Thermoelectric properties of Ce x Nd y Co4Sb12 skutterudites

Experimental results of studying the thermoelectric properties of Co₄Sb₁₂, Ce_0.1Nd_0.5Co₄Sb₁₂, and Ce_0.5Nd_0.1Co₄Sb₁₂ prepared by induction melting are presented. The thermoelectric figure of merit ZT of the studied Co₄Sb₁₂ is approximately two times higher than ZT of unfilled skutterudites prepared by the conventional solid-phase synthesis method. The figure of merit of Ce_0.1Nd_0.5Co₄Sb₁₂ and Ce_0.5Nd_0.1Co₄Sb₁₂ appears lower than ZT of Co₄Sb₁₂ due to the presence of an impurity phase of metal antimony in the first two samples. It is assumed that the thermoelectric properties of filled skutterudites can be significantly improved by optimizing the induction melting method.

     

Development of the hydraulic circuit theory for solving problems of controlling the operation of heat supply systems

Important lines in the development of hydraulic circuit theory are briefly characterized. New formulations and the main content of the methods of this theory are described with placing emphasis on approaches for solving key issues that hinder further improvement in the efficiency of heat supply systems and quality of controlling their operating conditions. Application of mathematical and computer simulation is central to the proposed approaches.     

Investigation of the dynamic piezoelectric moduli of single crystals of Bi12GeO20, Li2GeO3, and LiNbO3

Conclusions An investigation of the dynamic piezoelectric modulus of single crystals of a pure piezoelectric material (bismuth germanate), a pyroelectric material (lithium germanate), and a ferroelectric material with rigidly fixed domains (lithium niobate) showed that all the above listed crystals can serve as a highly efficient working body of pressure pickups. Crystals of lithium niobate are distinguished by the highest stability; their industrial production has been perfected, and their behavior in shock waves has been rather completely investigated In [3] an investigation was made of the dynamic piezoelectric moduli for three sections of lithium niobate: -Z, Y, 36° -Y; in [26], an investigation was made of the mechanical and electrical reaction of lithium niobate to the action of a shock wave with an intensity exceeding the Hugoniot creep limit. The results set forth in the present article are in agreement with the data of [3, 26].The maximal value of the dynamic piezoelectric modulus for the investigated crystals is that of bismuth germanate, i.e., 13×10^–3 C/(m²·KPa), which is six times greater than the piezoelectric modulus of quartz.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 16, No. 1, pp. 99–105, January–February, 1980.     

Formation of Friction Layers and Wear Resistance of Steels under Conditions of Boundary Friction

We studied the influence of the lubricant compositions Grafitol with 10% graphite (1), Aerol containing 17% MoS₂ (2), Limol containing 60% MoS₂ (3), Limol + 10% chlorine-paraffin (4), and Limol + 10% copper powder (5) on the wear rate and formation of the fine structure of surface friction layers of structural steels. We established a correlation between the tribological characteristics of steels and lubricants. The abrasive wear of 40KhFA steel was minimum if it was lubricated with Limol + 10% copper powder. In this case, its wear was smaller by a factor of 10, 2, 1.25, and 7.25 as compared with lubricant compositions 1–4, respectively. In the course of minimum wear of 40KhFA steel, in the surface friction layers, we observed the minimum values of second-kind distortions (a/a) and of the true size of domains of X-ray coherent scattering (D) as well as the minimum difference between the crystal lattice constants (a) of steel before and after friction.