Apparent Density Of Powder Research Articles

Experimental Characterization and Computational Simulation of Powder Bed for Powder Bed Fusion Additive Manufacturing

The packing density of powder bed is one of the critical parameters affecting the quality of the final parts fabricated via powder bed fusion additive manufacturing. In this study the packing density of the first layer of the powder bed was experimentally estimated from the packing densities of recoated powder with different number of layers. It is found that the packing density of the first layer is much lower than the apparent density of powder and the macro-scale packing density increases as the number of recoated layer increases. Furthermore, recoating simulation using discrete element method (DEM) was conducted to investigate the deposition mechanism of the powder at the particulate-scale. The simulation results showed the packing density of powder bed increases as the number of recoated layer increases, similar to the experimental results. This is caused by the rearrangement of the powder in the powder bed stimulated by the supplied powder. Also, the packing density of the powder bed was not uniform in the thickness direction, and the top surface layer which affects the quality of manufactured parts had almost the same packing density as that of the first recoated layer independently of the number of recoated layers.

The influence of the carrier addition and spray drying temperatures on physicochemical properties of microencapsulated carrot juice powder

SummaryThe objective of this study was to determinate the influence of carrier addition and spray drying temperatures (160 or 200°C) on physicochemical properties of spray‐dried carrot juice powder. As carriers, maltodextrin and gum Arabic in different proportions were used. In powders were determined the following: moisture content, water activity, apparent density, size of particles, colour and carotenoids content. The content of carotenoids in powders prepared from solutions with juice to carrier ratio 2:3 was 324.3–406.6 mg/kg d.m., while in powders with a J:C = 3:2 values ranged from 576.7 to 637.7 mg/kg d.m. The highest content of carotenoids and the most yellow colour were observed in powders with 1:3 gum Arabic to maltodextrin ratio. Powders with the highest amount of gum Arabic have the highest diameter and the lowest water activity. High inlet temperature caused brighter colour of powders, higher dry matter content, lower water activity and apparent density of powders.

Preparation of Polypropylene Powder by Dissolution-Precipitation Method for Selective Laser Sintering

Polypropylene (PP) powder with spherical morphology and suitable particle size for selective laser sintering (SLS) was successfully produced by dissolution-precipitation method. The influence of preparation condition on properties of PP powder was investigated. The experimental results show that the optimal preparation conditions are as follows: dissolution temperature being about 166°C, pressure being about 0.7MPa, and the solid-to-solvent ratio being about 0.067g/ml. The prepared PP powder displayed a narrow size distribution with the mean size of about 42.7μm and the apparent density of powder about 0.40 g/cm3. The specimens produced by laser sintering of the PP powder showed smooth appearance and good dimensional accuracy. The tensile strength and impact strength of the sintered parts were 27.9MPa and 6.3KJ/m2, respectively, which are basically equal to the properties of the injection molded parts.

The Spherical Casting WC Powder and its Application in Laser Surface Alloying Treatment

The spherical casting WC powder is a kind of new potential wear-resistance ceramic material. In this paper, its chemical composition, surface morphology, microstructure, phase, microhardness and some powder characteristics were investigated, and then the powders were applied in laser surface alloying treatment on medium carbon steel. The results indicate that the spherical WC powder consists of (wt.%) 94.06 W, 4.03 C and 1.91 other elements including Fe, V, Cr and Nb. Most of powder particles have regular spherical shape and smooth surface, and the microstructure is acicular eutectic of WC and W2C, which leads to high microhardness of 2812 HV. The fluidity of powders is 5.97 s/50g, and the apparent density of powders is 10.1 g/cm3. The laser alloyed layer is characterized by dendritic primary phase, ledeburite microstructure and some residual WC particles. The laser surface alloying treatment with adding material of spherical casting WC powder can enhanc the abrasive wear resistance of medium carbon steel by over 200%.

The effect of reversing current deposition on the apparent density of electrolytic copper powder

The possibility of depositing copper powders with different apparent density by changing the shape of reversing current wave is shown. The morphology and crystallinity of powder particles can be varied considerably by changing shape of the reversing current wave and, hence, the apparent density of powders. The relation of apparent density with particle morphology and structure was illustrated.

スプレードライ造粒粉末を用いてパルス磁場中成形したＮｄ‐Ｆｅ‐Ｂ系焼結磁石の磁気特性

Nd-Fe-B alloy powder was granulated by a spray drying method using an organic binder in order to improve the powder flowability during feeding and compacting. In this experiment, whether or not the degree of magnetic orientation of primary particles in granulated powders is raised by applying high intensity pulsed magnetic field in compacting was studied, in order to improve magnetic properties of sintered magnets. It was found that the orientation of particles (remanences) was improved remarkably by applying high intensity pulsed magnetic field in initial process of compaction of granulated powders, so that magnetic properties of magnets are superior to those of magnets when applying only static magnetic field in compacting. The observation of granulated powders after applying magnetic field shows that granulated powders were destructed more easily by such high intensity pulsed field. The orientation of primary particles in granulated powders depends strongly on the apparent density of powders when applying pulsed field. It was very effective for improving magnetic properties of magnets using granulated powders to apply pulsed field when powders fed in die cavity are free for orientation. By means of controlling the binding strength of binder and timing of pulsed magnetic field, magnetic characteristics of magnets using granulated powders became almost equal to that of magnet using raw powder.

