The present study employs Density Functional Theory simulation to investigate the atomic-scale surface reconstruction of NiTi alloy induced by ion implantation. A 2 & times; 2 & times; 2 supercell containing pre-existing defects was constructed to investigate lattice distortion and defect structure stability. Additionally, a symmetrical threelayer NiTi (110) slab model with a vacuum thickness of 15 & Aring; was employed for electronic calculations, including density of states, electron density difference, and work function. The findings suggest that ion implantation results in an increased occurrence of point defects, including both vacancies and doping-related structures. When occupying the vacancy, non-metal N and C atoms induce more pronounced lattice distortions compared to the metal Cr atom. Moreover, by examining orbital hybridization and charge density differences, it was discovered that the implanted ions exhibit a chemisorption behavior when interacting with the Ni/Ti-SV point defect structure.

In this study, three distinct ion species (Cr, C, and N) were implanted into a solution-treated 60NiTi alloy. Ion implantation was found to induce the formation of crystallographic defects and promote the development of nanoscale hard phases within the modified surface layer. Consequently, the near-surface hardness and corrosion resistance of the 60NiTi alloy were significantly enhanced. However, both the untreated and ion-implanted samples exhibited a notable decrease in corrosion resistance under frictional conditions. Furthermore, the transformation of free carbon into graphite-like carbon was observed on the worn surface of the carbon ion-implanted sample following annealing. This structural evolution contributes to enhanced anti-friction performance, reduced wear loss, and improved corrosion resistance in the carbon ion-implanted and post-annealed sample under mechanical friction conditions.

This study presents a novel statistical model for quantitatively estimating the thickness and hardness of Ni60A coating under different parameters, which are then utilized to optimize the cladding process for the Ni60A coating used as a protective layer for guide shoes of coal mining machines. Furthermore, the tribological properties of optimized Ni60A coating were evaluated in comparison with those of substrate under identical conditions. The results confirmed that the proposed model offered a viable mathematical expression for estimating the microhardness of cladding layer, with an R2 value of 98.10% in least square fitting and a predictive deviation of 1.27%. The presence of Ni60A coating effectively suppresses the propagation ability of microcracks, thereby significantly enhancing the wear resistance of guide shoe.

Polyacrylamide (PAM) hydrogels have garnered significant attention due to their unique swelling properties, biocompatibility, and stability, resulting in them being promising candidates for various applications, ranging from drug delivery to tissue engineering. However, traditional PAM hydrogels suffer from low strength and poor toughness, which limits their widespread use. In this study, based on the theory of filler-reinforced composites, we introduced ordered sulfonated polystyrene (SPS) particles into PAM hydrogels using electric field-assisted techniques. The effects of the geometric dimensions and filling concentration of SPS particles on thermal stability, swelling/deswelling behavior, and mechanical properties of composite hydrogels were investigated. When filled with ordered 100 nm SPS particles at a concentration of 2.0 g·L-1, the resulting SPS/PAM composite exhibited improved water retention capacity, as well as a fracture elongation of 316 % and a tensile strength of 23 kPa. These findings in the paper provide valuable insights into the understanding of PAM hydrogels and open up new avenues for the development of advanced hydrogel-based systems with enhanced performance and functionality.

In order to understand the coupling mechanical model of aeroengine ceramic matrix composite, the author proposed a coupling mechanical model and failure study of aeroengine ceramic matrix composite based on genetic algorithm. The author first analyzed that the real-time model of an aircraft engine and the matching accuracy of the engine directly affect the accuracy of aircraft engine fault diagnosis, a least squares support vector regression (AGA LSSVR) method based on adaptive genetic algorithm was proposed to modify the real-time model of an aircraft engine, effectively improving the matching accuracy of the model. Secondly, the impact of parameter selection in least squares support vector machines on model correction was analyzed, and an adaptive genetic algorithm was used to search for the optimal parameters in the parameter selection space. Finally, compare the correction effects of methods such as (BP) neural network, support vector regression machine, AGA LSSVR in airborne models. The results indicate that: The proposed AGA LSSVR has good correction accuracy, which verifies the effectiveness of the correction model.

