Interfacial Reaction Layer Research Articles

Electrode interface optimization advances conversion efficiency and stability of thermoelectric devices

Although the CoSb3-based skutterudite thermoelectric devices have been highly expected for wide uses such as waste heat recovery and space power supply, the limited long-term service stability majorly determined by the degradation of electrode interface obstructs its applications. Here, we built up an effective criterion for screening barrier layer based on the combination of negative interfacial reaction energy and high activation energy barrier of Sb migration through the formed interfacial reaction layer. Accordingly, we predicted niobium as a promising barrier layer. The experimental results show the skutterudite/Nb joint has the slowest interfacial reaction layer growth rate and smallest interfacial electrical resistivity. The fabricated 8-pair skutterudite module using Nb as barrier layer achieves a recorded conversion efficiency of 10.2% at hot-side temperature of 872 K and shows excellent stability during long-time aging. This simple criterion provides an effective guidance on screening barrier layer with bonding-blocking-conducting synergetic functions for thermoelectric device integration.

Interfacial behaviors of p-type CeyFexCo4–xSb12/Nb thermoelectric joints

Interfacial diffusions and/or chemical reactions are one of the key issues for the reliability of CoSb3-based skutterudite thermoelectric (TE) joint, especially for the [Formula: see text]-type joint, which limits the applications of TE devices. We investigate the interfacial evolution for [Formula: see text]-type CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints ([Formula: see text]–1, [Formula: see text], 3, 4) and combine the previous study on [Formula: see text]-type Yb[Formula: see text]Co4Sb[Formula: see text]/Nb joint to demonstrate the effect of TE materials on the interfacial microstructure and interfacial resistivity. The reaction–diffusion kinetic analysis shows that the TE materials has little effect on chemical reactions but strongly influence the Sb diffusions. The low energy barrier of Sb diffusion leads to the absent phase decomposition of skutterudites in CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints. The interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints is related with Fe content and the interfacial reaction layer (IRL) growth. In addition, since the interfacial reaction layer growth rate and interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints are both low, Nb is an adequate barrier layer candidate material.

Joining ZnS ceramics by using PbTiO3-doped PbO–B2O3–ZnO

ZnS ceramic has been extensively used in various optical applications, e.g., full-wave band infrared window. The attractiveness of this material is explained by its wider transmission radiation range and higher infrared transmittance. An infrared window has often to be bonded to the protective metal frame due to high risk of involving demanding operational conditions, e.g., a vibration. So, an innovative joining technique must be necessarily uncovered. The objective of this work was designed to use a low-temperature glass powder to directly solder/braze ZnS ceramics during the temperature range between 400 and 450 °C. Our hypothesis was that the mechanical strength between ZnS glass and PbO–B2O3–ZnO powder would be significantly enhanced by doping the solder/braze by PbTiO3 particles. The formed interfacial reaction layer consists of PbS and the uniformly dispersed PbTiO3 particles. A heuristic explanation of the bonding mechanism is offered, and it is found that the use of sintering remelting can reduce defects within the glass joints. Owning to the second-phase diffusion strengthening of PbTiO3 particles and an interfacial chemical bonding in the joint, the mechanical properties are enhanced.

Wetting and spreading behaviors of Al-Si alloy on surface textured stainless steel by ultrafast laser

An ultrafast laser was used to ablate the surface of stainless steel. Periodical surface micro-textures including micro-grooves, micro-pits and micro/nano-ripples were successfully fabricated. As a typical reactive wetting system, Al-Si alloy was used to study the wetting and spreading behaviors on the laser patterned surfaces of stainless steel. The results showed that initial, rapid spreading and gradient balance stages were found in the spreading process. By comparing to the primitive surface, Al-Si alloy exhibited worse wettability on the surface with micro-grooves and micro-pits because of the geometrical characteristics and nano-scale oxides residuals after laser processing; however, Al-Si alloy showed better wettability on the surface with micro/nano-ripples owing to the formation of micro/nano hierarchically patterns and the resultant improved capillary actions. The interfacial reaction layer formed during wetting and spreading processes were also investigated. The surface micro-textures were found to enhance the interfacial metallurgical reactions, thus increasing the thickness of the reaction layer. This work provides a new method to improve the wettability, spreadability and metallurgical reactions of Al-Si/stainless steel reactive wetting system and may extend its use in other reactive wetting systems. This method may be able to improve brazing, soldering, coating and other processes involving solid/liquid interfacial interactions.

