With the continuous development of science and technology, more and more new materials and new processes are used in the research and development and production stages of automobiles. Possibly, for the use of new materials, China’s ancient invention-ceramics is one of them.
For ceramics, they are usually divided into traditional ceramics and special ceramics according to different materials and firing processes. Traditional ceramics are fired from natural silicate minerals, also called silicate ceramics. In contrast to this, various ceramics developed in modern times are collectively called special ceramics, also known as new ceramics, high-tech ceramics or fine ceramics.
Application of ceramic materials in automobiles
1. Application of ceramics in automotive sensors
The requirements for automotive sensors are long-term applicable to the harsh environments unique to automobiles (high temperature, low temperature, vibration, acceleration, humidity, noise, exhaust gas), and should have the characteristics of small size, light weight, good reusability and wide output range. Ceramic heat resistance, corrosion resistance, wear resistance and its potential excellent electromagnetic and optical functions have been fully utilized in recent years with the advancement of manufacturing technology. Ceramic sensors can fully meet the above requirements.
2. Application of ceramics on automobile engines
The new ceramics are made by sintering inorganic non-metals such as silicon carbide and silicon nitride. Compared with the alumina ceramics used in the past, it has more than three times the strength and can withstand high temperatures above 1000 degrees Celsius. New materials have promoted the development of new uses in automobiles. For example: To reduce the fuel consumption of diesel engines by more than 30%, it can be said that new ceramics are indispensable materials. At present, about 78% of the combustion energy in the gasoline engine is lost in heat energy and heat transfer. The thermal efficiency of the diesel engine is 33%, which is very superior to the gasoline engine. However, more than 60% of the thermal energy is still lost. Therefore, in order to reduce this part of the loss, the combustion chamber is insulated with ceramic materials with good thermal insulation properties, and then exhaust gas turbochargers and power turbines are used to recover exhaust energy. Experiments have shown that this can increase the thermal efficiency to 48%.
At the same time, due to the use of new ceramics, instantaneous rapid start of diesel engines will become possible. The turbocharger adopts a new type of ceramic, which has more superior heat resistance than today’s super heat-resistant alloy, and the specific gravity is only about one third of that of a metal turbine. Therefore, the new ceramic turbine can compensate for the shortcomings of low dynamic response of the metal turbine. Other ongoing research is: using new ceramic piston pins and piston rings and other moving parts. Due to the reduction in weight, engine efficiency is expected to be improved.
3. Application of ceramics in automobile brakes
Ceramic brakes are manufactured on the basis of carbon fiber brakes. A carbon fiber brake disc is initially composed of carbon fiber and resin. It is pressed into shape by a machine. Afterwards, it is heated, carbonized, heated, cooled and other processes to make a ceramic brake. The hardness of the carbon silicon compound surface of the ceramic brake is close to diamond The carbon fiber structure inside makes it sturdy, impact-resistant and corrosion-resistant, making the disc extremely wear-resistant.
At present, this kind of technology is not only used in F1 racing, but also involved in super civilian sports cars, such as Mercedes-Benz CL55 AMG.
4. Application of ceramics on automobile shock absorbers
The anti-vibration device of the high-end car is a smart anti-vibration device developed by comprehensively utilizing the positive piezoelectric effect, inverse piezoelectric effect and electrostrictive effect of sensitive ceramics. Due to the use of high-sensitivity ceramic components, this shock absorber has the function of recognizing the road surface and being able to do self-adjustment, which can minimize the vibration of the car caused by the rough road surface to a minimum.
5. Application of ceramics 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 advantages of this technology are good heat insulation effect, can withstand high temperature and high pressure, mature technology and stable quality. In order to achieve the goal of low heat dissipation, ceramic spraying can be applied to the engine combustion chamber components, such as zirconia sprayed on the top of the piston and zirconia sprayed on the cylinder liner. After this treatment, the engine can reduce heat loss, reduce the quality of the engine, reduce the size of the engine, and reduce the fuel consumption.
Special ceramics use refined high-purity chemical products as raw materials, and are different from traditional ceramics in chemical composition, internal structure, performance and use efficiency. Therefore, under the very strict environmental engineering application conditions, its high stability and excellent mechanical properties have also attracted attention in the automotive industry, and are widely used in the manufacture of engines and heat exchange parts, spark plugs for gasoline engine ignition systems Of the substrate.
