Use Of Interlayer Research Articles

Analysis of the Microstructure and Mechanical Performance of Resistance Spot-Welding of Ti6Al4V to DP600 Steel Using Copper/Gold Cold-Sprayed Interlayers.

In this article, an attempt was made to join DP600 steel and Ti6Al4V titanium alloy sheets by resistance spot-welding (RSW) using an interlayer in the form of Cu and Au layers fabricated through the cold-spraying process. The welded joints obtained by RSW without an interlayer were also considered. The influence of Cu and Au as an interlayer on the resulting microstructure as well as mechanical properties (shear force and microhardness) of the joints were determined. A typical type of failure of Ti6Al4V/DP600 joints produced without the use of an interlayer is brittle fracture. The microstructure of the resulting joint consisted mainly of the intermetallic phases FeTi and Fe2Ti. The microstructure of the Ti6Al4V/Au/DP600 joint contained the intermetallic phases Ti3Au, TiAu, and TiAu4. The intermetallic phases TiCu and FeCu were found in the microstructure of the Ti6Al4V/Cu/DP600 joint. The maximum tensile/shear stress was 109.46 MPa, which is more than three times higher than for a welded joint fabricated without the use of Cu or Au interlayers. It has been observed that some alloying elements, such as Fe, can lower the martensitic transformation temperature, and some, such as Au, can increase the martensitic transformation temperature.

A Review on the Recent Trends in Forming Composite Joints Using Spot Welding Variants

Traditional resistance spot welding (RSW) has been unsuccessful in forming quality composite joints between steel– or aluminum–polymer-based composites. This has led to the development of spot welding variants such as friction stir spot welding (FFSW), ultrasonic spot welding (USW), and laser spot welding (LSW). The paper reviewed the differences in the bonding mechanisms, spot weld characteristics, and challenges involved in using these spot welding variants. Variants of RSW use series electrode arrangement, co-axial electrodes, metallic inserts, interlayers, or external energy to produce composite joints. FFSW and USW use nanoparticles, interlayers, or energy directors to create composite spot welds. Mechanical interlocking is the common composite joint mechanism for all variants. Each spot welding variant has different sets of weld parameters and distinct spot weld morphologies. FFSW is the most expensive variant but is commonly used for composite spot weld joints. USW has a shorter welding cycle compared to RSW and FFSW but can only be used for small components. LSW is faster than the other variants, but limited work was found on its use in composite spot weld joining. The use of interlayers in FFSW and USW to form composite joints is a potential research area recommended in this review.

Key Roles of Interfaces in Inverted Metal-Halide Perovskite Solar Cells.

Metal-halide perovskite solar cells (PSCs), an emerging technology for transforming solar energy into a clean source of electricity, have reached efficiency levels comparable to those of commercial silicon cells. Compared with other types of PSCs, inverted perovskite solar cells (IPSCs) have shown promise with regard to commercialization due to their facile fabrication and excellent optoelectronic properties. The interlayer interfaces play an important role in the performance of perovskite cells, not only affecting charge transfer and transport, but also acting as a barrier against oxygen and moisture permeation. Herein, we describe and summarize the last three years of studies that summarize the advantages of interface engineering-based advances for the commercialization of IPSCs. This review includes a brief introduction of the structure and working principle of IPSCs, and analyzes how interfaces affect the performance of IPSC devices from the perspective of photovoltaic performance and device lifetime. In addition, a comprehensive summary of various interface engineering approaches to solving these problems and challenges in IPSCs, including the use of interlayers, interface modification, defect passivation, and others, is summarized. Moreover, based upon current developments and breakthroughs, fundamental and engineering perspectives on future commercialization pathways are provided for the innovation and design of next-generation IPSCs.

