Microcalorimetric investigation of the recrystallization behaviour of polycrystalline copper deformed at room-temperature

The recrystallization of 5 N copper samples which had been deformed at roomtemperature by torsion to an average shear of by rolling to 65% r.c.s. was investigated by means of a commercial heatflow calorimeter.During recrystallization, which was also studied by hardness tests and optical microscopy, a stored energy release of the order of 0.145 cal/g was observed. Some problems inherent in the use of microsamples are discussed. By kinetic analysis, based on variation of the linear heating rate, a value of 21.9 kcal mole^–1 was determined for the apparent activation energy of the recrystallization process in torsion samples.

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Zusammenfassung Die Rekristallisation von 5 N Kupferproben, die bei Raumtemperatur durch Torsion bzw. durch Walzen (65%) verformt worden waren, wurde mit einem kommerziellen Wärmeströmungskalorimeter untersucht. Bei der Rekristallisation, die ebenfalls mit Härtemessungen und Gefügeuntersuchungen verfolgt wurde, wird eine Energiefreigabe von etwa 0.145 cal/g beobachtet. Einige bei der Verwendung von Microproben auftretende Probleme werden diskutiert. Eine Analyse der Kinetik, die auf der Variation der linearen Aufheizgeschwindigkeit basiert, ergab für die scheinbare Aktivierungsenergie des Rekristallisationprozesses in Torsionsproben einen Wert von 21.9 Kcal Mol^–1.

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Résumé On a étudié à l'aide d'un calorimètre à flux de chaleur commercial la recristallisation d'échantillons de cuivre 5 N, préalablement déformés à température ambiante par torsion ou par laminage (65%).Lors de la recristallisation, également suivie par mesures de dureté et examens de structure, on observe un dégagement d'énergie d'environ 0,145 cal/g. Les problèmes qui surgissent lors de l'utilisation de prélèvements micro sont discutés. L'énergie d'activation apparente du processus de recristallisation après l'écrouissage par torsion s'élève à 21.9 kcal mol^–1.

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5H , , , 65% . . . , , 0.145 /. , . , , , 21.9 ^–1.

     

Kinetics of the geometric isomerization of aqueous cis-diamminedichloroplatinum(II)

The rate of the isomerization of cis-diamminedichloroplatinum(II) to the trans form has been determined in aqueous KCl solutions from 65°C to 100°C. At 37°C the half-life is 1.8 years. Pt, AgCl, Si, SiO₂, and graphite did not catalyse the isomerization while other chemical reactions occurred with Ag and Ketjenblack carbon.

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-(II) - KCl 65°C 100°C. 37°C 1,8 . Pt, AgCl, Si, SiO₂ , Ag Ketjenblack.

     

Reactivity of alkyl and polychloroalkyl radicals toward 1-hexene

The kinetics of CCl₃ radical addition to 1-hexene in CCl₃Br and CCl₄ media has been studied. The rate constant of CCl₃ addition to the double bond is shown to be independent of the solvent. The ratios between the rate constants of transfer and allyl chain termination for the alkyl and polychloroalkyl radicals have been estimated by competition methods. Activation parameters for the calculated rate constants are given.

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CCl₃- 1- CCCl₃Br CCl₄. , . . .

     

Hydrogen adsorption on chromia-supported iridium catalyst

Effect of thermal pretreatment of chromia-supported iridium catalyst on hydrogen adsorption was studied. It was found that the hydrogen uptake by Ir/Cr₂O₃ was highly dependent on the reduction temperature. The catalyst proved to be resistant to sintering in oxygen atmosphere at temperatures up to 700 °C and it showed symptoms of redispersion even at 650 °C.

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. Ir/Cr₂O₃ . 700°C, , 650°C .

     

Is the ion-linear quadrupole capture rate constant anisotropic with respect to the sign of the product of the charge on the ion and the quadrupole moment of the molecule?

