Showing papers on "Thermal decomposition published in 1990"
185 citations
TL;DR: In this article, the dislocation pile-up avalanche model is used to explain the crystal size dependence for hot spot-controlled initiation of chemical decomposition in cyclotrimethylenetrinitramine crystals subjected to drop-weight impact testing.
Abstract: The dislocation pile‐up avalanche model is used to explain the crystal size dependence for hot spot‐controlled initiation of chemical decomposition in cyclotrimethylenetrinitramine crystals subjected to drop‐weight impact testing. Deformation‐induced temperature rises, hot spot sizes, and lifetimes are related to previously reported values for direct thermal decomposition. A reasonable chemical reaction yield is estimated from available kinetic data.
184 citations
TL;DR: In this article, six alternative decomposition modes of silanol are examined with ab initio electronic structure theory, and the MP2/6-31G(d,p) level of computation and single-point energies obtained with MP4/MC-311G (d, p) wave functions predict that the 1,1-and 1,2-eliminations of molecular hydrogen are both thermodynamically and kinetically competitive.
Abstract: Six alternative decomposition modes of silanol are examined with ab initio electronic structure theory. Geometries determined at the MP2/6-31G(d,p) level of computation and single-point energetics obtained with MP4/MC-311G(d,p) wave functions predict that the 1,1- and 1,2-eliminations of molecular hydrogen are both thermodynamically and kinetically competitive, with all other processes requiring at least 10 kcal/mol more energy to occur. At the highest level of theory, silanone is predicted to be 2.7 kcal/mol lower in energy than hydroxysilylene
178 citations
TL;DR: In this paper, the effect of N-substituents on the radical polymerization of poly(substituted maleimides) was investigated and the polymerization reactivities, i.e. yield and molecular weight of the polymers, were found to change depending on the structure of the n-substantituents.
Abstract: The effect ofN-substituents on the radical polymerization ofN-substituted maleimides (RMI) was investigated. The polymerization reactivities, i.e. yield and molecular weight of the polymers, were found to change depending on the structure of theN-substituents. The poly(RMI)s bearing a bulkyN-substituent were confirmed to be semiflexible poly(substituted methylene)s which were soluble in many organic solvents, but did not melt below their decomposition temperatures. From thermogravimetric analysis determined in a nitrogen stream, no weight-loss of poly(RMI) was observed at temperature below 300°C, and the maximum decomposition temperature was 400–440°C, except forN-tert-alkyl substituted derivatives which decomposed at 240–280°C via a two-step reaction.
124 citations
TL;DR: In this paper, a method for determining the real kinetics of solid-state reactions from analysis of the shape of controlled-rate thermal analysis curves is proposed, which provides an easy way for discriminating between Avrami-Erofeev and diffusion kinetic laws.
122 citations
TL;DR: In this article, the surface coverage of SiH3 species is varied, and the coverage-dependant kinetics of siH3 decomposition are examined using temperature programmed SSIMS.
Abstract: Silane adsorption at a surface temperature of 150 K and the surface decomposition of SiH3 and SiH2 have been investigated on the Si(100)‐(2×1) surface using static secondary ion mass spectrometry (SSIMS) and temperature programmed desorption (TPD). Silane dissociatively chemisorbs at 150 K to form SiH3 and H. At saturation, the combined coverage of these two is approximately 0.4 groups/1st layer Si atom (0.2 SiH4 adsorbed/1st layer Si atom). Using SiH4, the surface coverage of SiH3 species is varied, and the coverage‐dependant kinetics of SiH3 decomposition are examined using temperature programmed SSIMS. Changes in SiH4 exposure and source of SiH3 (di‐ vs monosilane) cause changes in surface SiH3 stability. The stability changes are interpreted as due to blocking of empty sites (dangling bonds, db) required for SiH3 decomposition to SiH2 and H. It is shown here that the decomposition temperature of SiH3 can vary from 200 to 600 K, depending on the dangling bond coverage (θdb). Subsequently, evidence for ...
121 citations
TL;DR: The thermal decomposition of dolomite, CaMg(CO 3 ) 2, has been studied by obtaining thermogravimetric and differential thermal analysis curves in various controlled atmospheres involving the use of N 2 )-CO 2 mixtures as mentioned in this paper.
