Fine ceramics defined in JIS (Japanese Industrial Standard) as "Nonmetal and inorganic material with new functions and properties, produced under precise control such as chemical composition, crystal structure, micro structure/grain boundary, shape and manufacturing process."
Traditional ceramics including refractories are mainly produced using natural raw material. On the contrary, fine ceramics is produced using pure refined artificial raw material under precisely controlled process.
In general, fine ceramics has the properties of hard and high strength, but it is rather brittle compared with metal or refractories.
Fine ceramics is produced through the method of mixing & grinding selected raw material and sintering with high temperature. In each process, various technology and technics & improvements are necessary to produce stable homogeneous products.
As we have accumulated production technology over the years as ceramics material manufacturer, our products are manufactured by ourselves systematically through all process from raw material treatment, molding, sintering and finishing.
Introducing of some part of the essential points for producing homogeneous and excellent products.
1）Homogeneous raw material mixing
Raw materials with sub-micron sizes are used in fine ceramics production. These fine particles have a tendency to condense due to intermolecular forces and electrostatic force. If heterogeneous condensed raw material is formed and sintered, crack will occur in final product because of heterogeneous density and distortion. Therefore, homogeneous distribution of raw material is essential to realize aimed functions. As such, most suitable grinding and mixing technology is required.
2）Selecting suitable method for forming
According to the composition of raw material, final shape and total production quantity, most suitable forming method is selected. In addition to these factors, we select forming method considering finishing way and required preciseness of sizes. Then, we design the mold.
Main forming method is shown below table.
|Kind of forming method
||Details of forming method
||Press method by one rig machine after casting powder of raw material
||Simple shape of flat and cylindrical shape
||Pre-heated raw material (added thermoplastic resin) is charged into metal mold to form
||Small complex shape
||Pre-heated row material (added thermoplastic resin) is extruded through metal mold to form
||Long stick type
|Cold hydrostatic press
||Isostatic press method using metal mold or rubber mold
||Pipe, plate, block,
||Firstly, cast the well-dispersed slurry raw material into gypsum mold. Then, gypsum mold absorbs moisture of slurry.
||Flat and cylindrical shape
3）To sinter the formed body (intermediate-product) with most suitable process depending on each product
When the formed body is burnt, adjacent particles of raw material gradually bind together at lower temperature than melting point (temperature) the body is burnt adjacent, space between particles became narrower and simultaneously shrinkage happen at entire area. This phenomena is called 「sintering」. Because properties of porosity and electrical conductivity are determined during burning process, many years of accumulated burning technology such as burning temperature, burning period, atmosphere control and piling method are important.
Examples of Defective Products
In brittle material like fine ceramics, if there is fine crack which humankind cannot recognize by visual observation, stress concentrates on a defective fine crack and finally leads to destruction. Therefore, the appearance inspection using fluorescence flaw detective liquid and a black light is carried out not to overlook even slight defect or crack.