Surface area, mass fractal dimension, and apparent density of powders

We discuss the relationship between mass fractal dimension, Dm, and apparent density, ϱa, in powders. Experimental Dm values, derived from the particle size dependence of ϱa, are reported for glass, hydrated cement, montmorillonite clay, sepiolite clay, attapulgite clay, silica gel, alumina, and charcoal. All the values are very close to 3, in the particle size range ∼ 50 to ∼ 1500 μm. This suggests that the particle texture in most powders tends to be homogenous and Euclidean at sufficiently large length scales. An outcome of this is that the numerous surface fractal dimensions characterizing particle roughness, which were all determined from adsorption measurements assuming Dm = 3 [D. Avnir, D. Farin, and P. Pfeifer, Nature (London) 308, 261 (1984) and subsequent publications], are most probably correct, in the particle size range in which the surface area was measured.

Pressing characteristics of tungstenless KNT16 alloy powder

A tungstenless KNTI6 alloy powder and VK6, VKI5, and VK20 alloyt powders produced under industrial conditions were chosen for investigation. A comparison was made of the apparent densities of these powders and of the densities and strengths of compacts pressed from them under the same pressure. Apparent density was determined by the method described in [2, pp. 28-29]. The powders were compacted into cylindrical specimens of dimensions d = 12 and h = ii mm. The density of a compact was calculated as the ratio of its weight to its volume after removal from the die. The strength of a compact was assessed, as described in [2, p. 27], by its ability to withstand disintegration during tumbling in a screen barrel. As a strength indicator the ratio between the compact weights after and before tumbling, expressed in percent, was used. To study the effect of the use of a plasticizer, mechanical characteristics were determined for powder charges with and without rubber additions. The mixing of the powders with rubber was performed in accordance with processing instructions for the corresponding groups of alloys (the amount of rubber added to 1 kg of the KNTI6 alloy powder was twice that added to each of the WC-Co alloys). The relative apparent density of the KNTI6 alloy powder was found to be slightly less than that of the WC-Co alloys. This difference should be taken into account in the designing of new pressing tools: The die height and the pressing and ejection strokes should be increased by 10-15%. In spite of the difference in apparent density, the relative densities and hence coefficients of shrinkage of compacts from the KNTI6 and WC-Co alloy powders pressed under the same pressure were practically identical (Table i). Slight differences attributable to technological variations in properties among different batches of powders can easily be allowed for by varying the pressing pressure. Thus, for pressing tungsten and tungstenless alloys it is possible to use die sets calculated for the same extent of shrinkage. The strength of KNTI6 alloy compacts proved to be no different from that of WC-Co alloy compacts pressed under the same pressure. Unexpectedly, the plasticizer was found to have very little effect on the strength of KNTI6 alloy compacts: In the absence of the plasticizer the strength indicator of the tungstenless alloy was still very high, while that of WC--Co alloy compacts was close to zero. Together with determinations of pressing characteristics, an assessment was made of the technology of industrial production of parts in VKTI6 alloy from the point of view of accuracy of manufacture of cutting tips. Essentially, the assessment consisted in comparing the fields of scatter of tip dimensions with the allowance fields laid down by [3]. From each of five batches of KNTI6 alloy 12 parts were selected, and several of their parameters, including weight, were measured. The scatter of any dimension was determined as the difference between the extreme values of this dimension for the series of tips selected, referred to the

Friction in power rolling

Friction in the rolling of powders should be analyzed in conjunction with their compressibility. The mechanical component of the coefficient of friction (roll surface roughness) at the interface between a roll and a powder being densified (zone II) exerts the strongest influence on the gauge indicators of the compacted strip. Internal friction in powders cannot significantly affect the size of the densification zone, but has a marked effect on the uniformity of density distribution over the surface of the rolled strip. The effect of liquid lubricants on the gauge indicators of roll-compacted strip should be assessed by examining the opposed effects of two factors: An increase in external friction at the roll/powder interface (beginning of zone II) raises the gauge coefficient, while a decrease in the relative apparent density of powders lowers it.

Effect of electrolysis conditions on the dispersion and apparent density of nickel powder

1. A study was made of the effect of electrolyte composition and electrolysis conditions on the dispersion and apparent density of nickel powder obtained from sulphate-chloride electrolytes. By using the regularities established, it is possible to prepare powder metals of any required dispersion. 2. It is demonstrated that the most effective factors governing the dispersion and apparent density of the powder are the concentration of nickel ions in the solution, current density, and electrolyte temperature. 3. It was established that, with increasing electrolyte temperature, the dispersion and apparent density of the powder decrease. The decrease in the apparent density of the powder is due to the fact that the adsorption and passivating effect of the hydrolysis products of nickel sulphate result in the deposition of strongly dendritic particles. 4. Increasing the concentration of sodium chloride and decreasing the duration of growth of loose deposits on the cathode (periods of time between the powder removal operations) are instrumental in increasing the dispersion of the powder. Both these factors may be utilized for improving the technical and economic parameters of electrolysis.

粉末物質の一性質,割目の一特性,及びその地球物理學に於ける應用に就いて

For a vast dimension as that of the actual earth's crust, the effect of the gravity is very great as compared with the effect of strength of the material. Hence, the earth's crust may be represented by powder mass as a model in laboratory. In the present paper, the cohesion of powder mass was measured and it was found that they are about 0.4-0.02gr./cm2. Next the following similitude law of cracks was deduced where λ is the linear dimension of the fractured pieces, d the thickness of powder layer, ρ the apparent density of powder, g the acceleration due to gravity, Fs the cohesion of powder. This law was applied for geophysical problem, and it was concluded that the earth's crust has block structure. and its linear dimension was calculated as about 13km which is in good accordance with the observed value 10km.