The effect of pressure on the thermal conductivity of ordered and disordered alloys

A comparison is made between the results from experimental studies into the effect of hydrostatic pressures of up to 400 MPa in the temperature range 273–523 K on the phonon thermal conductivity of CdSnAs₂ alloy and the effective thermal conductivity of granite. Pressure was demonstrated to lead to a change in the degree of structural ordering of the studied specimens.     

Investigation of the beryllia ceramics molding process by the hot casting method

Results of mathematical simulation of the ceramics molding process by the hot casting method are presented. The mathematical model describes the motion of beryllia liquid thermoplastic slurry in a form-building cavity subject to solidification. Velocity and temperature profiles providing homogeneous properties of the beryllia ceramics in the process of molding by the hot casting method are obtained.     

Magnetocaloric effect and the heat capacity of ferrimagnetic nanosystems in magnetic fluids

The specific heat capacity of a magnetite-based magnetic fluid and changes in the magnetic part of the molar heat capacity of its magnetic phase in magnetic fields of 0–0.7 T were determined calorimetrically over the temperature range 288–353 K. The temperature dependence of changes in the magnetic part of entropy in an applied magnetic field was calculated. It was found that the field dependence of heat capacity had a maximum in fields of 0.3–0.4 T, and the temperature dependences of changes in the magnetic part of heat capacity ΔC _p (H) and entropy ΔS _m(H) had maxima at the magnetic phase transition temperature.     

Adsorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of highly dispersed manganese and copper ferrites

A comparative study of adsorption-desorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of manganese and copper ferrites is performed by means of equilibrium adsorption. Adsorption isotherms of fatty acids are described in terms of the theory of volume filling of micropores, and the values of the limiting adsorption, the characteristic adsorption energy, and the pore space volume are calculated. It is established that the limiting adsorption values of linoleic and linolenic acids from solutions in carbon tetrachloride on a copper ferrite surface are higher than on a manganese ferrite surface. It is shown that the adsorption-desorption isotherms have a hysteresis loop.     

Effect of uniform pressure on the energy spectrum of electrons and the kinetic properties of II-IV-V2 semiconductors

Conclusion The data surveyed above for IV semiconductors and III–V groups indicate the effectiveness of applying uniform pressure in investigating the electron energy spectrum, transport effects, optical and other properties of II-IV-V₂ semiconductors. Similar studies have only started, and their continuation is, obviously, recommended. However, the results obtained, mostly complex studies on the model object CdSnAs₂ for the II-IV-V₂ group, allow us to diagnose with some degree of probability the nature of the action of uniform pressure on electron energy spectra and their scattering mechanisms. Experiments under high pressure conditions play a particularly important role in investigating the behavior of impurities and various kinds of defects.Since a substantial portion of the study was devoted to investigation results in CdSnAs₂, the numerical values of the basic parameters of the band structure are given in Table 2, where the most reliable values, in our opinion, were given. A quite complete bibliography is available in [7, 9, 10], while attention must also be turned to [45, 48, 57, 58].The width of the band gap E_G=E_c(₇)-E_v(₆) (Fig. 1) and its temperature coefficient were determined by the present authors by analyzing data on the intrinsic absorption [52] and the temperature dependence of the Hall coefficient [62].The Authors are grateful to V. D. Prochukhan, G. K. Averkiev, C. P. Vul', V. N. Portnov, O. V. Voevodin, and V. G. Voevodin for supplying them with CdSnAs₂ crystals.Translated from Ivestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 98–111, August, 1986.     

Structural effects of solvation of unsaturated fatty acids C18:n in tetrachloromethane found in investigations of the volumetric properties of solutions

The limiting partial molar volumes of solutes and excess molar volumes of their mixtures with nonpolar solvents are calculated on the basis of precise (error ≤ 5·10^?6 g·cm^?3) densitometric measurements for dilute solutions of oleic, linoleic, and linolenic acids in tetrachloromethane at 298.15 K. It is found that self-association processes of the components of the mixtures play the key role in dissolution effects of fatty acids in CCl₄. As the number of C=C double bonds in the acid molecule increases, acid desolvation becomes less pronounced and is accompanied by compression (reduction of volume) of the structural packing of the solvate complex formed due to the strengthening interaction of the acid with tetrachloromethane.     

Spectral holographic imaging of transparent objects in Mach−Zehnder interferometer using acousto-optic filter

The problem of digital holographic imaging of optically transparent objects in arbitrary spectral intervals is discussed. An optical scheme based on Mach?Zehnder interferometer with acousto-optic filtration of broadband light is proposed, and an experimental setup is described. Digital holograms of test patterns and real biological objects are presented.     

Physicochemical properties of magnetic fluids based on synthetic oils

A technique for synthesizing magnetic fluids based on Alkaren synthetic oil is described. The optimum synthesis conditions for the magnetite are selected, and the magnetic phase-stabilizer quantitative ratio is calculated. A magnetic fluid based on synthetic hydrocarbon oil is synthesized, and its physicochemical characteristics are determined.