Analysis of Nitride Ceramic Type
1. silicon nitride ceramics
1.1 basic characteristics of silicon nitride
Aα-Si3N4: low temperature type, is needle-like crystals. β-Si3N4: high temperature type, is a granular crystal. The high purity silicon is nitrided at 1200-1300 ° C to obtain white or off-white α-Si3N4, and β-Si3N4 can be obtained when nitriding at about 1450 ° C.
A? -Si3N4 is heated at 1400 to 1600C, and is converted into? -Si3N4.1900C. Si3N4 strength and toughness is better than SiC, but the oxidation resistance and high temperature strength less than SiC.
1.2 Preparation of silicon nitride
(A) Synthesis of silicon nitride powder:
Table 1 Synthesis of Si3N4 powder
(B) sintering aids: MgO, Al2O3, Y2O3
(C) Sintering method: atmospheric sintering, pressure sintering, hot pressing sintering, reactive sintering, hot isostatic pressing sintering
1.3 Properties and Application of Silicon Nitride Ceramics
(1) Si3N4 ceramic material with high temperature wear resistance, in the ceramic engine for the preparation of gas turbine rotor, stator and scroll tube; anhydrous cold ceramic engine, with hot pressing Si3N4 to do the piston cap; with reactive sintering Si3N4 The burner, which can also be used as a spark plug for a diesel engine, a piston cover, a cylinder liner, a sub-combustion chamber, and a piston-turbine modular aero engine.
(2) Si3N4 ceramic material has the characteristics of good wear resistance, high strength and low friction coefficient. The bending strength is high and the hardness is also high. At the same time, the friction coefficient is small, with self-lubricating property and small friction coefficient (only 0.1). So it can be widely used in machinery industry, such as manufacturing bearings, ball, roller, ball seat, high temperature bolts, molds, plunger pumps, sealing materials.
(3) Si3N4 ceramic materials are chemically stable, corrosion of all inorganic acids and certain alkaloids other than hydrofluoric acid, and are not protected by lead, aluminum, tin, silver, brass, nickel and other molten metal alloys. Infiltration and corrosion. So it can be widely used in the chemical industry to prepare corrosion-resistant wear-resistant parts, such as ball valves, sealing rings, filters, heat exchanger parts, pipes, catalyst carriers and so on.
(4) Si3N4 ceramic material high temperature resistivity is relatively high (1013-1014Ω · cm), on the one hand can be used as a better insulating material; also can be used for electronics, military and nuclear industry, such as switch circuit substrate, film Capacitors, high temperature insulators, radar radomes, missile nozzles, barrel lining, nuclear reactor support, and so on.
In addition, Si3N4 ceramics can also be used as heat engine materials, cutting tools, advanced refractory materials.
2. Boron nitride ceramics
Boron nitride (BN) has two crystal forms: cubic BN and hexagonal BN, in high temperature and high pressure hexagonal BN can be transformed into cubic BN.
Cubic boron nitride (C-BN): its structure and performance and diamond similar to its hardness after the diamond, the chemical inertness than the diamond and hard alloy. The main uses of C-BN are: cutting tools, abrasives and abrasives, which can be used to cut all metal and nonmetallic materials including ferrous metals and can be used for finishing.
Hexagonal boron nitride (H-BN): its structure and performance and graphite similar, also known as white graphite, is a good high-temperature lubricating materials and high-temperature electrical insulation materials. H-BN does not react with most metals and is not wettable and can be used as a crucible or pipe for melting and transporting metal. Can produce high-temperature structural components, such as rocket combustion chamber lining, the spacecraft's thermal shielding, magnetic fluid generator, such as corrosion-resistant pieces. But also as a high temperature, high frequency, high voltage insulation parts, semiconductor package cooling floor, nuclear reactor neutron absorption and shielding materials.
3. Aluminum nitride ceramics
The basic properties and uses of aluminum nitride ceramics: AlN is hexagonal crystal, density 3.26g / cm3, atmospheric pressure 2450 ℃ sublimation decomposition, Mohs hardness of 7 to 9. The biggest feature is the high thermal conductivity, up to 200W / m · K or more, thermal expansion coefficient is small, high strength, good electrical insulation properties, is the ideal substrate material for high temperature structural parts and heat exchangers.
Alumina ceramic sintering process: in the nitrogen at 1800 ~ 1900 ℃ firing, sintering aids for the SiO2, Y2O3, CaO, ceramic strength up to 200 ~ 300MPa.
4. Sialon (sialon) ceramics
Ceramics are the solid solution of Si3N4 and spinel AlN · Al2O3. The crystal structure is the same as β-Si3N4. The mechanical properties are similar to that of β-Si3N4. The hardness, strength and thermal conductivity are slightly lower than Si3N4, but the toughness is better than Si3N4.
