WO2007088484A1 - Moulage par injection de matériau céramique - Google Patents

Moulage par injection de matériau céramique Download PDF

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Publication number
WO2007088484A1
WO2007088484A1 PCT/IB2007/000271 IB2007000271W WO2007088484A1 WO 2007088484 A1 WO2007088484 A1 WO 2007088484A1 IB 2007000271 W IB2007000271 W IB 2007000271W WO 2007088484 A1 WO2007088484 A1 WO 2007088484A1
Authority
WO
WIPO (PCT)
Prior art keywords
article
particulate material
fuel cell
tubes
flow path
Prior art date
Application number
PCT/IB2007/000271
Other languages
English (en)
Inventor
Pieter Wouter Du Toit
Original Assignee
Pieter Wouter Du Toit
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Pieter Wouter Du Toit filed Critical Pieter Wouter Du Toit
Publication of WO2007088484A1 publication Critical patent/WO2007088484A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/24—Producing shaped prefabricated articles from the material by injection moulding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H01M4/8882—Heat treatment, e.g. drying, baking
    • H01M4/8885—Sintering or firing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • THIS INVENTION relates to moulding of ceramic materials to manufacture tubes for fuel cells and other thin-walled articles.
  • Ceramic materials are generally manufactured by preparing a slurry of a ceramic powder, water and bonding agent, drying the slurry to form a composition comprising coated ceramic particles, shaping the coated ceramic particles to form a so-called "green” article, and exposing the green article to heat or "firing" it firstly to remove the bonding agent and secondly to form a ceramic body by sintering the ceramic particles.
  • This invention relates to the step of shaping the composition of coated ceramic particles.
  • compositions vary and, depending on their consistency, the compositions can be shaped in a variety of ways, e.g. by casting or extruding when the compositions are fluid, or machining compositions that are more substantial.
  • moulding fluid ceramic compositions can present difficulties, since the these compositions are usually shear-thickening or dilitant, i.e. the viscosity of the fluids increase with an increase in shear, typically due to the interaction of the ceramic powder particles in the mixture, with one another.
  • Articles with relatively thick walls and small dimensions can be moulded at relatively low pressures, but in the case of articles such as tubes for fuel cells, that have very thin walls and large dimensions, the pressures required to cause ceramic fluid compositions to flow into moulds for these articles causes shear forces in the fluid to become too high, so that the flow gets blocked as a result of the dilitant effect.
  • Fuel cell tubes are consequently not made by injection moulding, but are instead extruded and in the event that the ends of the tubes need to be closed, this is done by fixing plugs to the ends of the tubes while green or after they have been fired.
  • These fuel cell tubes have a number of shortfalls in that the attachment of the ends to the elongate walls is never as strong as the walls themselves, variations in the shape of the extruded walls occur, since the shape and dimensions cannot be accurately controlled in an extrusion process and the manufacturing processes are time consuming and expensive.
  • the object of the present invention is to provide for cost effective manufacture of thin walled ceramic articles.
  • a method of manufacturing an article from particulate material comprising injecting particulate material through an injection flow path into a mould cavity under low pressure and using a piston to apply the pressure to the particulate material in the flow path, wherein the dimensions of the flow path are large enough and the pressure in the particulate material is low enough to avoid excessive shear within the particulate material in the flow path.
  • the shear in the particulate material in the flow path should preferably be low enough to avoid significant flow restriction in the particulate material as a result of the dilitant effect.
  • the particulate material may be ceramic material and/or may be powdered metal.
  • the article may be thin-walled.
  • an article is regarded as thin walled if the thickness of material that constitute the article is less than 4mm and is less than one tenth of the largest dimension of the article, i.e. the article has an aspect ratio between its length and its wall thickness of 10:1.
  • the piston may define a face that forms part of the bounding wall of the mould cavity, when the ceramic and or powdered metal, i.e. the particulate material, has been injected into the mould cavity.
  • the invention extends to an article made in accordance with the method as described herein above and the article may be a tube, such as a fuel cell tube.
  • tube refers to a hollow, elongate article with any cross-sectional profile, whether round, square, oval, tapered, or any other desired shape.
  • the tube may include a closed end wall that is formed integrally with the walls of the tube in a single step, may define a thread in a neck region of the tube near one of its ends and/or may include at least one longitudinal rib.
  • the article may be a manifold or matrix for a fuel cell, comprising ceramic and/or metal powder, i.e. particulate material, wherein the tubes as described herein above may fit.
  • the article may be a housing for a fuel cell, comprising ceramic and/or metal powder, the housing defining elongate recesses into which fuel cell tubes are receivable with clearance.
  • the article may comprise a manifold for a fuel cell and fuel cell tubes, the manifold and fuel cell tubes being integrally formed of particulate material in a single step.
  • At least some of the fuel cell tubes of the article may have closed end walls that are formed integrally with the walls of the tubes, in a single step.
  • the porosity of any article made in accordance with the method described above may depend on the particle sizes of the ceramic and/or metal particles and/or on the combination of ceramic or metal particles used.
  • Figure 1 is a sectional view through a mould in accordance with the present invention.
  • Figure 2 is a sectional view of part of a fuel cell in accordance with a first embodiment of the present invention.
  • Figure is a sectional view of part of a fuel cell in accordance with a second embodiment of the present invention.
  • a mould for a fuel cell tube in accordance with the present invention is generally indicated by reference numeral 10 and a fuel cell tube in accordance with the invention is generally indicated by reference numeral 12.
  • a mould 10 is provided for making a thin walled ceramic article in the form of a fuel cell tube 12.
