High-entropy titanate pyrochlore as newly low-thermal conductivity ceramics

Low-thermal conductivity ceramics play an indispensable role in maximizing the efficiency and durability of hot end components. Pyrochlore, particularly zirconate pyrochlore, is currently a highly promising and widely studied candidate for its extremely low thermal conductivity. However, there are still few pyrochlores that offer both stiffness, insulation, and good thermal expansion properties. In this work, the solidification method was innovatively introduced into the preparation of titanate pyrochlore, and combined it with the compositional design of high-entropy. Through careful composition design and solidification control, the high-density and uniform elements distributed high-entropy titanate pyrochlore ceramics were successfully prepared. These samples possess high hardness (15.88 GPa) and Young’s modulus (295.5 GPa), low thermal conductivity (0.947 W·m^?1·K^?1), excellent thermal expansion coefficient (11.6 ×10^?6/K) and an exquisite balance between stiffness and insulation (E/κ, 312.1 GPa·W^?1·m·K), in which the E/κ exhibits the highest value among the current reported works.     

Shock/expansion fan interaction with real gas effects for Earth and Mars atmospheric conditions

Numerical simulations are performed to investigate the real gas effects on shock/expansion fan interaction. Initial perfect gas simulations at low enthalpy capture the flow structures efficiently and outcomes are found to have excellent agreement with the analytical calculations. Furthermore, the simulations with the real gas solver for different enthalpies showed that the variation in enthalpy significantly changes the flow structures. It is observed that an increase in enthalpy leads to a decrease and increase in the postshock and postexpansion fan Mach numbers, respectively. Another important observation is the decrement in the peak pressure ratio with an increment in the enthalpy. These effects are noted to be more pronounced for Mars's environment due to the higher dependency of specific heat on temperature.     

Effects of structural parameters on water film properties of transpiring wall reactor

Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone.     

煤峪口矿81010工作面煤层底板裂隙发育特征及防治

针对煤炭开采过程中出现的突水事故,采用RFPA数值模拟软件建立采动模型,对底板裂隙破断过程和声发射进行模拟,研究煤层底板采动裂隙扩展突水通道,结果表明:离断层越近,断层内水压导升高度越高,断层出现活化,裂隙扩展发育,最终贯通形成导水通道,在进行注浆改造后,单个钻孔的最大涌水量为8 m³/h,说明注浆加固防治水效果较好,能确保工作面的安全回采。     

缺水传感器改进设计

针对一种煤矿用本安型缺水传感器在现场安装及维护难度大,以及抽采泵供水状态下管道内有水但传感器检测显示为无水,或抽采泵停止工作时传感器检测显示有水问题,分析原产品中磁体及探头感应装置结构。改进其结构形式,并优化安装,使检测稳定可靠。实现抽采泵管道用缺水传感器的可靠性设计和轻量化设计。     

Quantification of Dendritic Spines Remodeling under Physiological Stimuli and in Pathological Conditions

Numerous brain diseases are associated with abnormalities in morphology and density of dendritic spines, small membranous protrusions whose structural geometry correlates with the strength of synaptic connections. Thus, the quantitative analysis of dendritic spines remodeling in microscopic images is one of the key elements towards understanding mechanisms of structural neuronal plasticity and bases of brain pathology. In the following article, we review experimental approaches designed to assess quantitative features of dendritic spines under physiological stimuli and in pathological conditions. We compare various methodological pipelines of biological models, sample preparation, data analysis, image acquisition, sample size, and statistical analysis. The methodology and results of relevant experiments are systematically summarized in a tabular form. In particular, we focus on quantitative data regarding the number of animals, cells, dendritic spines, types of studied parameters, size of observed changes, and their statistical significance.     

Influence of temperature on acoustic emission source location accuracy in underground structure

An acoustic emission (AE) experiment was carried out to explore the AE location accuracy influenced by temperature. A hollow hemispherical specimen was used to simulate common underground structures. In the process of heating with the flame, the pulse signal of constant frequency was stimulated as an AE source. Then AE signals received by each sensor were collected and used for comparing localization accuracy at different temperatures. Results show that location errors of AE keep the same phenomenon in the early and middle heating stages. In the later stage of heating, location errors of AE increase sharply due to the appearance of cracks. This provides some beneficial suggestions on decreasing location errors of structural cracks caused by temperature and improves the ability of underground structure disaster prevention and control.     

Structure,mechanical and thermal properties of Y-doped CrAlN coatings

CrAlYN coatings with different Y contents (0, 5 and 12 at.%) were deposited by cathodic arc evaporation to investigate the influence of Y-addition on the structure, mechanical and thermal properties of CrAlN coatings by using X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermal gravimetric analysis and nanoindentation. The structural transformation of single phase cubic Cr_0.42Al_0.58N and Cr_0.39Al_0.56Y_0.05N coatings to cubic–wurtzite mixed Cr_0.32Al_0.56Y_0.12N coating leads to a drop in hardness from (30.2±0.7) GPa of Cr_0.42Al_0.58N and (32.0±1.0) GPa of Cr_0.39Al_0.56Y_0.05N to (25.2±0.7) GPa of Cr_0.32Al_0.56Y_0.12N. The incorporation of 5 at.% Y retards the thermal decomposition of CrAlN, verified by the postponed precipitation of w-AlN and N-loss upon annealing. Correspondingly, Cr_0.39Al_0.56Y_0.05N coating consistently exhibits the highest hardness value during thermal annealing. Nevertheless, alloying with Y exerts an adverse effect on the oxidation resistance of CrAlN.     

The origin of interfacial delamination in Au/ceramic cofired LTCC structure

The interfacial delamination of electrode/ceramic multilayer structure will seriously damage the reliability of low temperature co-fired ceramic (LTCC) module in practical applications. In this work, three kinds of glasses employed in Au electrode are designed and prepared to study the abnormal expansion and delamination process in the Au/ceramic LTCC multilayer structure. The interfacial delamination in the co-fired structure is found to be attributed to the abnormal expansion of glass in respect to Au electrode at high temperature, which is originated from the enlarged closed pores during the co-firing process. This conclusion is further confirmed by co-firing the sample in a low-pressure condition. The mechanism and elimination of interfacial delamination here provides a feasible solution for the design of novel glasses in Au electrode for LTCC applications.