Modification of perovskite/HTL interface with cooperative polymers bilayer (PTB7-Th/P3HT) to improve perovskite solar cell efficiency and stability

The use of interlayers is a valuable strategy for improving the performance of perovskite solar cells. Usually, such interlayers are thin films of a single material. We consider it interesting to evaluate interlayers formed by two or more materials, to take advantage of their possible cooperative or complementary effect. In the present work, the influence of monolayers and bilayers of the polymers PTB7-Th and P3HT, placed in perovskite/Spiro-OMeTAD interface, is evaluated on the efficiency and stability of solar cells. Devices with the perovskite film made in air (R Cells), and devices with the perovskite made in 2 atm (PbI2 deposition in N2, and CH3NH3I deposition in air) (S Cells) were studied. It is observed that polymer monolayers and bilayers create more compact surfaces, reduce recombination and leakage currents, and promote hole transfer from perovskite. The incorporation of these intermediate layers significantly increases the efficiency of R cells, but less in S cells. With the PTB7-Th/P3HT bilayer, the highest efficiency is achieved in R cells with an increase of 172%, compared with the efficiency of the control cell. On the other hand, with the P3HT interlayer, the highest efficiency is achieved in S cells and the highest stability in both types of cells (R and S). This study suggests that the use of interlayers formed by bilayers of organic materials is an interesting way to improve the performance of perovskite solar cells.

A Review on the Friction Stir Brazing for Joining Dissimilar Materials

Friction stir brazing (FSB) is a new technology developed for its ability to join similar and dissimilar metals and alloys resulting in a joint with considerable characteristics through the use of interlayer (braze) material under the action of a pinless rotating tool and other FSB parameters. The frictional heat during FSB is responsible for the melting of the braze material between the two workpieces, while the shoulder action must be satisfactory for the extrusion of the excess braze liquid phase depending on the FSB parameters used. The parameters of FSB also have a considerable impact on the microstructure and mechanical characteristics of friction stir brazed (FSBed) joints. Sound interfacial bonding can be observed in the central zone of FSBed joints, where intermetallic compounds (IMCs) can be formed by direct diffusion among the dissimilar workpieces after extrusion of liquid phase rather than by mechanical mixing or solidification of braze material. Increasing the transverse speed at a constant rotational speed has an influence on the peak temperature, but it remarkably reduces the holding time owing to the increased cooling rate. The use of vibration in the FSB increments the fluidity of the molten braze material among the joining workpieces resulting in a more homogeneous distribution of IMCs particles. In this review article, FSB parameters, bonding mechanisms, as well as the microstructure, and mechanical properties of FSBed joints are reviewed.

Microstructure, strength and welding window of aluminum alloy−stainless steel explosive cladding with different interlayers

Aluminum 5052 (Al 5052)−stainless steel 316 (SS 316) plates were explosively cladded with Al 1100, pure copper and SS 304 interlayers. The operational parameters viz., standoff distance, explosive mass ratio (mass ratio of the explosive to the flyer plate) and inclination angle were varied and the results were presented. The advent of interlayer relocates the lower boundary of the welding window, and enhances the welding regime by 40%. A triaxial welding window, considering the influence of the third operational parameter, was developed as well. Use of interlayer transforms the continuous molten layer formed in the traditional Al 5052−SS 316 explosive clad interfaces into a smooth interface devoid or with a slender presence of intermetallic compounds. The microhardness, ram tensile and shear strengths of the interlayered clads are higher than those of the traditional explosive clads, and the maximum values are witnessed for stainless steel interlaced Al 5052−SS 316 explosive clads.

Joining of titanium and stainless steel by using different welding processes: A review

In recent years, there is a huge demand in various industries on use of different material combination with contradictory properties for overall cost reduction and performance enhancement. As a result, use of advanced and hybrid welding techniques, development in conventional welding process etc. goes on hike to meet the expectation of dissimilar metal welding and their large-scale production. Particularly the joining of Titanium (Ti) and stainless-steel (SS) dissimilar metal couple is extensively employed for various industrial applications, i.e., nuclear, aviation, automobile, power generation and transmission, chemical industries etc. The main motivation of this combination offers superior corrosion resistance and high strength. The objective of the present study is to address the recent development on joining of Ti-SS metal couple combination by several welding processes, followed by their mechanical and metallurgical properties. It is also observed that the joining of such combination through the fusion welding process quite challenging to achieve desire properties, as the brittle intermetallics such as FeTi/Fe2Ti may formed during process. To overcome such issues, use of interlayer with low melting point than the base metal may proceed to some remarkable achievement.

