Advanced Powder Materials最新文献

Co-catalysts decorations provide unique opportunity in promoting the photocatalytic water splitting performance of graphite carbon nitride (g-C₃N₄) system, while mechanistic understanding of this complex catalytic network remains elusive. Here, taking the single-atom-based photocatalysts (M₁-g-C₃N₄) as an unprecedented simplified model system, we theoretically tracked the photocatalytic kinetics for a comprehensive understanding of the photocatalytic process and afforded the descriptor α_S1-T1/α_T1-S0 (ratio of the extent of S₁-T₁ and T₁-S₀ state mixing) and ΔG_H∗ (hydrogen adsorpti on free energy) for rational screening of photocatalysts. The targeted Fe₁-g-C₃N₄ yields an excellent H₂ evolution rate (ca. 3.2 ⋅mmol·g_cat⁻¹·h⁻¹ under full arc), two order of magnitude improvement relative to pristine g-C₃N₄ counterpart and also outperforms other representative 3d-transition-metal-based photocatalysts. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic course and sheds light on the design of photocatalysts from both photophysical and photochemical aspects.

MXenes are an emerging class of new two-dimensional materials, which have been widely used in energy storage, catalysis, sensing, biology, and other fields due to their unique structure and properties. The distinct structure, low shear resistance, and easy-to-modify ability endow MXenes with particularly superior lubrication potentials. This review highlights the research status and applications of MXenes lubrication categorized into solid lubricants, lubricant additives, and reinforcement phase parts, summaries the influencing factors and lubrication mechanisms of MXenes lubrication, points out some unexplored research fields and unsettled questions, and then puts forwards possible solutions and prospects for the future research. The lubrication advances and potentials of MXenes are fully verified. Predictably, the emerging MXenes lubricants will exhibit remarkable application prospects in advanced manufacturing such as machining industries, automotive industries, micro/nano-electromechanical systems, and spacecraft components.

In this study, we performed first-principles calculations to determine the effects of four metallic solutes (Y, Zr, Mg, and Zn) on the hydrogen embrittlement (HE) of aluminum alloys with the Σ5(210) grain boundary (GB). The segregation energy, associated segregation concentration, and binding energy of these solutes were examined to identify their states. Moreover, the ability of the aforementioned solutes to inhibit or promote HE in the aforementioned alloys through GB energy, free surface energy, and adhesion was investigated. The Griffith and Rice–Wang–Scheiber models were used to determine the effect of nonequilibrium concentration on adhesion. Tensile tests were performed using the uniaxial strain loading method to determine the ultimate tensile strength and GB elongation of the considered alloys. The mechanism of HE inhibition by the four solutes was investigated by examining the charge density, Bader charge, and crystal orbital Hamiltonian population of the alloys. Finally, the calculation results of this study were validated through experiments.

Considering the risk of a sudden degeneration caused by the oxidation of MXenes in dielectric and microwave absorption properties, to enhance the oxidation resistance of multilayer MXenes can make them more applicable as microwave absorbers than those with few-layer. However, there remains disadvantage in optimizing the poor impedance matching and inherent aggregation of multilayer MXenes via rational assembling. In the present study, a facile self-assembly process is conducted to obtain 2D MXenes/1D MnO₂/0D NiCo₂S₄ assembled low-dimensional aggregate with hierarchical structure and interlaminar electromagnetic synergy network. In addition to bridging adjacent MXenes lamellas for the enhancement of internal electron transport, high-density MnO₂ can also combine with NiCo₂S₄ to form an electromagnetic synergy network between lamellas, thus improving microwave attenuation. Though the modulation of components and assembled structures, it is achievable to effectively adjust and optimize the performance in impedance matching and microwave absorption. Given the thickness of 2.17 ​mm, the optimal reflection loss of −59.23 ​dB, and the effective absorption bandwidth of 5.8 ​GHz are achieved. Moreover, the RCS simulations is performed to demonstrate its excellent performance. Thus, the present work contributes a facile method to the development of multi-layer MXenes based-MAs via interlaminar electromagnetic network design.

Aqueous Zn metal batteries have become competitive electrochemical energy storage systems owing to their material abundance, low cost, high capacity, and nontoxicity. Nevertheless, the notorious Zn dendrites and poor anode reversibility caused by the insulating by-products and “dead Zn” are still formidable challenges for their practical application. Herein, an SnS-based layer coated on the Zn anode is reported to tackle these problems. The semiconducting SnS with a higher work function can drive the electrons from the Zn anode, which constructs a polarized interface between the SnS layer and Zn. The semiconducting importance of the coating layer is verified through theoretical simulations, which can migrate the polarization layer from the electrode surface to a well-protected spot beneath the coating layer. This polarization interface is effective in homogenizing the Zn²⁺ flux and repelling the anions from electrochemical corrosion. Compared with the bare Zn, the SnS-coated Zn anode exhibits a notable 14.7-fold enhancement in plating/stripping lifetime (over 3000 ​h), high reversibility (with CE of 99.74%), and superior stability in full cells when paired with vanadium- and manganese-based cathodes.

