~age to the membrane.
EXA~PLE I
Approximately 4 grams of nanoparticulate 8 =ol percent Y2 O3-doped ZrO2 (YSZ) powder having a mean diameter of about 20 nanometers was die-pressed to form a disc of about~,(2 . 25"~ in ~ or, The ceramic disc was then cold-S7 rn~
isostatically pres5ed a~(55, 000 psi~. Pore-size distribution 3,~ Io8 ~
analysis of the pressed YSZ disc indicated that it was about 50S porous with a uniform distribution of pores. The mean pore radius of th~ membrane was det~rm;n~ to be about 27 An ~:.LL~ . In a gas separation test, the membrane prepared in accordance with this example was found to be effective in the separation of an H2/C02 gas mixture. The membrane was found to be at least four times more F -~hl e to H2 than to CO2 .
It will be apparent to those skilled in the art that different membrane shapes can be formed in accordance with the process of this invention including discs and tubes .
To improve the r~ n;c~ Le~l~Lh~ the membranes can be heat treated by fast-firing to preserve the uniformity of the pore size distribution. ~embranes produced in accordance with the process of this invention have a porosity of about 30% to 55%, that is, a~out 30% to about 55% porous. The mean pore radius of the membranes wo ss/~7ss6 2 1 8 7 3 3 ~ PCrlU59s/043s~
'~
produced in accordance with the process of thi6 invention i6 between about V5 to V20 of the mean particle diameter of the powder used. In other words, if a powder with a mean particle diameter of 10 n~- ~r~6 is used, a membrane with a mean pore radius of about 5 AnyaLL~ - will be obtained.
If ~ ,l,le support or multilayers of r- '_I~es are desired, powders of different particulate size can be pressed together to form r ' c~ne layers of different mean pore sizes. In particular, in accordance with one of the process of this invention for producing ~ultilayer membranes, the loose powder layer of nAr te~-size particles of metal powder and/or ceramic powder is rormed on a coarse particle layer of metal and/or ceramic powder particles where the coarse particle layer comprises a plurality of particles, aul/a~ Lially all larger than n~- tr~r-size. In accordance with one I ';--nt of the process of this invention, the loose powder layer and the coarse particle layer are simult~nQollcly compacted together, forming a multilayer c~7ncol ir~ted powder porous I,e, In accordance with another: -'i- L of the process of this invention, the coarse particle layer is compacted and the loose powder layer is formed on the compacted coarse particle layer and s~lh6r-~r~r~ntly compacted onto the compacted coarse particle layer to form a multilayer ~ nncol ~ ted powder porous membrane.
wo ssn7ss6 2 1 8 7 3 3 0 PCI/llS9~s/11~35i ~
EXi~PLE I I
This example demonstrates a method for makiny a ceramic membrane having a two-layer structure.
Approximately 4 grams of submicron size 8 mol percent Yz03-doped ZrO2 (YSZ) powder having a mean 1'9iA ' -r of about 0 . 3 microns were die-pressed to form a disc of ;,(2.25") in diameter. Before removal of the YSZ disc from the s~in1~cs steel die, approximately 0.2 g of nanoparticluate Al203 powder having a mean diameter of about lO nanometers were spread evenly on the top surface of the YSZ disc, and die-pressed once again to form a two-layer porous ~LLU~_~U' ~.
The two-layer ceramic structure was them cold-isostatically pressed at~ 58,000 psi~. Accordingly, the YSZ powder, in this /o8~
case, was used as the supporting :7LLuL~LuL~= for the thin Al203 membrane.
In a gas separation test, the membrzne prep2red in this example was found to be effective in the separation of H2/C02 mixture. The membrane was found to be at least four times more p~ ~hle to X2 than to C02. The gas transfusing rate across the membrane was ~ign;f;c:lntly Pnh~nl-~d in the two-layer membrane structure compared to that of Example I.
~ hile in the f oregoing specif ication this invention has been described in relation to certain preferred ~ LS thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional ~mho~l;r LS and that certain of 11 A'1~',L;~ .r, ~J
wo ss/27ss6 2 1 8 7 3 3 ~ Q4~C~
the details described herein can be varied c~n~ rably without departing from the basic prinl-;pl~ of the invention.
