Bulletin of Materials Science最新文献

Effect of Nb element on the microstructure and mechanical properties of Co–8.8Al–9.8W superalloy was analysed by studying the occupancy of Nb element in the lattice and difference in the microstructure evolution during deformation. The calculation results show that Nb atom occupies the first priority position of Al₂ and the second priority position of W₆, forming a γ′ phase doped structure, and its strength, hardness and structural stability are improved. In the process of high-temperature deformation, the dislocations of 0Nb alloy have the mechanisms of cutting and bypassing, which makes strengthening phase rafting phenomenon, and dislocation propagation in 2Nb alloy is difficult, and there are a lot of stacking faults. Compared to 0Nb alloy, 2Nb alloy has improved nano-indentation hardness and elasticity modulus.

Copper matrix composites with NbC content of 1 wt.% and La content of 0.02 wt.%, 0.04 wt.%, 0.06 wt.%, and 0.08 wt.% were prepared by high-energy ball milling and spark plasma sintering using rare earth element La, ceramic particle NbC, and electrolytic copper powder as raw materials. The effects of different La content on the properties of NbC-Cu composites were discussed by observing the microstructure of La-NbC-Cu composites and testing the hardness and conductivity. When the content of La is 0.06 wt.%, the La-NbC-Cu composite has a hardness of 62 HV and a good conductivity of 76.5% IACS. At this time, the internal stress of the material is reduced and ultrafine grains appear. Then, with the increase of La element, when the content of La is 0.08 wt.%, the hardness of copper matrix composites decreases due to the enrichment of La atoms on the surface of the reinforced phase.

Oxidation behaviour of a third-generation Ni-based single-crystal superalloy was investigated at 900 and 1050°C by scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The alloy showed non-uniform oxidation behaviour in dendritic and interdendritic regions. Re and W were enriched in the dendritic region, leading to the formation of Re₂O₇ and WO₃, which were easy to volatile. As a result, the film in the dendritic region was loose and contained number of pores, providing an easy path for the outward diffusion of cations and inward diffusion of O²⁻. Moreover, the high Pilling–Bedworth ratio of Ta₂O₅ accumulated in the dendrite region, resulting in the occurrence of cracking and cyclic oxidation behaviour. Eventually, the synergistic effect between the loose oxide film and cyclic oxidation leads to more severe oxidation behaviour in dendritic regions of the alloy compared to interdendritic regions.

Graphical abstract

Supercapacitors’ high power density and extended life cycle have drawn a lot of interest in energy storage devices. In this study, different nanostructures of nickel oxide (NiO) and zinc oxide (ZnO) were synthesized using the hydrothermal method by treating the corresponding metal precursors in a high-temperature aqueous solution. The XRD and SEM were used to analyse crystal structure and morphology, respectively. The absorption of ZnO and NiO materials is found to be in the visible range of 300–400 and 200–300 nm, respectively. The band gap of ZnO was calculated as 3.04 eV, while that of NiO was 3.93 eV. The supercapacitor electrode was fabricated on nickel foam with developed nanostructure and carbon materials. The composite ZnO and NiO materials showed an increase in capacitance compared to the bare NiO and ZnO electrodes. This enhancement could be related to improved charge transfer kinetics and increased surface area for electrolyte interaction. Galvanostatic charge–discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements were conducted to assess the electrochemical efficiency of nanomaterials and their composites. At the current density of 2 A g⁻¹, the specific capacitance of the NiO/ZnO composite is found to be 351.54 F g⁻¹, which is ~2 times of the bare NiO and ~3.34 times of bare ZnO. The maximum energy density of ZnO nanoparticles, NiO nanoflakes and the composite are found to be 3.96, 6.58 and 13.90 Wh kg^-1, respectively. The charge storage process is the result of diffusion and redox reactions. This paper explores a binary oxide composites method for creating efficient supercapacitor electrode materials.

Polycrystalline cubic boron nitride (PcBN) composites were prepared through high-temperature and high-pressure (HTHP) sintering process. Cubic boron nitride (cBN) powders with particle sizes of 0.2, 1, 3, and 8 μm were selected as raw materials, and Al-Co-TiN was employed as a binder. The effect of particle size of initial cBN powders on the microstructure, relative density, flexural strength, microhardness, fracture toughness and abrasive ratio of sintered PcBN composite were systematically studied. The results showed that synthesized products were mostly made of cBN, TiN, AlN, TiB₂ and CoN phases. The mechanical properties of sintered PcBN composites first increased and then decreased with a reduction in the particle size of cBN powders. When the particle size of initial cBN powder was 1 µm, the binder was observed to be evenly distributed around the cBN grains in the sintered product. Moreover, there was a close bonding between cBN grains and the binder in the sintered product when the particle size of initial cBN powders was 1 µm, consequently, the optimal mechanical properties were achieved. The maximum values for relative density, flexural strength, microhardness, fracture toughness and abrasive ratio were 99.1%, 607 MPa, 47.06 GPa, 6.52 MPa·M^1/2 and 7125, respectively.

