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Cu2–xS and Cu2–xSe have recently been reported as promising thermoelectric (TE) materials for medium-temperature applications. In contrast, Cu2–xTe, another member of the copper chalcogenide family, typically exhibits low Seebeck coefficients that limit its potential to achieve a superior thermoelectric figure of merit, zT, particularly in the low-temperature range where this material could be effective. To address this, we investigated the TE performance of Cu1.5–xTe–Cu2Se nanocomposites by consolidating surface-engineered Cu1.5Te nanocrystals. This surface engineering strategy allows for precise adjustment of Cu/Te ratios and results in a reversible phase transition at around 600 K in Cu1.5–xTe–Cu2Se nanocomposites, as systematically confirmed by in situ high-temperature X-ray diffraction combined with differential scanning calorimetry analysis. The phase transition leads to a conversion from metallic-like to semiconducting-like TE properties. Additionally, a layer of Cu2Se generated around Cu1.5–xTe nanoparticles effectively inhibits Cu1.5–xTe grain growth, minimizing thermal conductivity and decreasing hole concentration. These properties indicate that copper telluride based compounds have a promising thermoelectric potential, translated into a high dimensionless zT of 1.3 at 560 K.

—: We have studied the effect of hydrostatic pressure on the galvanomagnetic properties of a Cd3As2 + 20 mol % MnAs alloy in a transverse magnetic field of up to 4 kOe. The pressure dependences of the Hall coefficient and resistivity for the alloy provide evidence of reversible phase transitions. The observed negative magnetoresistance of the alloy is shown to be induced by high pressure. © 2019, Pleiades Publishing, Ltd.

Materials that combine flexibility and open metal sites are crucial for myriad applications. In this article, we report a 2D coordination polymer (CP) assembled from CuII ions and a flexible meta-carborane-based linker [Cu2(L1)2(Solv)2]•xSolv (1-DMA, 1-DMF, and 1-MeOH; L1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane). 1-DMF undergoes an unusual example of reversible phase transition on solvent treatment (i.e., MeOH and CH2Cl2). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m2 g−1 and is capable of a CO2 uptake of 41 cm3 g−1. The transformation is reversible and 1-DMF is reformed on addition of DMF to the porous phase. We provide evidence for the reversible process being the result of the formation/cleavage of weak but attractive B–H∙∙∙Cu interactions by a combination of single-crystal (SCXRD), powder (PXRD) X-ray diffraction, Raman spectroscopy, and DFT calculations.

The fretting, behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting, behavior of NiTi alloy. Due to the low phase transition Stress (Only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5\%) of NiTi. the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value Of GCr15 plate under the sanae fretting conditions. For NiTi/GCr15 pair. even NiTi has a much lower hardness than GCr15. the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly, caused by, the abrasive wear of the GCr15 debris in the three-body wear mode.

The fretting, behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting, behavior of NiTi alloy. Due to the low phase transition Stress (Only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5\%) of NiTi. the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value Of GCr15 plate under the sanae fretting conditions. For NiTi/GCr15 pair. even NiTi has a much lower hardness than GCr15. the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly, caused by, the abrasive wear of the GCr15 debris in the three-body wear mode.

The fretting, behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting, behavior of NiTi alloy. Due to the low phase transition Stress (Only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5\%) of NiTi. the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value Of GCr15 plate under the sanae fretting conditions. For NiTi/GCr15 pair. even NiTi has a much lower hardness than GCr15. the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly, caused by, the abrasive wear of the GCr15 debris in the three-body wear mode.

Multitemperature X-ray diffraction and vibrational spectroscopic studies of tetracene-tetracyanoquinodimethane (TCNQ) charge transfer cocrystals have revealed the existence of a reversible phase transition in the temperature interval 150-200 K. It was shown that a new monoclinic polymorph of the cocrystal exists above that temperature range, with a structure that is very similar to the one previously described in the literature as being triclinic. The crystal structures of the two polymorphs were also calculated with periodic density functional theory quantum chemical calculations, and their geometries were compared to the experimental ones. The degree of charge transfer in both polymorphs was characterized using alteration in the bond lengths of the TCNQ molecule and frequency shifts obtained from vibrational spectroscopy data. © 2018 American Chemical Society.