PROCESS FOR PRODUCING MF~MRRANF~S
FROM NANOPARTICULATE POWDERS
RA~ K-~uNl~ OF THE INVENTION
Field of the Invention This invention relates to a process for producing structures, in particular, ~, having Al~y~LL size pores. Membranes, in particular, prepared in ac-:uL-la~lce with the process of this invention are suitable for use in applications such as high t~ -- aLuL~ gas separation and as :-uL~LL.,Le materials for the deposition of ultra-thin ceramic or metal films.
Description of Prior Art Nembrane t ~Qrhnnlogy is rapidly h ~ ; n~ ~n ~ OLLallL research area in rhQmi~ Qn~inQQring, ~ pQci~lly in the separation of gases. ~QpQn~in~ on the LLU~:LUL~: and nature of the materials, LLe~na~oLL of fluids, solutes or molecules through membranes can occur by one of several different --h;lnir ~. The transport of any species through es ~ which is similar to any separation process in chemical engineering, is driven by the difference in free energy or rhQmi~ ~l potential of that species across the membrane. In actual use, the membranes encounter various combinations of harsh rhQmirll environments and high temperatures. Thus, it is critical to evaluate the effects of changes in the thermal rh~mic~l properties and dimension w0 95/27s56 2 1 8 7 3 3 0 r~ o ~
st~bility of membrane materials on separation performance under dif ferent operating conditionfi .
The primary def iciency of the current generation of ceramic membranes is their poor damage tolerance and long-term reliability. On the other hand, the main atlvallLag~s of ceramic materials over conventional metals in the primary ~Lr u~.Lulcll applications are their superior ~LLe.lYUI and, at high temp~:L~tu~as, good thermal stress resistance, and ~Yrol 1 ~nt oxidation, corrosion, and erosion resistance. Unfortunately, the brittleness of ceramics has restricted their use in these applications where materials ~"~ cs is an; L~I~L criterion. In addition, ceramic materials are susceptible to thermal ~7L~ abnas and thermal ~hock failure, failures often occurring at t~ ~ c.tu,e:s that are lower than the service t~ clLu~ ~=s during heating and cooling.
Nembrane processes have aLL- c.-;Led much attention from an energy conservation stand-point in industrial gas separation processes. The separation -- ~ni ~ ~ of gases by porous solid membranes are conventionally classif ied into four types: 1) Knudsen diffusion, 2) surface diffusion, 3) rAri~ ry con~l~ncation with liquid flow, and 4) molecular sieving. In general, a narrow pore size distribution in a membrane system is needed in order to obtain a high degree of separation of mixtures, the re~uired modal size ~ r~n~l i n~
on the type of mixture to be separated.
~YO 95/2~556 ~) 2 1 8 7 3 3 0 rcrn1sss/0~3s~
Conventional preparation of ceramic ~aterials starts uith powders produced either from synthetic reactions ithout stric~ chemical process control or by grinding up naturally occurring minerals To prepare the final cerzmics, powders zre consolidated into porous compacts, then sintered into strong, dense ceramics. During these transformations, the grain size increases, pore shapes change, and the interior pores become smaller or ~;CApp~Ar completely .
WO-A-90/00685 describes a process using particle sizes of 50 microns. The membrane is considered to be used as oil bearing. EP-A-0 ' 580 ' 134 shows a process using particle sizes of 1 to 3 microns and achieves therefore pore sizes larger than 100 A.
Ceramic membranes having ultra-fine pores are typically formed by so-called "wet processes, n that is, DroceSSeS requiring the use of a solvent. Such processes include slip casting, gel casting, extrusion, and the sol-gel process. The slip casting and gel casting processes utilize large amounts of solvents as well as dispersing agents to form z slurry which is then cast in a mold to form the desired membrane. Extrusion typically involves the addition of a solvent along with die lubricants and an organic polymeric binder to a cera=ic powder to form a mixture which is then extruded to form, typically, tubular membranes. In the sol-gel process, a solution of organo-metallic material is formed and then gelled. The solvent in the gel is then removed alld the re-- i n i n~ structure heat treated .
Each of the slip casting, gel casting, extrusion and sol-gel processes utilize solvents and most of these processes utilize organic additives which must later be A~IJiJ'., ~n~T
Woss/2755~ 2 1 87330 F~l~ o~c7 removed. This greatly limits the minimum size o~ the pores, typically submicron size, which can be formed in the resulting :7LL~I~ LUL~ due to the requirement that the removal of solvents or organics requires that the pore size in the I~LU. LUL2 be larger than the molecules being removed.
