Particle Size Distribution Of Powder Research Articles

Influence of powder particle size distribution on microstructure and mechanical properties of 17-4 PH stainless steel fabricated by selective laser melting

This study explores the influence of particle size distribution (PSD) and heat treatment on 17-4 PH stainless steel fabricated by selective laser melting, which greatly improved the elongation of the material on the basis of ensuring the strength. Scanning electron microscope and electron backscattering diffraction were used to characterize the microstructure of 17-4 PH stainless steel. 17-4 PH stainless steel PSD+ and PSD− samples have obtained equiaxed grain, and the internal tissue distribution in PSD+ sample crystals is uneven. By reason of the gas in the large partials of PSD+ powder falling into the size distribution of 49 μm–58.9 μm, it was difficult to escape during the SLM process, which reduced the material density and mechanical properties. Compared with the PSD+ specimens, the tensile strength, hardness and elongation of the PSD− specimens are increase to 345.2 HV, 938.7 MPa, and 22%, respectively. This trend is retained after heat treatment, and the surface hardness, tensile strength and elongation rate of PSD− HT specimens, which are 5.3%, 5.4% and 12.9% higher compared with the PSD+ HT specimens, respectively.

Influences of double-sided molding method and initial particle size on fragmentation characteristics of reconstituted coal briquette

Using the reconstituted coal briquette to replace tectonic coal is a forced choice for many experimental studies on the mechanism of coal and gas outbursts. The molding method and initial particle size are two important factors affecting the properties of the soil-like coal briquette. In this study, tectonic coal particles with five different initial sizes were compressed into coal briquettes using three different molding methods. Each coal briquette was evenly divided into five parts along the vertical direction and each subunit was fragmented by a drop hammer to test the firmness. The results show that the briquette density first increases and then decreases with the rise of initial particle size. Briquettes obtained by the traditional one-sided molding method possess the lowest density. The fragment size distributions of the briquettes and the original tectonic coal have segmented and non-segmented fractal characteristics, respectively, which are mainly related to the initial particle size distribution of the coal powder used for making briquettes. Combining the vertical distribution laws of the surface work, Protodyakonov coefficients, and fractal dimension of the briquettes, it is determined that the coal briquettes obtained by the double-sided molding method are soft in the middle and possess a relatively symmetric structure. The surface work and Protodyakonov coefficients of the briquettes (9.03 ± 2.27 J/m2 and 0.10 ± 0.02, respectively) are comparable to those of the in-situ tectonic coal with the highest outburst risk.

Simulation Analysis of Spreading Process and Electron Beam Melting of Ti6Al4V Powder

Forming process control of powder bed fusion (PBF) additive manufacturing (AM) is the key to produce high-quality qualified parts. In this paper, spreading powder process and electron-beam melting (EBM) of Ti6Al4V powder were simulated based on simulation technology, and the state of powder bed powder and melting trajectory characteristics were characterized. Firstly, the particle size distribution of Ti6Al4V powder was tested, and the particle diameter of normal distribution for simulation was determined. Then, the simulation models of spreading powder and EBM model were established. Finally, based on the simulation results, the effect of processing parameters on the quality of powder laying is analyzed, and the morphology of EBM melting trajectory is characterized.

Application of Surfactant Activated Milling for Production of Nd–Fe–B Magnets by PLP Technology

The granulometric composition of Nd–Fe–B powders has been studied in detail after vibratory milling for various times both without and with the addition of siloxane. Sintered magnets were produced by the powder metallurgy method that excluded the pressing of powders. Correlations between the particle size distribution in the initial powders, microstructure of sintered magnets, and their magnetic hysteresis properties have been established. The difference in methods for estimating the size of powder particles by two methods is demonstrated. It is shown that the size distributions of powder particles and magnet grains are bimodal and are described by a superposition of two lognormal distributions.

