ChE 5700 Ceramic Powder Processing

Kan-Sen Chou

Material Classification

• Organic materials (small molecule, polymers) from oil/gas/coal• Inorganic materials: metal (conductive), ceramic, semiconductors; from minerals• Bio-materials: pollen; renewable source• 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

Material Research

• Processing what you do; innovative

• Microstructure changes in basic characteristics in material

• Property performance you desired; sometimes one may have to compromise among different properties

• Example: nickel hydroxide powder to electrode to battery

Course Contents (4 sections)

• Introduction: importance of this subject, various products

• Processing: Various methods to synthesize powder; Various techniques (steps) to process these powder into objects

• Microstructure: Various characteristics of powder: size, shape, crystallinity…..

• Property: strength, hardness, ..many other opto-electric properties; related to its applications

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 articlesNotes: http://ceramic.che.nthu.edu.tw go to “ 上課講義”Evaluation: homework, final oral and written reports

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

* Different sizes/ different shapes

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

Terra Cotta 秦皇俑

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

From TA Ring

Conventional tile production

•(A) raw materials ball mill to fine particles de-watering (filter press) kneading (paste) 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

Conventional Raw Materials

•Major applications: construction, bathroom, kitchenware

• Examples: 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, ITO, IZGO, …..

•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 synthesis powder treatment forming sintering final post-fabrication treatment

•processing – microstructure – properties • powder synthesis size mechanical• powder treatment shape/porosity electrical• forming of objects surface area etc• 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 (operation) will change some microstructure of material (material respond) to reach the final state

• Intrinsic Character: (microstructure) •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);•Resorbable: 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)

Examples on processing- microstructure – property

Che5700 陶瓷粉末處理

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

•(b) sintering – T & t & atmosphere 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: many different operations as shown in this diagram

Fig. 1.5 of the textbook by JS Reed

Science of Ceramics Processing what happened on the microscale

Reactions leading to the formation of particles (e.g. chemical reaction, particle 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 New Taipei City

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