In addition, the removal of solvents produces CArillAry stresses in the D~Lu~:LuL~: which increase as the pore size of the structure decreases. To avoid cracks in the submicron pore size D~Lu LUL~8, elaborate and expensive drying schemes are re~uired. When n~nnci~e or AnYDLLI size pores are desired, the problem become8 e-~cDnt;:~lly ;n Lable due to the l L~ ' capillary stresses encountered. See Hsieh, H.P. et al., ~Mi~:LuuuLuus Ceramic Nembranes", Polvmer Journ~l. Volume 23, No. 5, pages 407-415 (1991? which teaches ConvPntinn~1 ceramic forming t~Drhn;5~uDc such as extrusion, ession and injection molding which can be used to produce ceramic membranes with Dy ~ ic DLLLl~iLUIt:S and large pores from particles of well controlled size distributions. See also Chan K. et al., "Ceramic Membranes-Growth FLu~ua. LD and 0,UUUL Lu..ities'', Ceramic Bullet;n, Volume 70, No. 4, (1991) which teaches the use of the sol-gel prûcess for producing membranes having submicron pore sizes; Zievers, J. F. et al., "Porous Ceramic# For Gas Filtration", CerAm;r Bullet;n. Volume 70, No. 1, pages 108-111, (1991) which teaches the use of layered porous ceramic filter elements for gas filtration; and Breck, D. W. et al., "Nolecular Sieves", Scientific American (1959) which teaches ~ v~O95fl7556 2187330 ~crf~Sg~0435l the use of molecular sieves for separating very similar mo l ecul es .
Zeolites are a group of minerals, both naturally occurring and synthetically prepared, whose crystal structures contain pores on the order of about 3 to 20 AnyaLLI ~ in size. However, the preparation of monolithic discs or sheets of material using zeolite with only 3 to 20 Anu,~LLu_ size rnnnPc~p~ pores is not possible because the resulting micron size powder would contain crystals of zeolite which form shapes containing micron size pores with A~ .LL~ size pores within the crystals.
EP-A-0 ~ 426 ' 546 and FR-A-2150390 disclose processes for producing membranes using additives or solvents The membranes achieved by these processes have pores sizes larger than 100 A
SUM~L~RY 0~ ~E IN~rENTION
Accordingly, it is an objection of this invention to provide a process for producing a monolithic structure having An~:,LL, size and nanosize pores.
It is another object of this invention to produce ceramic and/or metal membranes having n;~nnsi 7e and Angstrom-size pores.
It is yet another obj ect of this invention to provide a process for producing ceramic andJor metal membranes which requires no solvents or dispersants which can require elaborate and expensive drying schemes to avoid cracks in the resulting submicron ~L~u-,LuLe:.
It is yet another obj ect of this invention to provide a process for producing ceramic and/or metal membranes which avoids the use of organic additives or solvents which must be removed during the manufacturing -tr Wo ss/27ss6 2 1 8 7 3 3 0 I/L_ _ 'O ~ IC'~
process and, thus, limit the minimum pore ~ize obtainable to the size of the molecules being removed from the final product .
These and other objects of this invention are achieved by a process f or producing a membrane having a plurality of Allg~L size pores comprising the steps of forming a loose powder layer of at least one of a metal powder and a ceramic powder comprising a plurality of subst~ntjAlly all nanometer-size particles and compacting said loose powder layer of said at least one of said metal powder and said ceramic powder to form a con~ol 1~9Ated powder porous membrane. By "subs~An~;Ally all r-- ~r-size particles, " we mean a powder having greater than about 959 nanometer-size particles. A critical feature of this process is the requirement that nanometer-size ceramic powders be utilized. In a preferred '-';- L of the process of this invention, compacting of the nanometer-size particles is carried out by cold-isostatic pressing.
To form membranes having highly uniform nanometer-size pores, it is generally desired that the nanoparticulate powder be relatively uniform in size. In addition, the mean pore size of the membranes produced in accordance with the process of this invention can be controlled based upon the mean particle size of the powder being pressed. That is, the smaller the mean particle size of the powder, the smaller will be the mean pore size of the resulting .e. Membranes ~Luduc~d in accordance with this ~ wossn~ss6 2 ~ ~ 7330 : Pcr~llss~lo~l~7 process have a higher porosity than those produced }~y other known processes for producing membranes, in particular, ceramic membranes.
