High performance metal powders are essential feedstocks for advanced manufacturing technologies such as additive manufacturing and metal injection molding. Their particle size strongly affect powder spreading, packing density, forming stability, and ultimately the microstructure and performance of the fabricated parts. In-flight droplet plasma atomization (IDPA) is a fine metal powder production technique developed as an extension of conventional plasma atomization. By confining the atomization region, IDPA enhances droplet–plasma interaction and promotes secondary breakup, thereby facilitating the production of fine spherical powders. However, this confinement intensifies the coupling between the high-speed flow and thermal state within the nozzle, leading to severe metallic deposition that compromises process stability and continuous operation. To address this issue, this study proposes an outlet-thermal-state-oriented constrained flow-field regulation strategy based on the thermodynamic evolution of compressible flow inside the nozzle. A terminal contraction boundary was introduced to induce limited moderate deceleration and local static-temperature recovery of the high-speed gas flow after expansion. Numerical simulations and experiments were combined to investigate the thermal-fluid characteristics, droplet breakup behavior, deposition features, and powder particle size distribution before and after constrained flow-field regulation. The results show that the terminal contraction boundary mainly improves the thermal state near the nozzle outlet without significantly weakening the primary breakup in the throat and early diverging section. Under identical operating conditions, the nozzle average mass gain after 5 min of continuous operation decreased from 6.07 g to 1.5 g, and outlet deposition and build-up were markedly suppressed. Powder characterization showed that the d90of Ti–6Al–4 V powders produced before and after constrained flow-field regulation were 52.17 μm and 57.89 μm, respectively, both below 60 μm. These results demonstrate that outlet-thermal-state-oriented constrained flow-field regulation can effectively suppress metallic deposition while maintaining the powder refinement capability of IDPA, providing a feasible route for the continuous and stable production of fine spherical metal powders.

To achieve atomic-scale removal of Y2O3, the mechanochemical removal mechanism of Y2O3, modulated by UV/ O3 treatment, was systematically analyzed using atomic force microscopy. UV/O3-induced color centers are crucial for triggering mechanochemical removal at the Y2O3/Al2O3 interface. Color centers, created by electron excitation of Y atoms under UV light, facilitate the formation of Y-O-Al interfacial bonds under mechanical stress, which enables the atomic removal of the Y2O3 substrate while maintaining subsurface integrity and unchanged chemical composition and phase structure. Importantly, the formation of color centers is reversible, which makes it challenging for the Y2O3 surface to achieve nanoscale mechanochemical wear when mechanical chemical activity decreases. This work presents a novel, reversible, and non-destructive approach for atomicscale precision chemical mechanical polishing applications.

Plasma electrochemical polishing (PEP) is a novel technology for polishing the surfaces of metals with complex structures. The dynamic gas layer has a significant impact on the removal behavior in PEP, but it is rarely given due attention. In this study, we investigated the relationship between cations and the dynamic gas layer, and further linked these effects to the final polishing performance of the GH3044 alloy. The dynamic gas layer exhibits two primary states: turbulent fluctuation and dynamic stability. Li+ was found to induce turbulent vapor-gas envelope (VGE), leading to uneven material removal. Na+ and K+ promote the formation of a dynamically stable VGE; however, excessive thickness of the gas layer hinders the alloy dissolution process. NH4+ facilitates the formation of a stable and thickness-moderate VGE layer. The generated & centerdot;NH3 acts as a complexing ligand, effectively promoting the removal of surface oxides. Using optimized parameters, the surface roughness of the GH3044 alloy was markedly reduced from 240.1 nm to 44.6 nm. This result provides theoretical support for enhancing the surface finish of nickel-based superalloys.

Efficient, nondestructive, and cost-effective detection of the hollow ratio in ceramic powder remains an urgent technical challenge in the industrial field. In this study, a novel image recognition-based method for detecting the hollow ratio of ceramic powder was proposed. Using 8 mol% yttrium-stabilized zirconia powder as the research subject, a mapping relationship between the physical structure of hollow particles and their optical imaging characteristics was established. By conducting targeted image enhancement on the characteristics of ceramic particles, a high-resolution image annotation dataset was constructed, and the detection performance of the YOLOv5s, YOLOv8s, YOLOv9s, and YOLOv11s models was systematically compared. The results indicate that the YOLOv11s model demonstrates superior overall detection performance. Building upon this finding and integrating the OpenCV scale calibration algorithm, automatic statistical analysis of particle size distribution (D10, D50, D90) and hollow ratio was achieved, significantly enhancing both efficiency and accuracy. This study highlights the promising application potential of the proposed method in the field of powder metallurgy.