120 citations
118 citations
TL;DR: A detailed chemical mechanism was developed in this paper to describe the reaction system of chlorobenzene pyrolysis in helium, which yields significantly less conversion but more C (solids) for similar residence times.
Abstract: Thermal reaction studies of dilute mixtures (0.37%) of chlorobenzene in hydrogen have been performed in tubular flow reactors at various surface to volume ratios and 1 atm total pressure. Residence times range from 0.02 to 2.5 s with temperatures between 1,050 and 1,275 K. HCl, benzene, and C (solids) are observed as the major products; minor products include methane, cyclopentadiene, toluene, naphthalene, and biphenyls. Chlorobenzene pyrolysis in helium yields significantly less conversion but more C (solids) for similar residence times. A detailed chemical mechanism is developed to describe this reaction system.
117 citations
TL;DR: In this paper, a kinetic analysis of the thermal decomposition of eucalyptus sawdust, cellulose, and cellulose kraft lignin was performed from temperature-programmed reaction experiments, using two different approaches.
103 citations
TL;DR: In this paper, the evolution of (Sr, Ti) resin intermediates from the solutions during the Pechini process, and their pyrolysis to SrTiO3 were investigated using differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques.
Abstract: The evolution of (Sr, Ti) resin intermediates from the solutions during the Pechini process, and their pyrolysis to SrTiO3 were investigated using differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques. In order to understand the Pechini process better, the organic solutions containing either only titanium ions or no metal ions were also prepared and thermally polymerized so that their decomposition processes could be examined in the same manner. In the case of the initial (Sr, Ti) organic solutions, all organic acid groups were bonded mainly either with ethylene glycol forming esters, or with Sr/Ti ions forming unidentate complexes. With heat treatment, the nature of the bonding between carboxylate groups and Sr/Ti ions changed: unidentate → bridging → ionic. Carbonate species were detected at 530 ° C using infrared spectra. Their concentration was reduced as SrTiO3 formed. On the basis of powder X-ray diffraction data, it is doubtful that SrC03 and TiO2 were formed as distinct intermediate phases. Possibly, a carboxylate complex (Sr2Ti2O5CO3) was formed prior to the formation of SrTiO3.
TL;DR: In this paper, the thermal decomposition of trimethylgallium (TMGa) has been studied in a variety of carrier gases, using a time-of-flight mass spectrometer to analyze the products and obtain kinetic information.
TL;DR: In this article, high-resolution electron energy loss spectroscopy was used to study methanol decomposition to adsorbed CO and hydrogen on Pt(111, where only 2% of a monolayer of CO was formed regardless of the initial coverage.
TL;DR: In this paper, mass spectrometric studies of the products of thermal decomposition of triethylgallium (TEGa), and trimethyl gallium (TMGa) adsorbed on Ga-stabilized GaAs(100) in ultrahigh vacuum were performed.
TL;DR: X-ray crystal structures reveal a mononuclear, square-planar geometry for 2, and a distorted, square pyramidal geometry for 3 as discussed by the authors, showing that the mixture of copper, CuO and Cu2O gives copper.
AT&T1
TL;DR: The mechanism and kinetics of the thermal decomposition of trimethylamine alane (TMAA) on aluminum and silicon single crystal surfaces in ultrahigh vacuum are reported in this paper.
TL;DR: In this article, the authors studied the kinetics of the reaction between trimethylgallium (TMGa) and AsH3 in a flow tube reactor with D2 as the carrier gas and using a time-of-flight mass spectrometer to analyze the products.
TL;DR: In this paper, the authors used thermal decomposition of thioacetamide in acidic zinc solutions to produce spherical, monodisperse particles with a specific type of particle size distribution.
Abstract: Colloidal sols of ZnS were prepared by thermal decomposition of thioacetamide in acidic zinc solutions. Precipitation was carried out in the presence of nitrate, acetate, chloride, and sulfate ions. Particle morphology was influenced by the chemical nature of the anions present in the solution as well as the rate of sulfide ion generation. Spherical, monodisperse particles having a specific type of particle size distribution, i.e., monosized, bimodal, or continuous distribution, with mean sizes in the range of 0.15 to 3 μm, were formed depending on the anion type and sulfide ion generation rate. Individual particles always consisted of clusters of sphalerite crystallites except when sulfide ions were generated at low rates and sulfate ions were present. In such cases a mixture of α- and β-ZnS was formed.
