Thermal conductivity of Pb-Mg-Zr alloys and the thermal resistance of the interface between alloys and EP-823 steel in the temperature range of 300–900°C

A technique for measuring the thermal resistance of the liquid metal–structural steel interface is proposed. The results ofmeasurements of the thermal resistance of the interface between Pb-Mg-Zr alloys and EP-823 steel and the thermal conductivity of Pb-Mg-Zr alloys in the temperature range of 350–900 °C are presented.     

Influence of grain boundary state on electrical resistivity of ultrafine grained aluminium

An ultrafine grained (UFG) structure has been obtained in commercial purity Al by high-pressure torsion (HPT). Changes in microhardness and electrical resistivity of the UFG material after annealing at various temperatures within a range of 363–673 K have been investigated in correlation with the microstructure evolution. It has been shown that annealing at 363 K leads to substantial decrease in the electrical resistivity while keeping high microhardness level and approximately the same average grain size. The contributions from the various microstructural units (vacancies, dislocations, grain boundaries (GBs)) to the electrical resistivity were analysed. It was shown for the first time that a non-equilibrium state associated with strain-distorted grain boundary (GB) structure strongly affects electrical resistivity of UFG Al. The resistivity of non-equilibrium GBs in UFG structure formed by HPT was evaluated to be at least 50% higher than the resistivity of the thermally equilibrium GBs in a coarse-grained structure.     

Photopolymerization kinetics of a thiol–enol composition determined via recording/playback of a transmission holographic diffraction grating

The kinetics of thiol–enol photopolymerization of a hybrid composition based on a tetraacrylate monomer and a thiol-siloxane oligomer was studied with the use of a holographic recording of elementary transmission phase gratings. The degrees of conversion of double bonds in the tetraacrylate monomer after the polymerization in air and in an inert atmosphere of SF₆ were measured via IR spectroscopy. It is shown that the use of the thiol-siloxane oligomer efficiently suppresses oxygen inhibition of the photopolymerization. When the photoinitiator concentration is increased to more than 10^–2 mol/L, the photopolymerization rate levels off. An increase in the thiol-siloxane oligomer concentration leads to an extremal dependence of the photopolymerization rate on the oligomer concentration; the maximum rate is reached at an oligomer concentration of about 0.07 mol/L. The kinetic scheme of photopolymerization in the hybrid photopolymer composition was analyzed, and an analytical expression for the photopolymerization rate was obtained. The correlation between the kinetic constants of the thiol–enol photopolymerization was evaluated on the basis of the obtained parameters of the kinetic model.     

Effect of excess molybdenum trioxide on the activity and selectivity of some molybdates in methanol oxidation

Addition of a 10 mol% excess of molybdenum trioxide to normal molybdates of Na, Ca, Sr, Ni, Ba, Pb, Cr, Cd, Bi, Co and Fe significantly increases the activity and selectivity in the oxidation of methanol to formaldehyde. Upon further increase of the amount of MoO₃ the activity and selectivity vary but slightly. Probably, this effect is due to the formation of solid solutions containing molybdenum atoms in various states.

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Введение избыточной трехокиси молибдена в нормальные молибдаты Na, Ca, Sr, Ni, Ba, Pb, Cr, Ca, Bi, Co и Fe в количестве 10% мол. приводит к существенному увеличению активности и избирательности в окислении метанола до формальдегида. При дальнейшем увеличении количества вводимой трехокиси молибдена активность и избирательность изменяются незначительно. Предположено, что этот эффект связан с образованием твердых растворов, в которых имеются атомы молибдена в разных состояниях.

     

The heat effects of dissociation of maleic and fumaric acids

The heat effects of dissociation of maleic and fumaric acids at 298.15 K and several ionic strength values were determined calorimetrically in the presence of NaNO₃. The thermodynamic characteristics of dissociation at fixed ionic strengths and under standard conditions were calculated.     

Use of diamond stock in chromium plating

Cathodic deposition of a chromium coating from the standard electrolyte in the presence of a diamond stock was analyzed. The microhardness and wear resistance of chromium diamond coatings and the effect of the diamond stock on the electrical conductivity and throwing power of the electrolyte were studied.     

Iodine and cymantrenyl regioselective exchange in the η5-IC5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 complex under cross-coupling conditions

The reaction of ⁵-IC₅H₄(CO)₂Fe-¹,⁵-C₅H₄Mn(CO)₃ with Me₃SiCCSiMe₃ (2 : 1) in the presence of Pd(MeCN)₂Cl₂ afforded the I(CO)₂Fe(C₅H₄—C₅H₄)Mn(CO)₃ complex generated through migrations of the I atom from the Cp ring to the Fe atom and of the C₅H₄Mn(CO)₃ group from the Fe atom to the Cp ring.     

Thermal stability of urea complexes of magnesium nitrate and magnesium monophosphate

Urea complexes of magnesium nitrate and magnesium monophosphate were synthesized and investigated by thermal analysis, X-ray phase analysis and IR spectroscopy. It was found that the thermal stability of the complexes increases with the number of organic ligands in the complex. The mass losses corresponding to the stages of thermal decomposition of the compounds were calculated via the thermogravimetric curves. The mode of coordination between urea and Mgⁿ was investigated by IR spectroscopy.

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Zusammenfassung Harnstoffkomplexe von Magnesiumnitrat und Magnesiummohophosphat wurden synthetisiert und mittels thermischer Analyse, Röntgenphasenanalyse und IR-Spektroskopie untersucht. Die thermische Stabilität der Komplexe nimmt mit der Zahl der organischen Liganden im Komplex zu. Die thermischen Zersetzungsschritten der Verbindungen entsprechenden Massenverluste wurden aus den thermogravimetrischen Kurven ermittelt. IR-spektroskopisch wurde die Art der Koordination zwischen Harnstoff und Mg(II) untersucht.

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, , . , . , . Mg ^II.

     

Quantum polarization and dielectric losses at low temperatures

We propose a mechanism for the quantum polarization of solid dielectrics, and use it to create and study the kinetic equation taking into account the tunneling of relaxation oscillators. The frequency dependences of both and tan are determined theoretically and compared with experiment. The density of thermally stimulated currents in the dielectrics are calculated. We find that one must take into account tunneling transitions of relaxation oscillators in order to explain the low-temperature features in the dielectric spectra.Translated from Izvestiya Vysshikh Uchebnykh Zavenenii, Fizika, No. 2, pp. 6–9, February, 1984.