Fixed abrasive method

Method (9) is a fixed abrasive method. Slurry is not used. Instead, abrasive is coated on the pad. This method is used in some cases. However, as this method causes many scratches on wafers and thus requires scratch-preventing measures, it has not become the mainstream. 

Knoop developed an accepted method of measuring abrasive hardness using a diamond indenter of pyramidal shape and forcing it into the material to be evaluated with a fixed, often 100-g, load. The depth of penetration is then determined from the length and width of the indentation produced. Unlike WoodeU s method, Knoop values are static and primarily measure resistance to plastic flow and surface deformation. Variables such as load, temperature, and environment, which affect determination of hardness by the Knoop procedure, have been examined in detail (9). 

A definite shortcoming of Scott s method is that it fails to fix an exact quantitative relation between abrasiveness and hardness. Consequently, it can only be used for comparison, giving the strength of a material under operating conditions. 

Attrition accomplishes rock reduction by abrasion or by rubbing the rock between two surfaces, one of which may be fixed and the other moving, or both of which may be moving in the same direction but at a different rate of speed, or in different directions. Attrition is one of the most expensive and inconvenient methods of rock reduction, since it reduces the grinding medium to an excessive extent. Attrition is admissible where the rock may be made to grind upon itself, but in practice this has been accomplished only in an extremely limited way. 

The size and the shape of reforming catalysts depends on the form of operation of the reforming unit. For a moving bed, it is necessary to use beads, typically 1-2 mm in diameter, in order to facilitate circulation and to decrease mechanical abrasion of the catalyst. For fixed bed, catalysts are commonly 1/16-, 1/8-, or i- inch diameter and are shaped as spheres or cylindrical extrudates. In some cases the extrudates are the shape of a three- or four lobe cloverleaf The catalyst support is shaped by three methods granulation, drop coagulation, and... 

The damage or change in the finish coat and the transfer of color to the rubbing element are assessed after fixed mbbing intervals. This method provides data on the sensitivity of the finished leather surface to mbbing through, abrasion or transfer of color from the pigment coat under both dry and moist conditions. 

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