| 1. |
- Al-Hinai, A. T., et al.
(författare)
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Application of Eh-pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media
- 2014
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Ingår i: Materials research bulletin. - : Elsevier. - 0025-5408 .- 1873-4227. ; 49:1, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO3) particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a solution containing stoichiometric amounts of Zn2+ and Sn4+ was controlled for the precipitation in a one pot synthesis step at room temperature (25 degrees C). The effect of the concentration of the reactants on the particle size was studied by varying the concentration of the precursor (Zn2+ + Sn4+) solution. Scanning electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-organization olnano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and thermo gravimetric analysis (TGA) show that the particles are in ZnSnO3.3H(2)O form.
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| 2. |
- Baykal, A., et al.
(författare)
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Effect of ionic liquids on the electrical and magnetic performance of polyaniline-nickel ferrite nanocomposite
- 2013
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 48:2, s. 378-382
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Tidskriftsartikel (refereegranskat)abstract
- Polyaniline-NiFe2O4 nanofiber composites were successfully synthesized at the interface of water and ionic liquid via in situ polymerization using cetyl trimethylammonium bromide (CTAB) as surfactant. Both TG analysis and FT-IR measurements proved the presence of organic layer on the surface of NiFe2O4 nanoparticles. The influence of 1-butyl-3-methyl-imidazolium bromide [BMIM]Br as ionic liquid on the structure, conductivity and magnetic property of polyaniline-NiFe2O 4-CTAB nanocomposite were studied in detail. The results show that imidazolium-based ionic liquids BMIMBr acts as an anchor agent for the formation of morphology in polyaniline-NiFe2O4-CTAB nanocomposite. Introduction of ionic liquids obviously improves the conductivity but weakens the magnetization of polyaniline-NiFe2O4 nanocomposite.
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| 3. |
- Chandar, Nagamuthu Krishna, et al.
(författare)
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Structural, morphological and optical properties of solvothermally synthesized Pr(OH)(3) nanoparticles and calcined Pr6O11 nanorods
- 2014
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 50, s. 417-420
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Tidskriftsartikel (refereegranskat)abstract
- The structural, morphological and optical properties of solvothermally synthesized Pr(OH)(3) nanoparticles and calcined Pr6O11 nanorods have been studied. Pr6O11 nanorods were grown by subsequent thermal decomposition of the synthesized Pr(OH)(3) nanoparticles at 700 degrees C for 2 h. Structural analysis showed that the synthesized Pr(OH)(3) nanoparticles possess hexagonal phase and calcined Pr6O11 nanorods have cubic fluorite phase. HRSEM images revealed that the Pr6O11 sample contains well-defined rod-like morphology. The UV-vis absorbance study of Pr6O11 nanorods showed shapedependent absorption edge toward higher wavelength as compared to Pr(OH)(3) nanoparticles. The PL spectrum of Pr6O11 nanorods reveals the enhanced near-band-edge emission in the blue region, with significant defect level green emission. The mechanism for the formation of Pr6O11 nanorods from Pr(OH)(3) nanoparticles has been proposed.
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| 4. |
- Deligoz, H., et al.
(författare)
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Synthesis, structural and electrical properties of triethylene glycol (TREG) stabilized Mn0.2Co0.8Fe2O4 NPs
- 2012
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:3, s. 537-543
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Tidskriftsartikel (refereegranskat)abstract
- Triethylene glycol (TREG) stabilized Mn0.2Co0.8Fe2O4 NPs was synthesized by a glycothermal reaction. XRD analysis identified the product as Mn0.2Co0.8Fe2O4 with a high phase purity. Nano-sized particles with an average size of about 6-8 nm were obtained with nearly single crystalline nature with TEM analysis. Superparamagnetic-like behavior of TREG stabilized Mn0.2Co0.8Fe2O4 NPs was observed by VSM. The binding between TREG and Mn0.2Co0.8Fe2O4 NPs was investigated with FT-IR and found to be via O on the TREG and NP surface. TG analysis indicated that the Mn0.2Co0.8Fe2O4 NP content was about 40%, with a TREG-shell content to be around 60%. Overall conductivity of the nanocomposite is in the range of 10(-10) to 10(-7) S cm(-1) with a strong dependence on temperature and frequency, indicating ionic conductivity. The nanocomposite exhibited lower epsilon' and epsilon '' compared to TREG stabilized Mn0.2Co0.8Fe2O4 NPs due to the doping of co-doping of manganese and cobalt.
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| 5. |
- Deligöz, H., et al.
