Special ceramics uses refined high-purity products as raw materials, and is different from traditional ceramics in all aspects such as chemical composition, internal structure, performance and use efficiency. Special ceramics have various excellent and unique properties. Applying them to automobiles can reduce the quality of the vehicle itself, improve the thermal efficiency of the engine, reduce oil and gas pollution, reduce exhaust pollution, and increase the life of wearing parts.
Classification of special ceramic materials for automobiles
01 Alumina ceramics
Alumina ceramics are also called high alumina ceramics. The raw material is industrial alumina. The preparation method is to add a small amount of additives to industrial alumina and then make it through sintering and sintering. Products with high surface roughness and precision requirements should Grinding and polishing. The strength of alumina ceramics is higher than that of ordinary ceramics; the hardness is very high, second only to diamond, boron carbide, cubic boron nitride, and silicon carbide, and it has good wear resistance; excellent high temperature resistance, and minimal creep; corrosion resistance Very strong; good insulation performance.
The excellent high temperature and dielectric properties of alumina ceramics make it suitable for making spark plugs for internal combustion engines; good abrasion resistance can ensure that the manufactured pistons can be processed to a relatively high accuracy and roughness.
02 Silicon nitride ceramics
Silicon nitride ceramics are rich in raw materials and good processing performance. The main performance characteristics are high strength, good chemical stability, good temperature resistance, wear resistance, insulation, and high precision. The preparation methods mainly include a reaction sintering method and a hot-pressing sintering method.
Using silicon nitride materials to manufacture engines, the operating temperature can theoretically be increased to about 1370 ° C. Increasing the temperature allows for sufficient combustion, improved engine thermal efficiency, and reduced exhaust pollution. Reaction sintered silicon nitride can be used to manufacture pump mechanical seal rings, high temperature bearings, valves and other parts.
03 Silicon Carbide Ceramics
Silicon carbide ceramics are made of silicon carbide powder (quartz, carbon, and wood chips are charged into an electric arc furnace and synthesized at a high temperature of 1900 ~ 2000 ° C) by using powder metallurgy through reaction sintering and hot pressing sintering processes. The biggest features of silicon carbide ceramics are high temperature and high strength (bending strength is still maintained at a high level of 500 ~ 600MPa at 1400 ° C), strong thermal conductivity, good thermal stability, wear resistance, corrosion resistance, and good creep resistance.
Silicon carbide ceramics can be used to make rocket tail nozzles, throats for casting metals, thermocouple sleeves, blades and bearings for gas turbines.
Application of special ceramics in automobiles
01 Application in Automotive Engines
(1) Adiabatic engine
The ceramic heat-insulating engine is made of the characteristics of ceramic heat resistance, wear resistance, corrosion resistance, and small thermal expansion coefficient. Its working temperature can reach 1300 ℃ ~ 1500 ℃, which can reduce the heat loss in the cylinder, make the fuel fully burn, and reduce the environmental impact Pollution. In addition, it can simplify the overall structure of the engine, reducing engine weight and energy consumption.
(2) Ceramic piston
Ceramic fiber pistons made of silicon nitride ceramic materials have good abrasion resistance and can effectively prevent the "cold knock and hot pull" phenomenon of aluminum alloy pistons due to large thermal expansion coefficients.
(3) Ceramic cylinder liner
The upper ring of the cylinder liner is made of ceramic material or the full ceramic cylinder liner is made of a combination of metal and ceramic materials. Instead of the traditional cylinder liner, it can prevent heat loss in the cylinder, simplify the engine structure, and then improve thermal efficiency and reduce engine quality.
(4) Ceramic gas distribution mechanism
Utilizing the characteristics of low density, heat resistance and wear resistance of ceramic materials, using ceramic materials to manufacture valves, valve seats, tappets, valve springs and rocker arms can reduce the deformation of valve seats and bounce when seated, reduce noise and vibration, and prolong Service life.
02 Application in Automotive Brake
The brake disc in a ceramic brake can be made of reinforced ceramics, that is, ceramic powder and carbon fiber are used to replace the metal in the prior art. The surface hardness of the carbon silicon compound is close to that of diamond, and the carbon fiber structure makes it strong, impact-resistant, corrosion-resistant, and extremely wear-resistant. Compared with steel brake discs, ceramic brake discs reduce the quality of the entire vehicle, reduce fuel consumption, extend the service life, greatly improve the wear resistance, high temperature resistance, corrosion resistance, braking performance of the brake discs, and heat dissipation. Works well.
03Application in Automotive Shock Absorber
The shock absorber of a premium car is a smart shock absorber developed by comprehensively utilizing the sensitive ceramic positive piezoelectric effect, reverse piezoelectric effect, and electrostrictive effect, so that the vibration caused by rough roads can be minimized.
04Application in automotive spraying technology
In recent years, ceramic thin film spraying technology widely used in aerospace technology has begun to be applied to automobiles. The advantage of this technology is that it has good thermal insulation effect, can withstand high temperature and pressure, mature technology, and stable quality.
05 Application in Automotive Sensors
With the development of the automobile industry, people have higher and higher requirements for the safety, energy saving, comfort and intelligence of automobiles, and the country has higher requirements for noise and exhaust pollution restrictions. This makes functional ceramic materials with specific properties such as insulation, dielectric, semiconductor, and magnetic permeability more and more widely used as a variety of control sensitive components in automobiles, and the varieties and specifications are becoming more and more perfect.
06 Application on Car Catalytic Converter Carrier
In automotive catalytic converters, cordierite honeycomb ceramics are used as catalyst carriers. The honeycomb ceramic carriers have a porous, thin structure with a material strength of 100 N / mm2. Cordierite has high temperature resistance, high strength, low thermal expansion coefficient, and small volume mass, which is suitable for the environment of catalyst support.
07 Application in Automotive Bearings
The main material of ceramic bearings is silicon nitride ceramics, which has a high working temperature and wear resistance, which can increase the speed. The bearing components have lower requirements for lubrication and cooling, and ceramic bearings are non-magnetic, corrosion-resistant and have good insulation.