Progress in Natural Science: Materials International最新文献

Nowadays, an increasing number of scientists attach more importance to zero thermal expansion (ZTE) materials which are uncommon yet highly significant in the field of solid-state materials. The key to explore new ZTE compounds is to understand the mechanism, while it remains unclear. Here, we utilize density functional theory calculations to elucidate the mechanisms of NiPt(CN)₆. A joint study of bond nature, atomic mean-square displacements, phonon dispersion curves, Grüneisen parameters, and phonon vibrations to systematically analyze the ZTE mechanisms. The results suggest that the transverse vibrations of the –C≡N− groups are instrumental, particularly due to the involvement of the N atoms and the nature of the Ni–N and Pt–C bonds. Phonon modes with negative Grüneisen parameters at low frequencies play the mainly role to balance the positive thermal expansion from others frequency zone modes to obtain the ZTE behavior. This work demonstrates that NiPt(CN)₆ maintains substantial similarities with its trivalent-trivalent analogues, further enhancing our comprehension of NTE properties within open-framework structure.

Dead-ended proton exchange membrane fuel cells (PEMFC) using pure hydrogen oxygen can improve fuel efficiency and simplify fuel cell systems have been wildly used for a closed space. But the dead-ended operation of the PEMFC will cause difficulties in water management, especially in the cathode side, resulting in deteriorating of fuel cell stability. For this reason, gravity assisted drainage method, static drainage method are designed to migrate the water out of the cell. However, even with these methods, the reliability of the water removing from the cell remains questionable. Therefore, this paper introduces a novel water removal method to solve these problems and visualisation techniques were used to a more comprehensive knowledge of water transport mechanisms in dead-ended PEMFCs. A pressure-swing operation is realized by controlling the inlet of PEMFC solenoid valve to remove water and recycle oxygen during purging. The dynamic response characteristics of this system under different current densities, pressure differences, cell temperature and purging intervals are experimentally investigated in detail. It found that the water removal rate of the cathode flow channel of dead-ended PEMFC was as high as 99.25 ​%, and the fuel utilisation of the cell was close to 100 ​% in this water management mode.

In this paper, the microstructure evolution and properties of squeeze-cast Al–8Si-1.5Cu–1Ni-0.5Mg-0.5Mn-0.2V-0.2Ti-0.2Zr alloy (hereafter, Al–Si–Cu–Ni alloy for short) were investigated under various solution processes, evaluating the mechanical properties at room and elevated temperatures for both as-cast and T6-treated states. The results showed that following the optimal two-stage solution (i.e., solution at 510 ​°C for 6 ​h ​+ ​solution at 530 ​°C for 8 ​h) and subsequent aging at 190 ​°C for 10 ​h, referred to as the S530-T6 treatment, the Al–Si–Cu–Ni alloy exhibited excellent room/high temperature performance. The ultimate tensile strength (UTS), yield strength (YS) and elongation of the alloy at room temperature were 410 ​MPa, 368 ​MPa and 1.5 ​%, and the UTS, YS and elongation of alloy at 300 ​°C were 177 ​MPa, 170 ​MPa and 6 ​%, respectively. The increase in strength at room temperature is mainly attributed to the spheroidization of eutectic silicon and the precipitate strengthening aroused from uniformly dispersed nano-sized Q-Al₄Cu₂Mg₈Si₇, σ-Al₅Cu₆Mg₂ and θ′-Al₂Cu phases, while the increase in strength at high temperature is due to the formation of heat-resistant Ni-rich phases and the improvement of the micromorphology of high melting point intermetallic compounds.

The LiNi_0.83Co_0.12Mn_0.05O₂ (Ni-rich NCM) cathode materials have been widely studied owing to their high energy density and excellent rate capability. However, Ni-rich NCM is prone to form large amounts of lithium impurities and causes structural decline, resulting in inconvenient material storage. To this end, Li₄SiO₄/SiO₂ was used as a structural regulator to eliminate the residual lithium and convert the irreversible phase. The Li₄SiO₄/SiO₂ protective coating effectively suppresses the corrosion of the electrolyte by blocking the direct contact between the electrode and the electrolyte, while having a high air stability under the hydrophobic action. In addition, SiO₂ has excellent corrosion resistance, which further enhances the cyclic stability of the material. The obtained regenerated NCM material displayed a great capacity of 198.6 mAh g⁻¹ at 0.3 ​C and long cycling stability (capacity retention of 82.2 ​% after 250 cycles). This simple repair strategy significantly reduces the loss rate in industrial production and enhances the electrochemical performance while achieving material reuse.