D~SCRIPTION OF ~ u ~M~ODTlrFNTS
In accordance with a preferred ~hoA;-- ~ of this invention, c.nes having a plurality o~ AnyaL~ ~ size pores are produced by compacting at least one of a metal powder and a ceramic powder comprising substantially all n:-~ t~r-size particles to form ~ roncnl i~Ated porous layer of powder, that is, a cnncol ;A~ted powder porous membrane, the compacting being carried out by cold-isostatic pressing.
To eliminate large pores f rom within the resulting ~L .,~ Lu,æ, that is, pores greater than about three t3) times the particle size employed, compaction ~Le:aa~LæS between abou~(l5,000 psi) and about~,~300,000~si~ are preferred.
"'03 To produce a membrane having uniform pore sizes in accordance with the process of this invention, nanometer size particles having a narrow particle size distribution are desirable. In particular, it is preferred that the metal and/or ceramic powder comprise at least about 98 n;l- ~t~r-Size particles an~ that at least 95% of the nanometer-size particles be less than about 30 nanometers.
In a particularly preferred ~"hoAir L, the particle size of the nanometer-size particles is in the range of about 2 nanometers to about 30 n;~- ' F.rS.
The consolidated powder porous membranes produced in accordance with this process are strong, the particles WOgS/27556 2 l 8 7 3 3 0 r~l" ~c~c7 being bonded ~c a result of cold welding and electrostatic forces. In accordance with another preferred ~ t of this invention, the ~LLt~ Lil of the membrane can be in-;L-ased by fast-firing the ~ nncnl i~l~ted porous layer of powder. However, there are two; L~.l.L heating conditions which must be observed - a low sintering t~ cltULe: and a short hold time. A low sintering t~ cltuLe: minimi7~c the amount of d~ncif;c~tion taking place and, thu5, r-~nt~;rc the large porosity present in the membrane. A short hold time m1n;m;7Ac the amount of particle growth and, thus, reduces the amount of pore growth in the resulting - c-l.e.
For ceramic ~ ' anes, sintering ~ -tuL~s required by the process of this invention are typically a few hundred degrees lower than the temperatures reguired to densify the ceramic. For example, alumina can be _ l~t~ly densiried at 1550-C, but membranes produced in accordance with this process by compacting a ceramic powder comprising n ~r-size particles of alumina may be fired at lOoO-C
to strengthen it. In a preferred: ~ ir L of the process of this invention, the concol;~l~ted porous layer of ceramic material resulting from compaction of the ceramic powder i5 fired at a temperature between about 800-C and about 2000-C.
In accordance with a preferred: ir L of this invention, the hold time for the membrane within the firing process is less than 30 minutes and, preferably less than 5 minutes. CULL~ >~ in~ly~ a heating rate of about 0.5-C/minute to about 2000-C/minute is preferred. Upon Wo95~27~6 2 1`873~0. ` PCr/~159s~ C2 completion of the iring process, the resulting =e~rane is cooled, preferably as quickly as possible without causing da~age to the membrane.
EXA~PLE I
Approximately 4 grams of nanoparticulate 8 =ol percent Y2 O3-doped ZrO2 (YSZ) powder having a mean diameter of about 20 nanometers was die-pressed to form a disc of about~,(2 . 25"~ in ~ or, The ceramic disc was then cold-S7 rn~
isostatically pres5ed a~(55, 000 psi~. Pore-size distribution 3,~ Io8 ~
analysis of the pressed YSZ disc indicated that it was about 50S porous with a uniform distribution of pores. The mean pore radius of th~ membrane was det~rm;n~ to be about 27 An ~:.LL~ . In a gas separation test, the membrane prepared in accordance with this example was found to be effective in the separation of an H2/C02 gas mixture. The membrane was found to be at least four times more F -~hl e to H2 than to CO2 .
It will be apparent to those skilled in the art that different membrane shapes can be formed in accordance with the process of this invention including discs and tubes .
To improve the r~ n;c~ Le~l~Lh~ the membranes can be heat treated by fast-firing to preserve the uniformity of the pore size distribution. ~embranes produced in accordance with the process of this invention have a porosity of about 30% to 55%, that is, a~out 30% to about 55% porous. The mean pore radius of the membranes wo ss/~7ss6 2 1 8 7 3 3 ~ PCrlU59s/043s~
'~
produced in accordance with the process of thi6 invention i6 between about V5 to V20 of the mean particle diameter of the powder used. In other words, if a powder with a mean particle diameter of 10 n~- ~r~6 is used, a membrane with a mean pore radius of about 5 AnyaLL~ - will be obtained.
