Ag-CuO钎料与BaCo0.7Fe0.2Nb0.1O3-δ透氧膜陶瓷润湿及界面反应机理的研究

利用座滴法润湿实验,借助SEM和EDS测试,研究了Ag-CuO钎料与BaCo0.7Fe0.2Nb0.1O3-δ透氧膜陶瓷润湿及界面反应机理。结果表明Ag-Cu-O/BCFNO间的润湿遵从界面反应润湿机制,随Cu含量增加和温度升高,润湿角快速减小。当Cu含量为3.3%(摩尔分数)时,在界面处BCFNO侧开始生成1层反应层,反应层的存在降低了固液界面能,使界面润湿性得到改善,相互冶金作用增强。反应层产生的原因是界面处发生了界面反应CuOx+BaCoFeNbO→Ba-Cu-O+Co-Cu-O,生成的复杂氧化物Ba-Cu-O、Co-Cu-O在BCFNO基体的晶粒边界上呈岛状分布。     

Diffusion-limited reactive wetting: effect of interfacial reaction behind the advancing triple line

Using the “dispensed drop” variant of the sessile drop technique, spreading kinetics of dilute Cu–Cr alloys on smooth vitreous carbon substrates are measured under helium microleak conditions. In this system, it is known that the drop spreading rate is controlled by diffusion of the reactive atom species (Cr) from the bulk liquid to the triple line, where wetting is induced by formation of an interfacial layer of chromium carbide. Microstructural characterization of rapidly cooled drops shows that growth of the interfacial reaction product layer continues behind the moving solid–liquid–vapor triple line. The spreading velocity is modeled by finite-difference numerical analysis of diffusion near the triple line in the presence of continued interfacial reaction, simplifying the growth rate as being constant and using realistic parameter values. We show that continued interfacial reaction explains the dependence of the triple line spreading rate on the instantaneous wetting angle that is observed in this system.     

Effect of Nb on the Interfacial Wettability in A12O3／Medium Mn Steel

To develop medium Mn steel (MMS) matrix composites reinforced by Al2O3 particles, the effect of Nb on the interfacial wettability of Al2O3/MMS and its mechanism were investigated in this paper. The results show that the wetting angle of the specimens with different Nb contents are bigger than that of the specimen without Nb at the first stage, and then decreases with time at 1450 ºC. At certain time, the wetting angle is lower than that of the specimen without Nb. At 1550 and 1600ºC, the wetting angle of the specimens containing Nb decreases quickly with time at first stage. After 10 min, the wetting angle reaches a steady state, and hardly changes with time. The mechanisms of Nb to improve the wettability can be attributed to the enrichment of Nb at the interface and Nb serves as surface active agent of MMS at T<1550ºC, and as catalyzer for the interfacial reaction of Al2O3/MMS at T≥1550ºC, and reduces the interfacial energies.     

Effect of localized redox equilibria on adhesion between gold and thick-film dielectrics

The effect of processing atmospheres with decreasing partial pressure of oxygen on the stability of dielectric glass formers and on the wetting between gold and dielectrics was studied. Thermodynamic calculations, contrasted with experimental results, suggest that localized redox conditions may differ from ideal thermodynamic equilibria. As the redox equilibrium shifts towards reducing conditions, a compositional change occurs and affects the interfacial energies. Screen-printed gold combined with a lead-borosilicate glass dielectric becomes non-wetting when fired in nitrogen gas.     

Effects of diffusion on interfacial fracture of gold-chromium hybrid microcircuit films

In this study, the effects of diffusion on gold-chromium film durability was determined from interfacial fracture energy measurements on laboratory samples aged to simulate long term service. The samples were prepared by sputter deposition of gold films and chromium adhesive layers on sapphire substrates. Some films were left in the as-deposited condition while others were given an accelerated age to drive the chromium off the interface and into the gold film. Stressed overlayers and nanoindentation were then used to induce interfacial delamination and blister formation from which interfacial fracture energies were determined using mechanics-based models. These tests showed that the fracture energies for interfacial failure of the as-deposited and annealed films occurred near 1.3 J m^–2 even when diffusion had driven all chromium into solution. These results clearly demonstrate that chromium in solution is as effective in promoting adhesion as continuous chromium adhesive layers.     

