Interfacial Reaction Products Research Articles

Sn–Bi–Fe thermodynamic modeling and Sn–Bi/Fe interfacial reactions

Knowledge of Sn–Bi/Fe interfacial reactions and phase equilibria of Sn–Bi–Fe is of fundamental importance for Sn–Bi-based solder applications. Thermodynamic modeling of the binary Fe–Sn system and the ternary Sn–Bi–Fe system is carried out using the CALPHAD (calculation of phase diagram) method, and the calculated results show good agreement with the experimental information. The Sn–57wt%Bi/Fe interfacial reactions are examined between 250 and 500 °C. A peculiar phenomenon is observed that the reaction rates of Fe with molten Sn–57wt%Bi solder are lower at higher temperatures. This peculiar phenomenon is due to the different intermetallic compounds formed at different temperatures. The transition of the interfacial reaction products with temperatures is caused by the ternary phase equilibria tie-line shift, and can be well illustrated by the calculated Sn–Bi–Fe isothermal sections at different temperatures.

Interfacial reaction between Al72Ni12Co16 decagonal quasicrystalline particles and liquid aluminium

The interfacial reaction between Al72Ni12Co16 quasicrystalline particles and pure Al melt at 670 °C was investigated. For all the studied samples, only one interfacial reaction product was detected at the interface by scanning electron microscopy. The product was identified to be the Al9(Co, Ni)2 crystalline phase, which show an rod-like morphology. The growth rate of the Al9(Co, Ni)2 phase layer is very fast. Based on the microstructure analysis results, it is proposed that the layer growth is initially towards the liquid phase, but changes direction towards the quasicrystalline phase by the solid state reaction of diffusional Al with the quasicrystalline phase at the Al72Ni12Co16/Al9(Co, Ni)2 interface. A grain boundary grooving effect is deduced to have been involved during the reaction process.

Microstructure and thermal properties of recyclable Si p/1199Al composites

Recyclable Si p/1199Al composites with high volume fraction of Si particles were fabricated by squeeze-casting method. The microstructure was observed and the thermal properties were tested and calculated by theoretical models. Si p/1199Al composites are all dense and macroscopically homogeneous without any particle clustering. The interface of Si p/1199Al is clean, smooth and free from any interfacial reaction products. Si p/1199Al composites have high thermal diffusivity (65.083 mm 2/s) and thermal conductivity (168.211 W/(m· °C)). The specific heat capacity of Si p/1199Al composites at constant pressure increases while the thermal diffusivity and thermal conductivity decrease with increasing temperature. Annealing treatment could improve the thermal properties. The results of Maxwell model and P.G. model are higher than those of experiment.

Wetting and laser brazing of Zn-coated steel products by Cu–Si filler metal

Laser brazing is an effective process for joining of steel products widely applied in automobile industry on exposed parts, especially on two following targeted applications: roofs and hatchbacks. The obtaining of good quality joints requires an adequate understanding of interaction phenomena of the brazing filler with the steel surface. This study concerns the investigation of wetting and interfacial reactivity in Cu–Si brazing alloy/Zn-coated steel systems in order to identify how the coating influences the wettability and, consequently, the brazability of steel products. The wetting experiments are performed on hot-dip-galvanized and electro-galvanized coatings, as well as on bare steel. The morphology and chemistry of interfacial reaction products are characterized by SEM-FEG and X-microanalysis.

Modifying the cathodes of intermediate-temperature solid oxide fuel cells with a Ce 0.8Sm 0.2O 2 sol–gel coating

To increase the performance of solid oxide fuel cells operated at intermediate temperatures (<700 °C), we used the electronic conductor La 0.8Sr 0.2MnO 3 (LSM) and the mixed conductor La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) to modify the cathode in the electrode microstructure. For both cathode materials, we employed a Sm 0.2Ce 0.8O 2 (SDC) buffer layer as a diffusion barrier on the yttria-stabilized zirconia (YSZ) electrolyte to prevent the interlayer formation of SrZrO 3 and La 2Zr 2O 7, which have a poor ionic conductivity. These interfacial reaction products were formed only minimally at the electrolyte–cathode interlayer after sintering the SDC layer at high temperature; in addition, the degree of cathode polarization also decreased. Moreover to extend the triple phase boundary and improve cell performance at intermediate temperatures, we used sol–gel methods to coat an SDC layer on the cathode pore walls. The cathode resistance of the LSCF cathode cell featuring SDC modification reached as low as 0.11 Ω cm 2 in air when measured at 700 °C. The maximum power densities of the cells featuring the modified LSCF and LSM cathodes were 369 and 271 mW/cm 2, respectively, when using O 2 as the oxidant and H 2 as the fuel.

