Papers by Keyword: Crucible

Abstract: The structures of sodium zirconate were studied in this research, which formed after the alkali fusion process. In this process, zircon is decomposed using sodium hydroxide (NaOH) at high temperatures to separate zirconium from impurities, resulting in high-purity zirconia which has potential as a dental material. The study aims to control the formation of Na₂ZrO₃ phase and to minimize the reactions between Zircon, NaOH, and crucible materials, such as porcelain, silicon carbide (SiC), and alumina to prevent contamination. To enhance reaction efficiency, a pre-treatment process was introduced, including wet milling and NaOH leaching. Then, the pre-treated zircon sand was reacted with NaOH in a 1 ZrSiO₄ : 6 NaOH molar ratio. Results showed color changes in the crucibles, indicating interactions between crucible materials and NaOH. But there is no change observed in alumina crucible which means that it is not reacted with either NaOH or ZrSiO₄. Different pre-treatment and crucible materials influenced the crystal size of Na₂ZrO₃ phase which give the lowest crystal size of 24.69 nm when using porcelain crucible. After the recovery process was finished high-purity full tetragonal zirconia phase is achieved which can be further processed as a artificial dental application. In artificial tooth application, pure zirconia with high strength is needed, thus controlling crystal and grain sizes is a crucial factor which affect the properties.

Abstract: Due to material and structural issues, fire-assaying crucibles used for analyzing precious metals in ores have encountered challenges related to poor thermal cycling in Ghana’s sub-Saharan region. This study aimed to enhance the crucibles by analyzing aluminosilicate minerals' multiphase development using X-ray diffraction and understanding the effects of composition determined by X-ray fluorescence on thermal behavior and water absorption observed through optical microscopy. The improved crucible design exhibited enhanced thermal cycling stability and lower permeability to the assay charge. Analysis showed that Fosu Clay (FC) demonstrated promise with a favorable Al₂O₃:SiO₂ ratio and low impurities; mullite was identified as the primary phase formed at high temperatures, with quartz and cristobalite also present. Introducing 6% CSM dopant to FC increased the mullite content while supporting the transformation from quartz to cristobalite. The optimal crucible sample included coarse and fine-doped grog with an FC-clay binder, demonstrating excellent thermal stability, adequate porosity, and water absorption. Adjusting the percentage of doped grog further increased mullite content while reducing silica content; this suggests that locally produced improved crucibles are feasible through sintering commercial clay with mullite doping and precise composition adjustments.

Abstract: The results of the development of the technology for growing super-large single crystals of refractory metals, which were developed at the E.O. Paton Electric Welding Institute of the NAS of Ukraine. Based on proven technology and acquired skills, a new generation of equipment was created that allows the growth of single crystals of refractory alloys in the form of bodies of rotation. Experiments were conducted on growing a single crystal of tungsten in the form of a hollow cylinder, from which it is possible to make such a product as a crucible. Technological parameters and energy regimes were established, which allowed for control of the thickness of the wall to be welded. As a result of the experiments, an ingot with a welded wall height of 68 mm, a thickness of 20–22 mm, and an outer diameter of 85 mm was grown. The structure of the obtained samples was studied.

Abstract: The present study considers various technological approaches to the processes of complex utilization of nickel slags with preliminary additional extraction of non-ferrous metals, iron, and ways of utilization of the obtained gangue. The valuable components are often produced from waste using the mineral acids or mixtures; the metals are extracted from acid solutions in a free form or in the form of compounds using electrochemical or chemical methods. Slag dumps have a heterogeneous structure and mineralization; the zone distribution of slag is clearly defined due to different cooling and solidification rates. The slag composition is mostly represented by dense low-porous varieties consisting of dark brown glass. The porous slag fragments are secondary. The third texture diversity in the composition of slag is represented by nodular and kidney-shaped particles. The diversity and size of the ore minerals is directly connected with the distribution of pores in slag. The major ways for utilization of nickel industrial waste are pyro-metallurgical and hydrometallurgical methods. In addition, each of the methods is usually preceded by the stage of mechanical preparation of the raw materials, where the techno-genic waste is crushed.

Abstract: Technological features of obtaining of tin films in a vacuum by liquid-phase target magnetron sputtering were reviewed. With high deposition rate the white color tin coating with amorphous structure is formed on the substrate. X-ray microanalysis of the obtained tin films showed the presence of micro-and nanoparticles of an impurity of the crucible material in the structure of the films. The use of the tantalum crucible with liquid-phase target magnetron sputtering with deposition rate of 3.2 μm / min allows obtaining ultra-pure, continuous, homogeneous tin film on a stationary substrate without impurity material of the crucible.

