The origin of interfacial delamination in Au/ceramic cofired LTCC structure

The interfacial delamination of electrode/ceramic multilayer structure will seriously damage the reliability of low temperature co-fired ceramic (LTCC) module in practical applications. In this work, three kinds of glasses employed in Au electrode are designed and prepared to study the abnormal expansion and delamination process in the Au/ceramic LTCC multilayer structure. The interfacial delamination in the co-fired structure is found to be attributed to the abnormal expansion of glass in respect to Au electrode at high temperature, which is originated from the enlarged closed pores during the co-firing process. This conclusion is further confirmed by co-firing the sample in a low-pressure condition. The mechanism and elimination of interfacial delamination here provides a feasible solution for the design of novel glasses in Au electrode for LTCC applications.     

Cracking behavior and delamination mechanism of lamellar structured TBC with localized mixed oxides

Mixed oxide (MO) with localized growth feature and high growth rate remarkably affects the lifetime of thermal barrier coatings (TBCs), which indicates that clarifying the ceramic cracking mechanism induced by MO is critical for developing new coatings with high durability. Two kinds of TBC models involving spherical and layered mixed oxides are created to explore the influence of MO growth on the local stress state and crack evolution during thermal cycle. The growth of α-Al₂O₃ is also included in the model. The undulating interface between ceramic coat and bond coat is approximated using a cosine curve. Dynamic ceramic cracking is realized by a surface-based cohesive interaction. The ceramic delamination by simulation agrees with the experimental observation. The effects of MO coverage ratio and growth rate on the TBC failure are also discussed. The results show that the MO growth causes the local ceramic coat to bear the normal tensile stress. The failure mode of coating is turned from α-Al₂O₃ thickness control to MO growth control. Once the mixed oxide appears, local ceramic cracking is easy to occur. When multiple cracks connect, ceramic delamination happens. Suppressing MO formation or decreasing MO growth can evidently improve the coating durability. These results in this work can provide important theoretical guidance for the development of anti-cracking TBCs.     

Effects of stray AC on corrosion of 3-layer polyethylene coated X70 pipeline steel and cathodic delamination of coating with defects in 3.5 wt-% NaCl solution

In this work, the effects of stray alternating current (AC) on the corrosion of coated X70 pipeline steel and the delamination of 3-layer polyethylene (3PE) coatings with defects were investigated using COMSOL Multiphysics simulation, electrochemical impedance spectroscopy and three-dimensional (3D) digital microscope techniques. The results showed that under the same level of AC interference, pits with deeper maximum pit depth were observed at the smaller defect areas than those at larger defect areas. It was consistent with the simulation results that a greater corrosion current density was accompanied on samples with smaller defects. According to 3D digital images, the larger delamination of 3PE coatings was found on samples with smaller defects. With the increase of current density, the impedance of samples with small defects decreased, while that of samples with large defects increased. Additionally, with the same defect size, the maximum pit depth became deeper and the corrosion was more severe.     

Flutter of delaminated three-phase nano-composite beam-plates

ABSTRACT

In this article the supersonic flutter instability of delaminated carbon nanotube reinforced three-phase composite plate is investigated. The classical laminate plate theory and piston aerodynamic theory are developed to construct the governing equation of delaminated three-phase nano-composite plates. The effective material properties are obtained using Halpin-Tsai relation and rule of mixture. The effects of different parameters including carbon nanotubes (CNTs) weight percentage, fiber volume fraction, CNTs aspect ratio and different fiber orientation on flutter pressure of delaminated reinforced composite plates are considered. According to the results, appending small amount of CNTs (4% wt) into the matrix epoxy can improve the flutter critical pressure by 33% in comparison to the neat matrix epoxy.     

Microstructure and Wear Behaviors of Plasma-Sprayed FeCrNiMoCBSi Coating with Nano-Grain Dispersed Amorphous Phase in Reciprocating Sliding Contact

A novel FeCrNiMoCBSi amorphous/nanocrystalline coating was fabricated using a plasma spraying process. The coating was dense with a low porosity of approximately 0.99%. The coating consisted of a 67.8 vol% amorphous phase coupled with many nanocrystalline grains that were approximately 5?nm in diameter. The mechanical properties of the as-sprayed coating were determined by nanoindentation measurement, and the tribological behaviors were systematically investigated in a reciprocating sliding contact. The results show that FeCrNiMoCBSi coatings possess superior wear resistance compared to other typically similar Fe-based amorphous coatings. The tribological behaviors evolve with the combination of normal load and sliding velocity. Herein, the dominant wear mechanisms are delamination wear and oxidation wear. With an increase in normal load and sliding velocity, the abrasive wear is gradually weakened, the formation of oxide films on the worn surfaces is facilitated, and wear debris is ground to powder. The oxide films suffer from fatigue wear with induced cracks undergoing reciprocating sliding effects.     