(författare)
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Synthesis, structural, magnetic and electrical properties of Co 1-xZnxFe2O4 (x = 0.0, 0.2) nanoparticles
- 2013
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 48:2, s. 646-654
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Tidskriftsartikel (refereegranskat)abstract
- Co1-xZnxFe2O4 spinel nanoparticles with Zn concentrations of x = 0.0, 0.2 were prepared by a hydrothermal route in the presence of triethylene glycol (TEG). The structural, magnetic, electrical and dielectric properties of the prepared nanoparticles were studied. The XRD results confirmed the formation of single spinel ferrite structure with crystallite size 9 and 10 nm for x = 0.0 and 0.2 compositions respectively. The lattice parameter (a) increased with increasing Zn concentration. Temperature and frequency dependent electrical and dielectric properties of the prepared ferrites have also been investigated. Our findings show that overall conductivity of Co0.8Zn0.2Fe 2O4 nanoparticle is lower than that of CoFe 2O4 and roughly in the range of 10-11-10 -7 S cm-1 depending strongly temperature and frequency owing to the formation of stable electric bonds between the Zn2+ and Fe2+ ions, which localizes Fe2+ charge carriers. The ac conductivity showed a temperature dependent behavior at low frequencies and temperature independent behavior at high frequencies, which is an indication of ionic conductivity. dc conductivity of Co0.8Zn0.2Fe 2O4 nanoparticle are found to obey the Arrhenius plot and can be classified into two regions over with activation energy of 0.113 and 0.163 eV in the ranges of 20-40 °C and 70-120 °C, respectively when CoFe2O4 has an activation energy of 0.245 eV.
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| 6. |
- Dom, R., et al.
(författare)
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Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying
- 2012
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Ingår i: Materials research bulletin. - 0025-5408 .- 1873-4227. ; 47:3, s. 562-570
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of pure spinel phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor conditions (7 < pH ≤ 10) were found to favor oxide film formation. The nanostructured films produced under optimized conditions, with 500 mM solution at pH ∼ 8.0, yielded pure cubic phase ZnFe 2O 4 film. Very high/low precursor concentrations yielded mixed phase, less adherent, and highly inhomogeneous thin films. Desired spinel phase was achieved in as-deposited condition under appropriately controlled spray conditions and exhibited a band gap of ∼1.9 eV. The highly porous nature of the films favored its photocatalytic performance as indicated by methylene blue de-coloration under solar radiation. These immobilized films display good potential for visible light photocatalytic applications. © 2012 Elsevier Ltd. All rights reserved.
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| 7. |
- Erdemi, H., et al.
(författare)
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Synthesis and conductivity studies of piperidine-4-carboxylic acid functionalized Fe 3O 4 nanoparticles
- 2012
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:9, s. 2193-2199
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Tidskriftsartikel (refereegranskat)abstract
- Piperidine-4-carboxylic acid (PPCA) functionalized Fe 3O 4 nanoparticles as a novel organic-inorganic hybrid was fabricated and characterized by XRD, FT-IR, VSM, and TEM techniques. Its detailed electrical properties are also presented. Composition was determined as Fe 3O 4, while particles were observed to have spherical morphology. VSM measurement proved the super-paramagnetic property of the as synthesized nanocomposite. ac and dc conductivity measurements indicated semiconductor characteristics and changing trends with temperature because of reorganization of the nanocomposite. dc conductivity is strongly temperature dependent and is classified into three regions. Analysis of the real and imaginary parts of the permittivity of nanocomposite showed the ionic polarization mechanism consisting of ionic conductivity and interfacial polarization.
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| 8. |
- Günay, M., et al.
(författare)
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Triethylene glycol stabilized MnFe2O4 nanoparticle : Synthesis, magnetic and electrical characterization
- 2013
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 48:3, s. 1057-1064
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Tidskriftsartikel (refereegranskat)abstract
- In this study, triethylene glycol (TEG) stabilized superparamagnetic MnFe2O4 nanoparticle (TEG@Mn-Fe2O4) was synthesized via a simple polyol route. Composition of nanoparticle was confirmed as MnFe2O4 and surface conjugation of TEG was confirmed by Fourier transform infrared spectroscopy to be via oxygens on TEG covalently attached to metal centers on the NPs: Vibrating sample magnetometer measurements confirmed the superparamagnetic character of these nanoparticles without reaching to a saturation, and has no coercivity. The TEG@MnFe2O4 nanocomposite showed thermally activated conductivity, significant interfacial polarization effect also in the dielectric permittivity evaluations. Temperature dependency of conductivity is a strong evidence for thermally activated polarization mechanism. dc conductivity is classified into two regions over a limited temperature range and shows maximum conductivity of about 4 x 10(-7) S cm(-1) at 120 degrees C. Temperature and frequency dependence of dielectric permittivity indicated interfacial polarization and temperature-assisted-reorganization effects.
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| 9. |
- Ivanov, Sergey A., et al.
