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Decomposition Mechanism (decomposition + mechanism)
Selected AbstractsInvestigation of the Decomposition Mechanism and Thermal Stability of Nitrocellulose/Nitroglycerine Based Propellants by Electron Spin ResonancePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2007Anton Chin Abstract Nitrocellulose based (NC) and nitroglycerin based (NG) propellants often have a fixed acid and water content during the manufacturing time. After manufacture, the quantity and ratio of acid/water will continue to vary depending upon the conditions of storage and operation. The level of variation depends on many factors such as loading density, temperature, volume of ullage and sealing condition of the containing cartridge, just to name a few. As described in this paper and other literature, the degradation mechanisms and aging processes of NC/NG based propellants are extremely complicated. This paper describes the details of the application of Electron Spin Resonance (ESR) to study if the free-radical mechanism is involved in the decomposition of nitrocellulose and nitroglycerin. Due to the high free-radical intensity possessed by the propellant composition, we believe that a , complex intermediate may be formed between DPA and NG and/or NC. The formation of a , complex intermediate is not preferred because it may enhance the rate of decomposition of nitrate esters. [source] Validation of a thermal decomposition mechanism of formaldehyde by detection of CH2O and HCO behind shock wavesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2004Gernot Friedrichs The thermal decomposition of formaldehyde was investigated behind shock waves at temperatures between 1675 and 2080 K. Quantitative concentration time profiles of formaldehyde and formyl radicals were measured by means of sensitive 174 nm VUV absorption (CH2O) and 614 nm FM spectroscopy (HCO), respectively. The rate constant of the radical forming channel (1a), CH2O + M , HCO + H + M, of the unimolecular decomposition of formaldehyde in argon was measured at temperatures from 1675 to 2080 K at an average total pressure of 1.2 bar, k1a = 5.0 × 1015 exp(-308 kJ mol,1/RT) cm3 mol,1 s,1. The pressure dependence, the rate of the competing molecular channel (1b), CH2O + M , H2 + CO + M, and the branching fraction , = k1a/(kA1a + k1b) was characterized by a two-channel RRKM/master equation analysis. With channel (1b) being the main channel at low pressures, the branching fraction was found to switch from channel (1b) to channel (1a) at moderate pressures of 1,50 bar. Taking advantage of the results of two preceding publications, a decomposition mechanism with six reactions is recommended, which was validated by measured formyl radical profiles and numerous literature experimental observations. The mechanism is capable of a reliable prediction of almost all formaldehyde pyrolysis literature data, including CH2O, CO, and H atom measurements at temperatures of 1200,3200 K, with mixtures of 7 ppm to 5% formaldehyde, and pressures up to 15 bar. Some evidence was found for a self-reaction of two CH2O molecules. At high initial CH2O mole fractions the reverse of reaction (6), CH2OH + HCO , CH2O + CH2O becomes noticeable. The rate of the forward reaction was roughly measured to be k6 = 1.5 × 1013 cm3 mol,1 s,1. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 157,169 2004 [source] In situ thermo-TOF-SIMS study of thermal decomposition of zinc acetate dihydrateJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004Anil Vithal Ghule Abstract Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for an in situ thermal decomposition study of Zn(CH3COO)2·2H2O forming ZnO nanoparticles. TOF-SIMS spectra were recorded at regular temperature intervals of 25 °C in positive and negative detection modes in a dynamic thermal process. Controlled heating (5 °C min,1) of Zn(CH3COO)2·2H2O was also carried out using thermogravimetric analysis (TGA) in an oxygen atmosphere (20 ml min,1). Nearly spherical ZnO nanoparticles with no agglomeration and a narrow size distribution (diameter ,50 nm) were observed, which were characterized using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In situ thermo-TOF-SIMS was used to monitor the 64Zn+ and 66Zn+ ion abundances as a function of temperature, which showed a similar profile to that observed for weight loss in TGA during decomposition. Based on the experimental results, a possible decomposition mechanism for the formation of ZnO is proposed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mullite Decomposition Kinetics and Melt Stabilization in the Temperature Range 1900,2000°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Zhijun Xiao An investigation of the mullite decomposition mechanism and kinetics in the temperature range 1900,2000°C was conducted. SEM-EDS and XRD analysis showed that the decomposition of mullite in this temperature range was primarily caused by the presence of carbon from furnace components. A reaction mechanism, in which gas-phase SiO2 reacts with carbon to form SiO and CO, is proposed; both IR analysis and kinetic studies support the proposed mechanism. The decomposition was completely suppressed by the introduction of a modified crucible assembly and the addition of excess SiO2 to the reaction system. A mullite melt of stable composition was thus obtained, setting the groundwork for inviscid melt spinning mullite fiber making process development. [source] Synthesis of phase-pure SnS particles employing dithiocarbamate organotin(IV) complexes as single source precursors in thermal decomposition experimentsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2010D. C. Menezes