Dedicated drill design for reduction in burr and delamination during the drilling of composite materials

In the drilling of composite materials such as carbon fiber reinforced plastic, burrs and delamination occur during machining. This study proposed a design of a drill tool with a shape that suppresses burrs and delamination during the drilling of composite materials. The tool shape (tip, groove, land, etc.) is determined, and a nick shape that cuts off chips and reduces heat generation is adopted. A finite element analysis and an experimental evaluation involving 4600 holes were conducted. The maximum errors in the hole diameter and roundness were 15 μm and 0.016, respectively. Further, the maximum burr height was observed to be 80 μm or less, and delamination was not observed in the experiment.     

沿江山地城市景观照明设计理念及方法探究

城市景观照明是提升城市形象，促进旅游经济发展的重要策略。沿江山地城市特有的地域特征及空间形态不仅为创建山水园林式的景观照明风格提供了良好的条件，同时，又对景观照明设计师提出了新的挑战。对此，本文根据沿江山地城市的特点，从地域性及人文性方面对景观照明设计理念进行了探讨，并结合光度学及色度学的基本原理对景观照明中的亮化分级和光色分层进行了应用和理论分析，并提出了创建立体化城市夜景的新概念。文中针对沿江山地城市景观照明设计中易出现的问题，提出了科学的解决方法，以防止因生搬硬套，盲目效仿等不良设计风气所造成的负面效应。该文以突出绿色照明思想为中心，强调了技术与艺术的结合，为创意独具特色的沿江山地城市景观照明风格提供了应用和理论依据。     

全胶材料铅酸蓄电池的工业需求及设计

围绕电动自行车全胶材料铅酸蓄电池的工业需求及设计研发,从电池内部结构设计、生极板预处理工艺、胶体配方等多个方面进行了深入地研究,得到了大量可靠的实验结果.实验结果表明:全胶材料铅酸蓄电池可以满足电动自行车的工业需求,能够很好地解决电动自行车电池目前存在的问题,有效提高其使用性能.     

高模量碳纤维复合材料钻削力和加工缺陷分析

由于碳纤维复合材料独特的物理结构和化学性质,在其钻削加工中往往容易出现撕裂、毛刺、分层等缺陷,而这些缺陷与钻削参数以及钻削力息息相关。采用全因素实验研究了切削速度和进给速度对切削力以及钻削加工缺陷的影响。利用方差分析,对切削速度和进给量对实验结果的影响程度进行了分析。研究发现进给量是影响钻削加工最主要的因素,并且钻削轴向力和加工缺陷随切削参数的变化趋势基本一致。     

Nondestructive inspection of thermal barrier coating of gas turbine high temperature components

A thermal barrier coating (TBC) is applied to high‐temperature components in gas turbines, and consists of a ceramic topcoat and a metallic bondcoat. Various kinds of TBC degradation and damage occur in high‐temperature components during service, such as topcoat thinning, topcoat delamination, and formation of a thermally grown oxide (TGO) layer below the topcoat, each of which can be examined using a suitable nondestructive inspection technique. Topcoat thinning can be detected by topcoat thickness measurement using terahertz waves, which are electromagnetic waves in the frequency region between optical and radio waves. The measurement resolution is about 10 μm, which is comparable to microscopic observation of the cross section in destructive inspection. Topcoat delamination can be detected by active thermography, in which the topcoat surface is scanned by a heating laser and the surface temperature distribution is measured by a thermal infrared camera. The combination of temperature peak and residual thermal image detection is effective in eliminating false detection. The TGO layer can be detected using photoluminescence, in which the Cr³⁺ ions included as an impurity in Al₂O₃ are detected. Since delamination tends to occur at locations at which the TGO layer has grown, TGO layer detection provides an effective method to select regions where delamination has occurred or is likely to occur. An inspection flow based on these techniques is proposed, which is expected to aid the establishment of condition‐based maintenance strategies of high‐temperature components. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.