Microstructure and interface characterization of a cast Mg 2B 2O 5 whisker reinforced AZ91D magnesium alloy composite

In this study, the microstructure and interface of a Mg 2B 2O 5 whisker-reinforced magnesium composite were characterized using optical microscopy, transmission electron microscopy and X-ray diffraction. It was found that the Mg 2B 2O 5 whiskers have a twinned structure with the (2 0 2) as the twin plane and growth direction along [0 1 0]. The MgB 4O 7 particles and the globular Mg 2Si particles were observed within the Mg 2B 2O 5 whisker, and at the interface between the Mg 2B 2O 5 whiskers and Mg matrix, respectively. The MgO and MgB 2 phase formed at the matrix–whisker interface during vacuum-gas pressure infiltration process due to the interfacial reaction. The crystallographic orientation relationships between the Mg 2B 2O 5 whisker and the interfacial reaction products were found to be [ 0 1 0 ] Mg 2 B 2 O 5 //[1 1 0] MgO and [1 1 0] MgO// [ 2 1 ¯ 1 ¯ 0 ] MgB 2 , and ( 2 0 2 ) Mg 2 B 2 O 5 //(0 0 2) MgO and (0 0 2) MgO// ( 0 0 0 1 ) MgB 2 , respectively. The factors that influence the microstructure of the Mg 2B 2O 5 whiskers and the formation of the interfacial reaction products of Mg 2Si, MgO and MgB 2 phases were discussed.

Studies on Interface of SiCf/Ti55 Composite

Abstract The SiC fiber reinforced Ti55 composite (SiC f /Ti55) was fabricated by Fiber Coating Method (FCM) and Hot Isostatic Pressing (HIP). After the composites were thermally exposed in vacuum under different conditions, the study on the order of interfacial reaction products and the kinetics of interfacial reaction was performed. The results show that only C, Ti and Si elements take part in the interfacial reaction. The order of interfacial reaction products of SiC f /Ti55 composite exposed at 1000 °C can be identified as SiC | Ti 3 SiC 2 | Ti 5 Si 3 +TiC | TiC | Ti55. However, the Ti 3 SiC 2 does not exist in the composites exposed at low temperature. The interfacial reaction layer growth is controlled by diffusion and follows a role of parabolic rate, and the activation energy Q k and the pre-exponential factor k 0 of SiC f /Ti55 composite are 198.16 kJ·mol −1 and 1.79×10 −3 m·s −1/2 , respectively. Compared with the SiC f /Ti composite and SiC f /Ti 2 AlNb composite, there is an interface with higher stability in SiC f /Ti55 composite. However, the interfacial reaction between SiC fiber and matrix takes place easier in SiC f /Ti55 composite than in the SiC f /Ti600 composite and SCS-6 SiC f /super a 2 composite.

Effect of Ti Addition on Shear Strength of Brazing Diamond and Ag Based Filler Alloy

The shear strength samples of brazed single crystal diamond with the (72Ag–28Cu)–xTi (x=2, 4, 7wt.%) active filler metal were prepared, using vacuum brazing methods. Microstructure evolution of interfacial reaction product and shear strength of the brazed diamond and Ag based filler alloy were studied. The results show that there exits a layer of TiC on the surface diamond in different Ti additions, and the thickness of TiC layer increases with the increase of Ti addition. With the increase of Ti addition, the shear strength of the brazed joint decreases due to the increase of TiC layer thickness and amount of intermetallics. From the results, it was seen that mutual diffusion of C and Ti was effective on the morphology of the interface zone that affected the shear strength of the bonds. To achieve a reliable brazed joint, the Ti content must be controlled under 4wt.%.

