Particle Size Distribution Of Powder Research Articles

Synthesis and characterization of spherical Yb2SiO5 powder using solid-state diffusional reaction and spray dry process

Ytterbium monosilicate (Yb2SiO5) powder was successfully synthesized by the solid-state diffusional process at a low temperature (1350 °C) to serve as an environmental barrier coating (EBC). The stabilization procedure of the synthesized powder in the spray drying process was also presented. The synthesized monosilicate powder was used as a starting material in the EBC development. Ytterbium monosilicate coating was applied on the SiC/C ceramic composite substrate using the conventional atmospheric plasma spray (APS) technique. XRD analysis of the synthesized powder after the spray drying process showed a complete reaction between silica (SiO2) nanoparticles and ytterbium oxide (Yb2O3), leading to the formation of Yb2SiO5 without any side-product. Powder morphology, the corresponding elemental analysis of the spray-dried powder, and the microstructure of monosilicate coatings on the SiC/C substrate were investigated by the scanning electron microscopy (SEM). The particle size distribution of the spherical powder was found to be in the range of 20–80 μm. The thickness of the Yb2SiO5 coating was also in the range of 60–70 μm.

SCRAP TIRE RUBBER-BASED AGGREGATE IN LIGHTWEIGHT CONCRETE

Reusing rubber particles from used tires is good for the environment and, moreover, the world's population is becoming progressively conscious that a very high demand for natural resources is unsustainable. As the concrete industry consumes high amounts of natural resources, both for clinkering and gravel aggregate production, one must focus on its sustainability, considering environmental and economic issues. Therefore, reuse of waste tire rubber in concrete or in other composite materials is a logical solution for sustainable production of construction materials. Hence, the paper is aimed at the development and testing of lightweight concrete composed of a high volume of crushed waste tire rubber used as partial replacement of natural silica aggregate. In order to access the effect of incorporation waste tire rubber-based aggregate in concrete composition, reference concrete mix based on silica aggregate only is studied as well. The crushed waste tire rubber is characterized by its powder density, specific density, and particle size distribution. Specific attention is paid to thermal transport and storage properties of waste rubber that are examined in dependence on compaction time. For the developed lightweight concrete, mechanical, hygric, and thermal properties are tested. The tested lightweight concrete is found to be alternative and environmentally friendly construction material possessing improved thermal insulation function, interesting hygric parameters and sufficient mechanical resistance.

Reactive Shell Model for Boron Oxidation

An approach suitable for quantitative description of oxidation of porous powders with a complex particle morphology is developed and applied for a 95% pure boron powder. It is shown that boron particles, which are agglomerates of nanosized, partially fused primary particles, can be represented as spheres with reactive porous shells and impenetrable cores. The oxidation of such powders is assumed to occur volumetrically within the reactive shells. The shell thickness is obtained from simple experiments with the actual powders. To determine the thickness, thermo-gravimetric measurements are performed and processed for powders with different but overlapping particle size distributions. The processing uses measured powder particle size distributions to assign fractions of the powder mass gain to individual particle size bins. Selection of the appropriate initial reactive shell thickness makes it possible to ensure that particles of the same size present in samples with different size distributions oxidize in the same way. The specific powder studied here was successfully described with a reactive shell thickness of about 1.28 μm. Surface area measurements can be used to interpret the reactive shell as comprising packed spherical primary particles. For the powder used here, the radius of such primary particles is 80 nm. The proposed reactive shell model is shown to be valid as long as the thickness of boron oxide grown on the primary particles does not exceed 15 nm. The approach is useful for describing reactions leading to ignition of porous powders and of powders consisting of irregular aggregates in particular. It is also expected to be applicable to describe corrosion, catalyst aging, and other phenomena involving surface reactions for such powders.

Determining random packing density and equivalent packing size of superballs via binary mixtures with spheres

