Compositions: ceramic – Ceramic compositions – Refractory
Patent
1988-06-10
1989-12-19
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Refractory
106 84, 106 85, 1062862, 1062865, 423328, 423329, 4273977, 428372, 428375, 428384, 428388, 428396, 428698, 428699, 428701, 428702, 428902, 501153, 501154, C04B 3584, C04B 3516
Patent
active
048883115
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the description and fabrication of composite, temperature-resistant materials based on fibrous ceramics, whose ceramic matrix is a geopolymeric alumino-silicate compound resulting from an inorganic polycondensation reaction of reaction mixtures based on alkaline and/or alkaline earth silico-aluminates.
The principal object of this invention is the description of the various composite ceramic-ceramic materials, whose matrix is a geopolymeric alkaline and/or alkaline earth silico-aluminate compound. The second object of this invention is to describe the processes for obtaining these composite ceramic-ceramic materials. The polycondensation of the ceramic matrix is of the hydrothermal type. It is carried out at a temperature between 20.degree. C. and 120.degree. C. and is similar to that by which minerals such as synthetic zeolites or feldspars, or geopolymers of the type poly(sialate) or poly(sialate-siloxo) are obtained.
In the description of this invention, the term `composite material` designates a material composed of 2 or several constituents in intimate contact on a microscopic scale. In the case of composite materials with organic matrices, which are the most well-known, the constituents are: its properties of strength and mechanical rigidity on the finished composite material. to set in the desired shape while the stresses are transmitted to the fibres.
In this invention, the fibrous reinforcement is composed of fibrous ceramics. The plastic material referred to in point (2) is a thermosetting geopolymer and the matrix so obtained is of the ceramic type.
The notion of a ceramic-ceramic composite is defined in the work by R. Naslain, `Introduction to Composite Materials`, Editions du CNRS, Paris, 1985. In chapter XVIII of this work are described the various technologies used by workers in this field to carry out impregnation into the bulk of the fibrous material of the ceramic matrix. Three procedures are known: by gas, by liquid or by solid. These methods of impregnation all have in common the requirement of extremely high temperatures accompanied by techniques for avoiding the destruction at these temperatures of the fibrous reinforcement. Liquid impregnation of a vitro-ceramic silicoaluminous matrix is generally carried out in four stages: (1) preparation of a preimpregnate using slip, (2) making a composite preform, (3) compression between 6-10 MPa at high temperature 1200.degree.-1500 C. under controlled atmosphere, 4)ceramisation by curing at 900.degree.-1000*.degree. C. This technique is analogous to that used for composite materials based on an organic matrix, with, however, an essential difference in the process temperature, 100.degree.-250.degree. C. for organics compared with 1000.degree.-1500.degree. C. for ceramics.
In contrast, the ceramic-ceramic composites of this invention are characterized by their ease of production at low temperature, their resistance to temperature and their mechanical strengths. These three qualities have up to now been irreconcilable. The ease of production could be found in organic plastic materials; resistance to temperature was the characteristic property of ceramics; mechanical strength could be obtained with composite materials. The composite materials of this invention reconcile these three properties. They can be transformed at low temperatures, between 20.degree. C. and 120.degree. C. with the same technologies as for organic plastics, remain stable up to 1200.degree.-1400.degree. C., and the presence of high-performance ceramic fibres confers on them excellent mechanical properties over a very wide temperature range.
Another object of the invention is the description of manufacturing processes of several articles using the composite ceramic-ceramic material of the invention, in particular the making of small tooling and of items used in the casting of non-ferrous metals.
The ceramic matrix belongs to the geopolymer class of materials. French Pat. Nos. FR 2.464.227, FR 2.489.290, FR 2.489.291 and their European equivalents EP 26.
REFERENCES:
patent: 4284664 (1981-08-01), Ravich, Sr.
patent: 4349386 (1982-09-01), Davidovits
patent: 4472199 (1984-09-01), Davidovits
patent: 4509985 (1985-09-01), Davidovits et al.
Davidovits, "Geopolymers II-Processing and Applications of Ultra High Temperature, Inorganic Matrix Resin for Cast Composite Structures, Molds and Tools for RP/C and Metal Industries, Stable Up to 2100.degree. F.", PACTEC '83, Annual Pacific Technical Conference, Society of Plastic Engineers, Inc., 1983, pp. 222-230.
Davidovits, "Synthesis of New High Temperature Geo-Polymers for Reinforced Plastics/Composites", PACTEC '79, 4th Annual Pacific Technical Conference and Technical Displays, Society of Plastic Engineers, Inc., 1979, pp. 151-154.
Davidovics Michel
Davidovits Joseph
Davidovits Nicolas
Bell Mark L.
Green Anthony J.
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