Effect of yttria addition on the microstructure and mechanical behavior of ODS ferritic alloys processed by High Energy Milling and Spark Plasma Sintering

Oxide dispersion strengthened (ODS) ferritic alloys are structural materials used in nuclear fusion reactors, which exhibit enhanced mechanical properties, as well as corrosion and irradiation resistance. In the present work, ODS ferritic alloys with composition Fe-14Cr-1.5W-0.4Ti-(0, 0.4, 0.8) Y2O3 (in wt.%) were prepared employing high energy milling (HEM) followed by Spark Plasma Sintering (SPS). The particle size distribution (PSD) of the milled powders was characterized by laser diffraction. These powders and the sintered materials produced were characterized using X-ray diffraction (XRD), and scanning electron microscopy (SEM). The sintered materials were also characterized by dilatometry, diametral compression, Vickers microhardness, and corrosion rate tests. The largest Young’s modulus, microhardness, and dimensional shrinkage/expansion were obtained for the 0.8 wt.% Y2O3 alloy. However, this alloy was the least ductile. Furthermore, the 0.8 wt.% Y2O3 alloy was the one with the least dimensional change. According to the potentiodynamic polarization studies, it was found that the protective layer of Cr2O3 formed on the surface of the three alloys studied was less effective for the yttria-free alloy, since in this case the rupture of such protective layer occurred earlier than for the case of the yttria-containing alloys. Based on these results, it is suggested that the 0.8 wt.% Y2O3 alloy having fine microstructure could constitute a potential alternative as a structural material for Gen IV-type reactors.

In situ self-assembly preparation and characterization of CaO–ZrO2 nanopowders under vacuum

CaO–ZrO2 nanocomposite powders were prepared by in situ self-assembly method under vacuum. The effects of calcium oxide content on the physical phase composition and microscopic morphology of the as-prepared nanopowders were investigated. The results showed that the content of the tetragonal phase in the powders gradually increased with increasing calcium oxide content. When the calcium oxide content reached 10 wt%, the prepared CaO–ZrO2 nanopowders were a pure tetragonal phase with good dispersion and average particle size about 57 nm. In comparison to the situation in air, the amorphous carbon particles formed by the pyrolysis of organic matter under vacuum were evenly distributed on the surface of the nanocomposite particles or between them. In this way, direct contact of the nanoparticles was avoided, thus inhibiting their rapid growth at high temperatures and facilitating the formation of fine grains with high surface energy. The preliminary results indicated that the smaller average particle size and narrower particle size distribution of the nanocomposite powders prepared in vacuum were significantly beneficial for improving the bending strength of the nanoceramic products compared to that in air. It is expected to provide valuable information for further optimization of the controllable preparation of high-quality nanoceramic powders.

Powder Spreading Mechanism in Laser Powder Bed Fusion Additive Manufacturing: Experiments and Computational Approach Using Discrete Element Method.

Laser powder bed fusion (LPBF) additive manufacturing (AM) has been adopted by various industries as a novel manufacturing technology. Powder spreading is a crucial part of the LPBF AM process that defines the quality of the fabricated objects. In this study, the impacts of various input parameters on the spread of powder density and particle distribution during the powder spreading process are investigated using the DEM (discrete element method) simulation tool. The DEM simulations extend over several powder layers and are used to analyze the powder particle packing density variation in different layers and at different points along the longitudinal spreading direction. Additionally, this research covers experimental measurements of the density of the powder packing and the powder particle size distribution on the construction plate.

The impact of coal gasification slag powder on fluidity, rheology and viscoelasticity properties of fresh cement paste

Coal gasification slag (GS) is a potential pozzolanic industrial waste discharged during coal gasification. The study aimed to investigate the effect of finely ground GS powder on the fluidity, rheology and viscoelasticity properties of cement paste, which is essential for utilizing GS as a supplementary cementitious material for building materials. The research revealed that the morphology, physical filling effect, and particle size distribution of GS powder played a vital role in the workability of cement. The particle size distribution of the GS-cement system followed the Rosin-Rammler distribution model, and the width of the particle size distribution negatively correlated with paste fluidity. The rheological characteristics of blended paste transitioned from Bingham to modified Bingham fluid with increased GS powder content, showing shear thinning. Plastic viscosity can predict the fluidity and thixotropy of the paste. GS powder at 10% content broadened the particle size distribution, improved fluidity and rheological properties, with minimal effect on viscoelastic characteristics. With increased GS powder content, plastic viscosity, yield stress, and thixotropy of blended paste increased continuously, resulting in a slow transition from viscosity to elastic solid. Extending mechanical grinding time improved the fineness and activity of GS powder, optimized the particle size distribution, and reduced water demand, minimizing negative effects.