The sign of the charge-quadrupole moment product is shown to affect the rate of ion-linear quadrupole capture.

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- .

     

Effect of orbital-rotational coupling on the rate of ion-dipole capture at extremely low temperatures

The rate of the ion-dipole capture at very low temperatures or energies has been examined using the Statistical Adiabatic Channel model.

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- .

     

Violation of steady state process in CO hydrogenation to alcohols

Studies of the effect of iron supported on the surface of a K₂CO₃-doped zinc-chromium catalyst or entrapped from synthesis gas, have revealed violation of the steady state process in alcohol synthesis. Periodic oscillations in temperature and concentrations of reactants and reaction products are observed.

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, K₂CO₃ - -, , , , .

     

Hydrogenation of toluene over Pt and Pt?Cu alloys in NaY

The hydrogenation of toluene is performed over small Pt and Pt–Cu particles in a NaY zeolite. For toluene hydrogenation the T.O.N. of Pt and Pt alloyed with Cu are very different at room temperature but at high temperature (530 K) they are of the same order of magnitude.

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Pt Pt–Cu NaY. ( ) Pt Pt, , , , (530 K) .

     

Calculation of the energy spectrum of surface oxygen on CuO by the interacting bonds method

Using the interacting bonds model a calculation has been made for the energy spectrum of oxygen on the CuO surface. Dissociative adsorption of oxygen can be realized in one and two-center forms with 9.2 and 60.4 kcal/mol, respectively. Intermediate values of the adsorption heats are attributed to oxygen adsorption on induced and biographic defects. The theoretically calculated energy spectrum of adsorbed oxygen is in reasonable agreement with that obtained experimentally from the dependence of isosteric heats of oxygen adsorption on the surface coverage.

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CuO. - 9,2 60,4 / . . .

     

Kinetics of the acid catalyzed hydrolysis of hydroxamic acids

The acid catalyzed hydrolysis of some alkylhydroxamic acids has been studied spectrophotometrically in perchloric, hydrochloric and sulfuric acids. Plots of the first order rate constant, k_obs against H⁺ show maxima, which are caused by protonation of the substrate. The mechanism of hydrolysis is found to be similar to that of amides. The variation of reaction rate with acid concentration can be described by a two-parameter equation.

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, , , . k_obs [H⁺] , . . .

     

Investigation of catalytic purification of gases from aromatic hydrocarbons

1,1- (AH) ([AH]=6,9 /, 50°C). AH W_i/W_{O 3}=0,40±0,16.

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The kinetics and oxidation products of 1,1-diethoxyethane (AH) ozonolysis have been investigated at [AH]=6.9 mol/l and 50 °C. The initiation efficiency of radical oxidation by ozone is W_i/W_{O 3}=0.40±0.16.

     

Mechanism of catalysis and factors responsible for oxide catalyst activity in deep oxidation reactions

A general scheme for the deep oxidation mechanism on oxide catalysts including stepwise and concerted mechanisms as well as their mutual transformations is suggested. The principal factor responsible for the activity in the concerted mechanism region is the rate of oxygen binding. For the stepwise mechanism the main factor is the rate of catalyst interaction with oxidizable reactant.

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, . , . .

     

A flow-mixed reactor

A glass flow mixed reactor is described. In this reactor a stationary catalyst in the form of a plate 72 mm in diameter and 2 mm thick is placed on the bottom of the reactor. Determination of mass transfer at the upper surface of the plate showed that the whole surface of the catalyst was equally accessible to reacting gas mixtures.

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. 72 2 . , .

     

Catalytic activity of high-silicon TsVK and Y type zeolites

Conversion of paraffins on TsVK and Y zeolites follow a similar mechanism yielding the same intermediates. Low selectivity of Y zeolites with respect to aromatic hydrocarbons is attributed to the strong adsorption of these hydrocarbons on zeolites. It is assumed that the centers of strong adsorption are Al³⁺ ions in cationic positions in zeolite.