The influence of interfacial wetting and adhesion on the formation of voids at metal-ceramic interfaces

High temperature sessile drop experiments were conducted to evaluate the wetting (contact angle, surface/interface energies) on the basal C and prismatic A surfaces of sapphire by pure liquid Ni, and Ni alloyed with Al or S. After solidification of the drops, inspection of samples showed the presence of millimetre-sized voids at the interface between pure nickel and the basal surface of the sapphire substrate. However, no voids were found at the interfaces of pure Ni with the prismatic surface of sapphire, or at the interfaces of sapphire with Ni alloyed with 0.03at.%S or 2at.%Al, or if the pure Ni drops were significantly smaller in size. It is proposed that the voids form to release strain energy stored in the system, due to the dissimilar thermal expansion coefficients of Ni relative to sapphire. Alloying with Al and/or S retards interfacial void formation by enhancing the metal-ceramic interfacial wetting and adhesion.     

Coarsening Kinetics of γ' Precipitates in Dendritic Regions of a Ni_3 Al Base Alloy

Coarsening behavior of γ' precipitates in the dendritic regions of a Ni 3 Al base alloy containing chromium,molybdenum,zirconium and boron was investigated.Annealing treatment was performed up to 50 h at 900,1000 and 1100℃.The alloy was produced by vacuum-arc remelting technique.Results show that coarsening of the γ' precipitates in this complex alloy containing high volume fractions of γ' phase follows Lifshitz-Slyozov-Wagner(LSW) theory.Coarsening activation energy of the γ' precipitates was evaluated to be about 253.5 kJ.mol-1 which shows that the growth phenomenon is controlled by volume diffusion of aluminum.With an innovative approach,diffusion coefficient of the solute element(s) and the interfacial energy between γ' precipitates and γ'(matrix) were estimated at 900,1000 and 1100℃.Accordingly,the interfacial energies at 900,1000 and 1100℃ are 4.49±1.48,2.08±0.69 and 0.98±0.32 mJ.m-2,respectively.Also the diffusivities of solute element(s) at these temperatures are 3.41±1.08,30±9.5 and 145.15±45.85(10-15 m-2.s-1),respectively.     

Wettability and Bonding between Ni and Ti(C, N) with Multiple Carbide Additions

The wettability and bonding in Ni/Ti(C, N) systems with multiple carbide additions were studied by sessile drop technique and vacuum brazing technique, respectively. The phase characterizations of substrates and fracture surfaces were conducted by XRD. The microstructures at metal/ceramic interfaces and fracture surfaces were observed via SEM in back scattered mode and second electron mode, respectively. Furthermore, an X-ray energy-dispersive spectrometer (EDS) attached to SEM was used to study the elements diffusion in interfacial regions. The results reveal that diffusion and dissolution mechanism controlled reactive wetting takes place in the system in high temperature wetting. Results also show that the contact angles decrease with multiple carbide additions, and the effect of multiple carbide additions is stronger than that of single additions. The contact angle reaches the lowest value in the lowest TiC content case. The enhancement of the wettability is due to alloying procedure during high tempe     

Lateral diffusion of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate at the interfaces of C18 and chromatographic solvents

The influence of mobile phase on the lateral diffusion of an amphiphilic dye was studied for four chromatographic interfaces using fluorescence correlation spectroscopy. The fluorescent dye was DiI (1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate); the stationary phase was a covalently bonded monolayer of dimethyloctadecylsiloxane on fused silica; and the four mobile phases were acetonitrile, methanol, tetrahydrofuran, and water. Time-resolved measurements at varying focal positions of the microscope confirmed negligible fluorescence from solution. Single-molecule spectroscopy showed that exchange between mobile and immobile adsorbates was negligible. The lateral diffusion of DiI was the fastest for tetrahydrofuran, D = 5.3 x 10(-5) cm2/s, and slowest for water, D = 2.5 x 10(-6) cm2/s. Methanol and acetonitrile gave intermediate rates of diffusion, D = 3.4 x 10(-6) and 4.8 x 10(-6), respectively. There was no correlation of the lateral diffusion coefficient with solvent viscosity, a weak correlation with interfacial tension, and a strong correlation with 13C NMR line shapes for the terminal methyl group of the hydrocarbon chain. The increased wetting of the C18 interphase in the order water < methanol < acetonitrile < tetrahydrofuran agreed with data for the miscibility of these solvents with n-hexadecane. It is concluded that the wetting of the hydrocarbon interphase by the mobile phase enhances the lateral diffusion of the amphiphile.     

Wetting and evaporation behaviors of molten Mg–Al alloy drops on partially oxidized α-SiC substrates

The wetting and evaporation behaviors of Mg–Al alloys over a full composition range on partially oxidized polycrystalline α-SiC substrates were studied in a flowing Ar atmosphere using an improved sessile drop method. The time dependence of the changes in contact angle and drop geometry was monitored and representative wetting stages were identified. The initial contact angles at 1173 K were 100° for pure Al and 76° for pure Mg, with the maximum value of 106° for the 7.6 mol.% Mg–Al alloy. The interfacial reaction and the evaporation of Mg led to the decrease in the apparent contact angle in the spreading stage and their respective contribution was evaluated. After the pinning of the triple line, the decrease in the contact angle resulted from the diminishing drop volume as a consequence of the Mg evaporation. The effects of Mg concentration on the wetting and evaporation behaviors were discussed. A mechanism for the time-dependent diminishing drop volume was proposed in light of the competition between the Mg evaporation and its diffusion from the drop bulk to the surface. Finally, the interfacial reaction was analyzed based on thermodynamic considerations.     

