1. Che5700 陶瓷粉末處理 Powder Synthesis Solid state method:  Solid-solid reaction; decomposition of solid; oxidation or reduction of solid Liquid phase method:  Chemical precipitation, co-precipitation, evaporative salting out, hydrothermal, etc. Gas phase method:  Gas phase reaction, gas-solid reaction, evaporative condensation Others:  Solvent removal (spray drying, freeze drying), sol-gel, etc

2. Ideal Powder Che5700 陶瓷粉末處理 Ideal powder:  spherical, submicron (or nanometer)  Narrow size distribution  No agglomerate  Uniform composition, high purity

3. Many examples

4. Some examples Che5700 陶瓷粉末處理 Si 3 N 4 : from Si nitridation; or SiO 2  reduction + nitridation PLZT: precipitation + spray drying ZrO 2 : hydrolysis of metal salts Y 2 O 3 : emulsion precipitation SiC: plasma synthesis, vapor phase reaction Yttria: homogeneous precipitation TiN, AlN: combustion synthesis

5. One way to get powder of desired composition: from minerals, simple physical separation, + chemical purification to get products. Purity: often not very high; used in conventional ceramic industry

6. From bauxite ( 鋁礬土 ): Bayer process to produce alumina; feed  grinding  add alkaline & mixng  digester  thickener  filter  precipitation  crystallization + classification  filtration  drying and calcination  product

7. Extract zirconium from zircon Che5700 陶瓷粉末處理 Zircon: ZrO 2.SiO 2 Method one: high temperature melting and decomposition (use arc furnace or plasma arc) > 1750 o C;  quench  use acid to dissolve ZrO 2 or alkaline for SiO 2 Method two: zircon + NaOH  high temperature reaction  Na 2 ZrO 3 + Na 2 SiO 3  + water  filtration to remove Na 2 SiO 3.nH 2 O  crude sodium zirconate  + HCl  filtration to remove SiO 2 colloids  get ZrOCl 2 – HCl solution  evaporative concentration  crystallization  filtration to remove impurities (Fe, Ti, Na, Al, HCl etc)  get ZrOCl 2 8 H2O  repeat and secondary crystallization  high purity ZrOCl 2 8 H 2 O  calcination  zirconia

8. Magnesium zinc ferrite

9. Preparation of high purity alumina Che5700 陶瓷粉末處理 High purity: > 99.5%; (1)Selective crystallization: get ammonium alum or ammonium alum carbonate hydrate (AACH) first, repeated dissolution-crystallization, to remove impurities, e.g. Na, Mg, Ca, Fe, Ti, SiO 2 ; NH 4 Al(SO 4 ) 2 12 H 2 O (2)Distillation method: Al metal as source, reaction to get AlR 3 or alkoxide Al(OR) 3, then remove impurity by distillation, calcination to get oxides. (3)Spark discharge: high purity Al as electrode, under high electrical voltage, spark discharge to get oxide

10. Preparation of high purity alumina(2) Che5700 陶瓷粉末處理 (4)Chemical reaction: ethylene chlorohydrin process, sodium aluminate solution as source, add organic acid ClCH 2 CH 2 OH, slow neutralization reaction to get Al(OH)3, impurity such as Na, Si, Fe difficult to enter oxide lattice; by-product ethylene oxide, may react with HCl  to get ethylene hydrin to save money (5) Modified Bayer process : add large silica particle during calcination, to trap evaporated Na 2 O to remove it; or flowing HCl to form soluble NaCl to remove it;

11. Transparent Alumina One potential application: to be used in HID (high-intensity discharge) lamp; for projectors, etc. anti-corrosive, heat resistant, good strength (better than fused silica) HID lamp: greater light output/watt electrical input

12. Opaque alumina: purity > 99.5%; grain size ~ 0.55 μm, residual porosity 0.3%; transparent alumina: residual porosity < 0.03% (taken from J. Am. Cer. Soc., 89(6), 1985-1992, 2006)

15.  Different method: competitive in terms of quality and cost