Journal of Materials Science最新文献

In order to satisfy the requirements of various structure and manufacturing process, the machining processes would be applied to the two components of the joint structure, resulting in a significant thickness disparity between them. Additionally, the heat transfer during laser welding can affect the microstructure of the joint. Therefore, this study investigated the microstructural evolution and corrosion resistance mechanisms of the laser-welded 304 water pipe parent material and receiver parent material. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), potential dynamic polarization analysis, and electrochemical impedance spectroscopy (EIS) were utilized in this study. According to research, the internal structure of the stainless steel nozzle was significantly changed after a high-temperature thermal cycle during laser welding. Recrystallization occured within 254 μm of the fusion line, leading to the formation of equiaxed crystals with fine grains. Due to the reversibility of the martensitic transformation, most of the martensite reversely transformed to austenite within the range of 254– 278 μm of the fusion line. In the region beyond 278 μm from the fusion line, the degree of martensite reverse transformation was minimal. Compared to the nozzle parent material that was deformation processed twice before welding, the volume fraction of martensite after welding is lower, resulting in a slower corrosion rate and higher corrosion resistance. Furthermore, it was found that the welded joints exhibited superior corrosion resistance compared to the cold-rolled nozzle parent material, while the cold-rolled, stamped, and deep-drawn nozzle parent material showed the lowest corrosion resistance.

To more rationally and effectively handle and utilize solid wastes, this study explored the preparation of superior performance green backfill materials under alkaline activation conditions. Using waste stone limestone powder (LP), slag powder (SP), and fly ash (FA) as cementitious materials, coal gangue (CG) as fine aggregate, and incorporating polypropylene fibers (PP) of different lengths and contents, a ternary solid waste-cemented coal gangue green backfill material (LSFCLs + Ps) was developed. The mechanical properties and deformation characteristics of LSFCLs + Ps were investigated through splitting tensile strength (STS) tests, uniaxial compression strength (UCS) tests, digital image correlation (DIC), and scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS). The results indicate that: (1) When the fiber length is 9 mm and the content is 0.3%, the STS and UCS reach optimal values of 1.05 MPa and 7.53 MPa, respectively, which are 56.72% and 45.93% higher than those of the control group. (2) The addition of PP enhanced the deformation resistance of LSFCLs + Ps, improved the efficiency of elastic strain energy conversion, and reduced the energy consumption ratio of the backfill. (3) The effective bonding of PP with hydration products improved the overall density of the samples, inhibiting the formation and propagation of internal cracks. The research findings provide a theoretical basis for the treatment of coal gangue and the development of new backfill materials in mining areas.

The present work aims to compare the multiferroic and magnetodielectric (MD) properties of BaTiO₃–CoFe₂O₄ (BTC) and BaTiO₃–NiFe₂O₄ (BTN) composites, both with 15 wt.% ferrite content. The BTC, BTN, and their pristine samples (BaTiO₃, CoFe₂O₄, and NiFe₂O₄) were prepared via the solid-state process. These composites’ microstructure, dielectric, ferroelectric, ferromagnetic, and MD properties were investigated and compared. XRD patterns revealed the diminution of the tetragonality factor (c_T/a_T) of the BaTiO₃ (BTO) system in both composites; however, the BTO’s unit cell showed an expansion in the BTC and a shrinkage in the BTN. Furthermore, the FESEM images indicated a uniform dispersion of the ferrites within the matrix, confirming the successful particulate composition of the samples. Moreover, the BTC showed higher values of the dielectric (ε_r ~ 1676 and tan δ ~ 0.45) and ferroelectric (P_S ~ 11.33 μC/cm² and P_r ~ 9.28 μC/cm²) properties compared to the BTN composite. In addition, higher ferromagnetic properties (M_S ~ 7.14 emu/g and H_C ~ 377 Oe) for the BTC sample were obtained than those of the BTN composite (5 emu/g and 112 Oe). The multiferroicity of both BTC and BTN composites was validated due to the simultaneous observation of the ferroelectric and ferromagnetic characteristic hysteresis loops. The BTC’s MD coefficient was about 30% larger compared to the BTN at the applied magnetic field of 7 kOe.