The dual-phase competitive behavior is introduced as an effective strategy to optimize the physical and chemical properties of N-type Bi₂Te₃ thermoelectric (TE) materials. Controllable SnTe-embedded Bi₂Te₃ nanocomposites can be synthesized with the addition of excessive Sn into Bi₂Te₃ by tuning the crystallization behavior under proper thermal heating temperature. Notably, the precipitation temperature of Bi₂Te₃ increases from 473 ​K for Sn_20.9(Bi₂Te₃)_79.1 to 573 ​K for Sn_34.4(Bi₂Te₃)_65.6, expanding the controllable temperature span for the presence of SnTe phase. The second-phase nanoprecipitate SnTe can improve electrical conductivity by competing with the Bi₂Te₃ phase, achieving an increase of four orders of magnitude at the critical temperature of ∼500 ​K. Simultaneously, it increases the interfacial energy filtration effect between nanocrystalline grains, decoupling electrical parameters between conductivity and Seebeck coefficient. Consequently, the high power factor of ∼147 ​μW/mK² at 650 ​K for optimized Sn_26.6(Bi₂Te₃)_73.4 films can be obtained, which is more than twice that of the pure Bi₂Te₃ material. Our work demonstrates a new physical mechanism to unravel the complicated structure-property relationship by dual-phase competitive behavior during phase transition. This study fills the gap in knowledge on the effects of the SnTe phase regarding the Bi₂Te₃ system and provides guidance for the innovative design of high-performing inorganic thermoelectrics.

The impact of different Ta contents on the mechanical properties and thermoplastic forming ability of in-situ Ta-particle reinforced Zr–Cu–Al–Ni bulk metallic glass composites was studied. The composition (Zr₅₅Cu₃₀Al₁₀Ni₅)₉₄Ta₆ with the best comprehensive performance was chose for a systematic investigation into its thermoplastic behavior in the supercooled liquid region (SLR), with quantitative analysis conducted by the strain rate sensitivity index and activation volume. The steady-state flow stress and the stress overshoot intensity were augmented with deformation temperature decreasing, strain rate increasing, and the addition of the secondary phase, leading to a transition from Newtonian to non-Newtonian flow regime. The addition of the secondary phase deteriorated the rheological properties of the material. To solve the problem that the Maxwell-Pulse constitutive model showed an inability to accurately describe the steady-state flow process. A modified constitutive relationship, introducing the effect of the volume fraction of Ta particles on viscosity and elastic modulus in the steady-state flow process which was ignored in Maxwell-pulse model, was established. The fitting results of the true stress-strain curves of the modified Maxwell-pulse constitutive model were in better agreement with the experimental date than those of the Maxwell-pulse constitutive model, with higher prediction accuracy. The modified constitutive model well predicted the thermoplastic deformation behavior of (Zr₅₅Cu₃₀Al₁₀Ni₅)₉₄Ta₆. The influence mechanism of Ta particles on the flow behavior was explained that Ta particles increased the viscosity of amorphous matrix, thereby hindering its flow and ultimately leading to an increase in flow stress.

