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Showing papers on "Thermal decomposition published in 1986"


Journal ArticleDOI
TL;DR: In this article, the changes which take place during heat activation of hydrotalcite have been studied by 27Al nuclear magnetic resonance-magic angle spinning, Auger and XPS spectroscopy, transmission electron microscopy, and high resolution nitrogen desorption techniques.

506 citations


Journal ArticleDOI
01 Aug 1986-Nature
TL;DR: In this article, the preparation of small alloy particles by reduction of metal ions by KBH4 in aqueous solutions is described, which may have applications in ferrofluids, magnetic memory systems and catalysis.
Abstract: Amorphous alloys are normally prepared as thin ribbons or films by the liquid quench technique or by vapour deposition. Recently we have shown1 that ultra-fine amorphous Fe–C alloy particles can be prepared by thermal decomposition of Fe(CO)5 in an organic liquid; that is, by a chemical reaction. Here we report the preparation of small alloy particles by reduction of metal ions by KBH4 in aqueous solutions. Mossbauer and X-ray diffraction studies show that the particles are amorphous. The amorphous phase is formed because the chemical reaction takes place below the glass transition temperature and because boron atoms are present in the particles. The method may be used for the large-scale production of ultra-fine amorphous alloy particles, which may have applications in ferrofluids, magnetic memory systems and catalysis.

291 citations


Journal ArticleDOI
TL;DR: In this paper, high-concentration ultrafine particles having geometric mean diameters ranging between 0.01 and 0.06 µm and a geometric standard deviation of about 1.4 were obtained by varying the temperatures of the evaporator containing the liquid alkoxides and the reactor furnace, and the flow rate of carrier gas.
Abstract: Ultrafine spherical titanium, silicon, and aluminium oxide particles were prepared by the thermal decomposition of their alkoxide vapors, produced by evaporation and subsequent heating. High-concentration ultrafine particles having geometric mean diameters ranging between 0.01 and 0.06 µm and a geometric standard deviation of about 1.4 were obtained by varying the temperatures of the evaporator containing the liquid alkoxides and the reactor furnace, and the flow rate of carrier gas. For furnace temperatures lower than 400^oC for TiO, and 1000^oC for SiO_2 and Al_2O_3, the particles obtained were found to be amorphous. The observed changes in the particle size distributions due to changes in operating conditions were compared with those predicted theoretically by solving the discrete-continuous aerosol general dynamic equation accounting for coagulation and generation of monomer by thermal decomposition. The effect of monomer number concentration on the size distribution of generated particles was found to be qualitatively explained.

198 citations


Journal ArticleDOI
TL;DR: In this paper, the thermal decomposition of citric acid is studied by thermogravimetry (TG) and differential scanning calorimetry(DSC) techniques under various conditions.

176 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured the rate of decomposition of trimethylgallium (TMGa) and arsine by sampled gas infrared absorption spectroscopy, and the activation energy for decomposition in a quartz vessel is 34 kcal/mol.

162 citations



Journal ArticleDOI
TL;DR: In this article, the adsorption and thermal decomposition of ammonia at a Ni(110) surface was studied by means of thermal desorption (TD) and high resolution electron energy loss (HREEL) spectroscopy in the temperature range 110-500 K.

122 citations


Journal ArticleDOI
TL;DR: In this article, the thermal decomposition characteristics of rice husk have been investigated by dynamic thermoanalytical techniques: DTA, TG, DTG and isothermal heating.

104 citations


Journal ArticleDOI
TL;DR: It was found that the number and complexity of thermal reaction products increased with decreasing oxygen concentration, and with the exception of Freon 113, each component was less stable in the mixture as compared to pure compound data.
Abstract: In this report, the effect of oxygen concentration on the thermal stability of the components of a mixture of carbon tetrachloride, monochlorobenzene, 1,1,2-trichloro-,1,2,2-trifluoroethane (Freon 113 (Du Pont)), trichloroethylene, and toluene and the formation of thermal reaction products is examined. Thermal decomposition studies were conducted in atmospheres in which combustion oxygen was in excess, stoichiometric, and absent (pyrolysis). The components were also run individually in atmospheres with stoichiometric and excess oxygen. Results indicate that decreasing oxygen concentration increased the stability of the mixture components except Freon 113 and carbon tetrachloride. Furthermore, with the exception of Freon 113, each component was less stable in the mixture as compared to pure compound data. The stability of Freon 113 remained unchanged regardless of reaction atmosphere. It was found that the number and complexity of thermal reaction products increased with decreasing oxygen concentration. In all cases, products ranged from simple chlorinated aliphatics to complex polynuclear aromatics. 18 references, 7 figures, 2 tables.