The Ti6Al4V alloy is extensively utilized in critical marine equipment components due to its low density, high specific strength, and exceptional corrosion resistance in marine environments. However, its low hardness and inadequate wear resistance pose challenges in meeting the urgent demand for prolonged service life of relative motion friction pairs under complex wear and corrosion conditions. As a newly developed lightweight friction pair material, hardened 60NiTi is considered highly desirable owing to its combination of high hardness, high compressive strength, and excellent corrosion resistance. Nevertheless, the tribocorrosion properties of 60NiTi compared to those of Ti6Al4V are not yet fully comprehended. The present study conducted a series of sliding wear tests using a ball-on-plate configuration in artificial seawater environment to compare the response of 60NiTi with Ti6Al4V. In order to gain a comprehensive understanding of the factors contributing to the divergence in tribocorrosion response between both materials, further analysis was performed on the wear track subsurface and transfer film using focused ion beam-scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy respectively. The 60NiTi demonstrates significantly enhanced wear resistance in artificial seawater compared to Ti6Al4V, attributed to its combination of high hardness and excellent corrosion resistance. However, Ti6Al4V exhibits a lower friction coefficient (∼0.30) than 60NiTi (∼0.45) due to the formation of a stable transfer film primarily composed of SiO2, Al(OH)3, and Al2O3.

The epoxy nanocomposites reinforced by MoS2 nanosheets and aligned multi-walled carbon nanotubes (MWCNTs) were fabricated by DC electric field inducement. The epoxy nanocomposites achieved improvement in the tribological properties with the addition of randomly dispersed MoS2 and MWCNTs compared to the pure epoxy. Furthermore, the epoxy nanocomposites exhibit anisotropic tribological and mechanical properties when the MWCNTs are aligned in the composites. The tribological properties of epoxy nanocomposites containing 1 wt% MoS2 and aligned 1.2 wt% MWCNTs achieved the maximum improvement when the sliding direction is perpendicular to the axial direction of MWCNTs. Compared to random MoS2 nanosheets and random MWCNTs reinforced epoxy nanocomposites, the friction coefficient and wear rate of random MoS2 and aligned MWCNTs reinforced epoxy nanocomposites decreased by 11.3 and 66.7% under a load of 5 N, respectively. The increased thermal conductivity and mechanical properties, higher surface content of nanoparticles, as well as unique alignment mode of MWCNTs are considered to be the main reasons for the improvement of tribological properties of epoxy nanocomposites.

The piezoelectric drop-on-demand material jetting technique is widely used in additive manufacturing due to its cost-effectiveness, high accuracy, and the ability to efficiently print a variety of materials. However, there is a conflict between the requirements related to printing productivity and printing quality, which is solved by the droplet volume modulation method. In recent years, a variety of inkjet technologies have been developed to control the droplet volume, but control was achieved only over a small range, with the ratio between the maximum and minimum volume approx. 10. In this paper, the advance droplet phenomenon was shown and its formation mechanism was determined through experiments and simulations. Based on the formation mechanism and the response characteristic of the piezoelectric printhead to the basic waveform, a droplet volume modulation method was proposed. The method was based on multi-waveform superposition and the aim was to achieve a larger volume range of droplet ejection. The experimental results have shown that the newly designed waveform results in a controllable and stable single droplet ejection in a volume range from 0.61 pl to 83.7 pl, with the ratio between the maximum and minimum volume more than 130, an order of magnitude above current levels. Hence, this work provides a new perspective for improving both the printing quality and printing productivity of additive manufacturing.

