Abstract ：

Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head. The thermal efficiency of FRAM, which depends only on friction to generate heat, is low, and the thermalaccumulation effect of the deposition process must be addressed. An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling (PC-FRAM) is devised in this study, and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head. Additionally, 2195-T87 Al-Li alloy is used as the feed material, and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated. The results show that water cooling significantly improves heat accumulation during the deposition process. The cooling rate increases by 11.7 times, and the high-temperature residence time decreases by more than 50 %. The grain size of the PC-FRAM sample is the smallest, i.e., 3.77 E1.03 }m, its dislocation density is the highest, and the number density of precipitates is the highest, the size of precipitates is the smallest, which shows the best precipitation-strengthening effect. The hardness test results are consistent with the precipitation distribution. The ultimate tensile strength, yield strength and elongation of the PC-FRAM samples are the highest (351 E15.6 MPa, 251.3 E 15.8 MPa and 16.25 % E1.25 %, respectively) among the samples investigated. The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples. The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science &

Keyword ：

Microstructure Friction rolling additive manufacturing Plasma preheating Instant cooling Heat accumulation Al-Li alloy

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Abstract ：

Traditional semiconductor used as channel materials in driving transistors suffer from significant performance degradation as the semiconductor thickness is reduced. The two-dimensional (2D) materials with smooth, dangling-bond-free surfaces, represented by graphene, can be alternatives. Graphene boasts several advantages, including structural stability, ultra-thin thickness, near-total transparency, exceptional flexibility, and high mobility. Therefore, graphene field-effect transistors (GFETs) in the paper are used to drive Micro-light-emitting diodes (Micro-LEDs), key elements in next-generation advanced displays due to their high resolution, high brightness, high contrast, etc. Importantly, this study addresses the two major bottlenecks i.e. Micro-LEDs' mass transfer and graphene transfer. That is, monolithically integrated devices of Micro-LED and its driver GFET are designed and fabricated, bypassing the issue of traditional Micro-LEDs' mass transfer. For the first time, transfer-free method by plasma-enhanced chemical vapor deposition (PECVD) is used to grow graphene directly on GaN Micro-LED samples and prepared graphene transistors. This approach avoids doping and damage to the graphene during the transfer process, significantly shortens the growth time, and improves the fabrication efficiency. The devices possess broad applications potential and compatibility with semiconductor planar processes. This study paves the way for the transfer-free growth of graphene and the integration of Micro-LEDs with 2D materials transistors.

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Tungsten (W) is considered the prime candidate for plasma-facing materials (PFMs) in future fusion devices. However, the surface blistering induced by hydrogen isotope irradiation can significantly alter the surface morphology of W, thereby severely impacting its service lifetime. Recent studies have shown that high entropy alloys (HEAs) exhibit excellent radiation resistance. This work focuses on investigating the H+ irradiation effects on low-activity W-based HEAs. A composite target was prepared using a splicing method, and WTaZrCrVTiAl HEA films with an amorphous structure were deposited by magnetron sputtering. Comparative experiments on the HEA film and pure W film under H+ irradiation conditions revealed that the blister dose threshold of the HEA film far exceeds that of the pure W film, which implies that they have more excellent resistance to H+ irradiation.

Keyword ：

Nuclear materials Metallic composites Radiation damage

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Abstract ：

Precision polishing of small modulus gears is a difficult task due to the complexity of their geometry. Electrolytic plasma polishing technology as a green and efficient processing method, it can effectively decrease the friction between parts and improve the service life. However, considering the uneven distribution of gas layers on the surface of workpieces in electrolytic plasma polishing, which affects the precision of workpiece shapes after polishing, this study proposed the use of ultrasonic vibrations to generate pressure waves to improve the fluid characteristics. Comparative experiments on small modulus gear electrolytic plasma polishing with and without ultrasonic vibration were conducted. A high-speed camera was utilized to monitor the distribution of gas layers around the workpiece during the polishing process in real-time. The optical measurement methods were used to evaluate the gear precision. The results indicate that ultrasonic assistance is beneficial in improving the uniformity of the gas layers surrounding the workpiece, achieving higher gear precision, and obtaining a lower surface roughness after polishing. Through orthogonal experiments, this study analyzed the effects of various process parameters on the surface roughness of gear profiles and the uniformity of material removal after polishing. These parameters included power voltage, polishing time, workpiece immersion depth, ultrasonic frequency, and workpiece posture angle. An optimal combination of process parameters was identified. The results show that the best surface roughness and gear precision were achieved with a power voltage of 300 V, a polishing time of 4 min, a workpiece immersion depth of about 10 mm, an ultrasonic frequency of 40 kHz, and a workpiece tilt angle of 45 degrees.

Keyword ：

Surface roughness Gear precision Small modulus gears polishing Ultrasonic assisted electrolytic plasma Parameter optimization

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This study introduces a novel vector gas regulated plasma arc welding technique incorporating four auxiliary gas channels integrated within the water-cooled nozzle. Four different forms plasma arcs were generated by introducing four, three, two or none gas streams through the auxiliary channels respectively. Experimental and simulation methods were used to compare arc pressure, arc temperature characteristics for different arc types respectively. It was found that auxiliary gases can adjust the arc pressure and temperature field distribution on workpiece. In comparison to conventional plasma arc welding, the novel PAW can enhance the plasma arc penetration and adjust the thermal and force distribution. It offers increased welding efficiency and adaptability to diverse conditions, has a significant application potential in plasma arc welding technology.

