关键词： C/SiC-MoSi_(2)复合材料   微结构   力学行为  

摘要： 以三维针刺碳毡作为预制体,先采用树脂单向加压浸渍-热解工艺制备出C/C多孔体,然后采用反应熔体浸渗法将Si-Mo合金浸渗到C/C多孔体中制备C/SiC-MoSi_(2)复合材料。对C/SiC-MoSi_(2)复合材料的物相组成、显微结构以及力学性能进行了研究。结果表明,该复合材料由C、SiC、MoSi_(2)和Si组成;生成的SiC和MoSi_(2)分布在纤维束间和胎网层,Si-Mo合金并未渗入纤维束内部,束内碳纤维未受损伤;残余Si含量仅为4.2%,且被分散成小块。C/SiC-MoSi_(2)复合材料的弯曲断裂行为可分为三个阶段,从材料的断口形貌中可以观察到纤维的脱粘拔出、基体的台阶状断裂以及裂纹偏转和分叉,表明该复合材料呈现出塑性断裂特征。

关键词： Laser manufacturing   Recast zone   Microstructural characterization   Indentation   Fatigue performance  

摘要： Laser manufacturing is widely used in modern industries for its high efficiency and accuracy. In the present work, the microstructures and mechanical properties of the laser-induced recast material on nickel-based superalloy Inconel 718 were systematically investigated. The mechanical property of the recast material was investigated with the help of the instrumented indentation technique improved by the reverse analysis algorithm. The yield strength and microhardness in the recast zone are much lower than that of the base material, which is attributed to the epitaxial growth of columnar grains and more to the decrease of strengthening phases gamma' and gamma ''. Whereas the recast-affected zone reveals higher yield strength for the growth of strengthening twins, the partial dissolution of the delta phase and cold work hardening manifested by higher misorientations. The high cycle fatigue performance of the recast material reduces significantly, which is caused by microstructural changes and defects including interval cavities and surface micro-cracks distributed in the recast zone.

关键词： 热防护系统   三维随机纤维材料   微结构设计   有限元模型   几何参数  

摘要： 为研究三维随机纤维材料服役环境下的力学性能,提高热防护系统安全服役性能和结构寿命。利用有限元建模软件,建立三维随机纤维材料微结构模型,研究其面内和厚度两个方向的三维随机纤维材料宏观力学性能与几何参数(纤维方向、纤维长度和纤维直径)的关系,获得了三维随机纤维材料厚度和面内宏观力学性能演化规律。结果表明:三维随机纤维材料内部偏移纤维比重越大,厚度方向压缩强度就越高,面内方向压缩强度就越低;压缩强度随纤维长度增加呈上升趋势,在0.9 mm左右时达到临界值;压缩强度随纤维直径增加呈下降趋势。该研究结果可为三维随机纤维材料制备提供理论基础。

关键词： 硫铝酸盐   注浆材料   应力模拟装置   微结构   强度增强机理  

摘要： 在煤矿千米深井巷道注浆加固示范工程中,注浆结石体抗压强度常高于常压下的抗压强度,针对此问题,采用自制加压装置模拟应力作用对注浆材料浆液进行加压预养护,通过测试试样强度、表观密度、孔隙率、水化产物种类和微观结构,分析应力对材料强度增强的作用机理。结果表明:10 MPa的应力可以显著提高注浆材料结石体的抗折、抗压强度,抗折强度最大增加24.3%,抗压强度最大提高21.6%;应力可促进早期钙矾石的生成且不改变水化产物种类,提高结石体密度。分析认为,应力通过促进钙矾石的生成速率,降低结石体孔隙率和最可几孔径的方式提高结石体的强度,即提高结石体的密度,增加钙矾石相互搭接的紧密程度,进而提高注浆材料结石体的抗折、抗压强度。检测结石体密度在某种意义上可以评估注浆加固的加固效果。

关键词： 玄武岩玻璃   生物蚀变微结构   遗迹化石   海洋深地生物圈  

摘要： 玄武岩玻璃中的生物蚀变微结构为微生物摄取玄武岩玻璃中营养成分,通过新陈代谢产生有机酸溶解玄武岩玻璃而形成的微米级孔洞或钻穴。生物蚀变微结构在现代海洋洋壳及代表古老洋壳残片的蛇绿岩和绿岩带中广泛存在。研究玄武岩玻璃中蚀变微结构的形态特征、形成机制及其时空分布,不仅对探索地球早期生命起源和演化具有重要启示意义,也为研究海洋深地生物圈的微生物组成及其时空演化提供了新材料。形态学上,生物蚀变微结构分为颗粒和管状微结构。某些非生物成因微结构与生物蚀变微结构相似,识别生物蚀变微结构还需结合元素、同位素地球化学、有机质及DNA检测等方面研究手段。对全球玄武岩中生物蚀变微结构的时空分布总结表明其在地质历史时期普遍存在,并在洋壳垂向分布上可能密切受控于岩石的孔隙度和渗透率。不同海底环境,如氧化还原条件、酸碱度、深度、温度及孔隙度等都会影响微生物群落及其代谢方式,从而形成不同类型的生物蚀变微结构。具体哪些因素对玄武岩玻璃中生物蚀变微结构起主要控制作用还需进一步探索。

