纳米金属多层膜的微结构热稳定性研究

介绍了纳米金属多层膜的微结构热稳定性的实验和相关的理论基础及模拟计算，探讨了实验及模拟的发展前景，综述了纳米金属多层膜的微结构热稳定性研究的现状和发展趋势。

基于流变学法探究植被恢复下土壤力学稳定性

[目的]为探究黄土高原植被恢复过程中土壤微结构稳定性的演变规律。[方法]选取子午岭林区4个不同植被演替阶段的土壤为研究对象,通过流变学方法振幅扫描测试方式测定不同基质势(0,-3,-10 kPa)下土壤抗剪切强度参数和黏弹性参数,并分析其与土壤理化性质之间的关系。[结果](1)土壤抗剪切强度和黏弹性随植被演替阶段的增加而增加,主要是由于植被恢复过程中土壤有机碳、交换性Ca^(2+)、砂粒质量分数增加和Na^(+)下降提高土壤颗粒间的黏附力和摩擦力。(2)土壤抗剪切强度参数随基质势的降低而增加,在低基质势条件下,土壤抗剪切强度参数(G′_(LVE)、τ_(LVE)和τ_(max))与交换性Ca^(2+)、砂粒质量分数相关性不显著,而在高基质势条件下,土壤抗剪切强度参数与交换性Ca^(2+)呈显著正相关(p<0.05),τ_(max)、G′_(LVE)、τ_(YP)和G′_(YP)均与砂粒质量分数呈显著正相关。(3)土壤黏弹性参数(γ_(YP)和I_(Z))随基质势的降低而降低;高基质势条件下土壤黏弹性参数与有机碳呈正相关,且随着基质势的降低,相关性逐渐减弱;不同基质势下黏弹性参数均与黏粒质量分数呈显著负相关。(4)土壤整体力学稳定性在0 kPa时与土壤Ca^(2+)呈正相关,-3 kPa时与土壤粉粒、K^(+)呈负相关,-10 kPa时与黏粒质量分数呈正相关关系。[结论]研究结果揭示土壤在不同植被类型不同基质势下的力学稳定性变化规律及影响机制,为理解黄土高原植被恢复过程中土壤特性的演变提供重要依据,也为未来的土壤保护和生态恢复工作提供理论支撑。

Structure and properties of FeCoNiCrCu_(0.5)Al_x high-entropy alloy

Effects of Al content and heat treatment on the structure,hardness and electrochemical properties of FeCoNiCrCu0.5Alx high-entropy alloys were investigated.The phase structure of as-cast alloys evolves from FCC phase to BCC phase with the increase of Al content.The stable phase of FeCoNiCrCu0.5Alx high-entropy alloys will transform from FCC phase to FCC＋BCC duplex phases when x value increases from 0.5 to 1.5.The hardness of BCC phase is higher than that of FCC phase,and the corrosion resistance of BCC phase is better than FCC phase in chlorine ion and acid medium.High hardness and good corrosion resistance can be obtained in as-cast FeCoNiCrCu0.5Al1.0 alloy.

Instability mechanism and control technology of soft rock roadway affected by mining and high confined water

Based on deformation and failure characteristics of the second belt conveyor roadway at level II of Zhuxianzhuang coal mine, laboratory experiments, numerical calculation and field test were adopted to analyze the composition and microstructure of mudstone, the law of mudstone hydration and its strength weakening induced by water, the characteristics of surrounding rock deformation and failure under the action of confined water. Results showed that montmorillonite clay minerals accounted for as much as 76% of mudstone, with a large number of pores existing in the microstructure. Besides, as the molecular structure of montmorillonite changed, mudstone microstructure damage occurred with the macroscopic manifestation of its theological instability. Weakening degree of confined water on residual strength of mudstone was almost 50%. The instability mechanism of soft rock roadway caused by high confined water is that surrounding rock circulates the process of ＂fracture-seepage-mud ding-closed＂ twice, which weakens its strength and leads to roadway instability. A combined support technology, namely the, ＂high-toughness sealing layer ＋ hollow grouting cables ＋ full-length anchoring bolts with deep borehole＂ was proposed. Based on field observation, the soft rock roadway was controlled effectively, which also verified the effectiveness of new control technology for surrounding rock.

