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The synthesis of group IV transition metals (TMs) such as Ti, Zr, and Hf from their respective oxides (TMO 2) poses significant challenges with current methods. There is an urgent need for an environmentally friendly and versatile approach to establish sustainable, efficient, and adaptable TM synthesis technology from TMO 2. In this study, the LN process (Lee-Nersisyan), a novel and straightforward approach that employs CaMg 2 as the reductant for TMO 2 powders is introduced. This innovative strategy involves the thermal processing of TMO 2 + k CaMg 2 mixtures (with k values ranging from 2 to 5 moles) in an argon atmosphere at temperatures between 800 and 1200 °C. The process yields high-purity TM powder with particle sizes in the range of 5–25 μm and oxygen content of less than 0.2 wt%. We apply density-functional theory (DFT) to elucidate the interaction energies and equilibrium interatomic distances between Ti-Ca, Ti-Mg, Ca-Mg, Mg-Mg, Ca-Ca, and Ti-Ti metallic pairs. Additionally, we discuss the growth behavior of TM particles through molecular dynamics simulation (MD) employing LAMMPS. Our LN process represents a promising solution for efficient and sustainable TM synthesis from TMO 2. • An innovative method for producing TM (Ti, Zr, Hf) powders from oxides is presented. • Utilizing CaMg 2 as reductant results TM particles with 0.2 wt% of oxygen is obtained. • Calciothermic reduction of TMO 2 is found to be the primary driving force of reaction. • The interaction energies and interatomic distances of M-M pairs are calculated by DFT. • TM particles sintering and growth behavior based on MD simulation is highlighted. [ABSTRACT FROM AUTHOR]

Abstract: This work describes the role of temperature and rolling method on density and microstructure changes in Cu–15% In (wt%) alloy powder during normal and cross-roll rolling. The rolled specimen consisted of two distinct microstructures: α-Cu and Cu7In3 intermetallic compounds. The specimen obtained with 5° of cross rolling degree and 60% of rolling reduction ratio at 600°C has the highest density of 8.812g/cm3. A detailed analysis of these results in terms of the microstructural changes and densification mechanisms is also presented. [Copyright &y& Elsevier]

• Fabricated porous structure in p-type Cu 0.07 Bi 0.5 Sb 1.5 Te 3 compounds by assisting PVA as pore former and studied TE properties. • Lattice thermal conductivity effectively decreased by ~ 38% due to intensified phonon scattering at microscale pores. • The maximum ZT of 1.342 at 400 K and η max of ~ 9.4% at ∆T = 200 K was obtained for the sample with porosity of 10.58%. • The hardness and compressive strength of porous bulks show significantly higher than commercial zone melting materials. [Display omitted] In the background of enhancing thermoelectric (TE) figure of merit of solid-state materials, the introduction of porous structure can significantly decrease lattice thermal conductivity by intensifying phonon scattering at the inhomogeneous microscale pores. Herein, we developed a porous structure in Cu 0.07 Bi 0.5 Sb 1.5 Te 3 compounds by utilizing PVA as the pore former, and systematically studied its effect on thermoelectric properties. The results revealed that the reduction in thermal conductivity (~28%) was greater than the decrease in electrical conductivity (~17%) with increasing porosity, indicating long-wavelength phonon scattering was enhanced at micro-scale pores. Consequently, a peak zT of 1.342 at 400 K, and a zT avg of 1.254 in the temperature range of 300–500 K and an η max of ~9.4% at ΔT = 200 K were achieved in the porous sample (10.58%), which all are higher than that of dense sample. The hardness and compressive strength of the porous samples were significantly higher than commercial zone melting ingots. The proposed methodology is a cost-effective and efficient way of producing high-performance TE devices with good mechanical stability for real life practical applications. [ABSTRACT FROM AUTHOR]

