Compound Layer Research Articles

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu-centre were examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

Effect of strain rate on tensile characteristics and failure behavior of Al/steel welded joint producing by a laser-MIG composite heating source

Studies on dynamic tensile characteristics for Al/steel dissimilar materials are crucial to ensure the integrity and dependability of light-weight structures. In this study, the tensile characteristics and failure behaviors of Al/steel laser-MIG welded-brazed joints were studied. The dynamic fracture mechanisms of the joints are discussed. With the increase in strain rate, the fracture mode and tensile properties of Al/steel joints with reinforcement changed. The joints exhibited two failure modes of heat-affected zone failure at lower strain rates and interface failure at higher strain rates. When the strain rate was 1000 s−1, the increase in dislocation density in the weld reinforcement and diversion of cracks in the intermetallic compound layer significantly enhanced the joint’s properties. The tensile and yield strengths reached 222.6 and 166.6 MPa, 6.5 % and 17.9 % higher than those at a stain rate of 1 s−1, respectively. For Al/steel joints without reinforcement, as the strain rate increased, the crack gradually grew to the Al8Fe2Si phase, leading to a notable enhancement in the joint’s performance. At a strain rate of 500 s−1, the maximum strength of the joint reached 238.3 MPa, representing an increase of 58.9 % in comparison to the strain rate of 1 s−1.

Interstitials in Thermoelectrics.

Defect structure is pivotal in advancing thermoelectric performance with interstitials being widely recognized for their remarkable roles in optimizing both phonon and electron transport properties. Diverse interstitial atoms are identified in previous works according to their distinct roles and can be classified into rattling interstitial, decoupling interstitial, interlayer interstitial, dynamic interstitial, and liquid interstitial. Specifically, rattling interstitial can cause phonon resonance in cage compound to scatter phonon transport; decoupling interstitial can contribute to phonon blocking and electron transport due to their significantly different mean free paths; interlayer interstitial can facilitate out-of-layer electron transport in layered compounds; dynamic interstitial can tune temperature-dependent carrier density and optimize electrical transport properties at wide temperatures; liquid interstitial could improve the carrier mobility at homogeneous dispersion state. All of these interstitials have positive impact on thermoelectric performance by adjusting transport parameters. This perspective therefore intends to provide a thorough overview of advances in interstitial strategy and highlight their significance for optimizing thermoelectric parameters. Finally, the profound potential for extending interstitial strategy to various other thermoelectric systems is discussed and some future directions in thermoelectric material are also outlined.

The use of nonlinear guided-wave features for detection and assessment of intermetallic compounds within dissimilar joints – an experimental investigation

Abstract Welding dissimilar materials is widely employed in industrial construction and manufacturing to enhance cost-effectiveness and performance, often utilizing non-fusion methods like solid-state and high-energy beam welding. However, a significant challenge is the formation of intermetallic compounds (IMCs) at the joint interface, which can weaken the bond and increase brittleness, leading to hidden internal cracks. Nonlinear ultrasound detection methods are employed as advanced, non-destructive testing techniques for early damage inspection in various materials. This research investigates the assessment of the thickness of the intermetallic layer within dissimilar joints using non-linear ultrasound-wave features. Numerical and experimental investigations were performed using four friction stir welding (FSW) lap joints, between AA5052-H32 aluminum and ASTM 516-70 steel, with various intermetallic thicknesses. The methodology involved examining the generation of second-order harmonic frequency by exciting Lamb waves (LW) at specific frequencies. To determine the necessary LWs' excitation frequency, synchronism, and non-zero power flux conditions were employed. The collected signals were measured and analyzed in the time and frequency domains to understand the behavior of the non-linear parameter β′ with the thickness of the intermetallic layer. The results show that β′ changes in a linear manner with the thickness of the intermetallic compound layer (several micrometers in thickness). This provides strong evidence that nonlinear LW features are sensitive to microstructural variations in the FSW joints, which enables them to effectively evaluate their strength.