Effect of hydrogen on interfacial reaction between Ti-6Al-4V alloy melt and graphite mold

In this paper, the effect of hydrogen on the interfacial reaction between Ti-6Al-4V (Ti64) alloy and graphite casting mold was studied by argon and hydrogen plasma arc melting. The experimental results showed that the thickness and the hardness of the interfacial reaction layer decreased with increasing hydrogen partial pressure. The interaction of activated H atoms in the titanium alloy melt and carbon on the interface, [C] + 4[H] = CH4, could be taking place.

Influence of Holding Time on Interfacial Reaction Layer Characteristics and Wear Properties of CBN/Cu-Sn-Ti Composites

Effects of different holding time on CBN/Cu-Sn-Ti composites have been thoroughly documented. It is revealed that adequate wetting can only take place at 30 minutes and beyond. The thickness of reaction layer is governed by Ti diffusion, and follows a parabolic growth rate until Ti is fully consumed at the compensation of interfacial reactions. Concurrently, more stable Cu3Sn1 has been generated due to the decomposition of unstable Cu41Sn11, which leads to an enhanced wear performance.

Study on the Microstructure and Properties of Al/Cu Laser Filled Solder Joint

Using IPG-YLS-4000 fiber laser to weld T2 copper plate and LY16 aluminum alloy plate, using Zn-10%Al flux cored wire as filler material, the microstructure of the joint was observed and analyzed by SEM and EDS, and the effects of laser power, welding speed and welding line energy on the mechanical properties of the joint were studied. The results show that the joints are mainly divided into copper side brazing area, weld center area and aluminum side fusion welding area. Among them, there are two interface reaction layers composed of intermetallic compound (IMC) in the copper side brazing area, the first layer is CuZn compound in the form of strip, and the second layer is Al2Cu phase in the form of shoot. The central area of the weld is mainly composed of massive α-Al phase and branched β-Zn phase. The tensile strength of the joint increases first and then decreases with the increase of laser power, welding speed and welding line energy. The thickness of IMC layer grows linearly with the increase of line energy. The best process parameters: when the laser power is 2200 W, the welding speed is 0.9 m/min, the welding line energy is 1446.67 J/cm, the IMC layer thickness is 10.11 μm, and the tensile strength reaches the maximum value, 252.6 MPa.

Modelling the Elements Reaction–Diffusion Behavior on Interface of Ti/Al2O3 Composite Prepared by Hot Pressing Sintering

Element reaction–diffusion of Ti/Al2O3 composite which was fabricated at various sintering temperatures, holding times, and a sintering pressure of 30 MPa has been discussed in the present research. Results show that the thickness of the reaction layer of the Ti-Al2O3 interface was increased in exponential form in correspondence with the increase of the sintering temperature. Furthermore, according to analysis, the relationship between the thickness of the interface reaction layer, sintering temperature, and heat preservation time acquiring the kinetic equation of interfacial reaction of Ti/Al2O3 composite was d = 182.5exp(−6.6 × 104/RT)t0.48 by linear fitting.

Effect of Brazing Parameters on the Microstructure and Properties of SiC Ceramic Joint with Zr-Cu Filler Metal

The microstructure and mechanical properties of brazing SiC ceramic with Zr-Cu filler metal under different brazing parameters (brazing temperature, holding time) were investigated. The phase of the joint reaction interface between Zr-Cu filler metal and SiC ceramic was characterized by XRD, the microstructure and fracture morphology of the brazing SiC ceramic joint were analyzed by SEM with EDS, and the strength of the joint was evaluated by compression shear test. The results show that the brazing join between SiC ceramic and Zr-Cu filler metal can be realized at the brazing temperature of 1100 °C~1300 °C, and the main products of interface reaction are ZrC and Zr2Si. The shear strength of the joint increases with the brazing temperature, and reaches the highest at 1200 °C. The thickness of interface reaction layer increases with the increase of holding time at brazing temperature of 1200 °C. Thickness of the interface reaction layer is 2.9 μm when the joint is holding for 20 min, and the maximum shear strength of the corresponding brazed SiC ceramic joint is 57 MPa.

