Metal Bond Formation Research Articles

Fluorine-doped Na0.65MnO2 with a layer-tunnel structure for high-rate and long-cycle-life sodium-ion cathodes

Sodium-ion batteries (SIBs) exhibit comprehensive advantages in excellent cycling stability and high-rate performance. In this work, we present a novel cathode with a layered-tunnel coexisted structure with F ions, denoted as Na0.65MnO2-xFx. This material was confirmed the coexistence of layered and rod-like tunnel structures by advanced characterization methods. Due to the high specific capacity of the layered structure and the cycling stability of the rod-like tunnel structure, the Na0.65MnO2-xFx (x=0.2) cathode material exhibits outstanding comprehensive performance. At a rate of 0.1 C, the reversible discharge specific capacity is 124.6 mAh g−1, and notably, after 1000 cycles at a high rate of 10 C, the specific capacity is 55.9 mAh g−1 with a capacity retention rate of 98.2 %. This is significantly higher than the 34.1 mAh g−1 and 48.3 % capacity retention of pristine Na0.65MnO2. The introduction of F leads to an increase in the spacing between the oxide layers, the formation of strong metallic bonds and the formation of composite structures, which not only enhances the stability of the transition metal layer structure but also induces complex changes in the microstructure. This approach of ion doping and microstructure optimization provides a fresh perspective for the design and optimization of high-performance materials for SIBs.

Atomic-level into the microscopic mechanism of gold capture by FeS during gold collection in matte process

Understanding the microscopic mechanisms involved in gold capture by FeS at the atomic level is crucial for optimizing the matte process and improving the gold recovery from gold concentrate containing arsenic and antimony. Herein, the DFT method was employed to explore the adsorption structure and electronic characteristics of a gold (Au) atom on the FeS surface. Furthermore, the effects of Fe/S vacancy and As/Sb dopant on Au adsorption were also investigated. The results reveal that the FeS(100) with S termination exhibits the smallest surface energy (0.56 J/m2) and possesses the highest stability amongst the low-index surfaces. Furthermore, the Au atom exhibits a preference for adsorption on the Fe-bridge site of FeS(100) through chemisorption due to the formation of a strong Au-Fe metallic bond, large adsorption energy (−5.40 eV), and small adsorption distance. Moreover, the presence of S vacancy enhances the Au capture capability of FeS(100) with an adsorption energy of −6.35 eV, while the Fe vacancy slightly weakens it. Additionally, the doping of As and Sb enhances the adsorption of Au atoms on FeS(100), and the Sb doping showcases a more distinct enhancement in Au capture efficiency. The findings of this work contribute to the advancement of matte processing technology, enabling enhanced gold recovery and potentially opening new avenues for the treatment of refractory gold ores.

Stereoselective Synthesis of 2‐Deoxy‐α‐N‐Glycosides from Glycals with 1,4,2‐Dioxazol‐5‐ones

Comprehensive SummaryThe synthesis of N‐glycosides has received significant attention due to their crucial role in carbohydrate chemistry. Despite considerable advancements developed in the construction of N‐glycosides, methods for the stereoselective construction of 2‐deoxy‐α‐N‐glycosides are still limited. Herein, we disclosed a nickel‐catalyzed hydroamination of glycals under mild conditions. This transformation could allow for the stereoselective synthesis of an array of 2‐deoxy‐α‐N‐glycosides with excellent α‐stereoselectivity. Nickel‐catalyzed glycosylation reactions, particularly those involving anomeric C(sp3)‐metal bond formation, have proven to be an effective and stereoselective strategy for producing various N‐glycosides. Additionally, with highlight of the application of this reaction, γ‐sugar amino acid derivatives were synthesized.

Use of the biopore technique to improve soil quality and the growth of beach Casuarina plants on the reclaimed former tin mine land in Bangka Belitung Islands

The tin mining process removes soil layers so that the soil becomes dry and nutrient-poor. Reclamation of tin mining in Selingsing, Gantung Sub-district, Belitung Timur Regency, Bangka Belitung Islands Province has been carried out through revegetation using beach Casuarina plants, but plant growth is slow. On of the efforts that can be made to improve plant growth to restore land and forest conditions is using the biopore technique combined with organic litter and bioactivator solution. This study was therefore aimed to elucidate the effect of the biopore technique on soil quality and the growth of beach Casuarina on the reclaimed former tin mine land. Treatments tested were the use of bamboo biopores and without the use of bamboo biopores, with five replications in each treatment. The effect of variation was measured based on nitrogen, phosphorus, potassium, and lead contents in the root zone and plant growth (plant height and diameter). The results showed that compared to those without biopore treatment, the biopore treatment significantly increased nitrogen, phosphorus, and potassium contents by 0.67%, 2.12%, and 19%, respectively. The organic component of biopore treatment influenced the formation of metal bonds, as indicated by a decrease in lead content by 0.35%. The best plant height of 42 cm was observed in the treatment without biopore, and the best plant diameter of 2.9 cm was in the biopore treatment.

