Papers by Keyword: Silicon Powder

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Authors: Jun Cong Wei, Jun Bo Tu, Jian Cao
Abstract: Molten iron corrosion resistance of silicon-corundum-silicon nitride composites were investigated using corundum, silicon nitride, clay and silicon powder as the main starting materials by static crucible method. The corrosion mechanism of the composites was analyzed by means of scanning electron microscope (SEM with EDS). The results revealed that corundum-silicon nitride composites possessed good molten iron corrosion behavior and the active oxidation of silicon nitride was the main reason for loose structure of the corroded specimen; The composites produced a dense layer by addition of silicon, which made superior molten iron corrosion resistance behavior.
Authors: Jun Cong Wei, Xiu Mei Ji, Jian Kun Huang, Chun Hui Gao, Jun Bo Tu
Abstract: The effects of addition of silicon powder (1 wt. %) and Na2CO3 (converting to additional 0.5%, 1% Na2O) on the hot modulus of rupture (HMOR) of MgO-Al-C bricks were investigated. MgO-Al-C refractories were prepared by using fused magnesia and graphite flake as main starting materials, and Si, Na2CO3 or both as additives. Its phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results showed that the HMOR of MgO-Al-C bricks increased slightly with addition of Si powder. However, the HMOR decreased when adding Na2CO3 and Si powder together. Moreover, the HMOR deduced with the increase of Na2CO3 content. The mechanism is that Al powder reacted to form fibrous Al4C3 and AlN, which could improve the HMOR. When silicon was added, β-SiC and M2S were formed, which could fill the passages and pores. So the densification and strength were improved. The addition of Na2CO3 could promote the oxidation of Al powder to form Al2O3, and inhibit the formation of Al4C3 and AlN. Hence the strength of MgO-Al-C deduced.
Authors: Daniel Rodrigues, J.B. Ferreira Neto, Lucio Salgado, P.F. Nogueira, J.G.R. Poço
Authors: Xiu Mei Ji, Jun Cong Wei, Jian Kun Huang, Chun Hui Gao, Jun Bo Tu
Abstract: To improve the hydration resistance of MgO-Al-C bricks, Na2CO3 was chosen as an additive through thermodynamic calculation. MgO-Al-C refractories were prepared by using Si, Na2CO3 or both as additives. The effects of additives on the hydration resistance of specimens were investigated. XRD was conducted to determine the phase composition. The results showed that the hydration resistance of MgO-Al-C bricks would be improved slightly with addition of only Si due to the densification of the structure. When Na2CO3 and Si were added together, the hydration resistance would be improved remarkably. The mechanism is that Na2CO3 could decompose to give off O2 during heating, which could promote the oxidation of Al metal and inhibit the formation of Al4C3 and AlN.
Authors: K. Sikorski, Agnieszka Szymańska, M. Sekuła, D. Kowalczyk, Jan Kazior, Krzysztof Jan Kurzydlowski
Abstract: The aim of the study was to obtain a ferritic-austenitic stainless steel through sintering of the mixture of austenitic steel AISI 316L powders with silicon in the amount ranging from 1 to 7%. The pressed mixtures were sintered at 1240oC for 60 minutes under hydrogen atmosphere. The results of the silicon admixture on the density, porosity, microstructure and mechanical properties of the sintered specimens are discussed.
Authors: Thipwan Fangsuwannarak, K. Khunchana, S.T. Rattanachan
Abstract: In this study, silicon nanocrystal (Si-nc) films were synthesized by compositing of Si-nc powder embedded in silicon oxide phase. The Si-nc film produced by the spin-coating methode using Tetraethylorthosilicate, ethanol, phosphoric acid, and Si-nc powder as suspension precursors. The variation in structural and optical properties of Si-nc sol films with the amounts of Si-nc powder have been characterized. Atomic force microscopy (AFM) shows that low density level of Si-nc power can result in the amount of porosity in the Si-nc films. It is found that when the Si-nc films have the higher Si-nc density, the small pores in the SiO2 phase were removed. In addition, optical energy gap (Eg) of Si-nc samples was evaluated by the Tauc plot method. It is a crucial attribute for a promising photonic device. The obtained optical bang gap values were extended from 1.10 eV to 1.40 eV as compared with the typical Si bulk. In addition, density of Si-nc clusters has a considerable effect on the electrical conductance of the Si-nc films measured at room temperature.
Authors: Jun Cong Wei, Jun Bo Tu
Abstract: Effects of silicon powder additions on the phase composition and microstructure of silicon- corundum-silicon nitride composite refractories were investigated guided by the theory of metal transient plastic phase and the Si-O-N phase diagram. On this basis, silicon-corundum-silicon nitride composites were prepared under air atmosphere. The results showed that the addition of silicon powder could reduce the width of the oxidized film and improve the densification; silicon addition could decrease the oxygen partial pressure in the specimens and contribute to the sintering of the materials. Part of silicon could remain in the materials. The industrial experiments suggested that silicon powder mostly filled in the interstices of the matrix of the sintered products with addition of less than 8 wt.% Si powder, and with increasing Si powder additions the densification of the product was improved, cold strength increased, and hot strength also increased due to the in-situ formed fibrous SIALON by silicon powder; silicon powder formed continuous phase which led to the decrease in densification and hot strength when more than 8 wt.% silicon powder was added.
Authors: Fang Zhang, Zhi Liang Huang
Abstract: The study is carried out combing with the production practice in Danjiangkou Hongyuan SiC limited. Si3N4 and SiC were prepared successfully from SiC and Silicon power in nitrogen atmosphere at 1425°C and 1375°C sintering temperature by the serial of techniques, such as ingredients, mixing, molding and drying, respectively. In the actual production, silicon powder content and sintering temperature will directly influence the products of the bending strength and thermal shock resistance. By measuring bending strength, porosities, bulk density, XRD and FESEM, the bending strength and thermal shock resistance of samples were studied mainly by changing sintering temperature and silicon powder content. The results show that bending strength and thermal shock resistance of sample which was added 16% Si powder is best. And bending strength and thermal shock resistance of sample of 1425°C sintering temperature is higher than that of 1375°C sintering temperature.
Authors: Song Gao, Li Dai
Abstract: According to the cycles of freezing and thawing frequently happened during early spring and late autumn in northeast china, this paper studies on the frost resistance of concrete using in highway pavement. Making experiments by adding flyash, silicon powder, air entraining and water reducing agent to normal concrete with different proportions and using flexure strength, compression strength and mass loss rate of concrete as evaluating indicators, a reasonable and economic concrete proportion is determined, which reaches high flexure strength and compression strength, good frost resistance. On the bases of the experimental results and economic analysis, it is shown that the concrete proportion can effectively enhance the frost resistance of concrete. Therefore, it has good use value and it is promising with a good prospect of application.
Authors: Zhong Ning Zhang, Jian Tian
Abstract: There are the four types of defects during remote laser welding of zinc coated sheet metal. The root cause of all these defects is the explosion or ejection of molten weld metal caused by the escape of trapped high pressurized zinc vapor. De-gassing gapping is a method used to solve the defects. We have researched the silicon powder de-gassing gapping method for remote laser welding with coupons of zinc coated sheet metal. The result shows that silicon powder de-gassing gapping method works well.
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