关键词： 疲劳损伤演化   四维显微成像   原位表征   同步辐射光源   增材制造  

摘要： 具备高时空分辨率的同步辐射光源是标志着现代基础科学核心创新能力的一种大科学装置。介绍了基于高能X射线三维成像的原位加载装置的国内外研究进展,简要论述了作者团队自2011年以来基于上海同步辐射光源和北京同步辐射装置自主研制的系列原位加载装置,包括原位拉伸、压缩、低周疲劳、高周疲劳、超高周疲劳试验机及其样品环境,以及针对轻质高强材料(激光焊接铝合金和激光增材制造铝、钛合金等)缺陷安全性评定开展的研究工作。结果表明,原位加载装置是表征先进材料微结构损伤演化的核心,也是关系国家竞争力的大科学装置的重要支撑。

关键词： Electric fields  

摘要： The electric-field-induced and temperature induced dynamics of domains, defects, and phases play an important role in determining the macroscopic functional response of ferroelectric and piezoelectric materials. However, distinguishing and quantifying these phenomena remains a persistent challenge that inhibits our understanding of the fundamental structure-property relationships. In situ dark field x-ray microscopy is a new experimental technique for the real space mapping of lattice strain and orientation in bulk materials. In this paper, we describe an apparatus and methodology for conducting in situ studies of thermally and electrically induced structural dynamics and demonstrate their use on ferroelectric BaTiO3 single crystals. The stable temperature and electric field apparatus enables simultaneous control of electric fields up to approximate to 2 kV/mm at temperatures up to 200 degrees C with a stability of Delta T = +/- 0.01 K and a ramp rate of up to 0.5 K/min. This capability facilitates studies of critical phenomena, such as phase transitions, which we observe via the microstructural change occurring during the electric-field-induced cubic to tetragonal phase transition in BaTiO3 at its Curie temperature. With such systematic control, we show how the growth of the polar phase front and its associated ferroelastic domains fall along unexpected directions and, after several cycles of electric field application, result in a non-reversible lattice strain at the electrode-crystal interface. These capabilities pave the way for new insights into the temperature and electric field dependent electromechanical transitions and the critical influence of subtle defects and interfaces.

关键词： Sound absorbable materials   Porous structure   Microstructural analysis   Natural fiber   Aluminum powder  

摘要： As transportation on roads and railways has become an essential means enabling the development of cities, residents living near roads and railways face undesirable noise pollution. To reduce this noise pollution, sound absorbable porous cement-based materials have great potential in terms of high sound absorption ability at a wide frequency range. Because sound absorption performance is primarily related to pore characteristics, this study mainly focuses on the development and evaluation of highly porous structures in cement-based materials by incorporating natural fibers and aluminum powder. The fresh and hardened properties of porous cement-based materials are investigated with respect to workability, compressive strength, and water absorption capacity. Furthermore, the porous network in the materials is characterized by microstructural observation using an optical microscope and X-ray computed tomography. A sound absorption test is also conducted to highlight the influences of the material porosity on sound absorption performance. Experimental results indicate that a combination of natural fibers and aluminum powder has a synergistic effect for forming highly porous structures that improve sound absorption performance. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： 国家重点实验室   高性能陶瓷   重大科研项目   综合竞争力   无机材料   国家重大需求   原国家计委   中国科学院  

摘要： 为促进我国高性能陶瓷的研究和发展,扩大我国在该领域中的影响,1988年4月,经原国家计委和中国科学院批准,在中国科学院上海硅酸盐研究所建立高性能陶瓷和超微结构开放实验室;1991年纳入国家重点实验室序列,更名为高性能陶瓷和超微结构国家重点实验室。实验室充分发挥在无机材料设计、制备、工程应用方面的基础和优势,积极承担国家重大科研项目,面向国家重大需求和无机材料学科前沿取得了一系列创新成果,科研综合竞争力得到持续提升。

关键词： 位置精度   疲劳断口   金属材料   大科学装置   微结构损伤   破坏行为   疲劳损伤   点光源  

摘要： 长期以来,科学家通过测量表面裂纹长度和辨识疲劳断口揭示小试件的破坏行为,并依此来表征大块金属材料的疲劳损伤机制,从而建立了工程结构抗疲劳断裂设计的科学基础和评价体系。虽然断口保存了材料破坏过程的全部信息,但很难标定缺陷的空间形貌及与其他缺陷的耦合情况,无法提取到三维空间中真实临界缺陷尺寸。低通量点光源工业CT探测的缺陷形貌、尺寸及位置精度不足,尤其不能实现高时空分辨下的动态原位加载。

关键词： CdS-TiO2 nano-particle   Microstructure   Photo-luminescence property   Optical properties  

摘要： In the present work, we elaborated the CdS-TiO2 (CSTO) composite materials and considered their micro-structural and optical properties were investigated. The micro-structure and optical properties were examined by TEM, XRD, absorption and PL. The particles dimensions of composite have been varied from 18 to 22 nm while the typical crystalline size of TiO2 sample materials was varied involving the 9 nm and 14 nm. The direct band-gap of TiO2 nano-particles is 3.33 eV and E-g of CSTO sample is enlarged to 3.31 eV. The TEM show the existence of the CdS could efficiently hibit the agglomeration of the CSTO and progress the dispersion of particles. The photo-luminescence (PL) spectra illustrate that the CSTO sample has two tough emissions. These clarification results from the creation of the CSTO bond and the existence of CdS roughly anatase, which would impede the development of TiO2 powder. The internal micro-structure, thus obtained will make the permanence of our composite sample, allowing a development of optical features of TiO2 composite.

