Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering Summary of Material Science Chapter 1: Science of Materials Chapter 2: Properties of Materials Chapter 3: Material Testing Chapter 4: Alloys of Materials Chapter 5: Plain Carbon Steels Chapter 6: Heat Treatment Chapter 7: Cast Iron Chapter 8: Plastics/Polymers Chapter 9: Composite Materials Chapter 10: Ceramics Chapter 11: Semiconductors & Diodes Chapter 12: Biomaterials Chapter 13: Electrochemistry

Ceramics are non-metallic inorganic compounds formed from metallic (Al, Mg, Na, Ti, W) or semi-metallic (Si, B) and non-metallic (O, N, C) elements. Inorganic materials processed and used at high temperatures. Internal structure and bonding accounts for their unique properties. Contain mixed ionic and covalent bonding Cutting tool tips, abrasives, piezo-electric transducers, insulators and magnets, refractories (resistant to treatment or heat) and fibres for reinforcement and optical transmission. CERAMICS

Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering CERAMICS

3 Classifications Crystalline Ceramics. These are used for cutting tools and abrasives. They are single phase materials such as aluminium oxide, or mixtures of such compounds. Carbides and nitrides (some) also belong to this group. Amorphous Ceramics. Group of ceramics are not crystalline and the molecules are not arranged in a regular geometric structure. This group of ceramic materials includes the "glasses" as used for such applications as glazing, mirrors, optical lenses, reinforcement fibres for GRP products and optical fibres for data transmission. Bonded Ceramics. This group includes the "clay" products. These complex materials containing both crystalline and amorphous constituents in which individual crystals are bonded to a glassy matrix after "firing". These ceramics are used as electric insulators & refractories for furnace linings. Ceramic insulators are suitable for use out-doors as their hard glaze renders them weather resistant (electricity grid systems). They can also be used at high temperatures (spark plugs).

Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering CERAMICS OXIDES e.g. alumina, beryllia, magnesia, thoria and zirconia. Good Hardness, lower melting temperature BORIDES e.g. chromium, molybdenum, titanium, tungsten and zirconium. Very high hardness coupled with good resistance to chemical attack and melting points ranging from C but do start to oxidise at about C. NITRIDES -high melting points, they have low resistance to oxidation and chemical attack generally. However "Borazon“ = synthetic boron nitride produced under high temperatures and pressures, has a hardness approaching that of diamond

Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering CERAMICS CARBIDES -high melting points, they lack resistance to oxidation at high temperatures. The more important refractory materials are carbides of boron, silicon, titanium, tungsten and zirconium. WC Cerium, molybdenum, niobium, tantalum, tungsten and zirconium carbides can be used at temperature above C in neutral or reducing atmospheres, whilst niobium, titanium and vanadium carbides can be used above C in an atmosphere of nitrogen. Hafnium carbide has the highest melting point of any know substance at C.

Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering CERAMICS PROPERTIES Refractoriness-The refractoriness of the various groups of ceramics is greater than most metals. The melting point of some ranges to C. Strength Ceramic materials have high compressive strengths compared with their tensile strengths and the ability to retain its strengths at high temperatures is one of its most important properties. The lack of tensile strength in ceramic materials is due to the presence of micro-cracks.

Dr. Owen Clarkin School of Mechanical & Manufacturing Engineering CERAMICS PROPERTIES Hardness - Ceramics are harder than any pure or alloyed metallic material even after heat treatment. This hardness makes ceramics useful as abrasives and as cutting tool tips. Vickers or Knoop hardness must be used. Electrical Properties -Ceramic materials have been used for insulation purposes for a long time. Glazed porcelain insulators are used for such purposes as supporting high and medium voltage overhead electric cables and also telephone and telegraph cables. Ceramic materials are also used for low loss, high frequency insulators, ferro-magnets and semi-conductor devices.