Wetting of Ceramic Oxides by Molten Metals Under Ultrahigh Vacuum

Contact angles, surface free energies, and work of adhesion were determined by a sessile drop technique for the wetting of MgO, Al₂O₃, and SiO₂ by In, Ga, and Sn at 10^-10 torr. The surface free energies of In, Ga, and Sn were 540, 632, and 573 ergs/cm² (±5%), respectively, at their melting points. Works of adhesion and equilibrium contact angles for wetting of MgO by In are 172 ergs/cm² and 133° by Ga, 356 ergs/cm² and 116° by Sn, 278 ergs/cm² and 121°. For wetting of Al₂O₃ by In, they are 237 ergs/cm² and 124° by Ga, 226 ergs/cm² and 130° by Sn, 257 ergs/cm² and 123°. For wetting of SiO₂ by In, they are 208 ergs/cm² and 128° by Ga, 260 ergs/cm² and 126° by Sn, 252 ergs/cm² and 124°.     

Interfacial Reactions and Wetting Behavior of Glass-Iron Systems

Interfacial reactions and enhanced wetting or spreading of Na₂Fe_xSi₂O_5+x and Na_2–2xFe_xSi₂O₅ glasses on substrates of high-purity (Marz) and commercial (Armco) iron were observed at 1000°C at low partial pressures of O₂ and Na. Reactivity increased with increasing O/Si ratio in the glass, with the purity of the iron, and with decreasing gas pressure.     

Wetting of Ceramics by Liquid Metals

A linear relation is established between the cosine of the contact angle and the temperature of a liquid metal sessile drop resting on a ceramic substrate. This relation is demonstrated for many liquid metal/ceramic systems. The work of adhesion and the effects of surface roughness, porosity, chemical reactions, and structural transformations in the substrate surface are also discussed.     

Interfacial Bonding and Thermal Expansion of Fibre-Reinforced Composites

The present work examines the effect that the fibre-matrix bond strength has on longitudinal and transverse thermal expansivities of unidirectional glass fibre and carbon fibre-reinforced epoxies. It is shown that the weakening of the interfacial bond results in an increase of the longitudinal coefficient of thermal expansion, and a decrease of the transverse one. The results are explained in terms of the reinforcement efficiency factor, according to a theory proposed elsewhere.⁴     

Interfacial Contact and Bonding in Autohesion II-Intermolecular Forces

The second stage of autohesion involves bond formation after contact is established by elastic, viscous, or viscoelastic deformation of the surfaces. The interfacial bonding for polystyrene is mainly through van der Waals intermolecular forces. Molecular repeat units across the interface interact to yield an attractive force. The intermolecular forces are derived from a 6–12 Lennard-Jones potential. The two unknown constants for this potential are determined from the equilibrium distance and comparison of the computed lattice energy with the cohesive energy.     

Interfacial Contact and Bonding in Autohesion I-Contact Theory

A two stage theory, consisting of contact establishment as the first, and bond formation as the second stage, is proposed for autohesion. A viscoelastic contact theory is worked out based on the shape of the surfaces, the contact pressure, and the temperature. Contact of two spheres of polystyrene and a practical surface consisting of cylinders and flats are analyzed mathematically by extending the classical Hertz elastic contact problem by employing elastic-viscoelastic analogy developed by Alfrey and Gurnee. Karam's fourteen element generalized Voigt model is used for computations.     

Interfacial Contact and Bonding in Autohesion II-Intermolecular Forces

The second stage of autohesion involves bond formation after contact is established by elastic, viscous, or viscoelastic deformation of the surfaces. The interfacial bonding for polystyrene is mainly through van der Waals intermolecular forces. Molecular repeat units across the interface interact to yield an attractive force. The intermolecular forces are derived from a 6-12 Lennard-Jones potential. The two unknown constants for this potential are determined from the equilibrium distance and comparison of the computed lattice energy with the cohesive energy.     

Interfacial Contact and Bonding in Autohesion I-Contact Theory

A two stage theory, consisting of contact establishment as the first, and bond formation as the second stage, is proposed for autohesion. A viscoelastic contact theory is worked out based on the shape of the surfaces, the contact pressure, and the temperature. Contact of two spheres of polystyrene and a practical surface consisting of cylinders and flats are analyzed mathematically by extending the classical Hertz elastic contact problem by employing elastic-viscoelastic analogy developed by Alfrey and Gurnee. Karam's fourteen element generalized Voigt model is used for computations.     