New insights into the influencing mechanism of ultrasonic vibration on interface of Al/Mg bimetal composites by compound casting using simulation calculation and experimental verification

In this work, the numerical simulation of acoustic pressure distribution in ultrasonic vibration-assisted compound casting of Al/Mg bimetal composites was conducted. Relevant experimental verification was also performed to understand the influence of ultrasonic vibration treatment (UVT) on the interfacial microstructures and mechanical properties of the Al/Mg bimetal composites. Results revealed that the acoustic pressure distributions in the AZ91D melt were related to the vibration frequencies. The effective cavitation area at the Al/Mg interface reached the maximum percentage of 95.6 %, with the ultrasonic frequency of 20 kHz. The experimental results found that the Al/Mg interface without UVT was composed of Al–Mg intermetallic compounds (IMCs, i.e., Al3Mg2 and Al12Mg17) layer and eutectic layer. The oxide film and gas gap were existed between the two layers. The Mg2Si particles were gathered at the IMCs layer. The interfacial grains were coarse and their growth was directional. With UVT, the effective cavitation was occurred at the Al/Mg interface. The oxide film was broken, and the gas gap was eliminated. The interfacial microstructures were significantly refined. Due to the accelerated elemental diffusion and solute transfer by UVT, a more homogeneous Al/Mg interface was obtained. The Mg2Si particles were refined and formed at the eutectic layer. The microhardness mismatch of the IMCs layer and eutectic layer was decreased by UVT. The shear strength of the Al/Mg bimetal composites with UVT was enhanced to 62.2 MPa, which increased by 62.8 %, compared with that without UVT.

SLM and vacuum infiltration hybrid fabricating of stainless steel 316L honeycomb-filled tube/Al matrix composite

A SLMed 316L stainless steel (316L) honeycomb-filled tube was used as reinforcement through vacuum infiltration casting to prepare a new aluminum (Al) matrix composite. Microstructure, hardness, and component result analysis were done on the honeycomb-filled tube/Al matrix composite (HFT/AMC) in the axial end face. The results showed that there is a strong metallurgical bonding layer between honeycomb-filled tube and Al matrix. The intermetallic compound (IMC) layer was about 124.32 μm thick and its hardness was 723.33±84.3 HV. The compressive strength was 406.26 MPa. The X-ray diffraction (XRD) results confirmed that IMCs have formed, and the energy dispersive spectrometer (EDS) results indicated that a lot of elements have moved from 316L to the Al matrix. This increases the hardness of Al matrix by 188.35 % compared to pure Al. In addition, HFT/AMC exhibited good mechanical properties, energy absorption, and excellent tribological properties.

Effect of electromigration on microstructure and properties of CeO2 nanopartical-reinforced Sn58Bi/Cu solder joints

To mitigate the decrease in mechanical performance of Sn58Bi/Cu solder joints resulting from electromigration-induced damage. The CeO2 nanoparticles were incorporated into Sn58Bi solder by a melt-casting method, and their effects on the microstructure and properties of Sn58Bi/Cu solder joints under electromigration were investigated. The study results demonstrate that the addition of 0.125 ~ 0.5 wt% CeO2 nanoparticles refines the eutectic microstructure of Sn58Bi solder alloy. At an addition amount of 0.5 wt%, the composite solder alloy exhibits the maximum tensile strength of 68.9 MPa, which is 37% higher than that of the base solder. CeO2 nanoparticle-reinforced Sn58Bi solder can achieve excellent solderbility with Cu substrates and the joints can significantly inhibit the growth of the anodic Bi-rich layer, which is responsible for electromigration. With the extension of current stressing time, Bi-rich and Sn-rich layer are respectively formed on the anode and cathode in the joints. The intermetallic compound (IMC) layer grows asymmetrically, transitioning from a fan-shaped morphology to a flattened structure at the anode and to a thickened mountain-like morphology at the cathode. Adding the CeO2 nanoparticles helps to mitigate the decrease in mechanical performance caused by electromigration damage during current application to some extent. Over the current stressing period of 288 ~ 480 h, the fracture position shifts from the anodic IMC/Bi-rich interface to the cathodic Sn-rich/IMC interface. The fracture mechanism transitions from a brittle fracture characterized by plate-like cleavage to a ductile–brittle mixed fracture with fine dimples and cleavage.