96 citations



Journal ArticleDOI
TL;DR: In this paper, it was shown that benzene decomposition on the Rh(111) crystal surface begins at 400 K, forming a mixture of CH and C/sub 2/H species.
Abstract: Benzene decomposition on the Rh(111) crystal surface has been studied over the temperature range of 300-800 K by high-resolution electron energy loss spectroscopy (HREELS), temperature-programmed desorption (TPD), and low-energy electron diffraction (LEED). Our results show that benzene decomposition begins at 400 K, forming a mixture of CH and C/sub 2/H species. The relative amounts of these two species vary with temperature; at 470 K, the concentration ratio of CH to C/sub 2/H is 0.4. Above 500 K, these fragments dehydrogenate and condense to form C/sub n/H polymers. By 800 K, the adsorbed monolayer is completely dehydrogenated, forming a polymeric carbon monolayer with a vibrational spectrum similar to that of an ordered graphite monolayer. The authors propose that benzene decomposition on Rh(111) proceeds by decyclotrimerization to form three acetylenes which immediately decompose to CH and C/sub 2/H species.

Journal ArticleDOI
TL;DR: Magnesium aluminium oxide solid solutions were prepared by thermal decomposition of hydrotalcite-like compounds, [Mg1−xAlx,(OH)2]-CO3)x2·mH2O, at 500-700°C as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, the thermal decomposition of trimethylindium and phosphine was studied under flow conditions, and the activation energy in the homogeneous range was 69.2 kcal/mol.

Journal ArticleDOI
Ryohei Otsuka1
TL;DR: In this article, a direct formation theory for the formation of dolomite in CO 2 was proposed. But, it is not known whether or not the lower decomposition temperature depends on CO 2 pressure.

Journal ArticleDOI
TL;DR: In this article, the anneal behavior of silicon oxynitrides was studied using Fourier transform infrared absorption spectroscopy, nuclear reaction analysis, and electron spin resonance, and it is suggested that the coexistence of both Si-H and N-H bonds offers the possibility for cross linking and that consequently the decomposition temperature of both types of bonds is lowered.
Abstract: The anneal behavior of plasma‐enhanced chemical vapor deposited silicon oxynitride films has been studied using Fourier transform infrared absorption spectroscopy, nuclear reaction analysis, and electron‐spin resonance. The anneal temperature range was 500–1000 °C. It is observed that the oxynitrides which contain only N–H bonds are thermally stable in the temperature range under study. The layers which also contain Si–H bonds are considerably less thermally stable. Abundant hydrogen effusion from these layers is observed at temperatures as low as 600 °C, accompanied by cracking and shrinkage of the films. It is suggested that the coexistence of both Si–H and N–H bonds offers the possibility for cross linking and that consequently the decomposition temperature of both types of bonds is lowered. Evidence for the occurrence of cross linking is found in the infrared difference spectra. Consistently, the silicon unpaired electron density does not increase upon annealing. The Si–H and N–H bands effectively shift towards higher wave numbers upon annealing at higher temperatures. This is ascribed to the inhomogeneity in bond strength, which in turn is related to a variation in electronegativity of the surrounding groups.

Journal ArticleDOI
TL;DR: Mise en evidence de la formation d'alcanes a chaine droite de C 1 a C 14 and D'alcenes de C 2 a c 14 ; il se forme egalement de grandes quantites d' alcanes de C 18 a C 30 a chaines droites and reticulees.
Abstract: Mise en evidence de la formation d'alcanes a chaine droite de C 1 a C 14 et d'alcenes de C 2 a C 14 ; il se forme egalement de grandes quantites d'alcanes de C 18 a C 30 a chaines droites et reticulees. Mecanisme de formation de ces nouveaux produits

