Papers by Keyword: Composite Powder

Abstract: In order to improve the wear resistance of aluminum matrix composites and reduce the cost at the same time, the Al₂O₃/Al composite powder was prepared by hydrothermal method in this experiment, and the material properties of the Al₂O₃/Al metal matrix composite powder material were studied. It can be seen from the results that the encapsulation degree of Al₂O₃/Al-based composite powder material first increases and then decreases with the increase of ammonia concentration, and first increases and then decreases with the increase of PH value. The optimal molar ratio of salt and alkali is 1:1. Through the optimization of process parameters, the ratio of aluminum nitrate and ammonia water is obtained as: 1:1, the slurry stirring speed is 1500r/min, the stirring time is 10min, and the heating temperature is 200°C, the obtained composite powder is relatively uniform, has a larger specific surface area, and has better powder properties.

Abstract: On the one hand, cermet has the advantages of metal materials, and on the other hand, it maintains the excellent properties of ceramic materials, and is a very important new engineering material. In this paper, the alumina/aluminum cermet material composite powder was prepared by ball milling, and its densification properties were characterized and studied to provide reference for the preparation of high-performance cermet materials. When the ball milling time is more than 6h, the distribution of alumina particles around the aluminum powder is relatively uniform. The research shows that: with the extension of the ball milling time, the number of pinning of Al₂O₃ particles on the surface of the Al ball first increases and then decreases; The trend of decreasing; with the increase of ball-to-powder ratio, the distribution of Al₂O₃ particles on the surface of Al balls is more uniform. Considering its cost-effectiveness, it is more suitable to prepare pinned alumina/aluminum-ceramic composite powder under the conditions of ball milling speed of 360r/min, ball-to-material ratio of 2:1 and ball milling time of 12h. When the Al content gradually decreased, the density and hardness of the cermet material also decreased gradually. When the Al content gradually decreased, the density and hardness of the cermet material also decreased gradually. When Al accounts for 75% in the sample, the microstructure is dense and the hardness is higher. When the molding pressure is 20MPa, the unevenness of the surface of the material is greatly relieved, relatively flat, and the densification effect is better. When the sintering temperature is 800°C, the fired sample is very dense, and the particles have relatively high bonding strength, but a small amount of aluminum is precipitated on the surface of the sample, forming a silver-white spherical substance.

Abstract: Cold spray (CS) is a solid-state deposition technique of micron-sized metallic powder in an ultra-high velocity gas using a de Laval nozzle. CS is a unique deposition technique due to its use of relatively lower gas temperatures in comparison to other thermal processes. Consequently, high-temperature oxidation and phase transformations of deposited powders are largely restricted while the operating cost of CS is much lower than that of other thermal processes. Generally, the low pressure cold spray (LPCS) technique is used for the deposition of metallic powders on metallic substrates, while only a few studies of metallic particle deposition on ceramic substrates have been conducted, and it was found that the deposition of metallic powders on ceramic substrates was quite difficult. In this study, improved LPCS deposition of copper coatings on zirconia substrates was investigated. It is known that deposition of a metallic powder on a ceramic substrate is difficult due to the differences in material bonding and several properties of the two materials. These difficulties in LPCS deposition were solved using three different approaches, namely 1) use of copper and aluminum composite powders and 2) laser pre-treatment and 3) laser texturing of zirconia substrates. It was found that pure copper powder coatings on the as-received and various treated substrates were delaminated in the interface as expected. However, the deposition was improved for all substrates by using the copper and aluminum composite powder. While the laser pre-treated substrate was not effective for the deposition of the copper and aluminum composite powder, thick coatings were obtained for the deposition on the laser pre-treated with heat treatment substrate and the laser-textured substrate.

Abstract: Cermet is an important new engineering material that not only maintains the excellent properties of ceramic materials, but also has the advantages of metal materials. In this paper, the encapsulated alumina-aluminum composite powder was prepared by ball milling and characterized, which laid a foundation for the development of high properties cermet materials. Through the analysis of experimental results, the conclusions are shown when the ball milling time is greater than 3 h, the alumina particles are more evenly distributed around the aluminum powder. the ball milling for 6 h may have reached a limit of the mixing uniformity of the two powder, so the ball milling is determined 6 h as the better ball milling time. Under the ball milling condition of 50 r/min, the distribution of alumina particles around the aluminum powder is more uniform around the aluminum powder than the ball mill under 75 r/min, the ball milling speed is preferably 50 r/min. As the content of aluminum powder increases, the distribution of alumina in aluminum powder is large and uniform, and there is a small amount of pinning. It provides a package-like composite for the preparation of cermet with a wrapped structure and the thermal conduction mechanism of the controlled cermet.

