Journal of Materials Science & Technology最新文献

The development of intelligent electronic power systems necessitates advanced flexible pressure sensors. Despite improved compressibility through surface micro-structures or bulk pores, conventional capacitive pressure sensors face limitations due to their low dielectric constant and poor temperature tolerance of most elastomers. Herein, we constructed oriented polyimide-based aerogels with mechanical robustness and notable changes in dielectric constant under compression. The enhancement is attributed to the doping of surface-modified dielectric nanoparticles and graphene oxide sheets, which interact with polymer molecular chains. The resulting aerogels, with their excellent temperature resistance, were used to assemble high-performance capacitive pressure sensors. The sensor exhibits a maximum sensitivity of 1.41 kPa⁻¹ over a wide working range of 0-200 kPa. Meanwhile, the sensor can operate in environments up to 150°C during 2000 compression/release cycles. Furthermore, the aerogel-based sensor demonstrates proximity sensing capabilities, showing great potential for applications in non-contact sensing and extreme environment detection.

Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic (EM) wave absorption materials. In this study, an ultralight and rigid poly(p-phenylene benzobisoxazole) nanofiber (PNF) based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy (CoNi) nanoparticles and carbon nanotubes (CNTs) as magnetic and conductive fillers, respectively. A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method, and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel. CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles. The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss, magnetic loss, multiple reflection, scattering, and absorption. When its thickness was 4 mm, the CoNi/CNT/PNF aerogel showed a minimal reflection loss of −44.7 dB (at 6.88 GHz), and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band (12.32 GHz, from 5.68 GHz to 18 GHz). In addition, the rigid aerogel exhibited an ultralow density (0.107 g/cm³), excellent thermal insulation, and flame retardancy, demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.

The fabrication of Invar/MnCu functionally graded material (FGM) through directed energy deposition (DED) can satisfy the demands for precision devices in aerospace, providing lightweight properties and integrating thermal stability and vibration damping capabilities. However, basic research on Invar/MnCu FGM is still lacking, hindering its potential applications. To address this gap, this study was conducted using mixed powders and consistent process parameters to print experiments for Invar/MnCu FGM and homogeneous samples. Phases, microstructures, compositions, and thermal expansion properties were thoroughly examined. Three types of defects were detected in the Invar/MnCu FGM sample: unmelted Invar 36 powders, cracks, and pores. The mechanism of unmelted powders was deeply discussed, attributing it to material properties influencing laser absorptivity, the required time for melting powder, and effects on solidus temperature. The mechanism of cracks was also discussed, attributing it to the γ-Fe dendritic structure causing low melting point metal to form an intergranular liquid film, harmful secondary phases mismatched with the terminal alloy, and obvious tensile stresses during the DED process. Additionally, an effective strategy was proposed to reduce defects in Invar/MnCu FGM. After optimization, the specimens exhibited excellent tensile properties, with a yield strength of 262 ± 5 MPa, an ultimate tensile strength of 316 ± 7 MPa, and an elongation of 3% ± 1%. This research provides valuable references and insights for subsequent work, offering robust support for better understanding and designing other FGM.

Tetravalent tin (Sn⁴⁺)-based inorganic perovskite semiconductors like Cs₂SnI₆ are expected to replace lead-based perovskite counterparts due to advantages such as structural stability and environmental friendliness. In this paper, we reported the dopant compensation effect in the component-dependent self-doped (111)-oriented Cs₂SnI₆ thin films grown with pulsed laser deposition (PLD) at room temperature. The films were grown on (100)-SrTiO₃ (STO) substrates at room temperature by PLD. Hall results of the Cs₂SnI₆ films with different components realizing by controlling the ratio of SnI₄/CsI in the targets demonstrate a clear change of conductivity type from N-type to P-type, while the carrier concentration decreases from 10¹⁸ to 10¹³ and accordingly the film resistivity increases significantly from 3.8 to 2506 Ω cm. The defect-related optical fingerprints of Cs₂SnI₆ films were also investigated with temperature-dependent photoluminescence spectroscopy. At low temperatures of 10 K, the Cs₂SnI₆ films exhibit donor-bound (D⁰X) and donor-acceptor pair (DAP) emission, respectively, due to the self-doping effect. These results indicate that controlling the composition of the PLD target is a powerful way to tune the electrical properties of Cs₂SnI₆ films for possible applications in solar cells or X-ray detectors.

