Showing papers on "Thermal decomposition published in 1994"
TL;DR: In this paper, the authors studied the thermal decomposition of Li-ion cells in inert gas and found that the nickel materials are least stable, the manganese compounds are most stable, and that the cobalt compounds show intermediate behaviour.
646 citations
TL;DR: In this article, a method for estimating critical temperatures (Tb) of thermal explosion for energetic materials is derived from Semenov's thermal explosion theory and the non-isothermal kinetic equation dα/dt = Af(α)e−E/RT using reasonable hypotheses.
293 citations
TL;DR: In this paper, the changes in chemical states and composition of the surface region of a Ag2CO3 powder at various stages during thermal decomposition have been examined using X-ray photoelectron spectroscopy (XPS...
Abstract: The changes in chemical states and composition of the surface region of a Ag2CO3 powder at various stages during thermal decomposition have been examined using X-ray photoelectron spectroscopy (XPS...
288 citations
177 citations
TL;DR: In this paper, it was shown that n-alkenes, hydrogen and a carbonaceous sedimentary rock containing moderately high concentrations of transition metals react under mild conditions (∼200 °C) to generate a light-hydrocarbon product indistinguishable from natural gas in both molecular and carbon isotope composition.
Abstract: THE idea that natural gas is formed by thermal decomposition of sedimentary organic matter1,2 enjoys almost universal acceptance3–6. But pyrolysis experiments on organic matter7–13 have failed to reproduce the composition of natural gas (typically 90% methane). It has recently been suggested14 that natural gas may instead be generated catalytically: transition metals are often found in carbonaceous sedimentary rocks, and might promote the reaction between hydrogen and n-alkenes (which are themselves formed during thermal decomposition of kerogen) to give light hydrocarbons and natural gas. We report here experimental results that support this hypothesis. In particular, we find that n-alkenes, hydrogen and a carbonaceous sedimentary rock containing moderately high concentrations of transition metals react under mild conditions (∼200 °C) to generate a light-hydrocarbon product indistinguishable from natural gas in both molecular and carbon isotope composition. Our results demonstrate that the reaction is indeed catalytic, and could alter the way in which we view the generation and distribution of oil and gas in the Earth.
163 citations
153 citations
TL;DR: In this paper, Raman scattering is used to study the thermal decomposition of photochemically produced polymeric C60 films and the rate for thermal dissociation of these bonds is found to follow an Arrhenius-type behaviour with an activation energy Ea=1.25 eV.
135 citations
TL;DR: In this paper, a pre-heat-treated HA powder was pre-treated at 1200 °C for 120 min (the XRD pattern showing no decomposition) and then mechanically mixed with titanium and titanium dioxide powders.
Abstract: Titanium (Ti) implants coated with hydroxyapatite (HA), combining the ability of HA to bond with natural bone and excellent mechanical properties of titanium, have been successfully used in clinics. To improve the crystallinity of the coatings, post-heattreatment was applied on the HA coating-titanium system. Several groups [1-4] have post-heat-treated plasma-sprayed and sputtered HA coatings, to increase their crystallinity and lower their solubility compared with the as-received coatings. Ducheyne et al. [5] employed a vacuum heat treatment on electrophoretically deposited HA coatings to investigate the induced changes on their structures. Besides the benefits produced by heat treatment, there also exist some negative side-effects. Ducheyne et al. [5] found that the heat treated layers contain distinctively different compositions from the as-received coatings. The present authors [3] also reported that the plasma-sprayed HA coatings began to decompose at 800 °C during vacuum