金属熔液对氧化镁陶瓷润湿行为研究进展

MgO陶瓷因各种优异性能在轻质高强的金属基复合材料、电子封装材料和涂层材料领域都具有广阔的应用前景,然而研究金属熔液对MgO陶瓷的润湿性是MgO陶瓷能否成功应用于这些领域的基础所在,因此研究金属熔液对MgO的润湿性就显得极为重要.本文通过综述Al/MgO陶瓷反应体系、Mg/MgO陶瓷非反应体系以及其它金属包括稀有金属、贵金属与MgO陶瓷润湿行为的研究进展,将各种金属熔液对于MgO陶瓷的润湿行为分为反应型润湿金属、非反应型润湿金属和非反应型难润湿金属等类型.此外还讨论了目前金属熔液与MgO陶瓷润湿行为研究中尚为存在的一些问题与争论,为金属熔液与MgO陶瓷润湿行为理解的进一步深入提供了支持.     

Synthesis of boride and nitride ceramics in molten aluminium by reactive infiltration

The infiltration of solid powder mixtures with molten aluminium has been investigated as a potential route for the synthesis of ceramic/metal composites. Either titanium or tantalum powder was mixed with boron nitride flakes for the reaction powder mixture. The infiltration occurred spontaneously at 1473K for both [Ti+BN] and [Ta+BN] powder mixtures. Owing to reactions between the starting materials, both boride and nitride ceramics were produced in molten aluminium. TiB2 and AlN were produced from the [Ti+BN] powder mixture, and TaB2 and AlN were produced from the [Ta+BN] powder mixture. When the [Ti+BN] powder mixture was used, a reaction producing Al3Ti took place immediately after the infiltration of the molten aluminium, and a subsequent reaction producing TiB2 and AlN proceeded gradually. The time required to convert BN flakes to TiB2 and AlN particles at 1473K was in the range of 1800–3600 s. On the other hand, when the [Ta+BN] powder mixture was used, there was an initial incubation period to allow the tantalum and molten aluminium to react with each other. The reaction between tantalum, BN and aluminium took place after this incubation period. This revised version was published online in November 2006 with corrections to the Cover Date.     

The wetting of carbon by copper and copper alloys

The effects of alloying additions on the wetting of two types of carbon, HX30 graphite and vitreous carbon, have been investigated, with a view to developing a system for metal impregnation of carbon fibre assemblies. Pure copper is inert and non-wetting but two additions caused the copper to wet: Cr on both substrates and V on the vitreous carbon only. Many of the additions formed a carbide reaction layer at the interface, and in the two wetting systems this was a thin, continuous, coherent layer. The data have been analysed in terms of the chemical and physical properties of the system and it was found that the wetting behaviour of copper alloys on HX30 graphite and vitreous carbon could be explained in terms of the behaviour of the reaction product carbides of the alloying addition when these existed.     

Wetting in infiltration of alumina particle preforms with molten copper

The high-temperature wettability of alumina particulate preforms by copper is investigated by means of infiltration experiments conducted at 1473 K under low oxygen partial pressure. Wetting is quantified in terms of drainage curves, which plot the volume fraction of metal in the porous medium vs. the applied pressure. Mercury porosimetry is also used on similar preforms for comparison. The effect of volume fraction, particle geometry and capillary parameters on the drainage curve are studied and compared with the expression proposed by Brooks and Corey. The influence of the particle volume fraction and capillary parameters characterizing wetting in the two systems is discussed to derive an effective contact angle for wetting of alumina particles by molten copper.     

The wetting of carbon and carbides by copper alloys

In a previous paper (J. Mater. Sci. 5 (1970) 149) a model was developed to predict the wetting behaviour between carbon and copper alloys containing 1 at. % of a carbide forming element. In the present paper it is shown that the model can be applied successfully to alloys containing as little as 0.15 at. % chromium or vanadium and as much as 13 at. % titanium. A further development of the model is its use to predict carbide surface energies, the values derived being in good agreement with literature data.     

Critical wetting angle for spontaneous liquid infiltration into orderly packed fibres or spheres

The static mechanics requirement for liquids to infiltrate spontaneously into orderly packed monosized spheres or fibres is studied. It is found that a wetting angle much lower than 90 ° is required to achieve spontaneous infiltration, and this wetting angle also varies considerably with respect to the infiltration direction, the arrangement of the fibres or spheres, and the packing density.     