Enhanced chemical trapping and catalytic conversion of polysulfides by diatomite/MXene hybrid interlayer for stable Li-S batteries

Lithium-Sulfur (Li-S) batteries with high theoretical energy density are promising energy storage systems in the next decades, while the lithium polysulfides (LiPSs) shuttling caused by the sluggish sulfur redox reaction severely lowers the practical performance. The use of interlayer between the cathode and separator has been widely investigated to physically or chemically block the LiPSs, while the introduction of catalytic materials is a more effective strategy to accelerate the conversion of LiPSs. MXene with rich surface chemistry has shown its potential for facilitating the catalytic conversion, however, the aggregation of MXene sheets usually leads to the loss of the catalytic active sites. Herein, we report a diatomite/MXene (DE/MX) hybrid material as the bifunctional interlayer for improving the adsorption/conversion of LiPSs in Li-S batteries. The diatomite with porous structure and rich silica-hydroxyl functional groups could trap LiPSs effectively, while prevent the aggregation of MXene. The DE/MX based interlayer showed bifunctions of enhancing the chemical adsorption and promoting the conversion of LiPSs. The Li-S batteries with the DE/MX interlayer delivered an improved cycling stability with a low capacity decay of 0.059% per cycle over 1000 cycles at 1.0 C. Moreover, stable 200 cycles can be realized with a high sulfur loading electrode up to 6.0 mg cm−2. This work provides an effective strategy to construct bifunctional interlayers for hindering the shuttling of LiPSs and boosting the practical application of Li-S batteries.

A review on friction stir welding: A sustainable way of manufacturing

Abstract Friction stir welding (FSW) process has gained popularity due to its energy efficiency in joining similar or dissimilar materials as compared to traditional way of joining materials and as it involves no use of shielding gas and little harmful emissions due to which it is regarded as ‘green technology’. It’s a solid-state joining process in which plastic deformation takes place to join the similar or dissimilar materials rather than melting. Due to this its applications can be found in the field of industries ranging from aerospace to ship building and rail to electronics. FSW plays a key role in joining many ‘non-weldable’ aluminium alloys such as from 2xxx series alloys (Al-Cu) and 7xxx series alloys (Al-Zn) which is not possible with conventional process leads to softening of weld plates which leads to decrease in the mechanical properties. Hence, the study of various interlayers such as zinc, copper, brass, nickel, tin etc. has become a hot topic for researchers. The joining of dissimilar material is often difficult due to difference in physical properties and composition and hence use of interlayer in FSW helps in effective joining. Insertion of interlayer between the interface of plates to be joined not only enhances the tensile strength of the weld joint but also restricts the excessive formation of hard and brittle intermetallic compounds (IMCs) and leads to controlled formation of fine and uniformly distribution of IMCs and reduces the residual stresses and further increases the joint efficiency. This work contains the review of some important research papers on FSW of similar alloys (Al-Al), dissimilar alloys (Al-Mg), and effects of interlayer on similar alloys (Al/Cu/Al) and dissimilar alloys (Al/Zn/Mg). This paper also throws light on effects of process parameters such as (tool rotation, tool transverse speed, tool materials) on joining of materials by FSW has been discussed along with the suggestions of the researchers.

