Effect of B4Cp content on microstructure and the high-temperature oxidation behavior of Ti-5.4Al-4.03Mo-3.93V-2.37Cr-0.01Zr composites

The paper discusses the effects of B _4 C particle (B _4 C _p ) content on the microstructure and high-temperature oxidation resistance of B _4 C _p /Ti-5.4Al-4.03Mo-3.93V-2.37Cr-0.01Zr composite prepared by powder metallurgy. The results demonstrate that grain size of the composites decreases by increasing reinforcement content from 1 to 3 wt.%, suggesting that B _4 C _p can refine grain of the materials. For the composites with increasing B _4 C _p content from 0 to 3 wt.%, the apparent porosity increase from 3.23 to 6.89%, indicating that the density of materials decreased with the increase of B _4 C _P content. In addition, the hardness of the materials have been greatly improved. Comparing to the substrate 434.02 HV, the 1, 2, and 3 wt.% B _4 C _P specimens are increased by 37.2%, 57.5%, and 84.7%, respectively. The weight of the oxidation product is reduced and the oxidation rate is slowed down, as the B _4 C _P content increases. Moreover, the thickness of the oxide layer is greatly reduced, and the thickness of oxidation layer in composites with 0, 1, 2 and 3 wt.% B4CP specimens were 60, 55, 47 and 40 μ m, indicating that B _4 C _P can improve the high-temperature oxidation resistance

Understory specific species appearances indicate the soil improvement of low-function Platycladus orientalis forest in Beijing’s mountainous areas

How to assess the effect of ecosystem restoration is a trending topic with all the restoration projects and ecosystem function studies in recent years. Although many studies have used different indicators and methods to evaluate ecosystem restoration effects, it needs a lot of site works to acquire the data. Low-function Platycladus orientalis forest restoration program in Beijing mountainous area has been started since 2002, in this study, the understory species of 92 plots were investigated and recorded. We assumed that the effect of ecosystem restoration would improve site conditions, especially for the soil conditions which might lead to the appearance of new species. The relationship between understory species and eleven site condition factors was elucidated by means of canonical correspondence analysis (CCA), further, specific species were chosen to represent the improvement and possible growth areas of specific species was predicted by Maximum Entropy model. Results shown that Spiraea pubescens, Deutzia parviflora, Chrysanthemum chanetii, Themeda triandra, Oplismenus undulatifolius were the main understory species which were sensitive to environmental factors, and their distribution were related to soil factors closely. The species of Spiraea pubescens, Chrysanthemum chanetii, Oplismenus undulatifolius had strong indication to soil nutrient, the appearances would happen when the comprehensive index of soil nutrient was above 81,64 and 61 respectively. The appearance of Chrysanthemum chanetii and Oplismenus undulatifolius would indicate that the soil nutrient level was in or above the range of medium, and the appearance of Spiraea pubescens would mean that the soil nutrient level was in or above the range of high in low-function Platycladus orientalis forest of Beijing mountainous area. Our study indicates that the specific species could as an indicator to reflect or evaluate the ecosystem restoration effect

Rare-earth based intermetallic triangular lattice antiferromagnets REZn3_3As3_3: Crystal growth and physical properties

Inspired by the recent extensive investigations of the ground-state magnetic properties in the rare-earth based triangular lattice antiferromagnet YbMgGaO$_4$ and the related insulating oxide compounds, we have recently carried out the single-crystal growth of the rare-earth based triangular lattice intermetallic compounds REZn$_3$As$_3$ (RE=Ce, Nd, Pr). These materials are strongly frustrated two-dimensional antiferromagnets with the rare-earth ions forming triangular lattice layers. Our studies of the physical properties of the grown high-quality single-crystal samples, including X-ray diffraction, low-temperature heat capacity and magnetic susceptibility measurements etc., have suggested complex magnetic ground states for the studied compounds, likely due to the interplay between geometric frustration, Kondo coupling and RKKY interactions. Further investigations via neutron scattering have been planned