کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1475355 991117 2009 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Densification additives for hydroxyapatite ceramics
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد سرامیک و کامپوزیت
پیش نمایش صفحه اول مقاله
Densification additives for hydroxyapatite ceramics
چکیده انگلیسی

The present work is aimed at the elucidation of the role played by CaCl2 and NH4NO3 (the latter is a by-product of the solution synthesis of hydroxyapatite, hereinafter referred to as HAp) in the densification of nano-sized HAp powder in the course of the pressureless sintering. Nanocrystalline HAp powder was fabricated via the wet-precipitation technique by the dropwise addition of an (NH4)2HPO4 solution to a Ca(NO3)2 mother solution at a pre-adjusted pH at 60 °C. The pH of the aqueous mixture was maintained at a constant value (either 7 or 9) by the addition of an appropriate amount of NH4OH. The Ca/P ratio was set to 1.67, 1.61, and 1.48; 10 wt% of CaCl2 was added to dry HAp powder. NH4NO3 remaining in unwashed HAp powder can act as a fluxing agent that promotes partial melting at a relatively low temperature (150–250 °C) thus allowing the particles to rearrange into a denser packing. Several mechanisms of the CaCl2 action as a densification additive might be envisaged: (i) a decrease in the melting temperature; (ii) the surface wetting of grains; (iii) a change in the growth morphology owing to the high-temperature surfactant properties; (iv) a possible reaction with HAp on the surface of grains giving rise to the decomposition of HAp and yielding chlorapatite (ClAp), which can convert back to HAp over a wide temperature range and at any level of H2O.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of the European Ceramic Society - Volume 29, Issue 10, July 2009, Pages 1925–1932
نویسندگان
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