The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform

G. Den Ouden - One of the best experts on this subject based on the ideXlab platform.

  • Softening behaviour of Al–Zn–Mg alloys due to welding
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1999
    Co-Authors: G. Den Ouden
    Abstract:

    Abstract The softening behaviour of two Al–Zn–Mg alloys (7020 and 7022) due to welding was studied by means of simulation and real welding experiments. It was found that the heat-affected Zone of the alloys can be divided in two parts: the Dissolution Zone and the overageing Zone. The Dissolution Zone is characterised by Dissolution of the strengthening precipitates, whereas the overageing Zone is characterised by growth of the strengthening precipitates. It appears that the 7022 alloy has a stronger softening tendency than the 7020 alloy in both the Dissolution Zone and the overageing Zone. It was also found that the degree of softening depends on the heat input: a higher input leads to more severe softening and a wider softening area, located at a larger distance from the fusion boundary. The hardness in the heat-affected Zone can be recovered by post-weld heat treatment, especially in the Dissolution Zone. As far as the recovery of the hardness is concerned, artificial ageing is more effective than natural ageing.

Hong Wang - One of the best experts on this subject based on the ideXlab platform.

  • Studies on softening of heat-affected Zone of pulsed-current GMA welded Al-Zn-Mg alloy
    Journal of Materials Processing Technology, 2006
    Co-Authors: Fuquan Tian, Hong Wang
    Abstract:

    Abstract Studies on the softening behavior of the 7005 alloy by means of real welding experiments and heat-affected Zone (HAZ) simulation have been conducted. Softening in the HAZ is found to occur above a peak temperature of about 200 °C. It was found that the heat-affected Zone of the alloys can be divided into two sub-Zones according to their different mechanism of softening: the Dissolution Zone and the overageing Zone. The Dissolution Zone is characterised by Dissolution of precipitates and covers the peak temperature range above 380 °C. The overageing Zone is characterised by growth of precipitates and covers the peak temperature range between 230 and 380 °C. The hardness in the heat-affected Zone can be recovered by post-weld heat treatment, especially in the Dissolution Zone. Artificial ageing is more effective than natural ageing considering the recovery of the hardness.

N. I. Sorokin - One of the best experts on this subject based on the ideXlab platform.

  • Ionic conductivity of sodium–strontium germanate Na_4SrGe_6O_15
    Crystallography Reports, 2017
    Co-Authors: N. I. Sorokin
    Abstract:

    The electrical conductivity of sodium–strontium germanate Na_4SrGe_6O_15 (sp. gr. P 6_3/ m ) has been studied by impedance spectroscopy in the frequency range of 10^2–4 × 10^4 Hz and a temperature range of 450–600 K. Na4SrGe6O15 crystals were obtained by hydrothermal technique in the Na_2O–SrO–GeO_2–H_2O system (temperature t = 300–600°C and pressure p = 1.4 × 10^8 Pа in the Dissolution Zone). The ionic conductivity of ceramic Na_4SrGe_6O_15 samples is σ = 2.2 × 10^–6 S/cm (at 573 K), the activation energy of Na^+ ion transfer is E _ a = 0.70 ± 0.03 eV.

  • Ionic conductivity of single crystals of sodium aluminium germanate Na 8 Al 6 Ge 6 O 24 (OH) 2
    Crystallography Reports, 2015
    Co-Authors: N. I. Sorokin
    Abstract:

    The electrical conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2 (cubic system, sp. gr. \(P\overline 4 n\)), which is a germanium analog of sodalite, has been studied in the temperature range of 468‒758 K. Na8Al6Ge6O24(OH)2 crystals are obtained by hydrothermal synthesis (temperature in the Dissolution Zone 573‒673 K, temperature gradient ~1.5 K/cm). NaAlO2 and GeO2В oxides are used as starting reagents; NaOH hydroxide serves as a solvent. The ionic conductivity of Na8Al6Ge6O24(OH)2 crystals is 2 × 10−4 S/cm (at 758 K); the activation energy of ionic transfer is 0.46 ± 0.03 eV.

  • Ionic conductivity of single crystals of sodium aluminium germanate Na_8Al_6Ge_6O_24(OH)_2
    Crystallography Reports, 2015
    Co-Authors: N. I. Sorokin
    Abstract:

    The electrical conductivity of single crystals of sodium aluminium germanate Na_8A_l6Ge_6O_24(OH)_2 (cubic system, sp. gr. $$P\overline 4 n$$ ), which is a germanium analog of sodalite, has been studied in the temperature range of 468‒758 K. Na_8A_l6Ge_6O_24(OH)_2 crystals are obtained by hydrothermal synthesis (temperature in the Dissolution Zone 573‒673 K, temperature gradient ~1.5 K/cm). NaAlO_2 and GeO_2В oxides are used as starting reagents; NaOH hydroxide serves as a solvent. The ionic conductivity of Na_8Al_6Ge_6O_24(OH)_2 crystals is 2 × 10^−4 S/cm (at 758 K); the activation energy of ionic transfer is 0.46 ± 0.03 eV.

