METHOD OF MAKING THIN-WALL ARTICLES FROM COMPOSITE MATERIAL WITH GRADIENT PROPERTIES ON THICKNESS Russian patent published in 2015 - IPC C04B35/577 C04B35/573 B82Y40/00 

FIELD: chemistry.

SUBSTANCE: method of making thin-wall articles from composite material with gradient properties on the thickness thereof includes forming a frame of a layered or layered-piercing structure from heat-resistant carbon and/or silicon carbide fibres; packing said frame with carbonaceous matrix material to obtain a workpiece with porosity which varies from the protective layers to the bearing layers of the material of the intended article; filling the open pores of the workpiece material with dispersed carbon and siliconising. When forming the frame, a layer of graphite foil is placed between the protective and bearing layers or 1-2 boundary layers are impregnated with a suspension based on nanodispersed carbon particles. The frame is packed with carbonaceous matrix material as follows: first partially saturating the frame using vacuum isothermic method with pyrocarbon or silicon carbide until content thereof reaches, respectively, 6-10% and 8-15% of the weight of the frame made of carbon fibres and 3.6-6.0% and 4.8-9.0% of the weight of the frame made of silicon carbide fibres; impregnating the frame with a ceramic-forming polymer which is a silicon nitride or carbide precursor, and forming a plastic workpiece. Heat treatment of the workpiece is carried out at 1300-1500°C and atmospheric pressure in a medium of argon or especially pure nitrogen, after which the workpiece is saturated with pyrocarbon via a vacuum isothermic method until open porosity of the material of the bearing layers reaches 6-12% while preventing access to carbonaceous gas on the side of the protective layers of the material. The dispersed carbon used when filling open pores of the obtained workpiece is nanodispersed carbon or a mixture of nanodispersed carbon with finely dispersed carbon with particle size not greater than 3-5 mcm, and siliconisation is carried out via a vapour-liquid-phase method with initial mass-transfer of silicon into the pores of the material via capillary condensation of the vapour thereof at workpiece temperature of 1300-1600°C, reactor pressure not higher than 27 mmHg and silicon vapour temperature higher than workpiece temperature by 100-10 degrees, followed by heating and holding at 1650-1750°C for 1-2 hours.

EFFECT: making thin-wall articles without the need for mechanical processing.

5 cl, 1 tbl, 17 ex