高分子材料导热性能影响因素研究进展

介绍了高分子材料导热性能影响因素研究进展，重点阐释了聚合物基体的结构特性（链结构、分子间相互作用、取向、结晶度等）、导热填料（种类、含量、形态、尺寸等）以及制备方法等对高分子材料导热性能的影响。     

基于卓越工程师教育的频率特性分析课堂教学研究

频率特性分析在工程应用中具有重要的作用,在电路分析、模拟电子技术、信号与系统、自动控制理论等相关课程中都涉及到相关章节内容,在不同课程中如何根据工程应用和学生学习阶段把握具体的讲解内容和讲解方式非常重要。本文从频率特性的求解方法和具体物理意义角度开展在不同课程中讲解的方法,从时域和频域角度分别讨论其物理意义和具体的分析方法。通过渐进深化的教学过程和教学方法不断提高学生的知识掌握和应用技能,提高学生的工程意识、工程素质和工程创新能力,强化学生对于频率特性课程知识的综合应用能力。     

Inhibited intracrystalline cracks and enhanced electrochemical properties of NCM811 cathode materials coated by EPS

The formation of micro-cracks in Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode particles is an extremely important factor affecting the electrochemical characteristics after long-term cycling. Generally, cracks can be divided into intergranular crack and intracrystalline crack according to their positions. Coating has been confirmed as a highly effective strategy to relieve intergranular cracks. However, the intracrystalline cracks of primary-like particles have rarely been studied. In this work, ethoxy functional polysiloxane (EPS) was directly coated on the surface of original NCM811 by tetraethyl orthosilicate (TEOS) hydrolytic polycondensation method without any additives. Then, the microstructure, micromorphology, surface state and electrochemical properties were investigated in detail by XRD, SEM, TEM, CV and EIS. The results displayed that the micro-cracks of primary-like particles were effectively suppressed under appropriate EPS coating. Accordingly, excellent capacity retention of 95.6% (100 cycles, 1C) and rate performance (144.6 mA h/g, 5C) were obtained. These improved mechanical and electrochemical properties are considered to be related to the EPS stress buffer layer, suppressed oxygen vacancies, inhibited phase transition and reduced volume change.     

LCD-SLA 3D printing of BaTiO3 piezoelectric ceramics

Stereolithography-based 3D printing is a promising method to produce complex shapes from piezoceramic materials. In this study, LCD-SLA 3D printing was used to create lead-free piezoceramics based on barium titanate (BaTiO₃, BT). Three types of BT powders (micron, submicron and nanoscale) were tested in LCD-SLA 3D printing, and a technique for the preparation of a ceramic slurry suitable for LCD-SLA printing has been developed. Using TGA-DSC analysis, the thermal debinding parameters to obtain crack-free samples were determined, followed by further sintering and the study of the piezoelectric properties (ε_r = 1965, d₃₃ = 200 pC/N, tan = 1,7 %). The results of the study demonstrate high potential for the production of complex piezoceramic elements that can be used in aviation, in particular, aviation radio equipment; in the marine industry for transceiver modules of hydroacoustic antennas; and in the nuclear industry for pressure control sensors in the steam–water path.     

气藏平均地层压力跟踪计算新方法

平均地层压力是产能评价和动态分析的基础，准确、快速获取平均地层压力对高效开发气藏意义重大。基于地层压力随时间变化的规律，分析了平均地层压力的变化规律。研究结果表明：平均地层压力等效点仅随时间发生改变，平均地层压力的下降速率等于或者近似等于井底流压的下降速率。从封闭弹性驱动气藏的物质平衡方程出发，考虑偏差系数和井底流压随平均地层压力的变化，推导建立了平均地层压力跟踪计算新方法，根据生产数据可迭代计算平均地层压力。方法验证结果显示，采气速度和采出程度共同影响模型的计算结果。应用实例表明，跟踪计算法与压力恢复试井和物质平衡法之间的相对误差均较小，满足工程计算精度要求，且跟踪计算法不需依托生产测试数据，节约了测试费用，避免了测试占产。     

Ab initio study of helium in Li4SiO4 crystals: Electronic properties,migration, and vacancy capture mechanism

Li₄SiO₄ crystal is a candidate material for tritium breeder material. Vacancy defects and He atoms will be produced in the crystal after neutron irradiation in fusion reactor. In previous research, we learned vacancy defects mainly include V_O⁰, V_O²⁺, and V_Li⁰, meanwhile, He atoms are easy to migrate and aggregate in the crystal. In order to understand the relationship between vacancy defects and He atoms, we use density functional theory (DFT) to study the interaction mechanism between vacancy and He atom. The results show that the local stable sites of He atoms are related to the surrounding charge distribution. V_O²⁺ and V_Li⁰ can capture interstitial He atoms, and it is difficult to escape the vacancies, thereby increasing the nucleation center of He atoms. V_O⁰ promotes the diffusion of He atoms in the interstitial space, which will cause small helium bubbles to merge more easily.     

Enhanced electromagnetic microwave absorption of Fe/C/SiCN composite ceramics targeting in integrated structure and function

The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics.     

Rational Design of Potent Inhibitors of a Metallohydrolase Using a Fragment-Based Approach

Metallohydrolases form a large group of enzymes that have fundamental importance in a broad range of biological functions. Among them, the purple acid phosphatases (PAPs) have gained attention due to their crucial role in the acquisition and use of phosphate by plants and also as a promising target for novel treatments of bone-related disorders and cancer. To date, no crystal structure of a mammalian PAP with drug-like molecules bound near the active site is available. Herein, we used a fragment-based design approach using structures of a mammalian PAP in complex with the Maybridge^TM fragment CC063346, the amino acid L-glutamine and the buffer molecule HEPES, as well as various solvent molecules to guide the design of highly potent and efficient mammalian PAP inhibitors. These inhibitors have improved aqueous solubility when compared to the clinically most promising PAP inhibitors available to date. Furthermore, drug-like fragments bound in newly discovered binding sites mapped out additional scaffolds for further inhibitor discovery, as well as scaffolds for the design of inhibitors with novel modes of action.     

Corrosion behaviour of Mg-Gd-Y-Zn-Ag alloy components with different sizes after cooling

The corrosion behaviour of Mg-6Gd-3Y-1Zn-0.3Ag (wt.%) alloy components with different sizes after cooling was investigated. The alloys in the small components (SC) cooled fast, which were composed of α-Mg matrix and coarse long-period stacking ordered (LPSO) phases. The alloys in the large components (LC) cooled slowly, and there were thin lamellar LPSO phases precipitating inside the grains, except for α-Mg matrix and coarse LPSO phases. The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample. Electrochemical impedance spectroscopy (EIS) test showed that the surface film on LC alloys provided worse protection. The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion, which accelerated the rupture of the surface film.