Grain size and shape fractal characteristics of gangue in the process of 'jaw breaking-ball milling'.

This study investigates the fractal characteristics of the particle size and shape distribution of gangue powder in the "jaw crushing-ball milling" process using mudstone gangue. For this, fractal theory, laser particle size analyzer, scanning electron microscope and other mesoscopic research methods were introduced. This study has several main factors, including the discharge port width in the jaw crushing stage, the grinding particle size, ball-to-powder ratio in the ball milling stage, and the fractal dimension changes of the gangue in different crushing stages. The results indicate that in the process of "jaw crushing-ball milling", gangue's particle size and shape fractal dimension values changed periodically. During the jaw crushing stage, the particle size fractal dimension increases with the width of the discharge opening, ranging from 1.85 to 1.92. The value of the shape fractal dimension varies from 2.65 to 2.84. Ball milling causes the fractal dimension value of gangue particle size to increase with time before agglomeration and decrease after agglomeration. By comparing different in-grinding particle sizes and ball-to-powder ratio, it is found that the fractal dimension value of gangue particle size decreases with the increase of in-grinding particle size and increases with the increase of ball-to-powder ratio. The final gangue's particle size fractal dimension value is concentrated between 2.5 and 2.8. The fractal dimension of particle shape increases with the increase of the grinding particle size, and decreases with the increase of ball-to-powder ratio. A ball-to-powder ratio greater than 6 gradually reduces its influence on fractal dimensions, and the final shape dimension lies between 1.06 and 1.16. In addition, the increase/decrease range of particle size and shape fractal dimension decreases with the increase of ball milling time, which is also consistent with the grinding kinetics theory. As a result of the changes in particle size and shape fractal dimensions, parameters such as jaw crusher discharge port width, grinding particle size, and ball-to-powder ratio are calculated to provide a theoretical basis for the entire crushing process in the "jaw crusher-ball milling" crushing process.

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Improved optical properties of phosphors-in-glass through the optimal size distribution of glass powder.

White-light diodes (WLEDs) are widely used in high-brightness applications owing to their outstanding advantages. However, current methods for preparing commercial WLEDs significantly deteriorate their optical properties and limit their use in high-power applications. To address this, inorganic materials, such as phosphor-in-glass (PiG), have been recently investigated as practical alternatives. In this study, a series of high-efficiency white-emitting PiG samples were prepared by mixing silicate glass powders with different particle size distributions and different concentrations of Y3Al5O12:Ce3+ (YAG:Ce3+) phosphors. The microstructure, transmittance, and photoluminescence properties of PiG were investigated. When the glass powder with the particle size ranges of 75-150 and 30-48 μm were mixed, at a ratio of 94 : 6, a silicate glass with a thickness of 0.8 mm and a maximum transmittance of 75% in the visible range was obtained. Under excitation with a 450 nm blue-light laser diode, PiG produced white light with a total luminescence efficiency of 194.64 lm W-1 and a total luminous flux of 623.9 lm. These results demonstrate that the optical performance of PiG can be effectively adjusted by adjusting the particle size distribution of silicate glass powder and the mixing concentration of the YAG:Ce3+ phosphor, thereby providing a tuning pathway for smart white-light devices.

Эволюция состава и морфологии порошка сплава Ti – 18 Zr – 15 Nb в процессе гидридно-кальциевого синтеза

Medical β-alloys of the Ti – Zr – Nb system are promising materials for creating bone implants that do not contain metals toxic to the human body. Powder metallurgy makes it possible to create porous structures based on this class of materials, thereby improving the osseointegration of bone tissues. However, the shape and size of the pores in an implant depend on the size and morphology of the initial powder. In light of this, the effect of the temperature and duration of calcium-hydride synthesis on the phase composition and morphology of the Ti – 18 Zr – 15 Nb (at. %) powder is studied in the current research. It has been established that with an increase in the duration and temperature of synthesis, the average size of powder particles increases, and the powder morphology and particle size distribution law change due to the formation of agglomerates. It has also been shown that during the formation of the β-solid solution, the synthesis process occurs in three stages. The first stage is governed by reduction reactions on the contact surface “oxide – liquid calcium”. The third stage is controlled by solid solution heterodiffusion. At the second stage, the synthesis process combines both mechanisms.

