关键词： 聚醚醚酮   硫酸   表面粗糙度   细胞相容性  

摘要： 目的探讨硫酸酸蚀法构建具有更佳表面显微结构及细胞相容性的30%CF-PEEK复合材料的处理方案。方法分别用50%和98%硫酸处理CF-PEEK 5 min和30 min后,检测材料表面粗糙度、细胞毒性和表面贴壁细胞活性,与未处理材料做对比分析。结果经50%硫酸处理的材料表面均未发生明显改变,而经98%浓硫酸处理的材料有大量CF纤维束暴露,成骨细胞不断增值分裂,处理30min组材料表面贴壁细胞数目最高。结论 98%浓硫酸处理30%CF-PEEK复合材料可形成更有利成骨细胞贴附的表面粗糙度,但最佳酸蚀方案还需进一步优化。

关键词： 仿生结构   复合陶瓷刀具材料   显微结构   力学性能  

摘要： 针对不同烧结条件及TiC/WC组分比,采用热压烧结工艺制备出三层仿生结构复合陶瓷刀具材料。测试了仿生结构复合陶瓷材料力学性能,并对材料断口形貌和裂纹扩展进行了观察分析。结果表明:仿生结构复合陶瓷刀具材料抗弯强度达870 MPa,维氏硬度达21.83 GPa,断裂韧性达7.56 MPa·m^(1/2),比SG4均质陶瓷刀具材料性能有所提高。断口形貌显示仿生结构复合陶瓷刀具材料较SG4均质刀具材料晶粒细密,晶粒尺寸呈现多尺度特征。材料断裂模式为穿晶断裂和沿晶断裂混合型。仿生结构复合陶瓷材料表面裂纹扩展呈现偏转和分叉。裂纹穿过材料界面扩展时有明显偏转现象。

关键词： silver nanowires   capacitive pressure sensor   flexible   transparent   wearable electronics   e-skin  

摘要： The development of pressure sensors with highly sensitivity, fast response and facile fabrication technique is desirable for wearable electronics. Here, we successfully fabricated a flexible transparent capacitive pressure sensor based on patterned microstructured silver nanowires(AgNWs)/polydimethylsiloxane(PDMS) composite dielectrics. Compared with the pure PDMS dielectric layer with planar structures, the patterned microstructured sensor exhibits a higher sensitivity(0.831 kPa^-1, <0.5 kPa), a lower detection limit,good stability and durability. The enhanced sensing mechanism about the conductive filler content and the patterned microstructures has also been discussed. A 5×5 sensor array was then fabricated to be used as flexible and transparent wearable touch keyboards systems. The fabricated pressure sensor has great potential in the future electronic skin area.

关键词： 聚晶立方氮化硼(PcBN)   稀土氧化物   二硼化钛(TiB2)   棒晶  

摘要： 将cBN、Al、Ti微粉添加不同稀土氧化物进行混料,采用高温(1400℃)、高压(5.5GPa)原位合成聚晶立方氮化硼(PcBN)复合材料。通过X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)研究了添加Y2O3、Gd2O3、Nd2O3对PcBN复合材料物相和显微结构的影响,测试并分析了不同稀土氧化物对该体系中各试样相对密度和力学性能的影响。结果表明:添加稀土氧化物可以提高样品的致密度和显微硬度,其中添加Gd2O3比添加Y2O3和Nd2O3更有利于促进TiB2棒晶的形成,获得综合力学性能最佳的PcBN,其显微硬度为33.21GPa、抗弯强度为885.42MPa。

关键词： 复合材料   SPAN   钙基膨润土   电阻率  

摘要： 膨润土具有良好的物理性能和化学稳定性,具有广泛的用途,被誉为"万能石",一些学者尝试将其运用于电力行业,但因其电阻率较大而不适用。而制备出一种低电阻率的磺化聚苯胺(SPAN)改性钙基膨润土复合材料,使其在电力领域运用成为可能。采用插层聚合法制备导电SPAN-钙基膨润土复合材料,并通过正交法优化苯胺(An)加入量、反应时间、反应温度3个制备工艺参数。利用扫描电子显微镜(SEM)、红外光谱(FT-IR)、X射线衍射(XRD)、四点探针对钙基膨润土和SPAN-钙基膨润土复合材料进行微结构组织和性能表征。制备SPAN-钙基膨润土复合材料的最佳工艺方案为:An加入质量分数为50%,反应时间为16h,反应温度为0℃。反应时间对复合材料的性能影响较为显著。与钙基膨润土相比,SPAN-钙基膨润土复合材料的微观组织更均匀,晶面间距较大,电阻率下降了5个数量级,测得电阻率是1Ω·mm。

关键词： kaolin   diatomite   BET-specific surface area   sol-gel   ceramics   adsorbents  

摘要： Kaolin and diatomite are abundant and widely available geological materials that may immobilize or stabilize functional chemical species on their surfaces for various applications. Acid-treated kaolin and diatomite were intercalated with photocatalyst Ag-TiO2 nanoparticles using the sol-gel technique to prepare nanocomposite ceramic materials. The nanocomposites were sintered between 900 degrees C and 1000 degrees C to induce thermal reactions and to enhance nanoparticle-substrate attachment. Chemical and thermal characterizations of the acid-treated materials and intercalated nanocomposites were performed with energy-dispersive X-ray (EDX) analysis and differential scanning calorimetry (DSC), respectively. The Brunauer-Emmett-Teller (BET)-specific surface area and scanning electron microscopy (SEM) were employed for physical and microstructural characterization of the nanocomposites, respectively. Morphological studies revealed a uniform distribution of Ag-TiO2 nanocrystallites in pores and on mineral particle surfaces. The BET analysis showed remarkable surface and grain modification by sintering. Decreases in the BET-specific surface area were observed for the sintered ceramic nanocomposite, Ag-TiO2-kaolin (20.244 to 5.446 m(2)/g) and Ag-TiO2-diatomite (19.582 to 10.148 m(2)/g).