heat treatment. It is well known that the HA structure is thermally stable up to 1250 °C in air [6] and to 1050 °C in vacuum [7]. So it is hypothesized that the destruction of HA structure in H A T i or HA-TiO: systems at lower temperatures than 1000°C is completely related to the titanium and its dioxide. In the present study, HA powder was pre-heat-treated at 1200 °C for 120 min (the XRD pattern showing no decomposition) and then mechanically mixed with titanium and titanium dioxide powders. The mixtures were pressed into circular plates and sintered for 30 rain in vacuum and for 60 min in air, separately, at different temperatures. The stability of the starting H A powder was also proved by heating it in vacuum (<1.333 x 10 -3 Pa) at 1000 °C for 30 min, showing the same reflection patterns as those of the standard HA structure. The XRD patterns were determined on a RIGAKU diffractometer (D/max-y A) with Cu-Ko~ radiation at 45-50 kV and 140160 mA. The XRD patterns in Fig. 1 exhibit phase compositions of the mixture of HA and titanium sintered at different temperatures in vacuum. The decomposition of HA induced by titanium begins at 800 °C with the appearance of traces of o: tricalcium phosphate (oL-TCP) and tetracalcium phosphate (TCPM). With the increase of temperature, this process becomes more extensive and no other phase is produced besides cr-TCP and TCPM. The results are identical with our previous reports [3] concerning the thermal
112 citations
TL;DR: In this article, a new, well-ordered, thermally robust ethylene glycol intercalate of kaolinite was formed by refluxing the dimethyl sulfoxide intercalates of Kao-DMSO with dry E.G., which is characterized by a dool of 9.4 A.
Abstract: A new, well-ordered, thermally robust ethylene glycol intercalate of kaolinite was formed by refluxing the dimethyl sulfoxide intercalate of kaolinite (Kao-DMSO) with dry ethylene glycol (EG). This new phase (Kao-EG 9.4 A) which is characterized by a dool of 9.4 A is distinct from a previously reported ethylene glycol intercalated phase of kaolinite (Kao-EG 10.8/k) which has a dool of 10.8 ,~. The char- acterization of these two phases was studied by XRD, NMR, FTIR, and TGA/DSC. It was found that the concentration of water in the ethylene glycol reaction media played a crucial role in governing which of the phases predominated. Water favored Kao-EG 10.8 A formation, while anhydrous conditions favored the formation of Kao-EG 9.4 A. It is hypothesized that Kao-EG 9.4 A is a grafted phase resulting from the product of the condensation reaction between an aluminol group on the interlamenar surface of kaolinite and the alcohol group of ethylene glycol. Ethylene glycol units would be attached to the inter- lamellar surface of kaolinite via A1-O-C bonds. The Kao-EG 9.4 A phase was found to be resistant to both thermal decomposition up to 330~ and also, once formed, in the absence of interlamellar water molecules, to decomposition by hydrolysis in refluxing water.
104 citations
TL;DR: In this paper, the kinetics and mechanism of the CIO + CIO reaction and the thermal decomposition of CIOOCI were studied using the flash photolysis/long path ultraviolet absorption technique.
Abstract: The kinetics and mechanism of the CIO + CIO reaction and the thermal decomposition of CIOOCI were studied using the flash photolysis/long path ultraviolet absorption technique. Pressure and temperature dependences were determined for the rate coefficients for the bimolecular and termolecular reaction channels, and for the thermal decompositon of CIOOCI.
100 citations
TL;DR: In this article, the authors studied the decomposition of NO and N2O by chars in a fixed bed reactor under steady state conditions, and the reactions were studied at temperatures from 673 to 1223 K and at partial NO and n2O pressures in the range of 0.19-1.92 mbar, respectively.
TL;DR: In this paper, the thermal decomposition of a number of nitramines was studied in dilute solution and in the melt, including acyclic and cyclic mononitramines.
