Papers by Keyword: Nanopowder

Abstract: The article presents the results of research on the development of technology for the production of functional-gradient coatings with high levels of adhesive strength and hardness, as well as with low porosity. The coating was successfully tested and recommended to protect the elements and components of precision engineering.

Abstract: In this study, high quality monodispersed nanocrystalline cupric oxide (CuO) nanopowder was prepared through novel sol-gel green synthesis method, assisted by sodium alginate (Na-ALG) as the green ionic exchange material. The morphology and structural properties of CuO nanopowders synthesized with and without the incorporation of extrusion dripping, at different Na-ALG solution concentrations and calcination temperatures, were studied using thermalgravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. Optimum synthesis conditions were identified, resulting in high-purity, monodispersed nanocrystalline CuO powder in the range of 9.92 – 12.4 nm, which could have a promising future in various applications.

Abstract: Electro discharge machining process experiences limitation due to the non-conductive nature of the workpiece material. However, researchers proposed assistive EDM technique to machine nonconductive materials in the past. These assistive techniques require a minimal thickness of 100 µm conductive coating on the workpiece surface which usually takes longer time to coat the surface using PVD (physical vapor deposition) method. In this paper, a new modified assistive EDM method has been proposed to machine nonconductive Aluminum Nitride ceramics successfully. A three layers coating was used that included silver coating, carbon tape and silver nano-powder on a non-conductive aluminium nitride. This coating aids in conducting EDM operation due to the availability of conductive particles. Apart from the decomposition of dielectric that facilitates carbon particles on top of conductive carbon layer, coating itself also contributes in conductive silver particles. Therefore, carbon as well as silver debris that remains on the ceramics surface aids in continuous spark generation which in turn creates alternative thermal load and thus removes materials.

Abstract: The paper presents a mathematical model and the elements of a computer program for calculation and visualization of solidification of the rotating molten iron of the working layer of the roll in the centrifugal machine. We established the dynamics of changes in supply rate of carbide nanopowder feeding on the surface of the molten metal, provided its uniform distribution along the solidifying layer of the cast iron. It is shown that the working layer of the iron cools sideways and more intensively from the side of the chill mould; the areas, which are located near it, are the first to reach the solidus and liquidus temperatures. During cooling the layer of the iron, a maximum of temperatures is observed at a distance of 25 – 30 mm from the protective flux contacting surface. It was established that for a uniform distribution of nanopowder in the solidifying layer of the iron its feeding supply rate needs to be proportional to the speed of the moving the front of particle penetration, which is defined by the solidification front. Powder feeding needs to start from the time concurrent with the start of moving the front of particle penetration into the metal and to finish when an opposite crystallization front begins to form from the side of the flux.

Abstract: Ultrafine SnO₂ is a new type of material, in the field of solar cells and semiconductors have a lot of use. To get different morphology and different properties of tin oxide powder material, making more applications in the field, the effect of the adjuvants on the properties of superfine SnO₂ powders were distigated. Through the analysis of experimental results, the conclusions are shown the stronger the alkalinity of the auxiliary agent, the larger the grain size of the obtained particles and the more uniform the particles. When the molar ratio of salt to alkali is more than 1: 4, the amount of alkali is gradually reduced, the particle size is small, the morphology is not uniform and easy to agglomerate. When the molar ratio of salt to alkali is 1: 4, the smaller particle size is shown, the appearance morphology is uneven. The longer the reaction time, the more complete the grain, the more uniform the morphology. Under the condition of SnCl₄ concentration of 0.05mol/L, reaction time is 4 days, salt and alkali molar ratio is 1: 4, holding temperature is 200°C, the auxiliary agent is NaOH, the size, shape and performance of synthesized SnO₂ are the better.

Abstract: Dispersed Y₂O₃-MgO nanopowder was synthesized by calcining the stearate. XRD, TG-DTA, FT-IR, BET and FE-SEM were employed to analyze The formation mechanism of the precursor and the Y₂O₃-MgO nanopowder. Pure and dispersed Y₂O₃-MgO nanopowder with an average particle size of 40 nm was produced by calcining the precursor at 600 °C. The particle size increases to about 70 nm with the increase of the calcination temperature to 700 °C. In the preparation of Y₂O₃-MgO from stearate, no water medium is involved, thus capillarity force and bridging of adjacent particles by hydrogen bonds can be avoided, resulting in good dispersion of the particles. The dispersed Y₂O₃-MgO nanopowder prepared in this work has potential application in infrared transparent ceramic materials.

Abstract: Nano-Si₃N₄ has been synthesized by the thermal plasma with silicon tetrachloride (SiCl₄) as the Si source, liquid ammonia (NH₃) as the N source, and silane (SiH₄) as the catalyst. And the prepared Nano-Si₃N₄was heat-treated atfour different temperatures of 1350°C, 1400°C, 1450°C, 1500°C. The as-prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The results showed that the particle size of the nano-Si₃N₄ powder was less than 100 nm and it was amorphous when the temperature below 1450°C. At 1500°C, the synthesized Si₃N₄ powder with the grain size of 10 nm was crystallized, and the α-phase Si₃N₄ reached more than 90%.

Abstract: A study on the refining of nickel sulfate solution from sulfuric acid leached solution of spent lithium ion battery and fabrication of nickel nanopowders from the nickel sulfate solution was investigated. the nickel sulfate solution with high purity (>99.9%) was refined by precipitation method and solvent extraction method. the nickel nanopowders were synthesized by liquid phase reduction method with hydrazine and sodium hydroxide. the purity of nickel sulfate solution and nickel nanopowders were measured by EDTA(ethylenediaminetetraacetic) titration method with ICP-OES(inductively coupled plasma optical emission spectrometer). morphology, particle size and crystal structure of the nickel nanopowder was observed using transmission electron microscopy and x-ray diffraction spectroscopy.

Abstract: The most promising application field of materials based on nano-sized Co₃O₄ is catalysis. The method of production is one of the factors, which greatly affects the catalytic activity of Co₃O₄ catalysts. The aim of this research is to study possibilities of a new promising extractive-pyrolytic method (EPM) for the production of Co₃O₄ nanopowders and silica- and ceria-supported Co₃O₄ nanocomposites. Solutions of cobalt hexanoate in hexanoic acid and trioctylammonium tetrachlorocobaltate in toluene preliminary produced by solvent extraction were used as precursors. The precursors’ thermal stability, phase composition, morphology and the magnetic properties of the final products of pyrolysis were studied. The performed investigations have shown that the mean size of the Co₃O₄ crystallites in the materials produced by the EPM varies from amorphous to 55 nm due to the production conditions.

Abstract: The problems of hydrogen energetic as well as a method of high pure hydrogen obtaining are presented in the paper. It was suggested to use the reaction of aluminium nanopowder with water, as the reaction proceeds with high rate even at ambient conditions (the rate of hydrogen emission reached 18 ml/(s∙g)) and high degree of conversion (up to 100 %). The unreasonableness of the replacement of aluminium nanopowder to coarse-grained powder in this reaction due to the low efficiency is shown in the article. As a solution for pure hydrogen obtaining, a phenomenon of self-heating of aluminum nanoparticles and the resulting hydrogen, as well as the effect of its high-temperature diffusion through the membrane of ultrahigh molecular weight polyethylene were used.