Organic-inorganic composites of poly(methyl methacrylate) with alkoxysilane hydrolyzates form transparent films. Their thermal and oxidative thermal degradation were studied by differential scanning calorimetry and thermogravimetric analysis. 相似文献
A new class of Sc, Eu, and Tb complexes with N,O-chelate ligands was synthesized for the first time. The mass spectra, thermogravimetric analysis, differential scanning calorimetry data, as well as the data on the saturated vapor pressure of the compounds were obtained. The main thermochemical parameters of the compounds were calculated. 相似文献
The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in
BaPb1 − xSbxO3 superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of 17O are measured systematically, and the contributions from 17O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin
density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase
of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in
compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of 17O-207Pb and 17O-121Sb are measured in the metal phase of BaPb1 − xSbxO3 oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin 17O-207Pb interaction are determined as functions of the local Knight shift 207Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms)
and analysis of evolution of the NMR spectra of 17O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous
state of the electron system in the metal phase of BaPb1 − xSbxO3 oxides. 相似文献
The heat capacity of di-(2-pyridyl)amine-bis-(4-methoxy-3,6-di-tert-butyl-o-benzosemiquinone)cobalt in the temperature range from 7 to 370 K was investigated by means of precise adiabatic vacuum calorimetry. It was established that the phase transition associated with the redox-isomeric transformation of the semiquinone-catecholate form of the complex into the bis-semiquinone form is observed above 260 K; this transition is not completed due to thermal destruction that begins at 367 K. The magnetic moment values in the temperature range from 5 to 350 K and the EPR spectra in the temperature range from 130 to 290 K, which confirm the nature of the phase transition, were obtained for the investigated complex. The standard thermodynamic functions CppO(T), H○(T)-H○(0), S○(T), and G○(T)-H○(0), were calculated from the data on heat capacity in the temperature range from T → 0 to 260 K. Analysis of the low temperature heat capacity on the basis of Debye’s theory of the heat capacity of solids and the multifractional model testifies to the chain-layered structural topology of the investigated complex. 相似文献
The synthesis and the studies of properties of diphenyl[dialkyl(alkyl)carbamoylmethyl]phosphine oxides by differential scanning
calorimetry, mass spectrometry and Knudsen effusion method were performed. The thermodynamic parameters of melting and vaporization
were calculated. 相似文献
The dependences of the relaxation rate and the absorption coefficient of ultrasound in GaAs crystals on the direction of the wave vector of quasi-transverse phonons for the Landau-Rumer mechanism are analyzed in the framework of the anisotropic-continuum model. The calculations are performed with two sets of second-order and third-order elastic moduli experimentally measured by different authors. It is demonstrated that the angular dependences of the relaxation rates of quasi-transverse phonons and the ultrasonic absorption coefficients calculated from these data differ qualitatively. The correctness of the determination of the third-order elastic moduli available in the literature can be checked by measuring the ultrasonic absorption coefficients for GaAs crystals. 相似文献
Active iron-containing nanosized components have been formed on the lignin surface. The metal was deposited on the lignin from an ethanol solution of Fe(acac)3 and from a colloid solution of iron metal particles obtained beforehand by metal vapor synthesis. These active components are able to absorb microwave radiation and are suitable for microwave-assisted high-rate dehydrogenation and dry reforming of lignin without addition of a carbon adsorbent, as a supplementary radiation absorbing material, to the feedstock. The dependence of the solid lignin heating dynamics on the concentration of supported iron particles was investigated. The threshold Fe concentration equal to 0.5 wt.%, providing the highest rate of sample heating up to the reforming and plasma generation temperature was identified. The microstructure and magnetic properties of iron-containing nanoparticles supported on lignin were studied before and after the reforming. The Fe3O4 nanoparticles and also core-shell Fe3O4@γ-Fe-С nanostructures are formed during the reforming of lignin samples. The catalytic performance of iron-based nanoparticles toward the lignin conversion is manifested as increasing selectivity to hydrogen and syngas, which reaches 94% at the Fe concentration of 2 wt.%. It was found that with microwave irradiation under argon, hydrogen predominates in the gas. In the СО2 atmosphere, dry reforming takes place to give syngas with the СО/Н2 ratio of ~?0.9. In both cases, the degree of hydrogen recovery from lignin reaches 90–94%.
Graphical abstract The microwave-supported deposition of iron on the lignin surface gives active well defined nanoparticles Fe3O4 and also core-shell Fe3O4@γ-Fe-С nanostructures. These nanocomponents provide for high-rate microwave-assisted dehydrogenation and dry reforming of lignin.
We present results of the combined study of the magnetic properties of Li2RuO3 by means of nuclear magnetic resonance (NMR) spectroscopy and theoretical dynamical mean-field theory (LDA + DMFT) calculations. The NMR data clearly show the onset of a thermal activation process in the high temperature region, T > 560K, which is tentatively ascribed to the formation of the valence bond liquid. The LDA + DMFT calculations demonstrate that the magnetic response at these temperatures is mostly due to the xz/yz orbitals, while the xy orbitals of Ru still form molecular orbitals. Thus, Ru ions are in the orbital-selective state in the high temperature phase of Li2RuO3. 相似文献
Comprehensive NMR investigation of low-frequency spin dynamics of LiCu2O2 (LCO) and NaCu2O2 (NCO) low-dimensional helical magnets in the paramagnetic state has been carried out for the first time. Temperature dependences of the spin–lattice relaxation rate and anisotropy on various LCO/NCO nuclei have been determined at various orientations of single crystals in an external magnetic field. The spatial asymmetry of spin fluctuations in LCO multiferroic has been discovered. The quantitative analysis of the anisotropy of spin–lattice relaxation in LCO/NCO has allowed estimating the contributions of individual neighboring Cu2+ ions to the transferred hyperfine field on Li+(Na+) ions. 相似文献