Showing papers on "Thermal decomposition published in 1974"

Ruthenium dioxide: a new electrode material. I. Behaviour in acid solutions of inert electrolytes

Abstract: The electrochemical behaviour of RuO2 film electrodes, prepared by the thermal decomposition of Ru Cl3 on metallic supports has been investigated in solutions of inert electrolytes. Steady-state pot entiostatici/E curves, cyclic voltammetry and charging curves are presented. The procedure for the preparation of electrodes is described.

An investigation of phase stability in the Y2O3-Al2O3 system

Abstract: The stability of the three known phases in the Y2O3-Al2O3 pseudo-binary system has been investigated. YAlO3 (YAP) and Y4Al2O9 (YAM) decompose at elevated temperatures, the products of the reaction being the third compound Y3Al5O12 (YAG) and an unknown phase (designated X). The decomposition is most evident in powders but can also be initiated on the surface of bulk single crystals. X-ray diffraction studies have been performed in an attempt to identify the structure and composition of the unknown phase. The thermal decomposition has been found to be surface controlled and an optical and scanning electron microscope study of the associated morphological changes in YAlO3 indicates that the reaction involves localized surface melting, probably with the loss of oxygen which effectively moves the composition off the binary join.

Copper(I) alkoxides. Synthesis, reactions, and thermal decompositions

Abstract: Alkoxides and phenoxides of copper(I) can be prepared by the heterogencous reaction between alcohols and phenols and methylcopper(I). These organocopper(I) compounds are useful reagents for the formation of ethers by displacement of hai ide from organic hal ides. The reaction of copper(l) alkoxidcs with aryl hal ides yields alkyl aryl ethers under part icularly mild iondit ions. Thermal decomposit ion of primary alkorycopper(l) reagcnts generates intermediate alkoxy radicals. Thermal clecomposit ion of secondary alkoxycopper(l) reagents apparently can take place either by a free-radical mechanism or by a mechanism tentat ively suggested to involve copper(I)-hydride as an intermediate. The structural factors determining which mechanism wil l predominate for a given compound have not been established' tTth. utit i ty of alkyland arylcopper(l) reagents in I organic synthesis is based on their h igh nucleophi l ic i ty toward carbon, and on their abi l i ty to take part in electron-transfer reactions.2-a They also show low basicity toward protons, an afff inity for carboncarbon double bonds, and an abi l i ty to coordinate wi th soft Lewis bases. Since the mechanisms by which copper(I) influences the reactivity of carbanions are not clearly understood, it is diff icult to predict the behavior of new types of organocopper( I ) compounds. Nevertheless, there is obvious reason to hope that organic derivatives of copper(I) other than those belonging to the wel l -explored class of compounds containing carbon-copper bonds might also show useful (1) Supported by the Nat ional Science Foundat ior l , Grants GP28586X ancl GP-14247, ancl by the Internat ional coppcr Rcsearch Associat ion. (2) J. F. Normant, S) 'nthesis,2,63 (1972); G' H. Posner, Org' React ' , 19, | (1972), (3) G. Br ihr ancl P. Burba in \"Methoden der organischen chemie\" (Houben-Weyl) , Vol . XI I I /1, E ' Mi , i l ler , Ed. , Georg Thicme Vcr lag, Stut tgart , 1970, p 731 f f . (4) O. A. Chal tyk ian, \"Copper-Catalyt ic React ions,\" A. E. Stubbs, t rans. , Consul tants Bureau, New York, N' Y. , 1966; P. F. Fanta, Chem. Rec, ,64,613 (1964); R. G. R. Bacon and H. A. O. Hi l l ' Quart ' Rec. , Chem. Soc. , 19,95 (1965); J. Peisach, P. Aisen, and W. E' Blurnberg, Ed., \"The Biochemistry of Copper,\" Academic Press, New York, N . Y . . 1966 . react iv i ty. This paper descr ibes studies of one such class: a lkoxides of copper( l ) . These studies had three object i ies: synthesis and character izat ion of a lkoxides und phenox ides o f copper ( l ) ; de termina t ion o f the behar l ior of thesc substances in react ions whose usefulness with alkylcopper reagents has already been establ ished: and examinat ion of the mechanisms of their thermal decomposi t ion. Copper( l ) a lkoxides and phenoxides have been impl icated previously as intermediates in a var iety of copper-catalyzed react ions,a '5 and poor ly character ized examples of these substances have been prepared'6 A useful synthesis of copper([) tert-butoxideT is not appl icable to the preparat ion of the thermal ly unstable copper( I ) pr imary and secondary alkoxides that were of ^central interest in our work. The preparat ion of copper( I ) phenoxide by a procedure analogous to that descr ibed here has been reported.s Copper( I ) a lkoxides (5) J. K. I (ochi , Proc. I t t t . Congr. Pure Appl ' Chem', 23rd,4 ' 377 (1971), and referenccs citcd therein, (6 ) b . E . H . Bawr r and F . J . Wh i tbv , J . Chem.9oc . ,3926 (1960) ; G ' Costa. A. Camus, and N. Marsich, J. Inorg ' l ' ' luc l ' Chem',27' 281 ( I e6s ) . (7) T. Saegusa, T. Tsucla, and T. Hashirnoto, J ' Amer ' Chem' Soc\" 94 ,658 (1972) . iSl f. I(awaki and H. Hashimoto, Bull. Chem. Soc' Jap', 45, 1499 (r972). Whitesides, et al, I St'nthesis ttf Cttpper(l) Alkoxides

