Conditions Of Thermal Decomposition Research Articles

Generation of gaseous mixtures of ethene on the basis of thermal decomposition of compound bonded to silica gel surface - Single and multipoint calibration of a thermal decomposition-gas chromatography system

The paper presents a new method of determination of a volatile component (ethene) of gaseous standard mixtures obtained by thermal decomposition of a suitable surface compound. This method is based on a simple mathematical relationsphip (function of a single variable). The amount of the analyte generated (under given, chosen conditions of thermal decomposition) per unit of mass of the source material has been determined exclusively on the basis of measuring the standard generation time.V

Generation of gaseous mixtures of ethene on the basis of thermal decomposition of compound bonded to silica gel surface – Single and multipoint calibration of a thermal decomposition-gas chromatography system

The paper presents a new method of determination of a volatile component (ethene) of gaseous standard mixtures obtained by thermal decomposition of a suitable surface compound. This method is based on a simple mathematical relationsphip (function of a single variable). The amount of the analyte generated (under given, chosen conditions of thermal decomposition) per unit of mass of the source material has been determined exclusively on the basis of measuring the standard generation time.V

Heteroorganic betaines. 6. Structure and reactivity of silicon-containing organophosphorus betaines with the –S—Si—C—P+ fragment: a DFT study

The structures of silicon-containing organophosphorus betaines –S—SiR1 2—CR2 2—P+R3 3 and their ylide isomers were calculated using the density functional approach with the gradient-corrected PBE functional and extended TZ2P basis set. Three possible pathways of thermal decomposition of these betaines were analyzed. These are (i) cleavage of the central C—Si bond with the formation of a Wittig ylide and silanethione, (ii) intramolecular nucleophilic S N-substitution with elimination of phosphine PR3 3 and the formation of silathiirane (the Corey—Chaikovscky transformation), and (iii) a Wittig-type decomposition followed by the formation of substituted silaethylene. The structures of products and transition states of these reactions were calculated. The cis-gauche conformation of the –S—Si—C—P+ fragment of betaines was found to be the most stable. This is in agreement with the results of X-ray diffraction study and can be rationalized by strong Coulomb attraction between the cationic and anionic centers. The betaines are stable toward retro-Wittig thermal decomposition. The Corey—Chaikovscky formation of thiirane is preferable under conditions of thermal decomposition. Retro-Wittig-type decomposition of betaines followed by the formation of silanethione is favored by intra- and intermolecular coordination of donor ligands.

PbTiO3 preparation through coprecipitation methods

Precursor powders to obtain SrTiO3 were prepared by using 8-hydroxyquinoline precipitant agent. The residues from the thermal decomposition, followed by TG/DTG/DTA, were characterized by XRD and it could be verified that the mixed oxides could be obtained varying the thermal decomposition conditions like atmosphere and heating rate. However, the morphology and crystallinity of these residues is highly affected by such variations. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Analysis of Fire Gases Released from Polyurethane and Fire-Retarded Polyurethane Coatings

We have investigated the analysis of smoke and gases generated under various thermal decomposition conditions of polyurethane (PU) and fire retarded polyurethane coatings. The use of Fourier Transform Infrared Analysis has allowed the continuous detection of a number of the most important fire gases. We have shown that the addition of ammonium polyphosphate (APP) in PU sharply decreases at the same time the emission of toxic gases such as CO or HCN, the optical density of smoke, the weight loss and the formation of soot. Expandable graphite, when added in PU, enables a decrease in toxic gases in a lower proportion than APP. In addition, we note that oxidation reactions strongly influence the nature of the combustion gases in case of fire.

Heteroelectrocyclic reaction of 4‐azido‐3‐hydrazonoalkyl‐quinolines to 2‐arylaminopyrazolo[4,3‐c]quinolones

Abstract4‐Azido‐3‐acylquinolones 4 obtained from 4‐hydroxy derivatives 1 via tosylates 3 or chlorides 5, reacted with arylhydrazines 6 to generate 4‐azido‐3‐hydrazonoalkylquinolines 7. Thermolysis of 7 gave ring closure products which were assigned to 2‐arylaminopyrazolo[4,3‐c]quinolones 10. The thermal decomposition conditions of the azides 4 and 7 were studied by differential scanning calorimetry (DSC).

Thermal cyclization of 4‐azido‐3‐nitropyridines to furoxanes

Abstract4‐Chloro‐3‐nitro‐2‐pyridines 3 and 10, obtained from 4‐hydroxy‐2‐pyridones 1 and 8 after nitration and chlorination, gave with sodium azide 4‐azido‐3‐nitropyridines 4 and 11, which cyclized on thermolysis to furoxans 6 and 12. Desoxygenation of the furoxan 6 with triphenylphosphane gave the furazan 7. Thermal decomposition conditions of the azide 4 and the desoxygenation reaction of 6 to 7 were studied by differ ential scanning calorimetry (DSC).

Decomposition Pathways of Some 3,6-Substituted s-Tetrazines

The thermal and electron-impact (EI) stabilities of eight 3,6-disubstituted-1,2,4,5-tetrazines were examined. Major EI peaks were also investigated by tandem mass techniques to construct fragmentation pathways. Tetrazine ring structures were not maintained under electron impact ionization nor under conditions of thermal decomposition. Under electron impact, the tetrazines examined shared the same initial fragmentation pathways: elimination of two of the nitrogen atoms as N2 from the tetrazine ring and cleavage of the remaining N−N bond. This pathway was also applicable to thermal decomposition; however, the main route involved dissociation of the substituent group, in some cases assisted by proton transfer.

SrTiO 3 preparation through coprecipitation methods

Precursor powders to obtain SrTiO 3 were prepared by using 8-hydroxyquinoline precipitant agent. The residues from the thermal decomposition, followed by TG/DTG/DTA, were characterized by XRD and it could be verified that the mixed oxides could be obtained varying the thermal decomposition conditions like atmosphere and heating rate. However, the morphology and crystallinity of these residues is highly affected by such variations.

Synthesis and structural characterization of isocyanate, amido and imido niobocene derivatives: crystal structures of [Nb(η5-C5H4SiMe3)2Cl(κ2N,C-OCNPh] and [{Nb(η5-C5H4SiMe3)2Cl}2(μ-1,3-N2C6H4)] †

The niobium complex [{Nb(η5-C5H4SiMe3)2Cl}2] 1 reacted with phenyl isocyanate, 1,3- and 1,4-phenylenediisocyanate to give the corresponding complexes [Nb(η5-C5H4SiMe3)2Cl(κ2N,C-OCNPh)] 2, [{Nb(η5-C5H4SiMe3)2Cl}2{κ2N,C-µ-1,3-(OCN)2C6H4}] 3 and [{Nb(η5-C5H4SiMe3)2Cl}2{κ2N,C-µ-1,4-(OCN)2C6H4}] 4, respectively. The spectroscopic data were not sufficient unequivocally to differentiate between the presence of a κ2C,N or κ2C,O co-ordination mode. However the crystal structure of 2 showed it to have κ2C,N co-ordination. Complexes 3 and 4 have an analogous structure in which two metal centres are linked through an aryl ring containing a diisocyanate ligand. The reactivity of these complexes under reduction and thermal decomposition conditions was examined. Complexes 2–4 with Na/Hg underwent a reduction at each metal centre followed by protonation to afford the corresponding [Nb(η5-C5H4SiMe3)2(OCHNPh)] 5, [{Nb(η5-C5H4SiMe3)2}2{µ-1,3-(OCHN)2C6H4}] 6 and [{Nb(η5-C5H4SiMe3)2}2{µ-1,4-(OCHN)2C6H4}] 7. The imido [Nb(η5-C5H4SiMe3)2Cl(NPh)] 8 and diimido derivatives [{Nb(η5-C5H4SiMe3)2Cl}2(µ-1,3-N2C6H4)] 9 and [{Nb(η5-C5H4SiMe3)2Cl}2(µ-1,4-N2C6H4)] 10 were isolated by heating 2, 3 or 4 or alternatively by treating 1 with the appropriate amount of the corresponding aniline, 1,3- or 1,4-phenylenediamine, respectively. The molecular crystal structure of 9 was determined by single-crystal diffractometry. It contains two bent niobocene units linked by a 1,3-diimidophenylene ligand, with the niobium atoms slightly deviating from the plane formed by this ligand. Complexes 8–10 reacted with Grignard reagents MgRCl (R = Me, Et or Pri) or MgMe2 in tetrahydrofuran solution to give the corresponding substitution products [Nb(η5-C5H4SiMe3)2R(NPh)] (R = Me 11, Et 12 or Pri 13), [{Nb(η5-C5H4SiMe3)2R}2(µ-1,3-N2C6H4)] (R = Me 14, Et 15 or Pri 16) and [{Nb(η5-C5H4SiMe3)2R}2(µ-1,4-N2C6H4)] (R = Me 17, Et 18 or Pri 19). The reaction of 8–10 with Na/Hg in appropriate molar ratios afforded the corresponding hydride complexes [Nb(η5-C5H4SiMe3)2H(NPh)] 20, [{Nb(η5-C5H4SiMe3)2H}2(µ-1,3-N2C6H4)] 21 and [{Nb(η5-C5H4SiMe3)2H}2(µ-1,4-N2C6H4)] 22. Finally, the monoimido complexes 8 and 11–13 were easily protonated with 1 equivalent of HBF4·OEt2 to give, in one step, the corresponding amido cationic complexes [Nb(η5-C5H4SiMe3)2X(NHPh)]+ [BF4]– (X = Cl 23, Me 24, Et 25 or Pri 26). The structures of the different families of complexes isolated were determined by spectroscopic methods.

Preparation, properties and thermal decomposition of rare earth element complexes with 3,5-dihydroxybenzoic acid

The conditions of the formation of rare earth element 3,5-dihydroxybenzoates have been studied; their quantitative composition and solubilities in water at 293 K have been determined. The IR spectra of the hydrated complexes have been recorded and their thermal decomposition in air determined. During heating, the hydrated complexes Ln(C 7H 5O 4)O 3· nH 2O( n = 4 for LaPr, n = 7 for in Y, NdLu) lose water of crystallization in one step and then the anhydrous complexes decompose directly to oxides (SmGd, DyLu, Y) or with intermediate formation of Ln 2O 2CO 3 (La, Nd). The conditions of thermal decomposition of 2,4- and 3,5-dihydroxybenzoates are compared.

Thermal decomposition of scandium(III) 2-chloro-, 30chloro, 4-chloro- and 2,4-dichlorobenzoates in an air atmosphere

The conditions of thermal decomposition of hydrated scandium(III) chlorobenzoates were studied. On heating, the carboxylates decompose in many steps. The hydrated complexes first lose water of crystallization in one or two steps and then anhydrous compounds are transformed to Sc2O3 with formation of Sc2O(CO3)2 intermediate. The dehydration of the complexes is accompanied by an endothermic effect and the decomposition of anhydrous complexes by strong endothermic effects. The anhydrous complexes are melted at 255–300°C.

熱分解法によるマグネタイトの生成

The effect of thermal decomposition conditions on the powder properties of Fe3O4 has been investigated, in order to obtain fine Fe3O4 powder. It is shown that the one phase Fe3O4 could be obtained under the following conditions, water vapor pressure is 0.1MPa, and thermal decomposition temperature is between 550 and 800°C. Fine Fe3O4 powder could be obtained by introducing FeCls or O2 at the thermal decomposition of FeCl2. It was found that FeO was not formed when FeCl3 was introduced.

Cubic and hexagonal tin tungsten bronzes synthesized from peroxo-polytungstic acid

Peroxo-polytungstic acid (PTA) is used for preparing the amorphous tin peroxo-polytungstate (Sn-PTA), which can under different thermal decomposition conditions (directly in a reducing atmosphere H 2, or first in air then in H 2) produce two kinds of bronzes: a black hexagonal tin tungsten bronze (HTB) Sn 0.23WO 3 with a = 7.4285 (5), c = 3.800 (3) A ̊ and a cubic tin tungsten bronze Sn 0.23WO 3 with a = 3.79743 (6) A ̊ . The powder X-ray and electron diffraction studies are in agreement. It was also observed that the redox reactions between tin tungsten bronzes (both phases) and tin tungstates are reversible.

Synthesis and properties of 2,2′-dipyridyl and 4,4′-dipyridyl complexes with thulium salts

New complexes of 2,2′-dipyridyl and 4,4′-dipyridyl with thulium salts TmX3 (whereX=Cl−, Br−, NO 3 − , NCS−, and ClO 4 − ) have been prepared and their solubilities in water at 21 °C were determined. The IR spectra of these compounds are discussed. The conditions of thermal decomposition of the complexes were also studied.

Initial compounds for obtaining high-temperature superconducting films by the CVD-method

The effect of the ligand and the metal on the volatility of complexes that are used to obtain Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconducting films by chemical vaporphase deposition method are considered. The thermodynamic parameters of evaporation of these compounds, their heat and temperature of sublimation, and the conditions of thermal decomposition and storage are presented.

Zr-V-Fe alloys as efficient hydrogen getters

Results are presented on phase equilibria and hydrogen uptake characteristics for alloys in the Zr-V-Fe system. Effects have been determined from combining these alloys with scandium, lanthanum, and aluminum oxide. The hydrogenation uptake kinetics can be improved if the alloy contains Zr3V3O, and the hydrogen capacity is increased if lanthanum or scandium is added. The thermal decomposition conditions for the hydrogenated alloys have been examined.

Thermal decompositions of lanthanum and lanthanide salts of sebacic acid

The conditions of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm(III), Eu, Gd, Tb(III), Dy, Ho, Er, Tm, Yb and Lu sebacates have been studied. When heated in air atmosphere, the sebacates of La and lanthanides with general formula Ln2(C10H16O4)3·nH2O, wheren=6−24, lose some crystallization water molecules in one or two steps at 323–343 K and are then dehydrated and decomposed simultaneously to the oxides Ln2O3, CeO2, Pr6O11 and Tb4O7. The oxides are formed over the range of temperature 783 K (CeO2)−1073 K (Nd2O3).

The role of enhanced activity sites in hexane cracking over ZSM-5 zeolites

Hexane cracking over various ZSM-5 zeolites was studied. In agreement with previous reports, it is shown that HZSM-5 with different SiO2/Al2O3ratio, when prepared in the absence of water vapor, contain acidic centers equal in activity and selectivity. Enhanced activity sites that are generated under certain conditions of steaming or thermal decomposition of NH4-ZSM-5 zeolite (SiO2/Al2O3 = 34) display the remarkably high activity in hydrogen transfer steps of the reaction. During coke formation, these sites are deactivated more rapidly than are normal acidic centers of ZSM-5-bridging OH groups

Thermal decomposition of rare earthp-aminosalicylates in air atmosphere

The conditions of thermal decomposition of thep-aminosalicylates of Y, La and the lanthanides from Ce(III) to Lu have been studied. On heating, the hydrated complexes of La and the light lanthanides decompose to the oxides with the intermediate formation of Ln2[H2N·C6H3(O)COO]3. Only the complex of La decomposes to La2O3 through La2[H2N·C6H3(O)COO]3 and La2O2CO3. The anhydrous complexes of the heavy lanthanides decompose directly to the oxides, whereas the anhydrous complex of Y decomposes to Y2O3 via Y2[H2N·C6H3(O)COO]3 formation. During heating, the hydrated complexes lose crystallization water and decompose simultaneously, and the endothermic effect of dehydration is masked by the strong exothermic effect of burning of the organic ligand.