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, . . , Al³⁺ .

     

Catalysis of thiophene hydrogenolysis by bimetallic sulfide catalysts of different compositions

The activity of sulfide catalysts M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ and (Ni,M_II)/SiO₂ (M_I is a first row transition metal, and M_II=Nb, Mo, W or Re) in the thiophene hydrogenolysis reaction has been studied. Activities of mono- and bimetallic catalysts are found to change in the same manner depending upon the nature of M_I. The formation of a sulfide bimetallic species (SBMS) is suggested.

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M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ (Ni, M_II)/SiO₂, M_I — , M_II–Nb, Mo, W, Re. - M_I. .

     

Interaction of hydrogen sulfide with molybdophosphoric heteropolyacid

The effect of hydrogen sulfide on P–12Mo heteropolyacid has been studied using ESR, IR spectroscopic and thermal analysis methods. It has been established that hydrogen sulfide can be chemisorbed like water and no entering of sulfur into the anion structure takes place.

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, P–12Mo . , . .

     

Structure and reactivity of vanadium(V) complexes formed in the reaction between vanadyl acetylacetonate and alkyl hydroperoxides. To the mechanism of selective epoxidation of olefins

Vanadium(V) complexes formed in the reaction between vanadyl acetylacetonate and alkylhydroperoxides are characterized according to their¹H and⁵¹V NMR spectra and the reactivity of these complexes towards cyclohexene is studied.

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¹H ⁵¹V , .

     

Unusual selectivity in photooxygenation of alkanes by air in CH3CN solutions catalyzed by CrCl3?C6H5CH2N(C2H5)3Cl

A new system CrCl₃–C₆H₅CH₂N(C₂H₅)₃Cl–CH₃CN for photooxygenation of alkanes is suggested. Unlike metal chlorides and oxocomplexes, it oxidizes alkanes to produce ketones and small amounts of alcohol. Adding of benzene, methylene chloride or ethanol to the cyclohexane solution rises the oxygenation rate and changes the ketone/alcohol ratio. With small amounts of hydroquinone the formation rate of cyclohexanone (but not of cyclohexanol) sharply decreases. Kinetic isotope effect in the oxidation of C₆H₁₂ and C₆D₁₂ is 1 for cyclohexanol and 2.9 for cyclohexanone. Cyclohexanol formation is assumed to follow a mechanism that does not involve free radicals. Free radicals can participate in the route toward ketone.

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CrCl₃–C₆H₅CH₂N(C₂H₅)₃Cl–CH₃CN . , . , /. ( ) . C₆H₁₂ C₆D₁₂ 1 2,9 . , , . , .

     

Correlation between acid strength (Ho) and ammonia desorption temperature for aluminas and silica-aluminas

Correlation between the temperature at which a base is desorbed and the acid strength (H_o) of the sites set free by it, was looked for. Ammonia was employed as base. A linear correlation of the type H_o=+/T (K) is valid with and constants, dependent on the adsorbate and the adsorbent.

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(H_o) , . H_o=+/T (K), .

     

Comparative testing of the flammability of upholstery textiles

Flash ignition temperatures of upholstery textiles were measured with a modified derivatograph, and the TG, DTG, DTA and T curves were also recorded. The results obtained with the newly-developed system were compared with those of the ASTM D 1929 test procedure and with the simultaneously recorded thermal analysis curves.

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Zusammenfassung Der Flammpunkt von Upholstery-Textilien wurde mittels eines modifizierten Derivatographen gemessen. TG-, DTG-, DTA- und T-Kurven wurden registriert. Die mit diesem neuentwickelten System erhaltenen Ergebnisse wurden mit den nach dem ASTM D 1929 Testverfahren erhaltenen und mit den simultan registrierten thermoanalytischen Kurven verglichen.

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, -, -, - -. , ASTM 1929 .

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Paper presented at the World Conference on Thermal Analysis, Madeira (Portugal), 1986.