Ceramic glow plug
The glow plug is also called a glow plug. When the diesel engine is cooled in a severe cold environment, it provides heat energy to improve the starting performance. Therefore, the glow plug is required to have the characteristics of rapid temperature rise and long-term maintenance of the temperature sensing state.
The ceramic glow plug can effectively achieve energy saving and emission reduction in diesel engine emission control due to its fast heating, high temperature, energy saving, environmental protection and long service life. It can not only completely change the original diesel electromechanical glow plug cold start system, but also completely It can replace the existing low-temperature start-up preheating and emission reduction methods, and can also meet customer needs in harsh low-temperature environments.
Full ceramic glow plug
The all-ceramic glow plug heating element is composed of multiple layers of ceramic composite materials. It is made of silicon nitride and has excellent acid and alkali resistance. It is not easy to adhere to other substances. The working temperature is up to more than 1000 degrees Celsius. The heating part is an external heating type ceramic material, which can overcome the problem of temperature difference of the traditional glow plug thermal conduction medium. In the conventional test, the temperature rise rate can be as fast as 1.5S to 850 ° C, which greatly shortens the engine waiting time for starting Operating temperature (1150 ℃), and can still ensure the normal use of the engine in an environment of -40 degrees Celsius, better optimize the combustion state of the diesel engine at low temperature and reduce the emission of harmful substances, without changing the original diesel electromechanical heating In the case of plug cold start system, it can directly replace metal glow plug products. And can protect the internal heating element from being oxidized, especially to meet the working conditions of special task machinery in remote areas.
Special ceramic piston for internal combustion engine
The earliest piston material used for internal combustion engine pistons is cast iron, and the most used are nodular cast iron and malleable cast iron materials. Cast iron materials still have very high strength at high temperatures, which can greatly increase the output power of internal combustion engines, so cast iron pistons are mainly used in High-power engines such as ships, engineering machinery and cargo-powered locomotives.
At the same time, its disadvantages have gradually emerged. Its biggest disadvantage is that its special performance under extreme conditions has begun to encounter bottlenecks. It has gradually failed to meet the performance requirements of modern technologies and application scenarios, limiting its application in the future. .
In order to optimize the quality and performance of automobile internal combustion engines, non-alloy pistons came into being.
For example, the representative ceramic piston ring is very popular, and its methods are roughly divided into two types.
One is the sintering method of directly manufacturing piston rings from zirconia and alumina,
The other method is to form a ceramic coating on the surface of the metal piston ring by physical vapor deposition or plasma spraying.
Diesel ceramic piston
Ceramic pistons are generally used in diesel engines. In turbo diesel engines, the use of ceramic materials instead of alloy materials can further reduce the design of the cooling device, and the overall production cost is expected to be reduced. In the direct injection diesel engine, the high temperature resistance of the ceramic material is inserted into the ceramic block on the top of the piston, and its thermal efficiency, noise and emissions are improved. The ceramic fiber piston made of silicon nitride material, because of its good wear resistance, can also prevent the “cold melt heat” phenomenon caused by the large thermal expansion coefficient of the aluminum alloy piston.
Ceramic cylinder liner
The ceramic cylinder liner is one of the worst parts in the working environment of the internal combustion engine. It withstands the impact of high temperature and high pressure and the reciprocating friction of the piston ring. Generation of problems.
According to different needs, ceramic cylinder liners can have the following three forms:
One is to spray ceramic coating on the inner surface of the cylinder liner,
The second is to use only ceramic materials to make the cylinder liner upper ring,
The third is to use metal and ceramic materials to make a full ceramic cylinder liner.
The use of all-ceramic cylinder liners instead of traditional cylinder liners prevents heat loss in the cylinder, simplifies the engine structure, and thereby improves thermal efficiency and reduces engine quality.
Ceramic gas distribution mechanism
Automobile gas distribution mechanism is generally composed of some related components such as camshaft, tappet, push rod, rocker arm, rocker shaft, valve spring and valve guide.
From the perspective of application range, ceramic parts are mostly used for sliding parts of engine gas distribution system. These parts mainly include ceramic rocker contacts, ceramic valve tappets, ceramic valves, etc.
Ceramic valves were initially actively developed in Japan and Germany. In order to improve the durability and reliability of marine diesel engines, the Japanese Steel Pipe Company has been developing ceramic exhaust valves since the 1980s. The goal is to achieve ceramic valve cones.
Spray exhaust valve
The ceramic sprayed on the cone surface of the exhaust valve greatly improves the air leakage resistance. The metal material of the spray exhaust valve is Ni-Cr, and the ceramic material is Cr3C2.
