화학공학소재연구정보센터
Journal of Materials Science, Vol.29, No.19, 5165-5176, 1994
Microsphere-Filled Lightweight Calcium-Phosphate Cements
The incorporation of inorganic and organic microsphere fillers into calcium phosphate cement (CPC) to produce lightweight cementitious materials that could be used under hydrothermal conditions at high temperatures between 200 and 1000 degrees C was investigated. An aluminosilicate based hollow microsphere, with a density of 0.67 g cm(-3) and a particle size of 75-200 mu m, was the most suitable having a low slurry density of approximate to 1.3 g cm(-3), and a compressive strength greater than 6.89 MPa. This microsphere-filled lightweight CPC exhibited the following characteristics : 1, after autoclaving at 200 degrees C, amorphous ammonium calcium orthophosphate (AmCOP) salt and Al2O3.xH(2)O gel phases, formed by the reaction between calcium aluminate cement and an NH4H2PO4 based fertilizer, were primarily responsible for the development of strength; 2. at a hydrothermal temperature of 300 degrees C, the microsphere shell moderately reacted with the CPC to form an intermediate reaction product, epistilbite (EP), while crystalline hydroxyapatite (HOAp) and boehmite (BO) were yielded by the phase transformations of AmCOP and Al2O3.xH(2)O, respectively; 3, at an annealing temperature of 600 degrees C, the HOAp phase remained in the cement body, even though an EP -->anorthite (AN) phase transition occurred; 4, at 1000 degrees C, the phase conversion of HOAp into whitlockite was completed, while the AN phase was eliminated; and 5. the microsphere demonstrated excellent thermal stability up to temperatures of 1000 degrees C.