Abstract A lot of efforts being invested into producing efficient thermoelectric devices based on Bi 0.5 Sb 1.5 Te 3 materials for room temperature applications. Key research achievements of these efforts that incorporation of oxide nanoparticles into Bi 0.5 Sb 1.5 Te 3 materials exhibit higher thermoelectric performance in nano-composite form. Here, we prepared Bi 0.5 Sb 1.5 Te 3 nanocomposite incorporated with TeO 2 nanoparticles (NPs) by high energy ball milling and spark plasma sintering, where in-situ Sb 2 O 3 phase and triple functional interfaces were developed. The formation mechanism of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored by the thermodynamic calculations; microstructural features and material composition in the bulk samples were investigated using high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS). The formation of interfaces between in situ senarmontite Sb 2 O 3 nanophase and Bi 0.5 Sb 1.5 Te 3 matrix causes an enhanced Seebeck coefficient by ∼20% due to increase of carrier energy filtering and significant reduction of thermal conductivity by ∼77% ascribed to intensified phonon scattering or trapping at 350 K. As a result, an improved dimensionless figure of merit (ZT) of 1.07 at 350 K was achieved in a Bi 0.5 Sb 1.5 Te 3 /3 wt%TeO 2 composites. The proposed in-situ reaction and interface formation mechanisms are expected to open the possibility of further increases in ZT. Graphical abstract Image 1 Highlights • Formation of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored. • Sb 2 O 3 phase is obtained by in-situ reaction of Sb with TeO 2 during milling and SPS. • The Seebeck coefficient was enhanced owing to increase of energy filtering effect. • Thermal conductivity was reduced (77%) due to phonon scattering at interfaces. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the high-temperature stability of CSZ, YSZ, and MSZ specimens in a CaCl 2 -CaF 2 -CaO molten salt at 1200 °C for the application of the materials as oxygen-ion-conducting solid-oxide membrane anodes in the electroreduction process of metal oxides. YSZ exhibited the lowest degradation among the tested specimens in a high-temperature stability test, whereas CSZ showed the highest degradation. The weight loss was not severe with concentrations of CaO up to 10 wt%. CSZ showed peaks for m-ZrO 2 , YSZ showed peaks for t-ZrO 2 and CaZrO 3 , and MSZ showed peaks for t-ZrO 2 and m-ZrO 2 in 0 wt% CaO. In the case of 5 wt% CaO, all specimens exhibited m-ZrO 2 and CaZrO 3 peaks, In the cases of 10 wt% and 20 wt% CaO, CSZ and MSZ showed peaks for CaZrO 3 , and YSZ showed peaks for m-ZrO 2 and CaZrO 3. While CSZ and MSZ became significantly looser as the CaO concentration was increased to 10 wt%, YSZ became significantly denser due to the formation of a protective layer and attack dependent on the solubility of CaO in the molten CaCl 2. In terms of long-term operation, YSZ was demonstrated to possess superior high-temperature stability compared to CSZ and MSZ, and CaO concentrations from 5 wt% to 10 wt% were found to be significantly more stable than other concentrations. Highlights • The degradation mechanism of CSZ, YSZ, and MSZ in CaCl 2 -CaF 2 -CaO molten salt is proposed. • The formation of CaZrO 3 acts as a protective layer. • YSZ shows high degradation resistance to CaCl 2 -CaF 2 molten salt that contains up to 10 wt% of CaO. • In view of long-term operation, YSZ is demonstrated to possess superior high-temperature stability compared to CSZ and MSZ. [ABSTRACT FROM AUTHOR]

In this study, the isothermal and cyclic corrosion behaviors of custom-made nickel-based alloys (N105, N107, and N108) with various elemental compositions in a LiCl-Li 2 O molten salt were investigated at 650 °C in argon atmosphere. The isothermal and cyclic corrosion behaviors were studied by measuring the mass changes, surface morphologies, cross-sectional morphologies with elemental distribution, and the compositional changes of the subscale and substrate as well as the spalled oxide scale. Under the isothermal and cyclic corrosion test, the corrosion rate was in the order of N108 < N105 < N107, and N107 < N105 < N108, respectively, which depended on the morphology and structure of the crystals formed on the surface of the outer scale in contact with the molten salt, and was also related to the region of Al and Cr depletion. After the isothermal corrosion test, the hot corrosion products formed in N105 were Cr 2 O 3 , NiCr 2 O 4 , and Li 2 Ni 8 O 10 and those in N107 were Cr 2 O 3 and NiCr 2 O 4 , while Cr 2 O 3 , NiCr 2 O 4 , and LiTiO 2 were identified as the hot corrosion products of N108. However, the hot corrosion products of N105, N107, and N108 were Cr 2 O 3 , NiCr 2 O 4 , and LiFeO 2 after the cyclic corrosion test. [ABSTRACT FROM AUTHOR]