Microstructure and properties of Zircaloy-4 alloy under low-temperature diffusion bonding with a Ni-plated surface

Zircaloy-4, which is used as a structural material for nuclear cladding, requires precise bonding at low temperature in nuclear power applications. We achieved this using diffusion bonding with Ni plating on the surface of Zircaloy-4. We evaluated the performance of joints at temperatures between 650 and 780 °C. At 650 °C, the joint was successfully bonded. The joint exhibited a maximum shear strength of 207 MPa at 780 °C, which was twice as high as that produced by direct diffusion bonding at 700 °C under the same parameters. The interface was analyzed by using a combination of SEM and TEM to identify the presence of multilayered intermetallic compound layers in the joints. We investigated the mechanism of interface generation and determined the sequence of phase formation by Gibbs free energy calculations to be NiZr, Ni10Zr7, NiZr2, Ni7Zr2, and Ni3Zr. Through X-ray diffraction and cross-section elemental analysis of the fractures, we observed that, at lower temperatures, the joint fracture tended to occur in the Ni layer, whereas at higher temperatures, it occurred between Ni7Zr2 and Ni3Zr. The utilization of diffusion welding with Ni plating applied to the surface of Zircaloy-4 reduces the joining temperature and enhances the properties of the joint.

Formation of a protective oxides-nitrides compound layer with enhanced wear properties, corrosion resistance, and cytocompatibility on novel Ti-Zr-Nb-Ta-Mo multi-principal element alloy

The insufficient surface properties of multi-principal element alloys (MPEAs) hinder their potential biomedical applications. Here, a facile thermal oxidation plus nitridation treatment is conducted to fabricate a protective layer on a novel Ti-Zr-Nb-Ta-Mo MPEA. The total surface layer of NT5-ON consists of a top compound layer, including TiO2, TiN, TiON, ZrO2, and ZrN, and an underneath N-diffusion zone, leading to an exceptionally high wear performance. Also, electrochemical testing and in-vitro evaluations demonstrated enhanced corrosion resistance and cytocompatibility of NT5-ON. As a result, thermal oxidation plus nitridation treatment is an effective technique for designing high-performance hip implant materials.

Nanotubes from Transition Metal Dichalcogenides: Recent Progress in the Synthesis, Characterization and Electrooptical Properties.

Inorganic layered compounds (2D-materials), particularlytransition metal dichalcogenide (TMDC), are the focus of intensive research in recent years. Shortly after the discovery of carbon nanotubes (CNTs) in 1991, it was hypothesized that nanostructures of 2D-materials can also fold and seam forming, thereby nanotubes (NTs). Indeed, nanotubes (and fullerene-like nanoparticles) of WS2 and subsequently from MoS2 were reported shortly after CNT. However, TMDC nanotubes received much less attention than CNT until recently, likely because they cannot be easily produced as single wall nanotubes with well-defined chiral angles. Nonetheless, NTs from inorganic layered compounds have become a fertile field of research in recent years. Much progress has been achieved in the high-temperature synthesis of TMDC nanotubes of different kinds, as well as their characterization and the study of their properties and potential applications. Their multiwall structure is found to be a blessing rather than a curse, leading to intriguing observations. This concise minireview is dedicated to the recent progress in the research of TMDC nanotubes. After reviewing the progress in their synthesis and structural characterization, their contributions to the research fields of energy conversion and storage, polymer nanocomposites, andunique optoelectronic devices are being reviewed. These studies suggest numerous potential applications for TMDC nanotubes in various technologies, which are briefly discussed.

High-Pressure oC16-YBr3 Polymorph Recoverable to Ambient Conditions: From 3D Framework to Layered Material.