Atomic-level precision manufacturing is the main development direction for improving the surface performance of Y2O3 optical devices. In this study, we introduce an innovative UV/O3-enhanced chemical mechanical polishing (CMP) technique aimed at improving polishing efficiency, yielding improved removal rate without damaging the substrate structure. Following UV/O3 treatment, a material removal rate of up to 383.3 nm/min was achieved in the Y2O3 CMP process, and the surface roughness Sa was reduced to as low as 0.6 nm. High-resolution transmission electron microscopy analysis of the polished substrate revealed that the atomic structure remained largely undisturbed. The key to achieving such remarkable polishing performance lies in the formation of color centers within the Y2O3 lattice induced by UV irradiation. This process promotes electron loss in Y atoms, transforming them into reactive species. These activated Y atoms subsequently react with water to form Y-OH groups. During polishing, the mechanical stress exerted by SiO2 facilitates the formation of Si-O-Y chemical bonds at the SiO2/Y2O3 interface. Under shear stress, these bonds enable the selective removal of Y atoms from the Y2O3 surface without inducing structural damage.

The clinical management of recurrent aphthous stomatitis, commonly known as oral ulcers, remains a significant challenge. Existing topical pharmacotherapies─although capable of providing temporary symptomatic relief─are frequently limited by inadequate bioadhesion, short therapeutic duration, and critically, an inability to correct the immune dysregulation inherent in the healing process. To address these limitations, this study developed a hand-held cold atmospheric plasma jet device, termed the "Biphasic Unity Pen" (BU Pen). The device introduces an innovative "Demon Sphere-Spiritual Sphere" biphasic immunomodulation strategy, designed to achieve intelligent, stage-dependent, and time-regulated therapy for oral ulcers. The BU Pen stably generates reactive oxygen and nitrogen species, enabling sustained immunomodulation within the humid oral environment without reliance on physical adhesion. In vitro, the device sequentially induces M1 macrophage polarization to support inflammatory clearance (the "Demon Sphere"), followed by a timely transition to M2 polarization to facilitate anti-inflammatory repair (the "Spiritual Sphere"). Additionally, the BU Pen enhances epithelial cell and fibroblast migration and promotes basement-membrane assembly and cytoskeletal reorganization. In a rat oral-ulcer model, treatment with the BU Pen achieved healing rates of up to 92.9%, restored feeding behavior and body weight, and promoted collagen deposition and angiogenesis through the M1-to-M2 macrophage transition. Overall, this study presents a novel and intelligent physical-therapy strategy for oral ulcers and other inflammatory oral diseases, offering substantial potential for clinical translation.

The connection between vapor-gaseous envelope (VGE) characteristics and plasma-electrochemical reaction pathways in plasma electrochemical polishing (PEP) of titanium alloys remains unclear, which hampers further progress in this technique. In this study, we systematically examined how different VGE characteristics relate to the polishing behavior of the TA4 alloy surface as the electrolyte's initial temperature is varied. The reaction pathway of the TA4 alloy in PEP was elucidated by analyzing surface reaction products under varying VGE conditions. The VGE displays three primary characteristics: shaky-thin VGE, stable-thin VGE, and shaky-thick VGE. As the electrolyte's initial temperature rises, the VGE state sequentially shifts from the first to the third type. In the first state, TiOF2 becomes the main reaction product due to the balance between oxidation and fluorination. In the second stage, TiO2 becomes the main reaction product due to stronger oxidation. In the third stage, TiF4 becomes the main reaction product owing to F exhibits stronger effects. These findings provide essential theoretical guidance for achieving atomic-level precision in polishing titanium alloy surfaces.

Atmospheric inductively coupled plasma (ICP) etching has emerged as a critical technology for optical fabrication due to its damage-free etching, high removal efficiency, and adaptability to curved surfaces. However, the existing ICP torch design often struggles to achieve the high reactive gas ionization and low-temperature jet characteristics essential for etching applications. In this paper, a low-temperature ICP conical torch enabling stable plasma generation at reduced power inputs (250 600 W) was proposed. Through multi-physical coupling simulations, we analyzed the torch’s internal electromagnetic, temperature, and flow fields, which revealed the formation of the skin layer zone, the distribution of the core high-temperature zone, and the influences of the swirl, development, and blockage zones. On this basis, key structural parameters of the torch were optimized, including the taper of the variable-diameter section, the coil axial position and the nozzle throat geometry. Subsequently, etching experiments of fused silica were conducted to verify the removal efficiency and stability of the low-temperature ICP jet. It could achieve a peak removal rate of 11.19 μm/min and a volume removal rate of 0.69 mm3/min. The jet exhibited the relatively long-term stability, both axial and radial fluctuations of which were maintained below 5