The thermal decomposition of calcium, sodium, silver and copper(II) acetates

Abstract: The thermal decomposition of the acetates of calcium, sodium, silver and copper(II) have been investigated using thermogravimetry and differential thermal analysis, together with analysis of the gaseous products formed during the decomposition process. The results indicate that the major organic product formed is either acetone or acetic acid, depending on whether the final solid product is the oxide or the metal.

Kinetic analysis of thermogravimetric data: VII. Thermal decomposition of calcium carbonate

Abstract: Fifteen thermogravimetric curves of the thermal decomposition of CaCO3 reported in the literature have been analysed and kinetic parameters have been derived by means of Coats and Redfern's method. The activation energy varies between 26 and 377 kcal/mole, and the pre-exponential factors between 102 and 1069, as functions of the working conditions. The kinetic compensation effect has been observed, and the results are well described by the following empirical compensation law: logZ=0.195E− 1.86.RésuméOn a calculé les paramètres cinétiques de la décomposition thermique de CaCO3 en suivant la méthode de Coats et Redfern et en utilisant 15 courbes thermogravimétriques publiées dans la littérature. L'énergie d'activation varie entre 26 et 377 kcal/mol, les fac teurs préexponentiels entre 102 et 1069, suivant les conditions opératoires. On a observé l'effet de compensation cinétique et les résultats peuvent être décrits par la loi empirique suivante: logZ=0.195E − 1.86.ZusammenfassungFünfzehn, in der Literatur veröffentlichte thermogravimetrische Kurven der thermischen Zersetzung des CaCO3 wurden analysiert und kinetische Parameter unter Anwendung der Methode von Coats und Redfern abgeleitet. Die Aktivierungsenergie schwankt zwischen 26 und 377 kcal/Mol, die prä-exponentiellen Faktoren zwischen 102 und 1069, je nach den Arbeitsbedingungen. Der kinetische Kompensationseffekt wurde beobachtet und die Ergebnisse lassen sich mit dem folgenden empirischen Kompensationsgesetz gut beschreiben: logZ=0.195E− 1.86.РезюмеПроанализированы 15 те рмогравиметрически х кривых термораспада СаСО3, опубликованных в литературе, и по мето ду Котса и Редферна рассчитан ы кинетические параметры в зависимо сти от условий экспер имента. Энергия активации ко леблется между 26 и 377 ккал/мол, преэ кспоненциальные фак торы —между 102 и 1069. Наблю дается эффект кинетической компенсации и резуль таты удовлетворительно о писываются следующим эмпиричес ким законом компенса ции: logZ=0,195E − 1,86.

On the thermal decomposition of GaN in vacuum

Abstract: The thermal decomposition of GaN was studied by means of a Mettler Thermoanalyzer while the gaseous products evolved were continuously pumped out. Some small loss of weight of GaN was observable already in the temperature range of 710 to 980°C but a definitive loss started only above 980°C. The gaseous decomposition products were analyzed also by means of a mass-spectrometer, Varian, coupled directly to a vacuum furnace. Only nitrogen was found. The temperature dependence of the decomposition was determined using the equilibrium pressure data of the dynamic system. Die thermische Zersetzung des GaN wurde unter fortlaufendem Abpumpen der Spaltgase mit einem Mettler Thermoanalysator untersucht. Eine geringe Absenkung des Gewichts des GaN konnte schon im Temperaturbereich von 710 bis 980°C beobachtet werden, aber ein ausgepragter Gewichtsverlust begann nur uber 980°C. Die gasformigen Zersetzungs-produkte wurden auch mit einem, dem Vakuumofen unmittelbar angeschlossenen Massen-spektrometer, Varian, untersucht. Die Temperaturabhangigkeit der Zersetzungwurde aus den Daten der Gleichgewichtsdrucke des dynamischen Systems berechnet.