Strengthening of Ta-W alloys by alloying Zr elements: First-principles calculation and experimental perspective

In order to improve the room-temperature strength and hardness of Ta-W alloys, Zr was chosen for alloying and strengthened Ta-W-Zr alloys were developed. The strengthening effect of Zr alloying was investigated based on first-principles calculation and experimental verification. Calculations revealed that the doped of Zr atoms increased the shear modulus G and Young's modulus E of the alloys and promoted the formation of metallic and ionic bonds, which improved the hardness of the alloys. To verify the calculated results, hardness and compression tests were carried out for Ta-W-Zr alloys. The results showed that the compressive strength and hardness of the alloys increased with increasing Zr content, which was consistent with the trend predicted by the calculations. Among them, the maximum compressive strength of Ta-11.3 W-11.2Zr alloy was as high as 1850.53 ± 6.8 MPa and the maximum hardness was up to 478.40 ± 8.3 HV, which was almost twice that of the Ta-10 W alloy. It was indicated that Zr alloying can effectively strengthen Ta-W alloys, which provided a guidance for the development of high-performance Ta-W alloys.

Large-area joining of CF/Epoxy skin and Al alloy web by an advanced continuous resistance spot welding technology to manufacturing wind turbine blade

The large-area resistance welding of resin matrix composites and metal has always been a pursuit for manufacturing of hybrid structure. Herein, an advanced continuous resistance spot welding technology of CF/Epoxy composite and Al alloy based on multipoint sequential welding was developed, which was performed by a stainless-steel mesh implant at 0.4 MPa. A CF/Epoxy-Al alloy joint bonded was composed mainly by implant/resin and Al alloy/resin interfaces, shown a shear strength with about 17.9 MPa. Both types interfaces were analyzed and display similar results: C–O–metal bond formation at the interface is key reaction mechanism.

Investigations into the AuI and PtII Coordination Chemistry of Bidentate “cis‐Spanning” Ligands

AbstractThe novel bidentate PP and PN ligands o‐(Ph2P)−C6H4−C≡C−PPh2 (LPP) and o‐(Ph2P)−C6H4−4−(C5H9N−Me) (LPN), respectively, have been designed as long‐range “cis‐spanning“ ligands for the stabilization of heterodinuclear complexes containing two metal atoms in close proximity. The synthesis of heterodinuclear, formal AuIPtII complexes with the ligand LPP is straightforward. In the course of a one‐pot reaction, a surprisingly high selectivity for the coordination of AuCl and Pt(CNC) (CNC=2,6‐diphenylpyridine‐o,o’‐diate) to the phenyl‐bound and the alkyne‐bound PPh2 sites of LPP is observed, respectively. Chloride abstraction from the resulting heterodinuclear complex [(ClAu)(o‐Ph2P)−C6H4−C≡C−PPh2(Pt{CNC})] with Ag[SbF6] causes metal–metal bond formation and the generation of the cationic complex [LPPAuPt(CNC)][SbF6]. The high site selectivity for the coordination of the two metals to LPP was investigated by stoichiometric reactions of the ligand with one equivalent of the corresponding precursors. While analogous complexation experiments with LPN have not been successful, the synthesis of the heterodinuclear complex [(ClAu)(o‐Ph2P)−C6H4−4‐(C5H9N−Me)(PtCl2{dmso})] and of [LPN(AuCl)2] confirm the ability of LPN to serve as a ditopic ligand. In this context, it is noteworthy that [LPN(AuCl)2] constitutes the first amine–AuCl complex featuring a tertiary amine.

