D.c. conductivity of V2O5–MnO–TeO2 glasses

Semiconductive oxide glasses in the system V2O5–MnO–TeO2 were prepared, and the mechanism of d.c. conduction was studied. The Seebeck coefficient measurements at temperatures from 375–475 K indicated the glasses to be n-type semiconducting. The d.c. conductivity ranged from 5×10–5 to 1.9×10–6 S cm–1 at 405 K for V2O5=60 mol% and MnO=0–20 mol%, and decreased with increasing MnO content. The conduction was confirmed to obey the adiabatic small polaron hopping model, and was due to mainly hopping between V-ions in the glasses. The polaron band width J was estimated to be J=0.10–0.20 eV. The electron–phonon interaction coefficient p was very large (21–26). The hopping mobility evaluated as 2.3×10–7–2.7×10–6 cm2 V–1 s–1 increased with increasing V2O5 content. The estimated carrier concentration was the order of 1019 cm–3. The principal factor determining conductivity was the polaron hopping mobility in these glasses. © 1998 Chapman & Hall     

High-temperature thermoelectric properties of the sintered Bi2Sr2Ca1 − xYxCu2Oy (x = 0 – 1)

Electrical conductivity and Seebeck coefficient were measured in a temperature range of 320–1073 K for sintered samples of Bi₂Sr₂Ca_{1 – x} Y _x Cu₂O _y (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). It has been found that the conduction behavior changes from n-type metallic to p-type semiconducting with increasing yttrium concentration. The power factors were in a range of 1.7–3.0 × 10^–5 Wm^–1 K^–2 for the sample with x = 0.8, being maximized by the optimization of the yttrium concentration. The thermal conductivity for the sample with x = 0.8 was 0.73 Wm^–1 K^–1 at 310 K, and decreased with increasing temperature. The values of thermoelectric figure of merit were estimated to be in a range of 3.4–4.8 × 10^–5 K^–1 at temperatures of 320–673 K for the sample with x = 0.8.     

Sol–gel processing of hydroxyapatite

Hydroxyapatite, a calcium phosphate-based compound with numerous applications in the biological field was synthesized using the sol–gel processing route. The formation of hydroxyapatite and other compounds during the heat-treatment cycle were identified and characterized using thermal analyses and X-ray diffraction together with infrared and Raman spectroscopy. The influence of the addition of various organic alcohols (R–OH, R=CH3–, C2H5– and C3H8–) on the reaction results was studied. © 1998 Kluwer Academic Publishers     

Experimental study of the heat transfer in porous semitransparent heat-shield materials

Studies of the stationary heat transfer and effective heat conductivity of two materials in the temperature range T = 573–1473 K and the air-pressure range p = 1–10⁵ Pa have been made. A comparative analysis of the heat transfer in them and other porous materials is given.__________Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 1, pp. 60–66, January–February, 2005.     

Calculation of the density of solutions (sunflower oil +n-hexane) over a wide range of temperatures and pressure

We present the results from an experimental investigation of the density of the sunflower oil system as a function of the mass concentration of n-hexane in the ranges of temperatures T=290–520 K and pressures P=0.101–98.1 MPa. A method of hydrostatic weighing was used to measure the density of the solutions under study.K. Dzhuraev Dushanbe State Pedagogical University, Tadzhikistan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 5, pp. 789–792, September–October, 1995.     

Synthesis and Properties of Ln3In5S12

Ln₃In₅S₁₂ compounds were characterized by physicochemical analysis and electrical measurements. All the compounds studied crystallize in monoclinic symmetry and are isostructural. In the series La₃In₅S₁₂–Lu₃In₅S₁₂, the lattice parameters vary in the ranges a = 11.36–10.74 Å, b = 21.49–20.94 Å, c = 4.06–3.72 Å, and = 98.8°–98.4°. The photoelectric properties of Ho₃In₅S₁₂ crystals doped with Sn, Zn, Cu, and Cd were studied at 77 and 300 K. The Cd-doped crystals showed no appreciable photoresponse around the fundamental absorption edge.     

General characteristics of supersonic vortical boundary layers

Results are shown of a study concerning the velocity profile, the velocity of discrete vortices, and the thickness of supersonic vortical boundary layers. Measurements were made with the Mach number M = 1.7–3.0 and with the Reynolds number Re = 4.4 · 10⁵-4.0⁷.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.22, No. 5, pp. 885–889, May, 1972.     

Layered 4He in Hectorite: A New Quasi-Two-Dimensional Environment for Quantum Liquids

We have studied the properties of quasi-two-dimensional ⁴He in an environment provided by the layered structure of hectorite. A phase transition occurs for areal densities between n=0.029 Å^–2 and n=0.032 Å^–2 where the structure of ⁴He changes abruptly from a 4-layer to a 5-layer configuration. The signatures of this phase transition are detectable in the static density–density response function and in the density–dependence of the roton minimum.     

