| 1. |
- Bo, Qi-Bing, et al.
(författare)
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A new family of 3D 3d-4f heterometallic frameworks comprising 1D inorganic lanthanide ladders and organic Cu-bipyridine chains
- 2008
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 10:2, s. 232-238
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Tidskriftsartikel (refereegranskat)abstract
- A new family of the 3D heterometallic coordination polymers [{Ln2(SO4)2(H2O)2(pydc)2Cu2 (bpy)2·2(H2O)}]n (Ln = Sm ( 1), Eu ( 2), Gd ( 3), Tb ( 4) and Dy ( 5); pydc = 2,6-pyridine-dicarboxylate anion; bpy= 4,4-bipyridine) have successfully been synthesized under solvothermal conditions (H2O/ethanol). All the coordination polymers obtained were characterized by elemental analysis, FT-IR analysis, differential thermal analysis/thermogravimetry (DTA/TG), fluorescent spectra and single crystal X-ray diffraction analysis. The most intriguing structural feature is that all the compounds exhibit 3D frameworks with 1D inorganic lanthanide ladders and organic CuI-bipyridine chains, which represent two types of 3d/4f coordination polymers (form I: Ln = Sm and Eu; form II: Ln = Gd, Tb and Dy) as the result of a so-called gadolinium break effect. Additionally, compounds 2 and 4 showed the characteristic emission spectra of the EuIII and TbIII ions, respectively, and appeared to have good fluorescence properties, while 1, 3 and 5 emitted fluorescence resembling CuI complexes. To our knowledge, the investigation of the
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| 2. |
- Bredyuk, O. A., et al.
(författare)
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Structural organization of cadmium(II) and copper(II) dithiocarbamate complexes with dialkyl-substituted and cyclic ligands: Synthesis, single-crystal X-ray diffraction, EPR, and CP/MAS13C, 15N, and 113Cd NMR
- 2005
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Ingår i: Russian Journal of Inorganic Chemistry. - 0036-0236 .- 1531-8613. ; 50:11, s. 1710-1726
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Tidskriftsartikel (refereegranskat)abstract
- A comparative study of polynuclear thallium complexes with dialkyldithiocarbamates [Tl2{S2CNR2} 2]n (R = CH3, i-C3H7, C4H9, and i-C4H9; R2 = (CH2)6) was performed by solid-state 13C and 15N CP/MAS NMR spectroscopy. The dithiocarbamate groups were found to be structurally equivalent in the complexes studied. An increase in the positive inductive effect of alkyl substituents at the N atom increased 15N chemical shifts as a result of a combination of positive inductive effect of the alkyl substituents and the mesomeric effect of =NC(S)S-groups. The first representative of thallium(I) complexes with a cyclic dithiocarbamate ligand [Tl2{S2CN(CH2) 6}2]n was obtained. Its molecular structure was determined from X-ray diffraction data. The β-form of the isotope-substituted complex [63/65CuTl2{S 2CN(CH2)6}4] was obtained and examined by EPR spectroscopy. The EPR spectra were modeled at the second order of the perturbation theory. The spin density at the thallium atoms was calculated and its distribution over the AOs of thallium was determined.
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| 3. |
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| 4. |
- Casellas, D., et al.
(författare)
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On the transformation toughening of Y-ZrO2 ceramics with mixed Y-TZP/PSZ microstructures
- 2001
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 21:6, s. 765-777
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Tidskriftsartikel (refereegranskat)abstract
- Heat treatment of Y-TZP at high temperatures produces materials with a mixed Y-TZP/PSZ phase assemblage, which exhibit a unique combination of high mechanical strength and fracture toughness, uncommon in zirconia ceramics. The microstructure and crack growth resistance of the Y-TZP/PSZ materials developed by treating at 1650°C in air a fine-grained Y-TZP was studied. XRD as well as Raman spectroscopy results indicate that the obtained microstructure allow the retention of large tetragonal grains (up to ˜4 μm), resulting in both phase transformability enhancement and pronounced R-curve behavior. The large transformation zone, discerned from accurate measurements with Raman microprobe spectroscopy, sustains the above assessment and points out tetragonal to monoclinic phase transformation as the main toughening mechanism in the investigated Y-TZP/PSZ microstructures. This was confirmed by satisfactory agreement between the transformation toughening estimated from numerical analysis and the crack shielding experimentally determined from the R-curve measurements.
