Performance of BaZrO3/Y2O3 dual-phase refractory applied to TiAl alloy melting

Vacuum induction melting is a potential process for the preparation of TiAl alloys with good homogeneity and low cost. But the crucial problem is a selection of high stability refractory. In this study, a BaZrO₃/Y₂O₃ dual-phase refractory was prepared and its performance for melting TiAl alloys was studied and compared with that of a Y₂O₃ refractory. The results showed the dual-phase refractory consisted of BaZr_1-xY_xO_3-δ and Y₂O₃(ZrO₂), exhibited a thinner interaction layer (30 μm) than the Y₂O₃ refractory (90 μm) after melting the TiAl alloy. Although the TiAl alloys melted in the dual-phase and Y₂O₃ refractory exhibited similar oxygen contamination (<0.1 wt%), the alloy melted in the dual-phase refractory had smaller Y₂O₃ inclusion content and size than that in the Y₂O₃ refractory, indicating that the dual-phase refractory exhibited a better melting performance than the Y₂O₃ refractory. This study provides insights into the process of designing highly stable refractory for melting TiAl alloys.     

SLM printing of cermet powders: Inhomogeneity from atomic scale to microstructure

It is very challenging for 3D printing based on the selective laser melting (SLM) technology to obtain cermet bulk materials with high density and homogeneous microstructures. In this work, the SLM process of the cermet powders was studied by both simulations and experiments using the WC-Co cemented carbides as an example. The results indicated that the evolution of the ceramic and metallic phases in the cermet particle during the heating, melting and solidification processes were all significantly inhomogeneous from atomic scale to mesoscale microstructures. As a consequence, the microstructural defects were caused intrinsically in the printed bulk material. The formation and growth of the bonding necks between the particles were mainly completed at the later stage of laser heating and the early stage of solidification. Both simulations and experiments demonstrated that thin amorphous layers formed at the ceramics/metal interfaces. This work disclosed the mechanisms for the evolution from the atomic scale to microstructure during the SLM printing of cermet powders, and discovered the origin of the defects in the printed cermet bulk materials.     

Study on ice-melting performance of gradient gas diffusion layer in proton exchange membrane fuel cell

In this study, a three-dimensional model was established using the lattice Boltzmann method (LBM) to study the internal ice melting process of the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC). The single-point second-order curved boundary condition was adopted. The effects of GDL carbon fiber number, growth slope of the number of carbon fibers and carbon fiber diameter on ice melting were studied. The results were revealed that the temperature in the middle and lower part of the gradient distribution GDL is significantly higher than that of the no-gradient GDL. With the increase of the growth slope of the number of carbon fiber, the temperature and melting rate gradually increase, and the position of the solid-liquid interface gradually decreases. The decrease in the number of carbon fibers has a similar effect as the increase in the growth slope of the number of carbon fibers. In addition, as the diameter of the carbon fiber increases, the position of the solid-liquid interface gradually decreases first and then increases.     

面向消费类电子产品的自动化生产线成组技术

针对现代消费类电子产品快速更新换代的现状, 介绍了该类产品的自动化生产线成组技术,阐述了通过度量消费类电子产品相似性和派生性特征,对产线进行成组编码的原理,研究产线工位单元的建模方法,描述了建模内容,并通过有无装载板的产线结构,论述了产线成组编码集成的途径和方法.     

烟机结垢的成因分析及防范措施

通过对烟机垢物的元素和晶体组成进行表征，分析其形成条件，计算验证并探讨垢物的形成过程，并提出应对防范措施。烟机结垢过程为：极少数原料油滴在反应汽化段内未完全汽化，未汽化油黏附在催化剂细粉表面并缩合生焦；部分焦炭颗粒未在再生器内烧尽，进入烟道后继续燃烧达到细粉的熔融温度，转化为液相黏性物质；携带微量高温熔融粉尘的烟气在三级旋风分离器下料口、烟机叶片等部位受高速离心作用，黏附到易结垢部位，形成无定形垢物。可通过提升原料油喷嘴雾化效果，调整合适的剂油比和系统细粉含量来减少烟机结垢。     

橡胶促进剂DM的合成工艺

M氧化生成DM是自由基反应机理，结合微反应器机理，采用分子氧化的反应方式，选用绿色溶剂异丙醇、环境友好型氧化剂H202，一步法制取高品质DM。对反应时间、反应温度、氧化剂用量等因素进行考察，确定最佳工艺条件为：反应时间90min，反应温度55℃，氧化剂不过量，碱过量5％，M—Na溶液M含量30％，加料时N60 min，溶剂用量为M—Na溶液质量的1．5倍，所得产品质量合格，熔点可达180℃。     

邻—(4—乙基苯甲酰基)苯甲酸的研究

本文阐述了通过Friedel-Crafts反应合成邻-(4-乙基苯甲酰基)苯甲酸的方法.研究了影响产物质量的因素,提出了适宜的工艺条件.     

堇青石基玻璃陶瓷的制备与展望

介绍了制备堇青石基玻璃陶瓷的三种方法：熔融法、烧结法和溶胶-凝胶法，综述了玻璃组成、添加剂和成核剂对堇青石基玻璃陶瓷的烧结及性能的影响，并对其未来的发展进行了展望。     

有机羧酸钠盐对PET结晶和熔融行为的影响

采用差示扫描量热仪研究了5种具有不同取代基的苯甲酸钠盐作为结晶成核剂对聚对苯二甲酸乙二醇酯（HET）结晶和熔融行为的影响，并同滑石粉进行了对比。结果表明，成核剂的加入能明显改变PET的结晶和熔融行为。苯甲酸钠、对苯二甲酸甲酯单羧酸钠和对羟基苯甲酸钠提高既汀的熔融结晶温度（Tc）分别达22．93、21．7和19．37℃，但使PET降解严重；对苯酚钠甲酸钠能够提高Tc达17．75℃且对PET相对分子质量影响很小；对苯二甲酸二钠成核作用最差。低于滑石粉。此外，成核剂的成核能力越强，PET双熔融峰中的低温峰顶温度就越高。