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High‐Throughput Exploration of Structural and Electrochemical Properties of the High‐Entropy Nitride System (Ti–Co–Mo–Ta–W)N

High‐entropy nitrides are largely unexplored materials with high potential to show good mechanical properties, high stability against chemicals, but also promising electrocatalytic properties. The latter is due to their good electrical conductivity compared to (high‐entropy) oxides. The high‐entropy nitride system (Ti–Co–Mo–Ta–W)N is chosen for investigation based on the idea to combine binary and ternary nitrides, which show good water‐splitting activities. Thin‐film materials libraries with continuous composition spreads are deposited using reactive cosputter deposition at 300 and 500 °C. X‐Ray diffraction results show that the films consist of a single‐phase solid solution in NaCl‐type structure. The surface morphology is examined using scanning electron and atomic force microscopy. (Ti–Co–Mo–Ta–W)N films show low resistivity values in the range from 1.72 to 5.2 μΩ cm. Their oxygen evolution reaction activity is measured using a scanning droplet cell, with a maximum current density of 1.78 mA cm−2 at 1700 mV versus reversible hydrogen electrode. The results indicate that stability is a challenge for high‐entropy nitrides, at least for their use as oxygen‐related electrocatalytic reactions.

Open Access
Preparation of Graphite/Ferrite/Resin‐Based Composite High‐Efficiency Wave‐Absorbing Materials by Selective Laser Sintering

Herein, graphite/Fe3O4/resin‐based composite absorbers are prepared by selective laser sintering (SLS) and vacuum impregnation of epoxy resin. The effects of different graphite–Fe3O4 powder compositions on the absorbing and mechanical properties of the composites are investigated. The results show that with the increase of Fe3O4 content, the absorption performance of the composites first increases and then decreases, and the absorption peak gradually moves from high frequency (12–18 GHz) to low frequency (2–8 GHz). The bending strength of composites decreases with the increasing of Fe3O4 content. When the mass ratio of graphite–Fe3O4 is 4:3, the wave absorption performance is the best, the minimum reflection loss is −54.8 dB, the effective absorption bandwidth is 2.8 GHz (8.72–11.52 GHz), and the bending strength is 11 MPa, which is 9 times higher than that of SLS plain billets. This is because the increase of the Fe3O4 content in the hybrid powder increases the number of heterogeneous interfaces, but decreases the number of holes inside the composite, which affects the number of microwave reflections inside the material, resulting in different wave absorption and mechanical properties. The graphite/ferrite/resin matrix composites prepared by SLS technology achieve the synergy of lightweight, high strength, and good wave absorption properties.

Mechanical Property and Failure Mechanism of Metal Rubber/ZA8 Composite Made by Squeeze Casting Process

High‐performance lightweight composites are developed by integrating metal rubber (MR) into a zinc alloy (ZA8) matrix via squeeze casting. MR, comprising 304 stainless steel wires (SSWs) with diameters of 0.15 mm, forms 3D network skeletons with volume fractions of 8.8 vol% (S1), 11.1 vol% (S2), and 13.4 vol% (S3), respectively. The preparation parameters of the composites are optimized, and their microhardness is investigated. Special attention is paid to the ultimate compression and shear performance at 25, 150, and 250 °C. The microstructure and failure analysis are performed via scanning electron microscopy. The results reveal a 48.0% increase in microhardness at composite interfaces relative to ZA8. At 25 °C, S2 possesses an ultimate compressive strength (UCS) of 401.4 MPa, which is 33.7% higher than that of ZA8. At 150 and 250 °C, S3 exhibits UCS values of 180.3 and 74.3 MPa, exceeding those of ZA8 by 61.7% and 110.5%, respectively. Meanwhile, the ultimate shear strength of composites slightly drops below that of the matrix: the corresponding value of S1 specimen (158.4 MPa) at 250 °C is 11.5% below that of ZA8. Therefore, compression and shear failure mechanisms of MR/ZA8 composites are quite intricate, involving SSW separation, necking, and ZA8 fractures.

