Co元素对硬质合金基底金刚石涂层膜基界面结合强度的影响

采用基于密度泛函理论的第一性原理平面波赝势方法, 研究了硬质合金刀具基底黏结相Co元素对金刚石涂层膜基界面结合强度的影响机理. 借助Materials Studio软件建立了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型, 采用CASTEP仿真软件计算了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型的最优稳定结构. 通过仿真计算, 获得了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型的界面结合能、电荷密度图及Mulliken重叠布居数. 经对比分析后发现, 硬质合金基底中磁性元素Co的存在能转移金刚石涂层膜基界面处W元素及C元素的电荷, 从而使膜基界面处的原子因失电荷而相斥, 这直接导致了金刚石涂层膜基界面间距变大, 使得金刚石涂层膜基界面结合能降低.     

粘着摩擦系数的分形几何研究

计及作用于接触斑点上的切向力，通过比较作用于接触斑点上的法向弹性载荷与法向塑性载荷，确定了区分弹性接触与塑性接触区域的临界接触斑点面积．总的粘着摩擦系数被表示为弹性接触区与塑性接触区的粘着摩擦系数的组合．假设屈服压力及局部粘着摩擦系数不依赖于接触斑点且等于塑性接触区中的平均值，则总的粘着摩擦系数可用简单的表达式描述．分形几何参数及归一接触面积对于粘着摩擦系数的效应已通过算例表明，研究中，分别考虑了忽略与计及接触斑点的微粒间的相互作用，两种情况的结果完全不同．     

Single-particle motion in the strongly coupled one-component plasma

We present molecular dynamics computations of the time-dependent auto-correlation function of the single-particle density in a classical one-component plasma for three thermodynamic states in the range of intermediate and strong coupling. The deviations from the Gaussian approximation are calculated and the data are analyzed by the standard memory function formalism.     

铝合金表面复合陶瓷防火涂层的制备及性能研究

以无机胶粘剂及陶瓷粉体为原料,制备用于地铁内饰的铝合金板表面阻燃陶瓷涂层.研究了胶粘剂、无机阻燃剂的加入量及料浆粒度与涂层致密度的关系.按照饰面型防火涂料的国家标准(GB12441-2005)和材料非燃性的英国标准(BS476-4)对涂层的理化性能进行检测.结果表明:当粘结剂的用量为60;、添加剂粒度为1～2 μm时,涂层表面均匀、致密、无缩孔.所制备的陶瓷涂层均达到上述标准.涂层的耐火极限高于30 min,不燃,不脱落,无烟,不产生有毒的气体,具有很好的防火阻燃作用.     

Effect of fibril arrangement on crack trapping in a film‐terminated fibrillar interface

We present a three‐dimensional (3D) model for adhesion enhancement due to crack trapping in a film‐terminated fibrillar structure. Adhesion enhancement occurs due to trapping of the interfacial crack in the region between fibrils. Energy release to the crack tip is attenuated because, between fibrils, it has to pass through the compliant terminal film. Using perturbation theory and a finite element method, we solve for the shape of crack front, which is unknown. Our model thus also allows us to study how adhesion enhancement depends on the arrangement of fibrils. For example, our model explains why, for a fixed area density of fibrils and for similar crack orientations, hexagonal arrays have higher adhesion than square arrays. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2368–2384, 2009     

耐高温高塑性应变高聚物及其酰亚胺化特征

本文介绍了最近研制成功并用于材料热强度应变测量、耐热300℃、灵敏系数K>1.85和应变极限ε>8％,具有独特力学性能的耐高温高塑性(大)应变胶粘剂。以Ⅳ号胶为代表着重研究了这些溶液型共聚-共混聚酰胺酸在热酰亚胺化为最终产物过程中,各个阶段的特征及对性能的影响。结果发现,急剧酰亚胺化(155℃附近)之后,聚合物的T(>280℃)便已接近最大值,认为继续的酰亚胺化反应至完全(225℃附近)是在软玻璃态中进行的。文中确定了该胶粘剂呈现优良应变特性和粘结性的热-酰亚胺化温度是250—260℃。     

