Interaction potentials and collision integrals for hydrogen and alkali metal atoms

Interaction potentials between hydrogen and alkali metal atoms have been calculated. Calculated values of collision integrals in the temperature range 700–1500°K are reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 6, pp. 999–1004, December, 1980.     

Electric conductivity of metal-dielectric-metal structures with dielectric layer formed by spherical metal oxide nanoparticles

The electrical properties of metal-dielectric-metal (MDM) structures with the dielectric layer representing a monolayer of spherical Al₂O₃ or ZrO₂ oxide nanoparticles have been studied. It is established that these heterogeneous structures exhibit electric conductivity according to the mechanism for which the differential resistance dU/dI is negative and reversibly approaches zero with increasing current I. The electric conductivity strongly depends on the polarity of the applied voltage U, provided that electrodes are made of basically different metals or the same metal with different surface conditions. The mechanism of the electric conductivity in the given MDM structure depends on the diameter of nanoparticles in the dielectric layer.     

Viscosity and thermal conductivity of alkali metal vapors at temperatures up to 2000 K

New experimental data were obtained on transport coefficients of alkali metals in gaseous phase at high temperatures and within the pressure range from about 10 to about 100 kPa: lithium—thermal conductivity, T= 1400–1800 K, and viscosity, T=1600–2000 K; sodium-viscosity, T= 1100–1500 K; and cesiumviscosity, T=900–1250 K. Viscosity of the alkali metal vapors has been measured using a stationary-technique viscometer with an annular gap. Thermal conductivity was measured by the method of the nonstationary monotonous heating. Experimental data were used as a basis for computing effective atomatom and atom-molecule collision cross section, the values obtained from data on viscosity being in good agreement with those derived from thermal conductivity data. In the case of lithium, the atom-atom cross sections yielded by experiments are fairly consistent with the results of calculations with exact formulae of kinetic theory on the basis of quantum-mechanical potential curves for atom-atom interactions. This has enabled the authors to compile consistent tables of viscosities and thermal conductivities for lithium in a gaseous phase within the temperature range from 800 to 2500 K and pressures from 0.5 to 800 kPa, including the saturation curve.     

Enhanced conductivity of aluminum doped ZnO films by hydrogen plasma treatment

Aluminum doped zinc oxide (AZO) thin films prepared by radio-frequency (RF) magnetron sputtering at various RF power were treated by hydrogen plasma to enhance the characteristics for transparent electrode applications. The hydrogen plasma treatment was carried out at 300 °C in a plasma enhanced chemical vapor deposition system. X-ray diffraction analysis shows that all AZO films have a (002) preferred orientation and film crystallinity seems no significant change after plasma treatment. The plasma treatment not only significantly decreases film resistivity but enhances electrical stability as aging in air ambient. The improved electrical properties are due to desorption of weakly bonded oxygen species, formation of Zn-H type species and passivation of deep-level defects during plasma treatment.     

Sensitivity of porous silicon-ferromagnetic metal composites to molecular hydrogen adsorption

The effect of molecular hydrogen adsorption on the current-voltage characteristics of structures based on porous silicon (por-Si) nanocomposites with nickel (por-Si-Ni) and cobalt (por-Si-Co) has been studied. The samples exhibit significant sensitivity to molecular hydrogen adsorption at a temperature of about 150°C. A model is proposed that explains the observed phenomena.     

Thermochemistry of alkali metal uranomolybdates

Compounds A ₂ ^I UMo₂O₁₀·mH₂O (A_I=Na, K, Rb, Cs) were synthesized and studied by reaction calorimetry. The standard enthalpies of formation and hydration of the compounds at 298 K were determined.     

Thermal conductivity of fluorides of alkali earth metals

A linear dependence is obtained between the thermal resistance and the temperatures for the monocrystalline fluorides CaF₂, SrF₂, BaF₂, and MgF₂. Anisotropy in MgF₂ has been discovered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 2, pp. 322–327, February, 1976.     

