02274nas a2200217 4500008004100000022001400041245015900055210006900214260007300283300001000356490000800366520142200374653001001796653002801806653001701834100002001851700001901871700002401890700002001914856012201934 2008 eng d a1387-181100aNon-isothermal kinetic studies of the template decomposition from silicalite-1 framework-high temperature X-ray diffraction and thermogravimetric analysis0 aNonisothermal kinetic studies of the template decomposition from aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a64-710 v1133 a

Non-isothermal decomposition of the tetrapropylammonium cations (TPA(+)) intercalated in silicalite-1 framework has been carried out using thermogravimetric (TG) analysis and high temperature powder X-ray diffraction (HTXRD) techniques. Conversion factor for template decomposition is calculated using two methods viz., % weight loss from the thermogravimetric analysis and changes in the intensities of the Bragg reflections 101/011 and 200/020 in the HTXRD patterns scanned at different temperatures (range 298823 K). The calculated apparent activation energy for template decomposition in air was 129 and 125 kJ mol(-1), respectively, for the two techniques TG and HTXRD, calculated using the Kissinger method. By Flynn-Wall-Ozawa approach of isoconversion, apparent activation energy for template decomposition in air was 123 and 124 U mol-1, respectively, for TG and HTXRD data. The reaction order was determined using the method of Kennedy and Clark and it is similar to 2 by both the techniques. The second order of template decomposition can be attributed to the fact that TPA+ is positioned in two different orientations inside the silicalite-1 framework. Template removal occurs with a contraction in unit cell dimensions. There is a decrease in the lattice parameters of the as-synthesized silicalite-1 sample after removal of template from the framework. (C) 2007 Elsevier Inc. All rights reserved.

10aHTXRD10anon-isothermal kinetics10aSilicalite-11 aBhange, Deu, S.1 aPandya, N., A.1 aJha, Ratnesh, Kumar1 aRamaswamy, Veda uhttp://library.ncl.res.in/content/non-isothermal-kinetic-studies-template-decomposition-silicalite-1-framework-high-002154nas a2200289 4500008004100000022001400041245008800055210006900143260010600212300001400318490000700332520116500339653001301504653002301517653002401540653001101564653002201575100001901597700001901616700001801635700002101653700002401674700001801698700001801716700001301734856011701747 2008 eng d a0025-540800aNovel hydroxide precursors for low temperature synthesis of selected ternary oxides0 aNovel hydroxide precursors for low temperature synthesis of sele aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJUL a1842-18490 v433 a

A novel method of using hydroxide precursors to reduce the synthesis temperature for few selected ternary oxides has been presented here. This technique is very useful and advantageous when the ternary oxides contain an alkaline earth element. The selected compositions for this method are BaCeO3 (BC), BaBiO3 (BB), La0.7Sr0.3CoO3 (LSCO) and BaBi2Nb2O9 (BBN). Commercially purchased strontium (or barium) hydroxide and freshly prepared lanthanum, cobalt, bismuth and niobium hydroxides were mixed thoroughly in stoichiometric ratio and heated at different temperatures ranging from 100 to 700 degrees C for 10 h for corresponding compositions. The sequence of the reaction and evolution of the product phase were studied by the X-ray diffraction (XRD) studies. The phase purity and lattice parameters were also determined by XRD investigations. All the product phases in each case were formed at relatively low temperature than when they were prepared by co-precipitation or solid state method. The morphology and average particle size of these powders were investigated by scanning electron microscopy (SEM). (C) 2007 Elsevier Ltd. All rights reserved.

10aCeramics10aChemical synthesis10aElectron microscopy10aOxides10aX-ray diffraction1 aMuthurajan, H.1 aRao, Koteswara1 aGupta, U., N.1 aPradhan, Sivaram1 aJha, Ratnesh, Kumar1 aKumar, H., H.1 aMirji, S., A.1 aRavi, V. uhttp://library.ncl.res.in/content/novel-hydroxide-precursors-low-temperature-synthesis-selected-ternary-oxides-001881nas a2200205 4500008004100000022001400041245006800055210006800123260008100191300001200272490000600284520115900290100002501449700001901474700002101493700002401514700002401538700001701562856009601579 2008 eng d a1546-542X00aNovel synthesis of SrBi2Nb2O9 powders from hydroxide precursors0 aNovel synthesis of SrBi2Nb2O9 powders from hydroxide precursors a9600 GARSINGTON RD, OXFORD OX4 2DQ, OXON, ENGLANDbBLACKWELL PUBLISHINGcJAN a101-1040 v53 a

Simple hydroxide precursors were used for the first time for the synthesis of a typical Aurivillius compound (SrBi2Nb2O9 (SBN)) at a low temperature. This method is very advantageous because it circumvents the use of SrCO3 in the case of conventional ceramics as well in the coprecipitation methods, thereby lowering the formation of the product phase. Commercially purchased strontium hydroxide is mixed thoroughly with freshly precipitated bismuth and niobium hydroxides in a stoichiometric ratio and heated at different temperatures ranging from 100 degrees C to 750 degrees C for 12 h. The sequence of the reaction and evolution of the product phase was monitored by X-ray diffraction (XRD) studies by recording the XRD for samples calcined at different temperatures. The incipient SBN phase begins to form at temperatures as low as 400 degrees C, and phase formation was complete only at 650 degrees C as revealed by the XRD observations. The differential thermal/thermogravimetric analyses) also corroborate this result. The morphology and average particle size of these powders were investigated by transmission electron microscopy studies.

1 aGupta, Upendra, Nath1 aRao, Koteswara1 aPradhan, Sivaram1 aJha, Ratnesh, Kumar1 aMuthurajan, Harries1 aRavi, Venkat uhttp://library.ncl.res.in/content/novel-synthesis-srbi2nb2o9-powders-hydroxide-precursors-0