Keyword ：

Arc pressure Temperature field Auxiliary gas Plasma arc welding

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Abstract ：

Molten calcium-magnesium-aluminosilicate (CMAS) poses a considerable threat to the environmental barrier coatings (EBCs) service life. Here, we have prepared ytterbium monosilicate (YbMS) and ytterbium disilicate (YbDS) coatings using air plasma spraying (APS), and comprehensively investigated their high -temperature response to two CMAS relevant to real sediments within gas turbine and Beijing sand -dust, which are defined as CaO-rich CMAS and CaO-lean CMAS respectively. In the CaO-rich CMAS case, either YbMS or YbDS coating exhibits a vigorous reaction and rapid precipitation of apatite phase, constructing a dense reaction layer and inhibiting the molten CMAS infiltration. Note that the YbMS coating always possesses a smaller infiltration depth than YbDS coating because of the synergistic effect of its higher reactivity and more stable crystal structure. In comparison, the molten CaO-lean CMAS infiltrates along the grain boundaries of both coatings without any barrier, only some re -precipitated YbDS grains exist at the CMAS/coating interface. This phenomenon is closely related to the relatively high Yb3+ solubility due to its lower CaO content relative to the CaO-rich CMAS. These finds in this work are expected to provide a better understanding for the design of next -generation EBCs material and proposal of effective methods to mitigate the molten CMAS attack.

Keyword ：

Ytterbium monosilicate Ytterbium disilicate Calcium-magnesium-aluminosilicate (CMAS) Environmental barrier coatings (EBCs)

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Abstract ：

Variable polarity plasma arc welding (VPPAW) is a highly efficient method for joining aluminum and magnesium alloys, primarily because of the automatic removal of oxide layers through cathode spots. Additionally, the high energy density generated by a variable polarity plasma arc creates a keyhole within the weld pool, enabling single-pass welding of medium-thick plates with minimal deformation and residual stress. Understanding the keyhole behaviors, arc physics, and control methodologies are essential to optimize and improve the stability of this welding process. This survey paper offers an overview of the development of the VPPAW process and its recent developments of detecting, modeling, and controlling. It shows that the potential applications of hybrid processes derived from VPPAW have expanded. Advanced process detection techniques, particularly the utilization of X-ray-based vision systems for the in-situ observation of molten metal flow, have significantly contributed to the understanding of VPPAW. Moreover, studies investigating VPPAW across different welding positions have enhanced the adaptability of this welding method. Accurate numerical models and intelligent deep learning methodologies have been crucial in unveiling the underlying mechanisms and facilitating the predictive analysis of welding quality.

Keyword ：

Modeling Arc physics Control Variable polarity plasma arc welding Detection Keyhole

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Abstract ：

Plastic products offer remarkable convenience for modern life. However, growing concerns are emerging regarding the potential health hazards posed by nanoplastics, which formed as plastics break down. Currently, the biological effects and mechanisms induced by nanoplastics are largely underexplored. In this study, we report that polystyrene nanoplastics can enter the bloodstream and enhance thrombus formation. Our findings show that polystyrene nanoplastics adsorb plasma proteins, particularly coagulation factor XII and plasminogen activator inhibitor-1, play a key role in this process, as demonstrated by proteomics, bioinformatic analyses, and molecular dynamics simulations. The adsorption of these proteins by nanoplastics is an essential factor in thrombosis enhancement. This newly uncovered pathway of protein adsorption leading to enhanced thrombosis provides new insights into the biological effects of nanoplastics, which may inform future safety and environmental risk assessment of plastics. © 2024 Elsevier B.V.

Keyword ：

Nanoclay

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Abstract ：

变极性等离子弧(Variable Polarity Plasma Arc,VPPA)焊是一种高效的铝合金和镁合金焊接方法,其主要优势在于等离子电弧具有高能量密度,可以在焊接时穿透熔池形成小孔,大幅度降低焊接变形和残余应力,提高焊接质量.了解熔池小孔行为、电弧物理特性和控制方法对于优化和提高焊接过程的稳定性至关重要.本文综述了VPPA焊接技术发展的最新情况,对VPPA焊接过程信息的检测研究为深刻认识焊接稳定性机理提供了有力保障,尤其是利用X射线成像系统观测熔融金属流动的研究,对提升VPPA穿孔熔池物理本质的认识做出了重要贡献.此外,针对不同位置VPPA焊接的研究增加了这一焊接工艺的灵活性,由VPPA焊接衍生的多种拓展工艺拓宽了该焊接方法的适用范围.VPPA穿孔焊接技术以其焊接变形小、焊后无缺陷、单面焊接双面一次成形等优势,成为航空航天领域铝合金中厚板材焊接制造的优选工艺.

Keyword ：

复合焊接 电弧物理 熔池检测 稳定性控制 变极性等离子弧焊

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传统电弧由于热输入高、熔覆率低,无法直接应用于电弧熔丝增材制造(wire and arc additive manufacturing,WAAM)技术.该文提出极性变换自适应分流交替电弧WAAM工艺方法,在钨电极,工件和丝材间形成交替电弧.根据EN/EP电流转换时自适应分流并主动诱导交替电弧形成.该新型热源能满足以丝材阳极-钨电极阴极的EN电弧熔化丝材;以钨电极阳极-工件阴极的EP电弧清理工件,并通过适当的调节实现电弧热质力传输的受控解耦.验证了该新型热源的适用性,并对比分析了焊接速度和丝材高度下对电弧行为及熔滴过渡的影响.结果表明,当焊接速度为 5.7 mm/s和丝材高度为 8 mm时,沉积层形貌较好且熔滴过渡规律;与传统变极性等离子电弧(variable polarity plasma arc,VPPA)熔丝增材制造技术相比,其自适应分流交替电弧显著提高了丝材的沉积效率且降低了母材热输入,较好的兼顾了增材质量与增材效率.

Keyword ：

交替电弧 电弧行为 熔滴过渡 焊缝成形 电弧熔丝增材制造

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