title: Possibilities for strengthening hydroxyapatite ceramics.
abstract: Some physics during heating and sintering of powder pressings of hydroxyapatite (HA) under conventional (usual) conditions have been studied. It is revealed that heating and firing of the pressings of a middle-dispersity powder are accompanied by release of gases. The gas release hinders and can stop the shrinkage (sintering). The microhardness is low and has a complicated distribution on the surface and in the volume of ceramics. A slight degassing (drying) of the pressing before sintering heightens the density and improves the microhardness characteristics of the ceramics. The shrinkage stop effect is eliminated in pressings of a fine powder. On the basis of the results, a technique and some methods for quality improvement of ceramics were proposed and approbated. They consisted of the manufacture of samples of a mixture of two powders with different dispersity, use of a press technique with two male dies, thermal treatment of pressing before sintering, and the choice of moderate sintering conditions. The resulting ceramics had a density close to the theoretical, almost homogeneous microhardness distribution in the sample and much higher values of microhardness and compressive strength.
authors.affiliation: Physics of Solids Department, Physics Faculty, Kharkov State University, Ukraine.
authors.forename: Z Z
authors.initials: ZZ
authors.lastname: Zyman
authors.forename: I G
authors.initials: IG
authors.lastname: Ivanov
authors.forename: V I
authors.initials: VI
authors.lastname: Glushko
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry / Q000302:isolation & purification; D002516:Ceramics / Q000737:chemistry / Q000302:isolation & purification; D017886:Durapatite / Q000737:chemistry / Q000302:isolation & purification; D006244:Hardness; D010316:Particle Size; D011208:Powders; D013055:Spectrophotometry, Infrared
chemical_list: D001672:Biocompatible Materials; D011208:Powders; D017886:Durapatite