Structure and mechanical properties of novel lightweight refractory high entropy alloys NbMoTiZr-(Al/V): a combined first principles and experimental study

NbMoTaW refractory high entropy alloy (RHEA) has excellent high temperature mechanical properties, but low room temperature ductility and high density severely limit its practical applications. In the present work, to overcome this deficiency, the composition was adjusted, and the mechanical properties of four novel as-cast NbMoTiZr-(Al/V) lightweight refractory high entropy alloys (LRHEAs) were investigated by theoretical calculations combined with experimental methods. The first-principle calculations approach based on density functional theory predicts the mechanical properties of LRHEAs and explains the alloying effects at the atomic and electronic levels. The body-centered-cubic (BCC) phase structure of the alloys were predicted on the formation enthalpy and cohesive energy, as well as empirical parameters such as ΔSmix, ΔHmix, VEC, and the atomic size difference, in conjunction with CALPHAD and XRD. The microstructure of the LRHEAs were also analyzed by SEM. The experimental results, along with the calculated elastic constants and moduli, show significant improvement in the strength and ductility of NbMoTiZr-(Al/V) LRHEAs compared to NbMoTaW RHEA. LRHEAs exhibit elastic anisotropy and are therefore more suitable for use in engineering applications. The strengthening mechanisms of the alloys were analyzed in terms of total and partial densities of states, overlapping Mulliken population, charge density contour and atomic distances. The increased plasticity of LRHEAs is mainly due to the formation of Ti-Ti, Zr-Zr and Zr-Al metallic bonds in the alloys. The calculated results agree with the experimental results, indicating that first-principles calculations are an effective method for predicting the improved properties of lightweight refractory high-entropy alloys. The present work provides a good guideline for the design and research of lightweight refractory high entropy alloys.

Defining the zerogap: cracking along the photolithographically defined Au–Cu–Au lines with sub-nanometer precision

Abstract Cracks are formed along the photolithographically pre-determined lines with extremely high yield and repeatability, when Cu clusters are introduced between planarized Au thin films sequentially deposited on a PET substrate. These clusters act as nanometer-sized spacers preventing the formation of contiguous metallic bond between the adjacent Au layers which will render prepatterned-cracking impossible. While the effective gap width is initially zero in the optical sense from microwaves all the way to the visible, outer-bending the PET substrate allows the gap width tuning into the 100 nm range, with the stability and controllability in the ranges of 100 s and Angstrom-scale, respectively. It is anticipated that our wafer-scale prepatterned crack technology with an unprecedented mixture of macroscopic length and Angstrom-scale controllability will open-up many applications in optoelectronics, quantum photonics and photocatalysis.

Effect of Oxygen Content on Bonding Performance of Sintered Silver Joint on Bare Copper Substrate

Optimizing oxygen level in sintering atmosphere seems to be a more economical method to realize die-attachment on bare copper substrate with silver paste. In this paper, effects of oxygen content on mechanical and thermal performance of sintered Ag joint on bare copper substrate were investigated. The 5×103 ppm was demonstrated as the most appropriate oxygen content for the optimum bare copper joint, which removed most organics in the paste layer while preventing copper substrate from oxidation. Besides, bonding mechanism of joints sintered under different oxygen levels was clarified. For joint sintered at 1×103 ppm, excess residual organics significantly facilitated the formation of hydrogen bonds, resulting in the adhesive-dominated failure mode and worst overall performance. The increase of oxygen content to 5×103 ppm reinforced the bonding strength due to the Ag-Cu metallic bond formation at the interface and ameliorative densification of sintered-Ag layer. As the amount of oxygen further increased, copper substrate was oxidized, and bonding strength experienced a changing course of decline, rise, and flat, which can be attributed to Ag adhesion on copper surface and the formation of voids at the interface between oxide layer and copper substrate.

Модель формування пористості брикетів губчастого титану на стадії спікання

This article examines the peculiarities of the formation of interparticle connections in porous products based on titanium powders using sponge titanium as an example, which are used in the aviation industry and airfield management. The developed model is based on the results of a previous study, where the structure of cuboctahedral and inverse cuboctahedral clusters of packing spherical powder particles was determined at the most dense packing. During the study, a model of the fusion of particles at the points of pressing deformation due to recrystallization under the influence of high temperatures in a vacuum was developed. 4 main stages of powder briquette sintering were considered, and a mathematical model was developed for each of them. Thus, the stage of liquid evaporation is considered from the viewpoint of the cavitation effect of boiling on the surface of particles and boiling of plasticizers. Euler's film boiling formula was used to describe the forces acting on the particle surface; Tolubinsky's formula was used for bubble boiling; convective heat exchange was considered part of the final stage of sintering. The stage of the formation of metallic bonds is modeled on the basis of the results of practical studies in the REV 5.5 furnace, recrystallization based on differential scanning colorimetry on the NETZSCH STA 449F1 Proteus device, and determining the change in grain size according to the E19 ASTM scales using the Jeffers method. The diffusion stage is modeled on the basis of the approximation of the particle deformation model in the contact zones at the pressing stage using the Frenkel formula. Linear shrinkage is modeled based on direct measurement of sample sizes before and after sintering. The developed model has a certain versatility when applied to simulate the interaction of particles of metal powders under the conditions of the formation of porous briquettes, especially if the shape of the particles is close to round or spongy. The obtained result will make it possible to more accurately evaluate such a factor as the adhesion between the particles of the pressing and predict the tensile strength of the material. Additionally, due to the mathematical characterization of the peculiarities of the formation of corpuscular porosity under the conditions of sintering in a vacuum, we can design materials with differentiated porosity, as well as lay the foundations for powder 3D printing of such materials, by assembling grain by grain, or layer by layer with the adjustment of the force of particle compression one into the other.

