金属/陶瓷润湿性(上)

本文综述了金属／陶瓷的润湿性测定方法，理论研究方法，改善润湿性的技术方法，并系统收集和评价了各种金属／陶瓷体系中润湿性的测试和研究结果。     

金属/陶瓷润湿性(下)

本文综述了金属／陶瓷的润湿性的表征及测定方法，理论研究方法，改善润湿性的技术方法。并系统收集和评价了各种金属／陶瓷体系中润湿性的测试和研究结果。     

添加剂对Ag/陶瓷复合触点材料浸润性及电性能的影响

采用固相反应法制备了LaFe0.25Ni0.75O3陶瓷并加入少量添加物作为改性剂,对其与Ag的浸润性,材料的电阻率以及Ag/陶瓷复合电接触材料的电性能分别进行了研究,结果显示,改性剂使陶瓷材料与Ag之间的浸润性发生明显的变化,且作用效果与改性剂的加入方式有关,添加剂的加入使材料的电阻率增大,同时一定程度上改变了陶瓷在银基体中的分布状态,从而对电接触材料的使用性能产生较大的影响.     

Co—Ti,Ti—Zr—Cu高温钎料在Si3N4陶瓷上润湿性与界面连接

设计了Ｃｏ－Ｔｉ，Ｔｉ－Ｚｒ－Ｃｕ两种高温钎料，进行了它们与Ｓｉ３Ｎ４表面的润湿性实验，利用ＸＲＤ分析钎焊合金与陶瓷界面，结果表明Ｃｏ－Ｔｉ合金中Ｔｉ以化合形态形式存在时，钎料不润湿Ｓｉ３Ｎ４陶瓷，钎焊合金与陶瓷间的办面连接强度与基体材料及界面反应产物密切相关。     

Processing of B4C Particulate-reinforced Magnesium-matrix Composites by Metal-assisted Melt Infiltration Technique

In fabricating magnesium-matrix composites, an easy and cost-effective route is to infiltrate the ceramic preform with molten Mg without any external pressure. However, a rather well wettability of molten Mg with ceramic reinforcement is needed for this process. In order to improve the wettability of the metal melt with ceramic preform during fabricating composites by metal melt infiltration, a simple and viable method has been proposed in this paper where a small amount of metal powder with higher melting point is added to the ceramic preform such that the surface tension of the Mg melt and the liquid-solid interfacial tension could be reduced. By using this method, boron carbide particulate-reinforced magnesium-matrix composites （B4C/Mg） have been successfully fabricated where Ti powder immiscible with magnesium melt was introduced into B4C preform as infiltration inducer. The infiltration ability of molten Mg to the ceramic preform was further studied in association with the processing conditions and the mechanism involved in this process was also analyzed.     

改进浸浆法制备氧化钛/多孔钛复合微滤膜

金属陶瓷复合膜以多孔金属为载体、多孔陶瓷为活性分离层,结合了陶瓷膜和金属膜的优点,具有良好的工业应用前景。采用改进浸浆法制备氧化钛/多孔钛复合微滤膜。将氧化钛粉体分散到氧化钛溶胶中作为制膜液,以提高制膜液在多孔金属支撑体表面的润湿性.结果表明,相同温度下溶胶的表面张力远小于水的表面张力,溶胶分散制膜液的表面张力也远小于水分散制膜液的表面张力.由此明显地改变了制膜液和支撑体的润湿性能,从而可以制备得到连续完整的膜层.由于溶胶粒子对粒径较大的氧化钛颗粒的烧结促进作用,使得膜层可以在较低的温度下烧结.在850℃下烧结的膜层平均孔径为0.31μm,且分布较窄.膜层表面完整无缺陷,与支撑体结合情况良好,膜层厚度约为17μm.膜层N2渗透通量为6.6×105L/(m2.h)(0.1 MPa).     

