1. Synthesis,Properties and Uses. CERAMICS

2. WHAT ARE CERAMICS?? Ceramics are inorganic materials with many different properties generally known for their strength and heat resistance. They may be amorphous, partly crystalline or fully crystalline. They are either formed from a molten mass that solidifies on cooling, formed and matured by the action of heat, or chemically synthesized at low temperatures using, for example, hydrothermal or sol-gel synthesis. 3. BASIC MANUFACTURE PROCESS MILLING BATCHINGMIXINGFORMING DRYING FIRING ASSEMBLY 1.Milling Ceramic materials are reduced by size for efficient processing. 2.Batching It is the process of weighing the oxides according to their requirement and preparing them for mixing and drying. 4. 3.Mixing All materials are churned together and wetted most of the times to enable appropriate shaping 4. Forming It Is making the mixed material into shapes. 5.Drying It is removing the water or the binding component from the formed material. 6.Firing It means giving the final form to the product. 5. BASIC CLASSIFICATION OF CERAMICS: 6. ALUMINA Alumina or aluminium oxide( Al2O3 )is one of the most widely used oxide ceramic. It naturally occurs in its crystalline form -Corundum. How it is produced? 1. First Bauxite is purified by the Bayer process: AlO(OH) + H2O + NaOH NaAl(OH)4Al(OH)3 + NaOH NaAl(OH)4 Except for SiO2, the other components of bauxite do not dissolve in base. Upon filtering the basic mixture, Fe2O3 is removed. When the Bayer liquor is cooled, Al(OH)3 precipitates, leaving the silicates in solution. NaAl(OH)4 NaOH + Al(OH)3The solid Al(OH)3 Gibbsite is then calcined (heated strongly) to give aluminium oxide 2Al(OH)3 Al2O3 + 3H2O. 7. PROPERTIES AND USES OF ALUMINA PROPERTIES: Electrical insulator Aluminium oxide is insoluble in water USES It is a major component, of the cue tip "chalk" used in billiards. Also it is used in some CD polishing and scratch-repair kits Used in ballistic armoured vests and can repel large- calibre rifle fire. Alumina can form glass if it is alloyed with calcium oxides, but its difficult to produce bulk quantities due to unavailability. 8. SILICON CARBIDE It is also known as carborundum. 9. PRODUCTION 1.-SiC: The primary reaction is: SiO2(Sand) + 3C SiC +2CO { SiO2 +C SiO (g)+CO (g) SiO (g)+2C SiC+CO (g) } At 2000-3000 degree Celsius 2.-SiC: SiCl4 + CH4 SiC+4HCl At 1000-1500 degree Celsius 10. SILICON: PROPERTIES AND USES PROPERTY USE Durability and low cost of the material High sublimation temperature of SiC High thermal conductivity, and high maximum current density High voltage-dependent resistance Grinding, honing, water-jet cutting Bearings and furnace parts. Semiconductor material in electronics. Lightning arresters 11. OTHER APPLICATIONS OF SIC Grains of silicon carbide are sintered to form ceramics which are used in car brakes , ceramic plates and protective vests. Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs, as it is able to withstand extreme temperatures. 12. ZIRCONIA(ZIRCONIUM DIOXIDE) Zirconia is nothing but Zirconium dioxide (ZrO2). It is produced by calcinating zirconium compounds, exploiting its high thermal stability. PROPERTIES: Monoclinic crystal structure at room temperature Thermal Insulator and very hard. 13. APPLICATIONS OF ZIRCONIA CUBIC ZIRCONIA (CZ) IS THE CUBIC CRYSTALLINE FORM OF ZIRCONIUM DIOXIDE (ZrO2). It is a excellent replacement for diamonds as it is almost similar to it. Used as an oxygen sensor in exhaust systems 14. FIBRE REINFORCED CERAMICS Consists of Ceramic fibers embedded in a ceramic matrix, thus forming a ceramic fiber reinforced ceramic (CFRC) material. PROCEDURE FOR FORMATION: 1. Lay-up and fixation of the fibers, shaped as the desired component 2. Infiltration of the matrix material 3. Final machining 15. IMPORTANT CERAMIC APPLICATIONS Silicon nitride parts are used in ceramic ball bearings. Their higher hardness means that they are much less susceptible to wear. Boron carbide and silicon carbide are used in fixed amounts to manufacture cockpit of planes. Artificial bone and teeth. High-temperature reusable surface insulation (HRSI) in Space shuttles Most widely used in Pottery Ceramic coatings are applied to engines 16. AN INTERESTING FACT In 1980s, Toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 3300 C. Ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. Fuel efficiency of the engine is also higher at high temperature. In a metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Despite all of these desirable conventional properties, such engines are not in production because the manufacturing of ceramic parts in the requisite precision and durability is difficult. Imperfection in the ceramic leads to cracks, which can lead to potentially dangerous equipment failure. 17. ADIABATIC ENGINE 18. THANK YOU FOR YOUR KIND ATTENTION