Ceramics

Application of precision ceramics in automobile field

With the continuous expansion of application fields, advanced ceramic materials, as a structural/functional material, are becoming more and more important in the entire industrial manufacturing. Especially with the advancement of science and technology and the unique and good comprehensive properties of ceramic materials, ceramic materials have gradually been widely used in the automotive industry in recent years. From the current point of view, the application of ceramic materials in automobiles has been quite common, whether it is the key functional devices of automobiles or important structural parts. Today we will take a look at the many applications of ceramic materials in automobiles.

1. Properties of ceramic materials

General properties of ceramics:

Mechanical properties	The elastic modulus is higher than that of metal, the hardness is high, and the compressive strength is high; but the brittleness is large, the tensile strength is low, and the plasticity and toughness are also small.
Thermal properties	It has high melting point, high thermal strength, generally small thermal expansion coefficient and thermal conductivity, and can still maintain room temperature performance above 1000 °C.
Electrical properties	It is generally an excellent insulator, and individual ceramics have electrical conductivity and magnetic permeability, and belong to new functional ceramic materials.
Chemical properties	Very stable, resistant to corrosion by acid, alkali, salt, etc., no aging, no oxidation (outside of some ceramics)

2. Classification of ceramic materials

(1) Oxide ceramics

Oxide ceramics are the earliest ceramic materials used, and they are also the most diverse and widely used. The most commonly used are Al2O3, SiO2, MgO, ZrO2, CeO2, CaO, mullite and spinel, among which Al2O3 and SiO2 are widely used like steel and aluminum in metal materials. In addition to the above single oxides, there are also a large number of oxide composite oxide ceramics.

(2) Carbide ceramics

Carbide ceramics have a higher melting point than oxides, but carbides are easily oxidized, so they must be prevented during manufacture and use. The most commonly used are SiC, WC, B4C, TiC, etc.

(3) Nitride ceramics

Including Si3N4, TiN, BN, AlN, etc. Among them, Si3N4 has excellent comprehensive mechanical properties and high temperature resistance; TiN has high hardness; BN has wear resistance and antifriction properties; AlN has thermoelectric properties, and its applications are becoming more and more extensive.

(4) Other compound ceramics

Refers to inorganic compounds other than the above-mentioned types of ceramics and metals and molecular materials, including boride ceramics often used as ceramic additives and chalcogenide ceramics with optical, electrical and other properties, and their research and applications are also increasing.

3. Ceramic adiabatic engine

Ceramic materials have the advantages of heat resistance, wear resistance, corrosion resistance, low density and strong heat insulation. The use of ceramic materials in the preparation of ceramic adiabatic engines can well prevent the loss of thermal energy inside the cylinder. Although the density of ceramic is not as low as that of aluminum, it is much lower than that of steel. The lower density means that the weight of the engine can be reduced. Combined with the weight reduced by the simplification of the cooling system, the weight of the ceramic engine can be made lighter than the metal engine. Among them, the main ceramic parts are as follows.

(1) Engine heart

In order to improve the thermal efficiency of the engine and save energy, the ceramic heat-resistant, wear-resistant, corrosion-resistant, high elastic modulus (low expansion coefficient), low density, and good thermal insulation characteristics of ceramic materials can be used to make ceramic thermal insulation engine cores. The loss of heat energy in the cylinder is prevented, the overall structure of the engine is simplified, and the weight of the engine is reduced.

(2) Ceramic piston

In general, ceramic pistons are used in diesel engines. Previously, precious metals were used, but now they are replaced by ceramic materials, which greatly saves costs in the preparation of vortex chamber diesel engines.

(3) Ceramic cylinder liner

Ceramic cylinder liners can be divided into the following forms: the first is that the inner surface of the cylinder liner is completely covered by ceramic materials, and the Japanese Komatsu engine is a typical example; the second is that only ceramics are used in the preparation of the upper ring of the cylinder liner material; and the third is the composite preparation of metal and ceramic materials

4. Piezoelectric ceramics

In recent years, with the sharp increase in the number of automobiles in my country, people have higher and higher requirements for automobile safety and comfort. Using the piezoelectric effect of piezoelectric ceramics, functions such as sensing, driving, vibration isolation and noise reduction in the automotive field can be realized, which can meet the requirements of automobiles in terms of safety and comfort.

(1) Application in the field of automotive sensing

There are dozens to hundreds of sensors installed on an ordinary family car, while the number of sensors on a luxury car can be as many as 200. As far as piezoelectric ceramic sensors are concerned, piezoelectric ceramic knock sensors, ultrasonic sensors, acceleration sensors, etc. are common.

(2) Application in the field of automobile drive

Using the inverse piezoelectric effect of piezoelectric ceramics, piezoelectric drivers can be made, which are used to drive electric rearview mirrors, electric doors and windows, electric seats, etc. in the automotive field.

