材料概论(陶瓷材料)

We live in a world of material possessions,that largely define our social relationships and economic quality of life .we distinguish six categories that encompass the materials available to practicing engineers:metals,ceramics,glasses,polymers,composites,and semiconductors.
Ceramics is the most ancient material that widely used as the engineering material since about 8000 years ago.and it also be developed for the airspace and electronics industries.Ceramics can be divided into two categories:structual ceramic and fuctional ceramic . the raw materials of trantional ceramic contains clay,kaolinite,montmorillonite and other materials that can improve and change the property of ceramics.there materials are abundent and economical,many of the traditional ceramics that we use are made of these materials called silicates.With the development of the ceramic,it has been more and more advanced .
When we first discuss a material,we often talk about it’s structual and property and then application.The structure of ceramic cotains three phases:crystal phase,glass phase and gaseous phase(i.e.pore)Because it’s crystal structual,ceramics often called crystalline ceramics by looking at the SiO2-based silicates.It’s network of the structure contribute to the property of it’s s pecial hardness and excellent temperature resistance and other phsical and chemical properties.The role of glass phase is to fill the crystalline gap,improve the density,lower the sintering temperature and
inhibit grain growth.The gaseous phase is residue after sintering.
The application of ceramics depended on it’s proprety.In this short essay,I only talk about the advanced ceramics.According to it’s application ,ceramics can be divided into structural ceramic and fuctional ceramic. the two categories has many similarities about their elements and properties.
Nonsilicate oxide ceramics include some tranditional materials ,such as alumina(Al2O3),magnesia(MgO) and zirconia(ZrO2),which are the primary candidates for some advanced structural applications.Some ceramics even have the clectronic property and other fuctional such as pyroelectricity,piezoelectricity after mixed some impurities such as barium titanate(BaTiO3),lead titanate(PbTiO3) and tungsten oxide(WO3). Especially the aluminum oxide ceramics are high-temperature-resistant materials that play crucial role in industry.
Nonoxide ceramics,such as silicon carbide ,silicon nitride and aluminium nitride, The stable crystal structure contribute to extraordinary hardness and the resistance to high-temperature.Beside,nonoxide ceramics also has excellent insulativity , self-lubrication and corrosion resistance.Thanks to this kind of ceramics ,the efficiency and life of engine has been improved .
Ceramics as a kind of tranditional material had got a great develop such as the ceramic matrix composite(CMC),by joining the
particles ,whiskers,and layered materials such as continuous fiber reinforcement with ceramic substrate to form composite materials.It’s easy to predict that ceramics will be more advanced and widely used in the future.。