High performance filters comprising an inorganic composite substrate and inorganic fiber whiskers

• US 6,264,045 B1
• Filed: 05/29/1998
• Issued: 07/24/2001
• Est. Priority Date: 06/02/1997
• Status: Expired due to Term

• Current Assignee: HITCO Carbon Composites, Inc. (Sgl Carbon Se)
• Original Assignee: HITCO Carbon Composites, Inc. (Sgl Carbon Se)
• Inventors: Wilson, Doug, Mathur, Raj
• Primary Examiner(s): Walker, W. L.
• Assistant Examiner(s): FLEMING, MICHAEL A
• Application Number:
  US09/087,404
• Time in Patent Office: 1,152 Days
• Field of Search: 210/500.23, 210/491, 210/500.25, 210/500.26, 210/500.27, 210/502.1, 210/503, 210/505, 428/408, 428/306.6, 428/307.3, 428/312.2, 428/312.6, 428/317.9, 428/318.4, 428/319.1, 428/698, 428/446, 501/94, 501/95.1, 501/95.2, 501/95.3, 501/96, 501/97, 501/87, 501/88, 501/90, 502/224, 502/229, 502/326, 502/527.12
• US Class Current: 210/491
• CPC Class Codes: B01D 2239/0471 Surface coating material
• CPC Class Codes: B01D 2239/0485 on particles
• CPC Class Codes: B01D 2239/0609 Knitted
• CPC Class Codes: B01D 2239/0613 Woven
• CPC Class Codes: B01D 2239/0636 Two or more types of fibres present in the filter material
• CPC Class Codes: B01D 2239/064 The fibres being mixed
• CPC Class Codes: B01D 2239/065 More than one layer present in the filtering material
• CPC Class Codes: B01D 2239/0695 Wound layers
• CPC Class Codes: B01D 2239/10 Filtering material manufacturing
• CPC Class Codes: B01D 2239/1208 Porosity
• CPC Class Codes: B01D 2239/1216 Pore size
• CPC Class Codes: B01D 2239/1225 Fibre length
• CPC Class Codes: B01D 2239/1233 Fibre diameter
• CPC Class Codes: B01D 39/2017 the material being filamentary or fibrous
• CPC Class Codes: B01D 39/2055 Carbonaceous material solid sorbent compositions comprising free carbon B01J20/20
• CPC Class Codes: B01D 39/2065 the material being fibrous
• CPC Class Codes: B01D 39/2082 the material being filamentary or fibrous
• CPC Class Codes: C04B 14/46 Rock wool ; Ceramic or silicate fibres C04B14/40, C04B14/42 take precedence
• CPC Class Codes: C04B 2111/00793 as filters or diaphragms
• CPC Class Codes: C04B 2235/614 Gas infiltration of green bodies or pre-forms
• CPC Class Codes: C04B 2235/616 : Liquid infiltration of green bodies or pre-forms
• CPC Class Codes: C04B 2235/94 : Products characterised by their shape
• CPC Class Codes: C04B 30/02 : containing fibrous materials
• CPC Class Codes: C04B 35/14 : based on silica
• CPC Class Codes: C04B 35/80 : Fibres, filaments, whiskers, platelets, or the like
• CPC Class Codes: C04B 35/806 : The matrix of the ceramic products consisting of non-oxides only
• CPC Class Codes: C04B 35/83 : Carbon fibres in a carbon matrix
• CPC Class Codes: C04B 38/00 : Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof treating slag with gases or gas generating material C04B5/06 ; expanded graphite C04B35/536
• CPC Class Codes: C04B 41/009 : characterised by the material treated
• CPC Class Codes: C04B 41/4529 : applied from the gas phase
• CPC Class Codes: C04B 41/455 : the coating or impregnating process including a chemical conversion or reaction
• CPC Class Codes: C04B 41/4596 : with fibrous materials or whiskers
• CPC Class Codes: C04B 41/5001 : with carbon or carbonisable materials
• CPC Class Codes: C04B 41/5053 : non-oxide ceramics carbon or carbonisable materials C04B41/5001
• CPC Class Codes: C04B 41/5144 : with a composition mainly composed of one or more of the metals of the iron group
• CPC Class Codes: C04B 41/81 : Coating or impregnation
• CPC Class Codes: Y10T 428/249955 : Void-containing component partially impregnated with adjacent component
• CPC Class Codes: Y10T 428/249956 : Void-containing component is inorganic
• CPC Class Codes: Y10T 428/249967 : Inorganic matrix in void-containing component
• CPC Class Codes: Y10T 428/249969 : Of silicon-containing material [e.g., glass, etc.]
• CPC Class Codes: Y10T 428/249986 : Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/249987 : With nonvoid component of specified composition
• CPC Class Codes: Y10T 428/24999 : Inorganic
• CPC Class Codes: Y10T 428/30 : Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A filter media system, which is capable of operating in the microfiltration regime, offers: low cost, durability, high temperature and chemical resistance, no particulation, mechanical strength, separation efficiency, and biocompatibility. A filter media system is comprised of a carbon or ceramic composite substrate which contains a carbon or ceramic matrix reinforced with carbon or ceramic fibers. The composite has an array of carbon or ceramic fiber whiskers grown onto its surface or in its bulk. A process is provided for manufacturing the filter media system wherein a carbon fiber is disposed in a matrix deposited by a CVI or LPI process, at temperatures of about 900 to about 1200° C. to achieve a weight gain of about 10 to 200% (the ceramic matrix is deposited by a CVI process from an aqueous slurry or by use of a preceramic polymer). This composite is treated with an aqueous solution of metal catalyst salt and is then heated in hydrogen at elevated temperatures to reduce the metal salt to metal. Whiskers are then grown on the surface or in the bulk of the catalyst deposited composite such as by decomposition of methane gas using metal catalyzed chemical vapor deposition (CVD).