Given the diversity in the structures of the substrates and the types of active transition metal atoms, using machine learning to screen two-dimensional conductive MOFs for high-performance OER catalytic materials can significantly save time and cost. This paper collected data from 413 catalysts composed of 20 different carbon substrates and 26 metal elements as the training dataset, constructed a series of two-dimensional conductive MOFs structures, and predicted their OER catalytic performance using the trained model. Additionally, density functional theory was used to systematically study the adsorption of OER intermediates *OH, *O, and *OOH on TMO_XN_4-X-OHPTP (TM = Fe, Co, Ni;X = 0–4), and the reaction overpotentials were calculated. The results show that CoO₄-OHPTP(ML/DFT:0.269 eV/0.237 eV), CoO₃N₁-OHPTP(ML/DFT:0.287 eV/0.239 eV), CoO₂N₂-I-OHPTP(ML/DFT:0.302 eV/0.241 eV), CoO₂N₂-II-OHPTP(ML/DFT:0.293 eV/0.295 eV), CoO₁N₃-OHPTP(ML/DFT:0.336 eV/0.300 eV), and CoN₄-OHPTP (ML/DFT:0.311 eV/0.33 eV) have overpotentials lower than RuO₂(η_*OER = 0.37 eV), which are consistent with the predicted results by machine learning. Through model analysis, apart from the properties of metal atoms, it is found that the number and types of different atoms in the substrate and the bond lengths between TM metal atoms and surrounding coordinating atoms are important descriptors that significantly affect the overpotential. Finally, the trained model was used to predict more 2D c-MOFs(TMO_XN_4-X-OHPTP and TMO_XN_4-X-TBC), identifying 18 additional potential OER catalysts.

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TiNb₂O₇ (TNO) is a promising anode for lithium-ion batteries owing to its high theoretical capacity, minimal volume expansion, and effective suppression of lithium dendrite formation. Nonetheless, the low electrical conductivity of TNO presents a barrier to practical application. Thus, a Mo⁶⁺ doping strategy was utilized to address the conductivity issue, and TNO-xMo (x = 0, 0.05, 0.10, 0.15, 0.20) anodes were prepared by a solid-state method. The incorporation of Mo⁶⁺ ions result in a charge redistribution, which can elevate electronic conductivity and accelerate ion diffusion. What’s more, by precisely controlling the Mo⁶⁺ ion concentration can regulate the morphologies of the TNO, enabling it to expose more fast-ion conducting (020) facets. The synergistic effect of the above two factors significantly enhances the conductivity and electrochemical properties of the TNO anode. As a result, the optimal TNO-0.05Mo with 2D lamellar structure exhibits a high discharge capacity of 347.6 mAh g⁻¹ at 0.1C, superior rate performance, and an excellent cycle lifespan, with retention of 78% after 1500 cycles at 1.5C/1.5C. Meanwhile, the solid-state battery with TNO-0.05Mo as anode also displays improved rate and cycle performance than the liquid-state battery, indicating the great application potential for the next-generation energy storage devices.

Zirconium oxide-based catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells were synthesized via heat treatment of zirconium polyacrylate in an NH₃ atmosphere. The effects of gas atmosphere and heat treatment temperature on the material structure were systematically examined. The formation of zirconium oxide nanoparticles and carbon residues, which act as electron conduction paths, was observed in all samples. The structure of the material varied significantly depending on the heat treatment conditions. The samples heat-treated in the NH₃ atmosphere showed greater exposure to zirconium oxide nanoparticles and an increase in the specific surface area of the carbon residue caused by NH₃-induced etching. In addition, the conductivity of the carbon residue increased, and its quantity decreased with increasing heat treatment temperature. This trade-off was optimally controlled at 800 °C, which resulted in a high rest potential and a large ORR current density. This study demonstrates that the heat treatment of organometallic complexes in an NH₃ atmosphere is highly effective for exposing metal oxide nanoparticles and increasing the specific surface area of the carbon residue, providing valuable insights into the design of electron conduction paths for metal oxide-based catalysts.