The voltage outputs of flexible piezoelectric films after bending deformation have always been limited by two factors, including the incompatible polarization direction with bending strain and the interfacial fatigue failure between the piezoelectric films and the electrode layers, largely hindering the applications in wearable electronics. Herein, we demonstrate a new piezoelectric film design, where 3D-architectured microelectrodes are fabricated inside a piezoelectric film by electrowetting-assisted printing of conductive nano-ink into the pre-formed meshed microchannels in the piezoelectric film. The 3D architectures increase the piezoelectric output of a typical P(VDF-TrFE) film by more than 7 fold compared with the conventional planar design at the same bending radius, and, more importantly, decrease the output attenuation down to only 5.3% after 10 000 bending cycles, less than one third of that for the conventional design. The dependence of piezoelectric outputs on feature sizes of 3D microelectrodes was investigated numerically and experimentally, providing a route for optimizing the 3D architecture design. Different composite piezoelectric films with internal 3D-architectured microelectrodes were fabricated, exhibiting improved piezoelectric outputs under bending deformations, demonstrating that our printing methods could have broad applications in various fields. The fabricated piezoelectric films, worn on human fingers, are used for remotely controlling the robot hand gestures by human-machine interaction; furthermore, the fabricated piezoelectric patches are used to successfully sense the pressure distribution by integrating with spacer arrays to convert the pressing movement into bending deformation, demonstrating the enormous potential of our piezoelectric films in practical applications.

In order to improve the lubrication performance of the WS 2 -based coatings at elevated temperature, the mechanisms of enhancing the tribological performance of WSNb coatings at elevated temperatures are investigated. The WSNb coating doped with 11.9 at.% Nb exhibited excellent anti-friction and wear resistance, achieved a low coefficient of friction of 0.02 at 400 °C, and its wear resistance was much better than that of WS 2 -based coatings. The Nb metal and its sulfide in the coating are more sensitive to oxygen than WS 2 at 400 °C, which reduces the oxygen concentration between the friction pairs and protects the WS 2 lubricating phase from being oxided. In addition, Nb enhances the hardness and Young's modulus of the coatings through the solid solution strengthening effect, generating a more continuous and stable lubricating film during the silding process. First-principles calculation results demonstrated that the Nb spontaneously forms Nb-S bonds with S atoms in the coating. The molecular details of the Nb-S formation have been investigated in depth.

The piezoelectric inkjet (PIJ) printing technique, as a typical drop-on-demand (DOD) inkjet process, employs the electric potential for activating the mechanical vibration of a lead zirconium titanate (PZT) membrane. As a result, the constant flow of the fluidic ink within the solid channel is attained, resulting in the formation of a droplet in the nozzle. This droplet will be subsequently deposited on a substrate, which renders the PIJ method one of the most indispensable tools for various applications in MEMS, cell printing, LCD fabrication, etc. However, by considering a specific driving waveform, an air bubble will be generated and trapped within the solid channel after the ink droplet is ejected from the nozzle, which would inevitably affect the subsequent printing process. Additionally, there are scarce reports in the literature that have dealt with this issue in depth. Along these lines, in this work, a conservative level set method in conjunction with the inverse piezoelectric effect and the fluid–structure interaction is proposed for analyzing the PIJ printing process. On top of that, benchmark effectiveness against the experimental tests is introduced, in which an air bubble can be observed to be generated and further be trapped within the nozzle channel. The evolution of air bubble formation and trapping process was then visually analyzed in depth by considering the ink–solid–air interaction in the form of numerical investigation, which has never been reported in the literature according to our best knowledge. In addition, a variety of both numerical and experimental results have been provided to illustrate the coalescence of the trapped air bubbles from smaller bubbles to a large bubble and to demonstrate how exactly the trapped air bubbles affect the print quality. Furthermore, the influence of the driving waveform on the evolution of the trapped air bubble was explored, which could be of great advantage for the better control of the printing process for various PIJ printheads.

Ti6Al4V alloy has good corrosion resistance due to the formation of the passive oxide films on the surface of Ti6Al4V alloy. However, Ti6Al4V alloy has poor tribocorrosion resistance in the seawater environment. Herein the present work, plasma electrolytic oxidation (PEO) with the electrolyte of glycerol and sodium borate is used to generate PEO coatings on the surface of Ti6Al4V alloy to improve its tribocorrosion properties. The microstructure and tribocorrosion properties of PEO coatings are investigated by using scanning electron microscopy, X‐ray diffraction, and tribometer, respectively. The growth kinetics and the tribocorrosion mechanisms of PEO coatings are discussed in detail. It is shown in the results that PEO coatings deposited on the surface of Ti6Al4V alloy are composed of rutile and anatase phases. The surface hardness and thickness of PEO coatings are enhanced with the increase of the voltage and time. The wear rate of Ti6Al4V alloy with PEO coatings is significantly reduced in artificial seawater.

