Variation of Surface Nanostructures on (100) PbS Single Crystals during Argon Plasma Treatment

The nanostructuring of the (100) PbS single crystal surface was studied under varying argon plasma treatment conditions. The initial PbS single crystals were grown by high-pressure vertical zone melting, cut into wafer samples, and polished. Subsequently, the PbS single crystals were treated with inductively coupled argon plasma under varying treatment parameters such as ion energy and sputtering time. Plasma treatment with ions at a minimum energy of 25 eV resulted in the formation of nanotips with heights of 30–50 nm. When the ion energy was increased to 75–200 eV, two types of structures formed on the surface: high submicron cones and arrays of nanostructures with various shapes. In particular, the 120 s plasma treatment formed specific cruciform nanostructures with lateral orthogonal elements oriented in four <100> directions. In contrast, plasma treatment with an ion energy of 75 eV for 180 s led to the formation of submicron quasi-spherical lead structures with diameters of 250–600 nm. The nanostructuring mechanisms included a surface micromasking mechanism with lead formation and the vapor–liquid–solid mechanism, with liquid lead droplets acting as self-forming micromasks and growth catalysts depending on the plasma treatment conditions (sputtering time and rate).

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.

Phase structures and magnetostriction of Fe71.3Ga28.7 alloys prepared by different solidification rates

Magnetostrictive property shows anisotropic characteristics, which are related to phase structure and crystal orientation. In this paper, phase structures and magnetostrictive properties of Fe[Formula: see text]Ga[Formula: see text] at different solidification rates during zone-melting directional solidification were studied. Results show that when the solidification rate exceeds 72 mm/h, the sample has a single A2 structure. A multiphase structure of D03 and A2 is formed when the solidification rate is 36 mm/h. The multiphase structure of L12 and A2 emerges in the sample prepared with a solidification rate of 18 mm/h. The samples with L12 and A2 multiphase structure have excellent low-field magnetostrictive properties, reaching 68 × 10[Formula: see text] under a magnetic field of 20 kA/m.

THE REFINING OF TITANIUM BY CRUCIBLELESS ZONE MELTING METHOD

The physical substantiation of titanium refining by crucibleless electron beam zone melting (ZM) method in vacuum was presented. Calculations of the equilibrium, limiting and effective distribution coefficients for impurity elements in the base metal were carried out. The refining of titanium was studied experimentally, and samples with a purity of 99.92 wt.% were received. The total content of impurities was reduced by a factor of 1.5 (from 0.12 to 0.08 wt.%). The concentration of interstitial impurities was significantly reduced (oxygen – by 1.3; carbon – by 2; nitrogen – by 2.5 times). The structure and microhardness were investigated.

High- and Ultra-High-Purity Aluminum, a Review on Technical Production Methodologies

Aluminum and aluminum-based alloys have been used for many years. In view of the increase in material purity requirements of advanced technology products, research regarding high-purity aluminum has gained significant attention in recent years. In this review, we seek to describe the fundamental purification principles and the mechanisms of various segregation techniques used to produce high-purity aluminum. Moreover, we aim to provide an overview of high-purity aluminum production, with particular emphasis on: (a) principles on how to produce high-purity aluminum by layer- and suspension-based segregation methods; (b) discussion of various influencing process parameters for each technique, including three-layer electrolysis, vacuum distillation, organic electrolysis, suspension-based segregation, zone melting, Pechiney, Cooled Finger, and directional solidification; as well as (c) investigations of fundamental working principles of various segregation methods and corresponding reported end-purification for the production of HP-Al. Eventually, the end-reported product purity, and advantages and disadvantages of various purification methods and technologies are summarized. By analyzing and comparing the characteristics of different methods, we put forward suggestions for realizing efficient and environmentally friendly production of high-purity aluminum in the future.