Fabrication and thermo-physical properties of TiB 2p/Cu composites for electronic packaging applications

TiB 2p/Cu composites with high reinforcement content ( ϕ p=50%, 58% and 65%) for electronic packaging applications were fabricated by squeeze casting technology. The microstructures and thermo-physical properties of the TiB 2p/Cu composites were investigated. The results show that TiB 2 particles are homogeneous and distribute uniformly, and the TiB 2-Cu interfaces are clean and free-from interfacial reaction products and amorphous layers, the densifications of the TiB 2p/Cu composites are higher than 98.2%. The mean linear coefficients of thermal expansion at 20–100 °C for TiB 2p/Cu composites range from 8.3×10 −6 to 10.8×10 −6/K and decrease with increasing volume fraction of TiB 2. The experimental coefficients of thermal expansion agree well with the predicted values based on Turner's model. The thermal conductivities of TiB 2p/Cu composites range from 167.3 to 215.4 W/(m·K), decreasing with increasing volume fraction TiB 2.

Self-lubricating carbon nanotube reinforced nickel matrix composites

Nickel (Ni)—multiwalled carbon nanotube (CNT) composites have been processed in a monolithic form using the laser-engineered net shape (LENS™) processing technique. Auger electron spectroscopy maps determined that the nanotubes were well dispersed and bonded in the nickel matrix and no interfacial chemical reaction products were determined in the as-synthesized composites. Mechanisms of solid lubrication have been investigated by micro-Raman spectroscopy spatial mapping of the worn surfaces to determine the formation of tribochemical products. The Ni-CNT composites exhibit a self-lubricating behavior, forming an in situ, low interfacial shear strength graphitic film during sliding, resulting in a decrease in friction coefficient compared to pure Ni.

The interfacial characteristic of SiCp/AZ91 magnesium matrix composites fabricated by stir casting

The particle/matrix interfaces in SiCp/AZ91 composite fabricated by stir casting were investigated using transmission electron microscope (TEM) equipped with ultra-thin window energy dispersive X-ray analysis (EDAX) system. Chemical reactions indeed occurred at the interfaces. According to EDAX results, the interfacial reaction products are considered to contain Al4C3, MgO, and Mg2Si phases. The interfaces can be classified into three types (interfaces I, II, and III) according to morphological features of the interfaces: (1) for interface I, interfacial reaction products were in direct contact with the surface of SiCp; (2) for interface II, interfacial reaction products were not in direct contact with the surface of SiCp; (3) for interface III, interfacial reaction products were not observed at the interfaces, i.e., interface III was simply formed by the two surfaces of SiCp and matrix. Mg17Al12 and Al8Mn5 precipitate phases heterogeneously nucleated at the particle/matrix interfaces.

Effect of Aspergillus niger Tiegh. L-10 on the physical and chemical properties of a polyaniline coating in the growth substrate

The influence of the growth of Aspergillus niger Tiegh. fungi on the morphological, chemical and electrochemical properties of the polyaniline (PANI) modified Ni surface has been investigated. The strain of Aspergillus niger Tiegh. L-10 was cultivated on the malt extract agar (DIFCO OXOID). A PANI film was synthesized by potentiodynamic polymerization in an aqueous 0.3 M H 2C 2O 4 solution containing 0.1 M aniline on the Ni electrode. The electrochemical behaviour of polymer films was determined in a 0.05 M H 2SO 4 solution by the cyclic voltammetry method. The composition of PANI and Aspergillus niger Tiegh. treated PANI surfaces have been characterized using X-ray photoelectron spectroscopy (XPS). The morphology has been studied using scanning electron microscopy (SEM). The attachment of a polymer film via the metabolic product resulted in oxidation of the surface. It was estimated that at the PANI/microorganism interface, a Ca-complexed carboxylate interfacial reaction product was formed.

Joining Strength and Microstructure of Sintered SiC/SiC Joints Prepared by Active Brazing Process

Sintered SiC ceramics were brazed with itself by ternary Ag-Cu-Ti filler metal foil.Effects of brazing parameters such as temperature,holding time on joining strength,together with interface microstructure and reaction products were investigated.Experimental results indicate that joining strength has peak value with the increasing of brazing temperature and holding time,and the max four-point bending strength of SiC/SiC joints reaches 342MPa.The joining strength increases first with the increasing of brazing temperature and holding time due to thickening of the reaction layer,then decreases due to evaporation of the filler metal.A uniform compact reaction layer of about 1μm thickness is found at the interface between SiC and filler metal,which is formed by the reaction of active element Ti of filler metal and SiC substrate.TiC and Ti5Si3 are confirmed as the reactive products by XRD and EDX.