关键词： 液晶显示   扩展光源   分段加权叠加   表面微结构   视角偏转  

摘要： 为了使应用于驾驶舱内的液晶显示器满足观看者的特殊视角要求,设计了一种能够将液晶显示器的最大亮度由正视方向根据观看者的位置偏转到特定方向的光学膜。本文基于扩展光源进行设计,根据扩展光源上不同位置的光线到达微结构的能量不同,提出了分段加权叠加的方法设计出微结构面型。仿真结果表明:水平视角不变,垂直视角偏转-15°,光线透过率为84.7%,半亮度视角范围为(-38.4°,4.4°)。采用无掩膜直写光刻工艺制作了实际样品并进行了效果测试,测试结果表明:和传统的背光视角相比,垂直方向的最大亮度由原来的0°偏转到-16°,半亮度视角由(-23.8°,27.4°)变为(-43°,9.4°),透过率为83.0%,同时满足视角偏转和亮度的要求。

关键词： Cermets   Ti(C   N)   Alternative binders   Phase diagram simulation   High-temperature XRD  

摘要： In this investigation, Ti(C,N)-FeNiCr systems were designed using Thermo-Calc? software. Materials were processed by conventional powder metallurgy, employing different carbon additions to study a wide range of the phase diagram as well as the effect of C in the sintered samples. Specimens were extensively characterised in terms of density, magnetic and mechanical properties, and microstructural features. Simulation approach was validated by means of Differential Thermal Analysis (DTA) and High-Temperature X-Ray Diffraction (HT-XRD), from room temperature up to 1200 ?C for each composition, comparing phases obtained for each temperature and composition with predicted ones. Results showed excellent consonance between Thermo-Calc? and XRD phases, except for precipitation of secondary carbides, which appeared in the simulation but not in the sintered samples. Moreover, variation of C content demonstrated to have a direct effect in the microstructural homogenization of the final specimens.

关键词： Damage   Deformation   In-situ SEM nanoindentation   Microstructure   Zirconia  

摘要： Development of optimal shaping processes for pre-sintered and sintered zirconia materials requires a fundamental understanding of damage and deformation mechanisms at small-scale contacts with diamond tools. This paper reports on responses of zirconia materials with distinct microstructures to nanoindentation associated with diamond machining using a Berkovich diamond indenter. In-situ nanoindentation was performed in a scanning electron microscope (SEM) and in-process filmed to record small contact events. Indentation morphology was SEM-mapped at high-magnifications. Although both pre-sintered porous and sintered dense zirconia materials mechanically revealed the quasi-plastic behavior in indentation, there were distinct responses of the two materials to quasi-plasticity at the microstructural level. For pre-sintered porous zirconia, the quasi-plasticity was attributed to shear faults resulting from breaking pore networks as microstructurally discrete interfaces, to lead to compression, fragmentation, pulverization and microcracking of zirconia crystals in indentation imprints. In contrast, sintered dense zirconia had shear band-induced quasi-plastic deformation, accompanied with localized tensile microfracture. A material index associated with the mechanical properties ranked the lower quasiplasticity for pre-sintered porous zirconia than its sintered dense state, predicting more machining-induced damage in the former than the latter. Significantly higher indentation imprint volumes induced in indented pre-sintered porous zirconia than sintered dense state previses higher machining efficiency for the former than the latter. The microstructure-dependent indentation mechanisms provide the fundamental knowledge into micromechanics of abrasive machining of zirconia materials and may lead to a new microstructural design for zirconia materials to achieve a balanced machining efficiency and damage control.

关键词： 热电材料   微波湿化学方法   全尺度分等级结构   Te  

摘要： 采用简易高效的微波湿化学方法合成了包括纤维状、棒状、花束状等多尺度Te纳米结构材料。系统地研究了NaOH、PVP的加入量及溶剂EG/EN体积比对Te微观结构形貌的调控及影响作用。该制备工艺操作简单、反应温和且节能环保,除可实现Te纳米结构材料的大规模生产外还对其他纳米级构件的制备起到指导意义。

关键词： Metadata  

摘要： Porous energy materials are essential components of many energy devices and systems, the development of which have been long plagued by two main challenges. The first is the 'curse of dimensionality', i.e. the complex structure-property relationships of energy materials are largely determined by a high-dimensional parameter space. The second challenge is the low efficiency of optimisation/discovery techniques for new energy materials. Digitalisation of porous energy materials is currently being considered as one of the most promising solutions to tackle these issues by transforming all material information into the digital space using reconstruction and imaging data and fusing this with various computational methods. With the help of material digitalisation, the rapid characterisation, the prediction of properties, and the autonomous optimisation of new energy materials can be achieved by using advanced mathematical algorithms. In this paper, we review the evolution of these computational and digital approaches and their typical applications in studying various porous energy materials and devices. Particularly, we address the recent progress of artificial intelligence (AI) in porous energy materials and highlight the successful application of several deep learning methods in microstructural reconstruction and generation, property prediction, and the performance optimisation of energy materials in service. We also provide a perspective on the potential of deep learning methods in achieving autonomous optimisation and discovery of new porous energy materials based on advanced computational modelling and AI techniques.