With the continuous innovation of material technology, more and more bold attempts to use new materials and processes have appeared in the research and development and production of automobiles, and many of them have thrown out cross-border collaborations among top brands.
In 2011, supercar maker Bugatti and KPM-BERLIN jointly released a unique customized version of the "ceramic" supercar-Bugatti Veyron SE, "the world's first porcelain concept as an interior and exterior design element. "The car", this 1.4 million euros orphan factory uses unique ceramic parts in seven different parts such as exterior and interior. The ceramic version of Veyron was shocked by the global collectors and car fans as soon as it was released, because for most people there seemed to be a misunderstanding of the "ceramic" material. Still stuck on the traditional understanding of the past.
The rapid development of the automobile industry has made people's requirements for automobile safety, energy saving, comfort, and intelligence increasingly prominent. At the same time, the state's restrictions on noise control and exhaust pollution have also demanded higher due to the development of society. So that special ceramic materials with specific properties such as insulation, dielectricity, semiconductority, piezoelectricity, and magnetic permeability can have many functions in automobiles, which is a performance that traditional ceramics do not have.
1. Classification of ceramic materials
(1) Classified by chemical composition:
① Oxide ceramics: It is the earliest ceramic material to be used. It has many types and is widely used. The most commonly used are Al2O3, SiO2, MgO, ZrO2, CeO2, CaO, and mullite and spinel. Among them, Al2O3 and SiO2 have the same application popularity as steel and aluminum in traditional metal materials. The commonly used glass and daily-use ceramics are composite oxide ceramics.
② Carbide ceramics: It is the material with the highest temperature resistance in the field of special ceramics. It has a higher melting point than oxides. For example, titanium carbide (TiC) has a melting point of 3460 ° C, tungsten carbide (WC) is 2720 ° C, and zirconium carbide ( ZrC) is 3450 ° C, and the vaporization point of silicon carbide (SiC) is 2600 ° C. Carbide ceramics also have good electrical conductivity, thermal conductivity, and chemical stability.
③Nitride ceramics: Most nitride ceramics have relatively high melting points. Although there are many types of nitride ceramics, their practical applications are limited. There are mainly silicon nitride (Si3N4), aluminum nitride (AIN), and boron nitride ( BN) and titanium nitride (TiN), etc., generally have very high molar hardness. Among them, Si3N4 has good comprehensive mechanical properties and high temperature resistance; TiN has high hardness; BN has wear resistance and wear reduction performance; AIN has thermoelectric properties, and its applications are becoming increasingly widespread.
④ Other compound ceramics refer to inorganic compounds other than the above three types of ceramics and metals and molecular materials, including borides often used as ceramic additives, and chalcogenide ceramics with optical and electrical properties, etc., and their research and application are also increasing.
2. Application of special ceramic materials in automobiles
Special ceramics have excellent strength, hardness, insulation, thermal conductivity, high temperature resistance, oxidation resistance, corrosion resistance, abrasion resistance, high temperature strength and other excellent mechanical, thermal, and chemical properties, so they are used under very severe environmental engineering application conditions The high stability and excellent mechanical properties exhibited have attracted much attention in the automotive industry. It is widely used in the manufacture of engines and heat exchange parts, and as the base of spark plugs for ignition systems of gasoline engines.
① Ceramic glow plug
Glow plugs are also called glow plugs. When the diesel engine cools in severe cold environments, it provides thermal energy to improve starting performance. Therefore, the glow plugs are required to have a rapid temperature rise and maintain a temperature-sensitive state for a long time. The first generation of glow plugs was made of metal, the second generation was made of cermet glow plugs with tungsten wires buried in silicon nitride ceramics, and the third generation was all-ceramic glow plugs made entirely of conductive ceramics. Ceramic glow plugs can effectively save energy and reduce emissions in diesel engine emission control due to its fast heating, high temperature, energy saving and environmental protection, and long service life. Not only can it not completely change the original diesel electromechanical hot plug cold start system, It can replace the existing low-temperature starting preheating and emission reduction methods, and can also meet customer needs in harsh low-temperature environments.
The all-ceramic glow plug heating element is composed of multi-layer ceramic composite materials. The silicon nitride material is selected. It has excellent acid and alkali resistance and 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 the temperature difference of the traditional glow plug heat conduction medium. In the normal test, the temperature rise rate can be as fast as 1.5S to 850 ℃, which greatly shortens the waiting time of the engine. Operating temperature (1150 ° C), and the normal use of the engine can still be guaranteed in the environment of -40 degrees Celsius, to better optimize the combustion conditions of the diesel engine in the cylinder at low temperatures and reduce the emissions of harmful substances, In the case of plug cold start system, it can directly replace metal glow plug products. (Wulong, 2010) and can protect the internal heating elements from oxidation, especially to meet the working conditions of special task machinery operating in remote areas.