陶瓷与金属的连接方法

特种陶瓷作为一种新兴的结构材料,具有耐腐蚀、高硬度、耐高温等特点.如何实现陶瓷与金属的可靠连接是发挥陶瓷材料作用的关键.从原子结构和物理化学匹配性两个方面分析了陶瓷与金属连接的特点,并介绍了常用的陶瓷与金属的连接方法,包括钎焊、固相扩散连接法、过渡液相连接法、反应成形连接法和自蔓延高温合成连接法等,重点介绍了他们的原理、特点、适用范围.在此基础上对陶瓷与金属的连接方法进行了综述和展望.     

Interfacial Bonding and Environmental Stability of Polymer Matrix Composites

Recently developed adsorption-interdiffusion (A-I) theory of adhesion is employed to isolate the (London) dispersion γ_i,j^d and (Keesom) polar γ_i,j^p components of the excess interfacial free energy γ_i,j=γ_i,j^d+γ_i,j^p at the fiber-matrix interface in polymer matrix composites. For adsorption bonded interfaces the theory defines a new method of mapping the surface energy effects of an immersion phase upon the Griffith fracture energy γ_G. The stability of interfacial bonding between graphite fiber-epoxy matrix is defined in terms of the theoretical model and experimentally evaluated by accelerated aging studies which monitor changes in fracture energy for crack propagation perpendicular to the fiber axis. Applications of the model to control fiber surface treatments and select matrix components for optimized bond strength and environmental resistance is discussed.     

Interfacial Bonding and Environmental Stability of Polymer Matrix Composites

Recently developed adsorption-interdiffusion (A-I) theory of adhesion is employed to isolate the (London) dispersion γ_i,j ^d and (Keesom) polar γ_i,j ^p components of the excess interfacial free energy γ_i,j=γ_i,j ^d+γ_i,j ^p at the fiber-matrix interface in polymer matrix composites. For adsorption bonded interfaces the theory defines a new method of mapping the surface energy effects of an immersion phase upon the Griffith fracture energy γ_G. The stability of interfacial bonding between graphite fiber-epoxy matrix is defined in terms of the theoretical model and experimentally evaluated by accelerated aging studies which monitor changes in fracture energy for crack propagation perpendicular to the fiber axis. Applications of the model to control fiber surface treatments and select matrix components for optimized bond strength and environmental resistance is discussed.     

Interfacial Chemistry of an Aluminum-to-EPDM Rubber Bonding System

During recent assessment of aging in aluminum-to-rubber bonds on stored solid rocket motors, corrosion and minor insulator debonds were observed. A test was conducted to study the progressive effect of exposure to high humidity on the bondline; elevated temperature was used to accelerate the aging. In a parallel test, samples were held at elevated temperature in a dry atmosphere. The test results were compared with the analyses of corroded and noncorroded hardware samples. The predominant corrosion product detected at the bondlines was aluminum oxide/hydroxide. In general, there was a very good correlation between the Cl:Al atomic percent ratio calculated from X-ray photoelectron spectroscopy analysis of the ruptured bondline surfaces and the visual characterization of the extent of corrosion. The Cl:Al ratio, which represented the ratio of primer to corrosion product at the locus of failure, varied from 0.4 to 47. The implications for metal-to-rubber bond fabrication and storage are discussed.     

Interfacial Chemistry of an Aluminum-to-EPDM Rubber Bonding System

During recent assessment of aging in aluminum-to-rubber bonds on stored solid rocket motors, corrosion and minor insulator debonds were observed. A test was conducted to study the progressive effect of exposure to high humidity on the bondline; elevated temperature was used to accelerate the aging. In a parallel test, samples were held at elevated temperature in a dry atmosphere. The test results were compared with the analyses of corroded and noncorroded hardware samples. The predominant corrosion product detected at the bondlines was aluminum oxide/hydroxide. In general, there was a very good correlation between the Cl:Al atomic percent ratio calculated from X-ray photoelectron spectroscopy analysis of the ruptured bondline surfaces and the visual characterization of the extent of corrosion. The Cl:Al ratio, which represented the ratio of primer to corrosion product at the locus of failure, varied from 0.4 to 47. The implications for metal-to-rubber bond fabrication and storage are discussed.     