Upon polycondensing, the monosodium salt of 2-sulphoterepthalic acid and 3,3′-diaminobenzidine resulted in sulphonated polybenzimidazole (s-p-PBI; amphiphilic polymer). The amphiphilic polymer was blended with commercially available sulphonated poly(arylene ether sulphone) (SPAES; acid polymer; IEC = 2.08 meq g⁻¹). The s-p-PBI content in blend composition is varied from 2.5 to 30% (w/w). ATR-FTIR spectroscopy and TG analysis were examined to identify the interactions between the polymers upon blending. Cross-sectional morphology was analysed through SEM. With amphiphilic polymer addition, chlorine (hypochlorite) stability decreased and tensile strength improved. All the blend membranes showed improved water transport or restricted salt permeability than the pristine membrane (acid polymer). Water diffusivity permeability (P_w) of blend membrane AC-AM-97.5 (i.e., 97.5% (w/w) of SPAES and 2.5% (w/w) of s-p-PBI) is 1.285 cm² s⁻¹, while the pristine membrane is 0.864 cm² s⁻¹. NaCl permeability selectivity (P_w/P_s) of AC-AM-97.5 is 0.208 × 10³, whereas pristine membrane shows 0.102 × 10³.

In this work, Ni²⁺ was doped into the crystal lattice of LiFePO₄ to improve the electrochemical performance. Lengths of the Li–O bonds in LiFe_0.98Ni_0.02PO₄/C (2% NiSO₄-doped LiFePO₄) is longer than that of the bare LiFePO₄ sample, the micromorphology of LiFe_0.98Ni_0.02PO₄/C sample becomes uniform, and the Ni²⁺ doped into LiFePO4 expands the crystal plane spacing, which is conducive to Li⁺ diffusion. Amongst all the doped samples, the Li⁺ diffusion coefffcient of LiFe_0.98Ni_0.02PO₄/C is the largest, and the redox peak of LiFe_0.98Ni_0.02PO₄/C is more symmetrical, sharper and narrower, indicating that the proper amount of Ni^2+-modified LiFePO₄ can improve the electrochemical performance. Specific discharge capacity at 1C is 152 mAh g⁻¹ when the doping amount is 2%. Additionally, after 200 cycles at 2C, the discharge specific capacity can be attained at 140 mAh g⁻¹ and capacity retention rate reached 98%.

Polyvinyl butyral (PVB) integrated with varying compositions of potassium chloride (KCl) was prepared through a solution-cast method in methanol, forming a PVB-based electrolyte film for solid-state potassium batteries. The incorporation of KCl into PVB matrix significantly altered the composite electrolyte film’s structural intricacies, bandgap modulation, thermal stability and facilitated functional group identification. Furthermore, the ionic conductivity of the PVB polymer electrolyte exhibited an initial enhancement followed by a subsequent reduction with the escalating ratio of KCl. Specifically, at 80 wt% PVB and 20 wt% KCl, its ionic conductivity reached a value of 1.87 × 10⁻⁵ S cm⁻¹ at room temperature and 9.61 × 10⁻⁵ S cm⁻¹ at 303 K temperature. The ion transference number, which denotes the relative ease with which potassium ions migrate within the PVB polymer-complexed electrolyte, was determined to be 0.98. Discharge tests on the cell, under 1.2 µA current and 2.1 V at room temperature, displayed an initial 9.16 µA h⁻¹ discharge capacity.

Non-equilibrium Green’s function (NEGF) and density functional theory (DFT) calculations are used to explore the impact of doping on the electron transport properties in a single tetracene molecule linked to gold electrodes using isocyanide anchoring groups. Boron (B) and Nitrogen (N) atoms are used for doping and co-doping (BN) of the carbon atoms placed at the edge of the tetracene molecule. It was found that the chemical doping of tetracene molecules mainly impacts the rectification trends compared to non-doped molecules. Our findings indicate that B doping significantly improves the rectification ratio compared to other dopants because of a greater difference between the current values under positive and negative biases as a result of asymmetric I-V characteristics. These inferences have also been assessed in terms of MPSH and transmission spectra. In addition, novel characteristic of negative differential resistance (NDR) is attained in single dopant molecular junctions.

Additive manufacturing (AM) processes produce complex and multifunctional items by layering pre-alloyed powder. Among them, direct metal laser sintering (DMLS) process encourages creation of distinct microstructures and internal phase distributions. These microstructures possess substantial influence on corrosion performance and mechanisms of corrosion resistance-improving surface treatments, such as anodizing. Hence, this study emphasize on corrosion performance of anodized and unanodized heat-treated AlSi10Mg samples manufactured through DMLS method. As built AlSi10Mg samples were subjected to stress relieving and T6 heat-treatment. The heat-treated samples were further subjected to anodizing process in H₂SO₄ electrolyte solution. Microstructural characterization of unanodized and anodized heat-treated samples was performed through microscopy analysis. In addition, corrosion experiments were performed in 1 M H₂SO₄ solution on anodized and unanodized heat-treated samples to determine E_corr, I_corr and corrosion rate values. The corroded samples are further characterized to understand different failure mechanisms.