Ceramics Mixture of metallic and non-metallic elements (clay products). Traditional: whiteware, tiles, brick, sewer pipe, pottery, and abrasive wheels. Industrial (fine ceramics): turbine, automotive, aerospace components, heat exchangers, semiconductors, seals, cutting tools.

Ceramic Applications Electronic insulators Engine components Machining tools Porcelain Bioceramics for prosthetics

Structure of Ceramics The structure of ceramic crystals is among the most complex of all materials. Contain various elements. Covalent bonding (electron sharing), stronger than metals. Hardness, thermal, and electrical resistance higher than metals. Finer the grain size, higher strength and toughness.

Ceramic Materials Clay (kaolin): silicate of aluminum. Flint: fine-grained silica. Feldspar: aluminum silicates, potassium, calcium/sodium.

General Properties of Ceramics Mechanical Properties Much stronger in compression vs. tension (one magnitude difference) Sensitive to cracks, impurities, porosity Lack toughness, ductility, are brittle and strong static fatigue failure (load over a period of time)- similar to stress-corrosion cracking. pre-stressing (compressing) increases resistance to breakdown from tensile stress.

General Properties of Ceramics Physical Properties low specific gravity/density. low thermal conductivity (porosity – air is poor conductor). low thermal expansion. resistance to wear. Alloying With metallic elements can cause ceramics to conduct

Types of Ceramics Oxide Ceramics Alumina Zirconia most widely used high temperature applications Electrical, thermal insulation, cutting tools Zirconia high toughness/strength resistance to thermal shock, wear, and corrosion. low thermal conductivity, friction coefficient. Engine components

Ceramic Knife (Zirconia) (global.kyocera.com)

Other Types of Ceramics Carbides tungsten, titanium, and silicon carbide. Silicon is an abrasive Grinding wheels, cutting tools Nitrides cubic boron nitride, titanium nitride, and silicon nitride. Grinding and cutting tools, turbine engines, bearings, sand-blast nozzles

Other Types of Ceramics (Cont.) Sialon silicon nitride and aluminum oxide, yttrium oxide, titanium carbide. Higher strength and thermal-shock resistance than silicon nitride Cutting tools Cermets ceramics bonded with metallic elements. cutting tools/high temperature applications.

Silica Polymorphic material (different crystal structures) Quartz Most glasses are 50% silica Silicates- reaction of silica and oxides of al, mg, fe, etc. (clay, asbestos, mica, and silicate glasses)

Glasses Amorphous solid (structure of a liquid) No specific freezing or melting point Cooled at a rate too high for crystals to form (supercooled). All glasses contain at least 50% silica.

Glass Applications Containers Windows Cookware Fiber Optics Monitors Lighting

Glass Properties Brittle, hard Resistant to chemicals and corrosion Low thermal conductivity and expansion. Dielectric properties. Reflection, refraction, absorption. Static Fatigue

Glass Ceramics High crystalline structure Stronger than glass Shaped first and heat treated devitrification or recrystallization of glass.

Graphite Crystalline form of carbon, having a layered structure. solid lubricant, low friction properties. brittle in nature. strength and stiffness increases with temperature.

Diamond Hardest substance known Synthetic (or industrial) lacks impurities which natural diamonds might have. electrical conductivity is 50 times higher than natural diamonds (heat sinks)

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