Enhanced strength without sacrificing ductility in FeCrMnVSix high entropy alloys via controlling the ratio of metallic to covalent bonding

It has been the pursuit of materials science to enhance strength without sacrificing the ductility of a material. By introducing the semi-metallic Si into the FeCrMnV high-entropy alloy (HEA) to control the ratio of metallic and covalent bonding, we obtained a FeCrMnVSix HEAs with high strength and favorable ductility from the perspective of interatomic bonding. First-principles calculation was employed to calculate the structural model, electronic environment, and mechanical properties. The theoretical calculations demonstrated that the covalent bonding had been obtained in the FeCrMnV HEA consisting of metallic bonding due to the addition of Si. Under the guidance of theoretical calculation, FeCrMnVSix HEAs were successfully prepared by laser cladding on 1Cr13 steel substrate. The nanoindentation, Vickers microhardness, and tensile tests were performed, and the results indicated that the strength of HEA was enhanced without sacrificing ductility. In addition, the as-prepared Si-containing HEA coatings exhibited excellent tribological properties. The mechanism of simultaneous formation of metallic and covalent bonds on the mechanical properties was analyzed. The enhanced strength without sacrificing ductility in FeCrMnVSix HEAs is attributed to the proper combination of metallic and covalent bonding, the metallic bonding facilitates favorable ductility while the covalent bonding contributes to excellent strength.

Approach to Chemically Durable Nickel and Cobalt Lanthanum-Nitride-Based Catalysts for Ammonia Synthesis.

Metal nitride complexes have recently been proposed as an efficient noble-metal-free catalyst for ammonia synthesis utilizing a dual active site concept. However, their high sensitivity to air and moisture has restricted potential applications. We report that their chemical sensitivity can be improved by introducing Al into the LaN lattice, thereby forming La-Al metallic bonds (La-Al-N). The catalytic activity and mechanism of the resulting TM/La-Al-N (TM=Ni, Co) are comparable to the previously reported TM/LaN catalyst. Notably, the catalytic activity did not degrade after exposure to air and moisture. Kinetic analysis and isotopic experiment showed that La-Al-N is responsible for N2 absorption and activation despite substantial Al being introduced into its lattice because the local coordination of the lattice N remained largely unchanged. These findings show the effectiveness of metallic bond formation, which can support the chemical stability of rare-earth nitrides with retention of catalytic functionality.

Approach to Chemically Durable Nickel and Cobalt Lanthanum‐Nitride‐Based Catalysts for Ammonia Synthesis

AbstractMetal nitride complexes have recently been proposed as an efficient noble‐metal‐free catalyst for ammonia synthesis utilizing a dual active site concept. However, their high sensitivity to air and moisture has restricted potential applications. We report that their chemical sensitivity can be improved by introducing Al into the LaN lattice, thereby forming La−Al metallic bonds (La−Al−N). The catalytic activity and mechanism of the resulting TM/La−Al−N (TM=Ni, Co) are comparable to the previously reported TM/LaN catalyst. Notably, the catalytic activity did not degrade after exposure to air and moisture. Kinetic analysis and isotopic experiment showed that La−Al−N is responsible for N2 absorption and activation despite substantial Al being introduced into its lattice because the local coordination of the lattice N remained largely unchanged. These findings show the effectiveness of metallic bond formation, which can support the chemical stability of rare‐earth nitrides with retention of catalytic functionality.

Low-energy electron interaction and focused electron beam-induced deposition of molybdenum hexacarbonyl (Mo(CO)6).

Motivated by the potential role of molybdenum in semiconductor materials, we present a combined theoretical and experimental gas-phase study on dissociative electron attachment (DEA) and dissociative ionization (DI) of Mo(CO)6 in comparison to focused electron beam-induced deposition (FEBID) of this precursor. The DEA and DI experiments are compared to previous work, differences are addressed, and the nature of the underlying resonances leading to the observed DEA processes are discussed in relation to an earlier electron transmission study. Relative contributions of individual ionic species obtained through DEA and DI of Mo(CO)6 and the average CO loss per incident are calculated and compared to the composition of the FEBID deposits produced. These are also compared to gas phase, surface science and deposition studies on W(CO)6 and we hypothesize that reductive ligand loss through electron attachment may promote metal–metal bond formation in the deposition process, leading to further ligand loss and the high metal content observed in FEBID for both these compounds.

