Ba-based complex perovskite ceramics with superior energy storage characteristics

Linear dielectrics are widely used to create high power capacitors, where it is a big challenge to achieve high energy storage density in such dielectrics. Here, Ba-based complex perovskite ceramics with high dielectric strength, medium dielectric constant, and ultra-low dielectric loss are proposed as the candidates for high energy storage density dielectric materials, and the significant effects of 1:2 B-site ordering and ordering domain structure are systematically investigated. In Ba(Mg_1/3Nb_2/3)O₃ ceramics, high dielectric strength of 1452 kV cm⁻¹ combined with high energy storage density of 3.31 J cm⁻³ are achieved in the samples after post-densification annealing, and they are 28% and 57%, respectively, higher than those in the as-sintered samples. The significant enhancement of energy storage performance could be attributed to the increased B-site ordering degree, and the uniform ordering domain structure. Furthermore, amorphous alumina thin films are introduced as the charge blocking layers, which significantly enhance the energy storage density to 5.09 J cm⁻³. The present work provides a new approach to develop the dielectric ceramics with high energy storage density.     

From bulk to porous structures: Tailoring monoclinic SrAl2Si2O8 ceramic by geopolymer precursor technique

In this paper, monoclinic SrAl₂Si₂O₈ ceramics with porous structures were prepared based on ion-exchanged geopolymer precursor technique. Micron-level pores with a homogeneous pore-size distribution were introduced into the inorganic framework using foaming agents. The results demonstrated that the apparent density, pore-size distribution and specific surface area of porous geopolymer precursors can be well-engineered via tailoring the category and concentration of the foaming agent. After being treated at 900°C, hexagonal SrAl₂Si₂O₈ first-crystallized from the amorphous geopolymer matrix and then gradually converted into monoclinic SrAl₂Si₂O₈ between 1100°C and 1200°C. The resulting monoclinic SrAl₂Si₂O₈ ceramics maintained the porous structures during high-temperature treatments and exhibited high porosity, specific surface area, and compressive strength. The aforementioned strategy not only achieves monoclinic SrAl₂Si₂O₈ ceramics with well-defined and robust microstructures, but also provides an alternative route to prepare other porous ceramics, with potential applications in fields of high-temperature filters, adsorbents, and heterogeneous catalysis.     

Simultaneous improvement of thermal conductivity and mechanical properties for mechanically mixed ABS/h-BN composites by using small amounts of hyperbranched polymer additives

Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester-based hyperbranched polymer (HBP) avoided the trade-off in mechanically mixed ABS/hexagonal boron nitride (h-BN) composites. After adding 0.5 wt% HBP, the maximum h-BN content in the composites increased from 50 to 60 wt%. The out-of-plane, in-plane thermal conductivity, and tensile strength of ABS/h-BN with 50 wt% h-BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h-BN/HBP with 60 wt% h-BN. The morphological and rheological results proved that these enhancements are due to the improved h-BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic-based TIMs.     

谈计算机信息网络系统的防雷

本文简要介绍了雷击的成因、种类,以及防雷原理,并特别针对计算机信息网络的防雷进行初步探讨。     

高密度电阻率法在工程勘察中的应用

从高密度电阻率法的基本原理出发,结合野外数据采集过程中装置形式的选择、极距的确定和数据质量的保证措施,以及资料处理解释过程,可看出高密度电阻率明显地优于其它直流电法。结合高密度电阻率法在工程勘察中的实例,验证了高密度电阻率法在工程勘察中的可行性、有效性和实用性。     

座椅悬架CAD系统中数据库的设计

阐述了为座椅悬架CAD系统建立专门管理图形库的数据库的必要性。介绍了数据库的设计思想和设计过程,利用VB编制了接口程序,以实现数据库和图形库的数据交换。数据库的设计方法方便并加快参数化绘图,完善了座椅悬架CAD系统,使之成为一个完整的软件包。     

水平一阶导数在航磁圈定断裂中的应用

对于区域磁场任意水平方向求一阶导数,相当于这个方向两侧边缘磁性体产生的磁异常,因此可以突出垂直于这个方向上的磁异常,使沿垂直此方向展布的断裂有明显的反映.该文对该方法进行了理论模型的分析研究,并通过实例证明了该方法在增强断裂磁场特征及准确划定断裂位置方面具有明显的效果.     

型钢混凝土受弯梁力学性能分析

型钢混凝土（SRC）结构由于其在大跨、重载结构中表现出来的良好受力性能以及在地震中表现出来的优良延性,已在工程实践中得到越来越广泛地应用。但是其计算理论多采用简单叠加或RC结构计算模式,这多少限制了其发展。为了了解SRC结构各组成材料受力性能及相互作用,本文对6根SRC梁进行了受弯载荷试验,并对其试验现象进行了分析,最后在此基础上依据混凝土、钢筋及型钢在不同位置处的实测应变变化情况,详细分析了SRC梁整个加载过程的力学性能。     

Process optimization of a closed-chamber distillation system for the recovery of FLiNaK molten salt

Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel. A closed-chamber disti...     

生产碳纤维的关键设备——碳化炉

具有耐热梯型结构的有机预氧丝经过高温热处理转化为含碳量在92%以上的无机碳纤维。实现这一转化的关键设备是碳化炉。工程实践与研究表明:其核心技术是宽口碳化炉及其配套的迷宫密封、废气排除和牵伸系统。对于ht级碳纤维生产线,炉口宽度需在1m以上,而且要正压操作,就需非接触式迷宫密封装置;为使热解废气不污染纤维,排除系统要畅通而瞬时排出;牵伸系统则是制造高性能碳纤维重要手段。