Opinions of the State Council on Further Expanding and Upgrading of Information Consumption for Sustainable Exploitation of Domestic Demand
The provinces, autonomous regions and municipalities directly under the Central People's Government, the State Council ministries and commissions, the institutions directly under:
In recent years, with the deep integration of Internet technology and economic society, the rapid development of information consumption in China is from the online to speed up the integration of online and offline new forms of change, the network speed down the cost of further advance, the growing consumer, Gradual expansion, rapid adjustment of the model, driven by rapid growth in other areas of consumption, has become the most active innovation, the most rapid growth, the most extensive radiation in one of the economic areas, to stimulate domestic demand, promote employment and lead the industry to play an important role in upgrading. But at the same time, China's effective supply of information consumption is still insufficient innovation, domestic demand has not yet fully released, the consumer environment needs to be optimized. To further expand and upgrade information consumption, the continued release of dynamic development and domestic demand potential, the following views are made.
First, the overall requirements
(A) guiding ideology.
Fully implement the spirit of the Sixth Party Congress and the Eighth Central Committee, the Fourth, the Fifth, the Sixth Plenary Session of the Eighth National Congress of the Communist Party of China, thoroughly implement the new spirit of the new series of ideas of the general secretary of Xi Jinping, and earnestly implement the Party Central Committee, The State Council decision-making arrangements, and promote the "five in one" overall layout and coordination to promote the "four comprehensive" strategic layout, insist on steady progress in the overall tone, firmly establish and implement innovation, coordination, green, open, shared development concept , To promote the supply side of the structural reform as the main line, optimize the information consumption environment, and further increase the speed of the network to speed up efforts to accelerate the market vitality, and actively expand the information consumption of new products, new formats, new models, expand information consumption coverage, Improve the supervision, improve the network security system, build information consumption upgrade version, and constantly release the people's growing consumer demand, promote sustained and healthy economic and social development.
(B) the basic principles.
Adhere to innovation drive. To promote the integration of information consumption and public entrepreneurship, "Internet +" deep integration, to encourage core technology research and development and service model innovation, to promote a new generation of information technology to the wide penetration of consumer areas, to create more effective supply of consumer upgrades, driven multi- Personalized information consumption development.
Adhere to demand pull. To meet the people's expectations and economic and social development needs as the starting point and the foothold, to speed up the expansion and upgrading of information consumption, and promote information products supply structure and demand structure effective match, consumer upgrades and effective investment benign interaction, with safe, convenient and rich information Consumption to help the economy to upgrade and improve people's livelihood.
Adhere to collaborative linkage. To enterprises as the main body, to promote the coordinated development of information consumption industry chain, strengthen the network, platform, payment, logistics and other support capacity building, build a sound information consumption ecological system. To promote the development and security, and continuously optimize the credit security, market environment and the protection of rights and interests, to create a "consumer, dare to consume, willing to consume" environment, the formation of government, business, consumer coordination and good development pattern.
(Iii) development goals.
By 2020, the scale of information consumption is expected to reach 6 trillion yuan, an average annual growth of more than 11%; information technology in the consumer sector significantly enhance the leading role in the depth of information products to expand the border, information services significantly improved, 15 trillion yuan, the information consumption to benefit the broad masses of the people. Information infrastructure to achieve world-leading level, "broadband China" strategic objectives to achieve a comprehensive, high-speed, mobile, safe, ubiquitous new generation of information infrastructure, network speed to achieve significant results. Based on the rapid growth of the new consumption of the network platform, online and offline interaction between the consumption of new ecological development and growth. Public data resources open and shared system is basically established, for enterprise
The Ministry of Environmental Protection will issue a document to resolutely implement the “ten-point water plan”, and water pollution control in industrial agglomeration areas must be put into practice
It’s learned from the Ministry of Environmental Protection that the Ministry of Environmental Protection will print and issue The Program to Promote the Water Pollution Control Task in Industrial Agglomeration Areas and require taking hard measures to implement the task of the “ten-point water plan”. For provincial or higher-level industrial agglomeration areas that fail to finish the task on time, the approval of their construction projects increasing water pollutant discharge shall be suspended and their park qualifications shall be revoked according to relevant regulations.
Relevant official of the Water Environment Management Division of the Ministry of Environmental Protection told the media on 6th that the progress in some places to implement water pollution control work in industrial agglomeration area is too slow and there is still too much gap from the requirements of the time limit required in the “ten-point water plan. “Industrial agglomeration areas are important carriers of industrial development. To establish centralized sewage treatment facilities and install automatic online monitoring devices are the bottom line of water pollution control in industrial agglomeration areas”, said the official.
The Program to Promote the Water Pollution Control Task in Industrial Agglomeration Areas to be printed and issued puts forward that all local governments and park administration as the main body of the responsibility shall go all out to complete the requirements of the “ten-point water plan”; all leading responsible departments shall intensify scheduling and information disclosure; all levels of environmental protection departments shall organize and coordinate relevant departments to go to the site for supervision and guidance; and the Ministry of Environmental Protection should strengthen supervision and guidance together with relevant ministrations.
As required in the “ten-point water plan”, before the end of 2017, all industrial agglomeration areas should establish centralized sewage treatment facilities and install automatic online monitoring devices in accordance with the regulations; especially the Beijing-Tianjin-Hebei, the Yangtze River Delta, the Pearl River Delta and relevant areas should complete one year in advance.