Journal ArticleDOI
TL;DR: In this paper, the IR spectra of the monomers and homopolymers of glycidyl azide (GAP), 3-azidomethyl-3-methyloxetane (AMMO), 3,3-bis(azidmethyl)oxetanes (BAMO), and 3-(2,3)-diazidopropoxymethyl)-3-moxy-mixture (DAPMMO) were assigned, and 10 scans s−1 were used to characterize the slow (5K min−1) and rapid

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the literature on the products of pyrolysis and combustion from polystyrenes and the toxicity of those products and concluded that polystyrene is among the least toxic materials used in buildings and residences.
Abstract: The current English literature through 1984 on the products of pyrolysis and combustion from polystyrenes and the toxicity of those products is reviewed. Among 57 compounds detected by chemical analyses of the thermal decomposition products produced under various atmospheric conditions (vacuum, inert and oxidative), the main volatile component is the styrene monomer, Evidence is provided that the mass fraction of styrene increases with furnace temperatures at least through 500°C. At 800°C and above, the concentration of styrene decreases. In oxidative atmospheres, carbon monoxide (CO), carbon dioxide (CO2) and oxidative hydrocarbons are formed. The concentrations of CO and CO2 are a function of temperature and combustion conditions, i.e. greater amounts are produced in the flaming than in the non-flaming mode. Eleven different test procedures were used to evaluate the toxicity of the pyrolysis and combustion atmospheres of polystyrenes. The more toxic environments produced under flaming conditions appear to be mainly attributed to CO and CO2 but rather to some other toxicant, probably the styrene monomer. When compared with other common materials used in buildings and residences, polystyrenes, in general, are among the least toxic.

Journal ArticleDOI
P. K. Gallagher1, M. E. Gross1
TL;DR: In this article, the nature, products, and enthalpy of the thermal decomposition of [Pd(CH3CO2)2]3 were determined in air, nitrogen and vacuum.
Abstract: The nature, products, and enthalpy of the thermal decomposition of [Pd(CH3CO2)2]3 were determined in air, nitrogen and vacuum. Thermogravimetry, differential thermal analysis, evolved gas analysis, differential scanning calorimetry, and infrared spectroscopy were used to characterize the process and products. In vacuum the trimer volatilizes completely below 200 °C. The IR spectrum of the gas phase species is reported. At atmospheric pressure the material decomposed to Pd between 200 and 300 °C depending upon the rate of heating. The apparent activation energy for this process is about 115 ± 5 kJ mol−1 and the enthalpy is 440 ± 20 kJ mol−1. In the presence of oxygen, however, oxidation of the ligands leads to an overall exothermic process. The resulting the Pd then slowly oxidizes to PdO2 up to the decomposition temperature of the oxide near 800 °C. There is the slight loss of a Pd containing species, presumably due to sublimation or gas entrainment, during the decomposition below 300 °C. The extent of this loss increases with increasing heating rate, approaching 10% of the total Pd at heating rates of 64 °C min−1.

Journal ArticleDOI
TL;DR: In this paper, an isothermal thermogravimetric analysis (TGA) study of the decomposition of RDX, HMX and the respective deuterated analogues, RDX-d/sub 6/ and HMX-D/sub 8/, has been carried out.
Abstract: An isothermal thermogravimetric analysis (TGA) study of the decomposition of RDX, HMX and the respective deuterated analogues, RDX-d/sub 6/ and HMX-d/sub 8/, has been carried out. In RDX, a kinetic isotope effect (KIE) (K/sub h//K/sub d/) of 1.5 was observed for the first time in the temperature range 199-216/sup 0/C. In the HMX decomposition, an isotope effect of approx.2.0 was consistently obtained in the temperature range 237-282/sup 0/C with no apparent temperature dependence. In both substances the KIE produced a small but definite decrease in shock sensitivity measured by the exploding metal foil method. These results indicate that the rate-determining steps in the processes of thermal decomposition and the chemical process of initiation are likely to be the same. Thus, the kinetic isotope effect served as a novel experimental probe to test the similarity, or otherwise, of the rate-limiting steps of the slow decomposition and the rapidly accelerating reactions of the initiation. Possible rate-limiting steps and reaction mechanisms are discussed.