Study of a Piezoelectric Energy Harvesting Collaborative Strategy Based on the Synergy of Multifrequency Technique and Magnetic Nonlinear Technique

For the purpose of improving the operating bandwidth and output power of piezoelectric vibration energy harvesters (PVEHs) in low‐frequency environment, a novel energy harvesting collaborative strategy based on the synergy of multifrequency technique and magnetic nonlinear technique is proposed. In order to reveal the working mechanism of the proposed strategy and determine the influence law of the key parameters on the output performances of system, theoretical modeling, simulation analysis, and experiments have been carried out. This study proves the feasibility of the two techniques cooperating and complementing each other on the mechanism level, and optimizes the ability of the inner and outer beams to capture energy under the action of the pair of magnets on the structural level. After the optimization of key parameters, the output performance of the proposed PVEH utilizing multifrequency and magnetic structure is higher than the counterpart only based on multifrequency cantilever structure. In an optimal configuration, the fabricated prototype can finally obtain a maximum power of 2.68 mW and a bandwidth of 1.39 Hz under 0.2 g acceleration with 0.03 MΩ load resistance. The proposed piezoelectric energy harvesting collaborative strategy can improve the output performance of piezoelectric vibration energy in practical vibration application environments.

Study on morphology, microstructure and tribo‐corrosion behavior of laser powder bed fusion‐fabricated titanium alloy

The complicated interplay between microstructure and tribo‐corrosion behavior has long been an intriguing problem in the field of advanced materials engineering. This study systematically investigated the effects of different laser energy densities (LED) on the surface morphology, microstructure, and tribo‐corrosion behavior of Ti‐6Al‐4V produced using laser powder bed fusion (LPBF) technology. The surface morphology and microstructure of the specimens were characterized in detail using various characterization techniques such as optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). Additionally, a self‐assembled friction‐corrosion equipment was employed to evaluate the tribo‐corrosion behavior of the samples at different LED settings. The results showed that the LED had a significant effect on the surface morphology, microstructure, and tribo‐corrosion behavior of the Ti‐6Al‐4V. Increasing the LED lead to reduced surface roughness, weakened keyhole and segregation phenomena, more distinct β grain boundaries, and coarser acicular α phase. Moreover, the tribo‐corrosion behavior initially improved and then declined with increasing LED. Furthermore, tribo‐corrosion product and mechanism of the Ti‐6Al‐4V alloy prepared by LPBF were revealed. This study is of great significance for understanding the relationship between the microstructure and tribo‐corrosion behavior of Ti‐6Al‐4V manufactured by LPBF.This article is protected by copyright. All rights reserved.

Towards the development of a shape memory polymer for individualized endovascular therapy of intracranial aneurysms using a 3D‐printing/leaching method

Endovascular treatment of intracranial aneurysms (ICA) aims to occlude the aneurysm space for preventing ICA growth/rupture. Modern endovascular techniques are still limited by lower complete occlusion rates, frequently leading to aneurysm growth, rupture and re‐operation. In this work, we propose shape memory polymer (SMP)‐based embolic devices that could advance the effectiveness of ICA therapy by facilitated individualized ICA occlusion. Specifically, we develop an 3D‐printing/leaching method for the fabrication of 3D‐SMP devices that can be tailored to patient‐specific aneurysm geometries that are obtained from computed tomography angiography. We demonstrate that this method allows the fabrication of highly porous, compressible foams with unique shape memory properties and customizable microstructure. In addition, the SMP foams exhibit great shape recovery, anisotropic mechanical properties, and the capability to occlude in‐vitro models with individualized geometries. Collectively, this study indicates that the proposed method will have the potential to advance the translation of coil‐ and stent‐free embolic devices for individualized treatment of saccular ICAs, targeting complete and long‐term durable aneurysm occlusion.This article is protected by copyright. All rights reserved.