We briefly review topological quantum materials, a new system of materials developed since 2005, including topological insulators, topological crystalline insulators, topological superconductors, and topological semimetals. The strong spin-orbit coupling in these materials lead to rich quantum phenomena such as quantum anomalous Hall effect, which can significantly promote the developments of new technologies such as low-energy-consuming electronics, topological quantum computation, and green energy.
Sepiolite/flower-like BiOCl nanocomposites as photocatalyst have been successfully prepared by hydrolysis precipitation method. And the influence of temperature, pH and Bi(NO3)3 concentration on the unique morphology of the nanocomposites was investigated. Moreover, the photocatalytic activity of these nanocomposites was examined for the degradation of rhodamine B. The results show that the flower-like BiOCl is uniformly dispersed on the sepiolite and this nanocomposites exhibit a photocatalytic efficiency of 14.29%-16.67% higher than that of pure BiOCl nanosheets for the degradation of rhodamine B, and the catalyst has an excellent cycling stability.
High deformability X80 pipeline steel with microstructure composed of bainite and martinsite/austenite (B+M/A) can be obtained through the coiling continuous partitioning process. Effect of coiling temperature on the microstructure evolution and mechanical performance of the (B+M/A) X80 pipeline steel was studied by means of microscopic analysis, X-ray diffraction and mechanical property tests. The results show that with the increasing coiling temperature, the strength of the steel decreases and the ductility increases because of the decrease amount of bainite and dislocation density, as well as the increase amount of retained austenite. By a high coiling temperature, both of the precipitation of carbides and the decomposition of retained austenites result in the increase of strength and the decrease of plasticity. With a process by proper coiling temperature, the produced steel with such (B+M/A) dual-phase structure may exhibit a comprehensive mechanical performance with such as lower ratio of yield to strength, higher uniform elongation and strain hardening index, which meets the technical requirements of high deformability pipeline steel.
The precipitation behavior of the strengthening precipitate Cu-rich phase at the early aging stage in 18Cr9Ni3CuNbN austenitic heat-resistant steel, which is commonly used as tubes for superheater and /or reheater at 600℃ of USC power plants, has been investigated by three dimensional atom probe (3DAP), and C curve of Cu-rich phase in 18Cr-9Ni type steel has been given. Experimental results show that the Cu-rich phase precipitates quickly at the early stage of long-term aging treatment at both 650℃ and 700℃. The Cu-rich segregation clusters quickly form and then the Cu atoms diffuse from the g-matrix into the Cu-rich segregation clusters. The atoms of Fe, Cr and Ni from Cu-rich clusters defuse outwards to the g-matrix simultaneously, finally the Cu-rich phase forms.
The lead-free bismuth layer-structured piezoelectric ceramics of SrNa0.5Bi4.5Ti5O18 + x wt.% CeO2 (SNBTCx) were prepared by solid state reaction and the effect of CeO2 on the microstructure and electrical properties of the ceramics have been investigated. The result shows that the CeO2 doping did not alter the crystallographic structure of the ceramics. There were not obvious changes in Curie temperature of the ceramics with the doping of CeO2, and all the prepared SNBTCx had high Curie points (Tc≥560oC). With the increase of CeO2 contents, the dielectric constant decreased gradually, while the dielectric loss increased firstly and then decreased. Among others, the ceramics SNBTCx with x=0.3 exhibited the best properties: Tc=567 oC, d33=29 pC/N and tanδ=0.015, besides of which the d33 value was still over 22 pC/N after annealing at 500 oC, indicating that the ceramic could be used at high temperature.
Nanostructured bainite steel with an ultimate tensile strength of 2127 MPa, elongation of 4% has been obtained by warm rolling followed with isothermal heat treatment.The effect of deformation temperature on transformation of nano bainites has been investigated. The results show that with a proper warm defromation, the time required for the transformation of the supercooled austenite into bainite can be shortened from 50 h to 20 h. The deformation rates of supercooled austenite adopted at all temperatures in the experiments can accelerate the low temperature nanobainite transformation, while the transformation rate increased with the decreasing deformation temperature. With a deformation rate above 30%, the retained austenites were sharply refined and the blocky austenites were diminished. The low temperature nano bainite transformation can be accelerated by warm rolling process without harm to the strength, thus shortening the time of heat treatment resulting in cost saving of the steel production.
