The forming methods of ceramic based composite materials can be divided into two categories: one is for reinforcing materials such as ceramic short fibers, whiskers, particles, etc. The forming process of composite materials is basically the same as that of ceramics, such as slurry casting method, hot pressing sintering method, etc; The other type is for carbon, graphite, and ceramic continuous fiber reinforced materials. The forming process of composite materials often adopts powder metallurgy, slurry infiltration method, slurry immersion hot pressing sintering method, and chemical vapor infiltration method.
(1) Powder metallurgy method, also known as compression sintering method or mixed compression method, is widely used in the preparation of special ceramics and certain glass ceramics. The method is to mix ceramic powder as the matrix, reinforcement material, and added adhesive evenly, cold press them into the desired shape, and then sinter or directly hot press sinter them to produce ceramic matrix composite materials. The former is called cold pressing sintering method, while the latter is called hot pressing sintering method. During hot pressing sintering, the densification rate can be increased under the simultaneous action of pressure and high temperature, resulting in products with no pores, fine grains, and excellent mechanical properties. The difficulty of using powder metallurgy for forming processing lies in the difficulty of mixing the matrix and reinforcement materials, and the fact that the product and fibers are prone to breakage during mixing or pressing, especially under cold pressing conditions.
(2) The slurry infiltration method involves weaving the fiber-reinforced material into the desired shape, compacting it with ceramic slurry, drying it, and then sintering it. The difference between this method and powder metallurgy is that the mixture is in the form of a slurry. Its advantages are that it does not damage the reinforcement, the process is relatively simple, and no mold is needed; The disadvantage is that the distribution of reinforcement in the ceramic matrix is not uniform.
(3) The slurry free hot pressing forming method immerses fiber or fabric reinforcement in a prepared rigid ceramic powder slurry, and then weaves the fiber or fabric reinforcement containing the slurry into a certain structured bad body. After drying, it is hot pressed and sintered at high temperature and high pressure to become a product. The advantages of the slurry immersion hot pressing method are that the heating temperature is lower than that of crystalline ceramics, the reinforcement is not easily damaged, the stacking sequence of the laminates can be arranged arbitrarily, the fiber distribution is uniform, the porosity is low, the strength obtained is high, the process is relatively simple, and there is no need for forming molds, which can produce large parts. The disadvantage is that it cannot produce parts with overly complex shapes, and the base material must be low melting point or low softening point ceramics.
(4) Chemical vapor infiltration (CVI) method, also known as chemical vapor infiltration (CVI) method, is a process of weaving reinforcing fibers into a preform of the desired shape, placing it in a reaction chamber at a certain temperature, and then introducing a certain gas source to produce thermal decomposition or chemical reaction deposition of the desired ceramic matrix on the fiber surface of the preform pores, until all pores in the preform are completely filled, obtaining high-density, high-strength, and high toughness parts.