Kinetic study of interfacial solid state reactions in the Ni/4H–SiC contact

Investigation of the relatively low temperature reaction between Ni nanolayer film and 4H–SiC substrate provides valuable insights into studies of the fundamental properties of SiC Schottky diodes. A quantitative description of chemical kinetics of Ni/SiC contact formation has been studied via deposition of about 50 nm Ni film on 4H–SiC (Si terminated surface) by magnetron sputtering and subsequent annealings at temperatures of 500–700 °C. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) techniques were used to investigate the interface reaction products upon annealing and element distribution across the reaction layer. It is found that the thermodynamically stable silicide Ni 2Si begins to form at the contact interface as a result of sample annealing above 600 °C, which associated with producing carbon distributed at the surface and at the interface of the silicide with the SiC substrate. The kinetic process is described to mainly include the solid state interface reactions and the diffusion of components through the produced layer of silicides. When the diffusion layer is thick enough (more than 100 nm), the kinetic feature is thought to be diffusion controlled, which follows the parabolic law. The active energy of Ni silicide formation was derived as (135.0 ± 19.51) kJ mol −1.

Influence of Mg and Si in the Aluminum on the Thermo-Physical Properties of Pressureless Infiltrated SiCp/Al Composites

SiCp/Al composites based on different matrix elements Mg and Si content were fabricated by pressureless infiltration. Through microscope investigation by SEM and TEM, density examination, coefficient of thermal expansion (CTE) and thermal conductivity measuring by Netzsch DIL 402EP and Netzsch LFA 447 Nanoflash, the effects of Mg and Si in the aluminum on the thermo-physical properties of SiCp/Al composites was studied and analysed. The results showed that , adding Mg element in matrix enhaced the densification and thermal conductivity of composites, but meanwhile increased the CTE of SiCp/Al composites. When Mg element content was in higher than 6.3wt%, CTE of SiCp/Al composites increased obviously. Adding Si element in matrix markedly reduced the CTE of composites , but meanwhile decreased thermal conductivity of composites. When Si element content was higher than 5-9wt%,thermal conductivity of composites declined obviously. Adding Mg element in matrix improved the interface wet ability between molten aluminum and SiC particles, and adding Si element in matrix could control the formation of A14C3 which is a detrimental interface reaction product during the pressureless infiltration processing. Therefore, adding appropriate Mg in company with Si in matrix will be more benefit to enhance the integer properties of SiCp/Al composites.

Interfacial characterisation in Al–20 vol.-%SiCp explosively compacted composite

Al–20 vol.-%SiCp composite was prepared using direct explosive compaction. Interfacial characterisation of the composite was preformed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The results showed that the interface seemed to be clean and no interfacial Al4C3 reaction product was generated along the interface between SiC particles and Al matrix. The results also showed a better bonding between SiC particles and Al matrix in the central region of the compact sample.

Ultra-thin nanocrystalline lanthanum strontium cobalt ferrite (La 0.6Sr 0.4Co 0.8Fe 0.2O 3− δ) films synthesis by RF-sputtering and temperature-dependent conductivity studies

Nanocrystalline lanthanum strontium cobalt ferrite (LSCF) ultra-thin films with high in-plane electrical conductivity have been deposited by RF sputtering from composite targets. The films, with nominal thickness of 54 nm, are crystalline when annealed or deposited at temperatures above 450 °C. Effects of annealing temperature, annealing time, and substrate temperature on crystallization, microstructure, and room temperature lateral electrical conductivity have been systematically studied. No interfacial reaction products between the LSCF and single crystalline yttria-stabilized zirconia (YSZ) were observed from X-ray diffraction studies upon annealing until 750 °C. In-plane electrical conductivity as high as 580 S cm −1 at 650 °C has been observed for LSCF thin films deposited on single crystalline YSZ substrates and sputtered nanocrystalline YSZ thin films; while activation energy for conductivity were determined to be 0.15 eV and 0.10 eV for the former and latter films, respectively, in 650–400 °C range. The high in-plane electrical conductivity for the nanocrystalline LSCF ultra-thin films is likely attributed to their low level of porosity. Micro-solid oxide fuels cells using 15 nm thick LSCF films as cathodes and sub-100 nm yttria-doped zirconia thin film electrolytes have been fabricated successfully and demonstrated to achieve peak power density of 60 mW cm −2 at 500 °C. Our results demonstrate that RF sputtering provides a low-temperature synthesis route for realizing ultra-thin nanocrystalline LSCF films as cathodes for intermediate- or low-temperature solid oxide fuel cells.

