Application of Electron Microscopy to the Electrorefining of Copper

Electron microscopy was used to characterize the fine-grained products formed during the electrorefining of copper and to elucidate the chemical processes occurring during this metallurgical process. Copper anodes and the anode slimes from the electrorefining of copper at three Canadian refineries are studied to determine the behaviour of lead and selenium and the formation of various silver-copper selenides during the electrorefining process. Silver occurs in solid solution in the copper metal and dissolves with the copper. Silver then reacts with Cu2Se to form Ag-Cu selenides. Lead is present in the anode mostly as complex Pb-As or Pb-As-Sb-Bi oxides. On exposure to the electrolyte, the lead is rapidly converted to insoluble PbSO4. Although most of the nickel in the anodes dissolves, some accumulates as NiO or Cu-Ni-Sb oxide inclusions in the anode slimes

Less than 50% sublattice polarization in an insulating S=3/2 kagome' antiferromagnet at low T

We have found weak long range antiferromagnetic order in the quasi-two-dimensional insulating oxide $KCr_3(OD)_6(SO_4)_2$ which contains Cr$^{3+}$ S=3/2 ions on a kagom\'{e} lattice. In a sample with $\approx$ 76% occupancy of the chromium sites the ordered moment is 1.1(3)$\mu_B$ per chromium ion which is only one third of the N\'{e}el value $g\mu_BS=3\mu_B$. The magnetic unit cell equals the chemical unit cell, a situation which is favored by inter-plane interactions. Gapless quantum spin-fluctuations ($\Delta/k_B >$T_N$= 1.6K are the dominant contribution to the spin correlation function,$S(Q,\omega)$ in the ordered phase.Comment: 18 pages, RevTex/Latex, with 6 figure

Determination of the single-ion anisotropy energy in a S = 5/2 kagome antiferromagnet using x-ray absorption spectroscopy

We report x-ray absorption and x-ray linear dichroism measurements at the Fe L-2,L-3 edges of the geometrically frustrated systems of potassium and hydronium iron jarosite. Comparison with simulated spectra, involving ligand-field multiplet calculations modeling the 3d-2p hybridization between the iron ion and the oxygen ligands, has yielded accurate estimates for the ligand metal-ion hybridization and the resulting single-ion crystal-field anisotropy energy. Using this method we provide an experimentally verified scenario for the appearance of a single-ion anisotropy in this nominally high-spin 3d(5) orbital singlet S-6 system, which accounts for features of the spin-wave dispersion in the long-range-ordered ground state of potassium iron jarosite

Mossbauer mineralogy of rock, soil, and dust at Meridiani Planum, Mars: Opportunity's journey across sulfate-rich outcrop, basaltic sand and dust, and hematite lag deposits

The Mössbauer (MB) spectrometer on Opportunity measured the Fe oxidation state, identified Fe-bearing phases, and measured relative abundances of Fe among those phases at Meridiani Planum, Mars. Eight Fe-bearing phases were identified: jarosite (K,Na,H3O)(Fe,Al)(OH)6(SO4)2, hematite, olivine, pyroxene, magnetite, nanophase ferric oxides (npOx), an unassigned ferric phase, and metallic Fe (kamacite). Burns Formation outcrop rocks consist of hematite-rich spherules dispersed throughout S-rich rock that has nearly constant proportions of Fe3+ from jarosite, hematite, and npOx (29%, 36%, and 20% of total Fe). The high oxidation state of the S-rich rock (Fe3+/FeT ~ 0.9) implies that S is present as the sulfate anion. Jarosite is mineralogical evidence for aqueous processes under acid-sulfate conditions because it has structural hydroxide and sulfate and it forms at low pH. Hematite-rich spherules, eroded from the outcrop, and their fragments are concentrated as hematite-rich soils (lag deposits) on ripple crests (up to 68% of total Fe from hematite). Olivine, pyroxene, and magnetite are primarily associated with basaltic soils and are present as thin and locally discontinuous cover over outcrop rocks, commonly forming aeolian bedforms. Basaltic soils are more reduced (Fe3+/FeT ~ 0.2–0.4), with the fine-grained and bright aeolian deposits being the most oxidized. Average proportions of total Fe from olivine, pyroxene, npOx, magnetite, and hematite are 33%, 38%, 18%, 6%, and 4%, respectively. TheMB parameters of outcrop npOx and basaltic-soil npOx are different, but it is not possible to infer mineralogical information beyond octahedrally coordinated Fe3+. Basaltic soils at Meridiani Planum and Gusev crater have similar Fe-mineralogical compositions.Additonal co-authors: P Gütlich, E Kankeleit, T McCoy, DW Mittlefehldt, F Renz, ME Schmidt, B Zubkov, SW Squyres, RE Arvidso