Friction and solid-solid adhesion on complex metallic alloys

The discovery in 1987 of stable quasicrystals in the Al–Cu–Fe system was soon exploited to patent specific coatings that showed reduced friction in ambient air against hard antagonists. Henceforth, it was possible to develop a number of applications, potential or commercially exploited to date, that will be alluded to in this topical review. A deeper understanding of the characteristics of complex metallic alloys (CMAs) may explain why material made of metals like Al, Cu and Fe offers reduced friction; low solid–solid adhesion came later. It is linked to the surface energy being significantly lower on those materials, in which translational symmetry has become a weak property, that is determined by the depth of the pseudo-gap at the Fermi energy. As a result, friction is anisotropic in CMAs that builds up according to the translation symmetry along one direction, but is aperiodic along the other two directions. A review is given in this article of the most salient data found along these lines during the past two decades or so.     

Adhesion of a rigid punch to a confined elastic layer revisited

The adhesion of a punch to a linear elastic, confined layer is investigated. Numerical analysis is performed to determine the equivalent elastic modulus in terms of layer confinement. The size of the layer relative to the punch radius and its Poisson’s ratio are found to affect the layer stiffness. The results reveal that the equivalent modulus of a highly confined layer depends on its Poisson’s ratio, whereas, in contrast, an unconfined layer is only sensitive to the extent of the elastic film. The solutions of the equivalent modulus obtained from the simulations are fitted by an analytical function that, subsequently, is utilized to deduce the energy release rate for detachment of the punch via linear elastic fracture mechanics. The energy release rate strongly varies with layer confinement. Regimes for stable and unstable crack growth can be identified that, in turn, are correlated to interfacial stress distributions to distinguish between different detachment mechanisms.     

Preparation of 2,4-dichlorophenoxyacetic acid loaded on cysteamine-modified polydopamine and its release behaviors

With dopamine as the monomer, the model pesticide 2,4-dichlorophenoxyacetic acid (2,4D) was loaded on cysteamine (NHSH)-modified polydopamine (PDA) nanospheres [2,4-dichlorophenoxyacetic acid bound to cysteamine-modified polydopamine (2,4D–PDA–NHSH)] via the construction of amide bonds. We investigated the materials’ structure, adhesive capability, and release behaviors, especially the mechanism of the release processes. The results demonstrate that the materials were spherical in appearance and adhesive. 2,4D loaded on the PDA vehicle was amorphous in structure. The amide bond between PDA and 2,4D generated by NHSH not only enhanced the loading amount of PDA from 296.28 to 692.56 mg/g but also decreased the thermal stability from 291 to 230 °C. The 2,4D–PDA–NHSH showed no pH responsiveness, whereas the PDA system without NHSH modification exhibited pH sensitivity. A mechanism for the observed behaviors was suggested. First-order, logistic, Weibull, and Korsmeyer–Peppas models were applied to describe the release behaviors at different pH values. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47469.     

轮船船体阴极保护控制系统的设计

轮船长期在海洋中航行,船体更容易受到微生物附着的损害。为了解决这一问题,本文提出了一种基于ARM的轮船船体外加电流阴极保护系统,当传感器监测到附着微生物达到一定数量时,系统就会将船体作为一个电极通以电流,此电流方向与腐蚀电流方向相反。并且,阴极提供自由氢的速度超过腐蚀菌去极化作用中利用氢的速度,同时阴极周围的pH升高至抑制硫酸盐还原菌生长繁殖的程度,最终达到保护船体的目的。     

核电用大口径闸阀关闭件发生热粘连的可能性分析

介绍了核电站用闸阀在高温条件下防止产生热粘连的结构要素,及其防止产生热粘连的理论分析。     

Study of the coating stability of a TBC system

Abstract

The degradation of thermal barrier coatings is closely linked to their spalling resistance which depends on the stability of the protective oxide scale produced by oxidation of the bond-coat. This study deals with a characterisation of the oxide layer, its interfaces with the bond-coat and the ceramic and their evolution during isothermal oxidation at 1,100°C. The microstructural evolution of the bond-coat, the outer part of the superalloy and the ceramic layer was also studied.     

Characterization of Chemical Densified Coating as Tritium Permeation Barrier

In a fusion blanket design, ceramic coating on structural materials has been considered to be used as a tritium permeation barrier. The Chemical Densified Coating (CDC) method has some advantage compared with another coating method. This method is capable to form densified coating on either the outer or the inner surface of a tube or a container. This process temperature is low (450°C). The fabrication technique of Cr₂O₃-SiO₂ coating had been developed using CDC method. However, Cr₂O₃-SiO₂ coating had open pores in the coating. For filling open pores, the densification treatment by CrPO₄ was examined. In this study, the verification of open pores, the thermal shock resistivity, the adhesion strength and the deuterium permeability were evaluated and compared with Cr₂O₃-SiO₂ (Type 1) coating and Cr₂O₃-SiO₂ including CrPO₄ (Type 2) coating. From these results, it was confirmed that Type 2 coating had a good adhesion property, and permeation reduction factor of SS316 with Cr₂O₃-SiO₂ including CrPO₄ coating reached about 1,000 at 600°C.     

转锈稳锈材料在石油钻采设备薄壁件表面的应用

石油钻采设备中存在部分薄壁板件(厚度不超过3 mm),在喷砂或喷丸过程中极易造成变形,故实际生产中只能手工打磨清理。但是手工打磨效率较低,且一旦手工清理不彻底,会影响产品的防腐质量。为提升石油钻采设备中薄壁防腐质量,引进了新材料——转锈稳锈材料。通过控制变量,使用拉拔仪检测不同变量下涂层附着力;对转锈稳锈材料和传统的手工处理进行比较,考察其对不同品牌的油漆是否具有兼容性。研究结果表明:转锈稳锈材料与传统的手工打磨清理相比在增加漆膜附着力方面更具有优势,而且与大多数的油漆具有兼容性。