Exfoliation of graphite and the discovery of the unique properties of graphene─graphite's single layer─have raised significant attention to layered compounds as potential precursors to 2D materials with applications in optoelectronics, spintronics, sensors, and solar cells. In this work, a new orthorhombic polymorph of yttrium bromide, oC16-YBr3 was synthesized from yttrium and CBr4 in a laser-heated diamond anvil cell at 45 GPa and 3000 K. The structure of oC16-YBr3 was solved and refined using in situ synchrotron single-crystal X-ray diffraction. At high pressure, it can be described as a 3D framework of YBr9 polyhedra, but upon decompression below 15 GPa, the structure motif changes to layered, with layers comprising edge-sharing YBr8 polyhedra weakly bonded by van der Waals interactions. The layered oC16-YBr3 material can be recovered to ambient conditions, and according to Perdew-Burke-Ernzerhof-density functional theory calculations, it exhibits semiconductor properties with a band gap that is highly sensitive to pressure. This polymorph possesses a low exfoliation energy of 0.30 J/m2. Our results expand the list of layered trivalent rare-earth metal halides and provide insights into how high pressure alters their structural motifs and physical properties.

Fabrication of multifunctional cotton fabrics with quaternized N-halamine endowing the synergetic rechargeable antibacterial, wound healing and self-cleaning performances

Cotton has attracted considerable attention due to its functional characteristics. The focus of research on cotton has shifted in recent years towards designing multi-functional and modified media for cotton fibers, which can be firmly combined with textiles, giving them reusability and extending their service life. This study constructed a synergistic antibacterial layer of quaternary ammonium compounds (QACs) and N-halamine (Hals) using an in-situ free radical copolymerization method in water, named QACs/Hals@cotton-Cl. The route significantly increases the number of antibacterial active centers. FTIR, XPS, and SEM were used to systematically analyze the product's chemical structure, surface morphology, and other characteristics. The modified fabric's antibacterial efficiency, wound healing, renewability, and durability were also evaluated. The chlorinated modified cotton fabric could completely eradicate S. aureus and E. coli within 10 min. Compared with pure cotton, it notably promoted the healing rate of infected wounds in mice. The modification method imparted excellent hydrophobicity to the cotton fabric, with a contact angle exceeding 130°, making it easy to remove surface stains. After 30 days of regular storage and 24 h of UV irradiation, the active chlorine concentration (Cl+%) only decreased by 25 % and 39 %, respectively, and the reduced Cl+% was effectively recharged via simple re-chlorination. The hydrophobicity and antimicrobial properties of QACs/Hals@cotton-Cl remained stable even after 20 cycles of friction. This simple synthesis technique provides a convenient approach for the scalable fabrication of multifunctional and rechargeable antibacterial textiles, with potential applications in medical devices and personal hygiene protection.

Acoustic cavitation-induced microstructure evolution in ultrasonically brazed Al/Cu joints using Zn-Al alloy fillers

Tailoring the phase constitutions of the interfacial reaction layers under the assistance of ultrasonic vibration is a convenient method to fabricate high-strength Al/Cu brazing joints. In this study, 1060-Al and T2-Cu dissimilar metals were ultrasonically brazed with Zn-3Al (wt. %) filler metals. Effects of ultrasonic brazing time on the microstructure and mechanical properties of joints were investigated. Results showed that the CuZn5 intermetallic compound (IMC) layer and Cu-based diffusion layer were created on the Cu substrate surface in the joint ultrasonically brazed at 400 ℃ for 2 s. However, the CuZn5 IMC layer was gradually transformed into a thin Al4.2Cu3.2Zn0.7 IMC layer by increasing the ultrasonic vibration time to 15 s. A well-matched coherent interface was formed between the Al4.2Cu3.2Zn0.7 ternary phase and the Cu-based diffusion layer. The phase transition of the Cu-side interfacial layer correlated closely with the acoustic cavitations induced super-saturation regions near the Cu substrate surface. The measured tensile strength of the Al/Zn-3Al/Cu joint ultrasonically brazed for 15 s was 89.3 MPa, which was approximately 2.5 times higher than that brazed for 2 s, and the tensile failure mainly occurred at the interface between the Al4.2Cu3.2Zn0.7 layer and the Cu-based diffusion layer.

