Papers by Keyword: Sphericity

Abstract: Concentrated solar power technology represents a novel approach to generating solar power, characterized by high solar radiation density and uninterrupted operation. To store thermal energy and extend system operating hours, concentrated solar power systems rely on thermal energy storage. Selecting the appropriate heat storage media is crucial for designing a cost-efficient and straightforward system capable of withstanding high processing conditions. Among many powder materials, bauxite powder stands out as alternatives to conventional molten salt for thermal storage media due to its widespread availability and suitability for operating conditions. Particle shape, particularly its sphericity, plays a vital role in efficiently packing particles which directly affects to heat transfer properties. To investigate this effect, three samples of particles with different shape were formed: spheres, ellipses, and cylinders using Discrete Element Method with equal volume and material properties, and only variation of their sphericity factors. The study focused on the analysis of the porosity of the packed bed of particles with different shapes and its influence on the packing structure properties. The analysis of local packing fraction revealed that elliptical and cylindrical particles samples exhibited reduced heap formation and a more uniform distribution along z direction during vertical packing. The coordination number and radial distribution function analyses for these non-spherical particles showed a greater number of contacts between particles and disordered distribution of particles due to mechanical interlocking of non-spherical particles. The results indicated that the deviation of sphericity has a positive impact on the denser packing of particles generated more contacts and higher local packing fraction.

Abstract: Spherical copper particles with diameter ranging from 120.6 to 437.0 μm were prepared by the pulsated orifice ejection method (termed “POEM”). These spherical copper particles exhibit a good spherical shape and a narrow size distribution, suggesting that the liquid copper can completely break the balance between the surface tension and the liquid static pressure in the crucible micropores and accurately control the volume of the droplets. Furthermore, the relationship between cooling rate and microstructures of spherical copper particles was carried out with a specific focus on different cooling atmosphere and particle diameter during the rapid solidification. The cooling rate of spherical copper particles is evaluated by a Newton’s cooling model. It is revealed that the cooling rate was depended on cooling medium and particle diameter. The cooling rate decreases and the grain size increases with the increase of particle diameter during the rapid solidification, while the grain boundary of same particle diameter with larger cooling rate in argon gas is smaller, while the grain boundary of particles with smaller cooling rate in helium gas is larger. When the particle diameter is larger than 100 μm, the cooling rate of the cooper droplet in argon gas achieves 1.0×104 K/s. Meanwhile, the cooling rate decreases rapidly when the particle diameter increased between 70.6 and 149.6 μm. It is an effective route for fabrication of high-quality spherical copper particles.

Abstract: Various sizes SiO₂ colloidal particles in the size range of 260-950 nm were synthesized by the stöber method by adjusting the amount of ammonia from 9.0 ml to 3.0 ml while keeping 20.0 ml tetraethyl orthosilicate (TEOS), 125.0 ml ethanol, 6.0 ml ammonia and 18.0 ml distilled water fixed. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the crystallinity and morphology of the synthesized SiO₂ colloidal particles; the XRD result show that the SiO₂ colloidal particles are amorphous at room temperature; the SEM results demonstrated that the amount of ammonia could have significant effects on the size, size distribution and sphericity of the SiO₂ colloidal particles. SiO₂ colloidal particles were resulted with good monodispersity when the amount of ammonia was in the range of 6.0-90 ml, while SiO₂ colloidal particles with double size distribution were obtained when the range is 3.0-4.5 ml; on the other hand, SiO₂ spheres were resulted with good sphericity when the ammonia is in the range of 6.0-7.5 ml.

Abstract: Basic oxygen furnace slag (BOFS) , a mass supplementary cementitious materials, can be used as an active additive in building materials. The work present the result of granule morphology of two kinds of BOFS powder, cooled by water quenching (BOFS-W) and air splashing method(BOFS-A). Micrographs of two kinds of BOFS powder were observed with a scan electron microscope (SEM), then, length of major axis and minor axis of two-dimension projective outline of every granule in these SEM micrographs was measured manually and their ratio (RLB) was used to represent the granule sphericity. Each BOFS powder was divided into 6 parts with different granularity range. By means of measurement and statistical analysis, the average RLB value of granules with different granularity grade was obtained and the relation between size and sphericity of granule was explored. Result showed that BOFS-W is superior to BOFS-A in sphericity of granule. According to different granularity grade, statistical average values of RLB of BOFS-W and BOFS-A range 1.422-1.496 and 1.490-1.647, respectively. The difference of BOFS-W and BOFS-A on granule sphericity mainly is reflected in coarse granule.

