Flotation of Barite From Complex Iron Ore

The present contribution is aimed at the production of a high-grade barite concentrate front complex iron ores of ore-deposit Kremikovtzi,Bulgaria. The ores consisting main-ly of limonite, hematite and siderite have been bene-ficiated by high intensity electromagnetic wet separation on magnetic separator type Jones DP 317. Barite flotation has been succeeded from non-magnetic fraction merged with ground barite rear materials. The collecting flotation agents OMC 199 and AERO 8-15 (2:1 ratio) at the total dosage rate of 400-450 g/t have been applied. The frother OrePrep F 501 consumption has been 10-15 g/t_ Water glass has been applied as a silica depressant at the application rate of 4-4.5 kg/t. Annual output of flotation barite concentrate reach 120 000 tons. Of this quantity 75 wt. i7c are exported in bulk with total assay of BaSO4 and SrSO4 97-98 wt % and 8 wt % moisture. The rest part is dried, ground and bagged. The qualirr corresponds to OCMA (Oil Companies Material Association) /API (American Petroleum Institutes requirements

Raman scattering study of (Kx_xSr1−x_{1-x})Fe2_2As2_2 (xx = 0.0, 0.4)

Polarized Raman spectra of non-superconducting SrFe$_2$As$_2$ and superconducting K$_{0.4}$Sr$_{0.6}$Fe$_2$As$_2$ ($T_c = 37$ K) are reported. All four phonon modes (A$_{1g}$ + B$_{1g}$ + 2E$_g$) allowed by symmetry, are found and identified. Shell model gives reasonable description of the spectra. No detectable anomalies are observed near the tetragonal-to-orthorhombic transition in SrFe$_2$As$_2$ or the superconducting transition in K$_{0.4}$Sr$_{0.6}$Fe$_2$As$_2$.Comment: 4 pages, 4 figures, 2 table

Enhanced Raman Microprobe Imaging of Single-Wall Carbon Nanotubes

We explore Raman microprobe capabilities to visualize single wall carbon nanotubes (SWCNTs). Although this technique is limited to a micron scale, we demonstrate that images of individual SWCNTs, bundles or their agglomerates can be generated by mapping Raman active elementary excitations. We measured the Raman response from carbon vibrations in SWCNTs excited by confocal scanning of a focused laser beam. Carbon vibrations reveal key characteristics of SWCNTs as nanotube diameter distribution (radial breathing modes, RBM, 100-300 cm(exp -1)), presence of defects and functional groups (D-mode, 1300-1350 cm(exp -1)), strain and oxidation states of SWCNTs, as well as metallic or semiconducting character of the tubes encoded in the lineshape of the G-modes at 1520-1600 cm(exp - 1). In addition, SWCNTs are highly anisotropic scatterers. The Raman response from a SWCNT is maximal for incident light polarization parallel to the tube axis and vanishing for perpendicular directions. We show that the SWCNT bundle shape or direction can be determined, with some limitations, from a set of Raman images taken at two orthogonal directions of the incident light polarization

Comment on "Raman spectroscopy study of NaxCoO2 and superconducting NaxCoO2 yH2O"

The effect of surface degradation of the thermolectric cobaltite on Raman spectra is discussed and compared to experimental results from Co3O4 single crystals. We conclude that on NaCl flux grown NaxCoO2 crystals a surface layer of Co3O4 easily forms that leads to the observation of an intense phonon around 700 cm-1 [Phys. Rev. B 70, 052502 (2004)]. Raman spectra on freshly cleaved crystals from optical floating zone ovens do not show such effects and have a high frequency phonon cut-off at approximately 600 cm -1 [Phys. Rev. Lett 96, 167204 (2006)]. We discuss the relation of structural dimensionality, electronic correlations and the high frequency phonon cut-off of the thermolectric cobaltite.Comment: 2 pages, 1 figure, to be published in Phys. Rev. B (2007

Co-digestion of waste activated sludge and silaged mix of chicken litter and fodder beet

In order to determine the yield of methane in a Co-degradation study with different substrates. The study involved the following substrates : WAS only; WAS+silage 2:1; WAS+silage 1:1; WAS+silage 1:2. Studieed is the contents of the macro and micronutrient in the tested substrates and biogas yield after methane fermentation. It was found that major disadvantage of the BMP test is the fact that it does not provide short-term results because of it s duration, methane yield during a shorter period could be predicted by evaluating the reaction rate provided by the rate constant

Charge transfer fluctuation, d−d-wave superconductivity, and the B1gB_{1g} Raman phonon in the Cuprates: A detailed analysis

