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:explode: CERAMIC TECHNOLOGY :fire:, Powder Injection Molding, Powder…
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Powder Injection Molding
mixed with thermoplastic polymer then heated and injected into mold cavity where upon cooling, hardens and form green body once the polymer binder is removed
Powder Pressing
uniaxial compression is where the die cavity is filled with powder and then pressure applied to top of die and then bottom part pushed compact piece away
Isostatic compression is when hydrostatic pressure is used to compact the ceramic powders from all direction which forms uniform density
hot pressing is when heat is added to the compression which makes green body more dense and finer grain size but die life decreases.
Slip Casting
prep of powder ceramic material and liquid into a slip. pour the slip into the porous mould of plaster where water can be absorber b the mould and solid is form. excess slip is then poured out via drain casting. the material in the mold is allowed to dry to provide proper strength for handling
Tape Casting
Thin sheets of green ceramic are casted as a flexible tape and these sheets are casted from liquid slip (ceramic +organic solvent)
during firing, the particle shrinks and porosity decreases and this imprve mechanical integrity
three stages : forms neck, neck thickens, grain boundary develop
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disperse ceramic particles in solvents to form stabilize slurry sedimentation. usage of polar head and nonpolar tail to reduce surface tension. can be both ionic and nonionic
solubility depends on chain side group, adsorb
on particle surface by van der Waal's force and can be used as bidner
material that helps to improve the strength of the as-formed product to provide strength for handling green strength is densified by firing
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plastic
higher wc (15-25%).
hand modeling, jiggering and plastic pressing occurs and extrusion
slip casting
grid particle to desire size and mixed with other components to for a suspension which has up to 40% water and then generally poured into porous plaster so that the mold can absorb the water.
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- mix of clay and lime bearing - calcinate to 1400 C and grind to fine powder - primary composition are tricalcium silicate and dicalcium silicate
- Produces a paste which hardens - hardening occurs due to hydration - forming 2CaO.SiO2.XH2O
Preparation of material via crushing/grinding or chemical treating to separate phases to achieve purity
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after forming green ceramic body, it has to go through sintering or firing process to reduce surface energy (both clay and non-clay composition)
the function is to bond individual grains, increase density, and reduce porosity
finishing is required to improve dimensional accuracy, improve surface and make minor changes in geometry
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they can be hard.brittle, chemically inert, impermeable, insulation, and transparent
main component is silica and it has high purity, good transparency, high softening point, chemically durable, low coefficient of thermal expansion, and expensive to produce
used in laboratory glasses, lenses, telescope mirrors, optical fibres
most common glass made of silica, sodium oxide and calcium oxide which has low softening point, high thermal coefficient and low chemical resistance
uses in window panes, light bubs, bottles and glass container
boron oxide added into soda lime glass which makes it low thermal expansion, high softening point, resistant to thermal shock and chemical attack.
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laboratory glass, cookware and glass container.
made by adding lead oxide and potassium oxide which has relatively soft surface with high refractive index, high density and attractive glittery appearance
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inorganic non-metallic sold compound which are hard strong, brittle, chemically inert, high melting point, heat and electrical insulators, opaque and porous
ceramic are used in construction, decorative, electrical insulator, medical field and advance composites
ceramic material produced by conversion of glass into polycrystalline structure through heat treatment
grain size of 01-1micron, fine crystal structure which makes the glass stronger than typical glass (up to 98% crystalinity)
- the glass is heated and shaped. Then, it is cooled down and reheated again to form a dense network of crystal nuclei and thanks to nucleation agents as titanium oxide, the crystallinity is increased
- high sealing properties, high mechanical strength, low thermal expansion, high thermal shock, good dielectric value, good biological properties, low prosoty
- construction, consumer. electronic components, medical field, and engineering components
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CVD is where the vapor of reactant chemically reacts at the surface of substrate to form high purity, high performance film.
- first reactant are transport by forced convection to the deposition region. reactant got diffused from main gas stream to boundary layer of wafer.
- adsorption of reactants on surface of wafer. Chemical decomposition, surface migration to attachment sites and other surface reactions occurs here.
- Desorption of by-products from the surface. the by-product is then transported by diffusion of boundary later back to the main gas stream.
- transport of byproduct by forced convection away from deposition region
- the process of CVD includes flow rate of the reactant gases, the nature and flow rate of any carrier gasses, the pressure in reaction vessel and the temp.