关键词： calculation of phase diagrams (CALPHAD)   high-speed steels   neural networks   simulation   steel design  

摘要： Increasing requirements concerning the operational conditions and durability of tools create a demand for the optimization of tool steels. High-speed steels (HSSs), for example, contain high amounts of carbides embedded in a secondary hardenable martensitic matrix. The wear behavior and the mechanical properties of HSS can be optimized for a certain application by adjusting the type and amount of carbides, as well as their compositions and the composition of the matrix. Computational thermodynamics based on the calculation of phase diagrams method allow the estimation of arising phases as well as phase compositions during the solidification or the heat treatment of a steel. However, in complex alloy systems, for example, HSS, the relationships between the content of alloying elements and the stability and the composition of phases can be complicated and nonlinear. Therefore, it can be difficult to find alloy compositions that are suitable to achieve a desired microstructure with iterative calculations. To handle this difficulty, a computational tool is developed, which determines compositions to obtain predefined HSS microstructures. The computational tool is based on a neural network that was previously trained with a thermodynamically calculated database. The efficiency of this approach is experimentally verified by producing and investigating laboratory melts of different HSS.

关键词： 3D conformal porous microstructure   modified fabric   breath figure   oil-water separation   self-powered sensor  

摘要： The conventional use of textiles as substrates for the incorporation of brick materials (i.e., polymers and nanomaterials) is ubiquitously developed with primary purposes for introducing desired technical/functional performance rather than maintaining the aesthetic/decorative characteristics and inherent advantages (i.e., flexibility and permeability) of textiles. Such kinds of modified textiles with typical solid coating layers, however, are becoming more and more unsuitable for some emerging applications, such as smart wearable devices. Herein, we presented a brand-new kind of modified textiles with brick materials formed contouring to the nonplanar fiber surfaces of a fabric substrate as a three-dimensional (3D) conformal layer of porous microstructures by a unique breath figure self-assembling strategy of employing water microdroplet arrays as soft dynamic templates that can be controlled, formed, and removed spontaneously. In this paper, the main influential factors such as solution concentration, relative humidity, temperature, brick materials, and fabric substrates were studied systematically to control and adjust the formation of 3D conformal porous microstructures (3CPMs). The obtained 3D conformal porous microstructured textiles (3CPMTs) hierarchically combining the inherent texture features of the porous network of textiles and honeycomb porous microstructures templated from water microdroplet arrays not only possess new functions of introduced brick materials (such as triboelectric performance and wettability) and maintain the excellent inherent advantages (such as flexibility, air permeability, water vapor permeability, and unique texture features) of fabrics but also enhance the tensile strength and thermal insulation performance of substrates. Taking advantage of the introduced functions, they can be either used for conventional applications (i.e., oil/water separation) with enhanced performance or explored for new applications (i.e., self-powered sen

关键词： Porous composite   Adaptive sound absorber   Microstructure-based modelling   Additive manufacturing  

摘要： This work investigates a porous composite with modifiable micro-geometry so that its ability to absorb noise can be accommodated to different frequency ranges. The polymeric skeleton of the composite has a specific periodic structure with two types of pores (larger and smaller ones) and two types of channels (wide and narrow ones), and each of the large pores contains a small steel ball. Depending on the situation, the balls block different channels that connect the pores, and therefore alter the visco-inertial phenomena between the saturating air and solid skeleton which take place at the micro-scale level and are responsible for the dissipation of the energy of acoustic waves penetrating the porous composite. All this is studied numerically using advanced dual-scale modelling, and the results are verified by the corresponding experimental tests of 3D-printed samples. Particular attention is paid to the prototyping and additive manufacturing of such adaptive porous composites.

关键词： 超声压印技术   PET聚合物材料   表面微结构   疏水性   接触角  

摘要： 为考察利用超声压印技术在PET聚合物材料表面制备疏水性微结构的技术可行性,以超声波塑料焊接机为核心搭建了超声压印平台,采用飞秒激光技术在7076航空铝表面制备一系列不同尺寸的立方体微结构疏水性点阵,并以此作为压印模具在PET材料表面制备疏水性微结构,采用白光干涉仪和接触角测量仪对其表面形貌和疏水性进行表征。结果表明:压印后的PET材料表面液滴接触角可达129.5°,较初始PET材料表面液滴接触角74.9°有大幅提升,表明压印后PET材料表面的疏水特性显著提升,证实了利用超声压印技术制备PET材料疏水表面的可行性;模具的疏水性是影响PET材料疏水性的一个关键因素,随着微结构点阵间距的增加,即固液接触的面积分数增加,PET压印样件的疏水性降低;微结构点阵间距相同时,微结构边长越小,其疏水性越好。