Recyclability of low-density polyethylene water sachet film into powder and its suitability for polyethylene-wood composite

Low density polyethylene (LDPE) based water sachet films were recycled into polymer powder by thermochemical treatment. Varying weights of sachet films were dissolved in automotive gas oil (AGO) at elevated temperature, followed by quenching in an ice-bath stainless steel container to determine optimum powder yield and particle size distribution. Sieve analysis of powder was carried out into different particle sizes and consequently to eliminate lumps. The polymer powder was subsequently mixed with maleic anhydride treated African mahogany wood dust (WD), in ratios 80:20, 70:30 and 60:40 wt%, and compacted by hot pressing to produce composite samples. Performance evaluation was carried out on the composite using tensile, flexural and impact energy testing techniques. Water absorption test was also carried out to determine hydrophilicity of the composite. The mass of powder yield from thermochemical treatment was about twice the amount of sachet films. Film dissolution of 100 mg/L of AGO gave optimal powder yield and size distribution with minimal lumps. Performance tests showed that, tensile and flexural strength, and impact energy of composites decreased with increase in the weight percent of wood dust. The water absorption test also revealed increased hydrophilicity of the composite with wood dust ratio.

Influence of Process Parameters and Particle Size Distribution on Mechanical Properties of Tablets

AbstractThe influence of the particle size distribution of maltodextrin powders with a dextrose equivalent level of 29 as well as two tableting process variables, namely the compression pressure and the dwell time, on the tensile strength, porosity, and pore size distribution of the final tablet was studied. The mechanical strength and porosity of the tablets are assessed in relation to the powder and process parameters. Regarding the process parameter, it was show that the compaction pressure clearly has a more pronounced influence on the tablet porosity and mechanical strength compared to the influence of the dwell time in the range of the study. As a result, the study offers a better understanding of how the properties of a tablet are influenced by the inter‐correlation of powder characteristics and tableting parameters. Therefore, the shelf‐life studies and tablet downstream processing as well as drug product development will benefit greatly from this work.

Characterization of Virgin, Re-used, and Oxygen-reduced Copper Powders processed by the Plasma Spheroidization Process

Fabrication of parts with high mechanical properties heavily depend on the quality of powder deployed in the fabrication process. Copper powder in three different powder types were spheroidized using radio-frequency inductively coupled plasma (ICP) spheroidization process (TekSphero-15 system). The characterized powders include virgin powder as purchased from the powder manufacturer, powder used in electron beam powder bed fusion (EB-PBF) process, and reconditioned powder, which was used powder that underwent an oxygen-reduction treatment. The goal of spheroidizing these powder types was to evaluate the change in powder morphology, the possibility of enhancing the powder properties back to their as-received conditions, and assess oxygen reduction of the powder lots given their initial oxygen contents. Also, to investigate the impact of re-spheroidization on powder properties, the second round of spheroidization was performed on the already used-spheroidized powder. The impact of powder type on powder sphericity and particle size distribution was evaluated using the image analysis of scanning electron microscope (SEM) micrographs and laser diffraction, respectively. The spheroidized powder showed higher sphericity and more uniform particle size distribution overall. Depending on the powder collection bin, second round of spheroidization affected the powder sphericity differently. The possibility of deploying the plasma spheroidization process as an alternative oxygen-reduction technique was also investigated through tracking the powders’ oxygen content using inert gas fusion method before and after the spheroidization. The plasma spheroidized powder showed less oxygen content than the hydrogen-treated powder. The second round of spheroidization caused no change in oxygen content. The correlation between oxygen-reduction and created cracks was discussed and compared between plasma spheroidization and hydrogen-treatment. The plasma spheroidization process created a powder with higher sphericity, uniform particle size, and less oxygen content.

