Slow crack growth and hydrothermal aging stability of an alumina-toughened zirconia composite made from La2O3-doped 2Y-TZP

A very tough zirconia matrix is interesting to fabricate alumina-toughened zirconia (ATZ) and composites generally processed from 3Y-TZP do not exhibit very high toughness. The strategy of lowering the yttria content to increase toughness however is normally associated with an increased hydrothermal aging susceptibility. In this work, a 0.4 mol% La₂O₃ doped 2Y-TZP matrix was investigated to realize a 20 wt.% alumina toughened zirconia composite with a substantially high aging resistance. The higher transformation toughening in the composite shifted the V-K_I towards higher K_I values, while preserving the slope of the curve, resulting in a threshold K_I0 of 4.0 MPa m^1/2 and fracture toughness (K_IC) of 7.1 MPa m^1/2. These composites can offer a better compromise between aging and crack resistance than traditional 3Y-TZPs and plain ATZ composites without La₂O₃ doping.     

Cyclic fatigue of silica refractories – effect of test method on failure process

Silica refractories serving in high temperature industrial installations fail due to thermo-mechanical cyclic loads. The failure process was investigated by performing cyclic fatigue tests of several methods. In uni-axial compression the samples were tested either with constant force or displacement amplitude or with fixed upper displacement limit. In bending constant displacement amplitude tests were done. The investigation was supported by monotonic loading tests and microstructural analysis. It was determined that the fatigue failure occurs due to the degradation of interlocking in the crack wake. Cracking of larger grains is important for the crack initiation. The test set-up and the loading procedures significantly influence the potential to resist the crack propagation. Cyclic loading produces less brittle failure than monotonic loading. The displacement controlled method allows more gradual, less brittle, failure than the force controlled method. The potential of the crack arrest is less developed in bending than in compression.     

Orthogonal ligation to spherical polymeric microparticles: Modular approaches for surface tailoring

Modular ligation strategies for the functionalization of polymeric microspheres provide new perspectives for their applications in material science. In the current trend article we highlight variable synthetic procedures for generating functional microspheres via orthogonal modular conjugation chemistries. An overview of the different surface chemistries available is provided, followed by surface-sensitive characterization techniques relevant for the microparticles. Finally, we explore future trends in modular orthogonal modification approaches on microparticles and provide an outlook on the perspectives that the field of surface-modification of polymeric microparticles holds.     

Synthesis and functionalization of nanoengineered materials using click chemistry

The synthesis of nanoengineered materials with precise control over material composition, architecture and functionality is integral to advances in diverse fields, including biomedicine. Over the last 10 years, click chemistry has emerged as a prominent and versatile approach to engineer materials with specific properties. Herein, we highlight the application of click chemistry for the synthesis of nanoengineered materials, ranging from ultrathin films to delivery systems such as polymersomes, dendrimers and capsules. In addition, we discuss the use of click chemistry for functionalizing such materials, focusing on modifications aimed at biomedical applications.     

国内多孔介质中天然气水合物成藏机理研究现状

南中国海的沉积物和青藏高原等冻土带中富含大量的天然气水合物,其成藏机理是开采天然气水合物的关键之一。本文介绍了中国近年来对多孔介质中模拟天然气水合物成藏的研究现状,包括主要的研究单位、研究者、研究方法与仪器设备以及近年来国内期刊上多孔介质中天然气水合物成藏机理的文献情况。     

内压作用下斜接弯管纵向半穿透裂纹应力强度因子研究

采用三维有限元技术,应用ANSYS对内压作用下含纵向半穿透裂纹斜接弯管的应力强度因子进行了系统的分析。建立了三维有限元裂纹模型,对裂纹前沿应力强度因子的影响因素进行了研究,分析了不同内压下无量纲参数裂纹相对深度a/t、裂纹相对形状b/a、管壁相对厚度Do/t对应力强度因子的影响。     

尿素高压管道支管座在连接管焊缝侧开裂原因分析及防范措施

介绍美荷型480kt/a尿素装置高压系统,高压管道支管座与接管(≤DN50)焊缝在熔合线上的开裂原因及在线处理情况,并对开裂原因进行分析,得出损坏的主要原因由应力腐蚀引起,针对腐蚀原因提出防范和整改措施。     

对石化设备不锈钢应力腐蚀开裂的认识与反思

根据石化装置不锈钢设备曾发生过应力腐蚀开裂的事例,总结与归纳出一些共性的东西,可供选材、设计、加工、维护、管理与检测时借鉴,以尽可能减少设备腐蚀开裂事故.     

耐温耐盐复合交联调剖体系实验研究

使用部分水解聚丙烯酰胺、有机铬和水溶性酚醛为主剂,制备了一种复合交联调剖体系,考察了聚合物及交联剂浓度、矿化度、温度等因素对体系成胶性能的影响。结果表明,体系在矿化度为15 000 mg/L,温度低于90℃的条件下,仍可生成较高强度的凝胶,具有良好耐温耐盐性能。通过单管和双管并联岩心封堵实验来模拟体系对地层的调剖过程,结果表明,体系对单管岩心的封堵率高于96%,突破压力梯度大于35 MPa/m;双管并联岩心实验时,体系对高渗管岩心的封堵率在95%以上,而对低渗管岩心的封堵率低于15%。     

ASA材料在PVC型材应用中的若干思考

简要介绍了PVC材料与ASA材料,探讨了PVC材料与ASA材料物理性能和加工性能上的差异、颜料对ASA材料性能的影响、ASA/PVC共挤型材及门窗的热变形问题,总结了ASA/PVC共挤型材变形的影响因素;为了解决ASA/PVC共挤型材加工过程和使用过程中的变形问题,还给出了具体的注意事项。