Abstract: Y₂O₃ doped SrZrO₃(SZY) powders were prepared according to a solid-state reaction method, which the raw materials contains SrCO₃, ZrO₂ and doped with 5 mol% Y₂O₃. And then the powders were used to make a green crucible shape by cold isostatic pressing. After that, the crucible was used to melt with TiNi alloy in the vacuum induction furnace with biscuit firing temperature of 900°C, and sintering temperature of 1750°C. The x-ray diffraction analysis (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to analysis the characterization of the Y₂O₃ doped SrZrO₃ power; microstructure of the crucible at different holding time under the 1750°C and the interfacial reaction between the crucible and the TiNi alloy. The results showed that the powders of Y₂O₃ doped SrZrO₃ were synthesized at 1200°C, and there was no obvious reaction layer and elements diffusion between the crucible and TiNi alloy. The ingot is easy to separate from the crucible after smelting.

Abstract: Aluminum nitride (AlN) bulk crystals, approximately 50.8mm in diameter and up to 5mm thickness, were grown by a physical vapor transport (PVT) method in a tantalum crucible. To investigate the effect of crucible materials, various crucible materials, a graphite and TaC-coated graphite and tantalum crucible were used for the AlN growth. XRD pattern of AlN crystal grown on SiC seed in the Ta-crucible exhibited only (00l) peaks, indicating that AlN single crystal was successfully grown on SiC seed. The interface structure between AlN and SiC crystals was observed by a high resolution TEM.

Abstract: Hexagonal Boron Nitride (h-BN) shows remarkable physical properties, including high thermal stability, low density, low metals wettability, high corrosion resistance and microwave transparency. These features make it extremely interesting for several industrial applications such as furnaces manufacturing and metallurgy industry. Usually, h-BN parts are sintered by expensive high-temperature/high-pressure processes, strongly limiting their size. Here we present a new, cost-effective technique to obtain materials with high h-BN content and large dimensions, suitable for wide-scale industrial applications. Using h-BN and silicon powders as raw materials, reaction-bonded Si₃N₄/BN composites were obtained by complete nitriding of silicon. Two shaping techniques were exploited: slip casting and uniaxial compression molding using a thermosetting resin (in this case also Silicon Carbide was obtained), leading to materials with different properties. Both large (plates with diameter up to 400mm) and/or complexly-shaped objects (i.e. crucibles) were produced. Such materials were prepared using a Gas Pressure Sintering oven with different process parameters. The as-prepared samples were characterized and tested in a real application, as parts of liquid-silicon infiltration crucibles.

Abstract: The thermal stress field in the polysilicon was simulated and comparatively analyzed at different shapes of crucibes which have different types of a flat, a inverted-conical and concave bottom by COMSOL Multiphysics version 4.3a. The results indicated that: within the flat-bottomed crucible ,the isotherm in the crystal was slightly convex and the area of the maximum thermal stress was distributed in the bottom of the crystal edge and near the top of crystal edge; within the inverted-cone crucible, the isotherm in the crystal was straight and the area of the maximum thermal stress was only distributed in the bottom of the crystal edge; within the bottom of the concave crucible, the isotherm in the crystal was slightly concave and the area of the maximum thermal stress distributed in the bottom of the crystal edge was larger than that of the crystal within the first two kinds of crucibles. To sum up, the inverted-cone crucibe was beneficial to reduce the thermal stress distribution in the polysilicon which could provide theoretical guidance for improving the production process of the polysilicon.

Abstract: This work presents recent advances in the characterisation of carrier recombination and impurities at Fraunhofer ISE. The role of iron contamination during crystallisation is analysed in more detail. Numerical simulations and comparisons to experimental data are presented which demonstrate the impact of iron from the crucible and crucible coating and show the in-diffusion of iron into the silicon melt as well as into the solid silicon during crystal cooling. Measurements of spatially resolved carrier lifetime and interstitial iron concentration on wafers after phosphorus diffusion gettering are used as input for cell efficiency modelling which reveals the specific and quantitative role of iron on cell parameters in multicrystalline silicon. A new photoluminescence based method is presented which quantitatively determines the interstitial iron concentration in finished solar cells. We finally present advances in defect characterisation with sub-micrometre resolution: We show recent progress in micro photoluminescence spectroscopy for the quantitative measurement of interstitial chromium with high spatial resolution. A further development of this setup will be discussed: By combining the principle of Light Beam Induced Current (LBIC) or voltage (LBIV) and the highly localized illumination, images of carrier recombination at local defects are presented which feature a, compared to EBIC, higher signal-to-noise ratio.