Effects of Mo nanoparticles on growth of compounds layer and strength of Sn3.0Ag0.5Cu/Cu solder joint during thermal cycling

Effects of Mo nanoparticles on growth of compounds layer and strength of Sn3.0Ag0.5Cu/Cu solder joint during thermal cycling

Investigating the effect of O2 plasma treatment on the operational characteristics of Schottky-gate AlGaN/GaN HEMT

This study investigates the effect of O2 plasma treatment on the physical and electrical properties of the surface region in Schottky-gate AlGaN/GaN high electron mobility transistor (HEMT). We demonstrate that O2 plasma treatment significantly reduces the gate leakage current and enhances the on/off ratio by three orders of magnitude compared to devices without treatment. The O2 plasma treatment removes organic chemical residue and forms Ga–O bonds on the AlGaN surface beneath the gate metal. X-ray photoelectron spectroscopy results indicate that the treatment effectively forms a Ga–O compound oxide layer, which provides surface passivation. Furthermore, atomic force microscope analysis reveals a 50% reduction in surface roughness after the O2 plasma treatment. Using O2 plasma oxidation treatment caused a shift in the threshold voltage (VTH ) of Schottky-gate AlGaN/GaN HEMT. Initially measured at −5.26 V, the VTH value shifted to +0.5 V. Furthermore, we also employ TCAD simulation to assist in the process developed during the manufacturing process. It is worth noting that the drain current decreases as the Ga–O compound oxide layer increases. This is due to effectively depleted the polarization charges at the AlGaN/GaN interfaces during E-mode operation when reducing the thickness of the AlGaN layer beneath the gate metal. Our results demonstrate the importance of O2 plasma surface treatment in achieving optimal device performance. This study systematically discusses the effect of O2 plasma on AlGaN/GaN surface properties and the formation of Ga–O bonding. It offers insights into developing high-performance Schottky-gate AlGaN/GaN HEMT.

Degradation Processes of Two Compound Layers on Nitrided Surfaces During the Wear Test by “Block on Hot Al Cylinder”

The results obtained in the study help to explain the degradation process of the nitrided steel compound layer. Compound layers with different properties on gas-nitrided H10 tool steel blocks were tested for wear with “block on hot Al cylinder”. Degradation processes were observed on both compound layers with different properties and at three contact pressures. In order to observe the degradation processes in the compound layers, the wear tests were interrupted at various fixed time intervals and the resulting changes were closely monitored. The comprehensive analysis highlighted the complexity of the degradation process in the compound layers and emphasized the existence of complex relationships between the above-mentioned parameters. The reaction of the nitrided steel surface with hot Al is more pronounced in areas with lower contact pressure, while adhesive removal and furrow formation are pronounced in areas with low and medium contact pressure. This process begins with a sufficient density of the areas where islands of adhesive removal are located, their enlargement during the test, the breaking up of the walls between them, and finally the removal of the compound layer in the sliding direction, which appears as furrowing in the final phase of wear.