Mechanical properties and microstructure analysis of welding-brazing of Al/ti butt joint with Zn foil additive

TIG welding-brazing features of 5052 Al alloy and Ti6Al4V alloy in butt configuration with Zn foil additive were studied with varying welding heat input. The joint morphology, mechanical performance, microstructure and joining mechanism were investigated in terms of experiment observation and analysis. Results reveal that the TIG welding-brazing process was successfully developed to join 5052 Al alloy and Ti6Al4V alloy. With low heat input, a mass of residual Zn and a thin TiAl3 IMCs layer occurred in the fusion area and brazing area respectively. And with optimal heat input, both the homogeneous diffusion of Zn atoms and the formation of clubbed interfacial reaction layer were beneficial to enhance joint performance. The optimized Al/Ti joint with the maximum joining strength of 192MPa was obtained under the current of 90A. Fracture occurred in the weld seam zone adjacent to the interface of Al/Ti and the fracture morphology was characterized by typical dimples and tearing ridges.

Effect of alumina impurity on microstructure and properties of alumina based conventionally brazed joints

Mo-Mn metallization of alumina ceramics of different purity has been performed at 1400 °C for 10 min in moisthydrogen and nitrogen atmosphere. Nickel coating has been applied onto the metallized alumina ceramics at 1000 °C for 1 hin a reducing hydrogen atmosphere. Finally, metallized and nickel coated alumina ceramics has been brazed with anothermetallized and nickel coated alumina ceramics using CuAg filler alloy at 900 °C for 10 min in a vacuum furnace at 1×10-6Torr pressure. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysishas been carried out for phase analysis, microstructural investigation and elemental composition analysis. The adhesivestrength of the metallizing layer and brazing strength of the joint have been measured by pull down breaking strengthmethod. SEM study has shown that the width of the interfacial reaction region between the metallizing layer and substrateenhances with increasing the impurity content in the alumina ceramics. It has been observed that the adhesive strength of themetallizing layer depends on the interfacial reaction layer thickness. The adhesive strength of the metallizing layer has beenincreased with increasing the thickness of interfacial reaction layer. High adhesive strength of the metallizing layer as wellas brazing strength has beenachieved for alumina ceramics with high impurity content.

Utilization of Chrome Containing Leather Waste in Development of Aluminium Based Green Composite Material

Leather industries are produced lots of hazardous waste in the town areas. Due to which level of soil and air pollutants are increasing day by day. These wastes also harm human health especially children and old age peoples. Among these leather wastes, chrome containing leather waste can be utilized to produce composite materials effectively. In the present work, an attempt is made to excerpt the chromium (Cr) based collagen powder from leather waste and utilize in the synthesis of MMCs. In this work, aluminium is used as base material whereas collagen powder is used as reinforcement along with Al2O3 ceramic particles as a primary reinforcement material. Results reveal the homogeneous distribution of Al2O3 particles and collagen powder in matrix material during the microstructural examination. Proper wettability and good interfacial reaction layer were observed between Collagen powder and Aluminium matrix material. Tensile strength was improved about 14.32% by adding simultaneously 5 wt. % Al2O3 and 1.25 wt. % collagen powder in the aluminium matrix material. However, the hardness was improved about 35.29% by adding 6.25 wt. % Al2O3 in aluminium. It has been also observed that impact strength significantly improved (27.77%) by adding 2.5 wt. % Al2O3 and 3.75 wt. % collagen powder simultaneously in aluminium. Minimum corrosion loss and thermal expansion have been observed for Al/1.25% Al2O3/5% collagen powder composite and Al/0% Al2O3/6.25% collagen powder composite respectively. X-ray diffraction analysis was also performed to validate the presence of Al2O3 and Cr in Al/Al2O3/Collagen powder metal matrix composite material. Mechanical properties were improved significantly by adding Al2O3 and Collagen powder simultaneously in Aluminium. Corrosion behaviour and thermal expansion of composite material were also identified to observe the Al2O3 and Collagen powder addition in Aluminium.

