Papers by Keyword: Fine Powder

Abstract: The Harmonic Structure [1] is a novel design concept that facilitates the engineering of metallic materials to achieve enhanced mechanical performance. The Harmonic Structure is composed of soft, coarse-grained regions, designated as the Core, which are surrounded in three dimensions by an interconnected network of hard, ultra-fine grain regions, referred to as the Shell. The interaction in these core/shell regions produces a synergistic effect during plastic deformation, resulting in superior mechanical properties that are of great significance. The distinctive network configuration of the Harmonic Structure enhances the dislocation density within the coarse-grain regions in contact with the interface through stress partitioning, thereby accelerating the work hardening rate and consequently enhancing the strength. This phenomenon is referred to as Hetero Deformation Induced (HDI) strengthening [2]. The fabrication of HS material is achieved through the application of mechanical milling (MM) to the powder, which results in the formation of a deformed layer on the surface of the powder and the creation of bimodal structured particles. However, a notable constraint of the MM process is its extended time requirement to attain the desired bimodal structure. In contrast, the bi-modal milling (BiM) technique involves the controlled mechanical milling of coarse and fine powders in conjunction with each other, with the objective of forming a layer of fine powders of a specified thickness over the coarse particles. The most advantageous aspect of bi-modal milling (BiM) is not only its reduced processing time, but also its superior ability to control the thickness of the surface deformation layer.

Abstract: The article is devoted to the description of a method for producing electrolytic copper powder with an average particle size of 3 to 10 μm. In order to increase the proportion of the finely dispersed fraction during the electrolysis process, the composition of the electrolyte was changed. In particular, the content of chloride ions was increased from 6 to 53 mg/dm³. After the growth of the powder in industrial baths, its subsequent drying and sieving on vibrating screens, samples were obtained with a fraction of 5 μm content in the range from 3 to 38 %. Additionally, air classification of powders was carried out at various speeds of the classifier rotor from 800 to 2000 rpm. Based on the results of the study, the optimal ranges of the specific surface area and the size of the initial powder particles before classification, as well as the composition of the electrolyte and the operating modes of the classifier, were determined.

Abstract: The article lays out the findings aimed to develop the fine silver powder production technique for electronics industry by selecting the variable parameters whereby a number of powder grades can be produced in the existing production environment (JSC “Uralelektromed”, Russia). The tests for significance of the parameters of silver recovery by ascorbic acid such as pH level of nitrate silver solution, dispersant flow rate, initial concentration of silver, mixing rate and solution temperature made it possible to choose optimum conditions to produce powders of 0.8-6.3 μm in particle size, of 3.0-4.2 g/cm³ in tapped density and with the specific surface area of 2300-4300 cm²/g. Crystalline silver of 99.98 % purity served as a raw material for obtaining silver powders.

Abstract: Today, the development of aluminium industry is highly dynamic. Aluminium production rightly takes top positions in the global metal market. Unique properties of aluminium mean that it is widely used in various industries. The construction industry is no exception – here, aluminium is actively used as a gassing agent for production of steam-cured aerated concrete, which is produced by mixing Portland cement, sand, water and aluminium fine powder or aluminium paste. The main disadvantage of aluminium fine powder is its high degree of dusting: at certain air concentration levels, this becomes fire-and explosion-prone. This is the reason the producers add complex organic additives into their aluminium fine powder: to ensure lower dusting levels and produce an aluminium paste, which is safer to use. This work focuses on obtaining an aluminium paste with sufficient share of organic additives to ensure the efficient performance of aluminium paste as a gassing agent in the production of steam-cured aerated concrete. A number of tests were carried out on mixing aluminium fine powder with various organic additives (fatty additive; wetting agent and gassing kinetics stabiliser; dedusting agent) in different ratios. The paper analyses the quality of distribution of organic additives inside the finished product and studies the relevant gassing kinetics.

Abstract: End-of-life tyres and elastomer products are recognised by European Union as important valuable resource for circular economy. Current work introduces an analysis of devulcanised crumb rubber comminution technique by means of semi-industrial disintegrator DESI-15. For the estimation of grindability, the main kinematic parameter in the processing of materials was given the specific energy of treatment E_s in kWh/t. Grindability of devulcanised crumb rubber aggregates as a function of particle size of the specific energy of treatment was analysed. Classified devulcanised crumb rubber will be used as a component of composite materials for oil spills remediation and for design of composite materials for civil engineering applications.

Abstract: The proposed method is a dry separation tailings. A separator developed for separating the tailings of the quartz sand and iron-bearing components. The efficiency of separation of enrichment tails in the fluidized bed separator is shown. The use of mill tailings as components in the manufacture of building materials is practically confirmed by testing samples of fine-grained concrete and asphalt.

Abstract: Ha Tai railway passenger dedicated line is a national key project of the eleventh five-year plan. Its different from other construction of high-speed railway because there is many frozen soil over the place. The requirement of the subgrade material is higher.We proposed a idea that gradred broken stone mixed with cement and fine powder applied in the project.The compressive strength,splitting tensile strength and flexural strength were studied and analyzed through laboratory test.And regression analysis between compressive strength and flexural strength was made .According to the regression analysis,a power exponent function between flexural strength and compressive strength was got.Based on this,the corresponding relationship table was deduced,which can be used in practical projects.

Abstract: Polycrystalline ferrites powders samples: Ni_0.6Cu_0.4Fe₂O₄ were synthesized by using metal nitrates and freshly extracted egg white, all the samples were sintered at 500°C,520°C, 550°C, 580°C and 600°C for 3h,6h,9h, respectively. The better synthesis conditions were investigated by analyzed the effect of sintering temperature and soaking time on structural, grain size and magnetic properties using X-ray diffraction (XRD), laser grain size analyzer (LPSA) and vibrating sample magnetometer (VSM). From the above analysis, the better synthesis conditions is set two insulation work steps: First at 240°C for 1h, then heating to 440°C for 2h, finally sintering at between 520°C and 550°C for 6h.

Abstract: Ha Tai high speed rail is a high-speed railway in cold region of China. The design criteria is very strict. There is many frozen soil over cold region. The research how to reduce the amount of subgrade frost heaving over Ha Tai high speed rail is of great significance.We use a frost heave model to simulate the subgrade frost heaving in the paper.We research how the fine power content and water content influence the frost heave amount of graded crushed stone by contrast test.The result shows that the fine power content and the water content have great influence on the frost heave amount of graded crushed stone .The frost heave ratio increases with the fine powder content and the water content.

Abstract: BaTiO₃ precursor powders were synthesized by two types of pulse jet spray pyrolysis1000 and 2000 kcal/h typesusing an aqueous solution of metal salt. All as-prepared powders crystallized to the cubic and other phases. However, the powders almost reached the tetragonal phase through calcination at 900 °C in air for 2 h. The crystallinity of the powders obtained from 2000 kcal/h type pyrolysis was higher than those obtained from the 1000 kcal/h type. When Ba (NO₃)₂ was used, nanoparticle formation at an average particle size of approximately 150 nm, with a narrow size distribution, was observed. The relative density of the sintered body was 87 %. The relative dielectric constant of the BaTiO₃ body was 1450, and its tanδ value was 0.017 at room temperature.