The word ceramic comes from a Greek word meaning potter's clay.Originally, ceramics referred to objects made from potter's clay.Nowadays, ceramic technology has developed a range of materialsfar beyond the traditional concepts of the potter's art. These include:• glass products• abrasive and cutting tool materials• construction industry materials

Unit 1 Ceramics

CeramicsCrystalline

CeramicsAmorphous

CeramicsBonded

Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. More simply put, when using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentation using one of over 12 different test methods

The Knoop hardness test method, also referred to as a microhardness test method, is mostly used for small parts, thin sections, or case depth work.

http://www.hardnesstesters.com/Applications/Knoop-Testing.aspx

CeramicsCements

Ceramics can be:• electrical insulators• cements and plasters for investment moulding• refractory (heat resistant) linings for furnaces .• refractory coatings for metals.StrengthCeramics are reasonably strong in compression, but are weak in tension and shear. They maintain their compressive strength even ate very high temperatures.Like most very hard materials they are brittle and lack ductility.They also suffer from micro cracks which occur during the firing process. These can lead to weaknesses and fatigue failiure.

HardnessMost ceramics are harder than other engineering materials- you can see this from the table on slide 2. As a result they can be used for cutting tool tips and for abrasives…. Carbon Boron Nitride is a good example of this.

Refractoriness.This is the ability to withstand high heat conditions in normal service conditions..High Alumina brick and fireclays can tend to soften gradually. Refractories which have a high proportion of silica to alumina are ofetn used as furnace linings.Electrical properties.