The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Shekhar Bhansali - One of the best experts on this subject based on the ideXlab platform.
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Selective growth of silica nanowires in silicon catalysed by Pt thin film
Nanotechnology, 2006Co-Authors: Praveen K. Sekhar, Senthil N. Sambandam, Dinesh K. Sood, Shekhar BhansaliAbstract:Selective growth of amorphous silica nanowires on a silicon wafer deposited with Pt thin film is reported. The mechanism of nanowire growth has been established to follow the vapour liquid solid (VLS) model via the PtSi phase acting as the catalyst. Nanowires grow with diameters ranging from 50 to 500 nm. These bottom-up grown nanowires exhibit photoluminescence with a stable emission of blue light at 430 nm under excitation. The effect of varying the seed layer thickness (Pt film) from 2 to 100 nm has been studied. It is observed that, above 10 nm thickness, a continuous layer of Pt(2)Si re-solidifies on the surface, inhibiting the growth of nanowires. The selectivity to the Pt thickness has been exploited to create regions of nanowires connected to conducting silicide (Pt(2)Si) simultaneously in a single Furnace Treatment. This novel approach has opened the gateways for realizing hybrid interconnects in silicon for various nano-optical applications such as the localization of light, low-dimensional waveguides for functional microphotonics, scanning near-field microscopy, and nanoantennae.
Janez Grum - One of the best experts on this subject based on the ideXlab platform.
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effect of high temperature Furnace Treatment on the microstructure and corrosion behavior of nicrbsi flame sprayed coatings
Corrosion Science, 2014Co-Authors: Zoran Bergant, Uros Trdan, Janez GrumAbstract:Abstract The microstructure and corrosion properties of flame-sprayed and heat-treated NiCrBSi coating on low-carbon steel are analyzed using an optical microscope, SEM/EDS and cyclic polarization electrochemical tests. Heat Treatment was performed at 930 °C, 1040 °C and 1080 °C for 10 and 20 min where densification of the coating occurred. Electrochemical corrosion tests in a 3.5 wt.% NaCl solution were performed on a low-carbon mild steel substrate, as-sprayed coating and on Furnace treated coating partially melted and fused between solidus and liquidus points at 1080 °C to evaluate the influence of heat Treatment on corrosion resistance.
S. S. Shibaev - One of the best experts on this subject based on the ideXlab platform.
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Nonmetallic inclusions in electric Furnace steel ShKh15SG-V bars
Russian Metallurgy (Metally), 2011Co-Authors: M.i. Gasik, A K Garber, K. V. Grigorovich, S. S. Shibaev, A. I. Panchenko, A. S. Sal’nikov, A. Yu. DalmatovAbstract:The mechanisms of formation and the methods of controlling nonmetallic inclusions (NIs) in bearing steel are considered. The number and composition of NIs in electric Furnace ShKh15SG-V steel bars made using various versions of heat and out-of-Furnace Treatment are studied by fractional gas analysis and number estimation according to State Standard GOST 801-79. A high calcium content is found to result in large globular NI numbers in the bars. Fractional gas analysis is shown to correctly determine the oxide inclusion content in steel.
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Analysis of various versions of the deoxidation of rail steel at OAO NTMK
Russian Metallurgy (Metally), 2009Co-Authors: A K Garber, A. V. Kushnarev, A M Arsenkin, K. V. Grigorovich, S. S. Shibaev, Yu. P. PetrenkoAbstract:The deoxidation of steel melted using various types of deoxidizers during out-of-Furnace Treatment is studied. The total oxygen and nitrogen content and the oxygen contents in the main types of oxide nonmetallic inclusions are determined by fractional gas analysis of steel samples taken from heats performed by various schedules. The main types of nonmetallic inclusions and their size distributions are found with qualitative and quantitative metallography. The oxygen content in the rail steel is minimal (5 ppm) when calcium carbide CaC_2 is introduced into the metal in tapping of a converter. When the metal is deoxidized using a steel wire filled with calcium or a steel wire filled with silicocalcium, the oxygen content in rail steel is ≈8 and ≈11 ppm, respectively. A comparison of various processes of rail steel deoxidation under the OAO NTMK conditions shows that the limitation of the aluminum content (no more than 30 ppm) or the use of a wire with a calcium or calcium carbide filler is more effective than the use of a wire filled with silicocalcium.
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Improvement of the technology of the out-of-Furnace Treatment of wheel steel
Russian Metallurgy, 2008Co-Authors: S. S. Shibaev, Andrea K. Garber, Yuri S. Demin, A. A. Shishov, A M Arsenkin, K. V. Grigorovich, K. A. MoskovoiAbstract:Various versions of the deoxidation and out-of-Furnace Treatment of wheel steel under the OAO VMZ conditions are analyzed. The effective partial pressure of carbon monoxide over a melt in a 130-t ladle degasser is found to be 54 ± 9 kPa. Thermodynamic analysis of the deoxidation demonstrates that low oxygen concentrations in the melt of wheel steel can be achieved when it is deoxidized by aluminum, silicocalcium, aluminocalcium, or carbon in vacuum. Experiments and a thermodynamic calculation show that the vacuum-carbon deoxidation of a high-strength wheel steel provides oxygen concentrations in the metal that are comparable with the concentrations obtained by silicocalcium deoxidation (0.0023 ± 0.0005 wt %) and ensures the optimum morphology and concentration of oxide inclusions. The causes of the formation of the defects revealed by ultrasonic inspection in railway wheel templates are studied. The level of rejection controlled by these defects depends on the deoxidation method and is related to the number and morphology of the oxide inclusions that form during secondary oxidation.
Yuri S. Demin - One of the best experts on this subject based on the ideXlab platform.
