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MgAl2O4–W composite was synthesized by aluminothermic reducing method using Al, WO3, MgO and corundum as raw materials under coke protection. The effects of temperature, content of corundum on the synthesis of MgAl2O4–W composite and lattice parameter of spinel has been discussed. The differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis indicated that spinel began to form at 1058.2°C without corundum and shifted to 1120.7°C with 0.8 mol of corundum. The XRD analysis confirmed that spinel and tungsten are the main phases under coke protection. Alumina rich spinel with a high solubility of alumina was easily formed because of the high exothermic heats. The solubility limit of Al2O3 in spinel is reached when corundum content is 2.1 mol. Furthermore, the calculated lattice parameter of spinel increases with the increment of added corundum content and rising of temperature. Microstructural observation indicates that cubic tungsten located at grain boundaries of well crystallized spinel. Residual WO3 has needle like morphology.

Combining Gleeble hot compression and tensile tests with finite‐element (FE) simulations, this study delivers a robust assessment of the elevated temperature damage and cracking of AISI 410 martensitic stainless steel. The effects of hot deformation parameters on the macroscopic flow and deformation behaviors as well as microscopic damage and fracture characteristics are discussed, determining the critical damage values with the aid of FE calculations. Furthermore, a novel critical damage value model is proposed using the Zener–Hollomon parameter to establish the normalized Oyane fracture criterion coupling hot deformation parameters. The results reveal that the flow stress and tensile load both increase, as the strain rate increases and the temperature decreases and vice versa. The occurrence of localized necking and internal damage cracking causes the tensile load to decline drastically. The hot deformation parameters manipulate not only the plat and dimple fractures, each caused by intergranular and transgranular fractures, but also the internal damage cracking before the final fracture. The established criterion predicts outcomes in good agreement with experimental results. This work provides essential information and a model for the cracking prediction of AISI 410 steel at elevated temperatures, helping to derive a rational hot forming design to prevent cracking. [ABSTRACT FROM AUTHOR]

The flow and densification behaviors of powder metallurgy (PM) Fe-0.5C-2Cu (wt%) steel are investigated by conducting isothermal hot compression tests on a Gleeble 3800 thermo-simulator in the temperature range of 850-1000 °C, a strain rate of 0.01-10 s−1, and a compressibility of 35-65%. It is found that the true stress-strain curves obtained from the hot compression tests demonstrated the characteristics typical of persistent hardening as the gradual decrease of the stress rise. The experimental results show that the flow and densification behaviors of the PM steel are greatly affected by the deformation temperature, strain rate, and deformation amount. A constitutive equation that predicts the dynamic flow stress and relative density in hot compression of the PM steel is established. The predicted values of flow stress and relative density are in good agreement with the experimental results, which demonstrate that the proposed constitutive equation is able to well characterize the flow and densification behaviors of the PM steel at elevated temperatures. The present study can provide important and basic data for the finite element simulation of plastic working processes of the PM steel. [ABSTRACT FROM AUTHOR]

Thermal oxidation of Cu substrate in air is one of the most practical preparation methods for the preparation of CuO nanowires (NWs). Many efforts have been made to tune the CuO morphology, while there is quite rare report on the CuO morphology tuning by adjusting the copper substrate. In the present work, novel hierarchical porous Cu and the directional microporous Cu structures were prepared by etching Cu–Fe 3D printing precursors with or without ultrasonic treatment, respectively. Hierarchical nanostructures composed by CuO NWs within directional microporous Cu have been successfully prepared by thermal oxidizing a directional microporous Cu. The effect of the nanoporous Cu on the formation of the hierarchical nanostructures and the hierarchical nanostructures' morphology evolution were investigated. This work provides a novel insight into the preparation of hierarchical nanostructures by coupling nanostructures with the directional microporous structure. • CuO NWs prefer to grow on the nanoporous Cu areas in the hierarchical porous Cu structure after thermal oxidization. • Directional microporous Cu was prepared by ultrasonic treating of the hierarchical porous Cu structure. • CuO NWs grow within the directional microporous Cu to form a hierarchical nanostructure by thermal oxidization. • The CuO NWs are mainly distributed on the concave part of the inner surface in the directional microporous Cu. [ABSTRACT FROM AUTHOR]