Plasma atomization (PA) is capable of producing high-quality spherical metal powders for advanced additive manufacturing. However, its industrial scalability is fundamentally limited by unstable powder quality under nominally identical operating conditions. This instability originates from the dynamically coupled convergence behavior of multiple plasma jets, which remains insufficiently characterized and quantitatively evaluated. In this study, a jet profile extraction algorithm and a novel parametric jet morphology model are developed to enable high-accuracy reconstruction of three converging plasma jets. Compared with the conventional Gaussian model, the proposed model significantly improves fitting accuracy and enhances the representation of complex jet geometries. Building upon this model, a quantitative evaluation framework is established to characterize both the temporal stability of individual jets and the consistency of multi-jet systems. The offset of the jet convergence region relative to the ideal convergence point is introduced as a physically meaningful metric to quantify multi-jet consistency. PA experiments reveal a clear correlation between multi-jet consistency and powder characteristics under identical nominal operating conditions. Improved jet consistency leads to finer particle size distributions and higher fine powder yield, indicating that multi-jet consistency acts as a critical intermediate process variable governing powder quality. The proposed methodology provides a quantitative tool for evaluating plasma jet states and offers new insights into process stability in PA systems, while establishing a generally applicable framework for quantitatively characterizing critical intermediate jet states in plasma-based material processing systems employing non-transferred arc plasma torches.

Direct current (DC) plasma torches play a pivotal role in the field of material processing, with their performance largely determined by the characteristics of the plasma jet. However, the cascade DC plasma torch produces a plasma jet that has a small high-temperature region and a high velocity, which limits their powder processing rate. This paper designs a novel triple-anode plasma torch (TAPT) equipped with annular powder feeding to address these challenges. Comprehensive investigation into the plasma jet characteristics of the TAPT was carried out through a combination of experimental measurements and numerical simulations. Results show that the TAPT produces an optimal plasma jet for powder processing, marked by a large high-temperature region, low velocity, and high uniformity. The plasma jet’s peak temperature reaches over 20,000 K, with a 4,000 K region of 160 mm in length and 33 mm in diameter, and minimal regions exceeding a velocity of 80 m/s. The annular powder feeding of the TAPT guarantees a stable plasma jet for effective material processing, with the arc voltage exhibiting a small standard deviation of just 1.08 V. Furthermore, the TAPT’s effectiveness in powder processing was exemplified by spheroidization trials involving aluminum oxide powder, which yielded a practical specific energy requirement of approximately 4.35 kWh/kg. Overall, the TAPT shows considerable potential in the field of powder processing, specifically in raising the efficiency of powder spheroidization processes.

Ultrafine spherical powders (USP) with particle sizes below 45 mu m are essential for various advanced manufacturing processes, including 3D printing, metal injection molding, cold spray, etc. However, conventional methods for preparing spherical powders are characterized by a broad particle size distribution (PSD), which reduces the yield of ultrafine powders and increases production costs. To address this challenge, a novel method named in-flight droplet plasma atomization (IDPA) has been developed. This method involves three key stages, i.e., formulation of large droplet, generation of high-temperature atomization fluid, and breakup of large droplet. As the core of the IDPA process, the breakup of droplets significantly impacts the PSD, which is predominantly regulated by the flow-controlling nozzle. To elucidate the underlying mechanisms of the large droplet breakup, this study firstly investigates the operational sustainability through experimental analysis of electro-thermal characteristics and corresponding temperature distribution of the flow-controlling nozzle. Results show that maintaining the nozzle temperature within an optimal range is important to avoid clogging and reduce mechanical wear, thus ensuring continuous operation of the IDPA process. Then, a numerical simulation model of the large droplet breakup process within the flow-controlling nozzle was developed to investigate the USP formation and facilitate the prediction of PSD. By employing the IDPA method to prepare USP, ultrafine particle size with a d90 of 27.97 mu m, PSD within a range from 5.27 to 56.2 mu m, high spheroidization ratio approaching 100 %, and the complete absence of hollow powders have been achieved in the prepared atomized powders. It's proved that IDPA is a viable and efficient approach for the production of USP. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Plasma Electrochemical Polishing (PEP) is an advanced surface treatment technology with the potential to achieve high-precision surfaces with complex geometries. The key challenge lies in balancing the unique effects of plasma activation and electrochemical corrosion, which jointly act on the material surface during the material removal process. Due to the lack of dynamic studies on the PEP process, there are discrepancies in the understanding of its mechanisms. First, based on dynamic monitoring of the PEP process and analysis of the material surface composition, the removal mechanism between plasma and electrochemical effects during the PEP process of GH3044 alloy was elucidated. Material removal is primarily driven by electrochemical dissolution. Concurrently, the plasma activates common substances (H2O and -COOH) into high-energy species (& sdot;OH, H2O2, O3, and -COOH*). The preferential generation of reactive oxygen species leads to the formation of an oxide layer, thereby reducing the overall removal rate. Secondary-generated reactive complexes, such as -COOH*, further promote material removal. Through optimization, the surface roughness RMS in the local region can be significantly reduced to below 1.0 nm when a voltage of 250 V is applied. This study aims to elucidate the interaction between plasma and electrochemical effects, laying the foundation for achieving high-precision surface manufacturing with complex features.