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This work presents the effect of the rapid thermal annealing (RTA) process on the performance of Ti/MoO_x/Pt resistive random access memory (RRAM). Compared with the device without RTA treatment, the device processed in vacuum RTA (300 ℃,80 s) exhibits better resistance switching (RS) characteristics, including smaller forming voltage (V_f = 5.7 V) and set voltage (V_set = 1.41 V), stable high-resistance state (coefficient of variation = 5.91%) and 100 times storage window. This may be attributed to changes in oxygen vacancies (V_O) content. The X-ray diffraction (XRD) analysis results indicate that the prepared MoO_x thin films are all amorphous. X-ray photoelectron spectroscopic (XPS) analysis results indicate that vacuum RTA treatment increases the V_O content in the MoO_x dielectric layer, which may make it easier for thick conductive filaments to form. This leads to a reduction in the V_f and V_set, while also establishing a relatively fixed fracture position for conductive filaments, thereby achieving a stable high-resistance state. XPS depth profiling results of Device B before and after applying positive voltage indicate the formation of TiO_x layer at the interface and the increase of V_O in the MoO_x dielectric layer (33.90% → 55.37%), which may indicate the establishment process of V_O conductive filaments in the device. In addition, we have explored synaptic applications of RRAM devices with this structure and simulated a range of synaptic behaviors, demonstrating the potential of MoO_x-based RRAM as an artificial synaptic device in neural morphology computing systems.

Ternary metal sulphide nanocomposites are gaining prominence for their energy storage properties and applications. In this work, ternary NiCdS₂ (NCS) nanocomposites were prepared via standard solvothermal method. Rietveld examination of the PXRD was revealed cubic NiS₂ and hexagonal CdS phases in NCS nanocomposites. The electron density, average crystallite size, crystalline parameters, micro-strain and dislocation density were determined. EDX analysis confirmed the elemental composition, while XPS was used to investigate the chemical states and bonding environments of Ni, Cd and S. Ellipsoid morphology with particle size in the ranging of 20–60 nm was investigated using HRTEM. Electrochemical behaviours were investigated through cyclic voltammetry and galvanostatic charging/discharging, which shows quasi-rectangular shape curve with higher specific capacitance and fast-charging and slow-discharging rate. Complex impedance/modulus spectra, dielectric properties and electrical conductivity were investigated at temperatures ranging from 308 to 423°K at various frequencies. Nyquist plots demonstrate two RC-equivalent circuits owing to the contribution of grains and grain boundaries, which investigates the non-Debye-type dielectric relaxation in NCS. The dielectric constant increased with temperature and found to be more than 10000 (huge) at higher temperature/low frequencies and the dielectric loss was exhibited an increasing trend with temperature. The correlated barrier hopping (CBH) model was adopted to explain the mechanism of conduction through Jonscher’s power law. The hopping parameters, like binding energy, activation energy, minimum hopping distance and density of states at fermi level, were evaluated at various temperatures. Furthermore, the non-Debye-type nature of the relaxation in the NCS has been established by using the Kohlrausch–Williams–Watts (KWW) model to complex modulus spectra. NCS nanocomposites were identified as potential alternates for energy storage devices because to their higher dielectric constant values and superior electrochemical performance.

Graphical Abstract

Compared to commercial lithium-ion batteries, lithium-sulfur (Li–S) batteries offered exceptionally high theoretical specific capacity (1675 mAh g⁻¹) and theoretical energy density (2600 Wh kg⁻¹), positioning them as promising alternatives of conventional Li-ion batteries. However, several key challenges, including shuttle effect of lithium polysulfides (LiPSs), capacity fade, volume expansion of the sulfur electrode, and poor conductivity, have hindered the progress of Li–S batteries. In our research, we employed lignosulfonate as a novel sulfur host. And the active sulfur was synthesized and uniformly deposited onto lignin-derived porous carbon. Electrochemical analysis revealed that this sulfur cathode, based on lignin-derived porous carbon hosts containing up to 60.31 wt% sulfur, delivered an outstanding high-rate capacity of 1099.95 mAh g⁻¹ at 0.10 C. The interconnected porous structure of this biomass-derived carbon not only accommodated the volume expansion of active sulfur but also facilitated ion and electron transport, effectively trapped LiPSs and enhanced sulfur utilization. Additionally, the synthesized nanosulfur, characterized by its stable morphology and abundant chemical reaction sites, further improved the utilization of active sulfur. Our work presents a viable solution for the development of composite cathodes for Li–S batteries utilizing biomass-derived carbon materials and nanosulfur.

Graphical abstract

Lignin-derived porous carbon (LDPC) with heteroatom doping act as efficient sulfur hosts for the adsorption and catalytic conversion of polysulfides. Chemically synthesized nano-sulfur (NS) serves as an excellent active material. Benefiting from the green and environmentally friendly raw materials of LDPC, its unique porous structure, and various heteroatom doping, along with the regular structure and abundant active sites of NS, the NS@LDPC cathode significantly improves the electrochemical stability of lithium-sulfur batteries.