Influence of interfacial structure on the fracture behavior of friction stir spot welded dissimilar joints

Dissimilar joints generally involve the formation of a non-uniform interfacial reaction layer, which affects the joint strength significantly. However, a clear understanding of the effect of interfacial local strength on the macroscopic fracture behavior of the dissimilar joints is lacking in the existing literature. Here, we demonstrate the influence of interfacial reaction layer on the fracture behavior of the friction stir spot welded dissimilar joints between galvanized steel and aluminum alloy through the microscale evaluation of interfacial strength in addition to the conventional macroscale evaluations. Macroscale evaluations showed that the rim region of the joint, which includes a thin reaction layer comprising of both intermetallic compound (IMC) with several hundred nm thickness and Zn-concentrated area partly including voids derived from the discharge of galvanized layer, primarily resists the fracture in tensile shear and cross tension tests. Microscale cantilever beam bending tests showed that the interfacial strength increases with the decrease of reaction layer thickness except in the case of voids. Our study highlights the significance of rim region in spot welding, which has been indicated only by macroscale evaluations.

Preparation and Characterization of Ni/Bi0.5Sb1.5Te3 Heterogeneous Multilayered Thermoelectric Materials

It is difficult to achieve coordinated optimization in thermoelectric materials due to the strong coupling between the electrical and thermal transport properties. However, interface effects, especially those caused by heterogeneous interfaces, are promising to overcome this challenge. In this work, the Ni/Bi0.5Sb1.5Te3 (BST) heterogeneous multilayer structure thermoelectric materials were fabricated by the combination of vacuum evaporation deposition and spark plasma sintering. The influence of Ni layer on the phase composition, microstructure and thermoelectric performance along the different directions (0°, 30°, 60° and 90°, the angles between the performance measurement direction and the Ni layer) of Ni/BST materials were systematically investigated. The microstructural analysis indicates that the distinct heterogeneous interfaces were firmly bonded, and the interface reaction layer was composed of Ni and Te. As compared with the matrix, the electrical conductivity and Seebeck coefficient of the Ni/BST heterogeneous multilayer thermoelectric materials increased, and the thermal conductivity slightly reduced. For Ni/BST90° sample, the maximum ZT value of 1.05 was achieved at 370 K, increased by 19.1% compared with the BST90°. Our work demonstrates that the electron and phonon transport properties can be simultaneously optimized by introducing the ordered heterogeneous interfaces.

Investigation of RSW process on three-layer joining of steel to 6061-T8 aluminum

ABSTRACTIn this article, the RSW process (Resistance Spot Welding) on 6061-T8 aluminum alloy was studied. Spot resistance welding of two-layer plates is difficult and has very low mechanical properties. That is why this process is not practical for industrial applications. In this paper, a spot welding method was used with a novel three-layer technique, which means that an aluminum sheet was located between two sheets of steel and RSW was performed. The effects of RSW parameters including both current and welding time were investigated on the diameter of nugget, the microstructure of heat-affected zone and reaction layer, and mechanical properties. The results show that this method increases the tensile shear load compared with two-layer joining. Also, increasing of welding current, both tensile shear load and weld nugget diameter increased first, and then reduced. The interfacial reaction layer and weld heat-affected zone (HAZ) consisted of , .

Joining of AA 6061/Ti–6Al–4V with zinc interlayer using friction welding process

The formation of intermetallic phases consisting of intermetallic compounds during welding of aluminium/titanium joints is a challenge to the welding processes, in the last two decades. Friction welding is attempted to reduce the formation of intermetallic phases through inserting the interlayer material. In recent years, the number of approaches has been used to insert the interlayer material to avoid metallurgical phases at the weld interface. In this paper, the new technique of electrodeposited zinc coating on titanium substrate acted as an interlayer. Different welding joints were made by varying the interlayer thickness, and henceforth, the characterization is almost done against the mechanical and microstructure of the weld interface. The result shows that the specimen joint having 5 µm Zn interlayer has higher mechanical strength when compared to the specimen joints having 2 µm and 3 µm Zn interlayer. The results of the EDAX line scan concentration profile reveal that across the joint interface there is diffusion of the zinc interlayer into the aluminium zone. The microstructural investigation has been carried out at the joint interface of titanium and aluminium alloy with zinc as an interlayer. It is revealed that the formation of the thin interfacial reaction layer occurs in between the zinc and titanium zone. The intermetallic compounds are formed here in this region, and they are identified as secondary phases of the reaction between zinc and titanium.

