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In this study, K390 powder was fabricated by means of the plasma rotating electrode process (PREP), and the microstructure and properties of the powder were examined. The findings indicated that as the rotating speed increased, the particle size of the powder decreased. The particle size distribution was generally normal and mainly ranged from 45 to 75 micrometers. The proportion of fine powder was low (less than 5 wt.%). The powder was spherical in shape with a smooth surface and no satellite-shaped particles. At a rotating speed of 31000 revolutions per minute, some spheroidal particles were formed. As the rotating speed continued to rise, the spheroidal particles vanished. Additionally, as the rotating speed increased, the apparent density of the K390 powder increased while the fluidity decreased significantly.

High-quality powders with spherical particles and controllable properties can be produced using centrifugal force. This review provides a comparative analysis of two centrifugal atomization techniques: the plasma rotating electrode process (PREP) and centrifugal atomization (CA). It systematically examines the fundamental principles, film disintegration modes, and the resultant powder characteristics, with a focus on mechanisms that lead to common defects. By evaluating current technological limitations and highlighting potential pathways for advancement, this review aims to offer valuable insights for the future development of high-quality, spherical metal powders for advanced manufacturing applications.

This study describes the preparation, characterization, and biosensing applications of Radio Frequency (RF) plasma-modified magnetic micro/M/Janus micromotors. In the first part of the study, two different Janus micromotors were fabricated. Firstly, Fe 3 O 4 magnetic micro/particles were functionalized with –OH groups under plasma treatment, and then Fe 3 O 4 and Fe 3 O 4 -OH NPs/Platinum (Pt) (Fe 3 O 4 /Pt and Fe 3 O 4 -OH/Pt) micromotors were prepared by Pt coating of one side of Fe 3 O 4 and Fe 3 O 4 -OH nanoparticles using by RF magnetron sputtering method. The work is the first example of RF rotating plasma preparation of modified magnetic nano/particle-based motors. Thus, it is of great interest to nano/micromachinery field. The synthesized micromotors were characterized by scanning electron microscopy (SEM) and energy-dispersive X-Ray spectroscopy (EDX) analysis. The dependence of the mobility of the motors on fuel concentration was evaluated. High speeds of 255 μm s − 1 and 128 μm s − 1 at 5% hydrogen peroxide (H 2 O 2 ) were observed for Fe 3 O 4 /Pt and Fe 3 O 4 -OH/Pt micromotors, respectively. Besides these remarkable values, long lifetimes of 15 min with Fe 3 O 4 /Pt micromotors and 20 min with Fe 3 O 4 -OH/Pt micromotors were achieved. In the second part of the study, these Janus micromotors were used in miRNA-21 biosensing. The changes in the fluorescence intensity and in the speed of micromotors were examined after hybridization. Performances of these two novel micromotors were compared to present their potential use in early cancer diagnosis. Promising results with the functionalized Fe 3 O 4 -OH/Pt micromotors were obtained.

In this study, the distribution, proportion and characteristics of internal defects in three kinds of powders of Ti-6Al-4V, 316-steel and Co-29Cr-6Mo alloys, produced by the plasma rotating electrode process (PREP) at various rotation speeds, are characterized by using both scanning electron microscopy (SEM) and synchrotron X-ray computed tomography (CT). The results show that in the powder of a given alloy, internal pores are formed more easily in coarse particles than in fine powder during PREP. The proportion of powder with pores can be reduced by appropriately increasing the rotation speed. In addition, the composition of an alloy has a great influence on the defect formation.

The plasma rotating electrode process (PREP) is an ideal method for the preparation of metal powders such as nickel-based, titanium-based, and iron-based alloys due to its low material loss and good degree of sphericity. However, the preparation of silver alloy powder by PREP remains challenging. The low hardness of the mould casting silver alloy leads to the bending of the electrode rod when subjected to high-speed rotation during PREP. The mould casting silver electrode rod can only be used in low-speed rotation, which has a negative effect on particle refinement. This study employed continuous casting (CC) to improve the surface hardness of S800 Ag (30.30% higher than mould casting), which enables a high rotation speed of up to 37,000 revolutions per minute, and silver alloy powder with an average sphericity of 0.98 (5.56% higher than gas atomisation) and a sphericity ratio of 97.67% (36.28% higher than gas atomisation) has been successfully prepared. The dense S800 Ag was successfully fabricated by laser powder bed fusion (LPBF), which proved the feasibility of preparing high-quality powder by the “CC + PREP” method. The samples fabricated by LPBF have a Vickers hardness of up to 271.20 HV (3.66 times that of mould casting), leading to a notable enhancement in the strength of S800 Ag. In comparison to GA, the S800 Ag powder prepared by “CC + PREP” exhibits greater sphericity, a higher sphericity ratio and less satellite powder, which lays the foundation for dense LPBF S800 Ag fabrication.