Fabrication and the impact of Fe and Al substitution on structural, morphological, vibrational and optical properties of Fe: Al co-doping zinc oxide nanostructured thin films developed by Arduino based spin coating device

Iron (Fe) and Aluminum (Al) co-doping nanostructured Zinc oxide (ZnO) films were fabricated at various Fe doping concentrations (3 wt%, 5 wt%, and 7 wt%) using the Arduino based spin coating device. In this report, the influence of Fe doping concentration on crystal microstructure and optical properties of Fe: Al co-doping ZnO films were investigated. The structural and optical characteristics of the material were determined using x-ray XRD and UV–VIS spectroscopy. SEM-EDS analysis was used to determine the surface morphology and elemental composition. XRD analysis confirmed the existence of a polycrystalline hexagonal ZnO phase. When the Fe content was increased, it was found that the crystalline quality of the deposited films deteriorated. The optical spectra revealed a transparency range of 85% to 75%. The film with Fe 7 wt% and Al wt3% dopant concentrations exhibited an optical band gap of 3.30 eV. Non-linear optical properties such as non-linear refractive index, non-linear susceptibility using the linear refractive index and energy gap were calculated. The linear refractive index was determined using a variety of models. The non-linear optical properties observed demonstrated a significant dependency on dopant concentrations. The non-linear refractive index and non-linear susceptibilities of the deposited co-doping films are 4.12×10-11-4.67×10-11esu and 2.54×10-12-2.92×10-12esu respectively. SEM analysis of all films demonstrates the growth of nanoscale crystal grains. FTIR spectroscopy verified the zinc oxide metallic bond formation in (Fe, Al) co-doping ZnO thin films.

The attachment-detachment mechanism of ionic/nanoscale/microscale substances on quartz sand in water

The attachment-detachment of heavy metal ions and suspended matter (SM), such as copper ions (Cu2+), graphene oxide (GO) and silica powders, onto a quartz sand porous medium (SiO2 particles) in water was investigated. The experimental results showed that the attachment-detachment process can be described by a nonlinear model. The detachment curves appeared as a group of parallel scanning curves. The attachment/detachment curves ranged from linear to nonlinear for copper ions, GO and silica powders (ranging from ions to particles). Finally, a unified static attachment-detachment model was established. The attachment mechanism mainly involved the interfacial electrostatic attraction between SM and the solid matrix, the formation and directional adjustment of metal bonds, and the complementary molecular structure characteristics of the different materials. The irregular motions of Cu2+, GO and silica powder were significantly enhanced by increasing the temperature.

Experimental investigation of Cu-SS electromagnetically assisted adhesive tube-to-tube joining: Its advantages over electromagnetic crimping

Electromagnetically assisted adhesive joining (EAAJ) is a novel hybrid joining technique combining the benefits of electromagnetic crimping and adhesive joining. This paper explores the possibility of creating an interference-fit tubular adhesive joint with improved strength and leak tightness. An acrylic-based structural Loctite 638 adhesive is used. Experiments are performed with and without (electromagnetic crimping) adhesives. Pull-out and compression test is performed for both joining techniques which has confirmed a significant improvement in joint strength with adhesives. A two-factor ANOVA analysis is also performed to calculate the contribution of adhesives and discharge energy over pull-out and compressive strength of the joint. An air leak testing setup is developed to investigate the leak tightness of the Cu-SS tube-to-tube Joint. Leak tightness is observed to be increased by ten times in the case of EAAJ compared to EMC. Macrographs have revealed no metallic bond formation. Deformation analysis is also performed to study the various zones of the samples. Micro-hardness is observed to be decreased for the adhesive joint in the adhesive zone.

Atomically Precise Insights into Metal–Metal Bonds Using Comparable Endo-Units of Sc 2 and Sc 2 C 2

The precise identification of metal–metal bonds is critical to fully understanding the nature of metal–metal bonding but remains a fundamental challenge. Herein, we show the essence of Sc–Sc bonds ...

Interference-fit joining of Cu-SS composite tubes by electromagnetic crimping for different surface profiles

This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC). Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy. Joints exceeding the strength of the parent tube are formed without any metallic bond formation. Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube. Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles. Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 6.2 kJ, which has shown a failure in the parent Cu tube during all three destructive testings. Radial deformation of the tubes is measured and compared for different discharge energy and surface profile. No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis. Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion. Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact.