Showing papers on "Thermal decomposition published in 1975"

Thermal cis–trans isomerization and decomposition of polyacetylene

Abstract: Thermal cis-trans isomerization and decomposition of polyacetylene film prepared with a Ti(OC4H9)4–Al(C2H5)3 (Al/Ti = 4) system were investigated under inert gas or in vacuum by means of thermal analysis and infrared spectroscopy. Thermograms of differential thermal analysis of cis-polyacetylene revealed the existence of two exothermic peaks at 145 and 325°C and one endothermic peak at 420°C which were assigned to cis-trans isomerization, hydrogen migration accompanied with crosslinking reaction, and thermal decomposition, respectively. The isomerization was followed by infrared spectroscopy over the temperature range 75–115°C. The reaction did not obey simple kinetics. The apparent activation energy for the cis-trans isomerization was 17.0 kcal/mole for the polymer containing 88% cis configuration and increased with increasing trans content up to 38.8 kcal/mole for 80% trans content.

Simple thermal decomposition reactions for storage of solar thermal energy

Abstract: Simple thermal decomposition reactions have been investigated for the purpose of solar thermal energy storage. Ten criteria regarding the thermodynamics and kinetics of the reaction and the physical properties of the components of the reaction have been established. One particular reaction, the decomposition of ammonium hydrogen sulfate, has been evaluated in a preliminary manner and appears to satisfy all of the established criteria. The efficiency of storage is high and the decomposition occurs in the vicinity of 500°C. Other compounds such as ammonium halides, alkali and alkaline earth metal hydroxides, carbonates, sulfates and oxides have also been examined.

Low Temperature Deposition of Metal Nitrides by Thermal Decomposition of Organometallic Compounds

Abstract: Decomposition reaction of dialkylamides of boron, silicon, tin, titanium, zirconium, niobium, and tantalum was investigated. The amides of transition metals decomposed to the corresponding nitrides at 300~176 whereas those of boron, silicon, and tin yielded elemental deposits at higher temperatures. In the deposition of titanium nitride from titanium tetrakis(dimethylamide), two optimum temperatures at 400 ~ and at 800~ in nitrogen or hydrogen atmosphere were found, but in argon only low temperature deposition was possible. The low and high temperature processes are discussed in relation to mass spectral analysis of the exhaust gases formed at various decomposition temperatures of titanium amide. Metal nitrides are well known to have outstanding physical and chemical properties and have been prepared by the reactions of metal halides or hydrides with nitrogen + hydrogen or ammonia, or of metals with nitrogen (1). These reactions usually require temperatures higher than 1000~ which have limited the application of the nitrides as the useful coatings on many materials. Therefore, their preparation at lower temperature, where deformation of substrate materials can be avoided, should be important.

Thermal Decomposition in the Solid State

Abstract: The foundation of solid state decomposition kinetics is based on the well known theory of nucleation and nucleus growth put forward by Jacobs and Tompkins. It has now been shown that all the kinetic equations thus derived can be represented by a general differential form: dα/dt = kα1-p(1-α)1-q in which α, t and k are respectively the fractional decomposition, time and rate constant; while p and q are parameters lying between zero and unity inclusively. A method has been suggested to find p and q experimentally, thereby enabling one to find the appropriate kinetic form for the chemical decomposition. The conventional method involves the testing of various existing equations to the decomposition data. Different equations are found to fit over different ranges of the decomposition curve so that it is difficult to decide which is the correct kinetic equation for a particular reaction. The present approach however eliminates this complication.

The Thermal Decomposition of Methane. I. Kinetics of the Primary Decompositionto C2H6 + H2; Rate Constant for the Homogeneous Unimolecular Dissociation of Methane and its Pressure Dependence

Abstract: The pyrolysis of methane has been studied in a static system at temperatures of 995, 1038, 1068, and 1103 K and pressures from 25 to 700 Torr. It was concluded that the initial stages of the reacti...

Ruthenium dioxide: a new electrode material. II. Non-stoichiometry and energetics of electrode reactions in acid solutions

Abstract: RuO2 films on Ta and Pt as supports have been prepared by thermal decomposition of RuCl3 at different temperatures in various atmospheres. Bulk and surface electronic properties of these films have been deduced from their behaviour as electrodes with respect to reactions involving or not involving the adsorption of reactants and/or products, (for example Fe2+/Fe3+, I−/I2, H2/H+ and some simple organic reactions). Results indicate that the non-stoichiometry of the oxide film is a function of the temperature of preparation and also of the atmosphere of annealing. In particular, smaller fractions of Ru3+are obtained as the temperature of preparation is increased and/or the atmosphere of annealing is made more oxygenated. Kinetics of electrode reactions suggest an essentially metallic nature for RuO2 films. They behave very well with redox systems but exhibit poor electrocatalytic features in that rates of reactions involving adsorption steps are usually lower on RuO2 films than on noble metals. Possible reasons for this are discussed in detail.

Thermal Decomposition of EDTA, NTA, and Nitrilotrimethylenephosphonic Acid in Aqueous Solution

Abstract: The decomposition of ethylenediaminetetraacetic acid (EDTA) in water solution at 200 and 260 °C, nitrilotriacetic acid (NTA) at 260 and 293 °C, and of nitrilotrimethylenephosphonic acid (NTPO) at 2...

Some Factors Affecting the Decomposition of Three Commercial Zinc Organodithiophosphates

Abstract: Despite the widespread use of zinc organodithiophosphates (ZDP's) as antiwear additives, how the ZDP's perform their antiwear function is still vague. Thermal decomposition of ZDP's and the formation of a protective antiwear coating by the decomposition products is one popular theory; but the correlation between thermal decomposition temperature and antiwear performance leaves something to be desired. To determine if other factors influence ZDP behavior, bench decomposition studies were conducted on three commercial ZDP's in which the effects of oxygen, water, other additives in the blend, and the base oil were investigated. For these studies, the bulk oil changes were followed by infrared spectroscopy, volatiles formation by pressure measurements, solids formation by centrifugation and subsequent elemental analysis and surface coating formation on steel balls by x-ray fluorescence spectroscopy. It was found that the decomposition of ZDP's is affected by oxygen availability, water, other additives in the ...

Chemical Effects of Heat on Cellulose

Abstract: The mechanism of rupture of the glucosidic bond in the thermal decomposition of cellulose is examined, and data are given on the primary steps of formation of levoglycosan. The effect of inorganic components on carbon–carbon bond rupture and on the direction of decomposition is considered. Possible practical uses of the results are discussed. 54 references

Thermolysis of (2-oxacyclopentylidene)pentacarbonylchromium(0): evidence against free carbenes in thermal decomposition of metal–carbene complexes

Abstract: Thermolysis of (2-oxacyclopentylidene)pentacarbonylchromium(0)(I) gives mainly the dimer and no cyclobutanone, a product characteristic of a free carbene; a bimolecular mechanism for decomposition of (I) is proposed based on kinetic studies.

The thermal decomposition of alkali metal formates

Abstract: The thermal decompositions of lithium, sodium, potassium, rubidium and caesium formates were investigated by a complex dynamic thermoanalytical method. The ratio of the products in reactions resulting in alkali metal carbonates and oxalates depended variously on the atmosphere used. Differences were found compared to isothermal investigations, in that the catalytic effects of bases could not be observed and the oxalate-conversion was lower. The formation of oxalate did not occur in the cases of lithium and caesium formates; the order for the other salts was sodium formate rubidium formate.

Kinetic analysis of thermogravimetric data. X: Thermal decomposition of some tris-ethylenediamine-cobalt(III) and chromium(III) complexes

Abstract: A study was made of the thermal decompositions of 22 derivatives of[M(en)3]X3 type complexes. Partial de-amination leading to the formation of[M(en)2X2]X type complexes occurs in the case ofM=Cr(III) ifX=Cl, Br, I orNCS, but in the case ofM=Co(III) it is possible only ifX=Cl. In other cases redox reactions hinder the formation of stable intermediates. Kinetic parameters were derived for the dehydration of 19 compounds.The validity of a linear kinetic compensation law was observed. The dependence of the kinetic compensation parameters on the nature of the thermal process is discussed.RésuméOn a étudié la décomposition thermique de 22 dérivés des complexes du type[M(en)3]x3. La réaction de désamination partielle qui amène la formation des complexes du type[M(en)2X2]X se produit dans le cas deCr(III), siX=Cl, Br, I ouCNS, mais dans le cas deCo(III) elle n'est possible que siX=Cl. Dans les autres cas, la formation d'intermédiaires stables est empêchée par des réactions d'oxydo-réduction. On a calculé les paramètres cinétiques pour la déshydratation de 19 composés.On a constaté la validité d'une loi de compensation cinétique linéaire. On discute la manière dont les paramètres de compensation cinétique dépendent de la nature du processus thermique.ZusammenfassungDie thermische Zersetzung von 22 Derivaten des Komplextyps[M(en)3]X3 wurde untersucht. Die partielle Deaminierungsreaktion, welche zur Bildung von Komplexen des Typs[M(en)2X2]X führt, tritt beiCr(III)-Komplexen in dem FalleX=Cl, Br, I oderNCS auf, ist aber beiCo(III)-Komplexen nur beiX=Cl möglich. In anderen Fällen wird die Bildung von stabilen Zwischenprodukten durch Redoxreaktionen verhindert. Für die Dehydratation von 19 Verbindungen wurden kinetische Parameter abgeleitet.Die Gültigkeit eines linearen kinetischen Kompensationsgesetzes wurde beobachtet. Die Abhängigkeit kinetischer Kompensationsparameter von der Beschaffenheit des thermischen Vorganges wird erörtert.РезюмеИсследован терморас пад 22 производных комплексов типа [М(ен)3] Х3. Реакция, приводящая к образов анию комплексов типа [М(ен)3] Х3X, имеетместо в случае Сr (III) комплексов, в которыхX=Cl, Br, I илиNCS, в случае же производныхСо (III) эта реакция возможна тол ько приX=Сl. В других сл учаях окислительно-восста новительные реакции мешают образ ованию стабильных пр омежуточных соединений. Рассчита ны кинетические параметры дегидрата ции 19 соединений.Обнаружена справедл ивость закона линейн ой кинетической компен сации. Обсуждается зависимость парамет ров кинетической ком пенсации от характера термическ ого процесса.

Thermal decomposition kinetics of diethyl dithiocarbamate complexes of copper(ii) and nickel(ii)

Abstract: Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL2 and NiL2 (L−=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL2, DTG 250–350°, DTA 300–320° and for NiL2, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

Thermal decomposition of cellulose

Abstract: Cellulose has been pyrolysed in nitrogen at two heating rates, and the rates of formation of total gases, and the oxides of carbon, have been measured. The quantities of products formed, and their first order kinetic parameters, are strongly dependent on the heating rate.

The Thermal Decomposition Reactions of Bivalent Metal Succinates in the Solid State

Abstract: The thermal decomposition reactions of MC4H4O4 (M : Mg(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II)) in nitrogen or helium were investigated by means of TG-DTA, X-ray diffraction measurements, gas chromatography, and combustion analysis for carbon. The decomposition residues of the Mg and Zn salts were composed of the corresponding metal oxides and some carbon, while those of the Co, Ni, Cu, and Pb salts were composed of the corresponding metals and some carbon. H2, O2, CO, CO2, H2O, CH4, C2H2, C2H4, HCOOCH3, HCOOC2H5, CH3COOC2H5, C2H5COOC2H5, and (CH2CO)2O were identified as the gaseous decomposition products; the compositions of the gaseous mixtures varied a great deal with the metals. Possible reaction mechanisms were discussed mainly on the basis of the decomposition products.