Comparative study on welding energy and Interface characteristics of titanium‑aluminum explosive composites with and without interlayer

In order to obtain titanium and aluminum composites with excellent performance and master the energy flow form when interlayer is used in explosive welding technology, energy calculation, SPH numerical simulation and experiment were used to conduct a comparative study of TA2/5083 and TA2/1060/5083 in this paper. Under the experiment conditions, TA2/1060, 1060/5083, TA2/5083 interface welding energy are respectively 547.17 MJ, 1178.86 MJ and 1455.5 MJ.The use of 1060 interlayer improves energy utilization efficiency by 14%. Numerical simulations and experiments showed that there was a continuous melting zone and a non-welded zone at the interface without interlayer. After the interlayer was used, the TA2/1060 interface was flat and the 1060/5083 interface showed a wave. There was no brittle intermetallic compound at the titanium‑aluminum composite interface. The use of interlayer reduces the welding energy of a single interface, and the constructed theoretical equation showed that the interface energy can be accurately designed by adjusting parameters of explosives, flyer plates, interlayers and base plates. The use of pure aluminum interlayer is an effective means to improve titanium‑aluminum explosive welding conditions

Improving Microstructural and Mechanical Properties of AA2024 Base Metal by Adding Reinforced Strip Width of AA7075 via Vertical Compensation Friction Stir Welding Technique

Improving microstructural and mechanical properties of AA2024 base metal reinforced with AA7075 via vertical compensation friction stir welding (VCFSW) have become a very vital research area to reinforce the weak part of nugget zone in welded joints. So this paper presents a novel and simple method to improve microstructural and mechanical properties especially ductility and fracture locations of welded aluminum joints by VCFSW technique. Anyhow, most of the welded parts are subjected to the forming processes so improvement in the property of ductility and fracture behavior of welded joints is required. One solution to increase ductility and improve fracture behavior of welded joints is the use of interlayer compensation strip width as a reinforcement which has superior mechanical properties between two blanks of base metal during friction stir welding process. The effect of changing interlayer compensation width was investigated on the microstructural characterization (by an optical microscope, scanning electron microscope and transmission electron microscope) and mechanical properties (using microhardness, tensile and bending tests). Microstructure observations revealed that the tailor-welded joint without compensation interlayer contains micro-voids in the stir zone, while in tailor-welded joints with compensation interlayer, the voids completely disappear on the microscale. X-ray diffraction detected that the use of compensation interlayer of AA7075 between two AA2024 blanks led to the appearance of two precipitates of intermetallic phases, Al2Cu and Mg2Zn, on grain boundaries of aluminum which improved ductility and fracture behavior of welded joints. Ductility enhanced till 54.4% at compensation interlayer width 2 mm when compared to the joint without compensation interlayer. Lower hardness values were detected at nugget zone in joint without compensation interlayer. By contrast, highest hardness values in the softened regions were obtained in compensation interlayer joints. Finally, the highest bending angle occurred without any cracks in case of compensation interlayer of 2 mm at ultimate bending load.

Enhancement ductility of friction stir welded aluminum blanks AA2024 via adding interlayer strip width of AA7075

This paper presents a novel and simple method to improve and enhance the ductility of welded aluminum blanks by friction stir welding technique. Anyhow; most of welded parts are subjected to the forming processes; so the ductility of friction stir tailor-welded aluminum blanks is an important key property. One solution to increase ductility is the use of interlayer compensation strip width as a reinforcement which has superior mechanical properties between two blanks of base metal during friction stir welding process. The effect of changing interlayer compensation width was investigated on the microstructural characterization (by an optical microscope, scanning electron microscope and transmission electron microscope) and mechanical properties (using microhardness, tensile and bending tests). Microstructure observations revealed that the tailor-welded joint without compensation interlayer contains micro-voids in the stir zone; while in tailor-welded joints with compensation interlayer the voids completely disappear on the microscale. x-ray diffraction detected that the use of compensation interlayer of AA7075 between two AA2024 blanks led to the appearance of two precipitates of intermetallic phases, Al2Cu and Mg2Zn, on the grain boundaries of aluminum which improved ductility of welded joints. Ductility enhanced till 54.4 % at compensation interlayer width 2 mm when compared to the joint without compensation interlayer. Lower hardness values were detected at the nugget zone in joint without compensation interlayer. On the other side; highest hardness values in the softened regions were obtained in compensation interlayer joints. Finally; the highest bending angle occurred without any cracks in case of compensation interlayer of 2 mm at ultimate bending load.

