ChE 5700 陶瓷粉末處理Ceramic (Inorganic) Powder Processing

Textbook

•J.S. Reed, Principles of Ceramic Processing, 2nd edition, John-Wiley & Sons, Inc., 1995

•Major references: - T.A. Ring, Fundamentals of Ceramic Powder Processing and Synthesis, Academic Press, 1996. - Journal articles

Notes: http://ceramic.che.nthu.edu.tw go to “ 上課講義”

Che5700 陶瓷粉末處理

Material Classification

• organic materials (polymers)• Inorganic materials: metal (conductive), ceramic, semiconductors• Bio-materials: pollen• Composites : fiber reinforced plastics, fiber reinforced metal, fiber reinforced ceramics

•by functions: environmental ceramics, electronic ceramics, opto-electronic ceramics etc.

Che5700 陶瓷粉末處理

Definition of ceramics

WD Kingery: The art and science of making and using solid articles which have as their essential components, and are composed in large part of inorganic, nonmetallic materials.

Most common forms: oxides, carbides, nitrides, borides, sulfides; B C N O Si P S

Che5700 陶瓷粉末處理

多元化的精密陶瓷材料Diversity of advanced ceramic materials

Ceramic components of an engine

(upper left counter-clock direction): Flow separation housing; regenerator shield; combustor liner; transition duct; combustion baffle; turbine backshroud; turbine stator; bolt assembly; turbine rotor; outer diffuser housing; inner diffuser housing; turbine shroud; insulation

More functional ceramics in cars

Che5700 陶瓷粉末處理

•Oxygen sensor ZrO2; knock sensor PZT•Backup sensor PZT; electric buzzer PZT•Thermal sensor for water temp., F3O4-CoMn2O3-NiO•Thermal sensor for exhaust gas Al2O3-Cr2O3

•Blower resistor BaTiO3 condenser BaTiO3

•Motor core Fe2O3-Mn2O3 LED GaP•EL ZnS heater for input gas BaTiO3

•Plate of hybrid IC Al2O3

•Fuel level switch Al2O3 – Cr2O3

• insulator for spark plug Al2O3

•Monolithic catalyst substrate MgO-Al2O3-SiO2

From J.S.Reed, 2nd ed. Advanced alumina structural ceramics – very many applications

Classification by function

•Electrical - insulation, ferroelectrics, piezoelectric, fast• ion conduction, superconductors•Magnetic - soft ferrite, hard ferrite•Nuclear - fuel, cladding/shielding•Optical - transparent envelope, light memory, colors•Mechanical - structural refractory, wear resistance, • cutting, abrasive, construction•Thermal - insulation, radiator•Chemical - gas sensor, catalyst carrier, electrodes• filter, coating•Biological - structural prostheses, cement•Aesthetic - pottery, artware, tile, concrete

JS Reed, 2nd ed.Refractory honeycomb cordierite catalyst support

JS Reed, 2nd ed.Magnetic ceramic ferrites used in a wide variety of electrical and electronic communications systems

From TA Ring

Conventional tile production

•(A) raw materials ball mill to grind de-watering (filter press) kneading vacuum forming drying glazing sintering (tunnel kiln) inspection product

•(B) raw materials ball mill to fine size powders spray dryer press forming glazing sintering (roller-hearth kiln) inspection product

Che5700 陶瓷粉末處理

Terra Cotta 秦皇俑

Source: Museum of Qin Terra Cotta Warriors and Horses (ancient ceramic products)

Conventional Raw Materials

•Major applications: construction, bathroom, kitchenware

• Examples (e.g.): clay – kaolin as representative, fine size hydrous aluminum silicate Al2(Si2O5)(OH)4, plasticity of suspension, can be sintered in wide range temperature

•Talc: hydrous magnesium silicate;

•Feldspar: anhydrous aluminum silicate, containing Na, K, or Ca – cheap water-insoluble alkali, often as flux;

•Silica: often as quartz, cristobalite etc.

Che5700 陶瓷粉末處理

Synthetic Materials

• raw materials for fine ceramics: mostly synthetic powders, major components: SiO2, Al2O3, TiO2, ZnO, ZrO2, ferrite, titanate (BaTiO3, PZT), SiC, Si3N4, boride, CdS, ZnS, …..

•Synthetic methods: chemical method (major), plus sol-gel method, solvent evaporation method, precursor decomposition, self-combustion, solid-state reaction method, ….. hope to get ideal powders!!

Taken from Am. Cer. Soc. Bull., Aug, 1999.

Markets and applications of Bayer process alumina

Ceramic Processing or Ceramic Fabrication Process

Che5700 陶瓷粉末處理

* Ordinary processing: powder preparation powder treatment forming sintering final post-fabrication treatment

* processing – microstructure – properties their relationship, processing: e.g. temperature, forming pressure etc. to change microstructure, e.g. grain size, surface area, etc, to obtain different properties – functions we want – e.g. mechanical or chemical properties, etc.