  • the mould 10 can comprise as many components as are required to form a mould cavity 14 that is shaped complemental to the fuel cell tube 12, e.g. the mould can include an outer body and one or more inner cores 18.
  • the fuel cell tube 12 has an elongate shape and in a preferred embodiment, a longitudinal rib 20 extends centrally along the inside of the tube, thus dividing the internal cavity 22 of the tube lengthwise.
  • the one end of the tube 12 is closed by an end wall 24 that can have any shape and near the other end of the tube, a thread 26 is defined in the outer circumference of the tube, in a neck region, which can be screwed into a structure of the fuel cell, such as a manifold or matrix 36, which can also be moulded in a method according to the present invention.
  • the length of the tube 12 is typically of the order of 200 mm to 2000 mm and the thickness of the walls 28 of the tube is typically about 1 mm to 4 mm.
  • the mould 10 further defines, a wide injection flow passage 30 extending into, i.e. being continuous with the mould cavity 14 and in a preferred embodiment of the invention, a piston 32 is configured to urge material from the flow passage into the mould cavity, the face 34 of the piston forming part of the inner bounding wall of the mould cavity, defining the shape of the mould cavity, when the piston reaches the forward end of its stroke, as shown in Figure 1.
  • the fuel cell tube 12 is manufactured by preparing a slurry including a suitable ceramic powder, water, a suitable bonding agent and other ingredients, if preferred.
  • the slurry is dried to form a composition of coated ceramic particles, which is heated to form a fluid composition of particulate material.
  • the mould 10 is closed and the piston 32 is withdrawn.
  • the hot, fluid ceramic composition of particulate material is fed into the mould cavity 14 under low pressure and the piston 32 is displaced forward to urge the composition into the mould under low pressure, until the piston has reached its forward position.
  • the dimensions of the flow passage 30 are large enough and the pressure applied by the piston 32 to the . particulate ceramic material in the flow passage is low enough to avoid excessive shear in the ceramic material within the flow passage.
  • the amount of ceramic material that the piston displaces should preferably be just enough to fill the mould cavity 14 when the piston 32 reaches the forward end of its stroke and forms part of the bounding wall of the cavity.
  • the particulate ceramic composition is allowed to cool and set and the mould 10 is opened to remove the green fuel cell tube 12, which is then fired.
  • the cross sectional dimensions of the injection flow passage are small and material is allowed to set in the flow passage. This would not work for moulding ceramic materials as the pressure required to push the ceramic material through the flow passage would be too high.
  • the flow passage cannot simply be scaled-up, to reduce the required supply pressure, as this would result in large protuberances of ceramic material that have set in the flow passages, extending from the moulded articles, that have to be removed.
  • the end walls 24 of the tubes 12 of the present invention are integrally formed with the side walls 28 of the tube itself, so there is no zone of structural weakness as there is where end walls are attached to extruded fuel cell tubes.
  • the end walls 24 of fuel cell tubes 12 offer the advantage of increasing the area where the chemical reaction of the fuel cell can take place. Further, fuel cell tubes tend to be long and slender and should preferably be perfectly straight for optimum operation of the fuel cells.
  • the end walls 24 provide structural strength to the outer walls 28, acting in a fashion similar to a bulkhead by preventing, or at least inhibiting deformation of the outer walls near the end walls. In the present invention, the end walls 24 are already present in the green fuel cell tubes 12 when they are released from the moulds 10 and can already perform this structural function, unlike in extruded fuel cell tubes, where the extruded ends of the tubes are unsupported until the end walls have been fitted.
  • the shape of a fuel cell tube 12 in accordance with the present invention is kept bound within the mould cavity 14 until it has set and there is therefore no chance of deformation while it sets, unlike in extrusion where deformation can occur where the extruded material can deform while it sets, immediately after leaving the extrusion die. This ensures that fuel cell tubes 12 made in accordance with the present invention have straighter walls 28.
  • components for a fuel cell are made in accordance with the present invention in moulds similar to that described above, but the fuel cell tubes 12 are integrally formed in a single injection moulding operation with its manifold (matrix) 36.
  • the fuel cell tubes 12 are generally identical to those described above, but their bottom walls 24 are rounded and instead of having screw threads, they are part of a continuous or integral body of moulded ceramic material, including the tubes and the manifold 36.
  • the fuel cell further includes a housing 38 which defines recesses 40 into which the tubes 12 are receivable with clearance.
  • the housing 38 is also made in an injection moulding method as described above.
  • any of the articles made in accordance with the invention can be made of other particulate material than ceramics materials, e.g. an article can be made of particulate or powdered metal.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Sustainable Energy (AREA)
  • Sustainable Development (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Fuel Cell (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un article (12,36) à partir de matière particulaire, en particulier d'articles de type tubes (12) et autres composants (36) pour piles à combustible. Le procédé de l'invention consiste à injecter de la matière particulaire à travers un canal d'écoulement d'injection (30) dans une cavité de moule (14) à basse pression et au moyen d'un piston (32) afin d'appliquer la pression sur la matière particulaire dans le canal d'écoulement (30). Les dimensions du canal d'écoulement (30) sont suffisamment grandes et la pression dans la matière particulaire est suffisamment basse pour éviter que des forces de cisaillement trop fortes ne soient exercées à l'intérieur de la matière particulaire dans le canal d'écoulement (30), ce qui permet d'éviter des limitations d'écoulement provoquées par l'effet de dilatation. L'invention s'étend à des articles (12,36) obtenu selon ledit procédé.
PCT/IB2007/000271 2006-02-03 2007-02-05 Moulage par injection de matériau céramique WO2007088484A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US76477206P 2006-02-03 2006-02-03
US60/764,772 2006-02-03