Wetting and interfacial phenomena in Ni–HfB 2 systems

The wettability and reactivity between polycrystalline hot-pressed HfB 2 and liquid Ni, Ni–Ti and Ni–B alloys have been investigated by the sessile drop method up to 1520 °C. Independently of the sintering aids (B 4C, HfSi 2), high-temperature interactions led to the formation of a bimodal interface profile, due to the competition between the strong dissolution of HfB 2 in the liquid phase and drop spreading along the substrate surface. Ni demonstrates good wetting with the HfB 2 substrates ( θ = 20°). Compared to Ni, high Ti-containing alloys reveal much faster wettability kinetics with a final contact angle below 10°, accompanied by the formation of an interfacial Ti-rich reaction product. The eutectic NiB alloy shows complete wetting and fast spreading on HfB 2 and minor dissolution of the ceramic into the liquid, a clear indication that higher B contents could optimize the interfacial structure. These results are of practical interest for liquid-assisted composite synthesis and joining of HfB 2-based ceramics.

Effect of Aluminum Concentration on the Interfacial Reactions of Sn-3.0Ag-xAl Solders with Copper and ENIG Metallizations

Aluminum was added into Sn-3.0Ag (wt.%) solder to investigate the effect of aluminum concentration on the interfacial reaction of Sn-3.0Ag-xAl solders with copper or electroless nickel immersion gold (ENIG) metallizations. Four different Sn-3.0Ag-xAl solders (x = 0 wt.%, 0.1 wt.%, 0.5 wt.%, and 1.0 wt.%) were used for comparison. It was found that the composition, morphology, and thickness of interfacial reaction products were strongly dependent on aluminum concentration. At low aluminum concentration (0.1 wt.%), the typical Cu6Sn5 layer was formed at the interface. When the aluminum concentration was 0.5 wt.%, a continuous CuAl2 layer spalled off from the interfacial Cu-Sn intermetallic compound (IMC) layer. Only a planar CuAl2 layer was observed at the interface when the aluminum concentration was increased to 1.0 wt.%. In Sn-Ag-Al/ENIG reactions, Ni3Sn4 was formed and spallation occurred near the interface in the Sn-3.0Ag and Sn-3.0Ag-0.1Al solder joints. When the aluminum concentration was higher than 0.1 wt.%, a thin planar AuAl compound formed at the interface. There was no P-rich phase formation that retarded the spalling phenomenon. The aluminum additive in Sn-Ag solder inhibited the growth of IMCs in the reaction with copper or ENIG metallizations, which was favorable for the reliability of solder joints.

Oxidation Performance of High Temperature Mo-Si-B Alloys and Coatings

Mo-Si-B alloys are attractive due to their high temperature mechanical properties and high melting temperature. The oxidation of multiphase alloys develops in two distinct stages. First, there is a transient stage that corresponds to the evaporation of the volatile MoO3 and to an initial high recession rate. The steady state stage of the oxidation begins when the slower forming borosilicate layer becomes continuous and inhibits further rapid oxidation. Then, the oxidation rate is limited by oxygen diffusion through the borosilicate layer. In order to inhibit the transient stage, a coating strategy has been developed to capitalize on the interdiffusion reactions and to employ a kinetic bias to modify interface reaction products in order to maximize the high temperature stability and performance. In order to achieve a compatible interface coating together with enhanced oxidation resistance, a pack cementation process has been adopted to synthesize metal-rich silicide and borosilicide surface layers. The analysis of the enhanced oxidation performance indicates that a strategy based upon the operating principles of interface reactions in multicomponent systems is effective for developing stable and robust coating systems.