(författare)
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Chemical pressure effects on structural, dielectric and magnetic properties of solid solutions Mn3-xCoxTeO6
- 2014
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 50, s. 42-56
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Tidskriftsartikel (refereegranskat)abstract
- The effects of Co2+ doping on the structural, magnetic and dielectric properties of the multiferroic frustrated antiferromagnet Mn3TeO6 have been investigated. Ceramic samples of the solid solution series Mn3-xCoxTeO6 were prepared by a solid-state reaction route. X-ray and neutron powder diffraction and electron microscopy techniques were combined with calorimetric, dielectric and magnetic measurements to investigate the dependence of the crystal structure and physical properties on temperature and composition. It is shown that the compounds with x <= 2.4 adopt the trigonal corundum-related structure of pure Mn3TeO6 (space group 18) in the temperature range 5-295 K and that the lattice parameters a and c and the unit-cell volume V decrease linearly with increasing Co2+ concentration. The low-temperature magnetic susceptibility and heat capacity data evidence the antiferromagnetic ordering of all samples. The Neel temperature linearly increases with Co2+ concentration x. Curie-Weiss fits of the high temperature susceptibility indicate that the magnetic frustration decreases with x. The derived magnetic structure of Mn3TeO6 can be described as an incommensurately modulated magnetic spin state with k = [0, 0, k(z)] and an elliptical spin-spiral order of spins within the chains of MnO6 octahedra. With increasing Co2+ concentration the propagation vector kz changes from 0.453 (x = 0) to 0.516 (x = 2.4). The magnetic anisotropy changes as well, leading to a reorientation of the spiral-basal plane. A possible coexistence of long-range order of electrical dipoles and magnetic moments in Mn3-xCoxTeO6 is discussed.
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| 10. |
- Ivanov, Sergey A., et al.
(författare)
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New type of incommensurate magnetic ordering in Mn(3)TeO(6)
- 2011
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 46:11, s. 1870-1877
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Tidskriftsartikel (refereegranskat)abstract
- The complex metal oxide Mn(3)TeO(6) exhibits a corundum related structure and has been prepared both in forms of single crystals by chemical transport reactions and of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric and magnetic measurements. At room temperature this compound adopts a trigonal structure, space group R (3) over bar with a = 8.8679(1) angstrom. c = 10.6727(2) angstrom. A long-range magnetically ordered state is identified below 23 K. An unexpected feature of this magnetic structure is several types of Mn-chains. Under the action of the incommensurate magnetic propagation vector k = [0, 0, 0.4302(1)] the unique Mn site is split into two magnetically different orbits. One orbit forms a perfect helix with the spiral axis along the c-axis while the other orbit has a sine wave character along the c-axis.
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| 11. |
- Ivanov, Sergey A., et al.
(författare)
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Preparation, structural, dielectric and magnetic properties of LaFeO3-PbTiO3 solid solutions
- 2012
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:11, s. 3253-3268
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Tidskriftsartikel (refereegranskat)abstract
- Solid solutions of (1−x)LaFeO3–(x)PbTiO3 (0 < x < 1) have been prepared by conventional solid-state reaction. These complex perovskites have been studied by means of X-ray (XRPD) and neutron powder (NPD) diffraction, complemented with dielectric, magnetic, heat capacity and Mössbauer measurements. Complete solubility in the perovskite series was demonstrated. The NPD and XRPD patterns were successfully refined as orthorhombic (x ≤ 0.7) and tetragonal (x ≥ 0.8). A composition-driven phase transformation occurs within the interval 0.7 < x < 0.8. The samples with x < 0.5 showed evidence of long-range magnetic ordering with an G-type antiferromagnetic arrangement of the magnetic moments of the Fe3+ cations in the B-site with propagation vector k = (0,0,0). Based on the obtained experimental data, a combined structural and magnetic phase diagram has been constructed. The factors governing the structural, dielectric and magnetic properties of (1−x)LaFeO3–(x)PbTiO3 solid solutions are discussed, as well as their possible multiferroicity.
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| 12. |
- Ivanov, Sergey A., et al.
(författare)
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Temperature-dependent multi-k magnetic structure in multiferroic Co3TeO6
- 2012
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:1, s. 63-72
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Tidskriftsartikel (refereegranskat)abstract
- A complex magnetic order of the multiferroic compound Co(3)TeO(6) has been revealed by neutron powder diffraction studies on ceramics and crushed single crystals. The compound adopts a monoclinic structure (s.g. C2/c) in the studied temperature range 2-300 K but exhibits successive antiferromagnetic transitions at low temperature. Incommensurate antiferromagnetic order with the propagation vector k(1) = (0, 0.485, 0.055) sets in at 26 K. A transition to a second antiferromagnetic structure with k(2) = (0, 0, 0) takes place at 21.1 K. Moreover, a transition to a commensurate antiferromagnetic structure with k(3) = (0, 0.5, 0.25) occurs at 17.4 K. The magnetic structures have been determined by neutron powder diffraction using group theory analysis as a preliminary tool. Different coordinations of the Co(2+) ions involved in the low-symmetry C2/c structure of Co(3)TeO(6) render the exchange-interaction network very complex by itself. The observed magnetic phase transformations are interpreted as an evidence of competing magnetic interactions. The temperature dependent changes in the magnetic structure, derived from refinements of high-resolution neutron data, are discussed and possible mechanisms connected with the spin reorientations are described.