C.V.D. Coating of Alumina Reinforcing Particles to Improve the Wear Resistance of H.S.S. Based Composites

C.V.D. coating of the reinforcing ceramic particles used in particulate metal matrix composites allows the control of reactivity at the particle/matrix interface. Wear resistant high speed steel-based composites containing uncoated A1₂0₃, uncoated TiC and C.V.D. coated A1₂0₃ were liquid phase sintered, then characterized using “pin-on-disc” wear testing. TiC or TiN C.V.D. coatings of A1₂0₃ were tested to determine die increase in reactivity of the particles with the liquid phases formed during sintering. This resulted in a porosity decrease at the particle/matrix interface in addition to a better ceramic/metal cohesion due to improved wettability. Reactivity and wettability were studied using differential thermal analysis, electron microprobe analysis, transmission electron microscopy, and image analysis. Results from pin-on-disc wear testing illustrated the role of the C.V.D. coating on the wear behavior of the studied materials. Lower wear rates were obtained with the composites containing TiC or TiN-coated Al₂0₃. These results showed that there is a relation between wettability of ceramic particles by the metallic phases and wear resistance of the composites.     

Effects of CO2 laser irradiation on the wettability and human skin fibroblast cell response of magnesia partially stabilised zirconia

Human skin fibroblast cells in vitro responses on the surface of a bioinert zirconia ceramic partially stabilised with magnesia partially stabilised zirconia (MgO-PSZ) bioinert ceramic before and after CO₂ laser treatment were investigated to find the interrelationship between the cell adhesion, wettability and laser parameters. Contact angle, θ, measurements of a set of test liquids were a clear indication that surface treatment of the MgO-PSZ with a CO₂ laser brought about a reduction in θ, indicating that the wettability of the MgO-PSZ had been enhanced. A relationship was found between the wettability and the microstructure of the MgO-PSZ surface and laser processing parameters. It was subsequently deduced that the factors active in causing the observed modification in the wettability of the MgO-PSZ were the increases in the surface O₂ content and the polar component of the surface energy, γ_sv^p, the latter resulting from surface melting and resolidification. Moreover, the investigation into the human skin fibroblast cell response revealed that the CO₂ laser treatment of the MgO-PSZ had resulted in a surface favourable for cell adhesion, as the extent of cell attachment and adhesion on the MgO-PSZ surface was enhanced depending on laser parameters. Such an improvement in cell adhesion, which could be greatly beneficial to developing enhanced bonding at the tissue and implant interface, was influenced by the surface properties of the modified MgO-PSZ, particular wettability.     

Effect of C and Hf Contents on the Interface Reactions and Wettability between a Ni_3Al-Based Superalloy and Ceramic Mould Material

The influence of active elements C and Hf on the interface reactions and wettability between a Ni_3Albased superalloy and the ceramic mould material was studied by using a sessile drop experiment.The microstructure of the alloy interface was investigated by scanning electron microscopy analysis and the phase identification was performed by X-ray diffraction analysis.The results show that interface reactions occur as C and Hf contents reach a critical value.The critical values for C and Hf to cause interface reactions are 0.12 wt%and 1.17 wt%,respectively.The reaction products contain HfO_2 and 9Al_2O_3-Cr_2O_3.Adsorptions of Hf and interface reactions improve the wettability obviously.     

Wetting of carbon nanotubes by aluminum oxide

Most ceramic-carbon nanotube (CNT) composite processing utilizes solid state sintering, hence the concept of wetting of CNTs by molten ceramic is absolutely new. In the present work on a plasma sprayed Al(2)O(3)-CNT nanocomposite, it is observed that molten Al(2)O(3) spreads uniformly on the CNT surface by forming a thin (～20-25?nm) ceramic layer without any cracks. The wettability of the Al(2)O(3)-CNT system is associated with the surface tension and capillary forces as captured from the evolution of microstructure. The dynamic equilibrium between melting and solidification of Al(2)O(3) was deduced from the meniscus height, curvature, contact perimeter and projection area of solidified Al(2)O(3) on the CNT surface. This interfacial phenomenon illuminates the mechanisms of microstructure evolution from Al(2)O(3)-coated CNT bridge structures to CNT mesh formation. Consequent ab?initio modeling depicted distorted iso-surface contours at the interface, suggesting partial bonding and good wettability of Al(2)O(3) on the CNT surface.     