Supermodulus effect by grain-boundary wetting in nanostructured multilayers

The effect of thermal treatments on mechanical properties was systematically investigated in Ni/Mo multilayers with a constant modulation period(160 nm)prepared by magnetron sputtering deposition.A supermodulus effect was found in the annealed multilayers as compared to the as-deposited state.A large tensile stress development was observed in the multilayers.The evolution of grain-boundary(GB)wetting was observed at the interfaces of the multilayers,which results in an enhanced modulus based on the mechanism of GB-wetting-induced interfacial stress/strain.The GB wetting phenomenon was further supported by a thermodynamic calculation.The results not only bring clear evidence of the important role of interfacial structures in governing the elastic behavior of metallic multilayers,but also allow designing the multilayers with special properties through atomic diffusion and wetting at the interfaces based on the thermodynamic calculation.     

Spreading kinetics of liquid metals on mild steel

Abstract

The kinetics of the spread of molten copper, Cu–Mn alloy, and aluminium on solid mild steel were investigated at temperatures from 800 to 1100°C under an anhydrous borate flux. The molten copper and Cu–Mn alloy seem to spread largely by surface diffusion and the spread of molten aluminium follows linear kinetics. The spread coefficient, interfacial tension, and work of adhesion are evaluated from the relationship between an observed rate constant and Yin's theoretical formulism. The spread of molten copper on mild steel indicates complete wetting, while the spread of molten aluminium shows the least wetting. In the aluminium–mild steel spread system, the spread tends to increase with temperature: with increasing temperature, the spread coefficient increases and the interfacial tension decreases, while the work of adhesion remains much the same.

MST/743     

Wettability and spreading kinetics of liquid aluminium on boron nitride

The wettability and spreading kinetics of liquid AI on CVD-BN were investigated by the sessile drop method in a vacuum of about 1.1×10⁻³ Pa at 1070 to 1430 K. The wettability on the Al-BN system was different from that of the Al-SiC system reported in the literature. The wetting angle of Al-BN linearly decreased with an increase of temperature in high temperature range, and tended towards 15° at 1430 K. Complete wetting could be obtained at about 1470 K. The interface energy between liquid Al and the reaction layer and the surface energy of CVD-BN were calculated by means of Warren thermodynamics analysis. The surface of CVD-BN was examined by XRD. The results show that the surface of CVD-BN was chiefly composed of those low energy planes parallel to (001). According to the relationship of the spreading kinetics from the experiments, the apparent activation energy of the liquid Al spreading on the surface of CVD-BN was calculated. The result shows that the activation energy of interfacial reaction accounts for about 54% of the spread activation energy. The spread of liquid Al on CVD-BN was affected by the interfacial reaction, diffusion and liquid movement on the surface.     

Interdiffusion reaction in the PZT/PNN functionally gradient piezoelectric ceramic materials

The interfacial diffusion reaction between lead zirconate titanate (PZT) and lead nickel niobate (PbNi1/3Nb2/3O3:PNN) phases in the PZT/PNN functionally gradient piezoelectric ceramics were investigated as a function of the diffusion temperature and time, respectively. The ionic composition distribution profiles in the interdiffusion region were examined by electron probe microbeam analysis (EPMA). Based on a diffusion model of the overlapped diffusion solution from thin slab, the numerical simulation for the ionic composition distribution was carried out by computer, which was in agreement with the EPMA result. The diffusion coefficients for the Ni2+, Nb5+, Ti4+ and Zr4+ ions were determined, which were 33.8, 22.6, 10.8 and 9.9×10-12 m2 s-1, respectively. The apparent activation energies for these ions were 94.4, 171.7, 257.5 and 325.8 kJ mol-1, respectively. The differences in the ionic diffusion coefficients and apparent activation energies were discussed from the viewpoint of the crystal chemistry. © 1998 Chapman & Hall     

Wetting Behaviors and Interfacial Reaction between Sn-10Sb-5Cu High Temperature Lead-free Solder and Cu Substrate

Sn-10Sb-5Cu lead-free solder was fabricated for high temperature application in electronic package. Wetting behaviors and interfacial reaction between such a high temperature lead-free solder and Cu substrate were investigated and compared with those of 95Pb-Sn solder. The results showed that the wetting properties of Sn-10Sb-5Cu solder are superior to those of 95Pb-Sn solder in maximum wetting force, wetting time and wetting angle in the temperature range of 340-400 ℃. However, the surface of the Sn-10Sb-5...     

