Sintering of different hydroxyapatite powders and low-melting sodium borosilicate glass
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THEORY AND TECHNOLOGY OF SINTERING, THERMAL AND CHEMICOTHERMAL TREATMENT SINTERING OF DIFFERENT HYDROXYAPATITE POWDERS AND LOW-MELTING SODIUM BOROSILICATE GLASS L. A. Ivanchenko1 UDC 546.41.185335.338611.711.5.086-0.539 The paper analyzes the sintering of three types of calcium phosphate powders and S–B–Na glass powder under the same conditions. It is concluded that a liquid phase, represented by the glass melt, shows up when the glass is sintered with biogenic or synthetic hydroxyapatite or a mixture of synthetic phosphates. The substantial pore formation in the sintering process is mainly due to the removal of carbon oxides and water vapors resulting from glass charge decomposition and glass boiling. Parameters of grain and porous microstructures of the ceramics are shown before and after the primary and secondary sintering. The mechanical strength and biosolubility of the ceramic samples are reported as well. Keywords: calcium phosphates, grain and pore microstructure, biosolubility.
INTRODUCTION Scientific literature on the development of new biomaterials for surgical repair of damaged bones in patients with musculoskeletal disorders for the last 10–15 years testifies that medical materials science has become highly relevant. The recent developments largely focus on the improvement of technologies and the creation of fundamentally new methods of producing ceramic composites or metal coatings based on hydroxyapatite (HAP). There is also interest in ceramics based on tricalcium phosphate Ca3(PO4)2, its solid solutions with HAP, and glassstrengthened calcium phosphates [1–4]. Ceramics made of synthetic HAP (SHAP) are peculiar in that their dense samples show high mechanical strength but weak bioresorption while porous, weakly sintered samples, especially those containing tricalcium phosphate, exhibit good resorption but quite low strength. For this reason, it was decided that calcium phosphate ceramics would be strengthened with phosphate or silicon glass [2, 4]. The main distinction of the composites based on biogenic HAP (BHAP) developed at the Frantsevich Institute for Problems of Materials Science is that the weight ratio of their crystalline and glass phases corresponds to the phase diagram of bioactive phosphate glass, referred to as Hench bioglass. Such a diagram is shown in [5]. It was previously shown that biomaterials with parameters optimal for use in bone surgery could be produced if
1Frantsevich
Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kiev, Ukraine; e-mail: [email protected]. Translated from Poroshkovaya Metallurgiya, Vol. 51, No. 3–4 (484), pp. 50–58, 2012. Original article submitted February 24, 2011. 1068-1302/12/0304-0165 2012 Springer Science+Business Media, Inc.
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BHAP or SHAP was sintered with a Si–B–Na glass charge in two stages: at T1 900C and T2 800C [6–8]. The properties of biomaterials can be modified by varying the HAP–glass weight ratio and primary sintering temperature T1 [6, 8–10]. Our goal is to summarize information on t
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