Abstract: The thermal decomposition of a number of nitramines was studied in dilute solution and in the melt. The nitramines included acyclic mononitramines [dimethylnitramine (DMN), diethylnitramine (DEN), dipropylnitramine (DPN), and diisopropylnitramine (DIPN)], cyclic mononitramines [N-nitro-piperidine (NPIP) and N-nitropyrrolidine (NPyr)], cyclic dinitramines [N-dinitropiperazine (pDNP), 1,3-dinitro-1,3-diazacyclopentane (DNI), and 1,3-dinitro-1,3diazacyclohexane (mDNP)], and 1,3,5-trinitro-1,3,5-triazocyclohexane (RDX), octahydro-1,3,5,7tetranitro-1,3,5,7-tetrazocine(HMX), hexanitro-hexaazaisowurtzitane (HNIW), and 1,3,3trinitroazetidine (TNAZ). For the acyclic and cyclic monoand di-nitramines, the corresponding nitrosamines were the only or major condensed-phase product. Kinetics and activation parameters were determined for the thermolysis of dilute solutions (0.01 to 1.0 wt%) over range 200 to 300C. The thermolyses were found to be first-order with the rate constants unaffected by use of deuterated solvent. As the nitramines became more complex than dimethylnitramine (DMN), the rate of decomposition increased and the product distribution became more complex. As the length of the aliphatic chain increased (DMN < DEN < DPN), the rate of thermolysis increased, yet nitrosamine remained the only observed condensed-phase product. When a secondary carbon was attached to the N-nitramine (DIPN) rather than primary (DPN), the rate of decomposition increased and a new condensed-phase product was observed. Among the cyclic nitramines, the rate of decomposition increased as the number ofNNO2 groups increased (NPIP < pDNP; NPyr < DNI; mDMP < RDX). The position of the nitramine groups affected the decomposition; meta NNO2 groups (mDNP) decomposed faster than para (pDNP). Ring strain decreased stability: mDNP < DNI; HMX < RDX. In complex nitramines, the increase in decomposition rate, the appearance of new products, and the change in the relative importance of nitrosamine and of N2 and N2O is attributed to new decomposition routes available to them. However, since complex nitramines (e.g. RDX) maintain first-order kinetics and since most have activation energies in the range of 40 to 50 kcal/mol, it is believed that the triggering mechanism remains N-NO2 homolysis. Intramolecular hydrogen transfer is also considered an important mode of nitramine decomposition. Introduction Before attempting to understand the mechanisms operating in species containing multiple nitramine functionalities, we examined the simple nitramine, dimethylnitramine (DMN). To avoid complications resulting from multiphase decomposition and autocatalysis, we studied the thermolysis in dilute solution. Two different N-labeling studies were performed. In both, complete label scrambling was observed in the N2 and N2O gases and in the dimethylnitrosamine. Only partial scrambling of the N-label was observed in the reactant, DMN. Kinetic studies of
TL;DR: In this article, a study was performed to characterize the homogeneous precipitation of yttrium aluminum garnet (YAG) precursor particles by the thermal decomposition of urea in aqueous solutions.
Abstract: A study was performed to characterize the homogeneous precipitation of yttrium aluminum garnet (YAG) precursor particles by the thermal decomposition of urea in aqueous solutions. Cation concentrations were varied from 0·005 m to 0·30 m . Observation of powder morphology together with chemical analysis suggests a sequential precipitation process with aluminum ions forming a solid phase first. Fine-grained, reactive powders were obtained that crystallized to single-phase YAG upon heating to 850°C. The precipitate was a hydrated basic carbonate.
TL;DR: In this article, the authors evaluated the kinetics of thermal decarboxylation of aqueous solutions of acetic acid and sodium acetate at 335 and 355°C in contact with various surfaces as potential catalysts.
TL;DR: In this article, the properties of the oxides obtained by thermal decomposition of Ni/Al and Ni/Cr HT anionic clays at different temperatures were compared, and it was found that the hydrotalcite-type structure is necessary, but not sufficient, to obtain well dispersed and stable samples; also necessary is the presence of aluminum as the trivalent element.
Patent•
06 Jun 1994
TL;DR: An electrochemical cell incorporating cathode materials comprising at least one metal oxide, a first metal and a second metal or a mixture of a first and second metals or their metal oxides incorporated in the matrix of a host metal oxide is described in this paper.