Adsorption of hydrogen,alkali metal,and halogen atoms on graphene: Adatom charge calculation

The adsorption of an atom with a single valence s electron (hydrogen, alkali metals) or with a single valence p-vacancy (halogens) on the surface of a graphene monolayer is considered and the adatom charge is calculated. Cases where the adatom-graphene σ bonds are formed with the participation of p, sp, sp ², and sp ³ states of carbon atoms are analyzed. It is established that the character of hybridization rather weakly influences the charge transfer. The character of adatom charge variation in the series Li → Cs and F → I is analyzed.     

Liquid-liquid extraction of alkali metal ions with photochromic crowned spirobenzopyrans

On the liquid-liquid extraction using 1,2-dichloroethane as an organic solvent, the crowned spirobenzopyrans exhibited textractability in the following order: Li+ > Na+ > K+ > or = tetramethylammonium ion (TMA+), Li+ > Na+ > K+ > TMA+, and Na+ > K+ > Li+ > TMA+ for spirobenzopyran derivatives bearing monoaza-12-crown-4, 1; monoaza-15-crown-5, 2; and monoaza-18-crown-6, 3; respectively, under dark conditions. The ion selectivity of 1 depends on the metal-ion complexing ability of monoaza-12-crown-4. Even 2, which carries a 15-crown-5 moiety, showed Li+ selectivity because of the much stronger interaction of Li+ with the phenolate ion of the merocyanine form of 2 than that of Na+. The Na+ selectivity of 3 is also attributed to the ionic interaction with the phenolate ion of the merocyanine form, since the ionic interaction prefers Na+ to K+ regardless of the higher affinity of the 18-crown-6 ring itself to the latter ion. The Li+ extraction into the organic phase with 1 was enhanced by UV irradiation (300-400 nm), while some depression in the extraction was found by visible irradiation (>500 nm). The effect of visible irradiation on the Li+ complexing ability of 1 was also examined with electrospray ionization mass spectrometry.     

Molten salt syntheses of alkali metal titanates

Submicrometer dispersions of rod-like alkali metal titanates were prepared by the flux method, from the reaction of TiOSO₄ or TiO₂ precursors in molten alkali metal nitrates, doped with carbonates or hydroxides. Mono-, di-, tetra-, and hexatitanates are formed as a function of the precursor nature and the melt composition. As a rule, in these syntheses poorly crystalline or amorphous solids are obtained, showing the structure of polytitanates on the nanoscopic level. Lamellar potassium hexatitanate can be exchanged by action of a diluted acid, leading to protonic form, free from the alkali metal but retaining initial morphology. Reactivity of TiOSO₄ and TiO₂ in molten alkali metal nitrates and their mixtures with the corresponding carbonates was studied by mass spectrometry of the gases evolved during heating of the reaction mixtures. For both pure and doped nitrates it changes in the expected row Li>Na>K, following the melts oxobasicity sequence.     

高导热金属基复合材料的热物理性能

分别采用无压浸渗、气压浸渗、内氧化技术制备了高导热Al/SiC、Al/C、Cu/Al2O3复合材料.研究了增强相和界面对这三种复合材料的热导率和热膨胀系数的影响,并对这些性能进行了理论分析和数值模拟.当颗粒尺寸与界面层厚度之比固定时,颗粒尺寸对Al/SiC复合材料热导率影响很小,但界面热导率对其影响很大;Al/SiC复合材料的CTE随温度的升高而增加,随SiO2层厚度的增加而减小;碳纤维中混杂3%SiC颗粒有利于改善纤维的分布,降低Al/C复合材料的缺陷,并提高其热导率;压力加工增加了Cu/Al2O3的致密度,也提高了其热导率;可用Schapery和Kerner模型计算复合材料的热膨胀系数,用Hasselman-Johnson模型计算热导率.     