If ~ ,l,le support or multilayers of r- '_I~es are desired, powders of different particulate size can be pressed together to form r ' c~ne layers of different mean pore sizes. In particular, in accordance with one of the process of this invention for producing ~ultilayer membranes, the loose powder layer of nAr te~-size particles of metal powder and/or ceramic powder is rormed on a coarse particle layer of metal and/or ceramic powder particles where the coarse particle layer comprises a plurality of particles, aul/a~ Lially all larger than n~- tr~r-size. In accordance with one I ';--nt of the process of this invention, the loose powder layer and the coarse particle layer are simult~nQollcly compacted together, forming a multilayer c~7ncol ir~ted powder porous I,e, In accordance with another: -'i- L of the process of this invention, the coarse particle layer is compacted and the loose powder layer is formed on the compacted coarse particle layer and s~lh6r-~r~r~ntly compacted onto the compacted coarse particle layer to form a multilayer ~ nncol ~ ted powder porous membrane.
wo ssn7ss6 2 1 8 7 3 3 0 PCI/llS9~s/11~35i ~
EXi~PLE I I
This example demonstrates a method for makiny a ceramic membrane having a two-layer structure.
Approximately 4 grams of submicron size 8 mol percent Yz03-doped ZrO2 (YSZ) powder having a mean 1'9iA ' -r of about 0 . 3 microns were die-pressed to form a disc of ;,(2.25") in diameter. Before removal of the YSZ disc from the s~in1~cs steel die, approximately 0.2 g of nanoparticluate Al203 powder having a mean diameter of about lO nanometers were spread evenly on the top surface of the YSZ disc, and die-pressed once again to form a two-layer porous ~LLU~_~U' ~.
The two-layer ceramic structure was them cold-isostatically pressed at~ 58,000 psi~. Accordingly, the YSZ powder, in this /o8~
case, was used as the supporting :7LLuL~LuL~= for the thin Al203 membrane.
In a gas separation test, the membrzne prep2red in this example was found to be effective in the separation of H2/C02 mixture. The membrane was found to be at least four times more p~ ~hle to X2 than to C02. The gas transfusing rate across the membrane was ~ign;f;c:lntly Pnh~nl-~d in the two-layer membrane structure compared to that of Example I.
~ hile in the f oregoing specif ication this invention has been described in relation to certain preferred ~ LS thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional ~mho~l;r LS and that certain of 11 A'1~',L;~ .r, ~J
wo ss/27ss6 2 1 8 7 3 3 ~ Q4~C~
the details described herein can be varied c~n~ rably without departing from the basic prinl-;pl~ of the invention.
Claims (14)
1. A process for producing a porous structure having pore sizes substantially in the range of about 1 Angstrom to about 90 Angstrom comprising the steps of:
forming a loose powder layer, free of solvents or additives, of at least one of a metal powder and a ceramic powder having particle sizes, at least 95% of which are less than about 30 nanometers; and compacting the loose powder layer, forming a consolidated powder porous structure having a porosity in the range of about 30% to 55%.
forming a loose powder layer, free of solvents or additives, of at least one of a metal powder and a ceramic powder having particle sizes, at least 95% of which are less than about 30 nanometers; and compacting the loose powder layer, forming a consolidated powder porous structure having a porosity in the range of about 30% to 55%.
2. A process in accordance with Claim 1, wherein said loose powder layer is compacted by cold-isostatic pressing.
3. A process in accordance with Claim 1, wherein said consolidated powder porous structure is fired at a heating rate between about 0.5°C/minute and about 2000°C/minute.
4. A process in accordance with Claim 3, wherein said consolidated powder porous structure is fired at a temperature between about 800°C and about 2000°C.
5. A process in accordance with Claim 1, wherein said at least one of said metal powder and said ceramic powder comprises particles having sizes, at least about 98% of which are less than about 30 nanometers.
6. A process in accordance with Claim 1, wherein said compaction pressure is between 1,03 105 Pa (15,000 psi) and 20,68 108 Pa (300,000 psi).