TiAl pre-alloyed powder is the foundation for additive manufacturing of TiAl alloys. In this work, TiAl pre-alloyed powder was prepared using a plasma rotating electrode process (PREP). The effects of electrode rotating speeds and current intensity on the microstructure and characteristics of TiAl pre-alloyed powder have been investigated in detail. The results show that the electrode rotating speeds mainly affected the average particle size of the powder (D50). As the electrode rotating speed increased, the D50 of the powder decreased. The current intensity mainly affected the particle size distribution of the powder. As the current intensity increased, the particle size distribution of the powder became narrower, which was concentrated at 45~105 μm. In addition, the current intensity had a significant effect on the sphericity degree of the powder with the particle size > 105 μm, but it had little effect on that <105 μm powder. TiAl pre-alloyed powder with a particle size > 45 μm demonstrated a dendritic + cellular structure, and the <45 μm powder had a microcrystalline structure. The powder was mainly composed of the α2 phase and γ phase. There were two kinds of phase structure inside the powder, namely the α2 + γ lamellar microstructure (particle size < 45 µm) and the α2 + γ network microstructure (particle size > 45 µm). The phase structure of the powder was related to the solidification path and cooling rate of molten droplets in the PREP. The average thickness of the α2 + γ lamellar was about 200 nm, in which the lamellar γ phases were arranged in an orderly manner in the α2 phase matrix with a thickness of about 20 nm. The network phase structure was corrugated, and the morphology of the γ phase was not obvious.

A warm degenerate magneto-rotating quantum plasma (WDMRQP) model consisting of a static heavy nucleus, inertial non-degenerate light nucleus, and warm non-relativistic or ultra-relativistic electrons has been considered to observe the generation of nucleus-acoustic (NA) solitary waves (NASWs). A Korteweg–de-Vries-type equation is derived by using the reductive perturbation method to describe the characteristics of the NASWs. It has been observed that the temperature of warm degenerate species, rotational speed of the plasma system, and the presence of heavy nucleus species modify the basic features (height and width) of NASWs in the WDMRQP system and support the existence of positive NA wave potential only. The applications of the present investigation have been briefly discussed.

Titanium alloy powders were prepared from titanium rods by plasma rotating electrode process (PREP). The effects of powder preparation technology on the morphology and properties of titanium alloy powders were studied by laser particle size analyzer, scanning electron microscope (SEM), X-ray diffraction, powder comprehensive property tester and oxygen nitrogen analyzer. The results shown that the titanium alloy powder prepared by PREP had uniform particle size distribution, sphericity >93% and oxygen content <1000 ppm. For TA1 powder, the phase’s structure was mainly composed of HCP-α phase, while the TC4 powder mainly composed of α' phase. During the preparation process, the particle size and sphericity of the alloy powder increased with the increase of electrode speed. The smaller the particle size and the higher the sphericity of the alloy powder, the larger the compacting density and bulk density, but the powders fluidity became worse. At the same time, the oxygen content of the titanium alloy powder increased with the decrease of the particle size, while the nitrogen content was not affected by the powder size. The oxygen content of the titanium alloy powder increased as the particle size became smaller, and the nitrogen content was not affected by the powder size.

Since molybdenum has very high melting point of 2620 °C, there are many difficulties in its forming and post-processing, especially for deep processing. Furthermore as molybdenum is expensive, the utilization rate is important for the molybdenum processing. Additive manufacturing can directly manufacture the parts without mold and increase the utilization rate, and brings an opportunities for the new direction of deep processing for molybdenum. Due to the high quality requirements of molybdenum powder in additive manufacturing technology, the high-quality spherical molybdenum powder was prepared by plasma rotating electrode process method in the present study. The morphology, particle size and particle size distribution, chemical and physical properties were investigated. The molybdenum powder prepared by plasma rotating electrode process method showed to have high purity, high sphericity, good fluidity and high bulk density, proper particle size distribution and low gap element within the powder. The microstructure of the powder was a mixed structure of dendrites and cell crystals formed by rapid solidification, and as the particle size of the powder gradually decreased, the microstructure of the powder surface was remarkably refined. Within a certain range, the molybdenum powder with a wide particle size distribution had better fluidity and higher bulk density. The high-quality spherical molybdenum powder was prepared by plasma rotating electrode process method, which can meet the requirements of additive manufacturing technology for powder material performance.

The Dense Plasma Focus (DPF) is such a simple device that it has awakened deep interest as a source of neutrons and as a possible alternative to the generation of energy by nuclear fusion. In essence, a DPF consists of two concentric electrodes between which a plasma sheet is formed by the action of an electrical discharge. Then, this sheet is accelerated until it collapses at the end of the device, generating a hot and extremely dense plasma. One of the most widely theoretical models used for describing the physical processes taking place in the DPF is Lee’s as it fits very well to the experimental data. This model divides the operation of the DPF into five phases. On the other hand, the poisoning of the plasma by particles from the electrodes can be reduced by rotating the plasma through the presence of an axial magnetic field. However, this generates a series of processes that were not taken into account in Lee’s original model. In this work, a variant of the Lee Model describing the rotational effects of plasma is presented. The new model brings new parameters and phenomena to be analyzed, such as the angular velocity and the swirl acceleration effect. The reduction of plasma temperature and also the reduction in neutron yield as observed experimentally, are also explained.