Microstructure and mechanical properties of ZA62 based magnesium alloys with calcium addition

As-cast microstructure and mechanical properties of Mg-6Zn-2Al-0.3Mn (ZA62) alloys with calcium addition were investigated.The as-cast microstructure of the base alloy ZA62 consists of the α-Mg matrix and eutectic phase Mg51Zn20.The Mg51Zn20 eutectic was gradually replaced by MgZn phase and Mg32(Al,Zn)49 phase when calcium is added into the base alloy.Further addition of calcium leads to the increase of grain boundary phases and formation of a new quaternary Mg-Zn-Al-Ca eutectic compound.In comparison with the base alloy,the increase of calcium addition to the base alloy results in the reduction of both strength and ductility at ambient temperature,but increase at elevated temperatures due to the thermal stability of Ca-containing phases.At elevated temperatures,the creep resistance of ZA62 based alloys containing calcium is significantly higher than that of AZ91 which is the most commonly used magnesium alloy.

Stability of thin films of microcrystalline silicon under ligh tsoaking

Silicon thin films with different crystalline ratio(Xc) have been deposited by varying silane content(SC) of reactive gases in the RF-PECVD process.The effects of silane content on performance of the materials and the relationship between microstructure and opto-electronic properties were studied by means of Raman measurements,photoconductivity(σ_ ph ),and dark conductivity(σ_d),followed by the measurements of light absorption coefficient(α),the product of quantum efficiency,mobility and lifetime (ημτ),before,during and after light soaking,respectively.The results indicate that the microcrystalline silicon near the transition region is suitable to prepare microcrystalline silicon of device grade,and that the amorphous region of the material is responsible to the light induced degradation.

Stable Solution of Nonlinear Age-structured Forest Evolution System

This paper studies the dynamical behavior of a class of total area dependent nonlinear age-structured forest evolution model. We give the problem of equal value for the forest system, and discuss the stable solution of system. We obtained the necessary and sufficient conditions for there exists the stable solution.

Enlarged interlayer spacing and enhanced capacitive behavior of a carbon anode for superior potassium storage

Potassium-ion batteries(PIBs) hold great potential as an alternative to lithium-ion batteries due to the abundant reserves of potassium and similar redox potentials of K+/K and Li+/Li. Unfortunately, PIBs with carbonaceous electrodes present sluggish kinetics, resulting in unsatisfactory cycling stability and poor rate capability. Herein, we demonstrate that the synergistic effects of the enlarged interlayer spacing and enhanced capacitive behavior induced by the co-doping of nitrogen and sulfur atoms into a carbon structure(NSC) can improve its potassium storage capability. Based on the capacitive contribution calculations, electrochemical impedance spectroscopy, the galvanostatic intermittent titration technique, and density functional theory results, the NSC electrode is found to exhibit favorable electronic conductivity,enhanced capacitive adsorption behavior, and fast K+ ion diffusion kinetics. Additionally, a series of exsitu characterizations demonstrate that NSC exhibits superior structural stability during the(de)potassiation process. As a result, NSC displays a high reversible capacity of 302.8 mAh g-1 at 0.1 Ag-1 and a stable capacity of 105.2 m Ahg-1 even at 2 Ag-1 after 600 cycles. This work may offer new insight into the effects of the heteroatom doping of carbon materials on their potassium storage properties and facilitate their application in PIBs.

Crystal structure of histidine-containing phosphocarrier protein from Thermoanaerobacter tengcongensis MB4 and the implications for thermostability

Protein thermostability is an inherent characteristic of proteins from thermophilic microorganisms,and therefore enables these organisms to survive at extreme temperatures.Although it is well-known that thermostable proteins are critical for the growth of thermophilic organisms,the structural basis of protein thermostability is not yet fully understood.The histidine-containing phosphocarrier (HPr) protein,a phosphate shuttle protein in the phosphoenolpyruvate-dependent sugar transport system (PTS) of bacterial species,is an ideal model for investigating protein thermostability with respect to its small size and deficiency in disulphide bonds or cofactors.In this study,the HPr protein from Thermoanaerobacter tengcongensis (TtHPr) is cloned and purified.Crystal structure with good quality has been determined at 2.3 resolution,which provides a firm foundation for exploring the thermostable mechanism.However,it shows that the crystal structure is conserved and no clue can be obtained from this single structure.Furthermore,detailed comparison of sequence and structure with the homologs from mesoor thermophilic bacteria shows no obvious rule for thermostability,but the extra salt-bridge existing only in thermophilic bacteria might be a better explanation for thermostability of HPr.Thus,mutations are performed to interrupt the salt-bridge in HPrs in thermophilic bacteria.Using site-directed mutations and the circular dichroism method,thermostability is evaluated,and the mutational variations are shown to have a faster denaturing rate than for wild-type viruses,indicating that mutations cause instability in the HPrs.Understanding the higher-temperature resistance of thermophilic and hyperthermophilic proteins is essential to studies on protein folding and stability,and is critical in engineering efficient enzymes that can work at a high temperature.