Showing papers on "Thermal decomposition published in 1988"

Preparation of spherical, monosized Y2O3 precursor particles

Abstract: Spherical, monosized yttria precursor particles were obtained by homogeneous precipitation in aqueous solutions by reaction with the thermal decomposition products of urea. Increasing [Y 3+ above 0.05 M resulted in a deviation from spherical morphology and caused agglomeration of particles. Over the concentration range studied, excess urea did not affect particle morphology, but increased the yield. Increasing aging time appeared to increase particle size as well as to improve yield, as long as the urea was not depleted. The approximate chemical composition of the precipitate was YOHCO 3 . The YOHCO 3 particles formed were amorphous to X-rays, and underwent a two-stage thermal decomposition, first forming Y 2 O 2 CO 3 near 180°C, and then cubic Y 2 O 3 above 610°C. Generation of CO 3 2− appeared to be crucial to the formation of the solid phase. Heating the aqueous yttrium solution with trichloroacetic acid (CCl 3 COOH) instead of urea as the precipitating agent produced a solid phase, while heating the same solution with formamide (HCONH 2 ) substituted for urea formed no precipitate.

Production of high-quality amorphous silicon films by evaporative silane surface decomposition

Abstract: High‐quality hydrogenated amorphous silicon films (a‐Si:H) have been produced by decomposition of low‐pressure silane gas on a very hot surface with deposition on a nearby, typically 210 °C substrate. A high‐temperature tungsten filament provides the surface for heterogeneous thermal decomposition of the low‐pressure silane and subsequent evaporation of atomic silicon and hydrogen. These evaporated species (primarily) induce a‐Si:H growth on nearby substrates which are temperature controlled using a novel substrate holder. The light and dark conductivities, optical band gap, deposition rates, and light‐soaking effects of preliminary films are reported. The decomposition‐evaporation process has been examined using a mass spectrometer to directly detect the decomposition rate and the evaporated radical species. Based on this data and other information, a simplified model for the deposition process is suggested. The excellent film quality and the attributes of the deposition process make this technique, which was originally suggested by Wiessman, viable for the fast rate, large‐area deposition of a‐Si:H for solar cells and other applications.

Thermal decomposition of 1,2 butadiene

Abstract: The thermal decomposition of 1,2 butadiene has been studied behind reflected shock waves over the temperature and total pressure ranges of 1300–2000 K and 0.20–0.55 atm using mixtures of 3% and 4.3% 1,2 butadiene in Ne. The major products of the pyrolysis are C2H2, C4H2, C2H4, CH4 and C6H6. Toluene was observed as a minor product in a narrow temperature range of 1500–1700 K. In order to model successfully the product profiles which were obtained by time-of-flight mass spectrometry, it was necessary to include the isomerization reaction of 1,2 to 1,3 butadiene. A reaction mechanism consisting of 74 reaction steps and 28 species was formulated to model the time and temperature dependence of major products obtained during the course of decomposition. The importance of C3H3 in the formation of benzene is demonstrated.

Ferromagnetic alloy for curie point type thermal decomposition device

Abstract: PURPOSE:To obtain an alloy which permits quantitative thermal decomposition of the entire sample at the Curie point temp. of the alloy by mixing the granular ferromagnetic alloy with the flaky sample and molding the same to a prescribed shape, then using such molding. CONSTITUTION:The sample 2 of the flaky or powder org. high-polymer compd. is dispersed into the granular ferromagnetic alloy 1 and is molded by pressing. The alloy 1 and the org. high-polymer compd. of the sample are thereby thoroughly and tightly adhered to each other and the entire sample is heated up to the Curie point possessed by the alloy in the extremely short time, by which the quantitative thermal decomposition at said temp. is permitted.

Synthesis and properties of bismaleimide resins containing ether bonds

Abstract: New bismaleimides containing ether bonds were prepared. The thermal properties of the bismaleimides were investigated by differential scanning calorimetry (DSC). The effects of structure of the bismaleimides and curing conditions on the thermal and mechanical properties of the cured resins such as initial decomposition temperature (Td), glass transition temperature (Tg), and flexural strength were studied. The introduction of ether bonds to bismaleimide resins decreased the brittleness of the resins without reductions in their heat-resistant properties.