Publications (1)

Publication Number Publication Date
WO2007088484A1 true WO2007088484A1 (fr) 2007-08-09

Family

ID=38180141

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2007/000271 WO2007088484A1 (fr) 2006-02-03 2007-02-05 Moulage par injection de matériau céramique

Country Status (1)

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WO (1) WO2007088484A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3218377A (en) * 1961-05-26 1965-11-16 Eternit Sa Method and means for molding an aqueous fibrous mixture
US3999923A (en) * 1974-02-23 1976-12-28 Klockner-Werke Ag Injection-molding apparatus
WO1999054947A2 (fr) * 1998-04-09 1999-10-28 Siemens Westinghouse Power Corporation Tubes pour piles a combustible et procede de fabrication desdits tubes
WO1999054949A2 (fr) * 1998-04-09 1999-10-28 Siemens Westinghouse Power Corporation Procede de fabrication de tubes en ceramique a extremite fermee pour piles a combustible

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3218377A (en) * 1961-05-26 1965-11-16 Eternit Sa Method and means for molding an aqueous fibrous mixture
US3999923A (en) * 1974-02-23 1976-12-28 Klockner-Werke Ag Injection-molding apparatus
WO1999054947A2 (fr) * 1998-04-09 1999-10-28 Siemens Westinghouse Power Corporation Tubes pour piles a combustible et procede de fabrication desdits tubes
WO1999054949A2 (fr) * 1998-04-09 1999-10-28 Siemens Westinghouse Power Corporation Procede de fabrication de tubes en ceramique a extremite fermee pour piles a combustible

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