Titanium (Ti) implants have become widespread especially in dentistry and orthopedics, where macrophage-driven osteoimmunomodulation is crucial to their success. Hydrophilic modification of Ti represents a promising strategy to enhance its immune and osteogenic responses. Herein, the osteoimmunomodulatory performance and integrin-mediated mechanism of novel non-thermal atmospheric plasma (NTAP) treatment to induce a hydrophilic Ti were investigated for the first time. Compared to a hydrophobic surface, NTAP-modified Ti possessed a 3-fold increase of pro-healing M2 macrophage makers, and the doubled osteogenic differentiation of mesenchymal stem cells was demonstrated in this immune microenvironment, thus improving early osseointegration. Mechanistically, the ameliorative osteoimmunomodulatory properties of NTAP were attributed to its positive and negative modulation in macrophages' integrin β1 or β2, and the subsequent FAK-PI3K/Akt or NF-κB signaling pathway. Collectively, this study highlighted the role of integrins and related signaling pathways in hydrophilic implant-caused macrophage polarization, therefore inventively unveiling the underlying mechanism of NTAP-enhanced osteoimmunomodulation. Furthermore, it established a robust theoretical foundation for the clinical application of this cost-effective, versatile, and transformation-valuable surface engineering strategy for the development of next-generation Ti implants.

Driven by the “dual-carbon” policy, arc steam plasmas provide high-temperature, low-cost, and environmentally friendly heat sources for a variety of applications. However, severe anode erosion caused by steam condensation has limited the large-scale application of arc steam plasma torches. Suppressing condensation depends on reducing heat loss from steam in the anode cold boundary layer, a process that is influenced by plasma flow field characteristics, yet the effects of these characteristics have not been systematically reported. This study investigates two representative flow fields: one generated by a trumpet-shaped anode, which forms stratified flow between the cold boundary layer and the plasma, and the other produced by a stepped anode, which enhances boundary layer turbulence. Through systematic experiments and numerical simulations, the study comparatively analyzes their electro-thermal characteristics, anode exit temperatures, anode erosion behavior, and physical properties inside the torch. The results show that plasma flow field characteristics have a significant impact on anode erosion: stratified flow fields lead to severe erosion, while turbulence-enhanced flow fields can significantly suppress it. Moreover, only under turbulence-enhanced flow fields is the electron temperature at the torch exit higher and sensitive to changes in current. These findings highlight the importance of turbulence-enhanced flow fields for extending the operational lifetime of steam plasma torches.

The unclear links between macroscopic input parameters and microscopic active particle motions in DBD plasma impeded controllable plasma processing. This paper investigates effects of O-2/CF4 content on Ar-DBD characteristics and active particle distributions using a flat-plate reactor and fluid model of 10-50 kHz. Results suggest adding CF4 promotes filament discharge, while O2 favors uniform glow discharge. Near-equal O-2/CF4 content yields mixed mode. Higher O-2/CF4 content reduces most active particle densities (except O+) but increases all particle fluxes to material surface. Elevated frequency boosts total density and flux of O, O+, O-, F, F- particles. Spatially, F/F-/O+ particles concentrate centrally, O/O- distribute peripherally-increased frequency shifts O enrichment area inward and expands F/F- enrichment area outward.