Effect of powder particle size distribution on the surface finish of components manufactured by laser powder bed fusion

One of the key aspects of the laser powder bed fusion (L-PBF) process is the quality of the raw powder since it affects the final properties of the manufactured parts. In this study, 13 batches of Inconel® 718 powder were analysed, all of them being specially designed for L-PBF technology and meeting similar requirements but coming from different suppliers. Therefore, these batches have certain differences in their characteristics, including the particle size distribution (PSD). This study presents the relationship between the PSD of each batch and the surface roughness obtained in the manufactured parts. For the roughness study, Sa and Sz parameters are presented; in addition, the size and frequency of the particles adhered to the surface were quantified, and an autocorrelation analysis was carried out. Furthermore, after this analysis, the parts were sandblasted in order to repeat the same analysis after removing the adhered particles from the surface. This work points to the fact that the particles adhered to the surface are the smallest particles in the powder batch, and their size affects the roughness of the final part. This means that the surface roughness is strongly related to the fraction of smaller particles within the PSD of the batch, while there is no relationship between the surface roughness and the larger particles.

Understanding the structural phase state of bulk amorphous/crystalline alloys obtained from Zr35Ti30Be27,5Cu7,5 powder

The paper describes a method for obtaining Ti- and Zr-base near-eutectic alloys in the form of powders with a high degree of sphericity and a narrow size distribution of powder particles. Thus, a Zr35Ti30Be27,5Сu7,5 alloy powder with a particle sphericity of more than 97% and a particle size distribution of 63–100 μm was produced using the method of plasma spheroidization of fragmented powders obtained by grinding amorphous rapid-quenched strips. The final state of spherical particles has an X-ray amorphous structure, as indicated by a broad halo of scattered intensity typical of amorphous materials. An even distribution of chemical elements across the particle section could be observed. Bulk samples were made using the method of spark plasma sintering and applying varying parameters of temperature and dwelling time. The authors looked at the microstructure and microhardness of the bulk samples and carried out an X-ray phase analysis. The samples were found to have an X-ray amorphous structure during spark plasma sintering in the temperature range of 320 to 340 оC. However, at the temperatures of 320–325 оC, the resulting samples have a high internal porosity, which cannot be fixed with a pressure rise. The greatest compaction is achieved at the temperatures of 335 to 340 оC. By varying the dwelling time, the authors determined the optimal regime for producing bulk amorphous alloys: sintering at 340 оC and the pressure of 50 MPa, dwelling for 15 min followed by cooling at the rate of 80 оC/min. The samples produced in the above conditions have no visible porosity, and their microhardness is closest to that registered in cast samples.Contributors to this research include O. N. Sevryukov, Associate Professor, Candidate of Technical Sciences; P. V. Morokhov, Lead Engineer; P. S. Dzhumaev, Associate Professor, Candidate of Technical Sciences; I. V. Kozlov, Engineer; V. V. Mikhalchik, Senior Lecturer, Candidate of Technical Sciences; D. S. Gorbunov, Senior Lab Assistant (National Research Nuclear University MEPhI); A. A. Fadeev, Research Fellow; I. D. Zavertyaev, Junior Researcher (Baikov Institute of Metallurgy and Materials Science at the Russian Academy of Sciences).

Correlation between particle size distribution and explosion intensity of aluminum powder

To successfully reduce the occurrence of aluminum powder explosion accidents, this study uses a statistical analysis approach to examine the relation between 14 particle size parameters (D10–D90, D3,2, D4,3, σD, PSS, and SSA) and 5 explosion intensity parameters (Pmax, (dP/dt)max, Kst, t1 min, and t2 min). Note that D10–D90 represent the 10th–90th percentiles of particle size distribution, respectively, unit: μm; D3,2 is the average diameter of surface area momentum, unit: μm; D4,3 represents the average diameter of volume momentum, unit: μm; σD represents the particle size polydispersity; PSS is the particle size span, unit: μm; and SSA is the specific surface area, unit: m2·kg−1; Pmax is the maximum explosion pressure, unit: MPa; (dP/dt)max is the maximum explosion pressure increase rate with time, unit: MPa·s−1; Kst is the explosion index, unit: MPa·m·s−1; t1 represents the time from the start of ignition to the time when the maximum pressure is attained in the 20-L explosion sphere cavity, unit:·s, t2 represents the time from the start of ignition to the time when the explosion pressure increase rate reaches the maximum value, unit:·s. The t1 min and t2 min represent the minimum value of t1 and t2, respectively, unit:·s. The stepwise regression method is used to screen the effective particle size parameters that can describe the effect of particle size distribution on the explosive intensity of aluminum powder. The results indicate that σD and PSS are not recommended to characterize the particle size distribution in examining the explosion intensity. In addition, among the particle size percentiles, D10, D20, and D30 have the strongest correlation with the explosion intensity parameters. SSA has a strong correlation with (dP/dt)max and Kst, and D3,2 has a strong correlation with Pmax and t2 min. The correlation of the small particle size percentiles D10 and D20 with Pmax as obtained by the stepwise regression method is statistically significant. Moreover, the correlations of SAA with (dP/dt)max and Kst; D10, D3,2, and D30 with t1 min; and D10 and SSA with t2 min are statistically significant. Therefore, it is advised to use particle size percentiles (D10–D30) and D3,2 to describe the particle size distribution when examining the explosion intensity. Furthermore, we should focus on the proportion of small-particle-size aluminum powder components (D10–D30).

