Obtaining of Copper- and Nickel-Based Polymetallic Gradient Products by Wire-Feed Electron Beam Additive Manufacturing

The structure and mechanical properties of gradient transition zones of the copper-nickel system formed by additive electron beam technology have been investigated. Pure copper and nickel alloy Ni80Cr20 were used for printing. The data obtained testify to the complex and heterogeneous nature of structure formation when printing both by single-wire method and using double-wire controlled feeding of material into the melt bath. In the samples, the formation of defects of different scale from local inhomogeneities of the structure to pores and cracks is possible. The mechanical properties of the structural gradient zone are at a sufficiently high level and depend on the ratio of the system components.

Ce Filling Limit and Its Influence on Thermoelectric Performance of Fe3CoSb12-Based Skutterudite Grown by a Temperature Gradient Zone Melting Method

CoSb3-based skutterudite is a promising mid-temperature thermoelectric material. However, the high lattice thermal conductivity limits its further application. Filling is one of the most effective methods to reduce the lattice thermal conductivity. In this study, we investigate the Ce filling limit and its influence on thermoelectric properties of p-type Fe3CoSb12-based skutterudites grown by a temperature gradient zone melting (TGZM) method. Crystal structure and composition characterization suggests that a maximum filling fraction of Ce reaches 0.73 in a composition of Ce0.73Fe2.73Co1.18Sb12 prepared by the TGZM method. The Ce filling reduces the carrier concentration to 1.03 × 1020 cm−3 in the Ce1.25Fe3CoSb12, leading to an increased Seebeck coefficient. Density functional theory (DFT) calculation indicates that the Ce-filling introduces an impurity level near the Fermi level. Moreover, the rattling effect of the Ce fillers strengthens the short-wavelength phonon scattering and reduces the lattice thermal conductivity to 0.91 W m−1 K−1. These effects induce a maximum Seebeck coefficient of 168 μV K−1 and a lowest κ of 1.52 W m−1 K−1 at 693 K in the Ce1.25Fe3CoSb12, leading to a peak zT value of 0.65, which is 9 times higher than that of the unfilled Fe3CoSb12.

Варизонные гетероструктуры Al-=SUB=-x-=/SUB=-In-=SUB=-y-=/SUB=-Ga-=SUB=-1-x-y-=/SUB=-P-=SUB=-z-=/SUB=-As-=SUB=-1-z-=/SUB=-/GaAs для фотоэлектрических преобразователей

The AlxInyGa1-x-yPzAs1-z/GaAs graded-gap heterostructures were grown by the temperature gradient zone recrystallization with a liquid zone reciprocating, where energy band gap varied from 1.43 to 2.2 eV. The influence of technological parameters on the varying in the energy band gap of the grown AlxInyGa1-x-yPzAs1-z/GaAs solid solutions is investigated. In the p-AlxInyGa1-x-yPzAs1-z/n-GaAs heterostructure, the maximum energy band gap gradient of 10490 eV/cm is reached, and an increase in the external quantum efficiency is shown in the wavelength range of 500-900 nm.

Revisiting Gradient Layer Heat Extraction in Solar Ponds Through a Realistic Approach

In this paper, the concept of heat extraction from the gradient zone (GZ) in solar ponds has been analyzed in a more realistic manner to overcome the drawbacks of previously conducted studies. For this purpose, a net heat transfer coefficient has been invoked to investigate the heat transfer occurring from the GZ to the exchanger installed in this zone, in addition to the storage zone (SZ). Analytical solutions for temperature profiles in the GZ and the corresponding exchanger have been obtained which are further used to investigate various aspects of the thermal performance of the pond. The consideration of realistic heat transfer across the GZ exchanger reveals that the ideal thickness of GZ yielding maximum power output is always under-predicted by the idealized assumption of the literature. Unlike intuitive perception, the conventional assumption of an infinite heat transfer coefficient does not affect the pond stability because, for all practical purposes, the critical salt diffusion rate predicted by it is always larger than the actual critical value required for ensuring stable pond operation. However, as expected, the rate of exergy destruction caused by the pond’s operation is found to be underestimated by the idealized assumption. This study provides a useful analytical tool to make more realistic predictions on various performance parameters of solar ponds utilizing the heat stored in their GZ.