Super-lyophobicity of porous Si3N4/BN ceramics with nanopores and nanowires by molten copper

Porous Si₃N₄/BN ceramics (PSBC) with a microstructure containing nanopores and nanowires were prepared by reaction bonding of silicon nitride (RBSN) technique. The phase composition and microstructure of PSBC were characterized by X-ray diffractometry (XRD) and field emission scanning electronic microscope (FE-SEM). The porosity of PSBC was 52.6%, the pore size was in the range of 60 to 300 nm. The wettability of PSBC by molten Cu at 1300 °C was investigated by the sessile drop method. The ceramics exhibit super-lyophobicity by molten Cu. The nanopores and nanowires embodied in PSBC increased the heterogeneity and surface roughness, resulting in the super-lyophobicity of the ceramics by molten Cu.     

The wetting of alumina by copper alloyed with titanium and other elements

The wettability of alumina by ternary alloys of copper, titanium and aluminium, gallium gold, indium, nickel or silver has been investigated using sessile drop tests conducted in vacuum at 1050–1250° C. Substantial additions of titanium are known to induce copper to wet alumina due to the formation of a titanium rich reaction product at the alloy/ ceramic interface, but the present work has shown that the concentration of titanium can be reduced by the addition of ternary alloying elements. Additions of indium are very beneficial, of aluminium, gold or silver are moderately beneficial, and of gallium or nickel are of negligible benefit or detrimental. These observations, and previous work with copper-tin-titanium alloys [1] can be interpreted in terms of effects on the activity of titanium which it is argued will be enhanced if the ternary alloying element has a low surface energy and is readily saturated by titanium. The correlation of the experimental wetting observations with the surface energy and titanium solubility data for the ternary alloying elements provides a basis for the rational development of reactive metal brazes for joining unmetallized ceramics.     

The wetting of copper by Al–Zn–Sn solders

Copper wetting times were measured for various Al–Zn–Sn solders using a wetting balance. Wettability of Cu with the Al–Zn–Sn solders was enhanced by increasing the Al and Zn contents. A scanning electron microscope (SEM) investigation on the solidified wetting sample revealed that diffusion of Al and Zn towards Cu is responsible for the observed wetting behaviour. The dipping speed is also important.     

The role of silicon in wetting and pressureless infiltration of SiCp preforms by aluminum alloys

Silicon plays an important role in the production of Al/SiC metal matrix composites. As an alloying element in aluminum, silicon retards the kinetics of the chemical reactions that result in the formation of the unwanted intermetallics Al₄C₃ and Al₄SiC₄. As a thin coating on silicon carbide, silicon becomes an active participant in a thermally activated chemical reaction that enhances wetting of silicon carbide by aluminum alloys. Consequently, Al/SiC composites made with siliconized silicon carbide and silicon rich aluminum alloys show mechanical properties that are significantly different from those of similar composites produced with unsiliconized silicon carbide or with aluminum alloys that do not contain silicon. It is shown that a silicon coating on SiC significantly enhances wetting of SiC particles by aluminum alloys, reduces porosity, does not affect the modulus of elasticity, but decreases the modulus of rupture of Al/SiC metal matrix composites.     

The effect of interfacial morphology on wetting of graphite by molten silver at high temperature

The wetting of graphite by molten silver was investigated at the temperature range from 1000 to 1350?°C using the sessile drop method coupled with a video-enhanced image digitization technology and a best-fitting algorithm. At the temperature range from 1100 to 1175?°C the contact angle θ was observed suddenly increasing and then decreasing, repeatedly. A similar behavior was not found in the comparison test performed on wetting of refractory (ZrO₂) by molten silver at the same range of temperature. A surface analysis of the graphite used in the measurements was performed, showing a rings-shaped surface morphology. The correlation between the wetting diameters, the ring diameters and the observed drop contractions was then brought out. The measured contact angle decreases while a “trough” forms at the three phases contact line. At the observed θ sudden increase, the drop is actually “jumping out” from the trough, since the rate of the formation of the trough is lower than the rate at which the drop changes its shape. The process then starts again, with the formation of a new trough. The measured θ is obviously affected by the trough geometry.     