Investigation of a resorcinol–formaldehyde resin by 13C-NMR spectroscopy and intrinsic viscosity measurement

Various molecular weight fractions and oligomers isolated from a novolac type resorcinol–formaldehyde (RF) wood adhesive resin were studied by ¹³C-NMR, gel permeation chromatography (GPC), and intrinsic viscosity measurements. The ¹³C-NMR results indicate that methylene groups occur mostly between C₄–C′₄ and C₂–C′₄ carbons and in minor amounts between C₂–C′₂ carbons of resorcinol rings. By suppressing the nuclear Overhauser effect (nOe) and using a long delay time for ¹³C-NMR measurements, reasonable methylene/aromatic carbon ratios were obtained from the aromatic C₁ carbon patterns that have resulted from different numbers of methylene groups bonded on the aromatic ring. This analysis results indicate that the RF resin has an appreciable amount of branch structures and compare favorably with the gel permeation chromatography and intrinsic viscosity measurement results. © 1993 John Wiley & Sons, Inc.     

周期激励下单搭接接头强度与振动特性研究

主要研究汽车轻量化粘接结构在周期性振动载荷激励下强度与振动属性的改变。首先,利用实验手段,研究了振动载荷对单搭接接头疲劳特性的影响,分析了疲劳后接头的强度及模态频率的变化;其次,通过仿真分析方法,建立了基于经典双线性内聚力模型(Cohesive Zone Model)的单搭接接头静态及动态仿真模型,对胶接接头的模态频率、振型及加载开裂过程中胶层单元失效扩展进行模拟,与此同时,探讨了疲劳载荷对胶层内聚力模型的弱化效应。最后,利用SEM电镜分析手段,从微观上分析了粘接接头疲劳损伤及断裂机理。     

混凝土裂缝的仿生自修复研究与进展

混凝土仿生自修复是根据生物体损伤修复的原理, 在混凝土传统组分中复 合特殊组分使其具有自修复功能, 当混凝土材料出现损伤或裂缝时, 自动触发修复反应使其 愈合, 恢复甚至提高开裂部分的强度, 从而提高整个结构的性能. 混凝土自修复系 统将免去有效的监听和外部修补所需的高额费用, 节省建筑结构运行费用, 且大大有利于建筑结构的 安全性和耐久性. 本文在简要介绍生物体损伤修复原理的基础上, 总结了两种混凝土自 修复技术与方法; 综述了国内外有关裂缝自修复混凝土的研究现状; 分析了仿 生自修复方法中所存在的问题及其实用价值, 展望了其发展趋势和应用前景; 最后, 指出需 进一步研究的方向.     

In Vitro and In Vivo Characterization of Biodegradable Reactive Isocyanate‐Terminated Three‐Armed‐ and Hyperbranched Block Copolymeric Tissue Adhesives

Tissue adhesives are an attractive class of biomaterials, which can serve as a treatment for meniscus tears. In this study, physicochemical and adhesive properties of novel biodegradable three‐armed‐ and hyperbranched block copolymeric adhesives are evaluated. Additionally, their degradation in vitro and in vivo, and the tissue reaction after subcutaneous injection in rats are assessed. The developed adhesives have sufficient adhesive strength to meniscus tissue after curing (66–88 kPa). Networks based on the three‐armed adhesive have tensile properties that are in the same range as human meniscus. After 26 weeks, networks based on the hyperbranched adhesive show a faster mass loss (25.4%) compared to networks prepared from the three‐armed ones (5.5%). Both adhesives induce an inflammatory reaction, however, no necrosis and only initial toxic effects on peripheral tissues are observed. The proposed materials are suitable candidates for the use as resorbable tissue adhesives for meniscus repair.