② Ceramic piston
The earliest piston material used for internal combustion engine pistons is cast iron. The most commonly used is nodular cast iron and malleable cast iron. Cast iron materials still have very high strength at high temperatures, which can greatly increase the output power of internal combustion engines. Therefore, cast iron pistons are mainly used in High-power engines such as ships, construction machinery and cargo locomotives. At the same time, its disadvantages have gradually emerged. Its biggest disadvantage is that the special performance under extreme conditions has begun to meet bottlenecks. It has gradually failed to meet the pursuit of performance in modern technology and application scenarios, limiting its use in the future. . In order to optimize the quality and performance of automobile internal combustion engines, non-alloy pistons came into being. For example, representative ceramic piston piston rings are very popular, and their methods are roughly divided into two types, one is the sintering method of directly manufacturing piston rings using zirconia and alumina, and the other is using physical vapor deposition or plasma. Method for forming ceramic coating on the surface of metal piston ring by spraying. The European and American markets prefer the latter solution. There are many coating technology companies in North America that prepare ceramic coatings for transmission systems. Nano-scale coatings can greatly reduce the friction coefficient of piston components, thereby improving transmission efficiency, and enhancing component wear resistance. Increase component life.
Ceramic pistons are generally used in diesel engines. The use of ceramic materials instead of alloy materials in turbo diesel engines can further reduce the design of cooling devices, and the overall production cost is expected to decrease. In the direct injection diesel engine, the ceramic material is embedded in the top of the piston using the high temperature resistance of the ceramic material, and its thermal efficiency, noise and emissions are improved. The ceramic fiber piston made of silicon nitride material can prevent the "cold melt and hot pull" phenomenon caused by the large thermal expansion coefficient due to its good wear resistance.
③ Ceramic cylinder liner
Cylinder liner is one of the most severe 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. It wears quickly and is prone to cylinder pulling. The excellent characteristics of advanced ceramic materials can alleviate this Problems arise. According to different needs, ceramic cylinder liners can have the following three forms: first, the inner surface of the cylinder liner is sprayed with ceramic coating, secondly, the upper ring of the cylinder liner is made of ceramic materials only, and third, the whole is made of a composite of metal and ceramic materials. Ceramic cylinder liner. The use of all-ceramic cylinder liners instead of traditional cylinder liners can prevent the loss of thermal energy in the cylinders, simplify the engine structure, thereby improving thermal efficiency and reducing engine quality.
④ Ceramic gas distribution mechanism
Automotive gas distribution mechanisms generally consist of camshafts, tappets, pushrods, rocker arms, rocker shafts, valve springs, and valve guides. From the scope of application, ceramic parts are mostly used on the sliding parts of the engine valve system. These parts mainly include ceramic rocker contacts, ceramic valve tappets, ceramic valves and so on. Ceramic valves were first developed actively 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, with the goal of ceramicizing valve cones. Exhaust valve cone sprayed ceramics have greatly improved air leakage resistance. The metal material of the spray exhaust valve is Ni-Cr, and the ceramic material is Cr3C2. Shanghai Internal Combustion Engine Research Institute has started successful experimental research on ceramic tappets in the late 1980s. In the 1990s, experimental research on the application of ceramic valves, tappets, and rockers on Guangxi Yuchai 6105 diesel engine has been carried out.
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. China's 492QA engine can save 2% -8% of fuel under various working conditions after adopting ceramic gas distribution mechanism. Mitsubishi's engine rocker made of ceramic and ceramic valve made of Isuzu's silicon nitride have also achieved good results in use. (Zhou Zhaoxiong, 1987)
⑤Ceramic rotor
Rotors are the main components of high-speed rotation in power machinery or work machinery such as electric motors, generators, gas turbines and turbine compressors. Japan's Special Ceramics Corporation (NGK / NTK) has developed the "ceramic rotor for pressurized gas supply to turbines" for the first time in the world after conducting research on "manufacturing technology for silicon nitride sintering systems using gas pressure sintering."
The sintered body obtained by this air pressure sintering method has almost no pores in the interior, and has excellent characteristics such as high strength reliability and strong oxidation resistance. In addition, the newly developed rotor is about 40% lighter than conventional rotors. , The moment of inertia when rotating is small. From low-speed operation to high-speed operation, it can achieve better results than previous turbines, so it is expected to reduce vehicle weight, increase power, and reduce fuel consumption.
In addition, the components made of special ceramic materials on automobiles include ceramic supports for catalytic converters for vehicles, carriers for exhaust purification honeycomb ceramic materials, ceramic exhaust 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.