Abstract: An electrochemical cell incorporating cathode materials comprising at least one metal oxide, a first metal and a second metal or a mixture of a first and a second metals or their metal oxides incorporated in the matrix of a host metal oxide is described. The cathode materials of this invention are constructed of the chemical addition, reaction, or otherwise intimate contact of various metal oxides and/or metal elements during thermal treatment in mixed states. The materials thereby produced contain metals and oxides of Group IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII, which include the noble metals and/or their metal oxide compounds. A preferred material comprises a composite metal oxide matrix formed as the thermal decomposition and reaction product of a matrix of vanadium oxide and at least two decomposable metals including copper and silver.
TL;DR: On thermal decomposition barium bis(citrato)oxotitanate (IV) citrate heptahydrate produces stoichiometric BaTiO3 fine powders at about 650°C as discussed by the authors.
TL;DR: In this article, selected triazole, tetrazole, triazine and tetrazine backbone compounds were shown by IR spectroscopy to convert to polymeric, melon-like, cyclic azine residues upon heating to T ≥ 500°C.
TL;DR: In this article, the authors examined the effect of tetralin addition on the deposit formation from a paraffinic jet fuel JP-8 which is rich in C[sub 9]-C[sub 16] long-chain alkanes, and an aromatic compound, n-butylbenzene.
Abstract: Hydrogen-transferring pyrolysis refers to the thermal decomposition of hydrocarbons in the presence of hydrogen donors. Relative to the pyrolysis of pure n-tetradecane (C[sub 14]H[sub 28]) at 450 C, adding 10 vol % of H-donor tetralin suppressed n-C[sub 14] conversion by 68 % after 12 min of residence time, by about 66% after 21 min, and by 37% after 30 min. The presence of tetralin not only inhibited the n-C[sub 14] decomposition, but also altered the product distribution. The decomposition and isomerization of primary radicals are strongly suppressed, leading to a much higher ratio of the 1-alkene to n-alkane with 12 carbon atoms and slightly higher alkene/alkane ratio for the other product groups. The overall reaction mechanism for the initial stage of hydrogen-transferring pyrolysis is characterized by a one-step [beta]-scission of secondary radical followed by H-abstraction of the resulting primary radical. Moreover, desirable effects of the H-donor are also observed even after 240 min at 450 C, especially for inhibiting solid deposition. The authors also examined the effect of tetralin addition on the deposit formation from a paraffinic jet fuel JP-8 which is rich in C[sub 9]-C[sub 16] long-chain alkanes, and an aromatic compound, n-butylbenzene. Adding 10 vol % tetralin tomore » a JP-8 jet fuel, n-C[sub 14], and n-butylbenzene reduced the formation of deposits by 90% (from 3.1 to 0.3 wt %), 77 % (from 3.0 to 0.7 wt %), and 54 % (from 5.6 to 2.6 wt %), respectively. These results suggest that, by taking advantage of H-transferring pyrolysis, hydrocarbon jet fuels may be used at high operating temperatures with little or no solid deposition.« less
TL;DR: In this article, a modification of the conventional gas condensation processing apparatus is described, in which the usual evaporative source is replaced by a chemical source, which combines rapid thermal decomposition and expansion of a precursor gas stream with rapid condensation of the product species on a cold substrate.
TL;DR: In this paper, the products from the thermal degradation of poly(ethylene glycol) (PEG) in a nitrogen atmosphere have been studied by GC/MS, and the results show that PEG degrades in nitrogen by a series of competitive intermolecular and intramolecular processes.
TL;DR: In this paper, the surface and catalytic properties of MgO were investigated at different process conditions, including reaction temperature, 700-800°C; CH 4 /O 2 ratio, 3.0-8.0; and gas hourly space velocity (GHSV), 25,500-102,000 cm 3 · g −1 · h −1 ).
TL;DR: In this article, an electrospray atomization of high-concentration (∼400 g/L) chemical precursor solutions was applied to the synthesis of yttria powders.