The Raman spectrum of the $B_{1g}$ phonon in the superconducting cuprate materials is investigated theoretically in detail in both the normal and superconducting phases, and is contrasted with that of the $A_{1g}$ phonon. A mechanism involving the charge transfer fluctuation between the two oxygen ions in the CuO$_2$ plane coupled to the crystal field perpendicular to the plane is discussed and the resulting electron-phonon coupling is evaluated. Depending on the symmetry of the phonon the weight of different parts of the Fermi surface in the coupling is different. This provides the opportunity to obtain information on the superconducting gap function at certain parts of the Fermi surface. The lineshape of the phonon is then analyzed in detail both in the normal and superconducting states. The Fano lineshape is calculated in the normal state and the change of the linewidth with temperature below T$_{c}$ is investigated for a $d_{x^{2}-y^{2}}$ pairing symmetry. Excellent agreement is obtained for the $B_{1g}$ phonon lineshape in YBa$_{2}$Cu$_{3}$O$_{7}$. These experiments, however, can not distinguish between $d_{x^{2}-y^{2}}$ and a highly anisotropic $s$-wave pairing.Comment: Revtex, 21 pages + 4 postscript figures appended, tp

Phonon and magnon scattering of antiferromagnetic Bi2Fe4O9

The phonon structure of antiferromagnetic Bi2Fe4O9 (space group Pbnm No. 55, TN≈240  K) was studied theoretically by calculations of lattice dynamics and experimentally between 10 and 300 K by polarized Raman spectroscopy. Most of the 12Ag+12B1g+9B2g+9B3g Raman modes were unambiguously identified. Strong second-order scattering was observed for ab-plane-confined incident and scattered light polarizations. In addition to the phonon-scattering, broad Raman bands with typical characteristics of magnon scattering appear below TN. The magnon bands are analyzed on the basis of magnetic structure of Bi2Fe4O9 and attributed to two- magnon excitations

Inelastic x-ray scattering investigations of lattice dynamics in SmFeAsO1−x_{1-x}Fy_y superconductors

We report measurements of the phonon density of states as measured with inelastic x-ray scattering in SmFeAsO$_{1-x}$F$_y$ powders. An unexpected strong renormalization of phonon branches around 23 meV is observed as fluorine is substituted for oxygen. Phonon dispersion measurements on SmFeAsO$_{1-x}$F$_y$ single crystals allow us to identify the 21 meV A$_{1g}$ in-phase (Sm,As) and the 26 meV B$_{1g}$ (Fe,O) modes to be responsible for this renormalization, and may reveal unusual electron-phonon coupling through the spin channel in iron-based superconductors.Comment: 4 pages, 3 figures, submitted for SNS2010 conference proceeding

A study of the superconducting gap in RNi2_2B2_2C (R = Y, Lu) single crystals by inelastic light scattering

Superconductivity-induced changes in the electronic Raman scattering response were observed for the RNi$_2$B$_2$C (R = Y, Lu) system in different scattering geometries. In the superconducting state, 2$\Delta$-like peaks were observed in A$_{1g}$, B$_{1g}$, and B$_{2g}$ spectra from single crystals. The peaks in A$_{1g}$ and B$_{2g}$ symmetries are significantly sharper and stronger than the peak in B$_{1g}$ symmetry. The temperature dependence of the frequencies of the 2$\Delta$-like peaks shows typical BCS-type behavior, but the apparent values of the $2\Delta$ gap are strongly anisotropic for both systems. In addition, for both YNi$_2$B$_2$C and LuNi$_2$B$_2$C systems, there exists reproducible scattering strength below the $2\Delta$ gap which is roughly linear to the frequency in B$_{1g}$ and B$_{2g}$ symmetries. This discovery of scattering below the gap in non-magnetic borocarbide superconductors, which are thought to be conventional BCS-type superconductors, is a challenge for current understanding of superconductivity in this system.Comment: Added text, changed a figure, and added references. Will appear in Phys. Rev.

Hole concentration and phonon renormalization in Ca-doped YBa_2Cu_3O_y (6.76 < y < 7.00)

In order to access the overdoped regime of the YBa_2Cu_3O_y phase diagram, 2% Ca is substituted for Y in YBa_2Cu_3O_y (y = 7.00,6.93,6.88,6.76). Raman scattering studies have been carried out on these four single crystals. Measurements of the superconductivity-induced renormalization in frequency (Delta \omega) and linewidth (\Delta 2\gamma) of the 340 cm^{-1} B_{1g} phonon demonstrate that the magnitude of the renormalization is directly related to the hole concentration (p), and not simply the oxygen content. The changes in \Delta \omega with p imply that the superconducting gap (\Delta_{max}) decreases monotonically with increasing hole concentration in the overdoped regime, and \Delta \omega falls to zero in the underdoped regime. The linewidth renormalization \Delta 2\gamma is negative in the underdoped regime, crossing over at optimal doping to a positive value in the overdoped state.Comment: 18 pages; 5 figures; submitted to Phys. Rev. B Oct. 24, 2002 (BX8292