A criterion for optimum adhesion applied to fibre reinforced composites

The effects of physical adhesion on the mechanical properties of a composite structure are examined in this work. A criterion for optimum adhesion between matrix and reinforcing fibres is proposed based on maximizing the wetting tension. It is shown that the maximum wetting tension criterion best fulfils two important requirements for a strong interface:(i) the physical interactions at the molecular level between the resin and the fibres must be maximized, and (ii) the liquid resin must spontaneously wet the fibre surface in order to minimize the flow density at the interface. The conditions on the surface energy of the various phases leading to maximum wetting tension are analysed considering three mixing rules: two based on dispersive–polar interactions, and a third one based on acid–base interactions. The optimum adherend for a given adhesive, and the optimum adhesive for a given adherend, are examined. The analysis shows that maximum wetting tension is obtained when the substrate and adhesive surface energies are very high and equal, so that their polar and dispersive components are equal when the polar–dispersive mixing rule is used, and e.g. their Lifshitz–van der Waals’ components are equal and the acid component of one phase is equal to the basic component of the other phase when the acid–base approach is considered. It is shown using data from the literature that interfacial strength correlates with the wetting tension for fibre reinforced composites. Additional observations show that under poor wetting conditions the voids tend to concentrate at the fibre–resin interface, whereas under favourable wetting conditions they tend to coalesce in regions away from the fibre surface. This revised version was published online in November 2006 with corrections to the Cover Date.     

Stability of strained thin films with interface misfit dislocations: A multiscale computational study

The stability of thin single-crystal, internal-defect-free Fe films on Mo(110) and W(110) substrates is investigated through calculations of energetics including contributions from the misfit strain, interfacial misfit dislocations, film surface and interface. The misfit dislocation model is developed through the Peierls-Nabarro framework, employing ab initio calculations of the corrugation potential at the film/substrate interface as an input to the model. The surface and interfacial energies for pseudomorphic films are calculated as a function of film thickness from 1 to 10 layers, employing first-principles spin-polarized density-functional theory calculations in the generalized gradient approximation. First-principles calculations are also employed to obtain the Fe surface stress used in the Peierls-Nabarro model to account for the strain dependence of the surface energy. It is found that the competition between the misfit strain, misfit dislocations, film surface and interfacial energies gives rise to a driving force for solid-state dewetting of a single-crystal, internal-defect-free film, i.e., an instability of a flat film that leads to formation of thicker and thinner regions. The details of the energetics are presented to demonstrate the robustness of the mechanism. Our findings indicate that misfit dislocations and their configurations play a significant role in a morphological evolution of metallic thin films.     

Interfacial Microstructure between WC-Based Cermet and Cu Alloy

A WC-TiC-Co/CuZnNi composite layer was produced on 1045 steel substrate by means of inside-furnace brazing technique. The microstructure, phase constituent and interfacial diffusion behavior between cermet and CuZnNi alloy were investigated by means of scanning electron microscopy (SEM), transmission electron microscope (TEM), electron probe microanalyzer (EPMA) and X-ray diffraction. The results showed that microstructure of matrix was α and β phases. Cermet particies were surrounded by the α+β phases in the composite layer and their sizes were almost similar to those in original state. The interfacial zone was formed by the mutual diffusion of elements under the condition of high temperature. The interface consists of WC, TiC, CuZn, and CuNi phases, and there are no microcracks and inclusions near the interface.     

A TEM study of the interfaces and matrices of SiC-coated carbon fibre/aluminium composites made by the K2ZrF6 process

Carbon fibre-reinforced aluminium composites were pressurelessly cast by using K₂ZrF₆ as the wetting promotion agent. Transmission electron microscopy (TEM) and energy dispersed analysis of X-rays, (EDAX) were used. The results showed that interfacial reactions were very active after K₂ZrF₆ treatment. This was caused by the diffusion and reaction of zirconium in the surface of carbon fibres or in the SiC coating. Silicon alloying of aluminium could suppress the interfacial reactions by decreasing the activity of zirconium and changing intermetallic Al₃Zr to Zr₃Al₄Si₅, and building up the phase equilibrium between SiC, aluminium and silicon. The requested silicon content was higher than the equilibrium content of Al-Si-SiC system to suppress the SiC/Al interfacial reaction. A perfect interface was achieved in SiC-coated carbon fibre Al-12 wt% Si composite.