We propose a new approach to determining the random packing densities of superballs via binary mixtures with spheres. The main idea of the approach is to suppress order formations in non-spherical particle packings via the polydispersity of particle shapes, which avoids using order metrics. The packing density of superballs in a mixture can be segregated using a linear fitting method with the concept of equivalent packing size (or size ratio with unit spheres) which represents the effective size (or volume) of a non-spherical particle in a binary mixture with spheres. We systemically study the packing properties of binary mixtures consisting of spheres and superballs and obtain the equivalent packing sizes of superballs. Our results show that the equivalent packing size ratio always corresponds to the minimal packing density or specific volume (reciprocal of packing densities) variation, and is independent of the solid volume fraction. The specific volumes of mixtures with the equivalent packing size ratio are always the upper bound for all the solid volume fractions. The linear relationship between the specific volume and solid volume fraction is only observed in the mixtures with superballs of small surface shape parameters (shapes close to a sphere), which results from the highly disordered nature in the mixtures. Moreover, the ideal random packing densities of mono-sized superballs obtained via the linear fitting method are surprisingly close to those of the MDRPs (maximally dense random packings), further verifying that the MDRPs of non-spherical particles correspond to the ideal random packings whose degrees of order are at the same level with that of the random close packing of spheres. Our work leads to a better understanding towards the random and binary packings and sheds new light on the essence of the MDRP. Our work also guides the optimal particle size distributions of powders in chemical engineering process.

Online Rheometry Investigation of Flow/Slip Behavior of Powder Injection Molding Feedstocks.

Wall slip in the flow of powder injection molding (PIM) compounds can be the cause of unrealistically low viscosity values, and can lead to a failure of flow simulation approaches. Regardless of its importance, it has been considered only scarcely in the rheological models applied to PIM materials. In this paper, an online extrusion rheometer equipped with rectangular slit dies was used to evaluate the slip velocity of commercial as well as in-house-prepared PIM feedstocks based on metallic and ceramic powders at close-to-processing conditions. The tested slit dies varied in their dimensions and surface roughness. The wall-slip effect was quantified using the Mooney analysis of slip velocities. The smaller gap height (1 mm) supported the wall-slip effect. It was shown that both the binder composition and the powder characteristic affect slip velocity. Slip velocity can be reduced by tailoring a powder particle size distribution towards smaller particle fractions. The thickness of the polymer layer formed at the channel wall is higher for water-soluble feedstocks, while in the case of the catalytic polyacetal feedstocks the effect of surface roughness was manifested through lower viscosity at smooth surfaces.

Investigation of affecting parameters on slip casting of yttria-magnesia IR-transparent bodies

Slip casting of MgOY2O3 suspensions has been investigated in this research. For this purpose relatively pure commercial raw materials were used. The Taguchi experiment method was used for design of experiments and selection of suitable solvents and dispersants and theirs optimum values. Preparation of suspensions was done in two stages, according to particle size distributions of powders after different milling time and Taguchi results. The best suspensions were selected based on viscosity and solid load of suspensions. Green bodies were slip casted using the optimized suspensions in order to obtain the green bodies with maximum density and a homogeneous structure in term of porosity size distribution. Results showed that using from ethanol as solvent, an optimum dispersant level of 3%wt. TEA +1%wt. DEA with a constant TEA/DEA ratio of 3/1 and mean particle size of 155 nm (milling time of 48 h) was the best choice for preparing of optimum suspensions. The highest relative green density of 65.91% was obtained for a suspension containing 35 vol % of solid particles casted under 3MPa. The dense Y2O3MgO submicron composite samples were sintered by SPS technique at 1250 °C under 70MPa for 6 min with a density about 99.5%.

Effects of oxide particles on the microstructural and mechanical properties of W-Ni-WB composites

This study reports the effect of La2O3 addition on the microstructural and some mechanical properties of the W-Ni-WB composites. Composites having the compositions of W – 1 wt% Ni – 2 wt% WB and W – 1 wt% Ni – 2 wt% WB – x wt% La2O3 (x = 0.5 and 1) were fabricated by mechanical alloying (MA) and activated sintering methods. Phase and microstructural characterizations of the mechanical alloyed powders and sintered samples were carried out using X-ray diffractometer, scanning electron microscope (SEM), particle size analyzer and electron probe microanalyzer. Archimedes density and microhardness measurements, and sliding wear tests were also conducted on the sintered samples. The results showed that 1 wt% addition of La2O3 particles yields the lowest average particle size (290 nm) with a homogeneous particle size distribution of the composite powders. The sinterability and wear resistance of the composites, and the distribution of the particles throughout the sintered microstructure were also improved by adding oxide dispersoids into the W-Ni-WB composites. MA’d and sintered W – 1 wt% Ni – 2 wt% WB, – 1 wt% La2O3 composite had the relative density, average microhardness, and wear volume loss values of 96.97%, 6.02 GPa, and 115.8 µm3, respectively.

Comparative Analysis of Mobility and Compactability Indices for F240 Grinding Powders from Different Producers

Properties are determined for electrocorundum grinding grits and powders of different grain size from various producers. Powder particle size distribution and also rheological properties are determined by a static method; bulk and tapping densities, time for emergence from a funnel, natural repose angle, flow criteria, compactability and degree of tapping (indices of powder mobility and compactability), and some dynamic properties using a Revolution instrument. Scanning electron microscopy is used to study features of powder morphology. Results are used for comparative analysis of powders and conclusions are drawn.