7. A process in accordance with Claim 6, wherein said compaction pressure is between 2,06 108 Pa (30,000 psi) and 10,34 108 Pa (150,000 psi) .
8. A process in accordance with Claim 1, wherein the particle size is in the range of about 2 nanometers to about 30 nanometers.
9. A process in accordance with Claim 1, wherein the pore sizes of said consolidated powder porous structure are in the range of 1 Angstrom to three times the largest of said particles.
10. A process in accordance with Claim 1, wherein said loose powder layer of said at least one of said metal powder and said ceramic powder is formed on a coarse particle layer of said at least one of said metal powder and said ceramic powder, said coarse particle layer comprising a plurality of particles larger than 30 nanometers.
11. A process in accordance with Claim 10, wherein said loose powder layer and said coarse particle layer are simultaneously compacted together, forming a multilayer said consolidated powder porous structure.
12. A process in accordance with Claim 11, wherein said coarse particle layer is compacted prior to forming of said loose powder layer and said loose powder layer is compacted onto said coarse particle layer, forming a multilayer said consolidated powder porous structure.
13. Porous structure in accordance with one of the claims 1 -12, wherein it consists of at least one of a metal powder and a ceramic powder and wherein the pore sizes of the structure are in the range of 1 Angstrom to 90 Angstrom and wherein the powder porous structure has a porosity in the range of 30 percent to 55 percent.
14. Use of a porous structure according to claim 15 as a membrane.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22525694A | 1994-04-07 | 1994-04-07 | |
| US225,256 | 1994-04-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2187330A1 true CA2187330A1 (en) | 1995-10-19 |
Family
ID=22844180
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002187330A Abandoned CA2187330A1 (en) | 1994-04-07 | 1995-04-07 | Process for producing membranes from nanoparticulate powders |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU2381195A (en) |
| CA (1) | CA2187330A1 (en) |
| WO (1) | WO1995027556A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9612215D0 (en) * | 1996-06-11 | 1996-08-14 | British Nuclear Fuels Plc | Manufacture of articles |
| BE1011287A3 (en) * | 1997-07-18 | 1999-07-06 | Bekaert Sa Nv | BEER FILTER. |
| DE19738376A1 (en) * | 1997-09-03 | 1999-03-04 | Mann & Hummel Filter | Filter element |
| MX250079B (en) | 1999-06-11 | 2007-10-08 | Gas Separation Technology Inc | Porous gas permeable material for gas separation. |
| EP1569790A4 (en) * | 2002-12-12 | 2006-09-20 | Entegris Inc | Porous sintered composite materials |
| RU2518809C2 (en) * | 2012-03-29 | 2014-06-10 | Государственное бюджетное образовательное учреждение высшего профессионального образования "Самарский государственный медицинский университет" Министерства здравоохранения Российской Федерации | Method of producing high-porosity materials |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE787964A (en) * | 1971-08-24 | 1973-02-26 | Montedison Spa | PROCESS FOR PREPARING POROUS COMPOSITE MEMBRANES OR BARRIERS FOR GAS DIFFUSION SYSTEMS |
| US4329157A (en) * | 1978-05-16 | 1982-05-11 | Monsanto Company | Inorganic anisotropic hollow fibers |
| DE3822919C2 (en) * | 1988-07-06 | 1997-06-19 | Interelectric Ag | Shaft slide bearing unit |
| JPH03143535A (en) * | 1989-10-26 | 1991-06-19 | Toto Ltd | Asymmetric ceramic film and production thereof |
| US5104546A (en) * | 1990-07-03 | 1992-04-14 | Aluminum Company Of America | Pyrogens separations by ceramic ultrafiltration |
| JP3324658B2 (en) * | 1992-07-21 | 2002-09-17 | 東芝タンガロイ株式会社 | Sintered alloy having fine pores and method for producing the same |
| US5364586A (en) * | 1993-08-17 | 1994-11-15 | Ultram International L.L.C. | Process for the production of porous membranes |
-
1995
- 1995-04-07 WO PCT/US1995/004352 patent/WO1995027556A1/en active Application Filing
- 1995-04-07 AU AU23811/95A patent/AU2381195A/en not_active Abandoned
- 1995-04-07 CA CA002187330A patent/CA2187330A1/en not_active Abandoned
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| WO1995027556A1 (en) | 1995-10-19 |
| AU2381195A (en) | 1995-10-30 |
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