Dissimilar metal welding of P91 steel-AISI 316L SS with Incoloy 800 and Inconel 600 interlayers by using activated TIG welding process and its effect on the microstructure and mechanical properties

This study investigates dissimilar metal weldments between P91 steel and AISI 316 L austenitic stainless steel fabricated by activated TIG welding (A-TIG) with and without the use of interlayers of Incoloy 800 and Inconel 600. Through thickness penetration in 8 mm thick plates was achieved in a single pass A-TIG welding using a pre-coated mixture of metallic oxides. Hot cracking was eliminated in A-TIG weld joints in contrast to conventional TIG weld joints without flux. Fully martensitic structure was observed in the weld metal developed without the use of interlayer. Microstructural modifications were achieved with the use of interlayers. The weldment with Incoloy 800 interlayer exhibited martensitic-austenitic structure whereas fully austenitic structure was observed with Inconel 600 interlayer. Interlayers improved impact toughness and ductility of the weld joints without significant loss of tensile strength. The effect of interlayers on carbon migration after aging treatment (620 °C/500 h) was evaluated with the help of thermodynamic simulations and it was observed that the use of interlayers reduced the severity of carbon migration.

Functional interlayer of In2O3 for transparent SnO2/SnS2 heterojunction photodetector

Light signals are widely employed in communications, military, health and space exploration applications, driving demand for self-powered photodetectors and sensors. Generally, the built-in potential in the heterojunction interface facilitates self-powered operation. However, this interface often contains defect states due to lattice mismatch and large differences in work function, which increases the dark current even under zero bias condition. In this article, we report the design of a self-powered and transparent (˜47%) photodetector using a SnO2/SnS2 heterojunction. In addition, we successfully demonstrate a reduction in dark current (6.9–2.8 μA) with a simultaneous increase in photocurrent (11.6–14.7 μA) by introducing an In2O3 interlayer in the SnO2/SnS2 heterojunction, while maintaining the average transparency of ˜47%. In addition, the fabricated device exhibited high rise and fall times of 59 and 79 μs, respectively. An energy band diagram based on the material work functions illustrates the creation of two staggered gap (Type-II) heterojunctions due to the embedded In2O3 nanolayer. This feasible band alignment facilitates the smooth transport of the photogenerated charge carriers. The interlayer also aids lattice matching while reducing defect states in the interface. The interface engineering by using a nanoscale layer embedment would effectively facilitate the feature of photoelectric device without degrading device transparency. This clearly demonstrates that the functional use of interlayer strongly enhances the device performances to suggest the further possible improvement in the transparent optoelectronics.

Regression Modelling of Joining Aluminium Studs to Steel with AA 1100 Interlayer

Recently, there is a steep increase in the requirement for aluminium-steel joints in several automotive and structural applications. But joining of dissimilar metals possesses unique challenges. To overcome these issues, AA 1100 interlayer has been proposed in the friction stud welding of AISI 1030/AA 1050 joints. In the present work, it is found that the use of interlayer not only enhances the joint strength but also inhibits the formation of flash and thereby reduces the consumption of base metals. Applying full factorial design, experiments were conducted to study the influence of interlayer thickness along with other parameters such as rotational speed, friction time and friction pressure on the strength of joint. SEM evaluation on the fractured surface of the specimens was carried out. Ductile mode fracture with dimples observed with 0.95 mm interlayer. Microvoids absorb a lot of energy, and the toughness is high. Hence, the dissimilar joint made using 0.95 mm interlayer have high joint strength. Microhardness measurement across the interfacial region shows increased value near the weld line due to increased plastic deformation. Finally, regression analysis is carried out and an empirical relation has been developed to predict impact strength and axial shortening length in terms of other parameters.