Taken from JS Reed, p.8; conventional alumina, sintered density98%, not transparent; next page product density 99.9%, transparent

Mechanical, optical properties influenced by grain size influenced by particle size of raw materials, forming technique, sintering condition, etc. processing variables

From JS Reed, 2nd ed.

porous ceramics: filtration 、 temperature resistant characteristics influenced by composition and pore size distribution Influenced by raw material/forming technique/sintering

From JS Reed, 2nd ed.

Ordinary Characteristics of Ceramics

Che5700 陶瓷粉末處理

•Advantages: Inert, high strength, tolerant of high temperature, functional properties

•Disadvantages: brittle, reliability (due to inhomogeneity or irregularity), reproducibility, cost and productivity

• New ceramics, fine ceramics, advanced ceramics

Powder Processing

Che5700 陶瓷粉末處理

•Total process concept: Pn(P n-1 (…..P2(P1(S)))) • -- every processing will change some microstructure of material to reach the final state

• Intrinsic Character: •composition: chemical, crystal phase•structure: grain size, crystal perfection, porosity

• Extrinsic (behavior) properties: •E.g.: tensile strength, magnetic permeability, thermal expansion, resistance to thermal shock, resistance to corrosion, etc.

Lots of Properties

Che5700 陶瓷粉末處理

Mechanical types: strength, toughness, low creep, low friction, wear resistance, corrosion resistance, thermal shock resistance, matched thermal expansion assemblies;

Electrical/optical/magnetic types: dielectric (high or low); thermal conductivity, electrical conductivity, temperature-dependent resistivity, piezoelectric , optical absorption, chemical electrical effect, voltage-sensitive resistivity; Others: thermal (insulation), biological, aesthetic (美學 ), chemical (e.g. sensor, electrode, etc.)

Bioceramics (brief)

Che5700 陶瓷粉末處理

• Classification:•Bio-inert (e.g. Al2O3, ZrO2);•Resorable: calcium phosphate•Bioactive (surface reactive): hydroxyapatite (HA), bioactive glass;•combination: e.g. coating or composite

•Applications: bone, teeth, joint etc. artificial materials; competitors: polymer, metal;•Desired characteristics: biocompatibility, strength (complex stress condition within human body)

processing- microstructure – property

Che5700 陶瓷粉末處理

•actions in processing materials respond and change develop microstructure showing desired properties for applications

•(a) grinding – fracture mechanics of powders – morphology & size distribution – surface energy, rheology of particle in fluid

•(b) sintering – solid state reactions, phase transformation, mass transport, grain boundary mobility – grain size & distribution, pore size & distribution, nature of grain boundary – all kinds of mechanical/chemical/electrical properties

C: composition; M:microstructure; PD: process defects; SD: service defects

Need to do more analysis on microstructure to improve reliability, reduce cost

Origins of non-uniformity

Che5700 陶瓷粉末處理

•composition: from mixing or reaction

•Particle size distribution

• agglomerates

•Forming process: e.g. during pressing

•sintering: e.g. temperature distribution in furnace

non-uniformity will pass on to next step, to final product and therefore properties of products

From JS Reed, 2nd ed.

Common processing steps: Raw material selection, grinding, size classification, purification and blending, paste preparation, dewatering, green body formation, drying, binder burn-out, and sintering

Fig. 1.5 of the textbook by JS Reed

Inter-discipline knowledge

•Raw materials chemical & physical treatments IDEAL POWDER ……chemical and chemical engineering technology

•Ideal powder forming sintering post-fabrication treatment DESIRED PROPERTIES …… material technology

•Desired properties characterization/testing device FINAL PRODUCT …….. Electrical/mechanical/chemical/material engineering

Che5700 陶瓷粉末處理

General Concepts of Ceramic Powder Processing

Taken from TA Ring, p.4-5 (a) Uniformity in the microstructure of a single phase ceramic is better for electrical and mechanical properties; (b) Microstructural inhomogeneities that occur in casting a green body remain (or even get larger) during drying, binder burn-out and sintering. (c) Smaller powders sinter to give smaller grains that give a stronger ceramic piece. Herring scaling law for sintering: particle size r1, r2, sintering time relationship t1, t2: t2 = [r2/r1]n t1; where n –related to sintering mechanism, e.g. volume diffusion, n = 3 small mean size, easy sintering

Science of Ceramics Processing

Reactions leading to the formation of particles (e.g. nucleation, growth,…)

dispersion of particles in solution: interfacial phenomena;

rheology during forming processes, particle packing

sintering: diffusion, grain growth, structural development, etc.

Ceramic Museum in Taipei County

website: http://www.ceramics.tpc.gov.tw address: 台北縣鶯歌文化路 200 號 (02-86772727) First Taiwan International Ceramic Arts Biannual Exhibition, 2004/2/13