The present study illustrates the processing parameter associated with the preparation of natural resourced ultrafine hydroxyapatite powders in a cost effective way through thermal decomposition of chemically treated fish scale. The optimisation of processing calcification temperature of HAp powder was identified through thermal gravimetric analysis and corresponding X-ray diffraction studies. The optimised calcined hydroxyapatite powder derived from fish scale was wet ball milled for several hours and compacted into different shapes at lower pressure (850 kg cm 22 ). The green compacts were sintered at different temperature for 1 h in dry air atmosphere. The average grain sizes of sintered samples remain mostly in the submicrometre range and y91% of theoretical density was achieved even at lower compacting pressure.

In the present paper, synthesis of hydroxyapatite (HAp) powder from eggshell waste is produced through wet precipitation process at 50-55uC. The thoroughly washed and dried eggshell powder is treated with dilute nitric acid followed by diammonium hydrogen phosphate under controlled reaction conditions such as pH, temperature, stirring time, etc. to obtain white HAp precipitate. The formation of the HAp phase and its thermal stability were identified through thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy and X-ray diffraction studies at different calcined temperatures. The dried powder at 90-100uC was wet ball milled for several hours and compacted to cylindrical shapes at a lower pressure of 850 kg cm 22 . The green compacts were sintered at different temperatures for 2 h in dry atmosphere. Average grain sizes of sintered samples are mostly in submicrometre range. The morphologies of the green as well as sintered compacts were observed by field emission scanning electron microscopy.

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A stable, Ag55 cluster protected with 4-(tert-butyl)benzyl mercaptan (BBSH) was synthesized which exhibits two prominent absorption bands with maxima at 2.25 and 2.81 eV. A molecular ion peak at m/z 11 500 ± 20 in matrix assisted laser desorption ionization mass spectrum (MALDI MS), assigned to Ag55(BBS)31 was observed. Electrospray ionization (ESI MS) shows a prominent trication along with higher charged species. An analogous Ag55(PET)31 (PET = 2-phenylethanethiol, in the thiolate form) was also synthesized under optimized conditions which proves the amenability of this cluster and the synthetic methodology to other ligands.