Many people may know that Mingrui Ceramics is an advanced ceramic manufacturer, but they do not know what advanced ceramics mean. Advanced ceramics generally refer to ceramics that use high-purity, ultra-fine synthetic or selected inorganic compounds as raw materials, have precise chemical composition, precise manufacturing and processing technology and structural design, and have excellent characteristics.
Advanced ceramics can be divided into structural ceramics with high strength, high hardness, high temperature resistance, corrosion resistance, and oxidation resistance, and functional ceramics with electrical properties, magnetic properties, biological properties, thermal sensitivity and optical properties. Advanced ceramics are widely used in the fields of high temperature, corrosion, electronics and optics. As an emerging material, it is unique in the field of materials with its excellent performance. It is highly valued by people and will play an important role in the future society.
1. Structural ceramics
Structural ceramics mainly include: cutting tools, molds, wear-resistant parts, pump and valve parts, engine parts, heat exchangers and armor. The main materials are silicon nitride (Si3N4), silicon carbide (SiC), zirconium dioxide (ZrO2), boron carbide (B4C), titanium diboride (TiB2), alumina (A12O3) and Sialon.
(1) Si3N4-based ceramic materials
C fiber reinforced Si3N4-based ceramic material, using ZrO2's transformation effect to prevent cracks due to the mismatch between the thermal expansion coefficient of the fiber and the matrix, and the fracture toughness of the obtained composite material is increased by 5 times. Silicon nitride ceramics have become one of the most promising cutting tools in high-performance ceramics due to their excellent comprehensive properties and rich resources. Approximately 140 tons of silicon nitride powder are used for tool manufacturing each year, worth about 300 million US dollars.
(2) Silicon carbide-based ceramics
The density of the silicon carbide ceramic prepared by the hot pressing process can be close to the theoretical density, and the bending strength can reach 500-600 MPa even at a high temperature of about 1400°C. The C-fiber reinforced silicon carbide composite material prepared by the CVI method has a strength of 520 MPa and a fracture toughness of 16.5 MPa·m. Adding 25vol% TiB silicon carbide composite ceramics, if the initial particle size is strictly controlled, the strength can reach 888MPa and the fracture strength can reach 8.8MPa·m. It can be said that silicon carbide is the strongest material in high-temperature air, and its thermal conductivity is second only to beryllium oxide ceramic materials. There are many companies in China that produce silicon carbide powder, a large part of which is exported, but mainly low-grade silicon carbide powder used in the manufacture of refractory bricks. Eastern Europe has a production capacity of 150,000 tons/year, and North America’s production capacity is 100,000 tons/year. The price of high-purity, high-activity silicon carbide fine powder is very high, at 14-40 US dollars per kilogram, and the annual demand is about 15 million US dollars. This powder is used to manufacture high-performance silicon carbide ceramics.
(3) Zirconia toughened ceramics
Zirconia toughened ceramics have made significant progress in the research of structural ceramics, and there are many types of toughened ceramics. At present, the additives that can stabilize zirconia are: magnesium oxide, calcium oxide, lanthanum oxide, and yttrium oxide , Cerium oxide and other single oxides or their composite oxides. In addition to stable zirconia, the toughened materials include oxide ceramics such as alumina, thorium oxide, spinel, and mullite. Adding 16 vol% zirconia to the alumina for toughening treatment, the strength of the material obtained is 1200 MPa, and the fracture toughness is 15.0 MPa·m. Zirconia toughened ceramic materials have the highest strength and fracture toughness at room temperature, and will focus on improving their high-temperature performance in the future.
2. Functional ceramics
Functional ceramics are knowledge- and technology-intensive products. People have discovered oxide conductors, solid electrolytes, piezoelectric, nonlinear optical materials, ferrites, memory materials, solar cells, high-temperature oxide superconductors, etc. With the development of electronic products that are light, thin, short and small, multi-functional, high-reliability, high-density surface, and high integration, functional materials also have continuous development.
There are many varieties of functional ceramics. This type of material has many excellent functions such as microwave dielectric properties, gas sensitivity properties, superconducting properties, resistance gradient properties, ferroelectric properties and its phase change behavior, multilayer driving properties, relaxation properties, etc. , The application is very wide.
(1) Electronic insulating materials
At present, the commonly used electronic insulation material at home and abroad is Al2O3. In recent years, new electronic insulating materials, such as AlN ceramics, have excellent properties such as high strength, high insulation, low dielectric constant, and high thermal conductivity, and their thermal expansion coefficient can match that of monocrystalline silicon. They are mainly used It is used as a heat dissipation substrate for large-scale integrated circuits and power module circuits.
(2) Dielectric materials
The dielectric materials of ceramic capacitors used for tuning circuits, protecting logic and memory cells are mostly BaTiO3-based materials. In addition, there are high-dielectric composite perovskite materials to develop high-dielectric materials with a dielectric constant of up to 105 at a frequency of 105Hz. At present, the emergence of grain boundary layer capacitors has increased the dielectric constant of conventional ceramic capacitors several times or even dozens of times.
(3) Piezoelectric ceramic materials
Commonly used piezoelectric components: sensors, gas igniters, alarms, audio equipment, medical diagnostic equipment and communications, etc. The usual piezoelectric material is PZT, and the new types of piezoelectric ceramic materials mainly include: high-sensitivity, high-stability piezoelectric ceramic materials, electrostrictive ceramic materials, pyroelectric ceramic materials, etc.
(4) Magnetic ceramic materials
Magnetic ceramic materials can be divided into two types: hard magnetic and soft magnetic materials. The former is not easy to be magnetized or lose its magnetism. Representative hard magnetic materials are ferrite magnets and rare earth magnets, which are mainly used for magnets and magnetic storage elements. Soft magnetic materials are easy to magnetize and demagnetize, and the direction of the magnetic field can be changed. It is mainly used for electronic components that respond to alternating magnetic fields.
(5) Superconducting ceramic materials
Since a major breakthrough in the study of superconducting ceramics in the 1980s, the research and application of high-temperature superconducting ceramic materials have attracted much attention. In the past ten years, China's research in this area has been at the advanced level in the world. At present, the application of high-temperature superconducting materials is moving towards high-current applications, electronics applications, and diamagnetism.
(6) Anti-bacterial ceramic materials
Anti-bacterial ceramic materials are a new generation of functional materials produced with the development of science and the civilization of society. Inorganic anti-bacterial agents can be divided into three categories according to the mechanism of acting on microorganisms: one type is to fix silver, copper, zinc and other anti-bacterial metals or their ions on zeolite, apatite, etc. by physical adsorption or ion exchange. It is made of silica gel, glass and other inorganic material carriers; the second type is titanium dioxide particle photocatalytic anti-bacterial agent, titanium dioxide can turn oxygen molecules into active oxygen under light, so that water produces active oxygen free radicals to play an antibacterial and sterilization effect. ; The third category is anti-bacterial materials with far-infrared radiation function. Far-infrared has limited anti-bacterial function. Therefore, this material must be used in conjunction with the first two materials to have better application value.
