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Processing of CeramicsLalita El Milla

Sifat GlassTidak mengalami solidifikasi sebagaimana kristalinDlm proses cooling, viscous glass meningkat Volume glass menurun kurva menurun mencapai glass transisi temp = TgDibwh Tg material glassDiatas Tg supercooled liquid

Ttk yg penting dlm fabrication & proses glass :Melting point.Viscositi 10 Pa-s : glass cukup cair untuk disebut sebagai liquid.2. Working point.Viscositi 103 Pa-s : glass mudah dideformasi pd viscositi ini.Softening point.Viscositi 4 x 106 Pa-s : maximum temperature at which a glass piece may be handled without causing significant dimensional alterations

Annealing point .Viscositi 1012 Pa-s : atomic diffusion is sufficiently rapidStrain point. Viscositi 3 x 1013 Pa-s : Temp dibwh strain point fraktur tjd sblm deformasi plastik. The glass transition temperature will be above the strain point

Glass-forming dilakukan di area working range (Antara working point dg softening point).

Glass FormingPembentukan glass hrs homogen & bebas pores sifat mekanis dan estetisHomogeniti material complete melting & mixing.

Metode ;PressingBlowingDrawingFiber forming

4 Methode forming glass :

Pressing.Cth : plat & piring.Glass ditekan di dlm mold besi yg dilapisi graphite kmd dipanaskan untuk mendptkan perm yg rata.

Blowing.Cth : kendi glass, botol, & bohlam lampu.Sepotong glass dimasukkan ke dlm parison mold (btk sementara) mechanical press pressure air.

Drawing.Cth : long glass : lembaran, tabung, batangan, & fiber.Lembaran glass masuk ke hot rolling flatness annealing.

Fiber forming.Teknik drawing yg menggunakan byk orifice kecil dlm prosesnya.

Heat Treating GlassAnnealing

Material ceramic saat didinginkan terjadi thermal stress fraktur extreme cases thermal shock

Mencegah thermal stress annealing dibiarkan perlahan mendingin di temp ruang.Glass Tempering

Thermal tempering Strength glass diperkuat inducing compressive residual surface stresses

Glass dipanaskan dibwh temp softening point dibiarkan dingin residual stress timbul Krn perbedaan cooling antara surface dgn interior glass

Di surface mendingin lbh cepat temp dibwh strain point rigidDi interior mendingin lbh lambat temp diatas strain point plastik.Stlh glass mendingin di temp ruang compressive stress di permukaan & tensile stress di interior

Ceramic dapat crack bila diberikan tensile stress di permukaannya.

Temper glass digunakan untuk aplikasi yg membutuhkan strength yg tinggi, cth pintu kaca besar, kaca depan mobil, & lensa kacamata.Tehnik Fabrication of ClayHYDROPLASTIC FORMINGClay + air plastik & lunak molded without crackingyield strength rendahTeknik Hydroplastik Forming = teknik extrusion pd logam.Batu bata, pipa, ceramic blok, & ubin

SLIP CASTINGSlip = suspensi clay &/atau material nonplastik lain dlm air.Suspensi dituang ke dlm mold air dr slip diserap kedlm mold meninggalkan lap solid di ddg mold proses terus menerus seluruh kavitas mold mjd solid.atau solid mencapai ketebalan yg diinginkan

Sifat slip : graviti tinggi, sgt fluid & dpt mengalir.

Drying & FiringDRYINGClay dry some shrinkage.Stage drying partikel clay dikelilingi & dipisahkan o/ lap tipis air water berkurang pemisahan interpartikel berkurang menyisakan shrinkage.Drying difusi molekul air bergerak ke permukaan evaporation.Kec evaporation > kec difusi dry surface lebih cepat dari interior (shrink)

Kec evaporation dpt dikontrol dgn :TempKelembabanKec aliran udaraAir dlm clay shrinkage TEKNIK POWDER PRESSINGuntuk pembuatan clay & nonclay,

3 prosedur powder pressing :Uniaxial.Caviti die diisi dg powder. Powder dipadatkan dg memberi pressure diatas die. Bag atas dilepaskan dg menaikkan tekanan dr bwh. Material yg terbtk dikeluarkan dr tempatnyaIsostatik/ hidrostatik.Powder material dibungkus karet & ditekan dg cairan.Hot pressing.Powder pressing & heat treatment dibentuk bersamaan.

Mikrostruk powder berubah selama firing :Proses Sintering :Stlh di press, byk partikel powder saling bertabrakan. Selama proses berlangsung, terbentuk neck, grain boundaries dan setiap celah antar partikel mjd pores. Pores mjd kecil & berbtk bola

Tape Castingtape is formed by pouring the slip onto a flat surface (of stainless steel, glass, a polymeric film, or paper)De-airing in a vacuum may also be necessary to remove any entrapped air or solvent vapor bubbles, which may act as crack-initiation sites in the finished piecedoctor blade spreads the slip into a thin tape of uniform thicknessTape thicknesses normally range between 0.1 and 2 mm (0.004 to 0.08 in.

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