Study on Diffusive Reaction Between C-Si System and Mo Metal

Diffusive reaction layer on Mo metal covered by C powder (Si powder or SiC powder, i.e. C-Si system) and heat treated in vacuum ranging from 600°C to 1600°C for 2 h was investigated. Microstructure of interfacial reaction layer between C-Si system/Mo metal were characterized by XRD, SEM, and mechanical properties were compared between reaction layer based on Mo and Mo. The results show: after Si diffusing into Mo, Mo3Si phase appears after heat treatment higher than 1000°C, Mo5Si3 phase forms at 1400°C, even MoSi2 phase appears; after C diffusing into Mo, Mo2C phase appears firstly, then MoC forms at 1400°C; after SiC diffusing into Mo, Mo2C appears first, Mo3Si then forms at 1200°C, Mo5Si3(Mo2C and Mo5Si3C) mutiphase coexist on Mo surface after heat treatment high than 1400°C. Tensile and specific elongation of C-Si system/Mo vary little, but Vickers hardness of Mo diffused by C or Si comparing with Mo enhance distinctly.

Interfacial Reactions and Performance of Li7La3Zr2O12-Stabilized Li-Sulfur Hybrid Cell.

Herein, we report on the characterization of a Li-S hybrid cell containing a garnet solid electrolyte (Li7La3Zr2O12, LLZO) and conventional liquid electrolyte. While the liquid electrolyte provided ionically conductive pathways throughout the porous cathode, the LLZO acted as a physical barrier to protect the Li metal anode and prevent polysulfide shuttling during battery operation. This hybrid cell exhibited an initial capacity of 1000 mAh/g(S) and high Coulombic efficiency (>99%). The interface between the liquid electrolyte and LLZO was studied using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy (XPS). These results indicate that a spontaneous interfacial reaction layer formed between the LLZO and liquid electrolyte. XPS depth profiling experiments indicate that this layer consisted of Li-enriched phases near the surface (e.g., Li2CO3) and intermediate Li-La-Zr oxides in subsurface regions. The reaction layer extended well beyond the LLZO surface, and bulk pristine LLZO was not observed even at the deepest sputtering depths used in this study (∼90 nm). Overall, these results highlight that developing stable electrode/electrolyte interfaces is critical for solid-state batteries and their hybrids.

Growth of NbO2 thin films on GaN(0001) by molecular beam epitaxy

We report on the growth of epitaxial NbO2 thin films by molecular beam epitaxy on GaN (0001). The combination of these two materials is of interest in resistive switching devices that can operate at high temperature. We show that direct deposition of Nb metal on GaN under an oxygen environment results in a substantial interfacial reaction layer. We perform detailed spectroscopic and structural analyses of the film and interface and describe their implications for the growth of this materials system.

Interfacial Reactions and Mechanical Properties Studies of C-Coated and C/B4C Duplex-Coated SiC Fiber-Reinforced Ti2AlNb Composites.

Continuous SiC fiber-reinforced Ti2AlNb matrix composites have a great potential for high-temperature aviation structure applications, and their properties strongly depend on the microstructure of the interfacial reaction layer. Notably, introducing diffusion barrier coatings has still been a popular strategy for optimizing the interfacial structure and interfacial properties of SiCf/Ti. In this work, C coating and C/B4C duplex coating were successfully fabricated onto SiC fibers via chemical vapor deposition (CVD), then consolidated into the SiCf/C/Ti2AlNb and the SiCf/C/B4C/Ti2AlNb composites, respectively, via hot isostatic pressing (HIP) under the condition of 970 °C, 150 MPa, 120 min, and finally furnace cooled to room temperature. The C- and C/B4C-dominated interfacial reactions in the SiCf/C/Ti2AlNb and the SiCf/C/B4C/Ti2AlNb were explored, revealing two different reaction products sequences: The different-sized TiC and the coarse-grained (Ti,Nb)C + AlNb3 for the SiCf/C/Ti2AlNb; and the fine-grained TiB2 + TiC, the needle-shaped (Ti,Nb)B2/NbB + (Ti,Nb)C, the coarse-grained (Ti,Nb)C + AlNb2 for the SiCf/C/B4C/Ti2AlNb. Annealing experiments were further carried out to verify the different reaction kinetics caused by C coating and C/B4C duplex coating. The reaction layer (RL)-dominated interfacial strength and tensile strength estimations showed that higher interface strength and tensile strength occurred in the SiCf/C/Ti2AlNb instead of the SiCf/C/B4C/Ti2AlNb, when the same failure mode of fiber push-out took place.