02760nas a2200205   4500008004100000022001400041245009500055210006900150260010600219300001400325490000700339520194900346653002602295653002202321653002202343653002202365100002002387700001802407856012902425       2006                        eng d  a0025-540800aNegative thermal expansion in silicalite-1 and zirconium silicalite-1 having MFI structure0 aNegative thermal expansion in silicalite1 and zirconium silicali  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJUL  a1392-14020 v413 a<p>In situ high temperature X-ray diffraction (HTXRD) studies on monoclinic silicalite-1 (S-1, silica polymorph of ZSM-5) and an orthorhombic metallosilicate molecular sieve, zirconium silicalite-1 (ZrS-1) with MFI structure (Si/Zr = 50) have been carried out using a laboratory X-ray diffractometer with an Anton Parr HTK 1600 attachment. While the structure of the S-I collapsed at 1123 K forming alpha-cristobalite. S-1 and ZrS-1 showed a complex thermal expansion behavior in the temperature range 298-1023 K, ZrS-1 was stable. Powder X-ray diffraction (PXRD) data taken in this region have shown strong negative lattice thermal expansion coefficient, alpha(v) = -6.75 x 10(-6) and - 17.92 x 10(-6) K-1 in the temperature range 298-1023 K-1 for S-1 and ZrS-1 samples, respectively. The thermal expansion behavior of S-1 and ZrS-1 is anisotropic, with the relative strength of contraction along a axis is more than that along b and c axes. Three different thermal expansion regions could be identified in the overall temperature range (298-1023 K) studied, corroborating with the three steps of weight loss in the TG curve of ZrS-1 sample. While the region between 298 and 423 K, displays positive thermal expansion coefficient with alpha(v) = 2.647 x 10(-6) and 4.24 x 10(-6) K-1, the second region between 423 and 873 K shows strong negative thermal expansion (NTE) coefficient alpha(v) = -7.602 x 10(-6) and - 15.04 x 10(-6) K-1, respectively, for S-1 and ZrS-1 samples. The region between 873 and 1023 K, shows a very strong NTE coefficient with alpha(v) = - 12.08 x 10(-6) and -45.622 x 10(-6) K-1 for S-1 and ZrS-1, respectively, which is the highest in the whole temperature range studied. NTE seen over a temperature range 298-1023 K could be associated with transverse vibrations of bridging oxygen atoms in the structure which results in an apparent shortening of the Si-O distances. (C) 2006 Elsevier Ltd. All rights reserved.</p>10amicroporous materials10aphase transitions10aThermal expansion10aX-ray diffraction1 aBhange, Deu, S.1 aRamaswamy, V.  uhttps://library.ncl.res.in/content/negative-thermal-expansion-silicalite-1-and-zirconium-silicalite-1-having-mfi-structure-001985nas a2200277   4500008004100000022001400041245011000055210006900165260007400234300001200308490000800320520103100328653001601359653001101375653001301386653002401399653001401423653001701437100002701454700002401481700002001505700002501525700002001550700001701570856012001587       2007                        eng d  a1520-610600aNCL-7, a novel all silica analog of polymorph B rich member of BEA family: synthesis and characterization0 aNCL7 a novel all silica analog of polymorph B rich member of BEA  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbJapan Assoc ZeolitescAPR  a108-1140 v1013 a<p>{Polymorph B-rich BEA type structure, NCL-7, was synthesized using hydrothermal method in fluoride medium using perchloric acid as promoter. The samples were characterized using XRD, low temperature N-2-adsorption and Si-29 MASNMR. As the structure of beta is highly disordered Rietveld refinement of powder XRD patterns is precluded. Phase composition is derived using the simulated patterns for the random intergrowths of polymorph A and B by DIFFaX. The stacking direction c' is perpendicular to the a'b' plane of the layer. The composition of polymorph B is found to be ca. 60-65%. Two other structures namely NCL-5 and NCL-6 with varying degree of polymorph B enrichment were also synthesized. Synthesis parameters such as effect of H2O/SiO2, TEAOH/SiO2, HClO4/SiO2 and crystallization temperature were studied thoroughly. The present article explains for the first time the synthesis and characterization of NCL-7, an analog of BEA type family with enrichment of polymorph B and its comparison with normal beta (*</p>10aB-polymorph10aDIFFaX10aPromoter10aReitveld refinement10asynthesis10azeolite beta1 aKadgaonkar, Mahesh, D.1 aKasture, Mahesh, W.1 aBhange, Deu, S.1 aJoshi, Praphulla, N.1 aRamaswamy, Veda1 aKumar, Rajiv  uhttps://library.ncl.res.in/content/ncl-7-novel-all-silica-analog-polymorph-b-rich-member-bea-family-synthesis-and-002275nas a2200217   4500008004100000022001400041245015900055210006900214260007300283300001000356490000800366520142200374653001001796653002801806653001701834100002001851700001901871700002401890700002001914856012301934       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<p>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.</p>10aHTXRD10anon-isothermal kinetics10aSilicalite-11 aBhange, Deu, S.1 aPandya, N., A.1 aJha, Ratnesh, Kumar1 aRamaswamy, Veda  uhttps://library.ncl.res.in/content/non-isothermal-kinetic-studies-template-decomposition-silicalite-1-framework-high-0