高分子材料导热性能影响因素研究进展

介绍了高分子材料导热性能影响因素研究进展，重点阐释了聚合物基体的结构特性（链结构、分子间相互作用、取向、结晶度等）、导热填料（种类、含量、形态、尺寸等）以及制备方法等对高分子材料导热性能的影响。     

基于立体定向靶标的探针式多视场三维视觉测量系统

针对含有遮挡区域、深孔及凹槽等特征的多面体或回转体物体，设计了一套基于立体定向靶标的探针式多视场三维视觉测量系统，并阐述该套测量系统的结构组成和基本工作原理。首先，基于近景摄影测量技术建立立体定向靶标的6个单元模型，计算靶标各侧面角点在各自单元模型内的坐标，再通过单元模型的链接和光束平差，获取全部角点的精确全局坐标，并将其作为立体定向靶标的全局控制点。然后，设计了利用共面角点辅助定位的探针，仍基于近景摄影测量技术解算出角点和测头在探针坐标系中的精确坐标。最后，利用共面的棋盘格角点与其像平面之间的单应性矩阵，推导全局坐标系、探针坐标系各自与相机坐标系的位姿关系，进而求得探针测头的全局坐标。以量块（量棒）的标准长度作为评价指标，在2m×1.5m的视场范围内测量精度优于0.1mm。测量实验表明，多视场三维视觉测量系统用于具有回转体结构特征的水壶测量，能够获取水壶表面全部区域的点云数据。     

Competitive growth of Al2O3/YAG/ZrO2 eutectic ceramics during directional solidification: Effect of interfacial energy

The microstructure evolution and growth behavior of the Al₂O₃/Y₃Al₅O₁₂(YAG)/ZrO₂ ternary eutectic ceramics during directional solidification were well investigated. During directional solidification of the Al₂O₃/YAG/ZrO₂ ternary eutectic ceramics, {} Al₂O₃ paralleled with {001}ZrO₂ while they did not parallel with {001}YAG at the same time in the competitive growth stage. All of the interfaces parallel to each other finally. The area percentage of the Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are 40.4 ± 0.2% and 30.8 ± 0.1%, respectively, higher than that of the Al₂O₃/YAG (28.8 ± 0.2%). The content of Al₂O₃ and YAG phases are 39.9% and 41.1%, respectively, almost double of that of ZrO₂. The interfaces of Al₂O₃/ZrO₂ and YAG/ZrO₂ are shorter and more dispersed than that of the Al₂O₃/YAG. It was found that the interfacial energy of Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are lower than that of Al₂O₃/YAG. It can be concluded that interfacial energy plays a decisive role in affecting the crystallographic orientation and interfaces distribution in the Al₂O₃/YAG/ZrO₂ eutectic since the interfaces of Al₂O₃/ZrO₂ and YAG/ZrO₂ with lower interfacial energy can be formed more easily during directional solidification. Therefore, the contents of Al₂O₃/ZrO₂ and YAG/ZrO₂ interfaces are higher. This study can provide theoretical guidance for interface design of multi-phase materials.     

热定形对并列复合再生聚酯短纤维性能的影响

以再生聚酯瓶片料和泡料混合料为原料进行并列复合纺丝,并经后纺工艺处理得到并列复合再生聚酯短纤维。通过对纤维进行干热定形,研究热定形温度、时间对并列复合再生聚酯短纤的强伸性能、卷曲性能和热收缩性能的影响。结果表明:聚酯短纤维的断裂强度和断裂伸长率随着热定形温度升高而增大;断裂强度随热定形时间的延长逐渐下降,断裂伸长率先增大后减小,在20 min时达到最大值,为17.4%,声速取向因子则随着热定形时间的延长呈现下降趋势。纤维的卷曲性能随着热定形温度的升高而改善,较短的时间内,纤维的卷曲性能已经达到最佳;热定形温度的升高使纤维的热收缩率增大;并列复合再生聚酯短纤维的最佳热定形温度是140～160℃,最佳定形时间为10 min。     

Rayleigh-Type Wave in A Rotated Piezoelectric Crystal Imperfectly Bonded on a Dielectric Substrate

Propagation characteristics of Rayleigh-type wave in a piezoelectric layered system are theoretically investigated. The piezoelectric layer is considered as a cubic crystal with finite thickness rotated about Y-axis and is imperfectly bonded onto a semi-infinite dielectric substrate. The imperfect interface between the two constituents is assumed to be mechanically compliant and dielectrically weakly conducting. The exact dispersion relations for electrically open or shorted boundary conditions are obtained. The numerical results show that the phase velocity of Rayleigh-type wave is symmetric with respect to the cut orientation of 45。 and can achieve the maximum propagation speed in this orientation. The mechanical imperfection plays an important role in the dispersion relations, further the normal imperfection can produce a significant reduction of phase velocity comparing with the tangential imperfection. Comparing with the mechanical imperfection the electrical imperfection makes a relatively small reduction of phase velocity of Rayleigh-type wave. The obtained results can provide some fundamentals for understanding of piezoelectric semiconductor and for design and application of piezoelectric surface acoustic wave devices.     