(3) Application in the field of automobile vibration isolation and noise reduction

Toshiyuki Shibayama et al. used piezoelectric ceramics to design an active mount for reducing the large vibration of the engine at idle speed. The principle is to use piezoelectric ceramics to drive the large piston in the mount, and the small piston connected to the large piston moves. The displacement amplifies the displacement of the piezoelectric ceramics, so as to obtain a larger displacement amount required for vibration reduction under idle speed conditions, and has a good inhibitory effect on the vibration of the engine under idle speed conditions.

(4) Application in tire pressure detection system

The power generation characteristics of piezoelectric ceramics provide a possibility for the passive scheme of automobile tire pressure monitoring system. The piezoelectric ceramic installed in the tire is continuously squeezed by the continuous squeezing effect of the tire rotation. According to the positive piezoelectric effect, the piezoelectric ceramic can continuously generate electricity and continuously provide energy and power for the pressure monitoring system.

5. Exhaust gas treatment - honeycomb ceramics/porous ceramics

Honeycomb ceramics are industrial ceramics with honeycomb pores as the main structure. Honeycomb ceramics can be divided into cordierite, mullite, aluminum titanate, silicon carbide, zirconia, alumina and their composite materials according to their materials. According to different conditions of use, select raw materials with different properties. Honeycomb ceramics are environmentally friendly materials with strong adsorption capacity, excellent pore structure, good thermal stability, low density, and good wear resistance. With the requirements of the National VI standard to upgrade the automobile exhaust gas treatment system, the honeycomb ceramic market will usher in a stage of substantial expansion.

6. MLCC is widely used in automotive electronics

The application of MLCC in automobiles includes satellite positioning system, central control system, radio navigation system, body stability control system, ADAS system, and various systems have great demand for MLCC. Models with different degrees of electrification have different demand for MLCCs. One pure electric vehicle needs 18,000 MLCCs.

Multiple systems in the car need to use MLCC

Car Model	Pure electric	Hybrid Electric/Plug-in Hybrid	Micro Hybrid Vehicle	Smart fuel-efficient car	Internal combustion engine vehicle
Demand per MLCC	18000	12000	4800	3900	3000

Demand for MLCCs of Different Models

7. Ceramic brake pads

As a new material, the new ceramic-based friction material can effectively improve the safety and stability of automobile braking, and is gradually applied to the brake pads of automobiles. At present, the research on ceramic tribology at home and abroad mainly focuses on a few ceramic materials such as SiC, Si3N4, Al2O3, BN and ZrO2. Among them, C/C-SiC composite materials and Al2O3 ceramic friction materials are the most widely used. Ceramic-based brake pads are popular because of their many excellent properties, especially they have good corrosion resistance and durability, are clean and environmentally friendly products with stable performance, and do not produce A lot of noise, so it can ensure people's driving comfort.

New ceramic-based friction material

8. Ceramic coating

At present, ceramic coating technology has been successfully applied in automobiles and many other fields, playing an increasingly important role, and the development of its technology has a very broad prospect. For example, thermal sprayed nano-structured ceramic coatings have excellent toughness, wear resistance, corrosion resistance and thermal shock resistance, and can be applied to various mechanical parts of automobiles. Such as pistons, piston rings, cylinder blocks, valve stems, hydraulic struts, bearing pads, pins, cams, lugs, turbine components, etc.

9. Silicon carbide power devices

In the field of electric vehicles, silicon carbide can be used as an important material in charging modules and electric modules in electric vehicles, and has excellent functions such as simplifying the power supply network system, increasing the power supply frequency, reducing the temperature of the device, reducing the size of the device, and improving the efficiency.

10. Battery separator

Lithium-ion batteries are the power source of electric vehicles. With the advancement of science and technology, lithium-ion battery technology and related materials have also developed rapidly, improving the performance of lithium-ion batteries and expanding the application range of lithium-ion batteries, especially in hybrid electric vehicles. Applications include buses, electric vehicles, aerospace, satellites, and energy storage. With the increasing demand for lithium-ion batteries, the requirements for the separator, one of its core components, are getting higher and higher, and high-performance ceramic separators are the main research direction. Pure alumina and boehmite. Although the development direction of lithium batteries is solid-state batteries, lithium battery separators are no longer needed, but according to industry estimates, it will take at least ten years to realize all-solid-state batteries. In the case of continuous safety accidents and extremely immature solid-state battery technology, it is still very necessary to improve the safety of lithium batteries by strengthening the research on ceramic separators.

11. Silicon carbide particle reinforced aluminum matrix composites

Silicon carbide particles reinforced aluminum matrix composites are especially suitable for making anti-wear materials, such as pistons, bearing bushes, etc. Toyota Motor Corporation has used silicon carbide particles reinforced aluminum matrix composites in automobiles to make piston rings and engine connecting rods. In addition, silicon carbide particle reinforced aluminum matrix composites can also be used to manufacture cylinder linings, drive shafts and other automotive parts. At present, the general environment of the automobile industry is to pursue energy saving, greenness and environmental protection. Therefore, when it comes to auto parts, the development trend is "replacing steel with aluminum", which can reduce the weight of the car as a whole and save energy. Therefore, aluminum matrix composites have broad application prospects in the field of transportation.