Abstract Preparation of tin(II) sulfide, semiconductor material, has been accomplished by thermal decomposition of easily prepared organotin dithiocarbamate complexes: [Sn{S2CNEt2}2Ph2] (1), [Sn{S2CNEt2}Ph3] (2), [Sn{S2CNEt2}3Ph] (3) and [Sn{S2CN(C4H8)}2Bu2] (4). Phase-pure tin(II) sulfide has been obtained by pyrolysis of these precursors at 350 °C in N2. Thermogravimetric analysis, X-ray powder diffraction, scanning electron microscopy, X-ray electron probe microanalysis and 119Sn Mössbauer spectroscopy revealed that the complexes decompose in a single and sharp step (1 and 2), or in pseudo-single stage (3 and 4), to produce SnS. We have also measured the bandgap energies of the residues using electronic spectroscopy in the solid state and the result relates well to that in the literature for SnS, 1.3 eV. A decomposition mechanism was also proposed for each complex based on electrospray ionization tandem mass spectrometric results. The synthetic method used in this work might be useful for the preparation of pure SnS on a large scale. Copyright © 2010 John Wiley & Sons, Ltd. [source] Composite Platinum/Silicon Dioxide Films Deposited using CVDCHEMICAL VAPOR DEPOSITION, Issue 3 2005P. Martin Abstract We report the low temperature deposition of platinum/silicon dioxide composite films from tetraethylorthosilicate (TEOS) and platinum acetylacetonate (Pt(acac)2). The simultaneous CVD of TEOS and Pt(acac)2, in the presence of oxygen, has been shown to reduce the decomposition temperature of TEOS to as low as 320,°C (from 600,°C without Pt(acac)2). Composite films were grown at temperatures ranging from 300,°C to 440,°C, using an estimated 5:1 flow rate of TEOS to Pt(acac)2 and in 0,70% oxygen atmosphere. The overall growth rate was maximized at 400,°C and the overall activation energy of the thin film formation was ,80 kJ mol,1. The SiO2 phase was amorphous and the platinum phase crystalline with an average grain size of 9 nm as determined by X-ray diffraction (XRD). An in-situ Fourier-transform infrared (FTIR) spectroscopy study of the gas phase was undertaken to provide confirmation of the low temperature decomposition of TEOS promoted by Pt(acac)2. Despite the high Si/Pt ratio in the feed, the maximum observed Si/Pt ratio in the film was 1:1, suggesting a cooperative TEOS-Pt(acac)2 decomposition mechanism. [source] Powder second harmonic generation measurement and thermal decomposition mechanisms of a new organometallic compound [(18C6)Li][Cd(SCN)3]CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2009J. J. Zhang Abstract Single crystals of a novel nonlinear optical organometallic compound CLTC, ([(18C6)Li][Cd(SCN)3]), were grown from aqueous solutions via evaporation technique and characterized by IR spectroscopy, thermal gravimetric analysis and X-ray single-crystal diffraction. By X-ray single-crystal structural analysis it is revealed that the compound crystallized in a noncentrosymmetric space group Cmc21 of orthorhombic system with cell parameter a = 14.767(3) Å, b = 15.454(3) Å, c = 10.644(2) Å, V = 2429.0(8) Å3 and Z = 4. The thermal stability and thermal decomposition of CLTC crystal were investigated by means of thermogravimetry and differential thermal analysis. The second harmonic generation (SHG) efficiency was measured using the Kurtz and Perry powder technique. It was shown that the value of the SHG efficiency of CLCT powder was about 2 times higher than that of potassium dihydrogen phosphate (KDP). (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multiperiod design and planning of multiproduct batch plants with mixed-product campaignsAICHE JOURNAL, Issue 9 2009Gabriela Corsano Abstract This work presents a multiperiod optimization model for multiproduct batch plants operating during several time periods with different characteristics because of seasonal and market fluctuations. This model simultaneously considers decisions about the design, operation, scheduling, and planning of the plant and the corresponding trade-offs among them. Thus, decomposition mechanisms, which have been frequently used in previous approaches, are avoided through a formulation that takes into account the main elements of these problems. Besides, decisions are affected by different context conditions arisen by the multiperiod effect. Through a mixed integer nonlinear program, different alternatives of mixed production campaign are considered, handled by means of a novel set of scheduling constraints. This approach is posed for a fermentors network with high detail level in the description of the unit operations in a plant that produces yeast and ethanol. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] MOCVD of YF3 and Y1,xErxF3 Thin Films from Precursors Synthesized In Situ,CHEMICAL VAPOR DEPOSITION, Issue 6-7 2005G. Condorelli Abstract RE(hfac)3 precursors (RE = Y, Er and Hhfac=1,1,1,5,5,5-hexafluoroacetylacetonate) have been obtained in-situ in a metal-organic (MO) CVD reactor by vapor-solid reaction between Hhfac and powders of suitable mixtures of RE2O3 oxides. YF3 and Y1,xErxF3 (x , 0.2) ultra-thin films have been deposited over glass substrates under Ar/O2 environments. Fourier-transform infrared (FTIR) in-situ measurements have been used to identify the nature of the precursor species in the gas phase, as well as to investigate decomposition mechanisms which accompany the film growth. Deposition involves the breakdown of the metal,ligand bond, thus leading to free Hhfac ligands and fluorinated ketones. Films have been characterized by energy dispersive X-ray (EDX) microanalysis, grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). [source] | |||||||||||||