Measurement of the Surface Tension of Undercooled Liquid Ti90Al6V4 by the Oscillating Drop Technique

The surface tension of liquid Ti₉₀Al₆V₄ was measured. The samples have been processed containerlessly by electromagnetic levitation, which allows the handling of highly reactive materials and measurements in the undercooled temperature region. The use of digital image processing allows the identification of oscillation modes and calculation of the surface tension from the l = 2 and m = 0, m = 2 oscillation modes. A linear least squares fit to the data showed the following temperature dependence: = 1.389 ± 0.09 – 9.017 × 10^–4 ± 5.64 × 10^–5(T – 1660°C) [Nm^–1]     

Structure and ionic conduction in the Ag2O·WO3·TeO2 glass system

Preparation, characterization by X-ray diffraction, differential scanning calorimetry, X-ray photoelectron spectroscopy (XPS), Raman and Fourier transform–infrared (FT–IR) spectroscopy and electrical conductivity studies have been carried out on the yAg2O · (1–y) [xWO3·(1–x) TeO2] glass system. The compositional variation of the glass transition temperature and the calculated oxygen packing density values have been correlated. The conductivity at ambient temperature shows two maxima for the compositions corresponding to y = 0.30 and 0.40 at x = 0.2 and 0.4, respectively. The observed conductivity enhancement is about an order of magnitude and it is correlated to the structural modifications due to the WO3 incorporation into the TeO2 glass network. From the XPS spectra, the binding energies (BEs) of the Ag 3d, Te 3d, W 4f and O 1s core-levels have been determined. The O 1s spectrum is found to consist of two peaks due to the presence of Te–eqOax–Te, W–O–W, W–O, Te = O, Te–O–1 and W–O–1 oxygen species. The tungsten ions appear to exist in 5+ and 6+ oxidation states in these glasses. The proportion of the reduced tungsten ion is found to decrease with an increase in the WO3 concentration, while that of the Te–eqOax–Te species decreases as x increases. The FT–IR and Raman spectra of these samples reveal that the glass network consists of TeO4, TeO3, WO4 and WO6 polyhedra.     

Investigation of the intensification of heat transfer during flow of gases and liquids in pipes

The article presents the results of an experimental investigation of intensification of heat transfer by means of periodically arranged annular diaphragms in pipes with heating and cooling of air, carbon dioxide, helium, water, and water-glycerol mixture in the range Re = 500-2 · 10⁵ and Pr=0.7–50.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 4, pp. 592–599, April, 1971.     

Electrical resistivity,nucleation and crystal growth in amorphous Se100−x -Sb x ,

The process of nucleation and crystal growth has been studied, using the change of the electrical resistance with time, for the system Se_100–x -Sb _x , wherex = 5, 10 and 15. The X-ray analysis of different records was also used to investigate the same processes. The results show that the apparent activation energies of nucleation were 17.89, 19.88 and 24.25 kcal mol^–1 (74.90, 83.23 and 101.53 kJ mol^–1) for x = 5, 10 and 15, respectively. The values of the apparent activation energy of crystal growth were 39.78, 45.67 and 52.70 kcal mol^–1 (166.55, 191.21 and 220.64 kJ mol^–1 ) for the same respective samples. The activation energy of conduction and the electrical resistance were found to decrease as the antimony content increases in both amorphous and crystalline states.     

Unsteady heat transfer in transverse airflow past a cylinder

The airflow cooling of a thin-walled hollow copper cylinder is investigated in the range of Reynolds numbers Re=10⁴–10⁵.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 5, pp. 813–819, May, 1980.     

Influence of the technological conditions on the luminescence of Eu3+ ions in Sr2SnO4

Different synthesis conditions have been used to prepare the stoichiometric compounds of the Sr2–xEuxSnO4 with x=0.00, 0.01, 0.02 and 0.03. As the 5D07F0 transition is forbidden by a selection rule of the Judd–Ofelt theory, the J=0J=0 level gains some intensity from the mixing of J states in the Sr2–xEuxKxSnO4 and Sr1–xEuxSnO4 samples. For Sr2–xEuxSnO4 samples prepared under a slightly reducing atmosphere, the J=0J=0 transition is split into two peaks, which confirms the substitution of Eu3+ ions for different crystallographic sites. © 1998 Chapman & Hall     

Thermomechanical processing of Ti–5Al–5Mo–5V–3Cr

The constitutive behaviour and microstructural evolution of the near-β alloy Ti–5Al–5Mo–5V–3Cr in the α + β condition has been characterised during isothermal subtransus forging at a range of temperatures and strain rates. The results indicate that Ti–5Al–5Mo–5V–3Cr has a shallower approach curve, and therefore, offers a more controllable microstructure than the near-β alloy Ti–10V–2Fe–3Al. Flow softening is small in magnitude in both alloys in the α + β condition. The steady state flow stresses obey a Norton–Hoff constitutive law with an activation energy of Q = 183 kJ mol⁻¹, which is similar to the activation energy for self-diffusion in the β phase, suggesting deformation is dominated by dynamic recovery in the β matrix. Good evidence is found for the existence of ω phase after both air cooling and water quenching from above the β transus. In addition, dissolution of the α phase is found to be slow at near-transus temperatures.     