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| 5. |
- Chanturiya, Valentine, et al.
(författare)
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The effect of crystallochemical peculiarities of nickel sulphide minerals on flotation of copper-nickel ore
- 2004
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Ingår i: International Journal of Mineral Processing. - : Elsevier BV. - 0301-7516 .- 1879-3525. ; 74:1-4, s. 289-301
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Tidskriftsartikel (refereegranskat)abstract
- Flotation kinetics of pentlandite and violarite contained in copper-nickel ores and the effect of crystallochemical peculiarities of the minerals on their flotation features are studied. Studies of the effect of pentlandite crystallochemical features on its flotation properties have shown that the easiest to float is nickel-enriched pentladite, cobalt-enriched one being somewhat worse the worst being iron-enriched one. Pentlandite was found to be much better recovery to flotation concentrates than violarite. So, the process of violaritization of the surface of pentlandite grains, which may occur during the flotation, will negatively affect its characteristics.
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| 6. |
- Du, Qing, et al.
(författare)
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Acid-base properties of aqueous illite surfaces
- 1997
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 187:1, s. 221-231
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the acid-base properties of illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous illite surfaces, two surface protonation models are proposed: (1) one site-one pKamodel, ≡SOH ≡SO-+ H+, pKaint= 4.12-4.23; (2) two sites-two pKas model, ≡SIOH ≡SIO-+ H+, pKintaI= 4.17-4.44, and ≡SIIOH ≡SIIO-+ H+, [dipKintaII= 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the illite surfaces, they suggest that the surface behavior of the illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.
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| 7. |
- Du, Qing, et al.
(författare)
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Adsorption of copper at aqueous illite surfaces
- 1997
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 187:1, s. 232-242
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free illite suspensions can be explained by the formation of mononuclear surface complexes, ≡SOCu+ and ≡SOCuOH, and a multinuclear surface complex, ≡SOCu2(OH)2+, followed by the formation of a bulk precipitate, Cu(OH)2(s), or a surface precipitate, ≡SOCu2(OH)3(sp). For the illite suspensions containing carbonates, we propose that the copper-illite interaction can be depicted by the formation of mononuclear surface complexes, ≡SOCu+and ≡SOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu2(OH)2CO3(s), rather than a copper hydroxide precipitate. The existence of Cu2(OH)2CO3(s) in the carbonate-containing illite suspensions was identified by FT-IR analysis.
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| 8. |
- Du, Qing, et al.
(författare)
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Complexations in illite–fulvic acid–Cu2+ systems
- 1999
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Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 33:3, s. 693-706
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Tidskriftsartikel (refereegranskat)abstract
- As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous illite surfaces and the complexation of heavy metal copper(II) in illite-FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2-FA and montmorillonite-FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in illite-FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA-Cu2+ and illite-Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various illite-FA-Cu2+ systems.
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| 9. |
- Dyer, Chris D., et al.
(författare)
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The Raman spectroscopy of cement minerals under 1064 nm excitation
- 1993
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Ingår i: Spectrochimica Acta. Part A, Molecular Spectroscopy. - 0584-8539. ; 49:5-6, s. 715-722
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Tidskriftsartikel (refereegranskat)abstract
- The prospects for near-IR-excited Raman scattering from cement minerals are discussed, and a very unusual result concerning the intensity of the spectra is presented.
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| 10. |
- Dyer, Chris, et al.
(författare)
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Surface hydration of aqueous γ-Al2O3 studied by Fourier transform Raman and infrared spectroscopy—I. Initial results
- 1993
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Ingår i: Spectrochimica Acta. Part A, Molecular Spectroscopy. - 0584-8539. ; 49:5-6, s. 691-705
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Tidskriftsartikel (refereegranskat)abstract
- The hydration of γ-Al2O3 has been studied by Fourier transform (FT) Raman and infrared (IR) spectroscopy, and by X-ray diffraction (XRD). The initial findings are presented, along with a discussion of the possible causes for the major spectral changes that occur after hydration. The aims of the study and ongoing research are described.
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