Papers by Keyword: Interfacial Reaction

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Authors: Xiang Dong Ma, Xin Yang Wang, Ji Wen Li, Shi Zhong Wei
Abstract: Brazing with active filler alloys containing some active elements, which promotes wetting of ceramics surfaces, is one of the most widely methods for joining ceramics to metals. The joints formed by brazing A12O3 to metal by using copper-titanium-nickel (Cu-Ti-Ni) as brazing filler were investigated. The metals/ceramics joints were produced at a vacuum level of 10-2-10-3 Pa at 1273K, using a constant holding time of 10 min. The surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). In the brazing process, copper and titanium in the braze alloy form a series of reaction products. The formation of Ti3Cu3O and Ti2Ni at the interface is characteristic of these joints. The estimated free energies of formation of the Ti3Cu3O and Ti2Ni are -119kcal/mol and -245.92 kJ ~-263.78kJ/mol at 1200~1288K respectively. The highly negative values for the free energies of formation suggest that these compounds are thermodynamically stable.
Authors: Amitava Ghorai, D. Roy
Abstract: In this paper different techniques for sandwich thin film production, characterization and interfacial reactions have been reviewed in order to understand the kinetic behaviour in the above systems. The contact and composite resistance measurements are the indirect methods for this purpose, while X-ray diffraction studies (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Rutherford backscattering (RBS), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), ion sputtering spectrometry (ISS), X-ray photoelectron spectroscopy (XPS) which is also referred to as electron spectroscopy for chemical analysis (ESCA) and atomic force microscopy (AFM) are some of the direct methods. Trends indicate that interfacial reactions start at room temperature.
Authors: Ming Yang, Xin Ma, Ming Yu Li
Abstract: The coarsening behavior of Cu6Sn5 grains formed at the Sn37Pb/Polycrystalline Cu interface is investigated in terms of their orientation evolution during solid-state aging. The results show that the coarsening behavior of the interfacial Cu6Sn5 grains during solid-state aging are quite different from that during liquid-state soldering. The occurrence of the coarsening in the solid-sate reaction is caused by the different surface energies between two adjacent grains. In addition, the texture morphologies of the interfacial grains affect their coarsening rates. In particular, the interfacial Cu6Sn5 grains formed at 200 oC exhibit a texture with the [0001] direction normal to the interface after 16 days of aging at 150 oC, and the formation of this texture accelerates the coarsening process of the interfacial Cu6Sn5 grains.
Authors: Mohammad A. Jafar Mazumder
Abstract: The design of new technologies for treatment of human disorders is a complex and difficult task. The aim of this article is to explore state of art discussion of various techniques and materials involve in cell encapsulations. Encapsulation of cells within semi-permeable polymer shells or beads is a potentially powerful tool, and has long been explored as a promising approach for the treatment of several human diseases such as lysosomal storage disease (LSD), neurological disorders, Parkinsons disease, dwarfism, hemophilia, cancer and diabetes using immune-isolation gene therapy.
Authors: J.E. Indacochea, A. Polar, S.M. McDeavitt
Abstract: This paper describes the metallurgical interfacial reactions at elevated temperatures between reactive zirconium metal and stable oxide ceramics, specifically beryllia, yttria, and magnesia- zirconia composite ceramic. The ceramic/metal systems were preheated at 600°C, and then heated to peak temperatures of 1800°C or above, depending of the system, in ultra pure Argon atmosphere. After a short stay at the peak temperature, each system was cooled to room. The interaction was monitored during heating by a video camera and the interfaces were microscopically examined after the thermal cycle. The microstructure and chemical changes at the interface were evaluated via SEM and EDS. During heating of the beryllia/Zr system, the ceramic was initially reduced and Be alloyed the Zr metal in solid solution, causing Zr to melt locally at the interface at about 1600°C instead of 1855°C. The alloy Zr-Be liquid is what later dissolved the beryllia and infiltrated partially into the ceramic substrate. It seems that there was no solid state reaction between the Zr metal and yttria since Zr melted at its melting temperature of 1855°C; it is evident, however, that the liquid Zr partially dissolved yttria at the interface; yttrium and oxygen segregated to the grain boundaries. The solidified metal tightly bonded to the ceramic substrate as the system cooled to room temperature. In the Zr-MgO/ZrO2 system, Zr melted at 1855°C and it reduced the magnesia, but at the same time the magnesium was volatilized.
Authors: D. Lizarazu, Pierre Steinmetz, J.L. Bernard
Authors: Yawara Hayashi, Ikuo Shohji, Yusuke Nakata, Tomihito Hashimoto
Abstract: To create a high reliability solder joint using IMCs dispersed in the joint, the joints with four types of lead-free solder were investigated. The joint with Sn-3.0Ag-0.7Cu-5.0In (mass%) has high die shear force compared to other joints investigated, and the joint with the Ni-electroplated Cu bonded at 300 oC for 30 min showed the maximum die shear force due to formation of a large number of fine IMCs. In the joint with Sn-0.7Cu-0.05Ni (mass%), uniform dispersion of a large number of IMCs was achieved, although the die shear force of the joint is lower than that of the joint with Sn-3.0Ag-0.7Cu-5.0In. In the joint with Sn-5.0Sb (mass%), a solder area was remained in the center of the joint although a large number of columnar IMCs form at the joint interface. The die shear force of the joint with Sn-5.0Sb increased with increasing the bonding time due to formation and growth of IMCs. In the joint with Sn-3.0Ag-0.5Cu (mass%), IMCs formed at the joint interface and did not disperse in the entire joint.
Authors: Hardinna Wirda Kahar, A.M. Zetty Akhtar, Siti Rabiatull Aisha Idris, Mahadzir Ishak
Abstract: This paper presents a study on relationship of cooling rates towards the intermetallic compound (IMC) morphology. Cooling rate is an important parameter as it has significant effect towards the IMC microstructure formation that indirectly affects solders joint reliability. However, there is still insufficient study regarding the effect of cooling rate on the IMC thickness and microstructure behavior by using Nickel Boron as surface finish material in the electronic packaging industry. In this study, Sn-3Ag-0.5Cu solder was used on Nickel Boron as coating layer. Cooling rates were obtained by cooling specimens in different media which is water and air. The elemental composition was confirmed using Energy-dispersive X-ray spectroscopy and the microstructure of each IMC then analyzed using optical microscope, image analyzer and ImageJ. In this study, faster cooling rate (water) found to provide thicker IMC (6μm) compared to the other medium used. The morphology shape of each IMC also differs between different medium of cooling. IMC that undergoes faster cooling showed continues like layer while the one using air cooling formed scallop like IMC.
Authors: Li Li Wang, Jia Rong Li, Ding Zhong Tang, Guo Hong Gu, Xin Li, Jian Sheng Yao, Hong Na Fan, Shu Xin Niu
Abstract: The characterization of the interfaces between DD6 single crystal superalloy and zirconia-silica (ZrO2-SiO2) ceramic cores was performed by optical microscope (OM), SEM and EDS analysis in order to study the influence of directional solidification condition on the interfacial reaction. The results showed that there were chemical reactions on interfaces between DD6 melt and ZrO2-SiO2 ceramic cores and the main reaction product was Al2O3. The interfacial reaction involved a complex, interdependent system including the oxidation of Al element, the destabilization of calcia stabilization zirconia (CSZ) and the formation of liquid phase with low melting point. The intensity of interfacial reaction increased with the increase of pouring temperature and solidification time, but the number and size of reaction zones could not increase together because of the limited Al content in DD6 alloy.
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