che 5700 陶瓷粉末處理 ceramic (inorganic) powder processing course contents ceramic products...

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.


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


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


•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


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.


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


* 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


Ordinary Characteristics of Ceramics


•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


•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


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)


• 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


•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


•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


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


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

che 5700 陶瓷粉末處理 ceramic (inorganic) powder processing course contents ceramic products...

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