Fundamentals of Glass-to-Metal Bonding: VIII, Nature of Wetting and Adherence

The sessile-drop method for the evaluation of wetting is discussed in terms of forces acting on the liquid drop. For acute angles, or wetting of the solid, the driving force is the lowering of the solid-gas surface energy by the liquid. Contact angles of approximately 25° and less, obtained under appropriate conditions, appear to be associated with interfacial conditions that lead to the development of a strong chemical bond (an interchange or sharing of electrons) and to good adherence. A theory is proposed whereby chemical bonding depends on the development of a balance of bond energies across the metal-glass interface. The factors that lead to this condition are discussed. A modified Dupre's equation to take into account a strain factor and a contact coefficient is developed. Bonding of Na₂Si₂O₅ molten glass to platinum, gold, and iron and oxidized iron in several atmospheres is discussed.     

润湿分散剂对聚氨酯底漆漆膜界面行为的影响

针对出现漆膜中长期发白现象的涂装养护环境，提出与其具有高度相关性的实验室模拟研究方法，探讨了润湿分散剂对聚氨酯(PU)底漆漆膜发白现象的影响；并通过扫描电子显微镜(SEM)、电子能谱仪(EDS)、X光电子能谱仪(XPS)等测试工具，对润湿分散剂添加前后PU底漆的漆膜界面行为进行了比较分析，对漆膜中长期发白的机理进行了初步探讨。     

Synthesis and Bonding Performance of Conductive Polymer Containing Rare Earth Oxides

Herein, a conductive polymer material containing rare earth oxide (PEG–LiX–CeO₂) was designed and synthesized. The bonding performance of the conductive polymer was analyzed via AC impedance, X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), tensile strength, ball milling and anodic bonding experiments. The AC impedance, XRD and FTIR experiments demonstrate that the introduction of alkali metal lithium salt and cerium oxide (CeO₂) can effectively reduce the crystallinity of the composites and increase the ion migration. The results of ball milling show that increasing the milling time (<?10 h) and speed (<?250 r min^?1) can improve the conductivity of the composites. The anodic bonding experiment of PEG–LiClO₄–CeO₂ with AL foil and the SEM characterization of the bonding interface demonstrate the existence of a well-defined bonding layer between the bonding interface.     

Structure of High-Angle Grain Boundaries in Metals and Ceramic Oxides

The current knowledge of the structure of high-angle grain boundaries in metals and ceramic oxides is critically reviewed. Particular attention is given to effects due to differences in the bonding and crystal structure in these solid types. The results of recent experimental work and efforts to model grain-boundary structure using computer simulation methods are described. Important characteristic features of boundaries in these materials are discussed. Difficulties which are presently being encountered in efforts to determine their structure are pointed out.     

Interfacial Contact and Bonding in Autohesion: III-Parallel Plate Attraction

Interfacial bonding force at the interface of polystyrene is computed by considering interaction of repeat units constituting molecules on the two sides. The interaction force between the repeat units is obtained from the 6–12 Lennard-Jones potential curves determined previously. The maximum value of the bonding force is of the same order of magnitude as the yield stress. Results indicate that regions in the immediate vicinity of flat regions where separation is within about 20A contribute to the overall strength of the bond.     

Interfacial Contact and Bonding in Autohesion: III-Parallel Plate Attraction

Interfacial bonding force at the interface of polystyrene is computed by considering interaction of repeat units constituting molecules on the two sides. The interaction force between the repeat units is obtained from the 6-12 Lennard-Jones potential curves determined previously. The maximum value of the bonding force is of the same order of magnitude as the yield stress. Results indicate that regions in the immediate vicinity of flat regions where separation is within about 20A contribute to the overall strength of the bond.     

Rheological Properties of Short Polyester Fiber-Polyurethane Elastomer Composite with Different Interfacial Bonding Agents

The rheological behavior of a short-polyester-fiber-filled polyurethane elastomer composite containing different bonding agents has been studied in the temperature range 120–160°C and in the shear rate range 63–608s^?1. The composite with and without bonding agents showed a pseudoplastic behavior which decreased with the increase of temperature. Composites containing bonding agents based on polypropyleneglycol and 4,4′-diphenylmethane-diisocyanate showed the lowest viscosity values at a particular shear rate, whereas composites containing a glycerol-(GL) based bonding agent showed the highest viscosity. The viscosity of the composite decreased sharply after a particular temperature (140°C) and the fall was less drastic in the composite containing a GL-based bonding agent.