Fabrication of robust SiC ceramic membrane filter with optimized flap for industrial coal-fired flue gas filtration

Silicon carbide (SiC) filter candles are particularly suitable for the purification of industrial coal-fired flue at high temperatures. However, the filters are prone to break due to the lack of bending strength, especially at the filter flap, which limits its application field and service life. In this work, the SiC filter candles with optimized flap for the removal of fly ash from the industrial coal-fired flue gas were presented. The bimodal particle size distribution of SiC powders were employed to prepare the SiC filter flap to increase the number of neck connections among the SiC particles. The bending strength of filter flap was enhanced from 18.0 MPa to 37.0 MPa while the gas permeability did not exhibit obvious decline. Besides, the SiC filter candles presented a good thermal shock resistance due to the similar coefficient of thermal expansion of SiC filter flap (5.6 × 10−6 /K, 300–450 °C) and pipe body (5.0 × 10−6 /K, 300–450 °C). When the dust-containing flue gas with high temperature (300–450 °C) passed through the SiC membrane filtration equipment, dust was removed efficiently, and downstream equipment were protected from blocking and fouling. When the surface velocity of flue gas was set at 0.8 m/min and the back flushing pressure was set at 0.6 MPa, the pressure drop was fairly stable with minor fluctuation from 2420 Pa to 2700 Pa. Meanwhile, the outlet dust concentration and filtration efficiency of coal-fired flue gas were below 5.0 mg/m3 and above 99.98 %, respectively. This work provided a robust and high-efficiency SiC filter for the purification of industrial flue gas containing submicron-sized solid particles.

Surface state change influence’s theoretical approach of pressed iron on hollow cathode discharge characteristics: first results of plasma heating reproducibility for sintering purposes

In this work first results of the plasma heating process reproducibility for sintering purposes of pressed iron powder sample was investigated analyzing changes on the current-voltage characteristics of pulsed direct current (dc) Ar + H2 hollow cathode discharges sequentially carried out. For this purpose, the temperature of a sample acting as central cathode was varied by changing the switched-on time (duty cycle) of the pulse, via plasma species bombardment (ions and fast neutrals), which typically occurs in both cathode cylindrical surfaces that constitute the annular (hollow cathode) glow discharge, and measured by a thermocouple inserted in the central cathode sample holder. After two sequential plasma heating experiments, the third one practically reproduced the measured plasma parameters evidenced in the second heating, and the respective heating curves as a function of the time have led to similar current-voltage characteristics suggesting the iron sample sintering in non-isothermal way. Principles comprising plasma-surface interface and metallurgical-physical-chemical reactions, powder surface aspects, thermodynamic properties, metallurgical transformation of the pressed sample, and hollow cathode discharge properties are presented and discussed. The main points considered in the present approach are related to plasma (oxygen-affected plasma ionization, high ionization and excitation rate, and the intense light radiation of the annular glow discharge), thermodynamics (oxidation-reduction reactions, electron work function, sintering driving force, and surface energy), and powder (particle size distribution, morphology, specific surface, and iron recrystallization). To the best of the author’s knowledge, it is the first time that it is brought to the light the changes on hollow cathode discharge characteristics while an iron sample acting as the central cathode of an annular glow discharge is subjected to distinct heating steps on the temperature range of 20 to ∼1250 °C, leading it to have its sintering initiated.