Production schemes for quasi-isostatic compaction of ceramic objects

Abstract

A classification method is provided for quasi-isostatic compaction of powder material objects. Schemes are considered for the action of compaction pressure on pressed material in relation to an assortment of pressed objects.The method of quasi-isostatic compaction is a fundamentally new version of isostatic compaction, combining successfully the advantages of the radial hydrostatic and static compaction methods, providing volumetric compression of pressed material. The method was developed for the first time in the Soviet Union, and there were no overseas analogs. The technology, developed for a broad range of objects, was introduced into 14 enterprises of the country. The method of volumetric (quasi-isostatic) compaction is the most economic and advanced procedure of all currently known isostatic and static compaction methods. Objects prepared by this method have high physicomechanical and electrical properties. The density of objects of aluminum oxide material is 94 -95% of theoretical, and with hydrostatic compaction of the same object this property does not exceed 85%. With static compaction the density of any objects of the same aluminum oxide material is 76 -82%.The compaction process is accomplished without using expensive isostats in dies, similar in construction to normal static compaction metal dies, using the equipment employed for static compaction. The sequence of production operations for quasi-isostatic compaction is similar to that for static compaction. The principle of quasi-isostatic compaction includes the fact that the medium transmitting a uniform pressure is an elastic material, i.e. synthetic rubber, that is similar to a quasiliquid, and transmits the applied pressure throughout the whole volume of a compacted object. Compared with hydrostatic compaction technology, the quasi-isostatic compaction method makes it possible to simplify considerably the technology and production equipment, to reduce capital expenditure and the production space, and to reduce production personnel. Compared with the static method, with quasi-isostatic (triaxial) compaction there is a considerable reduction in the metal content of the die and a reduction by several factors in the wear of metal surfaces. Industrial use of the quasi-isostatic compaction method creates a considerable saving in the national economy [1 -3].The quasi-isostatic compaction method has been used by us in order to prepare objects of a broad range: saggers (round, rectilinear, square), shells made of chamotte and alundum mixes, smooth rings with a diameter of 180, 190, 250, 370 mm and a height up to 250 mm, rings of ribbed configuration with a diameter of 156 mm made of aluminum oxide material, mixer balls with a diameter of 20, 30, 40, 50, 60 mm, powder condensers with a height of 170 and 120 mm, pipes of several standard sizes with a length of 65 and 160 mm (including with a wall thickness up to 1,5 mm), plates of several standard sizes (including with a size of 370´370´65 mm), crucibles, briquettes of cylindrical and rectangular shape, ro...

Methods Used for the Compaction and Molding of Ceramic Matrix Composites Reinforced with Carbon Nanotubes

“…The quasi-isostatic pressing makes it possible to realize the isostatic pressing mode using a standard uniaxial press without resorting to liquid, as in the case of CIP [47,[51][52][53][54][55][56][57][58][59][60][61][62][63]. The isotropic pressure transfer is achieved due to a deformation of an elastomeric mold (made of rubber or polyurethane) upon uniaxial compression.…”

Physical bases of quasi-isostatic compaction of powder materials

“…Due to a marked reduction in energy expenditure for friction of powder particles over the die wall, the pressed billet prepared by this method has high density and uniformity compared with a compact manufactured at the same pressure in normal metal dies [4,5]. In compacting powder materials the overall pressure P, applied to an object, is built up from three components [6]:…”