Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1995-03-08
1996-09-10
Phasge, Arun S.
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204483, 204489, 204490, 204491, 204507, 204509, C25D 1302
Patent
active
055542719
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of manufacturing a composite material and is particularly concerned with a method of manufacturing a composite material using electrophoresis.
It is well known that certain characteristics of some materials can be enhanced by reinforcing those materials with a suitably configured structure formed from a different material. In a typical example, the strength characteristics of one material can be enhanced by reinforcing that material with a different suitably strong material.
In the field of ceramics it is frequently desirable to reinforce a ceramic matrix material with high strength fibres of, for instance, alumina or silicon carbide. Difficulties arise, however, in ensuring that the reinforcing fibres are completely infiltrated by the ceramic matrix material.
One method of infiltrating reinforcing fibres with a ceramic matrix material is by the use of chemical vapour infiltration. In that technique, the fibres are placed in an atmosphere of a suitable vapour which is caused to chemically break down to deposit a ceramic material on the fibres. Ceramics such as silicon carbide can be deposited in this way. However it is a slow process which is expensive to carry out. In addition, it does have a tendency to produce a matrix material which has some degree of undesirable porosity.
Another technique is one which utilises liquid phase reaction. This involves infiltrating the reinforcing fibres with a liquid which progressively oxidises or reacts with a gaseous medium to form a ceramic matrix material. For instance, the fibres could be infiltrated by molten aluminium which is caused to oxidise to alumina as it infiltrates.
The drawback with this technique is that there is only a small range of materials which are suitable for use with it. Additionally there is the danger that unreacted metal could be left in the matrix material and the matrix material does tend to exhibit a certain degree of porosity.
A still further technique is one in which the reinforcing fibres are infiltrated with a liquid glass precursor material which is subsequently crystalised to form a ceramic product.
The difficulty with this technique is that of the limited range of glass precursor materials which are available.
It is an object of the present invention to provide a method of manufacturing a composite material in which such difficulties are substantially avoided.
According to the present invention, a method of manufacturing a composite material comprises the steps of immersing an electrically conductive or semi-conductive porous reinforcing medium in a ceramic sol, each of said sol particles carrying a surface charge but not having a polymer coating thereon, applying a potential difference between said porous reinforcing medium and a further electrode in said sol sufficient to cause said sol particles to migrate through said suspension and be deposited upon said porous reinforcing medium, the application of said potential difference being continued until said porous reinforcing medium has been substantially completely permeated by said sol particles, discontinuing said applied potential difference, taking steps to ensure that said permeating sol particles remain in position within said porous medium after the discontinuation of said potential difference, removing said permeated porous medium from said sol subsequently sintering said permeating sol particles within said porous reinforcing medium.
The method of the present invention is directed towards the production of a composite material which comprises reinforcing fibres embedded in a matrix of a ceramic material.
Throughout this specification, the term "ceramic" is intended to include vitreous products as well as crystalline and semi-crystalline products and should be construed accordingly.
The fibres are initially arranged in the particular configuration which is desired in the final composite material. One convenient way of achieving this is to weave the fibres in the desired configuration. However, it will be appreciated that other measures coul
REFERENCES:
patent: 4923578 (1990-05-01), Benton et al.
patent: 5211822 (1993-05-01), Alary et al.
Corden et al., "Oxidation and Wear resistant carbon--carbon composites." (1991) (no month).
Gal--Or et al., "Coating and Impregnation of carbon-carbon composites with ceramics by elechophoretiz deposition" (1989) no month.
Butler Edwin G.
Doleman Paul A.
Gilbert Mark J.
Illston Trevor J.
Marquis Peter M.
Phasge Arun S,.
Rolls-Royce plc
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