Abstract: The objective of the present study is to investigate the engineering properties of paddy (One-thousand-one) grown in the coastal region of Odisha (India). The average length, width and thickness of paddy are measured as 8.80 mm, 2.65 mm and 1.91 mm respectively at moisture content of 28% (wb). The mean bulk density and true density of the particular variety of paddy are measured to be 0.61 g/cc and 1.47 g/cc. Properties like equivalent diameter, sphericity, grain volume, grain surface area, aspect ratio and porosity are calculated to be 3.58 mm, 0.40, 24.00 mm³, 35.66 mm², 0.30, 58.24% respectively. The angle of repose and angle of friction of the paddy grains are determined to be 37.73o and 0.43o, 0.25o, 0.30o with plywood, glass and galvanized iron respectively. These engineering properties are useful in design of forced convection dryer for the drying and processing of paddy.

Abstract: Definition and studies on the shape of various bodies are an interdisciplinary issue, raising wide interest among scientists. In geology and geotechnics the studies refer to features related to the shape of soil and rock particles, especially of those used for practical purposes. Due to the complex shape of particles, its three components have been distinguished: sphericity, angularity and surface microtexture. Sphericity usually determines the degree of similarity of a given particle to a sphere, whereas defined as a form refers to the general shape of the particle [3]. Particle shape and parameters that characterise it have not been unequivocally defined and normalised, resulting in a large number of definitions and ways of their determination. An extensive paper presenting the definitions used to describe shape parameters has been presented by Szerakowska [13]. This paper is focused on the comparison of analytical methods and an attempt to select the most optimal method for determining sphericity of particles in construction and road aggregates.

Abstract: The process of drum granulation is forming agglomerate by infiltrating liquid or binder into solid fine powder to produce bond force. Seed particles present different shapes features in granulation process. Different shapes of particles will have different movement trajectory and attitude under the condition of different location or rotational speed in the cylinder. The motion pose of different shape particles are analyzed by the simulation method using discrete element method, this way is better for us to control the time of powder in different drum position and frequency of adding powders per time. Research provides the theoretical basis on regulatory means and control parameters for adding powders and guarantee the production efficiency.

Abstract: A new fracture ceramic proppant was prepared using the low-cost raw bauxite mineral as raw material, by adding the auxiliary material such as potash feldspar, manganese powder and nanocalcium carbonate. The obtained proppants were characterized by XRD and SEM. The crushing rate, particle size, sphericity and roundness of the products were satisfied the recommendation in the standard of the American Petroleum Institute APIR-60.

Abstract: In this study, the novel finishing method of the Micro Lens Array mold is proposed. This method combines the cutting by a ball-endmill and the finishing by sphere indentation. In the previous step, U-shape grooves intersected at right angle are machined by a ball-endmill. In the following step, the ball tool indents at the intersection between U-shape grooves, consequently, the aiming lens form and the aiming surface roughness are obtained. From the results of the manufacturing experiments of the MLA mold by this method, the following are made clear : The proposed method is effective to suppress the deformation of neighboring lens forms caused by following indentation. The improvement effect of sphere indentation on the finished surface roughness is remarkable in the early stage of indentation. The transcribing deviations are 12μm or less in comparison between the radius of lens form and the ideal value regardless of radii in grooves previously cut. In case of the indentation of neighboring four (2 × 2) lenses, the deviation reduces down to 3μm.

Abstract: A newly developed practical sphericity measurement system by means of stitching interferometry is described in this paper. Spheres are widely used in industry. In particular, spheres with stem are usually used in metrological applications such as reference sphere for Coordinate Measuring Machines. It is common to calibrate form of spheres with tactile roundness measurement, however a comprehensive form measurement is desired for evolving high precision applications. The developed system consists of commercial base Fizeau type interferometer to capture partial surface areas of sphere and five axes stages to handle sphere with stem. Hence the system is very suitable for measurement of such stemmed spheres. This system yields three dimensional form maps of stitched sphere and peak to valley sphericity. Standard deviation of sphericity value yielded using this system is less than 5 nm in 8 times repetition. Finally, an equatorial profile clipped from stitched sphere shows good agreement with a result of tactile roundness measuring method within 10 nm typically.