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Gaseous Species (gaseous + species)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Interaction of a phosphorus-based FR, a nanoclay and PA6,Part 1: Interaction of FR and nanoclay

FIRE AND MATERIALS, Issue 6 2009
Alwar Ramani
Abstract The thermal decomposition of organophosphorus fire-retardant (OP1311) and/ or organonanoclay (Cloisite 30B) is hereby investigated employing thermogravimetric analysis (TGA), to give an insight into their intrinsic behaviour and interaction in polymer nanocomposites for fire safety applications, because the addition of OP1311 and Cloisite 30B in Polyamide 6 (PA6) seems to have a synergistic effect on the thermal decomposition of PA6 (part 2 of the paper). An important objective of this research was to determine to what extent phosphorus components escape in the gaseous phase, which will affect the heat of combustion of the fire-retarded polymer. The decomposition products arising from pyrolysis and combustion are investigated by means of Fourier transform infrared spectroscopy. Under pyrolytic conditions, the inclusion of Cloisite 30B into OP1311 (FR) shows a synergistic effect on the initial mass loss at low temperature of ,280,420°C and leads to the acceleration of the thermal degradation process. While the DTG curve of Cloisite 30B shows two distinct degradation peaks (steps) that of OP1311 and OP1311 plus Cloisite 30B show four degradation steps. TGA measurements of OP1311 in nitrogen show more mass loss than in air, whereas Cloisite 30B gives similar amounts of mass loss in air and nitrogen. In nitrogen, the major evolved gaseous species from Cloisite 30B alone are hydrocarbons, 2-(diethylamino)ethanol and water, whereas the evolved gases from that of OP1311 at ,320°C are mainly water, at ,420°C, carbon dioxide, water and ammonia and at 480,570°C diethylphosphinic acid. Under thermo-oxidative conditions, the gases evolved are mainly carbon dioxide and water from both Cloisite 30B and OP1311. Copyright © 2009 John Wiley & Sons, Ltd. [source]

From monosilane to crystalline silicon, part II: Kinetic considerations on thermal decomposition of pressurized monosilane

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2006
J. O. Odden
Kinetic aspects of the thermal decomposition of monosilane at 690,830 K and initial pressures of 0.1,3.7 MPa in a free-space reactor are considered. Neglecting the preparatory initiation period for the reaction (which is difficult to evaluate under the present dynamic conditions), the onset temperature for the decomposition is stipulated to some 700,710 K, independent of the initial monosilane pressure. The overall reaction appears to be of first order throughout the progressing decomposition process. We observe considerably lower reaction rates under the high-pressure conditions than existing models in the literature suggest. A modified model is proposed that simulates the observed reaction rates within ±1% and moreover predicts credible concentrations of the involved gaseous species. A key feature of the modified model is incorporation of two third-body assisted surface reactions, which generate monosilane from disilane and disilane from trisilane. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 309,321, 2006 [source]

Kinetic model for noncatalytic supercritical water gasification of cellulose and lignin

AICHE JOURNAL, Issue 9 2010
Fernando L. P. Resende
Abstract This article reports the first kinetics model for Supercritical Water Gasification (SCWG) that describes the formation and interconversion of individual gaseous species. The model comprises 11 reactions, and it uses a lumping scheme to handle the large number of intermediate compounds. We determined numerical values for the rate constants in the model by fitting it to experimental data previously reported for SCWG of cellulose and lignin. We validated the model by showing that it accurately predicts gas yields at biomass loadings and water densities not used in the parameter estimation. Sensitivity analysis and reaction rate analysis indicate that steam-reforming and water,gas shift are the main sources of H2 in SCWG, and intermediate species are the main sources of CO, CO2, and CH4. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Cracking study of pentakis(dimethylamino)tantalum vapors by Knudsen cell mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2010
Perrine Violet
Organometallic molecules are commonly used as gaseous precursors in Atomic Layer Deposition/Chemical Vapor Deposition (ALD/CVD) processes. However, the use of these molecules, which are generally thermally unstable at temperatures close to the deposition temperature, requires an understanding of their gas-phase chemical behavior. The thermal cracking of the gaseous precursor, pentakis(dimethylamino) tantalum (PDMAT), generally adopted in the ALD/CVD TaN deposition processes, has been studied in the temperature range from 343 to 723K using a specific reactor coupled with a high-temperature mass spectrometer. This reactor , built as tandem Knudsen cells , consists of two superimposed cells. The first stage reactor , an evaporation cell , provides an input saturated vapor flow operating from room temperature to 333K. The second stage cell, named the cracking cell, operated from 333 to 723K in the present study. Experiments showed the appearance of many gaseous species when the cracking temperature increased and, in particular, dimethylamine, corresponding to the saturated organic branches of PDMAT. Decomposition products of the HNC2H6 branch were observed at relatively high temperature, namely above 633K. This gas-phase study , as for the preceding saturated one , shows the presence of oxygen-containing molecules in PDMAT cracked vapor. Thus, it explains the systematic presence of oxygen contamination in the deposited TaN films observed in ALD/CVD industrial processes. Copyright © 2010 John Wiley & Sons, Ltd. [source]