TL;DR: In this article, it is assumed that the oxycarbonate observed is formed from the methane deep oxidation on the catalyst surface, which appears to act as an intermediate in the production of CO2 and is thus important for the resulting selectivity.
Abstract: The oxidative coupling of methane (OCM) has been found to be structure sensitive on La2O3 catalysts exhibiting different crystallite morphologies. Thin plates obtained by thermal decomposition of lanthanum nitrate at 650 °C are more selective on OCM reaction performed at 750 °C than the particles obtained by decomposition of the nitrate at 800 °C. It is assumed that the oxycarbonate observed is formed from the methane deep oxidation on the catalyst surface. This compound appears to act as an intermediate in the production of CO2 and is thus important hi the resulting selectivity.
TL;DR: In this paper, the identity of the majority of the potassium titanates described in the literature were synthesized, and their Raman spectra recorded by x-ray diffraction was confirmed by XRD data.
Abstract: The majority of the potassium titanates described in the literature were synthesized, and their Raman spectra recorded. The identity of the compounds K2TiO3, K2Ti2O5, K2Ti4O9, K2Ti6O13, and K2Ti8O17 was confirmed by x-ray diffraction. Raman spectroscopy was then used to study the hydrolysis, under different conditions, of K2Ti2O5 and of K2Ti4O9. On drying of the hydrolysis products, the following species were found to from: K2(H2O)0.66Ti8O16(OH)2, K1.33(H2O)0.33Ti4O8.33(OH)0.67, and H2Ti8O17. On ignition at temperatures of 500-600°C these species converted, respectively, to K2Ti8O17, K2Ti6O13, and TiO2(B). Raman spectroscopy was used to establish that (1) K6Ti4O11 consists of a mixture of K2TiO3 and a new compound K4Ti3O8; (2) K2Ti3O7 consists of a mixture of K2Ti2O5 and K2Ti4O9, and (3) K2Ti5O11 consists of a mixture of K2Ti4O9 and K2Ti6O13. The temperature of decomposition and the identity of the products of the thermal decomposition of K2Ti8O17, K2Ti4O9, K2Ti2O5, and K4Ti3O8 were determined by Raman spectroscopy. The XRD data of the newly identified compounds are reported.
TL;DR: In this paper, the authors reported the preparation of fine-particle, large-surface-area ceria by the combustion process developed for preparation of $\alpha$-alumina, aluminates, chromites, and ferrites.
Abstract: Fine-particle ceria having narrow size distribution is of interest as polishing material for ophthalmological lenses, television tubes, plates and mirrors [1]. The preparation has been reported of such ceria by the hydrolysis of cerium isopropoxide [2] and cerium nitrate [3, 4] followed by thermal decomposition, as well as by the thermal decomposition of cerium oxalate hydrazinate [5] and cerium hydrazine carboxylate [6]. In this letter we report the preparation of fine-particle, large-surface-area ceria by the combustion process developed for the preparation of $\alpha$-alumina [7], aluminates [8], chromites [9] and ferrites [10]. The process involves rapid decomposition of a saturated aqueous solution containing ceric ammonium nitrate and urea $(CH_4N_20)$, carbohydrazide $(CH_6N_4O (CH))$, oxalyl dihydrazide $(C_2H_{16}N_4O_2 (ODH))$ or tetraformal trisazine $(C_4H_{16}N_6O_2 (TFTA))$ redox mixtures.
TL;DR: The surface chemistry induced by UV photons and low energy electrons of chlorobenzene (C6H5Cl) on Ag(111) has been studied in this article, where the adsorption is accompanied by a surface work function change (ΔΦ) of −0.65 eV at one monolayer and − 0.9eV at multilayer coverages.