Abstract: Both alumina and boron carbide have good hardness and strength, and are widely used in production and life, industrial manufacturing, and military defense. However, due to the insufficiency of research at this stage and the lack of technical means, it is difficult to prepare alumina-boron carbide composite powder with good coating and ultra high strength through large-scale batch production. Therefore, this experiment wants to obtain a relatively good performance of coated Al₂O₃/B₄C cermet by hydrothermal method through different experimental parameter ratios. Through the experimental results and analysis, the following conclusions are obtained. The most suitable concentration of aluminum nitrate is 0.1 mol/l. The low concentration affects the formation of alumina particles. The concentration is too high and prone to agglomeration. Through the optimization of hydrothermal synthesis concentration, a composite of Al₂O₃/B₄C composite with good nanoencapsulated structure was obtained. The composite powder was pure in composition and high in specific surface area, which lays a foundation for solving the low-temperature preparation of high-density boron carbide ceramics.

Abstract: YAG has many excellent features and therefore has a wide range of applications. Preparation and properties of YAG porous ceramics via the casting method is investigated. Through analysis and discussion, the following conclusions can be obtained. With the increase of the content of foaming agent, in the foaming process of the slurry, bubbles generated by the foaming agent and water are gradually increased, the more pores are left in the body after casting, and when the blowing agent is too much, excessive bubbles are generated, which can lead to a very low strength of the green body and can not be formed and operated later. As the ratio of water to material increases, the porosity of the porous material increases. This is because when the blowing agent is constant, the amount of water required for foaming is constant, and the amount of foam generated is also constant. When the content of foaming agent and the ratio of water to material is both 1, the porosity and compressive strength is better.

Abstract: The Al₂O₃/Al cermet composite powders were prepared via the ball milling method,which provide raw materials for preparing high performance cermet materials. The results show that the number of Al₂O₃ particles on the surface of Al particles increases first and then decreases with increasing the ball milling time and milling rotating speed. The number of Al₂O₃ particles on the surface of Al particles increases with increasing ball to powder mass ratio. The analysis of the ratio of performance to price shows that the better parameters for preparing the pinned Al₂O₃/Al cermet composite powders are as follows, the ball milling time 24h,the ball milling rotating speed 100 r/min and the ratio of ball to powder 1:2.

Abstract: Hollow silica spheres (HSS) are prepared via soft template method. The morphology, internal structure, phase composition, particle size distribution and porosity of HSSs are characterized. It is found that the amorphous HSSs with thin shell thickness and density of around 0.41 g/cm³ have good sphericity and are relatively uniform in size. Most importantly, the size of the synthesized spheres is controlled successfully via stirring rate, and the linear fitting equation is described as d₅₀ = -0.45 × R + 206. This research provides a facile way to produce HSS with low density which has promising application in many fields.

Abstract: In view of the physical process of the wood powder/PES composite powder material selective laser sintering forming ,this article establishes the plane moving Gaussian heat source as the input laser heat source model .Based on selective laser sintering wood powder/PES composite powder sintering theory and combined with thermal conductivity of composite powder, specific heat, density and other related theoretical analytical models .It establishes three dimensional finite element model of selective laser sintering process of wood powder/PES composite powder transient temperature field .The laser sintering simulation experiment of wood powder/PES composite powder under different laser power obtains temperature field distribution law of the wood powder/PES composite powder forming under different laser power distribution, and the influence of the forming parts forming quality of wood powder/PES composite powder materials caused by the temperature field. The simulation results also provide certain theoretical basis for the choice of laser power in the subsequent laser sintering experiment.

Abstract: The paper captures the effect of structure and the applicability of compaction models using the cold compaction of a TiH₂-SS316L composite powder prepared by high energy mechanical milling. The composite blend was cold pressed uniaxially to pressures of up to 1250MPa. The compressibility of the composite blend was evaluated by fitting the experimental data to the most commonly used compaction models of Heckel, the Kawakita-Lüdde, the Cooper-Eaton, the Ge, and the Panelli-Filho compaction equations. Among the models, the Kawakita-Lüdde and Cooper-Eaton models fitted the experimental data very well with a good correlation (the correlation coefficient greater than 0.99) throughout the entire pressure range under investigation. The nature and mechanisms responsible for the densification during cold compaction are discussed. The Heckel, Ge, Panelli-Filho, and Cooper-Eaton model analysis showed that the dominant compaction mechanisms for composite blend were rearrangement of particles followed by elastic and plastic deformation. The results are discussed by way of a comprehensive model intercomparison study of the cold compaction behaviour using existing models.