Specific features of the interaction of alloys of the didymium-iron-boron system with hydrogen

We study the interaction of alloys of the Dd-Fe-B system [M-82, M-83, M-84, and M-85 alloys with a mass content of 33–40% didymium, up to 0.5% aluminum, and 1–1.25% boron (the rest is iron)] with hydrogen using volumetric, X-ray phase, and differential thermal analysis. If the initial hydrogen pressure is 1.0 MPa, hydrides with 0.4–0.6 mass % of hydrogen are formed. The saturation of these alloys with hydrogen is accompanied by an increase in the spacing a of an elementary cell by 1.2–1.4% and in c by 0.8–1.1% (the general increase in volume is 3.2–3.9%). If the initial pressure is 0.15–0.2 MPa, the time of complete saturation with hydrogen is 15–20 min for most alloys. At 973–1033 K, the alloys under study in hydrogen disproportionate into DdHx didymium hydride (a = 0.5449 – 0.5458 nm), -iron (a = 0.2864 – 0.2866 nm), and Fe2 B iron boride (a = 0.5112 – 0.5117 nm, c = 0.4228 nm). An increase in the initial hydrogen pressure from 0.1 to 5.0 MPa is accompanied by a decrease in the disproportionation temperature to 930 K.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 2, pp. 105–112, March–April, 2004.     

The oxidation of TiC in dry oxygen, wet oxygen, and water vapor

Isothermal oxidation of TiC was studied using powder sample at 300–400°C in Ar/O₂ = 95/5 kPa (dry oxidation) and Ar/O₂/H₂O = 90/5/5–10 kPa (wet oxidation), and at 520–650°C in Ar/H₂O = 95/5–15 kPa (H₂O oxidation) by monitoring weight changes. The phases produced were identified by X-ray analysis and the oxidized sample was observed by scanning and transmission electron microscopy. The dry, wet and H₂O oxidation of TiC was found to be described by a one-dimensional diffusion-controlling equation. It was revealed that the oxidation was divided into three steps, slow step I, fast step II, and slow step III. Water vapor in the wet oxidation accelerated these three steps, particularly step II. Non-isothermal oxidation of TiC was also performed to simultaneously monitor the evolved gases (CO/CO₂, H₂, CH₄) with weight changes by thermogravimetry and mass analysis. The accelerating effect of water vapor on oxidation of TiC was discussed from kinetic and thermoanalytical viewpoints.     

Heat Transfer at Mixed Convection in Vertical and Inclined Flat Channels of the Vacuum Chamber of the ITER International Thermonuclear Reactor

The results are given of the experimental investigation of the intensity of heat transfer from flat surfaces of a model of the vacuum chamber channel of the international thermonuclear experimental reactor (ITER), inclined to the horizontal at an angle of (5–90)@deg, with different heights (12–50) mm, heated length (1.02 and 2.48) m of the model and low velocities of water flow (0.0067–0.17) m/s that are characterized by the values of Re = 560-17 900. The specific heat flux on the heat-transfer surfaces is q = (1.3–24.4) kW/m². The treated range of parameters is characterized by the interaction of forced and natural convection with a significant temperature stratification of the flow in inclined channels. Closing relations are suggested on the basis of the experimental results.     

Turbulent boundary layer on a permeable surface with intensive blowing

Results of an experimental investigation of the structure and integrated characteristics of a turbulent boundary layer on a permeable plate in a broad range of blowing intensities ¯j=0.005–0.04 are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 5, pp. 773–779, May, 1976.     

Non-contact measurements of thermophysical properties of niobium at high temperature

Four thermophysical properties of both solid and liquid niobium have been measured using the vacuum version of the electrostatic levitation furnace developed by the National Space Development Agency of Japan. These properties are the density, the thermal expansion coefficient, the constant pressure heat capacity, and the hemispherical total emissivity. For the first time, we report these thermophysical quantities of niobium in its solid as well as in liquid state over a wide temperature range, including the undercooled state. Over the 2340 K to 2900 K temperature span, the density of the liquid can be expressed as _L (T) = 7.95 × 10³ – 0.23 (T – T _m)(kg · m^–3) with T _m = 2742 K, yielding a volume expansion coefficient _L(T) = 2.89 × 10^–5 (K^–1). Similarly, over the 1500 K to 2740 K temperature range, the density of the solid can be expressed as _s(T) = 8.26 × 10³ – 0.14(T – T _m)(kg · m^–3), giving a volume expansion coefficient _s(T) = 1.69 × 10^–5 (K^–1). The constant pressure heat capacity of the liquid phase could be estimated as C _PL(T) = 40.6 + 1.45 × 10^–3 (T – T _m) (J · mol^–1 · K^–1) if the hemispherical total emissivity of the liquid phase remains constant at 0.25 over the temperature range. Over the 1500 K to 2740 K temperature span, the hemispherical total emissivity of the solid phase could be rendered as _TS(T) = 0.23 + 5.81 × 10^–5 (T – T _m). The enthalpy of fusion has also been calculated as 29.1 kJ · mol^–1.