Incorporating high thermal conductivity fillers into the matrix material and optimizing their distribution offers a targeted approach to controlling heat flow conduction. However, the design of composite microstructure, particularly the precise orientation of fillers in the micro-nano domain, remains a formidable challenge to date. Here, we report a novel method for constructing directional/localized thermal conduction pathways based on silicon carbide whiskers (SiCWs) in the polyacrylamide (PAM) gel matrix using micro-structured electrodes. SiCWs are one-dimensional nanomaterials with ultra-high thermal conductivity, strength, and hardness. The outstanding properties of SiCWs can be maximized through ordered orientation. Under the conditions of 18 V voltage and 5 MHz frequency, SiCWs can achieve complete orientation in only about 3 s. In addition, the prepared SiCWs/PAM composite exhibits interesting properties, including enhanced thermal conductivity and localized conduction of heat flow. When the SiCWs concentration is 0.5 g & BULL;L-1, the thermal conductivity of SiCWs/PAM composite is about 0.7 W & BULL;m- 1 & BULL;K-1, which is 0.3 W & BULL;m- 1 & BULL;K-1 higher than that of PAM gel. This work achieved structural modulation of the thermal conductivity by constructing a specific spatial distribution of SiCWs units in the micro-nanoscale domain. The resulting SiCWs/PAM composite has unique localized heat conduction properties and is expected to become a new generation of composites with better characteristics and functions in thermal transmission and thermal management.

Metal micropatterns play critical roles in flexible electronics. However, the lack of versatile strategies for micropatterning of diverse metal materials on various thin, flexible or stretchable substrates has limited the rapid development of flexible electronics. Here, a metal micropatterning method by triboelectric spark discharge under atmospheric environment is developed, where a triboelectric nanogenerator (TENG) is employed to precisely and safely control the voltage, current, and frequency of the spark discharges. Micropatterns of metal films like gold, silver, copper, aluminum and platinum are successfully fabricated on substrates of polyimide, polyethylene terephthalate, polyvinyl chloride, polydimethylsiloxane, paper or latex, even on ultrathin substrates (5 μm thick) without damage, where the feature sizes of metal patterns are controllable from 20 μm to 1 mm. Experimental insights into the triboelectric spark discharge behaviors and the pattern feature sizes control are discussed. A straightforward fabrication of metal patterns on the balloon surface or human skin through “handwriting” by a pencil as discharge electrode is realized. Besides metals, extended processibility of conductive materials like carbon nanotubes, graphene, MXene, graphite, carbon fibers, and conductive polymers are also demonstrated. This work proves the possibility of microfabrication by TENG, which is of simplicity and attractiveness for flexible electronics.

Hardened 58Ni39Ti3Hf possesses a superior resistance to quenching cracking and spall-type surface fatigue as compared to 60NiTi, which makes it considered as an alternative for this binary intermetallic. Nonetheless, it is still a lack of deep understanding of how the microstructure, grain distribution, and surface properties of 58Ni39Ti3Hf differ from those of 60NiTi. In this work, combined analysis methods of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM) were conducted to systematically characterize the phase composition, microstructure, and grain distribution. Nanoindentation test was carried out to study the mechanical properties of surface. The growth of passive film in seawater was analyzed using X-ray photoelectron spectroscopy (XPS). Finally, electrochemical impedance spectroscopy (EIS) measurement before, during, and after the tribocorrosion test was performed to evaluate the corrosion resistance of these two alloys when served in different conditions. 58Ni39Ti3Hf was found to have better corrosion and mechanical properties than 60NiTi within the range of this experiment, and the involved mechanism was discussed in detail.