Journal ArticleDOI
TL;DR: Transparent Sb-doped SnO2 films were prepared at 600°C on glass substrates by thermal decomposition of tin 2-ethylhexanoate and antimony tributoxide as mentioned in this paper.
Abstract: Transparent Sb-doped SnO2 films were prepared at 600° C on glass substrates by thermal decomposition of tin 2-ethylhexanoate and antimony tributoxide. The films 100 to 300 nm thick, which are composed of fine particles, were very smooth. The films showed no preferred orientation. The minimum resistivity (2.1×10−2Ω cm) was attained at a concentration of 8 at% Sb on the substrate precoated with SiO2. The transmission of these films was about 80% over a wavelength range from 0.4 to 2.0 μm.

Journal ArticleDOI
TL;DR: In this paper, a thermal gravimetric method was used to measure rates of decomposition of NAHCO3 particles, which produces a highly porous Na2Co3 that reacts with SO2 rapidly and completely at moderate temperatures.
Abstract: A thermal gravimetric method was used to measure rates of decomposition of NAHCO3 particles. Such decomposition produces a highly porous Na2Co3 that reacts with SO2 rapidly and completely at moderate temperatures. Hence, NaHCO3 decomposition provides a reactant with attractive features for SO2 removal. The rapid rate of decomposition combined with the high heat effect prevented determining intrinsic rates by constant temperature runs when the temperature level was above 400 K. However, rising-temperature runs, which allowed time for heat transfer to equilibrate temperatures of the thermocouple and particles, gave reliable results at high temperatures. The activation energy was 102 kJ/mol. Porosimeter data verified the large increase in pore volume (from 0.03 to 0.39 × 10−3 m3/kg) on converting the NaHCO3 particles to Na2CO3. First-order kinetics were observed up to high conversions, after which the apparent order decreased. However, the sodium bicarbonate could be completely converted to Na2CO3.

Journal ArticleDOI
TL;DR: The thermal unimolecular decompositions of benzaldehyde (BA), crotonaldehyde (CA), and furfural (FA) have been investigated in a flow reactor at very low pressures by modulated beam mass spectrometry above 1040 K as discussed by the authors.
Abstract: The thermal unimolecular decompositions of benzaldehyde (BA), crotonaldehyde (CA), and furfural (FA) have been investigated in a flow reactor at very low pressures by modulated beam mass spectrometry above 1040 K. Each reaction proceeds by a different mechanism. Whereas BA decomposes by C(O)-H bond fission CA readily undergoes decarbonylation to propene via a three-center transition-state reaction. FA decomposition into vinylketene and CO involves ring opening followed by H-atom transfer in the resulting biradical. Overall high-pressure Arrhenius parameters for the three reactions are derived from kinetic data.

Journal ArticleDOI
TL;DR: A kinetic and mechanistic study of the thermal decomposition of copper(II) malonate has been completed in which the rate measurements have been complemented with microscopic and analytical observations for salt that was partly decomposed to various known extents as discussed by the authors.
Abstract: A kinetic and mechanistic study of the thermal decomposition of copper(II) malonate has been completed in which the rate measurements have been complemented with microscopic and analytical observations for salt that was partly decomposed to various known extents. Plots of the fractional reaction ($\alpha$) against time for the isothermal reactions were approximately sigmoid but were distorted by a significant diminution in rate at the half-way stage ($\alpha \approx$ 0.5). Microscopic observations gave evidence that local fusion occurred soon after the onset of reaction, so that the initial acceleratory behaviour cannot be ascribed to a solid-state nucleation and growth process. From analytical measurements it is concluded that decomposition proceeds to completion by two distinct reactions, involving a stepwise cation reduction: Cu$^{2+}\rightarrow$ Cu$^+\rightarrow$ Cu$^0$. The relatively slower rate of the second reaction accounts for the marked diminution in slope of the $\alpha$-time plots after $\alpha$ = 0.5. The first reaction, copper(II) malonate decomposition, is characterized by a prolonged acceleratory process that obeys the exponential equation ($\ln \alpha$ = kt). This is explained by autocatalytic behaviour in which anion breakdown is promoted by acetate, a reaction product, thus (d$\alpha$/d$t$) = $k\alpha$. Separate experiments confirmed that added copper(II) acetate accelerated the reaction. The decomposition of copper(II) malonate was accompanied by partial fusion, and gas evolution within the viscous melt resulted in the development of an intracrystalline froth-like texture. Such partial melting was, however, localized within the reactant and the sizes and shapes of crystallites did not change markedly during reaction, so that product particles were pseudomorphic with those of the reactant. The final, short deceleratory phase of the first reaction overlapped with the onset of the second reaction. The second reaction was deceleratory throughout and obeyed first-order kinetics. Product acetate was not formed and the decomposition was evidently not influenced by the concurrent breakdown (0.5 < $\alpha$ < 0.75) of acetate remaining after the first reaction. The froth-like structure of the coherent matrix of the residue was retained unchanged between 0.5 < $\alpha$ < 1.0. The immobile component of this residual material was identified as a carbonaceous phase, the product copper atoms possessed sufficient mobility to aggregate in the form of metallic crystallites. Reaction mechanisms to account for the observations are proposed and are discussed with reference to the complementary kinetic, microscopic, and analytical data.