Wetting of Group IV diborides by liquid metals

The possibility to exploit the peculiar characteristics of transition elements diboride ceramics—a class of promising materials for high temperature and highly aggressive applications—often depends to a great extent on the ability to join the ceramic parts one to the other or to special metallic alloys. Therefore, the knowledge of wettability, interfacial tensions and interfacial reactions is mandatory to optimise the joining processes. Data on the wettability and the interfacial features of different metal–ceramic systems, particularly of (Ti,Zr,Hf)B₂ in contact with liquid non-reactive metals Cu, Ag, Au and their alloys, are reported and critically discussed, beginning with the pioneering work made in European eastern countries in the 70s up to the most recent published and new data. Moreover, interfacial energetics at the atomistic level is being increasingly investigated by means of sophisticated modelling techniques such as pseudopotential-based Density Functional Theory (DFT). These approaches will be presented, referred to non-oxide metal–ceramic systems. Given the complexity of ab initio calculations, the study is limited to the ideal work of separation, i.e. with plastic and diffusional degrees of freedom suppressed. Nevertheless, it is shown that the results on the specific transition borides-molten metal systems can be used to interpret the wetting behaviour and the adsorption/reaction interfacial phenomena involved.     

Fe－40Al合金与Al2O3陶瓷的界面润湿现象

本文采用座滴法研究了金属间化合物Fe-40 Al与Al₂O₃陶瓷的润湿性及界面的相互作用,重点考察了温度、保温时间以及合金元素对Fe-40A1合金/Al₂O₃润湿行为和界面反应的影响。     

纳米碳含量对碳/碳化硅陶瓷的机械加工性及与玻璃熔体润湿性的影响

采用无压烧结法制备纳米碳颗粒(nano-Cp)改性碳化硅陶瓷 (C_p/SiC), 研究了不同纳米碳含量对C_p/SiC陶瓷的机械加工性及与玻璃熔体润湿性的影响。通过XRD和SEM对C_p/SiC陶瓷进行物相和显微分析。研究结果表明: 随着可加工相纳米碳含量的增加, C_p/SiC陶瓷的机械加工性能得到明显改善。根据陶瓷材料的机械加工指数(M)综合评价, M₁₅=0.921＞M₂₅=0.547＞M₅=0.056＞M₀=0.021(下标数字代表碳含量), 且15wt%C_p/SiC中的碳颗粒预先被氧化, 抑制了C_p/SiC陶瓷基体表面形成SiO₂, 阻止了C_p/SiC陶瓷与玻璃熔体的润湿, 使夹具材料与玻璃熔体不发生粘接, 适合用作玻璃夹具材料。     

Microstructure of the oxide ceramics/Inconel 713C interface

Nickel-based refractory alloys are used in the aerospace industry as materials for the production of engine turbine blades obtained by the casting method. Both casting process and surface quality of the ceramic mould have a significant influence on product properties. Current research involved the investigation of interactions between oxide ceramics, forming the basic material of casting moulds and crystallisers, and Inconel 713C nickel superalloy. The wettability of ceramics by Inconel 713C was tested for the three types of materials at temperatures commonly used in the directional casting of this alloy. The oxide ceramics/Inconel 713C interfaces were examined by SEM to reveal the microstructure of phase boundary and assess the degree of degradation of the casting mould ceramic coating.     

HK 合金与Al2O3陶瓷界面现象的研究

本文采用座滴法研究了HK 合金与Al₂O₃陶瓷的润湿性及界面间相互作用, 并且采用界面剪切法研究了α-Al₂O₃/HK 合金的界面结合强度, 重点考察了温度与保温时间对α-Al₂O₃/HK合金的润湿行为、界面反应和界面结合强度的影响。      

Role of Mg and Ti on a SiCp,ZrCp/Al composite at elevated temperatures

Metal-matrix composites have been considered as new materials with many attractive properties. One of the characteristics of particulate composites is high strength at elevated temperatures. In this work, a SiC-or ZrC-particle-reinforced composite was fabricated through a casting route and the effect of Ti and Mg alloying on the wettability between ceramic particles and a liquid aluminium alloy was measured with the time required for particulate incorporation. The formation of a reaction product was observed and it was identified by scanning electron microscopy (SEM) and X-ray microanalysis. Observations by SEM revealed that the incorporation time was closely related to the interfacial reactions. The degradation of the composite at an elevated temperature was measured, and the roles of the interfacial reaction and the formation of the reaction product were investigated. Decomposition of the ceramic phase due to the elevated-temperature holding depended on the thermodynamical properties of the ceramic phase. The formation site of the reaction product also affected the degradation of the composite material.     