Uncertainty of particle size measurements using dynamic image analysis

Metal powder particle size distribution (PSD) is a critical factor affecting powder layer density and uniformity in additive manufacturing processes. Among various existing measurement methods, dynamic image analysis (DIA) instruments are very appealing for measuring PSD. However, the ‘black box’ nature and complex measurement process inherent to DIA make quantification of uncertainty challenging. A method to establish DIA-based measurement uncertainty based on calibrated powder samples via a scanning electron microscope is described. Uncertainty analysis was performed taking into account uncertainties associated with the calibration of the sample as well as non-similarities of the calibrated sample and the measured sample.

Grinding Kinetics of Lotus Leaf Powder in a Stirred Media Mill

Abstract. Stirred media mills are invoked as high energy utilization equipment to prepare superfine particles with a narrow particle size distribution. In this study, the effects of the stirrer tip speed and the grinding media diameter on the particle size distribution of lotus leaf powder (LLP) were investigated. The stress intensity and stress number, which were determined by the stirrer tip speed and grinding media diameter, were applied to estimate the wet grinding kinetics of LLP. The stress conditions with the minimum specific energy consumption were a grinding media diameter of 1.4 mm and stirrer tip speed of 8.4 m s-1. Additionally, FT-IR measurements of the samples confirmed that the chemical structures of the active ingredients were not damaged with reduction in particle size, which indicated the mildness of the grinding process.HighlightsA stirred media mill was initially applied for preparing superfine lotus leaf powder.The stress conditions with the minimum specific energy consumption were determined.The active ingredients were not denatured during the grinding process. Keywords: Grinding kinetics, Lotus leaf, Stirred media mill, Stress intensity.

Simulation and experimental study on the air jet pulverization of TiC-containing slag

Process of “high temperature carbonization and low temperature chlorination”, which was considered to be one of the most promising technologies, could extracte more than 70% titanium from the furnace slag containing TiO2 10% - 30%. TiC-containing slag was the product of high temperature carbonization, and to meet the requirement of the following chlorination process, it needs to be crushed and grounded to a suitable size distribution. The air jet pulverization of TiC-containing slag was studied in this paper. On the one hand, By CFD numerical simulation, the distribution regularity of nozzle flow field about the main crushing equipment was obtained with different throat diameters and crushing gas pressures. On the other hand, the influences of nozzle throat diameter, crushing pressure, and collision angles on the particle size of the powder were studied by experiment. With the better parameters, the particle size distribution of the product powder was uniform.

Characterization of Ti6Al4V powders produced by different methods for selective electron beam melting

Three different types of Ti6Al4V powders produced by electrode induction melting gas atomization (EIGA), plasma rotating electrode process (PREP), and plasma atomization (PA) were compared from these aspects: particle size distribution, particle shape, and microstructure. Theywere characterized by particle size and shape analyzer, scanning electron microscope, and X-ray diffraction. The results show some benefits of using PA Ti6Al4V powder in selective electron beam melting. The particle size distribution of these Ti6Al4V powders were bimodal, and the PA Ti6Al4V powder had the narrowest particle size span. The roundness and elongation, the bluntness index of the most analyzed Ti6Al4V powders were greater than 80%. There were 52%, 81%, and 93% Ti6Al4V powders without satellite, respectively. These particle shape results indicate that EIGA, PRER, and PA Ti6Al4V powders have good sphericity and low content of satellites. The flowability of PA (20.55 s/50 g) is better than that of EIGA (24.80 s/50 g) and PREP (25.76 s/50 g). The microstructure of Ti6Al4V powders was composed of martensite ??.

A 3D discrete element-finite difference coupling model for predicting the effective thermal conductivity of metal powder beds

The effective thermal conductivity (ETC) of metal powder is a basic physical property that has an important role in industrial design for metallurgical, energy, chemical, and other types of application. To obtain this information, a numerical model based on the coupled discrete element-finite difference (DE-FD) method is proposed to precisely and efficiently predict the ETC of metal powders. A random packaged aluminum powder unit influenced by the effects of gravity is piled up concerning the particle size distribution of the real powder. Moreover, a sandwich structure model is proposed to simulate the thermal dynamic behavior during directional heat transfer. Based on the amount of heat passing through the system, the effective thermal conductivity was precisely calculated in an indirect way and the results of the simulation were consistent with corresponding experimental results. Relative error was within ±5%. Thus, the proposed numerical model may be useful in predicting the ETC of the different powder beds filed using various types of interstitial gas media within a wide range of temperatures.

