The Experts below are selected from a list of 135 Experts worldwide ranked by ideXlab platform

P. K. Das - One of the best experts on this subject based on the ideXlab platform.

  • Optimization of time-temperature schedule for nitridation of silicon compact on the basis of silicon and Nitrogen Reaction kinetics
    Bulletin of Materials Science, 2000
    Co-Authors: J. Rakshit, P. K. Das
    Abstract:

    A time-temperature schedule for formation of silicon-nitride by direct nitridation of silicon compact was optimized by kinetic study of the Reaction, 3Si + 2N_2 = Si_3N_4 at four different temperatures (1250°C, 1300°C, 1350°C and 1400°C). From kinetic study, three different temperature schedules were selected each of duration 20 h in the temperature range 1250°-1450°C, for complete nitridation. Theoretically full nitridation (100% i.e. 66.7% weight gain) was not achieved in the product having no unreacted silicon in the matrix, because impurities in Si powder and loss of material during nitridation would result in 5–10% reduction of weight gain. Green compact of density < 66% was fully nitrided by any one of the three schedules. For compact of density > 66%, the nitridation schedule was maneuvered for complete nitridation. Iron promotes nitridation Reaction. Higher weight loss during nitridation of iron doped compact is the main cause of lower nitridation gain compared to undoped compact in the same firing schedule. Iron also enhances the amount of Β-Si_3N_4 phase by formation of low melting FeSi_x phase.

  • Optimization of time-temperature schedule for nitridation of silicon compact on the basis of silicon and Nitrogen Reaction kinetics
    Bulletin of Materials Science, 2000
    Co-Authors: J. Rakshit, P. K. Das
    Abstract:

    A time-temperature schedule for formation of silicon-nitride by direct nitridation of silicon compact was optimized by kinetic study of the Reaction, 3Si + 2N2 = Si3N4 at four different temperatures (1250°C, 1300°C, 1350°C and 1400°C). From kinetic study, three different temperature schedules were selected each of duration 20 h in the temperature range 1250°-1450°C, for complete nitridation. Theoretically full nitridation (100% i.e. 66.7% weight gain) was not achieved in the product having no unreacted silicon in the matrix, because impurities in Si powder and loss of material during nitridation would result in 5–10% reduction of weight gain.

C Rodriguez - One of the best experts on this subject based on the ideXlab platform.

  • characterisation of an arc xenon lamp and its application to titanium nitride synthesis
    Solar Energy Materials and Solar Cells, 1997
    Co-Authors: C Rodriguez
    Abstract:

    Abstract Concentrated solar energy offers unknown possibilities on surface modification of materials. The characterisation of 7 kW arc xenon lamp is presented as a solar simulator. The lamp has a maximum net power density of about 220 Wcm −2 with a spot of 8 mm diameter. With this equipment it is possible to treat steels and even melt of materials up to 2000K. Results are presented for the surface nitriding of Ti alloys performed in a Nitrogen Reaction chamber at atmospheric pressure. The good quality of the TiN coating is demonstrated by scanning electron microscopy, X-ray diffraction and Vickers hardeness (hardness about 1000 HV). Treating times could be as short as 30 s because the growth rate is about 4 μm/min. This rate is higher than many other nitriding processes. These results are a previous experimental work to direct nitriding of Ti alloys in real solar concentrating equipment.

J. Rakshit - One of the best experts on this subject based on the ideXlab platform.

  • Optimization of time-temperature schedule for nitridation of silicon compact on the basis of silicon and Nitrogen Reaction kinetics
    Bulletin of Materials Science, 2000
    Co-Authors: J. Rakshit, P. K. Das
    Abstract:

    A time-temperature schedule for formation of silicon-nitride by direct nitridation of silicon compact was optimized by kinetic study of the Reaction, 3Si + 2N_2 = Si_3N_4 at four different temperatures (1250°C, 1300°C, 1350°C and 1400°C). From kinetic study, three different temperature schedules were selected each of duration 20 h in the temperature range 1250°-1450°C, for complete nitridation. Theoretically full nitridation (100% i.e. 66.7% weight gain) was not achieved in the product having no unreacted silicon in the matrix, because impurities in Si powder and loss of material during nitridation would result in 5–10% reduction of weight gain. Green compact of density < 66% was fully nitrided by any one of the three schedules. For compact of density > 66%, the nitridation schedule was maneuvered for complete nitridation. Iron promotes nitridation Reaction. Higher weight loss during nitridation of iron doped compact is the main cause of lower nitridation gain compared to undoped compact in the same firing schedule. Iron also enhances the amount of Β-Si_3N_4 phase by formation of low melting FeSi_x phase.

