关键词： 聚氨酯   环氧树脂   玄武岩鳞片   沟槽结构   低表面能  

摘要： 以端羟基聚丁二烯型聚氨酯(以下称为HPU)、环氧树脂、硅烷偶联剂处理玄武岩鳞片为主要原料,利用聚氨酯特殊的微相分离结构与片层结构的玄武岩鳞片堆积组装成表面沟槽微结构的低表面能材料,用SEM扫描电镜表征材料表面及侧面微结构特征,接触角测量仪测得材料表面静态水接触角达110°。

关键词： Mechanical properties   Microstructural effects   Polycrystal plasticity   Anisotropy   Additive manufacturing   Powder bed fusion   Directed energy deposition   High-Mn steel  

摘要： Metal additive manufacturing (AM) provides an unprecedented opportunity to explore extreme microstructural regimes and their associated effects on the mechanical response of polycrystals. In this work, a single alloy (composition) belonging to the high-Mn steels family was processed by a conventional thermo-mechanical treatment and two different AM processes. This resulted in three different materials with strikingly diverse microstructures with respect to the microstructural size and polarity. The influence of disparities in the statistical microstructural features arising from the different processing conditions on the (macroscopic) mechanical response was investigated through an experiment-simulation approach. The (as-processed/as-built) microstructures were analyzed on the meso-scale for derivation of a set of parameters, namely meso-structure descriptors, which adequately describe the meso-structural heterogeneity features. To link the microstructure and mechanical properties, we used a physics-based crystal plasticity modeling approach in the framework of full-field polycrystal homogenization. The meso-structure descriptors together with the submeso-scale/constitutive microstructural parameters were used to simulate the (anisotropic) mechanical response of the aforementioned materials. Then, for a reduced-order quantitative assessment of the effect of microstructural polarity on the anisotropic mechanical response, the plastic anisotropy indices were defined and calculated using the simulation results. This study provides new insights into the primary microstructural effects (the size and polarity effects) on the mechanical (stress and strain hardening) response of polycrystals as well as the propensity of micro-mechanisms accommodating polycrystal plasticity in highly different microstructural regimes, particularly those typically obtained by metal AM.

关键词： Cement mortar composites   Supplementary cementitious materials (SCMs)   Microstructure   Blast furnace slag   Fly ash   Bottom ash   Blaine fineness   Compressive strength  

摘要： The silica-rich supplementary cementitious materials (SCMs) are the key components of mechanical and microstructural properties. The use of SCMs results in improving the mechanical and microstructural properties and decreasing the environmental burden caused by cement production. In this regard, this paper reports a study to compare the influence of silica-rich supplementary cementitious materials (slag, fly ash, and bottom ash) having similar Blaine fineness on cement mortar composites in terms of mechanical and microstructural properties. The Blaine fineness of supplementary cementitious materials was chosen at cement Blaine fineness by using short grinding time due to minimize energy consumption and cost. Supplementary cementitious materials (slag, fly ash, and bottom ash) were ground at similar cement Blaine fineness (similar to 3300 cm(2)/g) and then by replacing 5 % and 20 % with cement, the 7-, 28-, 90-day mechanical and microstructural properties of cement mortar composites incorporating SCMs were examined. As a result, it was observed that the compressive strength properties of cement mortar composites incorporating 20 % slag gave similar strength of control samples (without SCM) according to samples with fly ash and bottom ash having similar fineness and this will decrease the required amount of cement and grinding time for the target strength properties, thus the number of CO2 emitted to nature will also decrease and less energy consumption, and the cost-effectiveness will be ensured by shorter grinding time for target strength.

关键词： 3D printer   PLA   Fused deposition modelling (FDM)   Additive manufacturing (AM)   microstructural analysis   raster angles   Scanning electron microscopy (SEM)   tensile test  

摘要： One of the most significant parameters of the Fused Deposition Modelling (FDM) for 3D printing process is the raster angle. In this study, the five different raster angles are used to fabricate the 3D parts using thermoplastic material - polylactic acid (PLA), and tensile properties of these parts are investigated to identify the best raster position to fabricate the strongest 3D printing part. In this study, the microstructural analyses on fracture interface, and on outer and inner surfaces of these 3D parts are performed using a scanning electron microscopy (SEM) to examine material failure modes and reasons, and defects in the 3D parts. This study identified the best raster orientation to lie down the layers of 3D printing material during the process. This study also identified that there are several defects in 3D printed parts at micro level that have large impact on mechanical properties of 3D printed part.

关键词： La0.7Sr0.3Ti0.15Fe0.65Ni0.2O3-delta (LSTFN)   Sintering-temperature   Coating thickness   Polarization resistance  

摘要： The modified Pechini method was applied to prepare a highly active and novel cathode material La0.7Sr0.3Ti0.15Fe0.65Ni0.2O3-delta (LSTFN). This material was coated on the LGSM electrolyte through a screen-printing technique with variable thicknesses of 28 +/- 8, 41 +/- 8, and 62 +/- 8 mu m, respectively. Different fabrication parameters, including sintering temperature, time, coating thickness, and variations in ball-milling, which affect the electrochemical performance of the cathode material, were investigated. X-ray diffraction analysis of the cathode material suggested that it exhibits a cubic crystal structure with a LSTFN single phase. The morphological studies were conducted using scanning electron microscopy (SEM), which confirmed that the electrode material had a highly porous structure. Meanwhile, the electrochemical properties of the material were studied by electrochemical impedance spectroscopy (EIS), which revealed that by varying different parameters, the electrochemical performance of the electrode material was enhanced. The coated cathode materials with variable thicknesses were analyzed at different sintering temperatures and times. Experimental results suggest that the optimum sintering temperature and time were 950 degrees C and 3 h, respectively, at which LSTFN exhibits the minimum polarization resistance (R-P) of 0.046 Omega cm(2) when sintered at 800 degrees C for 3 h.

