Papers by Keyword: Thermal Decomposition

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Authors: Ian C. Madsen, Ian E. Grey, Stuart J. Mills
Abstract: A study of the thermal decomposition sequence of a sample of natural arsenian plumbojarosite has been undertaken using in situ X-ray diffraction. The sample was heated to 900°C using an Anton-Paar heating stage fitted to an INEL CPS120 diffractometer. The data were analysed using a whole-pattern, Rietveld based approach for the extraction of quantitative phase abundances. The instrument configuration used required the development and application of algorithms to correct for aberrations in the (i) peak intensities due to differing path lengths of incident and diffracted beams in the sample and (ii) peak positions due to sample displacement. Details of the structural models used were refined at selected steps in the pattern and then fixed for subsequent analysis. The data sequence consists of some 110 individual data sets which were analysed sequentially with the output of each run forming the input for analysis of the next data set. The results of the analysis show a complex breakdown and recrystallisation sequence including the formation of a major amount of amorphous material after initial breakdown of the plumbojarosite.
Authors: Zhi Bing Xu, Yi Wang
Abstract: ZnO nanoparticles have been fabricated with cation resins templates by thermal decomposition reaction. TEM and XRD showed the ZnO nanoparticles synthesized have an average diameter of 46.5 nm with sphere-shaped. One strong green-light emission peak at 530 nm was observed.
Authors: Hui Yan Zeng, Zi Ling Yan, Meng Ran Jiao, Dong Dong Xu, Jiu Xin Jiang
Abstract: An entirely novel preparation method of calcium carbonate (CaCO3) from calcium hydrogen carbonate (Ca (HCO3)2) solution was presented and named as thermal decomposition. The variation of the polymorphs and morphologies of CaCO3 particles with reaction temperature was investigated. XRD result indicates that high temperature favors the formation of calcite. Cubic or rhombohedra calcite crystals, lamellar and spherical vaterite crystals and rod– and needle–like aragonite crystals are found in powder synthesized at different temperatures. The reaction process was also discussed in the present work.
Authors: Wen Wen Qu, Wen Jin, Jing Yu Xu, Shu Yang, Jin Hui Peng
Abstract: Zinc acetate and Zn-oxo complex of Zn4O(CH3COO)6 containing in the spent catalyst of vinyl synthesis were investigated by means of the first principles of density functional (DFT) methods. The geometries, energies, charge populations and local electron density distributions of the two compounds and their formate analogues were analyzed. Based on the pyrolysis characteristics of the spent catalyst, the thermodynamic properties of ΔG, ΔH and ΔS for possible decomposition reactions of zinc acetate and Zn4O(CH3COO)6 were calculated as functions of temperature. The results provide a theoretical evidence that Zn4O(CH3COO)6 is more stable than zinc acetate due to the regular Zn4O and ZnO4 tetrahedral coordination between Zn atoms and two kinds of O atoms. The preparation of Zn4O(CH3COO)6 via the hydrolysis of zinc acetate is thermodynamically feasible. Zn4O(CH3COO)6 is further decomposed into ZnO via a decarboxylation reaction rather than a hydrolysis reaction.
Authors: Alfred A. Christy
Abstract: The adsorption and desorption of water molecules from α, β and γ-cyclodextrins were studied by gravimetric and thermogravimetric analysis. Cyclodextrins like all the other carbohydrates have tendency to adsorb water molecules. However, their cyclic nature tends to affect the adsorption patterns. The cyclic nature of the cyclodextrins facilitates the formation of hydrogen bondings between OH groups of the neighbouring glucose units. The C2(1)-OH forms hydrogen bonding with C3(2)-OH. The extent of the hydrogen bond formation and strength of the hydrogen bond affect the way the adsorption and dehydration of water molecules from cyclodextrins take place.
Authors: W. M. Abdel-Wareth, Xu Xu
Abstract: Effects of various grain sizes (10~390 µm) under heating rate of 40 °C/min on ammonium perchlorate (AP) decomposition characteristic parameters, the decomposition thermal behavior and kinetic parameters (activation energy and pre-exponential factor), were investigated by simultaneous DSC/TGA in a dynamic nitrogen atmosphere. In addition, the specific surface areas were measured by the BET-method. Moreover, the kinetic parameters were determined by a simplified approach based on the isoconversional method. The results showed that, the higher the AP particle size the lower the determined decomposition kinetic parameters. In addition, the results were in acceptable agreements with some important literatures. Moreover, it was highly recommended to apply the higher agreeable heating rates for AP samples to determine that parameters more accurately.
Authors: Chun Yang, Xiang Rong Liu, Li Na Wang, Wen Sheng Shen, Dao Wu Yang
Abstract: Thirteen novel complexeswere synthesized using this method, by employing the designed ligand o-carboxylbenzaldehyde-2-pyrroleformylhydrazone (H2L). Elemental analysis, molar conductivity,Fourier transform infrared (FTIR) spectracharacterizations show that the composition formula of the complexes is RE(HL)(H2L)•2H2O (where RE=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Y). The thermal decomposition of the thirteen complexes was studied by Subscript textTG-DTG analysis and their apparent activation energies (E) were calculated by Kissinger’s and Flynn-Wall-Ozawa’s methods.
Authors: Wei Qiang Pang, Hui Xiang Xu, Yang Li, Xiao Bing Shi
Abstract: The theoretical performances of NEPE (nitrate ester plasticized polyether) propellant with and without ADN were calculated with minimum free energy method. The burning characteristics and the thermal decomposition of propellants were determined by nickel chromium wire method and TG- DTG, respectively. The SEM of NEPE propellants and the mechanical sensitivity were also detected. The results show that the specific impulse and the adiabatic flame temperature are increase with an increase in the content of ADN oxidizer. The burning rate and pressure exponent of propellant with a change of pat content of ADN can be boosted higher than those of the AP formulations.
Authors: Yu Hong Feng, Jia Cheng Li, Qiang Lin, Xi Bin Wang, Zhou Xin Wu, Su Juan Pang, Zhong Liang Sun
Abstract: A series of dialdehyde cellulose samples with varied aldehyde content were prepared by oxidation of bacterial cellulose with sodium periodate. The X-ray diffractometry profile showed that the crystallinity degree of bacterial cellulose was 66%, but that of the dialdehyde cellulose (containing 12% aldehyde ) was 56%. Thermal decomposition of these dialdehyde cellulose samples and bacterial cellulose were studied by thermogravimetry. The decomposition of bacterial cellulose in nitrogen started at 230 and rapid weight loss occurred between 300-400. The introduction of dialdehyde group to bacterial cellulose resulted in significant shifts of decomposition to lower temperature range. The decomposition of dialdehyde cellulose (12% aldehyde ) started at 180 and rapid weight loss between 200-350. The temperature of rapidest weight loss shifted from 340 of bacterial cellulose to 290 of the dialdehyde cellulose(12% aldehyde).
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