Quasicrystal (QC)-reinforced metal matrix composites fabricated by rapid solidification present promising new opportunities to develop high-strength alloys with multiple functions. In this research, specially designed Al–Fe–Cr samples possessing an Al–Fe–Cr quasicrystal-reinforced Al matrix structure were manufactured using a laser powder bed fusion (LPBF) process. Based on the optimized process parameters of laser scanning speed and hatch distance, an almost dense (99.8%) free-crack sample was obtained with the multiscaled heterogenous structure induced by the nonuniform rapid solidification in a single molten pool. The results show that nanosized Al–Fe–Cr quasicrystalline particles of different sizes are heterogeneously distributed in the α-Al columnar grain structure. In detail, the coarse flower-like and spherical QC particles can be observed at the molten pool boundary, and the fine spherical Al–Fe–Cr QC is located inside the laser fusion zone. The orientation relationship between the Al matrix and the icosahedral Al–Fe–Cr QC is as follows: Al [ ​− ​112 ] ∥ i5 with a semicoherency feature. The novel designed LPBF-processed Al–Fe–Cr alloy exhibits high mechanical strength due to the ultrafine multireinforced microstructure-induced Orowan strengthening effect. For instance, the ultimate tensile strength, yield strength and elongation of the sample processed with LPBF are 530.80 ​± ​3.19 ​MPa, 395.06 ​± ​6.44 ​MPa, and 4.16% ​± ​0.38%, respectively. The fractographic analysis shows that the fracture mechanism presents a combination of ductile‒brittle fracture.

In order to uniformly disperse the ceramic reinforcements synthesized in-situ in the copper matrix composites, this study used Carbon Polymer Dot (CPD) as the carbon source and Cu–1.0%Ti alloy powder as the matrix for supplying Ti source to prepare in-situ synthesized TiC/Cu composites. The results show that TiC nano-precipitates, having the similar particle sizes with the CPD, form at the grains interior and grain boundaries, and maintain a uniform distribution state. Compared with the matrix, 0.3 ​wt% CPD/Cu composite displays the best strength-plastic compatibility, the ultimate tensile strength achieves 385 ​MPa accompanied with a corresponding elongation of 21%, owing to the dislocation hindrance caused by nano-carbide and excellent interface bonding between nano TiC and the Cu matrix. The density function theory calculation supports our experimental results by showing a tighter and stronger interface contact. This work presents a new approach for studying in-situ carbide precipitates.

Fabrication of the Mg–9Al–1Zn–0.5Mn alloy with excellent mechanical performance using selective laser melting (SLM) technology is quite difficult owing to the poor weldability and low boiling point. To address these challenges and seek the optimal processing parameters, response surface methodology was systematically utilized to determine the appropriate SLM parameter combinations. Mg–9Al–1Zn–0.5Mn sample with high relative density (99.5 ​± ​0.28%) and favorable mechanical properties (microhardness ​= ​95.6 ​± ​5.28 HV_0.1, UTS ​= ​370.2 ​MPa, and A_t ​= ​10.4%) was achieved using optimized SLM parameters (P ​= ​120 ​W, v ​= ​500 ​mm/s, and h ​= ​45 ​μm). Sample ​is dominated by a random texture and microstructure is primarily constituted by quantities of fine equiaxed grains (α-Mg phase), a small amount of β-Al₁₂Mg₁₇ structures (4.96 ​vol%, including spherical: ${\left[2\overline{1}\overline{1}0\right]}_{\alpha }$// ${\left[111\right]}_{\beta }$ and long lath-like: ${\left[2\overline{1}\overline{1}0\right]}_{\alpha }$// ${\left[1\overline{1}5\right]}_{\beta }$ or ${\left[\overline{1}011\right]}_{\alpha }$// ${\left[3\overline{2}\overline{1}\right]}_{\beta }$), and some short rod-shaped Al₈Mn₅ nanoparticles. Benefiting from grain boundary strengthening, solid solution strengthening, and precipitation hardening of various nanoparticles (β-Al₁₂Mg₁₇ and Al₈Mn₅), high-performance Mg–9Al–1Zn–0.5Mn alloy biomedical implants can be fabricated. Precipitation hardening dominates the strengthening mechanism of the SLM Mg–9Al–1Zn–0.5Mn alloy.

Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr_0.375Nd_0.375Yb_0.25)₂(Ti_0.5Hf_0.25Zr_0.25)₂O₇]_1-x[(DyHoErNb)O₇]_x, denoted as 10CCFBO_xNb. A long-range order-disorder transition (ODT) occurs at x ​= ​0.81 ​± ​0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x ​= ​0.75, 0.8, 0.85, and 1) can be better fitted by C222₁ weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO_0.75Nb and 10CCFBO_0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT.

Regulating dielectric genes of hollow metal-organic frameworks is a milestone project for microwave absorption (MA). However, there is still a bottleneck in deciphering the contribution of various dielectric genes, making it hard to expand the MA potential from selective encoding gene sequences. Herein, a custom-made proton tailoring strategy is used to build a controllable cavity, and meticulously designed thermodynamic regulation promotes the rearrangement of carbon atoms from disorder to order, thus enhancing the characteristics of charge transfer. Meanwhile, the defect-configuration transformation from heteroatom to vacancy and geometric configuration of hollow structure increase the polarization-related dielectric genes. Therefore, MA performance is enhanced towards broadband absorption (6.6 ​GHz, 1.78 ​mm) and high-efficiency loss (−62.5 ​dB), making samples suitable for complex open electromagnetic environments. This work realizes the tradeoff between dielectric gene sequences and provides a profound insight into the functions and sources of various microwave loss mechanisms.