Solar water splitting is an emerging technology for producing clean and renewable hydrogen fuel from sunlight and water. Among various photoelectrode materials, bismuth vanadate (BiVO₄) has attracted considerable attention due to its visible light absorption, favorable band edge positions, good chemical stability, and low cost. However, the solar water splitting efficiency of BiVO₄ photoanodes is still far from satisfactory, mainly because of the low charge carrier mobility, high recombination rate, and slow water oxidation kinetics. In this review, we summarize the recent progress in the synthesis, modification, and application of BiVO₄-based photoelectrodes for photoelectrochemical (PEC) water splitting. The working principle of PEC water splitting and the fundamental properties of BiVO₄ are introduced. Then, the synthesis methods of BiVO₄ films are reviewed, and the strategies to enhance the PEC properties of BiVO₄ are critically discussed. Furthermore, the applications of BiVO₄-based photoelectrodes in different scenarios are highlighted. Finally, the summary and outlook for the future development of BiVO₄-based photoelectrodes for PEC water splitting are presented.

Even though vacuum induction melting (VIM) is widely employed in the industrial production of bulk metallic glasses (BMGs), the effect and mechanism of the interfacial reaction between the melt and the oxide ceramic crucible on BMG formations are not yet fully understood. Here, the influences and mechanisms of the interfacial reaction on a Zr-based BMG (Vit 105) subjected to various melting temperatures and holding times are revealed by employing experiments and theoretical calculations. We find that the degree of interfacial reaction is intriguingly correlated with the process parameters during VIM processing, leading to an increase in the oxygen content of the alloy and the reaction layer thickness. Besides, the increase of oxygen content also induces variations in the ordering and shear transformation zone (STZ) size of the BMGs, thus resulting in the precipitation of a nanoscale fcc phase and affecting the mechanical properties and reliability under deformation of the alloy. Furthermore, thermodynamic and kinetic parameters involved in the interfacial reaction, such as the molar Gibbs free energy of each element, the apparent activation energy, etc., are obtained, providing a comprehensive understanding of the transport processes at play. Our findings provide new insights into the preparation of BMGs by VIM and may be expanded to other melting techniques to accelerate the commercial application of metallic glasses.

To present an advanced device scheme of high-performance optoelectronic synapses, herein, we demonstrated the electrically- and/or optically-drivable multifaceted synaptic capabilities on the 2D semiconductor channel-based ferroelectric field-effect transistor (FeFET) architecture. The device was fabricated in the form of the MoS₂/PZT FeFET, and its synaptic weights were effectively controlled by dual stimuli (i.e., both electrical and optical pulses simultaneously) as well as single stimuli (i.e., either electrical or optical pulses alone). This could be attributed to the electrical pulse-tunable strong ferroelectric polarization in PbZr_xTi_1−xO₃ (PZT) as well as the polarization field-enhanced persistent photoconductivity effect in MoS₂. Additionally, it was confirmed that the proposed device possesses substantial activity, achieving approximately 95% pattern recognition accuracy. The results substantiate the great potential of the 2D semiconductor channel-based FeFET device as a high-performance optoelectronic synaptic platform, marking a pivotal stride towards the realization of advanced neuromorphic computing systems.

