Papers by Keyword: Barium

Abstract: For the first time, the time dependences of the temperature of aluminum, zinc and zinc-aluminum alloys alloyed with II A group elements under spontaneous cooling mode were obtained; an anomalous course and two characteristic times of the cooling process were found, and their mechanism was explained; the temperature dependence of the thermophysical properties of the investigated metals and alloys was established; the temperature dependence of the coefficients of convective heat transfer and radiation of Al, Zn and Zn55Al and Zn5Al alloys was experimentally determined; the influence of the concentration of II A group elements and temperature on the heat capacity and thermodynamic functions of Zn55Al and Zn5Al alloys was revealed.

Abstract: Error reasons of gold analytical determination in the chemical plant sludge are studied. The studied sludge is waste of BaCl₂ production. According to preliminary estimates it contains gold in sufficient quantity for industrial extraction. Comparison of direct sludge fire assay analysis and sludge dissolution in aqua regia, followed by gold atomic absorption determination in solution is made. The negative effect of Na⁺, Ca²⁺, Ba²⁺, Zn²⁺ ions presence in studied solutions was shown. Error quantitative estimate at alkali metals introducing into standard solutions is given. It is shown that Ca²⁺ and Ba²⁺ ions contribute the most error. Error increases linearly at addition of Ca²⁺ and Ba²⁺ ions. Growth error gradually slow down at increasing Na⁺, Zn²⁺ ion content.

Abstract: A thickness of Ba-introduced gate oxide was controlled with the oxygen concentration and a barrier layer thickness at a post-deposition annealing. The oxidation rate becomes slower with the low oxygen concentration and the thick barrier layer, and the thin oxide of 12 nm was realized with O₂ 5% and 9 nm of the barrier layer. This Ba-introduced thin gate oxide resulted in the field effect mobility of 13 cm²/Vs and the interface state density of 2×10¹¹ cm^-2eV^-1 at 0.25 eV below the conduction band edge of 4H-SiC.

Abstract: A correlation between field effect mobility and an accumulation conductance has been investigated at 4H-SiC MOS interface with barium. 4H-SiC n-channel MOSFETs and n-type MOS capacitors were fabricated with a barium-introduced SiO₂ and a conventional dry SiO₂. The field effect mobility was enhanced by introducing the barium-introduced SiO₂. It is found that there is a linear correlation between the mobility and the accumulation conductance. The MOS interface of the barium-introduced SiO₂ had a lower interface state density of 2×10¹¹ cm^-2eV^-1 than that of the conventional dry SiO₂.

Abstract: Enhanced-oxidation of 4H-SiC and interface modification with BaO₂ was investigated. The enhanced oxidation of 4H-SiC was drastically dependent on pre-deposited BaO₂ thickness. At the oxidation time of 300 min, oxide thicknesses for BaO₂ of 2.8 nm and 7.8 nm were 91.8 nm and 26.2 nm, respectively. The physical state of Ba in the oxide was investigated by XPS and 2D-GIXD. At thick BaO₂ with a thickness of over 6.4 nm, bridged oxygen and non-bridged oxygen were observed in O1s state. This results shows barium silicate was formed in SiO₂ at BaO₂ thickness of over 6.4 nm.

Abstract: Surface morphology and electrical properties of silicon dioxide (SiO₂) on 4H-SiC substrates formed by metal-enhanced oxidation (MEO) using barium (Ba) atoms were systematically investigated. It was found that severe surface roughening caused by Ba-MEO can be suppressed by using SiO₂ capping prior to MEO. The Ba atoms at the SiO₂/SiC interface were found to diffuse to the oxide surface through the deposited SiO₂ capping layer, and then the Ba density reduced to ~10¹⁴ cm^-2 before stable MEO. The resulting SiO₂/SiC interface showed the reduced interface state density but the insulating property of the oxides was significantly degraded.

Abstract: The paper considers carbon, silicon and aluminum reduction of barium and strontium from natural materials by thermodynamic modeling in conditions of out-of-furnace steel treatment. X-rays phase and differential thermal methods of analysis were applied to investigate the samples of natural barium and strontium containing material. A process flowsheet of steel treatment by barium-strontium modifier in induction furnace was developed on the basis of carried out research.

Abstract:

Magnesium alloys have been finding increasingly more types of application in the automotive and aerospace industries for over twenty years. Despite the fact conventional magnesium alloys have limited high-temperature strength and creep resistance, especially when they contain aluminium as an alloying element. Aluminium is necessary to improve the castability when high-pressure die casting is the favoured process. Applications with higher operating temperatures require additional alloy elements, which form precipitates with the aluminium during solidification and therefore prevent the formation of Mg₁₇Al₁₂, which is responsible for the low creep resistance of magnesium alloys that contain aluminium. The precipitates formed may also strengthen grain boundaries and so improve the creep strength. Barium and calcium were investigated as elements in a magnesium alloy containing aluminium (DieMag422: 4 wt.-% Al, 2 wt.-% Ba, 2 wt.-% Ca). The compression creep strength was compared at 240°C for stresses between 60 and 120 MPa with two commercial creep-resistant magnesium alloys, AE42 and MRI230D. The stress exponents were calculated from the stress dependence of the minimum creep rate. The concept of a threshold stress was applied and true stress exponents n_t close to 5 were found. The new alloy DieMag422 exhibits improved creep strength compared to both commercial alloys and also has proven it is die castable.

Abstract: The development of creep resistant high pressure die casting (HPDC) alloys is one of the main focuses in magnesium research. Alloying elements like rare earths, calcium, strontium or scandium added to the necessary aluminium for die casting have already been introduced. Newly developed barium containing magnesium alloys with three levels of alloying additions were processed via HPDC and their compression creep response at 200 °C was evaluated. DieMag633 (Mg-6Al-3Ba-3Ca) displays the best creep resistance followed by DieMag422 (Mg-4Al-2Ba-2Ca) and then DieMag211 (Mg-2Al-1Ba-1Ca). Stress exponents from tests at different applied stresses were calculated. The creep tests were also accompanied by microstructural investigations and mechanical property evaluation.

Abstract: Sendust soft magnetic composites coated by a thin Ba-B-P-O system insulating layer were produced; SEM spectroscopy and Energy dispersive X-ray analysis spectroscopy confirmed that thin layers of Ba-B-P-O system covered the alloy powders. The influence of various compaction pressures on composites permeability, DC properties and total loss was investigated. The Fe-Si-Al magnetic powder core with compaction pressure of 1932MPa, annealing temperature of 953K with a permeability of 94, a total loss of 108 mW/cm³.