204 publications from this institution
The relation between the microstructure and the corrosion behavior of Hastelloy® G-35® in a KCl – AlCl3 salt solution after different defor
Speciation of rhenium in high-temperature alkali chloride-based melts was studied using electronic absorption and IR spectroscopy of molten salts and diffuse reflectance spectroscopy of quenched melts. Rhenium was added to the melts by anodic dissolution of the metal (at anodic current densities of 0.005 - 0.05 A/cm 2 ), by reacting Re and ReO 2 with Cl 2 and HCl, and by dissolving K 2 [ReCl 6 ]. The melts included 3LiCl-2KCl and NaCl-2CsCl eutectics, an NaCl-KCl equimolar mixture, and pure NaCl, KCl and CsCl between 450 and 850 ◦ C. Rhenium was present in the melts as Re(IV) hexachloro-ions, [ReCl 6 ] 2− ; no evidence of species containing rhenium in oxidation states below four was obtained. The kinetics of [ReCl 6 ] 2− disproportionation in molten alkali chlorides were investigated, and the IR spectra of [ReO 4 ] − ions in molten CsCl-CsI and CsI were measured for the first time.
The process of vanadium electrorefining in NaCl–KCl–VCl2 melts was investigated. The optimum conditions of refining were determined by varying cathodic current density, vanadium concentration in the melt and specific quantity of electricity passed through the cell. The total amount of impurities in the refined product was below 0.07 wt. % and the current efficiency was 0.95±0.03 g/Ah.
not Available.
Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 was studied at 750 0C in NaCl-KCl equimolar melts. Iron, chromium and manganese species constitute the major corrosion products. The following mechanism of stainless steel corrosion in molten chlorides was proposed: 1) chemical interaction between the alloy and the salt intensified by the formation of microgalvanic pairs; 2) formation of chromium and molybdenum carbide-containing phases in steel as a result of heating to 750 0C; 3) additional formation of galvanic pairs between the grains of austenitic alloys and the carbide phases at the grain boundaries resulting in enhanced intergranular corrosion.
The mechanism of corrosion of austenitic steels 12Kh18N10T, 10Kh17N13M2T, and 03Kh17N14M3 and metals Cr, Fe, Ni, and Mo in a NaCl-KCl-NbCln (n = 3.5, Nb co
A combination of high field solid-state MAS NMR spectroscopy, X-ray diffraction, and first-principles calculations is used to elucidate the crystalline structure of CsSc3F10. At room temperature, this phase was found to crystallize in the Pmma (n°51) space group with a = 8.0837(1) Å, b = 7.5764(1) Å, and c = 6.8127(1) Å. The remarkable feature of CsSc3F10 is an unusual high cesium coordination number of 18. 45Sc -19F D-HMQC NMR method has been employed to investigate the connectivity of scandium with fluorine atoms. NMR parameters were determined using first principle DFT calculations and compared with experimentally obtained data.
No abstract is provided for this article.
Vanadium equilibrium potentials were determined in NaCl-KCl equimolar melts containing 0.018 - 8.02 wt.% of vanadium between 690 and 820 oC. It was found that only vanadium(II) ions are present in the equilibrium with the metal. The temperature dependence of E*V2+/V formal standard potential was determined. Enthalpy and entropy change of the formation of vanadium(II) chloride in NaCl-KCl melt were determined. Hypothetical values of enthalpy and entropy change of the formation of super-cooled liquid vanadium(II) chloride were calculated. Enthalpy and entropy of mixing of VCl2 and NaCl-KCl were estimated.
No abstract is provided for this article.
The corrosion behavior of the corrosion-resistant alloy Hastelloy G-35 (manufactured by Haynes International, Inc.), corrosion and heat resistant alloy VDM Alloy 600 or Nicrofer 7216 and corrosion-resistant alloys VDM Alloy C-4 or Nicrofer 6616 and VDM Alloy 625 or Nicrofer 6020 (all produced by VDM Metals) was studied at 450–650 °C in fused KCl–AlCl3 mixture with the initial AlCl3-to-KCl ratio of 1.1. Time of exposure varied from 6 to over 1000 h. The corrosion rates of all the nickel-based alloys studied were determined by the red-ox processes resulting in dissolving the most electronegative alloy components (Cr, Fe and Mn) indicating that the processes taking place had electrochemical nature. Increasing temperature led to a noticeable increase of corrosion rates and a change of the corrosion process nature. Transmission electron microscopy revealed that intermetallic phases (such as sigma-phase in case of Hastelloy G-35 and Alloy 625 or Ni2(Cr,Mo) secondary phase in VDM Alloy C-4) can be formed during prolonged high-temperature exposure. These phenomena can accelerate the processes of intergranular corrosion and stress corrosion cracking of studied materials in industrial conditions. The results obtained agreed well with thermodynamic analysis, mechanical and thermophysical properties of the alloys and constructed "time-temperature-precipitation" diagrams.
The corrosion of KhN65MVU alloy was studied in chloride melts contained vanadium, zirconium, niobium and uranium ions and the rates of corrosion were determined for different electrolytes and temperatures. It was shown that interaction between the studied alloy and chloride melts containing transition metal ions occurs due to the oxidation of more electronegative components of the alloy by different cations from the molten salt environment. The process of oxidation is intensified at the grain boundaries where the microgalvanic pairs are formed as a result of excessive phase segregation. Anodic elements of the galvanic pairs are represented by depletion in molybdenum zones contacted with the excessive phases. It was also found that contacting KhN65MVU with niobium-containing melts results in the formation of diffusion coating on the substrate. This coating can protect the material from further oxidation by molten chloride electrolyte.