原纤化过程对纸基空气滤材结构和性能的影响

以木浆为原料,分别采用不同磨浆转数对木浆纤维进行原纤化处理,使其表面分丝帚化,再利用冷冻干燥技术保持纤维表面分丝状态而避免角质化,从而制备出可生物降解的纸基空气过滤材料。研究了不同程度原纤化处理对纸基空气滤材结构和性能的影响,探讨了原纤化处理对滤材Z向形貌的影响机理。结果表明,浆料浓度为1.5%、冷冻温度为-56℃、磨浆转数为50000 r时,纸基空气滤材具有较佳的过滤性能。     

Improving EBSD precision by orientation refinement with full pattern matching

We present a comparison of the precision of different approaches for orientation imaging using electron backscatter diffraction (EBSD) in the scanning electron microscope. We have used EBSD to image the internal structure of WC grains, which contain features due to dislocations and subgrains. We compare the conventional, Hough-transform based orientation results from the EBSD system software with results of a high-precision orientation refinement using simulated pattern matching at the full available detector resolution of 640 × 480 pixels. Electron channelling contrast imaging (ECCI) is used to verify the correspondence of qualitative ECCI features with the quantitative orientation data from pattern matching. For the investigated sample, this leads to an estimated pattern matching sensitivity of about 0.5 mrad (0.03°) and a spatial feature resolution of about 100 nm. In order to investigate the alternative approach of postprocessing noisy orientation data, we analyse the effects of two different types of orientation filters. Using reference features in the high-precision pattern matching results for comparison, we find that denoising of orientation data can reduce the spatial resolution, and can lead to the creation of orientation artefacts for crystallographic features near the spatial and orientational resolution limits of EBSD.     

Effects of sintering in a high magnetic field on properties of vitrified bond and vitrified CBN composites

Vitrified bond CBN grinding wheels are being widely used due to their superior performance. Also, advantages of vitrified grinding wheels are high elastic modulus, stable chemical property, and low thermal expansion coefficient. Brittleness and low strength are key factors restricting the development of vitrified bond CBN grinding wheels. In this paper, the sintering in a high magnetic field was innovatively introduced into the manufacturing of vitrified bond CBN grinding wheels, and the effects of sintering in a high magnetic field on properties on vitrified bond and vitrified CBN composites were systematically investigated. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction. It was observed that microstructure of vitrified bond could be changed, grain orientation could be controlled and average grain size could be decreased in a high magnetic field, while vitrified bond strength could be simultaneously improved. High quality vitrified bond could be obtained by appropriately adjusting the strength and direction of high magnetic field. Results demonstrated that vitrified bond properties were improved when the magnetic field strength was 6?T. In order to highlight the high magnetic field effect on the vitrified CBN composites, the ordinary CBN abrasives and nickel plated CBN abrasives were used respectively. Microstructures, bending strengths of vitrified CBN composites were compared in different high magnetic fields. When the magnetic field strength was appropriate (less than 6?T), the binding characteristic of vitrified bond CBN composites with nickel plated CBN abrasives was greatly improved. The highest bending strength value of vitrified CBN composites was 79.5?MPa in 6?T high magnetic field.     

The correlation between porosity characteristics and the crystallographic texture in extruded stabilized aluminium titanate for diesel particulate filter applications

Porous ceramic diesel particulate filters (DPFs) are extruded products that possess macroscopic anisotropic mechanical and thermal properties. This anisotropy is caused by both morphological features (mostly the orientation of porosity) and crystallographic texture. We systematically studied those two aspects in two aluminum titanate ceramic materials of different porosity using mercury porosimetry, gas adsorption, electron microscopy, X-ray diffraction, and X-ray refraction radiography. We found that a lower porosity content implies a larger isotropy of both the crystal texture and the porosity orientation. We also found that, analogous to cordierite, crystallites do align with their axis of negative thermal expansion along the extrusion direction. However, unlike what found for cordierite, the aluminium titanate crystallite form is such that a more pronounced (0 0 2) texture along the extrusion direction implies porosity aligned perpendicular to it.     

Unraveling the attitudes on entrepreneurial universities: The case of Croatian and Spanish universities

The objective of this paper is to present evidence that there are different types of supportive faculty members. We conducted a case study on a sample of Croatian and Spanish universities by using an already tested ENTRE-U scale for measuring the faculty members' attitudes. These two scenarios are quite different in terms of their innovation systems, economic context and university system. We tested and found no evidence of any statistically significant difference due to the country. These two facts suggest the possible existence of an isomorphic trajectory when implementing entrepreneurial universities regardless the context. University managers should be aware of the existence of three different types of supportive individuals. Each of these groups requires a certain program of human resource development. This shifts the debate to how entrepreneurial universities should manage the tensions arising from the need of some degree of specialization in any of the three roles of the faculty members, namely teaching, researching and transfer of the knowledge stemming from research results.