R. Jeffrey Serne - One of the best experts on this subject based on the ideXlab platform.

  • Geochemical evolution of highly alkaline and saline tank waste plumes during seepage through vadose Zone sediments
    Geochimica et Cosmochimica Acta, 2004
    Co-Authors: Jiamin Wan, Tetsu K. Tokunaga, Joern T. Larsen, R. Jeffrey Serne
    Abstract:

    Abstract Leakage of highly saline and alkaline radioactive waste from storage tanks into underlying sediments is a serious environmental problem at the Hanford Site in Washington State. This study focuses on geochemical evolution of tank waste plumes resulting from interactions between the waste solution and sediment. A synthetic tank waste solution was infused into unsaturated Hanford sediment columns (0.2, 0.6, and 2 m) maintained at 70°C to simulate the field contamination process. Spatially and temporally resolved geochemical profiles of the waste plume were obtained. Thorough OH − neutralization (from an initial pH 14 down to 6.3) was observed. Three broad Zones of pore solutions were identified to categorize the dominant geochemical reactions: the silicate Dissolution Zone (pH > 10), pH-neutralized Zone (pH 10 to 6.5), and displaced native sediment pore water (pH 6.5 to 8). Elevated concentrations of Si, Fe, and K in plume fluids and their depleted concentrations in plume sediments reflected Dissolution of primary minerals within the silicate Dissolution Zone. The very high Na concentrations in the waste solution resulted in rapid and complete cation exchange, reflected in high concentrations of Ca and Mg at the plume front. The plume-sediment profiles also showed deposition of hydrated solids and carbonates. Fair correspondence was obtained between these results and analyses of field borehole samples from a waste plume at the Hanford Site. Results of this study provide a well-defined framework for understanding waste plumes in the more complex field setting and for understanding geochemical factors controlling transport of contaminant species carried in waste solutions that leaked from single-shell storage tanks in the past.

Kai Wang - One of the best experts on this subject based on the ideXlab platform.

  • Corrosion Properties of Cold Spray Zn-25Al Coating in Marine Environment
    Applied Mechanics and Materials, 2011
    Co-Authors: Qingjun Zhu, Kai Wang
    Abstract:

    Zn-25Al coatings were prepared by cold spray on mild carbon steel Q235. The coatings were studied by potentiodynamic polarization test, corrosion potentials and electrochemical impedance spectrum in natural seawater. The results show that the Ecorr of Zn-25Al coating is -1.01V (SCE) and the Ecorr of Q235 is -0.65V (SCE) at the beginning of the immersion. Self-corrosion potential of Zn-25Al coating is lower than that of Q235. The coatings turn to activity anodic Dissolution Zone when the potential reaches -1.05V. The coatings changes to passivation Zone after the potential reaches -1.01V and the current intensities increase slightly with the potential increasing quickly. Zn-25Al coatings can provide lower protection potential and promising current to protect Q235 from corrosion.

  • microstructure and anti corrosion properties of arc sprayed aluminum coating in splash Zone
    Advanced Materials Research, 2011
    Co-Authors: Kai Wang
    Abstract:

    Aluminum coatings were developed by arc spray on mild carbon steel Q235. Scanning electron microscopy detection shows that the coatings have good bonding with the substrate and have low porosity. The corrosion behaviors of the coatings in splash Zone were studied. The results show that free corrosion potentials of aluminum coatings are much lower than that of Q235. Potentiodynamic polarization measurements reveal that the curves of aluminum coatings have activity anodic Dissolution Zone, passivation Zone and super-passivation Zone. Corrosion morphology and energy dispersive spectrometers show that Cl- can penetrate into the coatings and some of the substrate has been corroded. The arc spray Al-coating develops a film of corrosion products on the coating surface, which tend to seal the pores in the coatings. Arc spray aluminum coatings can protect the substrate from corrosion in splash Zone.

  • Corrosion Behavior of Cold-Spray Aluminum Coating in Marine Environment
    Advanced Materials Research, 2010
    Co-Authors: Kai Wang, Xin-hong Wang
    Abstract:

    Aluminum coatings were prepared by cold spray on mild carbon steel Q235. Scanning electron microscopy shows that the bond Zone has good bonding between the substrate and the coating and the coatings consist of interlocked particles. The corrosion behaviors of the coatings in marine environment were studied by electrochemical methods. Free corrosion potentials of aluminum coatings are much lower than that of Q235. Potentiodynamic polarization measurements show that the curves of aluminum coatings have activity anodic Dissolution Zone, passivation Zone and super-passivation Zone. Corrosion morphology and energy dispersive spectrometers show that Cl- can penetrate into the coating and some of the substrate has been corroded. Corrosion only can happen on the coating surface and specific deeper sites, where Cl- can penetrate through pores. Cold spray aluminum coatings can protect the substrate from corrosion in marine environment.