  • Optimization of time-temperature schedule for nitridation of silicon compact on the basis of silicon and Nitrogen Reaction kinetics
    Bulletin of Materials Science, 2000
    Co-Authors: J. Rakshit, P. K. Das
    Abstract:

    A time-temperature schedule for formation of silicon-nitride by direct nitridation of silicon compact was optimized by kinetic study of the Reaction, 3Si + 2N2 = Si3N4 at four different temperatures (1250°C, 1300°C, 1350°C and 1400°C). From kinetic study, three different temperature schedules were selected each of duration 20 h in the temperature range 1250°-1450°C, for complete nitridation. Theoretically full nitridation (100% i.e. 66.7% weight gain) was not achieved in the product having no unreacted silicon in the matrix, because impurities in Si powder and loss of material during nitridation would result in 5–10% reduction of weight gain.

R J Fruehan - One of the best experts on this subject based on the ideXlab platform.

  • Recent advances in the fundamentals of the kinetics of steelmaking Reactions
    Metallurgical and Materials Transactions B, 2000
    Co-Authors: R J Fruehan, P. C. Glaws, D. Goldstein, B. Sarma, S. R. Story, H. U. Pasewicz
    Abstract:

    G.R. Belton was the leader in developing our understanding of the kinetics of metallurgical Reactions. Selected recent kinetic studies, based on this understanding and the application of the results to actual processes, are presented in this article. In particular, the rates of Reaction of carbon and carbon in iron with CO_2 and H_2O gases and FeO in slag are reviewed and applied to the iron smelting process. In addition, our basic understanding of the kinetics of the Nitrogen Reaction with iron is reviewed, and the results are used in comprehensive models, which can predict the Nitrogen content in steel as a function of operating variables in the basic oxygen furnace, electric arc furnace (EAF), and vacuum degassing.

  • Mathematical model for Nitrogen control in oxygen steelmaking
    Metallurgical and Materials Transactions B, 1999
    Co-Authors: D. A. Goldstein, R J Fruehan
    Abstract:

    A mathematical model was developed to quantify the effects of different operational parameters on the Nitrogen content of steel produced during oxygen steelmaking. The model predicts Nitrogen removal by the CO produced during decarburization and how the final Nitrogen content is affected by different process variables. These variables include the type of coolants used (scrap, direct reduced iron (DRI), etc. ), the sulfur content of the metal, combined gas blowing practices, and the Nitrogen content in the hot metal, scrap and oxygen blown. The model is a mixed control model that incorporates mass transfer and chemical kinetics. It requires a single parameter that reflects the surface area and mass-transfer coefficient that is determined from the rate of decarburization. The model also computes the rate of decarburization and the change in surface active elements, such as sulfur and oxygen, that affect the rate of the Nitrogen Reaction. Nitrogenization of steel in the converter is also predicted with the model. The computed results are in good agreement with plant data and observations.

  • Removal of Nitrogen from steel using novel fluxes
    Metallurgical and Materials Transactions B, 1991
    Co-Authors: K. Nomura, B. Ozturk, R J Fruehan
    Abstract:

    The solubility of Nitrogen and the nitride capacity of CaO-Al_2O_3-TiO_2 and CaO-BaO-Al_2O_3-TiO_2 slags were measured at 1873 K using a gas-slag-metal equilibration technique with carbon-saturated iron and gas mixtures of CO and N_2. The nitride capacity increased with increasing the TiO_2 and BaO content and is significantly higher than the nitride capacity for normal ladle slags. The activity coefficient of TiO_2 in CaO-Al_2O_3-TiO_2 and CaO-BaO-Al_2O_2-TiO_2 systems were measured. This is necessary to know in order to estimate the possible pickup of titanium in the metal when an aluminum-killed steel is treated with these slags. Also, the activity coefficient of Ti in carbon-saturated iron was measured. The kinetics of the Nitrogen Reaction between slag and metal is influenced by the oxygen potential in the metal and is primarily controlled by liquid-phase mass transfer of Nitrogen in the metal.

Shengmin Guo - One of the best experts on this subject based on the ideXlab platform.

  • Titanium and Nitrogen interactions under laser additive manufacturing conditions
    Surface and Coatings Technology, 2019
    Co-Authors: Congyuan Zeng, Hao Wen, Henry Bellamy, Phillip Sprunger, Paul J. Schilling, Shengmin Guo
    Abstract:

    Abstract To understand how to make bulk titanium parts or coatings with desired levels of titanium nitrides, this paper investigates the dynamic interactions between titanium and Nitrogen under representative laser-based additive manufacturing (AM) conditions. Under a set of gas environments containing different concentrations of Nitrogen, the titanium and Nitrogen Reaction products—formed under typical Selective Laser Melting (SLM) and Laser Engineered Net Shaping (LENS) AM scanning conditions—are examined for compositions, phases, and microstructures. In-situ synchrotron X-ray diffraction (SXRD) test is performed to reveal the high temperature Reaction steps between titanium and Nitrogen.