Spent galvanizing acid solution contains high concentrations of zinc salts, ferrous salts, and residual acids, exhibiting extremely high value-added recovery potential. However, achieving the efficient extraction and separation of Zn over Fe becomes particularly challenging under elevated Zn ion concentration. Here, the key extraction parameters, such as modifier ratio, Cyanex 923 concentration and ratio of organic phase to aqueous phase (O/A), are investigated. The stripping and regeneration of extractant, extraction mechanism, as well as high-value recovery of Zn and Fe resources are also comprehensively expounded. After the two-stage extraction, the extraction efficiency of Zn and Fe is 98.92 ​% and 2.09 ​%, respectively. Moreover, the stripping efficiency of Zn reaches 92.3 ​% with O/A ratio of 1 : 2, using oxalic acid as stripping agent. The predominant extracted species is confirmed to be $\text{Zn}{\text{Cl}}_3^{-}$, resulting in the formation of $\text{HZn}{\text{Cl}}_3\bullet R_3\text{PO}$ complex. More importantly, the regenerated extractant can be recycled back into the extraction process, and the reproduced HCl, high-value recovered ZnO and Fe₂O₃ can be used for different industrial fields. These findings lay a solid foundation for the efficient separation and comprehensive recovery of high-concentration spent galvanizing acid solution.

Earth-abundant Fe oxide-based catalysts, renowned for their broad-spectrum light absorption, hold promise for driving the photothermal RWGS reaction—a promising strategy for converting CO₂ emissions into valuable carbonaceous feedstocks. However, traditional Fe oxide-based catalysts exhibit limited activity due to their constrained H₂ dissociation and CO₂ activation capabilities, especially at lower temperatures. This study introduces Co, Ni, and Cu-doped Ce_0.7Fe_0.3O₂ solid-solution catalysts. Incorporation of Fe into CeO₂ enhances CO₂ dissociation while preserving extensive light adsorption up to 2500 ​nm. Notably, Co doping enhances H₂ dissociation and promotes CO₂ activation. Subsequent investigations reveal that a catalyst doped with 5 ​mol% Co exhibits the highest photothermal catalytic activity, attaining a ∼50 ​% CO₂ conversion under 300 ​W Xe-lamp irradiation with excellent selectivity and stability over 10 reaction cycles spanning 10 ​h. These results underscore the potential of designing CeO₂-based solid solution catalysts with synergistic metal dopants for efficient and selective CO₂ conversion under moderate conditions.

Using melt spinning technology, we successfully synthesized a series of Fe-rich Fe–P–C amorphous alloys exhibiting high saturation magnetization (B_s), low coercivity (H_c), and excellent bending ductility. These alloys exhibit low H_c values ranging from 4.1 to 7.2 A/m, and high B_s values ranging from 1.58 to 1.68 ​T. Particularly, after annealing at 588 ​K for 900 ​s, the Fe₈₃P₁₁C₆ amorphous alloy showed extraordinary soft magnetic properties: B_s up to 1.68 ​T, H_c only 4.7 A/m, and the core loss at approximately 1.5 ​W/kg under the condition of 0.5 ​T and 50 ​Hz, all of which surpass the reported Fe–P–C ternary amorphous and nanocrystalline alloys. These Fe-rich Fe–P–C alloy ribbon samples exhibit favorable bending ductility in both the as-spun and annealed states. Their simple alloy composition, outstanding soft magnetic properties, and excellent flexibility collectively make these soft magnetic alloys highly promising candidate materials for industrial applications.

This study focused on the microscopic strengthening and failure mechanisms of the Al matrix reinforced by graphene (Gr), and the effects of number of layers, chirality, and arrangement of Gr were calculated based on the molecular dynamics simulation. The results revealed that the Young's modulus and yield strength were significantly enhanced by the addition of Gr. In Gr/Al composites with monolayer Gr, the zigzag Gr exhibited a better ultimate strain than the armchair Gr, indicating that the plastic deformation was affected by the chirality, and the dislocation hindrance and load transfer were the dominated strengthening mechanisms. The crack in the armchair Gr was limited to follow straight paths, while that in zigzag Gr extended in a petal-like manner across multiple directions. In Gr/Al composite with multilayer Gr, the dispersing Gr showed a stronger strengthening effect than the stacking Gr, and the strengthening effect increased with increasing the volume fraction of Gr. The dispersing Gr strongly hindered the movement of dislocations, while the Al matrix in the composite with stacking Gr could retard the folding of Gr. Moreover, Gr nanosheets fractured layer by layer rather than simultaneously fractured in the Gr/Al composites with multilayer Gr.