Improvements in Welding Properties of Titanium Through the Use of Interlayers

This article presents some recent results from fusion welding of titanium alloys with interlayers. Without an interlayer, the CP Ti weld typically results in comparable hardness across the weld and base material (BM). However, for α alloys, near-α alloys and α + β alloys, the fusion zone (FZ) and heat-affected zone (HAZ) show high hardness compared with the BM. Inversely, β alloys have FZ and HAZ with lower hardness compared with BM. Under loading, the presence of areas with high or lower hardness could affect the load distribution across the weldments. Post-welding heat treatment (PWHT) is sometimes employed to minimise or avoid this situation. However, for large-size components, PWHT is not practical. In this investigation, we show that by selecting a proper interlayer the above issues can be minimised; hence, PWHT may not be necessary, leading to cost reduction and process efficiency.

Building and Testing 70-100Ah Large Format Prismatic Cu-Intercalated Bi-δ-MnO2/Zn CELLS for GRID Storage Application

Alkaline manganese dioxide (MnO2)/Zinc (Zn) cells have been primarily used as AA batteries, where their complete capacity is discharged only once because the electrochemical irreversibility of its active materials. The energy density obtained from its single discharge is >400Wh/L because of the high capacity of MnO2 (617mAh/g) and Zn (820mAh/g) based on two electron reactions.1 This energy density is higher than other aqueous chemistries like lead acid, nickel-zinc, nickel-metal hydride and some varieties of lithium-ion as well, which could find its usage in important applications like grid-scale energy storage because of its other advantages like low cost, non-toxic material and nonflammable electrolyte; however, it has been relegated to the realm of primary applications like remote controls, etc. because of its electrochemical irreversibility. Recently, we discovered the complete reversibility of MnO2 in alkaline electrolyte by using its layered polymorph called birnessite (δ-MnO2) mixed with bismuth oxide and intercalating it with copper (Cu) ions [Cu-intercalated Bi-δ-MnO2). This new material helped to achieve the theoretical two electron capacity of 617mAh/g for over 3000-6000 cycles.1 When the Cu-intercalated Bi-δ-MnO2 was tested against a Zn anode (15% utilization), energy densities of >160Wh/L were obtained; however, cycle life was limited because of Zn-ion (zincate) poisoning of the cathode to form ZnMn2O4.4 We implemented calcium hydroxide [Ca(OH)2] interlayers in the cells which allowed to capture these zincate ions and prevent the poisoning of the cathode, which resulted in the highest cycle life of 900 yet achieved from this chemistry in literature. These results, however, were laboratory size cells with electrode sizes ranging from 1in2 to 6in2 and occasionally with 2 cathodes and 3 anode pairings. To understand the applicability of this chemistry to real world conditions, it is necessary to test them at much higher capacities (areal and volumetric), larger electrode sizes, in starved electrolyte conditions and much higher active mass loadings, where these batteries can be considered economical. In this talk, we will present our experiences building and testing >70-100Ah large prismatic cells (18in2) of Cu-intercalated Bi-δ-MnO2/Zn. The cells consisted of 10 cathodes and 11 anodes, where the cell capacity varied from >70-100Ah, the Zn utilization varied between 10-25% utilization and a number of different C-rates were tested. We found that the cycle life of the cells were usually affected by the high utilizations of the Zn anode, where causes of failure were due to shape change, drying of the electrode and passivation (probably Type 2-type ZnO formation). The drying of the electrode was a result of the expansion of the cathodes during cycling, which would result in limiting the electrolyte contact with the Zn anodes. Further drying of the anodes were also postulated to be due to pore plugging as a result of ZnO formation. The compactness and expansion of the cells could sometimes also result in minimizing the electrolyte contact or hydroxyl ion transport to the cathodes, which would result in affecting the cathode performance. When cellophane and Celgard 5550 were used as the only separators the cells occasionally experienced “soft” shorts, where Zn and Cu deposited on the separators. The changing pH of the electrolyte, the cross talk between dissolved Mn and Zn ions and minimized hydroxyl ion transport would often lead to formation of spinel-type structures, which would affect the potential curves of the cells. Cycling protocols were also found to be very important in improving the cycle life of the large prismatic cells, where inputting charge on constant voltage protocol was a driver in negatively affecting the discharge curves of the cell. We developed a number of successful methods to improve the cycle life, where use of interlayers like Ca(OH)2 and other types of layers prevented the “soft” short and minimized the effect of zincate ions on the cathode. New electrode designs were incorporated that improved electrolyte contact and maintained hydroxyl transport to the cathodes. Cycling protocols were designed to improve the plating efficiency of the Zn, the efficiency of the cathode formation and improve the cycle life of the cells. New novel membranes were designed that successfully blocked zincate ions from poisoning the cathode. We will present these results in detail and discuss our perspective and new directions for this chemistry. Funding: This work was supported by the New York State Research and Development Authority (NYSERDA) under Project Number 58068.