The wetting of solids by molten metals and its relation to the preparation of metal-matrix composites composites

This review aims at making a bridge between the fundamentals of the wetting of solids by liquid metals and the practice of the preparation of metal-matrix composites. One recalls first the significance of concepts such as surface tension, work of adhesion, adsorption and the relation between these concepts, the phenomenon of wetting and the process of liquid metal infiltration. Thereafter, the wetting of various types of solids is considered: metals, oxides, carbon and carbides. !n the !light of this body of science, one proposes finally a critical evaluation of the literature concerning the preparation of metal-matrix composites by liquid metal infiltration techniques. Particular emphasis is devoted to reinforcements made of graphite, alumina or silicon carbide multifilament fibres; the use of coatings and the addition of alloying elements to the metal are successively discussed.     

无压浸渗制备含镍陶瓷/铁基合金复合材料微观组织及浸渗机理

通过铁合金无压浸渗含镍氧化铝陶瓷的方法,制备了陶瓷/铁合金复合材料.其工艺过程是:将镍粉与陶瓷粉混合球磨后,压制成具有网络结构的陶瓷体,经烧结成瓷后,铁合金无压浸渗,浸渗温度1600℃,保温4h.研究结果表明,含镍陶瓷与铁合金在界面处形成锯齿状的机械啮合,两相之间无过渡层以及微裂纹存在;铁合金中的Fe、Cr元素呈梯度分...     

The interaction of molten copper with solid iron

The interaction phenomenon of solid iron with molten copper was studied by investigating the interfacial microstructures of Cu/Fe and Cu-Ag/Fe and the migration mechanism of molten copper and Cu-Ag alloy into the solid iron. A small quantity of copper or Cu-Ag alloy was melted in a solid iron cylindrical specimen at temperatures ranging from 1100 to 1400° C using a high-frequency induction furnace. The Cu/Fe interfacial microstructure consisted of iron dendrites in the copper matrix, and an iron dendrite layer and a copper-penetrated solid solution zone adjacent to each other at the interface. Irrigation effects and grain-boundary penetration were observed partially at lower temperature. The addition of silver to molten copper causes inactivation of the reaction, resulting in the formation of thin reaction layers at the interface. The migration of molten copper and Cu-Ag alloy into solid iron occurs mainly with the formation of an iron-saturated layer due to iron dissolution and a copper-penetrated solid solution zone due to incipient volume diffusion. The copper penetration appears to be dominated by volume diffusion at high temperatures and by both volume and grain-boundary diffusion at low temperatures. Increased silver content in the molten copper decreases the penetration rate constant.     

Surface and grain boundary wetting of Fe based solids by molten Pb and Pb-Bi eutectic

Surface and grain boundary wetting and penetration of pure Fe and a martensitic steel by Pb and Pb-Bi eutectic alloys were studied by the sessile drop and dispensed drop techniques at different temperatures (400–900^°C) and times (up to 30 h). By using two different atmospheres—high vacuum and a He-H₂ gas—and different heat treatments, wetting was studied for both oxidized and deoxidized solid substrates.     

熔融硅液相浸渍法制备C/C-SiC复合材料

采用熔融硅液相浸渍法制备了C/C-SiC复合材料,反应生成的SiC主要分布在层间孔和束间孔碳基体表面,少量分布在束内孔.1600℃渗硅2 h,硅化深度约为2～4 μm.由于液态硅与碳之间的润湿性很好,在碳基体表面形成了连续的SiC层,局部有粗大的多面碳化硅颗粒生成;讨论了细晶粒连续SiC层和SiC粗晶粒形成机理.由于SiC的加入,材料的抗氧化性能得到明显改善.     

Wetting of ceramics by molten silicon and silicon alloys: a review

The surface of silicon is very sensitive to interactions with oxygen present as impurity in furnace atmosphere. It is shown that three types of Si surfaces can be obtained depending on the oxygen’s partial pressure in the furnace and on temperature: oxidized, oxide-free but containing adsorbed oxygen and adsorption free. The influence of oxygen on the surface tension of molten Si is also discussed. Wetting by Si and Si alloys is then described and analysed for three types of ceramics: (i) ionocovalent oxides (Al₂O₃, SiO₂, MgO, etc.), with a particular emphasis on the Si/silica couple, (ii) the different types of carbons where wetting is assisted by the reaction between Si and carbon, and (iii) the predominantly covalent ceramics (SiC, Si₃N₄, AlN, BN, etc). The role of wetting in the processing of silicon or silicon-based multimaterials is also illustrated.