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Improvement of the technology of the out-of-Furnace Treatment of wheel steel
Russian Metallurgy, 2008Co-Authors: S. S. Shibaev, Andrea K. Garber, Yuri S. Demin, A. A. Shishov, A M Arsenkin, K. V. Grigorovich, K. A. MoskovoiAbstract:Various versions of the deoxidation and out-of-Furnace Treatment of wheel steel under the OAO VMZ conditions are analyzed. The effective partial pressure of carbon monoxide over a melt in a 130-t ladle degasser is found to be 54 ± 9 kPa. Thermodynamic analysis of the deoxidation demonstrates that low oxygen concentrations in the melt of wheel steel can be achieved when it is deoxidized by aluminum, silicocalcium, aluminocalcium, or carbon in vacuum. Experiments and a thermodynamic calculation show that the vacuum-carbon deoxidation of a high-strength wheel steel provides oxygen concentrations in the metal that are comparable with the concentrations obtained by silicocalcium deoxidation (0.0023 ± 0.0005 wt %) and ensures the optimum morphology and concentration of oxide inclusions. The causes of the formation of the defects revealed by ultrasonic inspection in railway wheel templates are studied. The level of rejection controlled by these defects depends on the deoxidation method and is related to the number and morphology of the oxide inclusions that form during secondary oxidation.
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Improving the Out-of-Furnace Treatment of Wheel Steel by Using an Integrated Technology
Metallurgist, 2005Co-Authors: S. V. Sukharev, I. V. Kushnerev, S. A. Korolev, S. V. Kazakov, Yuri S. DeminAbstract:It has been shown that a new out-of-Furnace Treatment complex can be used in the open-hearth shop of the Vyksa Metallurgical Plant to make wheel steel that fully satisfies the existing requirements of the Russian Ministry of Railroads. The improved technology is distinguished by lower consumption indices due to the conservation of ferroalloys and alloying materials, shortening of the Treatment, and stabilization of the conditions under which it is administered. Use of the technology makes it possible to obtain metal that meets present-day standards on product quality.
A. C. Crawford - One of the best experts on this subject based on the ideXlab platform.
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Efficient expulsion of magnetic flux in superconducting RF cavities for high $Q_0$ applications
Journal of Applied Physics, 2016Co-Authors: Sam Posen, Anna Grassellino, Alexander Romanenko, Oleksandr Melnychuk, Dmitri Sergatskov, Martina Martinello, Mattia Checchin, A. C. CrawfordAbstract:Even when cooled through its transition temperature in the presence of an external magnetic field, a superconductor can expel nearly all external magnetic flux. This Letter presents an experimental study to identify the parameters that most strongly influence flux trapping in high purity niobium during cooldown. This is critical to the operation of superconducting radiofrequency cavities, in which trapped flux degrades the quality factor and therefore cryogenic efficiency. Flux expulsion was measured on a large survey of 1.3 GHz cavities prepared in various ways. It is shown that both spatial thermal gradient and high temperature Treatment are critical to expelling external magnetic fields, while surface Treatment has minimal effect. For the first time, it is shown that a cavity can be converted from poor expulsion behavior to strong expulsion behavior after Furnace Treatment, resulting in a substantial improvement in quality factor. Future plans are described to build on this result in order to optimize Treatment for future cavities.Comment: 5 page
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Flux expulsion variation in SRF cavities
arXiv: Accelerator Physics, 2015Co-Authors: Sam Posen, Anna Grassellino, Alexander Romanenko, Oleksandr Melnychuk, Dmitri Sergatskov, Martina Martinello, Mattia Checchin, A. C. CrawfordAbstract:Treating a cavity with nitrogen doping significantly increases $Q_0$ at medium fields, reducing cryogenic costs for high duty factor linear accelerators such as LCLS II. N-doping also makes cavities more sensitive to increased residual resistance due to trapped magnetic flux, making it critical to either have extremely effective magnetic shielding, or to prevent flux from being trapped in the cavity during cooldown. In this paper, we report on results of a study of flux expulsion. We discuss possible ways in which flux can be pinned in the inner surface, outer surface, or bulk of a cavity, and we present experimental results studying these mechanisms. We show that grain structure appears to play a key role and that a cavity that expelled flux poorly changed to expelling flux well after a high temperature Furnace Treatment. We further show that after Furnace Treatment, this cavity exhibited a significant improvement in quality factor when cooled in an external magnetic field. We conclude with implications for SRF accelerators with high $Q_0$ requirements.
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A pathway to SRF niobium cavities processing simplification and quality factor improvement via elimination of the post-annealing chemical Treatment
arXiv: Accelerator Physics, 2013Co-Authors: Anna Grassellino, Alexander Romanenko, Oleksandr Melnychuk, Dmitri Sergatskov, A. C. Crawford, Allan Rowe, M. Wong, C. Cooper, D. Bice, Y. TrenikhinaAbstract:We investigate the effect of high temperature Treatments followed by only high-pressure water rinse (HPR) of superconducting radio frequency (SRF) niobium cavities. The objective is to provide a cost effective alternative to the typical cavity processing sequence, by eliminating the material removal step post Furnace Treatment while preserving or improving the RF performance. The studies have been conducted in the temperature range 800-1000C for different conditions of the starting substrate: large grain and fine grain, electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish. An interesting effect of the grain size on the performances is found. Cavity results and samples characterization show that Furnace contaminants cause poor cavity performance, and a practical solution is found to prevent surface contamination. Extraordinary values of residual resistances ~ 1 nOhm and below are then consistently achieved for the contamination-free cavities. These results lead to a more cost-effective processing and improved RF performance, and, in conjunction with CBP, open a potential pathway to acid-free processing.
