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Spherical powder materials are essential raw materials for manufacturing processes such as metal additive manufacturing and powder metallurgy. They possess characteristics that are key factors influencing the performance of additive manufacturing. This paper introduces the fundamental principles and characteristics of laser additive manufacturing technology and analyzes the technical principles, advantages, and disadvantages of three alloy powder preparation methods: gas atomization, centrifugal atomization, and plasma atomization. It further elucidates the influence of process parameters of these three powder preparation techniques on the characteristics of alloy powders. Finally, the development trends in alloy powder preparation for laser additive manufacturing are projected.

Minimum quantity lubrication (MQL) is a relatively efficient and clean alternative to flooding workpiece machining. Electrostatic atomization has the merits of small droplet diameter, high uniformity of droplet size, and strong coating, hence its superiority to pneumatic atomization. However, as the current research hotspot, the influence of jet parameters and electrical parameters on the average diameter of droplets is not clear. First, by observing the shape of the liquid film at the nozzle outlet, the influence law of air pressure and voltage on liquid film thickness ( h ) and transverse and longitudinal fluctuations are determined. Then, the mathematical model of charged droplet volume average diameter (VAD) is constructed based on three dimensions of the liquid film, namely its thickness, transverse wavelength ( λ h ), and longitudinal wavelength ( λ z ). The model results under different working conditions are obtained by numerical simulation. Comparisons of the model results with the experimental VAD of the droplet confirm the error of the mathematical model to be less than 10%. The droplet diameter distribution span value Rosin-Rammler distribution span (R.S) and percentage concentrations of PM10 (particle size of less than 10 µm)/PM2.5 (particle size of less than 2.5 µm) under different working conditions are further analyzed. The results show that electrostatic atomization not only reduces the diameter distribution span of atomized droplets but also significantly inhibits the formation of PM10 and PM2.5 fine-suspension droplets. When the air pressure is 0.3 MPa, and the voltage is 40 kV, the percentage concentrations of PM10 and PM2.5 can be reduced by 80.72% and 92.05%, respectively, compared with that under the pure pneumatic atomization condition at 0.3 MPa.

The so-called close-coupled gas atomization process involves melting a metal and using a high-pressure gas jet positioned close to the melt stream to rapidly break it into fine, spherical powder particles. This technique, adapted for blast furnace slag granulation using a circular seam nozzle, typically aims to produce solid slag particles sized 30–140 µm, thereby allowing the utilization of slag as a resource. This study explores the atomization dynamics of liquid blast furnace slag, focusing on the effects of atomization pressure. Primary atomization is simulated using a combination of the Volume of Fluid (VOF) method and the Shear Stress Transport k-ω turbulence model, while secondary atomization is analyzed through the Discrete Phase Model (DPM). The results reveal that primary atomization progresses in three stages: the slag column transforms into an umbrella-shaped liquid film, whose leading edge fragments into particles while forming a cavity-like structure, which is eventually torn into ligaments. This primary deformation is driven by the interplay of airflow velocity in the recirculation zone and the guide tube outlet pressure (Fp). Increasing the atomization pressure amplifies airflow velocity, recirculation zone size, expansion and shock waves, though the guide tube outlet pressure variations remain irregular. Notably, at 4.5 MPa, the primary deformation is most pronounced. Secondary atomization yields finer slag particles as a result of more vigorous primary atomization. For this pressure, the smallest average particle size and the highest yield of particles within the target range (30–140 µm) are achieved.

Flow physics plays a key role in nearly every facet of the COVID-19 pandemic. This includes the generation and aerosolization of virus-laden respiratory droplets from a host, its airborne dispersion and deposition on surfaces, as well as the subsequent inhalation of these bioaerosols by unsuspecting recipients. Fluid dynamics is also key to preventative measures such as the use of face masks, hand washing, ventilation of indoor environments and even social distancing. This article summarizes what we know and, more importantly, what we need to learn about the science underlying these issues so that we are better prepared to tackle the next outbreak of COVID-19 or a similar disease.

The present work studies low viscosity twin-fluid atomization experimentally and analytically to characterize and predict the droplet size distribution of the spray. The study is based on experiments conducted using commercially available twin-fluid nozzles with water as the liquid. Shadowgraph images were used to visualize the near-nozzle flow while the droplet size distribution was measured in the far field using a Malvern Spraytec. To analytically model the atomization of the spray, the authors’ recent works on aerodynamic droplet breakup, which describe the formation and breakup of ligament and bag structures by multiple mechanisms, are extended to provide an analytical prediction of the droplet size distribution of the spray that is validated against the present experiments. The present model is developed to be a good physical representation of the spray behaviour at practical operating conditions. A Python implementation of the model has been deposited in a GitHub repository to accompany this work.

