▎ 摘　　要

NOVELTY - Preparation of carbon fiber reinforced (Cf)/ carbon -silicon carbide composite material involves (i) superimposing a weft-free cloth and a mesh tire to form an axial unit layer and needling the continuous fiber wound composite carbon fiber mesh to form a hoop unit layer to obtain carbon fiber performs, (ii) performing pyrolytic carbon densification on carbon fiber preforms to obtain a Cf/carbon porous material, (iii) heating, (iv) adding dehydrated alcohol and silane coupling agent, adding ethyl cellulose and carbon nanofiller to obtain a mixture, (v) adding the Cf/carbon porous material, injecting the well-stirred carbon nanofiller slurry to prepare Cf/carbon-carbon nanofillers, (vi) placing the Cf/carbon-carbon nanofillers in a graphite crucible filled with silicon powder, filling the pores of the porous material with silicon carbide to obtain Cf/carbon-silicon carbide composite material, and (vii) heating. USE - Preparation method of Cf/carbon-silicon carbide composite material for engine piston (claimed) used in internal combustion engine, diesel engine and petrol engine. ADVANTAGE - The method provides high reliability, low damage sensitive and high temperature ceramic double-element composite material with excellent self-lubricating performance, high room temperature and high-temperature mechanical strength, small thermal expansion coefficient, low crack damage sensitivity and excellent service reliability, and promotes the application of the material in the engine piston field of further application. DETAILED DESCRIPTION - Preparation of carbon fiber reinforced (Cf)/ carbon-silicon carbide composite material involves (i) cyclically superimposing a weft-free cloth and a mesh tire to form an axial unit layer according to the cylinder shape structure of the engine piston, through relay acupuncture, needling the continuous fiber wound composite carbon fiber mesh to form a hoop unit layer, alternately superimposing axial unit layer and annular unit layer and continuous needling to obtain carbon fiber performs, (ii) performing pyrolytic carbon densification on carbon fiber preforms for engine pistons by chemical vapor deposition method using a carbon source gas chosen from one or more of natural gas, propane, propylene and acetylene and dilution gas comprising nitrogen and/or hydrogen in volume ratio of carbon source gas and diluent gas of 1:1-14 at 860-1200degrees Celsius for 50-200 hours and pressure of 1000-5000 Pa for residence time of 1-2 seconds to obtain a Cf/carbon porous material having density of 1.15-1.55 g/cm3, (iii) heat-treating the prepared Cf/carbon porous material to high temperature at 1800-2450degrees Celsius in a high temperature furnace under an inert gas protective atmosphere comprising argon and pressure of 1000-5000 Pa for 1.5-2.5 hours, (iv) adding dehydrated alcohol and silane coupling agent into the beaker according to the mass ratio of (6-10):1, mixing, adjusting the pH value of the system to 4-6 with oxalic acid, adding ethyl cellulose and carbon nanofiller to the beaker to obtain a mixture, in which the mass ratio of silane coupling agent, ethyl cellulose and carbon nanofiller is (8-15):1:(32-60), using an ultrasonic disperser to ultrasonically disperse under ultrasonic dispersion power 500-800 W at 25-30degrees Celsius for 10-30 minutes and ball milling with a ball mill at speed of 150-300 rpm for 20-30 hours, in which the mass ratio of the grinding ball to mixture is (2-3):1, the carbon nanofillers comprise graphite, graphite oxide, graphene, graphene oxide, carbon nanotubes and has size of 50 mum or less, (v) adding the Cf/carbon porous material into a vacuum environment to exhaust the air in the pores, injecting the well-stirred carbon nanofiller slurry for vacuum impregnation for 1-2 hours, feeding compressed air at a rate of 1.5-2 MPa/hour to 3.0-3.2 MPa to start pressure impregnation, taking out after 1-2 hours and putting it an oven at 80-100degrees Celsius for 1-2 hours, repeating dipping and drying for 2-5 times to prepare Cf/carbon-carbon nanofillers, (vi) placing the Cf/carbon-carbon nanofillers in a graphite crucible filled with silicon powder, infiltrating molten silicon in a high-temperature furnace, filling the pores of the porous material with silicon carbide by in-situ reaction of molten silica with the matrix carbon and carbon nanofillers to obtain Cf/carbon-silicon carbide composite material, calculating the amount of silicon powder placed in the molten siliconizing process from the difference between the expected density of the Cf/carbon-silicon carbide composite and the density of the Cf/carbon-carbon nanofiller, burying the low-density Cf/carbon composite material in silicon powder, using a vacuum environment in the high-temperature furnace, in which the silicon powder has purity of more than 99% and particle size of 100-300 mesh, maintaining the molten siliconizing conditions at 1550-1750degrees Celsius for 1.5-3.5 hours and controlling the heating rate from 1200degrees Celsius to the final siliconizing temperature at 5.7-6.2degrees Celsius/minute, and (vii) heat-treating the Cf/carbon-silicon carbide composite to high-temperature heat treatment in a vacuum atmosphere at 1100-1300degrees Celsius for 1-3 hours at heating rate of 5-15degrees Celsius/minute and vacuum degree of 10-20 Pa, and free-cooling. INDEPENDENT CLAIMS are included for the following: (1) Piston, (2) Carbon nanofiller slurry, which comprises absolute ethanol, silane coupling agent, ethyl cellulose and carbon nanofiller, in which in mass ratio of absolute ethanol and silane coupling agent is (6-10):1 and mass ratio of silane coupling agent, ethyl cellulose and carbon nanofiller is (8-15):1:(32-60), and (3) Preparation of carbon nanofiller slurry.