Increased surface area during sintering of calcium phosphate glass and sodium chloride mixtures

Abstract

Glass scaffolds were obtained by the salt sintering method, using mixtures of calcium phosphate glass, 25.42%SiO2-10.89% P2O5-32.68%CaO-31%Mg0(mol%), and salt, NaCl, pressed and sintered bellow the salt melting point, followed by leaching of the salt in water. The sintering behaviour of glass/salt powder mixtures was followed by dilatometry, BET and SEM. It was found that the specific surface area (SSA) of supports sintered between 700-750 degrees C and leached, can be 15-50 times higher than that of the glass precursor powder, a very surprising behaviour because it presents the opposite tendency of a typical sintering process. Dilatometric curves showed an unusual expansion from similar to 450 degrees C until similar to 700 degrees C, followed by shrinkage at higher temperatures. This expansion accompanies the observed increase of SSA and the microstructures showed a clear effect of reaction between the glass and the salt with remarkable wrinkling of the glass particle surfaces. This phenomenon was further investigated by using DTA, XRD and FTIR. (C) 2014 Elsevier Ltd. All rights reserved.