FeSiBCCr amorphous powders were produced by a novel gas–water combined atomization process, and the corresponding MPCs (magnetic powder cores) were subsequently fabricated by phosphating treatment (0.4~1.6 wt.%), cold pressing (550~2350 MPa), and annealing (423~773 K), respectively. The results showed that the powders had high circularity, excellent thermal stability (ΔT = 59 K), and high saturation magnetization (0.83 T), which could provide raw powders for high-performance MPCs. With increasing phosphoric acid concentrations, despite the increase in DC-bias%, the uniformity of the insulation layers deteriorated, which led to a decrease in permeability and an increase in core loss. With increasing compaction pressures, the core loss increased continuously, and the permeability and DC-bias% first increased and then decreased. When annealing below the crystallization temperature, with increasing annealing temperatures, the permeability increased, and the core loss and DC-bias% decreased continuously. Under the optimized process of 0.4 wt.% phosphating concentration, 550 MPa pressure, and 773 K annealing temperature, the MPCs had a permeability of 21.54 ± 1.21, DC-bias% of 90.3 ± 0.2, and a core loss (Bm = 50 mT, f = 100 kHz) of 103.0 ± 26.3 mW cm−3. The MPCs had excellent high-frequency low-loss characteristics and showed great application potential under the development trends of high current, high power, and high frequency of electronic components.

This paper presents issues in the field of theory, construction, calculations, as well as the design of effervescent-swirl atomizers. The results of experimental studies of spraying liquids with different physico-chemical properties for this type of atomizers are discussed. Effervescent-swirl atomization is a complex process and its mechanism is not fully understood. Therefore, the purpose of the manuscript is the complexity of the atomization process and its mechanism as well as the influence of individual parameters on its efficiency were thoroughly analyzed. The analyzed parameters include: atomizer design, outlet shape, gas and liquid flow rate, injection pressure, physicochemical properties of the atomized liquid, pressure drop, outflow coefficient, spray angle, quantitative droplet distributions, and average droplet diameter. Moreover, in the work, on the basis of the literature review, the results of the research related to, inter alia, the phenomenon of air core formation and the influence of a number of parameters on the efficiency of the atomization process are analyzed. The literature review included in the work makes it possible to better understand the atomization process carried out in effervescent-swirl atomizers, and also provides better design criteria and analysis of the efficiency of the tested devices. The article presents correlation equations covering the basic features of the atomization process, which relate a large number of parameters influencing the efficiency of this process and the character of the sprayed liquid, which may be useful in design practice.

To analyze the distribution pattern concerning multi-nozzle interference spray particle granularity between hydraulic supports, the present study conducts atomization interference experimental characterization for three types of nozzles used in coal mines based on a Doppler laser interference spray dust suppression simulation experimental system. The results indicate that for single-nozzle atomization, the impact of spray pressure on spray droplet size is gradually subdued, and a spray pressure of 8 MPa yields the best result; compared with single-nozzle spray, the multi-nozzle atomization interference effect can downsize the spray field overlapping zone, leading to an improved uniformity of overall spray particle distribution. As the spray field overlapping coefficient k increases, the particle size of the interference spray field decreases first and then increases. As the spray field overlapping coefficient reaches 0.4, the distribution of spray droplet size is most concentrated, corresponding to the optimal atomized dust suppression effect. Practical testing indicates that the optimal spray field overlapping coefficient measured at a fully mechanized mining face agrees well with the experimental result. Under the optimal parameters, the average total dust and respirable dust suppression rates measured at various measuring points on the downwind side during support relocation reach 78.93% and 80.53%, respectively.

Epoxy syntactic foam (ESF) materials are widely used in marine detection systems, deep sea diving equipment, offshore oil exploration and other deep sea development and exploration equipment due to their superior properties such as low density, high compressive strength and low water absorption. The composition and preparation process of the ESF material determine the structure of the ESF material, the structure determines the performance, and the performance determines the application of the ESF material. The review describes the epoxy-based syntactic foams from the following aspects: definition and classification, preparation methods, properties and influencing factors, application, problems and development trend. The forming methods of hollow glass microspheres (solid-state powder processing method and liquid atomization method), hollow polymer microspheres (spray drying method) and centimeter-sized hollow spheres (rolling ball method and electrostatic fiber flocking method) are introduced in detail, as well as the casting molding method, vacuum molding method and pressure molding method of the syntactic foams. The main objective of this paper is focusing on the influence of various factors including filler content, graded structure, clay material, carbon material, fiber-reinforced material, molding process, material structure (sandwich structure) on the compressive strength and the density of the syntactic foam in detail. The paper may also provide some guidance to the preparation of ESF used in deep sea development and exploration equipment.

Atomization is an intricate operation involving unstable and complex networks with rupture and fusion of liquid molecules. There are diverse details that typify the spray formation, which are the technique and configuration of the atomization process, dimension and structure of the nozzle, experimental parameters, etc. Ultimately, the process generates fine sprays from the bulk of a liquid. Some examples of atomization that we come across in our day-to-day life are antiperspirant or hair spray, shower head, garden sprinkler, or cologne mist. In this review paper we are briefly discussing the theoretical steps taking place in an atomization technique. The instabilities of the jet and sheet are explained to understand the underlying theory that breaks the jet or sheet into droplets. Different types of atomization processes based on the energy sources are also summarized to give an idea about the advantages and disadvantages of these techniques. We are also discussing the various biomedical applications of the electrohydrodynamic atomization and its potential to use as a drug delivery system. In short, this paper is trying to demonstrate the diverse applications of atomization to show its potency as a user friendly and cost-effective technique for various purposes.