Claims

1. A process for manufacturing a filter media system comprising a carbon composite substrate which comprises a carbon matrix reinforced with carbon fibers, wherein an array of carbon fiber whiskers have been grown onto said substrate, comprising:

a) providing the carbon fiber reinforcement;

b) depositing the carbon matrix by one of chemical vapor infiltration (CVI) and liquid pressure infiltration (LPI) process at temperatures of about 900 to about 1200°

C. in order to achieve a weight gain of about 10 to about 200%;

c) treating the composite with a solution of metal catalyst salt;

d) heating the composite in hydrogen at elevated temperatures to reduce the metal salt to metal; and

e) initiating whisker growth on at least one of the surface and the bulk of the metal deposited composite by decomposition of low molecular weight hydrocarbon gas at elevated temperature; and

wherein the filter media system has an interconnected porosity that is adapted to allow fluid to flow through the filter media system, and a pore size distribution that is adapted to capture particles having a diameter in the range of about 0.1 to about 100 microns.

2. The process in claim 1 wherein the solution of metal catalyst salt is selected from the group consisting of nickel chloride and ferric chloride.

3. The process in claim 1 wherein the whisker growth is initiated on the surface of the catalyst deposited composite by decomposition of a gas selected from the group consisting of ethane, methane, and propane.

4. The process of claim 1 wherein the fiber whiskers are grown on the composite surface using metal catalyzed chemical vapor deposition (CVD).

5. A process for manufacturing a filter media system comprising a ceramic composite substrate which comprises a ceramic matrix reinforced with ceramic fibers, wherein an array of ceramic fiber whiskers have been grown onto said substrate, comprising:

a) densifying the ceramic fiber with a precursor in order to deposit a ceramic matrix to produce a composite;

b) treating the composite with a solution of metal catalyst salt;

c) heating the composite in hydrogen at elevated temperatures to reduce the metal salt to metal; and

d) initiating whisker growth on at least one of the surface and the bulk of the metal coated composite by subjecting the composite to a whisker precursor; and

wherein the filter media system has an interconnected porosity that is adapted to allow fluid to flow through the filter media system, and a pore size distribution that is adapted to capture particles having a diameter in the range of about 0.1 to about 100 microns.

6. The process of claim 5 wherein the precursor is selected from the group consisting of methylchlorosilane, alkylchlorosilane, polycarbosilane, and polycarbosilazane.

7. The process of claim 5 wherein the ceramic matrix is selected from the group consisting of silicon carbide and silicon nitride.

8. The process of claim 5 wherein the ceramic fibers are selected from the group consisting of silicon carbide, silicon nitride, aluminosilicate, silica, glass, and mixtures thereof.

9. The process of claim 5 wherein the fiber whiskers are selected from the group consisting of carbon, silicon carbide, silicon nitride, titanium carbide, titanium nitride, and mixtures thereof.