The importance of ZT in thermoelectric (TE) materials is critical for green power generation and cooling applications. Therefore, tremendous efforts were underway to improve ZT, in which we proposed a layer structured approach by successively arranging of coarse Bi 0.5 Sb 1.5 Te 3 (BST) and fine BST/0.07Cu microstructure materials and investigated their transportation mechanism. The dual bulk microstructure was well-bonded and confirmed by analyzing the microstructure through scanning electron microscope (SEM), electron backscatter diffraction analysis (EBSD) and simulated the electrical potential and temperature distribution during spark plasma sintering with COMSOL software. The results indicate that the highest power factor of 3.8 mW/m-K2 was attained in the layer structured sample, which is significantly higher than other samples due to its synergistically optimized electrical conductivity and Seebeck coefficient. Through the varied microstructure, the κ was decreased at 400 K and consequently the ZT was improved to 1.25 at 400 K for the layer structure samples. Therefore, it is suggested that layered arrangement of different microstructure material could improve the thermoelectric properties of materials. [Display omitted] • Novel fabrication of hierarchical structured material with successive arrangement of two different microstructures. • Successful consolidation of well-bonded hierarchical material and confirming by simulating results from COMSOL software. • Highest power factor of 3.8 * 10−3 W/m-K2 obtained by transportation of charge carriers through two different energy levels. • Hierarchical structured sample show highest figure of merit of 1.25 at 400 K which is highest among all reported samples. [ABSTRACT FROM AUTHOR]

Evaporation of tellurium (Te) occurs during most of the fabrication methods which leads to a strong deviation on thermoelectric properties. Due to the existence of volatile tellurium has been a great challenge to determine the accurate chemical compositions in the Bi 0.5 Sb 1.5 Te 3 compound for optimizing the carrier concentration. Herein, we systematically verify the reliability and understand the correlations between chemical composition and thermoelectric properties at different portions of large (25 mm), thick (30 mm) samples. The results reveal that spark plasma sintered samples didn't show any significant evaporation of Te. However, the chemical composition slightly changed, resulting in the final thermoelectric figure of merit at different portions of thick samples varied typically within a 10% error. Moreover, this work supports that the selection of the powder fabrication and compaction method plays a crucial role on the final thermoelectric properties of the material, as the combining of gas atomization and spark plasma sintering can prohibit the evaporation of tellurium and any possible inhomogeneous stress field or temperature distribution in large-sized graphite die to SPS. Image 1 • Determined the chemical composition at different portions of large (25 mm) and thick (30 mm) samples. • Gas atomization and subsequent spark plasma sintering process utterly prohibited the evaporation of Te. • Elucidated the relation between chemical composition and thermoelectric properties. • Verified the homogeneity effect at different positions of large-size bulk samples. [ABSTRACT FROM AUTHOR]

Decoupling the Seebeck coefficient, electrical and thermal conductivity has been a great challenge in efforts to obtain thermoelectric materials with a high figure of merit (ZT) for power generation and cooling applications. In this work, p-type Bi 0.5 Sb 1.5 Te 3 samples were fabricated by combining gas atomization and spark plasma sintering. Heat-treatment and subsequent consolidation during SPS stimulated the recrystallization of grains and reduced texture, contributing to reduced carrier scattering. This enhanced carrier mobility by 29%. The recrystallization also induces a hierarchy of fine and coarse crystal grains with random orientations. This mixed microstructure contributed to the simultaneous enhancement of the Seebeck coefficient and electrical conductivity, while reducing lattice thermal conductivity, due to effective phonon scattering by the fine grains and Sb 2 O 3 nanoparticles. The significant improvement in power factor and relatively low κ L resulted in a peak ZT of 1.1 at 350 K for the 470 °C treated sample. This was about 47% higher than the initial sample (ZT = 0.75 at 350 K). The average ZT for all the heat treated samples reached over unity in the range of 300–500 K. This work suggests that the spark plasma heat treatment and consolidation processes enable the recrystallization, allowing the thermoelectric properties to be decoupled, enhancing ZT. Image 1 • The hierarchical structures were formed in Bi 0.5 Sb 1.5 Te 3 alloys via recrystallization. • Decoupled the electrical and thermal properties by forming the hierarchical structures. • Heat-treatment and subsequent consolidation during SPS stimulated the recrystallization of grains and reduced texture. • ZT enhanced by 47% for recrystallized samples than the initial samples. [ABSTRACT FROM AUTHOR]