Thermal Decomposition of Polyvinyl Chloride) and of Its Low-Molecular-Weight Model Compounds

Abstract: Polyvinyl chloride) (PVC) is undoubtedly among the most frequently used plastics; it is widely applied in many branches of the national economy, including industry and building [1] Its advantages are comparatively high chemical resistance, low production costs, and an almost universal possibility of application as pastes, lattices, solutions, films, boards, various extruded or molded pieces, etc [2]

The Organic Chemistry of Copper

Abstract: Publisher Summary This chapter discusses the organic chemistry of copper. Organocopper compounds have been obtained by many methods; the one commonly employed is the metathetical reaction between an organometallic reagent, wherein the metal is higher than copper in the electromotive series, and a copper salt. A general method for the preparation of organocopper compounds of the type RCu is the reaction of a Grignard or lithium reagent with an excess of a copper salt. Organocopper compounds, such as methyl–, phenyl–, tolyl–, and ethynylcopper are easily isolated by the virtue of their insolubility in the media employed in their preparations. The structures of some copper compounds have been determined either by X–ray crystallography or by a combination of nuclear magnetic resonance (NMR) and mass spectroscopic data and the degree of association. Ultraviolet spectral data have been reported for a few organocopper compounds. Organocopper–isocyanide complexes are assumed to be intermediates in certain organic syntheses. Perfluoroalkylcopper and perfluoroarylcopper compounds are noticeably more thermally stable than the corresponding alkyl and aryl compounds. The thermal decomposition of aryl– and vinylcopper compounds is an alternative method of obtaining dimeric products from organocopper compounds. Organocopper compounds are useful reagents for coupling reactions with organic halides. A noticeable feature of the majority of reactions of diorganocuprates with alkyl halides is that the molar ratios of up to 5: 1, respectively, are employed for most effective coupling.

Studies on the formation of ?-Fe2O3 (maghemite) by thermal decomposition of ferrous oxalate dihydrate

Abstract: The thermal decomposition of ferrous oxalate dihydrate FeC2O4.2H2O, has been investigated using thermogravimetric (TG), differential thermogravimetric (DTG), differential thermal analysis (DTA), X-ray diffraction and infra-red spectroscopic techniques. The DTA data obtained in air consist of an endothermic dehydration peak at ∼ 190‡ C and two exothermic peaks at ∼ 245 and ∼ 360‡ C. The first exotherm corresponds to the primary oxidative decomposition while the second one seems to be due to a structural transformation from a disordered or non-crystalline to a crystalline state ofα-Fe2O3. Similar experiments carried out using a nitrogen atmosphere show an endothermic peak ∼ 190‡ C followed immediately by an exothermic peak at 240‡ C. The final product of this decomposition has been identified as Fe3O4. The oxalate dihydrate containing traces of moisture decomposes in air under the ambient of its own gaseous products at ∼ 300‡ C to giveγ-Fe2O3. This compound has been characterized by X-ray diffraction and magnetic hysteresis measurements.

Catalytic production of isocyanates from esters of carbamic acids

Abstract: Method for the production of isocyanates from esters of carbamic acids (urethanes) by decomposing the ester in the presence of a heavy metal or inorganic or organic compound of the heavy metal or mixtures or combinations thereof at elevated temperatures while said ester is dissolved in a suitable inert solvent to produce the isocyanate and alcohol, the heavy metal catalyst may be as finely divided metal or mixture of metals and the heavy metal compound catalyst may be further characterized by being soluble under reaction conditions. This method gives increased decomposition rates as compared with thermal decomposition.

On the eutectoid decomposition of CaCu5-type rare earth-cobalt phases

Abstract: The decomposition of CaCu5-type rare earth-cobalt compounds has been studied at various stages. It is shown that the occurrence of one of the phases, after decomposition in the form of closely-spaced parallel lamellae, corresponds to an intermediate stage of the decomposition process in which the initial precipitates have not yet coalesced into larger regions. The influence of various impurities on the metastable character of the RCo5 compounds has been investigated. It is shown that impurities can shift the decomposition temperature over a range of several hundred degrees Celsius.

Evaluation of kinetic parameters of thermal decomposition of native collagen by thermogravimetric analysis

Abstract: The kinetic parameters associated with the thermal decomposition of native collagen have been obtained by thermogravimetric techniques. In order to achieve this a thermogravimetric analysis was carried out in the temperature range of 25°C to about 1000°C. In this temperature range, it had been found that the differential primary weight loss curve had yielded three distinct peaks for the tendon collagen. The thermal decomposition corresponding to each peak was analyzed to retrieve its kinetic parameters. The peak temperature associated with the first peak decreased as the water content in a sample increased, while that of the second peak was independent of its hydration condition. It is believed that the first and the second peaks are, respectively, results of: (1) dissociation of water from collagen, and (2) of breaking of the collagen molecule itself. The third peak has not been easily identified so far. The activation energy and the order of water decomposition are obtained by various known methods. The results obtained by these different approaches agree reasonably well. The kinetic parameters of second and third peak are also obtained and reported here.

Very low-pressure pyrolysis (VLPP) of t-butylmethyl ether

Abstract: The thermal decomposition of t-butylmethyl ether has been studied using the VLPP technique. The recommended Arrhenius parameters for the molecular elimination, reaction (1), are A(800°K) = 101 3, 9 sec−1 and Ea (800°K) = 59.0 ± 1.0 kcal/mole. No radical reactions occur under the conditions used. These parameters are in good agreement with earlier experimental work and with theoretical estimates of both A and E.