关键词： Surface tension   Liquids   Peptides and proteins   Phase separation   Molecular interactions  

摘要： This perspective article highlights recent progress and emerging challenges in understanding the formation and function of membraneless organelles (MLOs). A long-term goal in the MLO field is to identify the sequence-encoded rules that dictate the formation of compositionally controlled biomolecular condensates, which cells utilize to perform a wide variety of functions. The molecular organization of the different components within a condensate can vary significantly, ranging from a homogeneous mixture to core-shell droplet structures. We provide many examples to highlight the richness of the observed behavior and potential research directions for improving our mechanistic understanding. The tunable environment within condensates can, in principle, alter enzymatic activity significantly. We examine recent examples where this was demonstrated, including applications in synthetic biology. An important question about MLOs is the role of liquid-like material properties in biological function. We discuss the need for improved quantitative characterization tools and the development of sequencestructuredynamics relationships.

关键词： Machine learning   Microstructure   Two-phase materials   Finite element analysis   Two-point correlation   Principal component analysis  

摘要： This study explores the use of supervised machine learning (ML) to predict the mechanical properties of a family of two-phase materials using their microstructural images. Random two-phase microstructures with a diversity of inclusion volume fractions, size distributions, and/or shapes are input into a finite element analysis program to determine the elastic modulus, Poisson's ratio, and phase stresses. The finite element analysis results establish the "ground truth" to train the supervised ML models. Two-point correlation (TPC) functions and principal component (PC) analysis are applied to the microstructures before training and testing the artificial neural network (ANN) and forest ensemble MLs. The chosen ML methods are found to accurately predict the homogenized elastic properties. Although the PCs for each set of microstructures are unique, recognizable patterns are detected that signify microstructural features that are key to microstructure-based property prediction. This work enables the development of ML algorithms to predict the mechanical properties of complex, multi-phase microstructural composites, based on microstructural images.

关键词： 升温制度   Al-MgO-Al_(2)O_(3)耐火材料   (Al_(2)OC)x(AlN)1-x   相组成   显微结构  

摘要： 以金属Al粉、电熔镁砂和电熔棕刚玉为原料,热固性酚醛树脂为结合剂,制备了Al-MgO-Al_(2)O_(3)耐火材料试样。在空气条件下以两种升温制度对其进行热处理:1)直接升温至1500℃保温2 h;2,先升温至580℃保温2 h后再升温至1500℃保温2 h。利用XRD、SEM等探究了升温制度对材料相组成及显微结构的影响。结果表明:1)直接升温至1500℃热处理后,材料中生成的非氧化物相主要为Al 4O 4C;2,580℃保温2 h有利于金属铝在高温下以Al 2O(g)的形式参与反应,进而使材料中生成(Al 2OC)x(AlN)1-x纤维;3)先580℃保温再1500℃热处理后材料中形成了以镁铝尖晶石和(Al 2OC)x(AlN)1-x纤维为主成分的致密层。

关键词： 负泊松比   拓扑优化   多材料设计   微结构  

摘要： 复合材料优化设计为负泊松比结构提供更大的设计空间,可以充分挖掘材料的各种潜力。为实现多材料负泊松比微结构拓扑优化设计,文中基于序列插值法,对多材料密度进行归一化处理,得到了多材料插值模型,该模型能够使多材料在设计域内向不同材料点集合,可以在单一设计变量下完成多材料拓扑优化设计,无需增加额外设计变量。结合能量均匀化理论,以等效负泊松比为优化目标,进行相应的灵敏度分析,对优化模型进行求解,最终得到了具有负泊松比效应的多材料微结构。然后根据优化结果,对拓扑构型进行重构,并进行有限元分析,得到的结构具有负泊松比效应,结果表明,该方法能有效实现多材料负泊松比微结构拓扑优化设计。

关键词： C/C-ZrC-SiC复合材料   反应熔渗法   Fe_(x)Si_(y)   显微结构   烧蚀性能  

摘要： 为了改善C/C-ZrC-SiC复合材料的烧蚀性能,采用反应熔渗法(RMI)在1850℃制得一种新型耗散防热Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料,并研究熔渗母料中Fe含量的变化对该复合材料显微结构和烧蚀性能的影响。结果表明:随着熔渗母料中Fe含量的升高,复合材料的密度呈现先降低后增加的趋势。当Fe含量超过6%(摩尔分数)时,沿垂直无纬布方向,复合材料中出现独立于SiC和ZrC之间的Fe_(x)Si_(y)C固溶相,其相含量随Fe含量的升高而增多;沿平行无纬布方向,复合材料中发现众多以灰色Fe_(x)Si_(y)C相间隔的“团粒型”排布的ZrC相,其粒径约为10μm。通过对不同Fe含量的Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料烧蚀性能进行表征,结果表明,当Fe含量为8.5%(摩尔分数)时,Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料的烧蚀性能最佳,质量烧蚀率和线烧蚀率分别为2.3×10^(−3) g/s和0.7×10^(−3) mm/s,相比纯C/C-ZrC-SiC复合材料分别降低3.6×10^(−3) g/s和3.61×10^(−3) mm/s。其优异的抗烧蚀性能主要得益于低熔Fe_(x)Si_(y)相的耗氧耗热和SiO2熔体补偿,促使样品表面形成一层致密、低氧透过率的富SiO2层,避免基体的进一步烧蚀。