Ultrasonic vibration-assisted helical grinding(UVHG) has emerged as a novel method for hole precision machining in brittle silicon carbide(SiC) ceramics. The impact of coupled multiple movements in UVHG makes the materials removal mechanism, the evolution law of tool wear and machining quality extremely complicated. To address that, this paper systematically investigates the UVHG of SiC ceramics for hole-making through theoretical modeling, simulation analysis, and experimental validation. Based on the indentation fracture theory and the trajectory analysis of abrasives, the SiC ceramics removal mechanism of UVHG is investigated considering the impact of multi-abrasive. The SiC ceramics removal process can be divided into four stages, sequentially named abrasive indentation, crack expansion, crack interweaving and material removal. Considering the influence of the previous and subsequent cut-in positions of the abrasive, a dual-abrasive simulation is constructed to verify the material removal mechanism and determine the influence of process parameters on the material removal process. It’s found that ultrasonic vibration enhances the crack interweaving effect in removing material from adjacent cut-in positions. A mechanical model of UVHG is constructed by novelly combining the conical frustum removal volume and the semi-ellipsoid removal volume. The model exhibit congruence with experimentally measured grinding forces in trend variation patterns. Through the hole-making experiment of UVHG, the influence law of process parameters on grinding force is obtained and utilized to calibrate the mechanical model. Moreover, the grinding wheel wear is analyzed by characterizing the topography of the worn wheel and the machining quality of the machined hole. The UVHG method has been proven effective in improving the wheel wear by enhancing the crack interweaving and optimizing the motion trajectory of abrasives, contributing to the maximum reduction in the roughness of the hole’s bottom surface by 41.8

Plasma spraying is a critical surface coating technique extensively used across various industries to improve the surface characteristics of workpiece. Accurate modelling of the coating thickness distribution is vital for trajectory planning and optimizing process parameters in the robotic plasma spray system. Traditional models for coating thickness distribution often assume a Gaussian powder distribution in the nozzle's external space. However, this assumption is frequently inaccurate, as the spatial distribution of powder in radial powder-feeding plasma spraying is typically asymmetrical rather than Gaussian, limiting the applicability of these models in real-world operations. To overcome this limitation and improve the prediction accuracy, this paper proposes a novel multivariate model for coating thickness distribution that considers the asymmetrical spatial distribution of powder. The model incorporates variables such as plasma spray torch speed, spray angle, and spray distance, allowing for the prediction of coating thickness under diverse powder feeding scenarios. To validate the model's effectiveness, plasma spraying experiments involving spot and linear spraying were conducted under various parameters. Then the corresponding coating thickness prediction using our proposed model was compared against that using a conventional bimodal Gaussian model. The comparative analysis demonstrated that our model offers superior fitting accuracy and reduced error margins, thereby validating its reliability.

Yttria-stabilized zirconia hollow spherical powder (YSZ-HOSP) is a widely utilized ceramic material in thermal barrier coatings (TBCs). Within the category of YSZ-HOSP, yttria-stabilized zirconia spherical thin -walled hollow -shell powder (YSZ-STHS) displays immense potential for producing TBCs with minimal inter -lamellar porosity and cracks. Arc plasma torch equipped with flow -shaping nozzle shows promise for preparing YSZSTHS. However, there is limited research on the impact of the nozzle geometry on plasma flow field characteristics and the resulting effect on the quality of YSZ-HOSP, particularly in terms of spheroidization ratio, hollow -shell powder ratio, and shell thickness. To achieve controllable preparation of YSZ-STHS in arc plasma spheroidization, this paper proposed a novel model for the formation of YSZ-HOSP under different plasma flow characteristics, including high-speed compressing flow field, intermediate -speed critical flow field, and lowspeed expanding flow field. These different plasma flow characteristics were achieved by changing the nozzle diameter and investigated by both numerical simulation and experiments in terms of plasma flow characteristics, electro-thermal characteristics, and the quality of the YSZ-HOSP. Results reveal that YSZ-HOSP prepared with high-speed compressing flow field resulted in a low hollow -shell powder ratio, while low -speed expanding flow field led to an over -thick shell. Conversely, the intermediate -speed critical flow field demonstrates relatively high thermal efficiency and enthalpy, along with moderate jet temperature and velocity, resulting in YSZ-STHS with a spheroidization ratio of 96.6 %, a hollow -shell powder ratio of 92.5 %, and a mean shell thickness of 3.49 mu m. Therefore, it is evident that manipulating plasma flow characteristics allows for the controlled preparation of YSZ-STHS.