Electron beam induced surface nucleation and low‐temperature decomposition of metal carbonyls

Abstract: The kinetics of low‐energy electron beam induced metal film nucleation have been investigated. Experiments performed were the deposition of Fe and Cr from Fe(CO)5 and Cr(CO)6, respectively. It was found that the activation energy for the autocatalytic thermal decomposition of these compounds was lower than the activation energy for decomposition on Si surface. The autocatalytic activation energies were measured as 0.14 eV for Fe(CO)5 and 1.02 eV for Cr(CO)6. The electron beam induced nucleation, together with the rapid autocatalytic decomposition, allowed for selective area metal film growth. A qualitative model based on classical nucleation theory describes well the effect of electron irradiation in inducing film growth. The electron beam induced nucleation step has been modeled in more detail and shows a t4 dependence for the early stages of film growth, in agreement with the observed data.

Low‐temperature deposition of zirconium and hafnium boride films by thermal decomposition of the metal borohydrides (M[BH4]4)

Abstract: Conductive (150 μΩ cm), adherent films of zirconium and hafnium borides have been deposited on various substrates by the low‐temperature (100–270 °C) thermal decomposition of Zr[BH4]4 and Hf[BH4]4. Auger electron spectroscopy of these films shows that their composition is ZrB2 and HfB2. The film surfaces are oxidized and slightly carbon contaminated. However, the bulk contains less than 1 at. % C or O. This synthesis is by far the lowest temperature preparation of these materials (plasma‐enhanced chemical vapor deposition of TiB2 requires 480–600 °C) and holds great promise for the use of these materials in electronics applications.

Inhalation Toxicity of Carbon Monoxide and Hydrogen Cyanide Gases Released During the Thermal Decomposition of Polymers

Abstract: The acute lethality of thermal decomposition products of various polymeric materials was investigated using bioassay procedures and a small scale com bustion apparatus. The concentrations of pertin...

Chemical vapor deposition of transistion metals

Abstract: Coatings of Group IIA metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula (I) ##STR1## wherein M is a transition metal of Group VB, VIB, VIIB or VIII, R1 is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, R2 is a hydrogen or lower alkyl or alkenyl radical, n is the valence of M and is an integer from 2 to 4, and p is an integer from 0 to (n-1), is contacted with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula I is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as manganese telluride can be deposited from a manganese compound of formula I and a heat decomposable tellurium compound under nonoxidizing conditions.

Analysis of autoxidized fats by gas chromatography-mass spectrometry: X. Volatile thermal decomposition products of methyl linolenate dimers.

Abstract: High-molecular weight compounds previously were found to be important secondary products from autoxidation of polyunsaturated fatty esters. The contribution of dimers to oxidative deterioration was investigated by analyzing their volatile thermal decomposition products by capillary gas chromatography-mass spectrometry. Dimers were isolated by gel permeation chromatography from autoxidized linolenate and from the corresponding monohydroperoxides, cyclic peroxides and dihydroperoxides. Major volatile decomposition products identified from these oxidative dimers were similar to those formed from the corresponding monomeric hydroperoxides. However, dimers from linolenate hydroperoxides produced more propanal and methyl 9-oxononanoate than the corresponding monomers but less methyl octanoate and much less or no 2,4-heptadienal and 2,4,7-decatrienal. Significant differences in minor volatile products also were observed between dimeric and monomeric products of methyl linolenate oxidation compounds. Mechanisms are suggested for the formation of volatile decomposition products from different dimeric structures. These dimers are believed to be important sources of volatile compounds contributing to flavor and oxidative deterioration of fats.

Direct Preparation of Uniformly-Distributed YBa2Cu3O7-xPowders by Spray-Pyrolysis

Abstract: Fine powders of the compound YBa2Cu3O7-x have been prepared directly by the spray-pyrolysis of aqueous solutions of corresponding metal nitrates. The powders obtained in a temperature range of 900 to 1000°C were spherical and their diameters were uniformly distributed below 1 µm. The crystallinity of these powders was increased with increasing decomposition temperature; an orthorhombic single phase was indeed obtained at 1000°C. The sintered bodies from these powders showed the offset of superconducting transition at 84 K.