关键词： Density-based topology optimization   Material design   Periodic microstructures   Stress constraints   Homogenization  

摘要： This work aims at introducing stress responses within a topology optimization framework applied to the design of periodic microstructures. The emergence of novel additive manufacturing techniques fosters research towards new approaches to tailor materials properties. This paper derives a formulation to prevent the occurrence of high stress concentrations, often present in optimized microstructures. Applying macroscopic test strain fields to the material, microstructural layouts, reducing the stress level while exhibiting the best overall stiffness properties, are sought for. Equivalent stiffness properties of the designed material are predicted by numerical homogenization and considering a metallic base material for the microstructure, it is assumed that the classical Von Mises stress criterion remains valid to predict the material elastic allowable stress at the microscale. Stress constraints with arbitrary bounds are considered, assuming that a sizing optimization step could be applied to match the actual stress limits under realistic service loads. Density-based topology optimization, relying on the SIMP model, is used and the qp-approach is exploited to overcome the singularity phenomenon arising from the introduction of stress constraints with vanishing material. Optimization problems are solved using mathematical programming schemes, in particular MMA, so that a sensitivity analysis of stress responses at the microstructural level is required and performed considering the adjoint approach. Finally, the developed method is first validated with classical academic benchmarks and then illustrated with an original application: tailoring metamaterials for a museum anti-seismic stand.

关键词： Particulate composite   Mechanical characterization   Spectroscopic analysis   Microstructure   Piping material  

摘要： A doum palm particulate reinforced polyvinyl chloride (PVC) composite was developed with considerably low cost materials providing an overall light-weight and good mechanical properties for potential application as piping material. The specimen composite material was produced with the doum palm (leaves) particulate as reinforcement using compression molding. Results showed that density and elastic Modulus of the composite decreases and increases respectively with increasing weight fraction of the particulate reinforcement. The tensile strength increased to a maximum of 50 MPa and then decreased steadily. The composition with optimum mechanical property (50 MPa) was determined at 8, 62 and 30% formulation of doum palm particulates (reinforcement), PVC (matrix) and Kankara clay (filler) respectively with corresponding percentage water absorption of 0.72%, Young's Modulus of 2 GPa, flexural strength of 84 MPa and density of 1.43 g/cm(3). Fourier Transform Infrared (FTIR) analysis of the constituents showed identical bands within the range 4000-1000 cm(-1) with renown research work. Scanning Electron Microscopy (SEM) result showed fairly uniform distribution of constituents' phases. X-Ray Fluorescence (XRF) confirms the X-ray diffraction (XRD) result of the presence of minerals of kaolinite, quartz, rutile and illite in the kaolin clay. Comparison with conventional piping materials showed the composite offered a price savings per meter length of 86.6% and 35.9% when compared with carbon steel and PVC material. (C) 2018 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： Bone   Ultrastructure   Mineral lamellae   Collagen   Apatite   TEM  

摘要： The ultrastructure of bone has been widely debated, in part due to limitations in visualizing nanostructural features over relevant micrometer length scales. Here, we employ the high resolving power and compositional contrast of high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) to investigate new features in human bone with nanometer resolution over microscale areas. Using focused ion beam (FIB)-milled sections that span an area of 50m(2), we have shown how most of the mineral of cortical human osteonal bone occurs in the form of long, thin polycrystalline plates (mineral lamellae, MLs) which are either flat or curved to wrap closely around collagen fibrils. Close to the collagen fibril (<20nm), the radius of curvature matches that of the fibril diameter, while at greater distances, MLs form arcs with much larger radii of curvature. In addition, stacks of closely packed planar (uncurved) MLs occur between fibrils. The curving of mineral lamellae both around and between the fibrils would contribute to the strength of bone. At a larger scale, rosette-like clusters of fibrils are noted for the first time, arranged in quasi-circular arrays that define tube-like structures in alternating osteonal lamellae. At the boundary between adjacent osteonal lamellae, the orientation of fibrils and surrounding mineral lamellae changes abruptly, resembling the orthogonal patterns identified by others (Reznikov et al. in Acta Biomater 10:3815-3826, 2014). These features spanning nanometer to micrometer scale have implications for our understanding of bone structure and mechanical integrity.

关键词： 钢   钢  

ISBN: (纸本)9787030602527

摘要： 抗磨钢铁材料作为目前广泛采用的一类耐磨材料, 应用于冶金、矿山、电力、建材、能源、交通等领域。强化相作为抗磨钢铁材料中的重要组分, 在磨损过程中起到抗磨骨架的作用。合金元素种类和含量影响强化相的结构、硬度、脆韧性、热膨胀等热物理性能, 从而影响抗磨钢铁整体的耐磨性。本书采用第一性原理计算结合微观结构和性能表征的方法对抗磨钢铁中常见多元强化相的结构、力学和热学性质进行研究, 并从电子-原子层次揭示不同合金元素对性质影响的本质原因, 实现强化相组分、结构和性能的快速筛选与预测, 进而指导设计新型高性能抗磨钢铁材料, 对新型抗磨钢铁材料的成分设计与性能优化有一定的参考价值。