Journal ArticleDOI
TL;DR: Water and acetate solutions were irradiated under argon by 300 kHz ultrasonic waves and oxygen and succinic acid was found as a product of the attack of OH radicals on acetate, and CO2 and CO became the predominant products of sonolysis.
Abstract: Water and acetate solutions were irradiated under argon by 300 kHz ultrasonic waves. Oxygen was found to be generated besides the products H2 and H2O2, already known. In the presence of acetate the O2 yield decreased rapidly while that of H2O2 decreased more slowly. Succinic acid was found as a product of the attack of OH radicals on acetate. Appreciable amounts of glyoxylic and glycolic acid and smaller amounts of formaldehyde and carbon dioxide were also detected. They resulted from the reaction of sonolytically generated oxygen with CH2CO2- radicals, produced upon attack of OH on acetate. Methane was a minor product of sonolysis. At acetate concentrations above 0.4 mol dm-3 CO2 and CO became the predominant products of sonolysis. This is explained by a second kind of action of ultrasound on dissolved acetate, i.e. by a thermal decomposition. This decomposition is possibly facilitated by radical attack on acetate. The results are discussed in terms of a 'structured hot spot' model, in which three regions for the occurrence of chemical reactions are postulated: a hot gaseous nucleus, an interfacial region with radial gradient in temperature and local radical density; and the bulk solution at ambient temperature.

Journal ArticleDOI
TL;DR: In this paper, a qualitative correlation exists between the average N-N bond distance and the average frequency of the NO/sub 2/ asymmetric stretch in nitramines containing C/Sub 2/NNO/sub2/ units.
Abstract: A qualitative correlation exists between the average N-N bond distance and the average frequency of the NO/sub 2/ asymmetric stretch in nitramines containing C/sub 2/NNO/sub 2/ units. Compounds containing long N-N bonds (high nu/sub as/(NO/sub 2/)) tend to liberate considerable NO/sub 2/ when they are rapidly heated. Other decomposition products replace or are in competition with NO/sub 2/ for nitramines having shorter N-N bonds (lower nu/sub as/(NO/sub 2/)). These conclusions are bolstered by rapid-scan infrared spectroscopy studies of the initial gas decomposition products from 2,4,6,8-tetranitro-3,3,7,7-tetrakis(trifluoromethyl)-2,4,6,8-tetraazabicyclo(3.3.0)octane and its 2,6-dinitro analogue. The initial gas products evolved from the tetranitro compound are relatively independent of pressure (1-1000 psi) suggesting that N-N bond homolysis is the initial fast step that dominates thermal decomposition.

Journal ArticleDOI
TL;DR: In this article, the adsorption and decomposition of 1-propanol, 1-butanol, and 2butanol on polycrystalline ZnO has been investigated using temperature-programmed desorption (TPD).

Journal ArticleDOI
TL;DR: In this article, simultaneous thermal analyses were performed on samples of five typical compounds based on poly(vinyl chloride) in three main breakdown stages, the first accounting for over 60% of the pure resins and for over 50 % of the other compounds.

Journal ArticleDOI
TL;DR: In this paper, the authors propose a par decomposition thermique de N 2 H 5 Fe(N 2 H 3 COO) 3 •H 2 O et Fe(n 2 H 4 ) 2
Abstract: Preparation par decomposition thermique de N 2 H 5 Fe(N 2 H 3 COO) 3 •H 2 O et Fe(N 2 H 3 COO) 2 (N 2 H 4 ) 2