Abstract: The surface chemistry, induced by UV photons and low energy electrons, of chlorobenzene (C6H5Cl) on Ag(111) has been studied. C6H5Cl adsorbs molecularly on Ag(111) at 100 K and desorbs molecularly at 170 K (physisorbed) and 230–240 K (chemisorbed) with no thermal decomposition. The adsorption is accompanied by a surface work function change (ΔΦ) of −0.65 eV at one monolayer and −0.9 eV at multilayer coverages. Both UV photons and low energy electrons induce the decomposition of adsorbed C6H5Cl. The energy threshold for the decomposition is 3.5–3.8 eV for photons and ∼5 eV for electrons. For photons and <12 eV electrons, the decomposition involves only C–Cl bond cleavage, producing surface phenyl groups and Cl atoms. Phenyl groups recombine and desorb as biphenyl at 390–400 K during post‐irradiation temperature programmed desorption (TPD). They do not dehydrogenate. However, for electron energies higher than ∼12 eV, the decomposition involves cleavage of C–H, C–Cl, and, probably, C–C bonds. In this case, p...
TL;DR: In this paper, the authors focused on the thermal decomposition of the material generated by ion exchange of decavanadate ions into the layers of a magnesium aluminum hydroxide hydrotalcite-like compound, over the temperature range from ambient to 650°C.
01 Nov 1990
TL;DR: In this paper, the thermal decomposition of benzyl radicals has been investigated behind reflected shock waves by monitoring the formation of hydrogen atoms by using a shock tube in conjunction with atomic resonance absorption spectrometry (ARAS).
Abstract: The thermal decomposition of benzyl radicals has been investigated behind reflected shock waves by monitoring the formation of hydrogen atoms. The results reported here have been obtained by using a shock tube in conjunction with atomic resonance absorption spectrometry (ARAS). The temperatures ranged between 1450 and 1700 K at total pressures around 2 bar. The test gas mixtures consisted of argon with relative concentrations of a few ppm benzyliodide, C7H7I. From the measurements of the temporal H-atom concentrations, in connection with thermochemical restraints, it was deduced that the benzyl decay is preceded by isomerization of benzyl. Due to the low initial concentration of the radical precursor, it was possible to evaluate a first order rate coefficient for the initiation reaction:
The heat of formation of the benzyl radical is discussed. A value of ΔH0f, 298 = 215.5 kJ mol−1 fits best to the experimental results.
TL;DR: In this paper, a detailed decomposition scheme of coprecipitates and individual components is proposed and discussed, and the values of the observed weight loss are in good agreement with those of the theoretical values.
Abstract: Thermal analysis was performed on coprecipitated materials and on individual components. The detailed decomposition schemes of coprecipitates and individual components are proposed and discussed. According to the proposed decomposition schemes, the values of the observed weight loss are in good agreement with those of the theoretical values of the coprecipitated materials and individual components. The results indicate that barium titanyl oxalate is an inserting compound, i.e., a structure of distorted barium hydrogen oxalate hydrate being inserted by Ti(OH)3+. The results also verify that copreciptation of barium and titanium ions in an oxalate aqueous solution at pH 7 is a mixture of BaC2O4· 0.5H2O and TiO(OH)2· 1.5H2O and coprecipitation of barium and titanium ions using the process of Yamamura et al. is a mixture of Ba(NO3)2 and Ti(OH)2C2O4.
TL;DR: In this article, thin films of calcia-stabilized zirconia were fabricated from Zr and Ca acetylacetonato complexes on a La 0.6 Sr 0.4 MnO 3 porous electrode substrate by spray pyrolysis method.
TL;DR: In this article, the preparation of ternary compound thin films, taking advantage of the formation of binuclear complexes with organotin oxides or copper(II) dithiocarbamate complexes, was investigated.
TL;DR: In this paper, a new thermal battery cathode material, synthetic pyrite, has been developed as an alternative to the naturally occurring Pyrite and the discharge behavior, thermal stability, and surface chemistry of the synthetic material were evaluated by single-cell studies, thermogravimetry (TG), and x-ray photoelectron spectroscopy (XPS).
Abstract: A new thermal battery cathode material, synthetic , has been developed as an alternative to the naturally occurring pyrite. The discharge behavior, thermal stability, and surface chemistry of the synthetic pyrite were evaluated by single‐cell studies, thermogravimetry (TG), and x‐ray photoelectron spectroscopy (XPS). Isothermal and nonisothermal TG methods were used to elucidate the kinetics of pyrite decomposition. The controlling mechanism of the decomposition process and the decomposition rate of at various temperatures were investigated. Synthetic pyrite undergoes thermal decomposition more slowly than natural pyrite of equivalent particle size. Synthetic of high purity and having uniform physical and chemical properties may provide a solution to the problems of nonavailability and variable quality of the presently used natural material.