Optimized Compound Layer Design for Highly Loaded Nitrided Gears

AbstractNitriding is a thermochemical surface hardening process, which can be used to improve the performance properties of gears. In particular, the tooth flank and tooth root load-carrying capacity can be significantly increased by nitriding. Previous work has shown that tribological dominated failure modes and limits, such as the micro-pitting and wear load-carrying capacity of gears, can be significantly increased by a suitable compound layer structure. In this work, the relationship between compound layer design and macro-pitting load-carrying capacity of nitrided gears is explored based on experimental investigations. For this purpose, the materials EN31CrMoV9 and EN42CrMo4 were nitrided under varying nitriding conditions to produce compound layers with different structures and properties. The characteristics of the compound layer such as phase composition, compound layer thickness and pore seam were extensively characterized by means of metallographic techniques, XRD, GDOES, and EBSD. Experimental investigations of the macro-pitting load-carrying capacity were carried out on an FZG back-to-back gear test rig with center distance a = 52 mm. It was shown that the pitting load-carrying capacity depends to a large extent on the characteristics of the compound layer, in particular on the formation of the pore seam. A minimum pore seam thickness of CLTP ≥ 1.8 µm has a positive effect on the pitting load-carrying capacity. The test results for the pitting load-carrying capacity are above (σH lim ≥ 1690 N/mm2) or, in some cases, significantly above (σH lim = 1979 N/mm2) the strength values specified in ISO 6336-5:2016 for nitrided nitriding steels (σH lim = 1450 N/mm2; material quality ME) and case-hardened alloy steels (σH lim = 1650 N/mm2; material quality ME).

Dissimilar linear friction welding of AZ31 magnesium alloy and AA5052-H34 aluminum alloy

The intermetallic compound (IMC) layer, tensile properties, and fracture behavior of dissimilar Mg/Al joints and their relationship during linear friction welding (LFW) are investigated to develop a strategy to obtain high-strength Mg/Al dissimilar materials. The thickness of the Mg/Al-based IMC layer decreases as the applied pressure increases and the frequency decreases. The IMC layer is mainly composed of Mg17Al12 and Mg2Al3 at the weld interface. The tensile strength of the joints fabricated at an appropriate frequency of 50 Hz and a high pressure of 200 MPa during LFW is 235 MPa, which is 94 % the tensile strength of AZ31 and is attributed to the effective suppression of the Mg2Al3 IMC layer growth. At a lower frequency, large defects and pores are formed near the weld interface edge on the Mg side owing to the low welding temperature. The joint fabricated at a higher frequency exhibits a thick and brittle Mg2Al3 IMC layer at the weld interface because of the high growth rate; thus, the dissimilar joints fractured primarily at the Mg2Al3 IMC layer. The inhibition of the Mg2Al3 IMC layer growth yields superior tensile properties in Mg/Al dissimilar materials.

Counter-intuitive mechanical performance variation in aged low-temperature interconnections in electronic packaging

Different from the conventional aging induced continuous mechanical performance deterioration in solder joints, a counter-intuitive “decrease-increase-decrease” variation in shear strength with a peak value 12 MPa higher than the initial state was captured in aged low-temperature BGA structure Cu/Sn–58Bi/Cu solder joints. The first decrease in shear strength was dominated by the coarsening of Sn and Bi phases. The following increase in shear strength was rooted in the concurrent Bi subgrain strengthening, solid solution strengthening of Bi element in Sn-rich phase and precipitation strengthening induced by the Bi-rich phase particles. The eventual decrease in shear strength was ascribed to severely deteriorated interface between the solder matrix and intermetallic compound layer being the weaker site in the long time aged solder joint. This aging induced strengthening phenomenon is inspiring in mechanical performance optimization and reliability elevation of SnBi-based solder joints for the coming chiplet and heterogeneous integration packaging.

Large geometric polarization and magnetic behavior in the multiferroic quasi-2D SrNiF4 fluoride

In the last decades, multifunctional single-crystals that show multiferroic and magnetoelectric responses have attracted considerable attention due to the potential applications and physical phenomena involved in the entanglement of the ferroic orders. This paper explores the structural, ferroelectric, and magnetic properties of the unexplored layered SrNiF4 fluoride compound. We show that, in terms of the vibrational phonon modes, this fluoride compound shows a tangible ferroelectric behavior with an Ps = 14.8 μC cm−2 standing as the largest among its family. Besides, based on our findings such ferroelectric polarization presents a geometric origin that is strongly entangled with the octahedral rotations within the Γ2− phonon mode and enhanced by the structure’s Γ1+ mode. We also observed that the spontaneous polarization is coupled to the noncollinear antiferromagnetic ordering in the structure allowing a switching of the weak antiferromagnetic component when the polarization is reversed.