Electrical conductivity of platinum metal — nonplatium metal double oxides

The authors have determined an electrical conductivity type for 145 platinum metal-nonplatinum metal double oxides such as Ln₂M₂O₇ pyrochlores, AMO₃ perovskites, ARh₂O₄ spinels, Rh MO₄ rutiles, M_xPd₃O₄ and M_xPt₃O₄ bronzes, etc. It was shown that conductivity type is a certain function of the d-electron configuration of platinum metal ion in the double oxide, namely the double oxide with d⁴ or d⁵ electron configuration for platinum metal ion exhibits metallic conductivity while the oxide with d⁶ or d⁸ electron configuration for the ion is a semiconductor.     

Direct intercalation of alkali metal ions in FeOCl

The direct intercalation of Li⁺, Na⁺, K⁺ and their crown ether complexes has been observed when FeOCl reacts with the respective methoxide salts of these ions. The lattice parameters of the compounds formed are reported. The intercalation process is interpreted in terms of oxidation of the methoxide ion accompanied by a partial reduction of the Fe(III) in the FeOCl, with the intercalation of the alkali metal ion in the lattice for charge compensaion.     

Surface ionization properties of alkali metal oxide bronze

The process of selective ionization of a nitro compound (trinitrotoluene) on the surface of poly- and single-crystalline samples of sodium-vanadium oxide bronze has been studied in air at atmospheric pressure.     

Electrical conductivity of sol-gel derived metal nanoparticles

Electrically conducting films of thickness 2 m have been prepared on ordinary glass slides by growing ultra-fine particles of iron and copper, respectively, from a suitable precursor sol. The diameters of metal particles can be varied from 3–13 nm by controlling the heat-treatment schedule of the sol coating. Resistivity measurements (d.c.) have been carried out over the temperature range 80–300 K. The resistivity values in the range 0.0001–0.0039 cm have been obtained depending on the particle diameter and the type of metal used. The effective Debye temperature _D for the different nanoparticle systems have been estimated by fitting the experimental data to the Ziman equation. _D is found to vary from 346–408 K for iron with the particle size in the range 3.4–9.5 nm. The values obtained for copper are 243–307 K with particle diameters covering a range of 5.9–12.6 nm.     

Size and temperature dependences of the resistivity of thin alkali metal wires at liquid nitrogen,hydrogen and helium temperatures

The temperature variation of the resistivity ?, the size effect on the resistivity and the residual resistivity were investigated for thin wires of the alkali metals Na, K, Rb and Cs (which were of high purity and had a high crystalline order) from room to liquid He temperatures.The results obtained allowed us to determine the fundamental quantity ?_∞l and also the resistivity ?(T)_∞ of the bulk metal and the mean free path l(T) of the conduction electrons.The values of ?_∞l obtained near 0 K for these thin alkali metal wires of high crystalline order were found to correspond, within experimental error, to those obtained previously using highly disordered thin films of the same alkali metals at liquid nitrogen temperatures. Both sets of ?_∞l valuescorrespond to the values expected theoretically according to the fundamental equation $\text{1}\text{?}{}_{\mathrm{\infty }}\text{l}\text{=}\text{const.}\text{× N}{}^{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}$ (where N is the density of effective conduction electrons), thus proving that ?∞l is independent of temperature and of degree of crystalline order as expected.The results on the temperature variation of the resistivity ?(T)_pho due only to electron-phonon scattering reveal a T⁵ law for Na in the temperature interval 15?T?20 K and for Rb and Cs in the range 1.6?T?3 K, and a T³ law for K in the range 14?T?20 K. Moreover, at temperatures below 4 K the resistivities of the thinnest wires of Cs and, to a lesser extent, of Rb deviate from Matthiessen's rule, thus revealing a temperature-dependent size effect.     

Two-atom hydrogen clusters and diffusion of hydrogen in metal

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 25, No. 3, pp. 7–12, May–June, 1989.