A nitrogen doped nano-ZnO/PVC composite was prepared. The composite exhibits strong absorption in the ultraviolet and visible light regions according to measurement results by FT-IR and UV-visible diffuse reflectance spectroscopy. The effect of the composite on the photocatalytic degradation of methyl orange was examined. The results show that the existence of PVC in the composite can reduce the annihilation probability of electrons with cavities within ZnO, thereby broaden the spectral response range and correspondingly enhance the photocatalytic efficiency of the composite in visible light.
A new Cu-based composite Cu/Ti3SiC2/C was prepared by powder metallurgy. Then the tribological performance of the composite was examined under different sliding speeds and loads by means of a specially designed sliding apparatus. The worn surface of the composite was characterized by SEM equipped with EDS. The results show that the amount of wear loss increases linearly with the increase of the sliding distance under the condition of high speed and low load. The observation of the worn surface showed that scattered distribution of Ti3SiC2 and graphite in the Cu matrix may be responsible to the obvious enhancement of the wear property the composite. Furthermore, the worn failure of the composite may be attributed to adhesive wear, abrasive wear and oxidation wear.
Aluminum foil was anodic oxidized by a two-step anodization process in oxalic acid solutions. While the influence of processing parameters, such as voltage, time and solution concentration, for the 1st and 2nd steps of anodization process on the characteristics of pores of the anodic aluminum oxides (AAO) films was investigated. Results show that for the 1st anodization, the pores spacing increases with the rising voltage, yet the anodization time and the concentration of oxalic acid solution have almost no influence; for the 2nd anodization process, the pores spacing doesn’t change when varying the voltage, the anodization time and the concentration of solution, but the pore diameter rises greatly with the rise of the voltage. The pores of the AAOs films are well arranged in a form of hexagonal array. Furthermore, the shape of the pores changes slightly when increasing the voltage for the 2nd anodization. High concentration (up to 0.4 mol/L) oxalic acid solution for the 2nd anodization resulted in an oriented piercing of the pore’s wall, even a dissolving of the AAO layer, but the pores arrangement was not affected.
Effect of cyclic heat treatment on microstructure and mechanical properties of a Ti-V microalloyed steel was investigated. Therefore, the metallographic microstructure of the steels after heat treatment for each cycle was succesively examined and the relevant grain size was statistically determined; the cyclically heat-treated steels were also examined by means of SEM and TEM in order to reveal the microstructural evolution and the variations of average size and composition of precipitates in the steels with the increasing cycle number; while their tensile strength and toughness were measured. The results show that with the increasing cycle number, the average grain size of the steels decreases continuously. For mechanical properties, Rm has the same regularity due to the increase of mean size of the complex carbide with cycle numbers, while the AKU initially increases and thereafter decreases as a result of the joint influence of the average grain size and the proportion of proeutectoid ferrite.
Effect of linear heating aging process and the Cu content on the performance and the formation of precipitates of Al-Zn-Mg-(Cu) alloy was investigated by means of differential scanning calorimeter (DSC), hardness tester, transmission electron microscopy(TEM) and three-dimensional atom probe (3DAP). The results show that with the increase of the aging temperature the hardness rises firstly and then decreases after reaching a peak. After aging at every selected temperature of the linear heating aging treatment process, all the relevant hardness of the Al-Zn-Mg-Cu alloy is higher than that of the Al-Zn-Mg alloy. After aging at peak point by linear heating, the main precipitates are η' phase, while there exists small quantities of η phase and GP zone for the two alloys Al-Zn-Mg and Al-Zn-Mg-Cu. However the addition of Cu may induces certain change of the composition and morphology of the precipitates and delay their transition from metastable state to stable state.