Boundary engineering has proven effective in enhancing the thermoelectric performance of materials. SnSe, known for its low thermal conductivity, has garnered significant interest; however, its application is hindered by poor electrical conductivity. Herein, the Ag₈GeSe₆ is introduced into the p-type polycrystalline SnSe matrix to optimize the thermoelectric performance, and the in-situ Ag₂Se precipitates are formed in grain boundaries, which play dual roles, acting as an electron attraction center for improving hole concentration and a phonon scattering center for reducing lattice thermal conductivity. It effectively decouples the thermal and electrical transport properties to optimize the thermoelectric performance. Importantly, the amount of Ag₂Se can be controlled by adjusting the amount of Ag₈GeSe₆ added to the SnSe matrix. The introduction of Ag₈GeSe₆ enhances electrical conductivity due to the increased hole carrier caused by the introduced Ag⁺ and the formed electron attraction center (in-situ Ag₂Se precipitates). Based on the DFT calculations, the band gap of the Ag₈GeSe₆-doped samples is considerably decreased, facilitating carrier transport. As a result, the electrical transport properties increase to 808 μW m⁻¹ K⁻² at 823 K for SnSe + 0.5 wt% Ag₈GeSe₆. In addition, in-situ Ag₂Se precipitates in grain boundaries strongly enhance phonon scattering, causing a decrease in lattice thermal conductivity. Furthermore, the presence of defects contributes to a reduction in lattice thermal conductivity. Specifically, the thermal conductivity of SnSe + 1.0 wt% Ag₈GeSe₆ decreases to 0.29 W m⁻¹ K⁻¹ at 823 K. Consequently, SnSe + 0.5 wt% Ag₈GeSe₆ obtains a high ZT value of 1.7 at 823 K and maintains a high average ZT value of 0.57 over the temperature range of 323−773 K. Additionally, the mechanical properties of Ag₈GeSe₆-doped also show an improvement. These advancements can be applied to energy supply applications during deep space exploration.

To improve the thermal stability of nanocrystalline (NC) metals, their interface structure can be modified by applying amorphous intergranular layers. However, traditional amorphous metallic intergranular layers are rarely formed in most pure metals or alloys. In this study, we demonstrate that amorphous oxide intergranular layers can greatly improve the thermal stability of NC metals by tailoring the grain boundaries (GBs) of NC metals. Using a Au–ZrO₂ model system, ultra-fine Au nanoparticles (∼ 3 nm) with exceptional thermal stability at temperatures up to 600°C were formed after introducing amorphous ZrO₂ intergranular layers at the GBs of NC Au. Quantitative thermodynamic model calculations revealed that the exceptional thermal stability of the Au nanoparticles originated fundamentally from the formation of low-energy Au|ZrO₂ interfaces. The kinetic stabilization was further discussed, showing that the Ostwald ripening of Au nanoparticles was suppressed due to the presence of amorphous ZrO₂ intergranular. This study sheds light on new strategies for enhancing the thermal stability of NC metals by utilizing amorphous oxide intergranular layers, paving the way for the achievement of ultra-stable NC metals through interface modification.

Achieving intrinsic strengthening of boron nitride nanosheets (BNNSs) in Ti matrix composites was still an unsettled issue due to its severe and uncontrollable interface reaction. In the present study, high-performance BNNSs/Ti composites were fabricated by using the warm compaction (WC) technique and rapid heat treatment (HT) strategy on the basis of interfacial nano-TiB_w design. The intrinsic structure of BNNSs was well-retained and nano-TiB_w on partially reacted BNNSs led to a brilliant interface bonding and BNNSs intrinsic strengthening. Tensile tests revealed that 0.1 wt.%BNNSs/Ti composites exhibited the tensile strength (UTS) of 876 MPa (61% higher than pure Ti) and the fracture elongation of 22.6%, demonstrating the well-balanced property. By employing the in-situ TEM experiment, we solve an existing debate, uncovering the synergistic toughening effect from BNNSs and interfacial nano-TiB_w which effectively inhibited the micro-cracks propagation on BNNSs and heterogeneous interface. This work paves a new way for developing high-performance BNNSs/Ti composites by reaction interface manipulation and underscores the importance of maintaining BNNSs intrinsic structure in the Ti matrix.