The hydrotalcite (HT) film is a promising bioactive coating for magnesium alloys. In the present study, we investigate the corrosion behavior of HT film in the simulated body fluid (SBF), and compare with which in NaCl solution. The HT film can provide a very plummy initial protection to the AZ31 alloy in SBF. The corrosion behavior of the HT film in the two solutions is quite different. When in 0.1 mol·L−1 NaCl solution, the film is dissolved gradually, and filiform corrosion is predominant after 3 days immersion. While in Hank's solution, the thickness and composition of the film are changed. A corrosion products layer mainly consisted of Mg/Ca–PO43−/HPO42−, and minor of CaCO3 is deposited on the top of HT film, which enhances the barrier effect of the HT film. As a result, except for local pit corrosion at several active places, most of the area of the coated sample still remains integral even after immersion for 15 days. It is demonstrated that the HT film has better corrosion protection effect in SBF than in NaCl solution. [ABSTRACT FROM AUTHOR]

A series of Eu3+-activated Sr 2 LaTaO 6 red phosphors were synthesized by the traditional high temperature solid-state reaction process. The structure and photoluminescence properties of the phosphors were characterized using X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DR) and fluorescence spectrometer. The phosphors could emit bright red light upon 393 nm near ultraviolet light excitation. The dominant emission peaked at 613 nm corresponds to the electric dipole transition 5D 0 →7F 2 of Eu3+. The optimum doping concentration of Eu3+ ions was 15%, the emission intensity reaching the maximum, beyond which the concentration quenching happened. The representative phosphor Sr 2 La 0.85 TaO 6 :0.15Eu3+ exhibited a chromaticity coordinates of (0.6263, 0.3732) in red-light area with a low correlated color temperature (CCT) of 1759 K and a high color purity of 89.2%. It can be concluded that Sr 2 LaTaO 6 :Eu3+ phosphors have good potential as a red-emitting component for W-LEDs excited by near ultraviolet chip. [ABSTRACT FROM AUTHOR]

A series of phosphors Eu3+-activated Sr 2 Nb 2 O 7 red emitting phosphors were synthesized using a solid-state method in high temperature air. The X-ray diffraction (XRD) pattern showed that the single phase was obtained and the particles illustrated a narrow size distribution of about 0.75 μm. The excitation and emission spectrum show that the phosphor can be excited under the light of 393 nm or 465 nm to emit strong red light of 615 nm. The CIE coordinates (x = 0.65, y = 0.37) of the representative red phosphor are close to pure red. The luminescence properties suggest the phosphor is a potential red emitting phosphor. [ABSTRACT FROM AUTHOR]

Cu(OH) 2 nanomaterials are widely investigated for non-enzymatic glucose sensors due to their low-cost and excellent performance. Cu(OH) 2 nanomaterials usually grow on substrates to form sensor electrodes. Reported works mainly focus on structure adjusting of the Cu(OH) 2 nanostructures, while the optimization of substrates is still lacking. In the present work, directional porous Cu (DPC) was applied as the substrate for the growth of Cu(OH) 2 nanograss (NG), and hierarchical structures of Cu(OH) 2 @DPC were prepared by alkaline oxidation. The morphology and microstructure evolution of the prepared hierarchical structures was investigated, and the non-enzymatic glucose sensing performance was evaluated. Cu(OH) 2 @DPC exhibits enhanced comprehensive non-enzymatic glucose sensing performance compared to the reported ones, which may benefit from both the effective adsorption of the Cu(OH) 2 NG with a relatively high surface area and the high solute exchange of the DPC by a channel effect. This work provides new insights into the further improvement of the non-enzymatic glucose sensing performance of Cu(OH) 2 nanostructures by optimizing the substrate structure.