Improved additive manufacturing of silicon carbide parts via pressureless electric field-assisted sintering

High solids loading silicon carbide (SiC)-based aqueous slurries containing only .5 wt. % organic additives were utilized to create specimens of various geometries via an extrusion-based additive manufacturing (AM) technique. Pressureless electric field-assisted sintering was performed to densify each specimen without deformation. The combination of these techniques produced parts with >98% relative density despite containing only 5 wt.% oxide sintering additives. After sintering, specimens contained only the α-SiC and yttrium aluminum perovskite phases. This suggests the evolution of a nonequilibrium yttrium aluminate phase, as well as transformation from β-SiC to α-SiC. The fabrication method presented in this work has advantages over other AM techniques commonly used with SiC, because it does not require significant organic additives nor additional postprocessing steps such as chemical vapor infiltration or polymer impregnation and pyrolysis.     

Short fiber-reinforced oxide fiber composites

This paper presents a novel fiber spraying process for the manufacturing of short fiber bundle-reinforced Nextel™ 610/Al₂O₃-ZrO₂ oxide fiber composites (SF-OFC) and its characterization. First, the influence of varying fiber lengths (7, 14, and 28 mm, continuous fibers) and fiber orientations (unidirectional 0°, quasi-isotropic, ±45°) was investigated using hand-laid SF-OFC. Due to the weak matrix, the hand-laid material exhibited a strongly fiber-dominated material behavior, that is, variations in fiber length and orientation had a strong influence on the material properties. Second, the automated sprayed SF-OFC, however, exhibited a random orientation of the fiber bundles, which resulted in in-plane isotropic material properties. Average bending strengths of up to 177 MPa, strains of .39%, and a quasi-ductile fracture behavior were achieved. The strain was, therefore, in the range of fabric-reinforced OFC. While the bending strength of the SF-OFC was somewhat lower than that of fabric-reinforced OFC with the fiber orientation parallel to the loading direction, it was more than two times higher than the strength in 45° direction relative to the fabric reinforcement. Combined with good drapability and lower material costs compared to fabric-reinforced OFC, SF-OFC is, therefore, a promising material for industrial applications.     

大口径非球面系统的共基准加工与检验

针对大口径离轴非球面系统加工与装调的难点,提出了非球面光学系统共基准加工与检测的方法,对该方法的基本原理和实现过程进行了分析和研究。当光学系统的主镜和第三镜面形的RMS值优于λ/10(λ=632.8nm)时,对主镜和第三镜进行共基准装调和测试,并进行背板一体化装嵌,然后利用离子束对其进行一体化共基准加工。结合工程实例,对一大口径非球面系统口径为724mm×247mm的非球面主镜和口径为632mm×205mm的第三镜进行了共基准加工与检测,最终利用离子束共基准一体化精抛光得到主镜和第三镜面形的RMS值分别为0.019λ和0.017λ,满足光学成像。     

手机面板用蓝宝石玻璃性质与制备

蓝宝石具有硬度高、耐磨性、化学稳定性和耐热性好等特点,手机制造企业将蓝宝石用于代替玻璃作手机面板的覆盖材料。本文阐述了蓝宝石的结构、性质和大尺寸蓝宝石的制造方法,指出热交換法可以制备Φ380 mm的蓝宝石,冷心放肩微量提拉法(SAPMAC)也是一种有特色的制备方法。最后提出由蓝宝石和玻璃组成叠层材料,上层用耐磨的蓝宝石,下层为玻璃,可以节约成本,这将是手机面板发展的方向。     

基于快速成型技术的陶瓷零件无模制造

概述了几种近几年发展起来的陶瓷零件快速成型技术,着重介绍了它们的原理及应用于陶瓷零件制造的研究现状,比较分析了各种快速成型技术的优缺点及在产业化应用中存在的问题,并对今后该技术的发展进行了展望.     

PDMS微流控电泳芯片的快速制备

采用Protel软件绘制微流控沟道的形状,利用电路板制作技术加工出模具.该芯片由PDMS基片和PDMS盖片组成,微流控沟道位于基片上,深度和宽度分别为75μm和100μm,由盖片对其进行密封.考察了有绝缘漆模具和无绝缘漆模具制作的芯片的电泳分离情况.在所制作的PDMS微流控电泳芯片上对用异硫氰酸酯荧光素标记的氨基酸进行了电泳分离,当信噪比S/N=3时,最小检测浓度达到0.8×10-11mol/L.     

内孔焊技术在换热器制造中的应用

用内孔焊结构代替传统的端面焊结构是提高换热器管子与管板焊接接头抗应力腐蚀和缝隙腐蚀稳定性的根本途径.重点阐述了内孔焊的接头形式、焊接设备、工艺装备、焊接工艺参数以及具体实施过程中应注意的问题.     

改进的飞秒激光加工微型光波导方法

分析了垂直式加工中加工区域光强分布不对称的原因,从理论上总结出改进这种不对称的方法。在分析了仅引入单个透镜就能实现这一改进的可行性后,实验验证了这种改进方法。未改进之前加工出的光波导其端口两个方向直径之比为10:1,甚至更高;而改进后的比例则非常接近1:1。通过对光强不对称的改进,该方法有光路简单,无能量损失的优势。     

微乳技术在食品化学中的应用

介绍了微乳的概念、形成理论、组成以及微乳液制备过程中的一些关键问题,由于微乳液的特殊理化性质,使得这种新技术在食品化学领域具有相当潜在的应用前景。     

热稳定金刚石聚晶的制备及表征

在高温高压条件下（5.6GPa,1200℃～1480℃）,以含硼金刚石微粉为原料,镍基合金为烧结助剂,采用熔渗法成功制备了热稳定金刚石聚晶（Thermally stable PCD）。通过X射线衍射（XRD）和扫描电镜（SEM）,研究了烧结温度对热稳定金刚石聚晶的物相成分、微观组织形貌的影响;并与普通金刚石聚晶进行了差热（DTA）、热重（TG）的对比分析测试,结合X射线光电子能谱（XPS）测试结果给出了相应解释。实验结果表明：在压强为5.6GPa条件下,温度在1300℃～1450℃区间内,才能实现热稳定PCD的烧结;此时形成的热稳定PCD的耐热性和抗氧化性相比普通PCD均有较大幅度提高。