Abstract: Electrospray atomization of high-concentration (∼400 g/L) chemical precursor solutions was applied to the synthesis of yttria powders. Conditions were found which led to high-quality powders, composed of dense, spheroidal, submicrometer, and nanocrystalline oxide particles. The precursor solutions were hydrated yttrium nitrates dissolved in n-propyl alcohol at concentrations ranging from 44.1 to 455 g/L. Electrospray atomization produced submicrometer precursor droplets which were dispersed in air and carried through an electric furnace for thermal decomposition at 500°C for several seconds residence time. X-ray powder diffraction patterns indicated the expected cubic phase. Transmission electron micrographs showed that the particle structure varied with solution composition, ranging from hollow, inflated spheres for 6-hydrated nitrates to dense spheroids for 5-hydrated nitrates. The use of 6-hydrated nitrates in the solutions appeared to form particle surfaces which were impermeable to alcohol vapor evolved during thermal decomposition, leading to hollow, inflated spheres.
TL;DR: In this article, the point of zero charge (pzc) has been measured by potentiometric titration using KNO3 as a supporting electrolyte, regardless of the source, the same pzc at 8.1 ± 0.1.
TL;DR: In this paper, a magnesium-manganese hydroxycarbonate with the hydrotalcite structure was synthesized by coprecipitation from aqueous solutions of Mg2+ and Mn2+.
Abstract: A magnesium–manganese hydroxycarbonate with the hydrotalcite structure has been synthesized by coprecipitation from aqueous solutions of Mg2+ and Mn2+. According to temperature-programmed reduction data, 84% of the manganese is oxidized to Mn3+ during synthesis. Fourier-transform infrared spectroscopy, powder X-ray diffraction and transmission electron microscopy data support the hydrotalcite structure. Thermal decomposition in air at 390 °C leads to an amorphous material with a simultaneous increase of the specific surface area. Further calcination at higher temperatures (670 and 1000 °C) leads to crystallization of MgO and Mg2MnO4 spinel and to sintering. Reduction of the spinel takes place in two separate steps, probably through formation of intermediate Mn3O4 and finally MnO.
TL;DR: In this article, the structural decomposition of (NH4)3−xPMo12O40 heteropoly compounds was investigated at increasing temperatures to evaluate the thermal behavior, and was characterized by means of X-ray diffraction, FTIR spectroscopy, surface area measurements, ionic chromatography, EPR spectroscopic, and reactivity in the oxidative dehydrogenation of isobutyric acid to methacrylic acid.
TL;DR: In this paper, an equilibrium gas-phase calculation for the Si/C/Cl/H deposition system is performed over the range of conditions used to deposit silicon carbide (SiC) through the thermal decomposition of methyltrichlorosilane (MTS).
Abstract: Equilibrium gas-phase calculations for the Si/C/Cl/H deposition system are performed over the range of conditions used to deposit silicon carbide (SiC) through the thermal decomposition of methyltrichlorosilane (MTS). The compounds that exist in significant quantities in the gas phase, and thus may influence significantly the chemistry of the process, as well as the main deposition precursors are identified. The effect of temperature, pressure, and initial composition of the reacting mixture on the equilibrium composition of the gas phase is determined, and process conditions that may lead to stoichiometric silicon carbide films are suggested. Based on the results of the equilibrium calculations, a kinetic model for the homogeneous chemistry of the decomposition of MTS is proposed. Several reaction sequences leading to the generation of carbon and silicon deposition precursors are considered and their effects on the chemistry of the system are examined. Finally, the mechanism is incorporated into the reaction and transport model of a plug flow hot-wall reactor and the overall model is used to obtain the spatial variation of the composition of the gas phase under conditions typically encountered in chemical vapor deposition reactors.
TL;DR: In this paper, the kinetics and mechanism of the thermal decomposition of 3-nitro-1,2,4-triazole-5-one (NTO), a heterocyclic nitro triazole, have been studied, together with its morphology and evolved gaseous products, using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR), differential scanning calorimetry, X-ray diffractometry (XRD), and hot-stage microscopy.