The Experts below are selected from a list of 687774 Experts worldwide ranked by ideXlab platform
Yunfa Chen - One of the best experts on this subject based on the ideXlab platform.
-
acid leaching pretreatment on two stage roasting pyrite cinder for gold extraction and co precipitation of arsenic with iron
Hydrometallurgy, 2018Co-Authors: Yongliang Wang, Li Xiao, Hongxiao Liu, Peng Qian, Yunfa ChenAbstract:Abstract The leaching recovery of gold is low caused by the arsenic inclusion and gold encapsulation in the two-stage roasting pyrite cinder. It is necessary to pretreat the cinder to improve the recovery of gold. In this study, sulfuric acid was employed to remove arsenic and iron from the cinder, and then the arsenic was transferred to Precipitates from the leaching solution by ferric ion precipitation for harmless disposal. The vast majority of the arsenic and iron were leached into the solution at 80 °C under atmospheric pressure. The recovery rate of gold in residue after non-cyanide extraction was greatly improved, and the gold content in residue decreased from 11.2 g/t to 3.8 g/t. The leached iron was partly precipitated by controlling the additive amount of hydrogen peroxide and pH value to precipitate the arsenic. The arsenic concentration in the solution was reduced to about 5 mg/L after 1 h of precipitation. The size of the Precipitates was increased to >100 μm when the pH value was >5.69. In addition, the Precipitates had a strong adsorption capacity to absorb many other impurity ions such as ammonium. This study indicates that the removal of arsenic and iron from cinder is beneficial to increase the recovery of gold, and it is effective to remove the arsenic from the leaching solution through co-precipitation with ferric ion.
H W Zandbergen - One of the best experts on this subject based on the ideXlab platform.
-
the structural relation between Precipitates in al mg si alloys the al matrix and diamond silicon with emphasis on the trigonal phase u1 mgal2si2
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Sigmund Jarle Andersen, Calin Daniel Marioara, R Vissers, Anders G Froseth, H W ZandbergenAbstract:Abstract Atomic structures of the Precipitates in Al–Mg–Si alloys have important similarities. The trigonal precipitate U1-MgAl 2 Si 2 has super-cells in both Al and diamond Si. U1 is related to the Precipitates β′, U2, and B′ via silicon. The Si-content of the four Precipitates can be described as triangular planes parallel to Al {1 0 0} or Al {3 1 0} planes. Large Si-particles frequently align two of their {1 1 1} planes in a similar way. In the Al–Mg–Si alloy system this correspondence explains most coherency relations between Precipitates, and between Precipitates and matrix. The connection with Si gives a unified view of the precipitate structures. A model is given for a reflection twin boundary in U1.
R D Noebe - One of the best experts on this subject based on the ideXlab platform.
-
tem study of structural and microstructural characteristics of a precipitate phase in ni rich ni ti hf and ni ti zr shape memory alloys
Acta Materialia, 2013Co-Authors: R Santamarta, Raymundo Arroyave, J Pons, A Evirgen, I Karaman, H E Karaca, R D NoebeAbstract:Abstract The Precipitates formed after suitable thermal treatments in seven Ni-rich Ni–Ti–Hf and Ni–Ti–Zr high-temperature shape memory alloys have been investigated by conventional and high-resolution transmission electron microscopy. In both ternary systems, the precipitate coarsening kinetics become faster as the Ni and ternary element contents (Hf or Zr) of the bulk alloy are increased, in agreement with the precipitate composition measured by energy-dispersive X-ray microanalysis. The precipitate structure has been found to be the same in both Hf- and Zr-containing ternary alloys, and determined to be a superstructure of the B2 austenite phase, which arises from a recombination of the Hf/Zr and Ti atoms in their sublattice. Two different structural models for the precipitate phase were optimized using density functional theory methods. These calculations indicate that the energetics of the structure are not very sensitive to the atomic configuration of the Ti–Hf/Zr planes, thus significant configurational disorder due to entropic effects can be envisaged at high temperatures. The Precipitates are fully coherent with the austenite B2 matrix; however, upon martensitic transformation, they lose some coherency with the B19′ matrix as a result of the transformation shear process in the surrounding matrix. The strain accommodation around the particles is much easier in the Ni–Ti–Zr-containing alloys than in the Ni–Ti–Hf system, which correlates well with the lower transformation strain and stiffness predicted for the Ni–Ti–Zr alloys. The B19′ martensite twinning modes observed in the studied Ni-rich ternary alloys are not changed by the new precipitated phase, being equivalent to those previously reported in Ni-poor ternary alloys.
R Vissers - One of the best experts on this subject based on the ideXlab platform.
-
the structural relation between Precipitates in al mg si alloys the al matrix and diamond silicon with emphasis on the trigonal phase u1 mgal2si2
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Sigmund Jarle Andersen, Calin Daniel Marioara, R Vissers, Anders G Froseth, H W ZandbergenAbstract:Abstract Atomic structures of the Precipitates in Al–Mg–Si alloys have important similarities. The trigonal precipitate U1-MgAl 2 Si 2 has super-cells in both Al and diamond Si. U1 is related to the Precipitates β′, U2, and B′ via silicon. The Si-content of the four Precipitates can be described as triangular planes parallel to Al {1 0 0} or Al {3 1 0} planes. Large Si-particles frequently align two of their {1 1 1} planes in a similar way. In the Al–Mg–Si alloy system this correspondence explains most coherency relations between Precipitates, and between Precipitates and matrix. The connection with Si gives a unified view of the precipitate structures. A model is given for a reflection twin boundary in U1.
Jan Vanhellemont - One of the best experts on this subject based on the ideXlab platform.
-
precipitation and extended defect formation in silicon
Physica Status Solidi (c), 2005Co-Authors: Jan Vanhellemont, Olivier De Gryse, Paul ClauwsAbstract:The impact of self-interstitials and strain on the critical size for nucleation of incoherent Precipitates is well-known. A factor that has been neglected so far is the incorporation of intrinsic point defects of the host matrix in the precipitate itself. It is shown that this can have an important impact both on the critical r size and on the precipitated phase. The theoretical results are illustrated for the case of oxygen precipitation in silicon. The growing precipitate can also cause the nucleation of extended lattice defects such as dislocations and stacking faults in the surrounding matrix. A model is presented to predict stacking fault r nucleation.
-
oxide phase determination in silicon using infrared spectroscopy and transmission electron microscopy techniques
Journal of Applied Physics, 2002Co-Authors: Olivier De Gryse, Paul Clauws, J Van Landuyt, O I Lebedev, Cor Claeys, Eddy Simoen, Jan VanhellemontAbstract:Infrared absorption spectra of polyhedral and platelet oxygen Precipitates in silicon are analyzed using a modified Day–Thorpe approach [J. Phys.: Condens. Matter 11, 2551 (1999)]. The aspect ratio of the Precipitates is determined by transmission electron microscopy analysis. The reduced spectral function and the stoichiometry of the precipitate are extracted from the absorption spectra and the amount of precipitated interstitial oxygen. The experimental absorption spectra can be divided in a set with a Frohlich frequency of around 1100 cm−1 and in a set with a Frohlich frequency between 1110 and 1120 cm−1. It is shown that the shift in the Frohlich frequency is not due to a differing stoichiometry, but to the detailed structure of the reduced spectral function. Inverse modeling of the spectra suggests that the oxide Precipitates consist of substoichiometric SiOγ with γ=1.17±0.14.