Using the characteristics of low density, heat resistance and wear resistance of ceramic materials, manufacturing valves, valve seats, tappets, valve springs and rocker arms from ceramic materials can reduce the deformation of the valve seat and the bounce when seated, reduce noise and vibration, and extend Service life.
The rotor is mostly the main component of high-speed rotation in power machinery or working machinery such as electric motors, generators, gas turbines and turbine compressors.
Since the Japanese special ceramics company (NGK / NTK) conducted research on “manufacturing technology of silicon nitride sintering system using air pressure sintering method”, it developed the “ceramic rotor for pressurized air supply for turbine” for the first time in the world.
The sintered body obtained by this air pressure sintering method has almost no residual pores, and has excellent characteristics such as high strength reliability and strong oxidation resistance. In addition, the newly developed rotor is about 40% lighter than the conventional rotor. , The moment of inertia when rotating is small. From low-speed operation to high-speed operation, compared with the previous turbine, it can play a better effect, which is expected to achieve vehicle weight reduction, high power, and low fuel consumption.
In addition, the components made of special ceramic materials for automobiles include ceramic carriers for catalytic converters for vehicles, honeycomb ceramic material carriers for exhaust gas purification, ceramic honeycomb filters for diesel exhaust purification, ceramic automobile brakes, brake pads, ceramic bearings for vehicles, Thermal ceramic sensors, turbo chargers, ceramic composite exhaust pipes and other components are not one by one examples.
Classification and characteristics of ceramics
The performance of ceramics is determined by two factors. The first is the structure of matter, mainly the nature of chemical bonds and the crystal structure. They determine the properties of ceramic materials, such as high temperature resistance, semiconductority and insulation. Second is the microstructure, including distribution, grain size, shape, pore size and distribution, impurities, defects, etc.
Ordinary ceramics are made of clay, feldspar and quartz as raw materials, which are prepared and sintered. This type of ceramic is hard in texture, not oxidized and rusted, corrosion-resistant, non-conductive, able to withstand a certain high temperature, good formability, low cost, but low strength. Generally, the maximum operating temperature does not exceed 1200 degrees Celsius. This type of ceramic has a large output and many types, and is widely used in electrical and chemical industries.
Alumina ceramics are also called high-alumina ceramics, and the main components are alumina and silica. It has high strength, high hardness, corrosion resistance, good insulation, and a heat-resistant temperature of up to 1600 degrees Celsius, but its shortcomings are high brittleness, poor seismic resistance, complex technology, and high cost. The excellent high-temperature performance and dielectric performance of alumina ceramic make it suitable for making engine spark plugs; good wear resistance can ensure that the manufactured piston can be processed to a very high precision and roughness.
Silicon carbide ceramics
Silicon carbide ceramics are made of silicon carbide powder by powder metallurgy through reaction sintering or hot pressing sintering process. The biggest feature of silicon carbide ceramics is high temperature strength, good thermal stability, good wear resistance and creep resistance. It is suitable for casting metal throat, thermocouple bushing, gas turbine blades, bearings and other parts. At the same time, due to its high thermal conductivity, it is also suitable for heat exchanger materials under high temperature conditions, and can also be used to make various pump seals.
Silicon nitride ceramics
Silicon nitride ceramics are rich in raw materials and have good workability. They can produce parts of various sizes and precision at low cost, especially parts with complex shapes, and the yield is higher than other ceramic materials. Silicon nitride ceramic has good resistance to rapid temperature change and high hardness. Its hardness is second only to diamond, boron nitride and other substances. The engine is made of silicon nitride ceramic material. As the operating temperature is increased to 1370 degrees Celsius, the engine efficiency can be increased by 30%. At the same time, due to the temperature increase, the fuel can be fully burned, and the pollutant components in the exhaust gas are greatly reduced, which not only reduces energy consumption, but also reduces environmental pollution.
Other ceramic materials
There are many types of ceramic materials with their own characteristics, and they can be made into various functional components. Lithium oxide ceramics are high-temperature materials, talc ceramics are high-frequency insulating materials, thorium oxide ceramics are dielectric materials, barium titanate ceramics are photoelectric materials, and cermets such as boride, nitride, and silicide are ultra-high temperature materials. Ferrite ceramics are permanent magnets, memory magnets, magnetic heads and other materials, rare earth cobalt ceramics are memory materials, and semiconductor ceramics are sub-sensitive components, solar cells and other materials
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Post time: Apr-09-2020