Assessment of Raw Mineral Waste as Building Materials in Developing Countries

In many developing country’s mining exploitations are the main activities sources, and its exploitation is generating many mining wastes and environmental impacts. In order to use these waste, an innovative powder and aggregate were designed, aimed at providing alternative materials by cementitious supplementary materials and sand in Portland cement mortars. This paper investigates the use of raw mineral waste from some developing countries, namely Granite Residue (GR), from Niger, Mining Tailings (MT), from Madagascar, and red Volcanic Scoria (VS), from Cameroon as building materials. These raw materials were valorized as supplementary cementitious materials (GR powder, MS powder and VS powder) and as sand (GR sand and VS sand). GR sand and VS sand were used by 100% replacement of standard sand and GR powder, MS powder and VS powder were used by 5, 15, 25, or/and 35% cement replacement. Physical properties and mechanical properties of raw materials used and mortars obtained were investigated. The effects of these raw materials on properties of mortar mixes were studied and reported. Results show that, with sand from raw mineral waste materials, the compressive and flexural strengths of the produced mortar represented up than 70% and up than 85% respectively in comparison with mortar produce with siliceous standard sand. The reduction of strength of mortar with raw powder as ordinary Portland cement replacement is generally smaller than replacement ratio. Activity index of each raw powder is about 75% for ratio replacement of 5, 15 and 25%. Particle size distribution of raw powder and sand have an influence on the workability and mechanical properties of mortars. In conclusion, the use of raw mineral waste as a raw powder or as sand for mortar production presents an economical and environmental advantage for developing countries where mining exploitations are abundant.

Precision measurements of the particle size distribution of powder materials based on state primary standard for the units of disperse parameters of aerosols, suspensions and powder materials GET-163

In this article the problem of lack of specialized reference base and national standards in the sphere of additive technologies, particularly for the equipment and methods used in production, control of properties and the quality of powder materials is designated. The existing methods and instruments for measurement of particle size distribution and morphology of powders are considered and also the solution of this problem with use of the technical realization applied in the State primary standard for the units of disperse parameters of aerosols, suspensions and the powder materials GET-163 is proposed. Get-163 provides reproduction, storage and transmission of particle size units in aerosols, suspensions and powdery materials in the range from 0.001 to 2000 μm, counting concentration of particles in aerosols and suspensions in the range from 103 to 1012 m-3, mass concentration of aerosol particles in the range from 0.001 to 10,000 mg/m3, electrophoretic mobility of particles in the range from - 2⋅10-7 to + 2⋅10-7 m2/(V⋅s), zeta potential of particles in the range from -150 to + 150 mV.

Effect of powder characteristics on parts fabricated via binder jetting process

PurposeThis study aims to experimentally investigate the effect of the powder material characteristics on the qualities of the binder jetting additive manufacturing parts both before and after post processing (sintering).Design methodology/approachThree different types of the 316L stainless steel powder feedstock with various mean particle sizes and size distributions were studied. The influence of the powder particle size distributions and pore sizes on the powder bed packing densities and on the dynamics of the binder droplet-powder bed interactions were characterized. In addition, the surface roughness and densities of these parts both in the green state and after sintering were studied.FindingsThe results revealed the significant role of the powder feedstock characteristics on the liquid binder/powder bed interaction and consequently on the dimensional accuracies of the green parts. It was observed that the parts printed with the smaller mean particle sizes resulted in better surface finish and higher final densities after sintering. Furthermore, the hardness of the sintered parts produced with smaller powder particles exhibited higher values compared to the parts fabricated with the larger particles. On the other hand, larger particle sizes are advantageous for various green part qualities including the dimensional accuracies, green part densities and surface roughness.Originality/valueThis study establishes more comprehensive correlations between the powder feedstock characteristics and various quality criteria of the printed binder jetting components in both green and sintered states. These correlation are of critical importance in choosing the optimal process parameters for a given material system.