60NiTi alloy is highly promising for aerospace bearings and mechanisms. Shock load that is inevitably generated during launching process brings about an quick loading process and transient load duration, and may further results in an unnoticed but detrimental creep deformation. On this account, the nanoindentation creep behavior of solution-treated 60NiTi alloy at room temperature and the corresponding influencing mechanism were studied. The results show that creep displacement was dominated by strain rate at the very beginning of holding stage. Strain rate and flow stress at the very beginning of holding stage were increased with an increased loading rate but declined with increasing holding load or with simultaneously increasing loading rate and holding load. The underlying mechanisms were provided as nucleation and absorption of geometrically necessary dislocations (GNDs) associated with strain gradient plasticity theory rather than the model based on the consumption of creep deformation at loading stage.

随着中国电网容量的不断增大,用于输配电的开关柜数量也大大增加,这就对开关柜小型化和安全性能提出了更高的要求,而小型化的趋势使温升问题日益严重,加大了对安全性保障的难度.文中针对中压大电流开关柜的温升问题在SolidWorks和Ansys Workbench平台上进行了建模仿真研究.首先,基于电磁场理论,通过基于表面深度划分网格的方式进行了开关柜的涡流场仿真,分析了各个部分的损耗,研究了涡流损耗对总损耗的影响.随后运用单向耦合的方法进行了开关柜温度场的仿真,研究表明真空灭弧室触头中触头片部分是温升最严重的部分.最后结合涡流场与温度场仿真结果,进一步对开关柜在热源和散热两方面进行比较研究,结果表明将壳体材料改成不锈钢、触头片材料改为无氧铜(从发热的角度)、触头结构改为螺旋槽形橫磁触头、开关柜改善通风散热条件对开关柜的温升的降低具有明显的作用,仿真结果得到了实验验证.

In this work, WSN coatings were prepared with a 99% WS2 target by RF magnetron sputtering at the N-2 atmosphere, and their lubrication properties and wear resistance were tested at elevated temperatures. The mechanical properties of WSN coatings are studied using nanoindentation. In particular, the phase composition and the chemical composition of the coatings are analyzed in detail to study its lubrication mechanism by XRD, TEM, XPS, etc. Ultra-low CoF of 0.008, 0.009 and 0.006 were obtained at elevated temperatures of 200 degrees C, 400 degrees C and 500 degrees C respectively. WS2 nanocrystals are uniformly distributed in the coating and form a nanocomposite structure with the amorphous phase. Amorphous WNx formed by doping with N element plays a role of dispersion strengthening in the coating, which brings high mechanical properties and wear resistance to the WSN coating. The WS2 nanocrystals in the WSN coating are broken and reorganized in the friction pair, forming a stable lubricating film with the WS2 (002) crystal plane dominant orientation. At 500 degrees C, the WO3 crystal produced by the oxidation of the coating acts as a lubricating phase, forming a transfer film with extremely low shear strength between the friction pairs. This work proposes the improvement mechanism of elevatedtemperature tribological performance of hardened WS2 coating for the first time. In addition, first-principles methods are used to study the enhancement mechanism of N atoms in the WSN model. The formation of WNx is attributed to the chemical bonding between W and N atoms spontaneously. The molecular details of WNx strengthening phase formation have been studied in depth.

Axial magnetic field (AMF) contacts are widely used in vacuum interrupters. In this paper, the magnetic field distribution of 1/2 coil-type contact, 2/3 coil-type contact, 1/3 coil-type contact and cup-type contact are calculated and analyzed. It is found that the AMF strength of coil-type contacts is much greater than that of cup-type contact. The order of residual AMF from weak to strong is: cup-type contact, 1/3 coil-type contact, 1/2 coil-type contact and 2/3 coil-type contact. The order of phase shift from small to large is: 1/3 coil-type contact, 2/3 coil-type contact, 1/2 coil-type contact and cup-type contact. Triggered vacuum arc experiments about these contacts are carried out and the vacuum arc evolution process is recorded by high-speed camera. It is found that, under the same current, the arc constriction of the cup-type contact is the most serious and the arc of 2/3 coil-type contact has almost no constriction.