High-Efficiency Polymer:Nonfullerene Solar Cells with Quaterthiophene-Containing Polyimide Interlayers.

Interfacial layers (interlayers) are one of the emerging approaches in organic solar cells with bulk heterojunction (BHJ) layers because the solar cell efficiency can be additionally improved by their presence. However, less attention is paid to the use of interlayers for polymer:nonfullerene solar cells, which have strong advantages over polymer:fullerene solar cells. In addition, most polymers used for the interlayers possess a low glass transition temperature (T g). Here, it is demonstrated that two types of quarterthiophene‐containing polyimides (PIs) with high T g (>198 °C), which are synthesized using pyromellitic dianhydride (PMDA) and cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CTCDA), can act as an interfacial layer in the polymer:nonfullerene solar cells with the BHJ layers of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and 3,9‐bis(2‐methylene(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene) (ITIC), or (3‐(1,1‐dicyanomethylene)‐1‐methyl‐indanone)‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]‐dithiophene) (IT‐M). Interestingly, the efficiency and stability of devices are improved by the PMDA‐based PI interlayers with a stretched chain structure but degraded by the CTCDA‐based PI interlayers with a bended chain structure.

SnO2/Reduced Graphene Oxide Interlayer Mitigating the Shuttle Effect of Li-S Batteries.

The short cycle life of lithium-sulfur batteries (LSBs) plagues its practical application. In this study, a uniform SnO2/reduced graphene oxide (denoted as SnO2/rGO) composite is successfully designed onto the commercial polypropylene separator for use of interlayer of LSBs to decrease the charge-transfer resistance and trap the soluble lithium polysulfides (LPSs). As a result, the assembled devices using the separator modified with the functional interlayer (SnO2/rGO) exhibit improved cycle performance; for instance, over 200 cycles at 1C, the discharge capacity of the cells reaches 734 mAh g-1. The cells also display high rate capability, with the average discharge capacity of 541.9 mAh g-1 at 5C. Additionally, the mechanism of anchoring behavior of the SnO2/rGO interlayer was systematically investigated using density functional theory calculations. The results demonstrate that the improved performance is related to the ability of SnO2/rGO to effectively absorb S8 cluster and LPS. The strong Li-O/Sn-S/O-S bonds and tight chemical adsorption between LPS and SnO2 mitigate the shuttle effect of LSBs. This study demonstrates that engineering the functional interlayer of metal oxide and carbon materials in LSBs may be an easy way to improve their rate capacity and cycling life.

Effect of Post Weld Heat Treatment on Al 5052-SS 316 Explosive Cladding with Copper Interlayer

This study focuses on effect of post weld heat treatment (PWHT) on interfacial and mechanical properties of Al 5052-SS 316 explosive clad with copper interlayer at varied loading ratios and inclination angles. The use of interlayer is proposed for the control of additional kinetic energy dissipation and to alleviate the formation of intermetallic compounds at the interface. The Al-Steel clads are subjected to PWHT at varied temperatures (300°C-450°C) for 30 minutes and the results are presented. The microstructural characterization of as-clad and PWHT samples is observed by an optical microscope and Scanning Electron Microscope (SEM). Maximum hardness is obtained at the interface of the as-clad and PWHT samples. Increase in PWHT temperature enhances the tensile strength of the composite, whereas, the tensile strength decreases at 300°C due to the diffusion of Al and Cu elements and the formation of detrimental intermetallic compounds.