- substrate heating is needed for this endothermic reaction which has high yeild
CVD is very slow, very thin film, not suitable for mixture of material and got material limitation
high range of material, high purity, high densty
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reaction between molten metal and a gas. Oxidation of molten metal by a gas has been developed for porous dense production.
the filler and metal alloy are heated to the growth temperature where the oxidation process occurs from metal surface and into preform
DMO process is when the molten metal meets the preform where reaction of a molten metal with an oxidizing gas. the preform of dispersed phase is placed on the surface of parent molten metal in an atmosphere of oxygen
two condition is needed for this case and that is to have dispersed phase wetter by the formed oxide ceramic and the dispersed phase to not oxidize in an atmosphere of oxygen.
liquid metal oxidizes when it is in contact with oxygen forming thin layer of ceramic. The capillary effect forces the melt to penetrate through the porous ceramic layer.
the temp has to be in the range of 900 - 1500 C where the alloy contains a few percent of Mg and IVA element group. the oxide coating contains small pores which molten metal is drawn up to the top surface of the film, thereby continuing oxidation process.
as long as the molten and the oxidizing gas are available to sustain the process and the temperature is maintained, the reaction product continues to grow until the desired thickness. the two phase are oxidant product and unreacted product
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Fabrication route where a porous ceramic preform becomes dense ceramic covalent ceramic by reacting with fluid. Commonly, the process is accompanied by little or no shrinkage.
Reaction between a solid and liquid where a mixture of SiC particles, carbon and polymeric binder is formed into green body by pressing, extrusion or injection molding. then binder is the burned off by pyrolysis which the preform is infiltrated with liquid Si. then the SiC is formed via infiltration and reaction processes
Silicon powder is consolidated by pressing method and then green body is preheated in argon for 1200C where then machined to proper dimension and finally component heated in N2 at up to 1400 C. this nitridation process helps the formation silicon nitride
Reaction bonded aluminium oxide is where both gas-solid and gas liquid reaction take place. The process utilizes oxidation of powder Al. During heat treatment in an oxidizing atmosphere, the Al oxidizes to nano sized which undergoes phase transformation.
solution of metal compounds/ suspension in liquid is converted into a highly viscous mass. usage of metal alkoxides, a derivative an alcohol. Water is added either in the pure state/ dilute alcohol. Hydrolysis and condensation reaction occurs in stiring temp and suitable concentration of reactants and pH of the solution.
solution hydrolysis to sol then gelation to particulate gel then dried to dried gel and fired to dense product
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solution hydrolysis and condensation to solution of polymers and then gelation to polymeric gel and dried to dried gel and fired to dense product
high purity, good chemical homogeneity, fine porosity, lower densification temp
starting materials fairly expensive, difficulties of conventional drying which causes warping,shrinkage and cracking
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preceramic polymer is used as precursors and this process route has been applied to the production of nonoxide ceramic fibers in particular fibers of to silicon based ceramics
condensation reaction between Na and dimethyldicholorsilane in xylene to produce poly dimethylsilane and then dissolves in organic solvent and pyrolysis to SiC
reaction to produce SiN is when a preceramic polymer which is prepared by the ammonolysis of methylchlorosilanes is followed by the polymerization of silazane product and the pyrolysis to form SiN.
easy to process, relatively low temp, toxic component degrade at high temp, reduction in water volume due to high operating temp.
High operational and investment costs, air purification is needed to treat the gas from pyrolysis and produce ashes of high heavy metal content
this method involves melting a batch of raw materials followed by shape forming and this method is limited to fabrication of glass
i) a lower temp hold to induce nucleation of crystals. ii) one or higher temp to promote crystal growth on glass
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widely used for polycrystalline ceramics which involves consolidation of fine particles(form porous shaped powder) and firing to produce a dense product
densification and coarsening occur here to achieve high densification while reducing the driving force for densification
domination of densifying diffusion processes will favor the production of a dense body and when coarsening processes dominate high porous body
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low cost, safe, can use in most cases, can be recycled and filtration however cannot be applied at certain temps and takes time to dry.
achieve high solid loading, fast drying, high boiling temp but can be toxic, dangerous and expensive.
plasticity, flocculation, thickening, liquid retention
small liquid molecules added in by little to plastics or ceramic to reduce van der Waals forces to soften the polymer binder and increase its flexibility
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usually the powders are mixed with water temporarily to bind the particles together and after shaping the will sintered to remove any water
the raw material usually are reduce to powder from many method and this is then added all kind of additives to form proper composition
most traditional ceramics , water plays the main role therefore once drying, will leave lot of interparticle space
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this is the heat treatment process that sinters the ceramic material and it is performed in a furnace called a klin and this is where ceramic grains form bond and densification occur while porosity reduces
surface coating mather improve the color, waterproof, increase wear resistance
piece is fired before glazing, then glaze is applied and the fired again to harden glaze
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