Planetary ball‐milling of AlON powder for highly transparent ceramics

AbstractA detailed investigation of planetary ball‐milling for coarsened AlON powder was carried out. Our results showed that the weight ratios of milling ball‐to‐powder, the revolution rate and the planetary ball‐milling time have significant impacts on the microscopic morphology, particle size distribution and average particle size of powder. The process and mechanism were analyzed, and the outcome of our study can be used to optimize the complicated planetary ball‐milling method by controlling the planetary ball‐milling time or adjusting the revolution rate at the final stage of planetary ball‐milling. Sequentially, using fine and uniform AlON powder by optimized planetary ball‐milling with an average particle size below 300 nm and excellent sintering properties, highly transparent AlON ceramic with an in‐line transmittance of 84% at 2000 nm was successfully prepared through pressureless sintering at 1880°C for 6 hours using the elaborative treated powder synthesized from carbothermal nitridation method.

Development of porous spray-dried inhalable particles using an organic solvent-free technique

A simple technique to produce spray-dried porous particles for inhalatory administration was developed. The particles were produced using water as solvent, Sodium Cromoglycate as model drug and ammonium bicarbonate as pore forming agent. A central composite design was employed to study the influence of the: pore-forming agent concentration (in the drug aqueous solution fed to the spray dryer) and air inlet temperature on: process yield and powder properties. The powder particle size distribution, moisture content, densities and estimated aerodynamic diameters were studied. Also, particles morphology, hygroscopicity, surface area, in vitro aerosolization properties, dissolution rate and stability were evaluated for some selected samples. In addition, a novel friability test was proposed for mechanical resistance evaluation of the porous materials.A pore forming agent concentration of 1.25% (w/w) and an air inlet temperature of 170 °C were the optimal process parameters to produce porous particles suitable for inhalatory administration. The process yield was high and it was demonstrated that the particles were free of ammonium bicarbonate. The porous powder, obtained by a simple and scalable technique, exhibited low tap density, good stability even at long storage periods (12 months), appropriate mechanical resistance, high initial dissolution rate and excellent aerosolization performance.

Expanding particle size distribution and morphology of aluminium-silicon powders for Laser Beam Melting by dry coating with silica nanoparticles

Current requirements for metal powder in Additive Manufacturing via Laser Beam Melting in powder bed (LBM) that ensure repeatably homogeneous thin layers can be spread and LBM products with high relative density ρrel can be built are high sphericity and particle size distributions (PSD) with limited share of fine particles. The most established LBM powder production method today is delicate and costly inert gas atomization. It yields highly spherical particles with continuous particle size distributions, but two thirds of the atomized powder exceed established LBM size ranges. A novel process route to improve flowability of cohesive metal powders is the coating of micro-sized powder particles with small amounts of nanoparticles. In this article, significant improvements in powder layer smoothness and ρrel of LBM samples are shown by statistical analysis of physical experiments on the example of Al-Si powders dry coated with 0.5 wt% nanoparticular fumed silica SiOx. This setup was chosen because Al is most prone to powder flowability issues in LBM and no new chemical elements are added to the alloy from dry coated SiOx. Particle shape is varied from spherical over ovoidal to irregular using powder atomized with Ar, N and air. Effects of variations of PSD and LBM parameters on ρrel, defect types, microstructure and hardness using powders with and without SiOx are investigated. Because ρrel are skewed towards 100%, ANOVA on ranks is the applicable statistical method. Since the principle of using nanoparticles as spacers between microparticles is based on geometry, it is transferrable to other material systems. This may help for example to increase ρrel of LBM metal matrix composites prepared by mechanical alloying as non-spherical particles with considerable amounts of fine particles. The use of larger percentages of atomized powders in LBM can increase resource efficiency.

Optimization of ball-to-powder weight ratio toward to highly transparent LaGdZr2O7 ceramics processing by solid reactive sintering

Highly transparent LaGdZr2O7 ceramics were fabricated by solid reactive sintering using the ball-milling mixed raw powder, and the transparency of samples can be significantly enhanced by optimizing the ball-to-powder weight ratio. The ratio effects on the evolution of morphology and particle size distribution of mixed powder, as well as the relative density and the in-line transmittance of obtained LaGdZr2O7 ceramics were investigated in detail. As the ratio increased above 24:1, the uniform and spherical-like particles became platy particles with bimodal particle size distribution (platy bimodal powder), while the relative density and transmittance of the LaGdZr2O7 ceramics were obviously improved. The highest in-line transmittance of 74.8% at 1100 nm, about 94% of the theoretical transmittance, can be achieved when milling ratio 27:1 was employed. Combined with the high refractive index (2.08 at 632.8 nm), high density (6.446 g/cm3) and high effective atomic number, the highly transparent LaGdZr2O7 ceramics obtained in this work can find potential applications in many areas such as optical lens and promising candidates for scintillator host, etc.