Wetting and spreading of liquid metals on ZrB2-based ceramics

The possibility to exploit commercially the peculiar characteristics of refractory metallic and ceramic materials and in particular of Zirconium diboride ceramics—a class of promising materials for high temperature applications—often depends to a great extent on the ability to join different ceramics one to the other or to special metallic alloys. As the behaviour of a metal-ceramic joint is ruled by the chemical and the physical properties of the interface, the knowledge of wettability, interfacial tensions and interfacial reactions is mandatory to understand what happens at the liquid metal-ceramic interface during joining processes. In the framework of an extensive study aimed at evaluating the wettability and the interfacial characteristics of different metal-ceramic systems, the behaviour of ZrB₂ in contact with liquid Ag and its alloys (Cu, Ti, Zr, Hf) has been studied. ZrB₂ pure, with different sintering aids or “alloyed” with other ceramic materials (SiC, Si₃N₄), have been used. The wetting and spreading experiments have been performed by the sessile drop technique under controlled atmospheres. The wetting and spreading characteristics and the interfacial reactions are discussed as a function of time, compositions of the ceramic and of the alloy involved. The interfacial morphologies, analysed by SEM and EDS, show the presence of regular interfaces and adsorption layers and of different bulk phases which are interpreted in terms of the relevant phase-diagrams.     

Recent advances in 3D printing of porous ceramics: A review

3D printing, alongside the rapidly advancing field of porous ceramics, is quickly expanding the horizon of what is going to be possible in the future. In this paper, 3D printing technology is evaluated for its compatibility with porous ceramic materials, due to its competitive process in terms of speed and specific tooling, especially for good quality fabrication. The paper reviews the capabilities of these new technology techniques for the fabrication of porous ceramic. The basic technology is the 3D printing techniques, which are used to fabricate porous green ceramic parts that are later sintered. Different ceramic materials are evaluated and the classification of different powders according to their 3D printing quality as well as material aspects is examined. The evaluation of 3D printing process in terms of the powders’ physical properties such as particle size, flowability and wettability is also discussed. The relationship between the different 3D printing parameters and the final printing outcome are assessed.     

陶瓷/金属钎焊体系反应润湿及残余热应力缓解的研究进展

陶瓷/金属钎焊件广泛应用于机械电子、能源化工、航空航天和生物医学等领域以实现材料各自性能上的优势互补。然而,陶瓷与金属原子键合上的差异及热膨胀失配使得它们的高可靠连接面临润湿性和残余热应力的问题。综述了国内外在反应润湿和残余热应力缓解方面的研究进展,对活性钎料/陶瓷界面反应产物及界面结构、界面反应热力学、反应润湿及铺展动力学模型进行了介绍,总结了复合钎料法和添加中间层法等残余热应力的缓解方法,并对当前存在的问题进行了初步探讨。     

C/C复合材料与LAS陶瓷连接的显微结构与性能

采用Y2O3-Al2O3-SiO2-TiO2(YAST)玻璃作为中间层,对SiC-MoSi2表面改性的C/C复合材料与Li2CO3-Al2O3-SiO2(LAS)陶瓷进行热压连接,所施压力为20MPa,保温时间为30min,连接温度分别为1150℃,1200℃,1250℃,1300℃。利用SEM,EDS和BEI(背散射电子像)对SiC-MoSi2涂层,连接界面的形貌和断口进行了分析,研究结果表明,SiC-MoSi2涂层与基体结合紧密,Si、C元素在界面处呈梯度状分布,形成厚度约为15μm的过渡层。YAST玻璃与基体润湿良好,接头的剪切强度可达26.21MPa。