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| 13. |
- Jalilian, Ehsan, et al.
(författare)
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Luminescence properties of monoclinic Cu4I4(Piperidine)4
- 2011
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Ingår i: Materials research bulletin. - : Elsevier Ltd.. - 0025-5408 .- 1873-4227. ; 46:8, s. 1192-1196
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Tidskriftsartikel (refereegranskat)abstract
- A new modification of Cu4I4Pip4 has been synthesized under hydrothermal conditions. X-ray crystallography revealed that this compound crystallized in the monoclinic system and consists of a tetrahedral core with composition Cu4I4, in which each Cu atom is coordinated by a piperidine molecule via the N atom. In contrast to a previously reported modification of Cu4I4Pip4, the present modification shows luminescent properties when exposed to UV-light. In addition, we have used time-dependent density functional theory calculations to characterize both compounds in term of both absorption and emission.
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| 14. |
- Jeon, So-hyoun, et al.
(författare)
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Selective control of wetting on various substrates
- 2014
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Ingår i: Materials research bulletin. - : Elsevier Ltd. - 0025-5408 .- 1873-4227. ; 58, s. 32-34
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Tidskriftsartikel (refereegranskat)abstract
- Selective control of wetting is highly demanded for a broad window of applications. To selectively control wetting a surface should be locally modified by structuring surfaces or modulating surface chemistry. However, the local modifications are still challenging due to their complex and expensive processes. In this report we demonstrate the development of a facile approach for selective control of wetting on various substrates. Taking superhydrophobic polypropylene particles and hydrophilic silica nanoparticles, we here show that the locally controlled wetting can be achieved by coating the particles on a wide range of substrates including metal and paper and be applied to microfluidic channels. Furthermore, we represent that the coating method can be applied to any surfaces regardless of compositions and geometries.
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| 15. |
- Karaoglu, E., et al.
(författare)
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Synthesis and characterization of Piperidine-4-carboxylic acid functionalized Fe 3O 4 nanoparticles as a magnetic catalyst for Knoevenagel reaction
- 2012
-
Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:9, s. 2480-2486
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Tidskriftsartikel (refereegranskat)abstract
- Piperidine-4-carboxylic acid (PPCA) functionalized Fe 3O 4 nanoparticles as a novel organic-inorganic hybrid heterogeneous catalyst was fabricated and characterized by XRD, FT-IR, TGA, TEM and VSM techniques. Composition was determined as Fe 3O 4, while particles were observed to have spherical morphology. Size estimations using X-ray line profile fitting (10 nm), TEM (11 nm) and magnetization fitting (9 nm) agree well, revealing nearly single crystalline character of Fe 3O 4 nanoparticles. Magnetization measurements reveal that PPCA functionalized Fe 3O 4 NPs have superparamagnetic features, namely immeasurable coercivity and absence of saturation. Small coercivity is established at low temperatures. The catalytic activity of Fe 3O 4-PPCA was probed through one-pot synthesis of nitro alkenes through Knoevenagel reaction in CH 2Cl 2 at room temperature. The heterogeneous catalyst showed very high conversion rates (97%) and could be recovered easily and reused many times without significant loss of its catalytic activity.
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| 16. |
- Kars, Mohammed, et al.
(författare)
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Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS1-xSex)(1.16)(Nb1.036S2)(2)
- 2010
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 45:8, s. 982-988
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Tidskriftsartikel (refereegranskat)abstract
- In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS1-xSex)slabs stacking alternately with double NbS2 layers and both can be treated as separate monoclinic subsystems. The (SbS1-xSex) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of (SbX5) square pyramids joined by edges (X: S, Se); the NbS2 layers consist of (SbX5) trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS2 structure type. Both sublattices have the same lattice parameters a = 5.7672(19) angstrom, c = 17.618(6) angstrom and beta = 96.18(3)degrees, with incommensurability occurring along the b direction: b(1) = 3.3442(13) angstrom for the NbS2 subsystem and b(2) = 2.8755(13) angstrom for the (SbS1-xSex) subsystem. The occurrence of diffuse scattering intensity streaked along c* indicates that the (SbS1-xSex) subsystem is subjected to extended defects along the stacking direction.
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| 17. |
- Lane, Nina J., et al.
(författare)
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High-temperature stability of alpha-Ta(4)AlC(3)
- 2011
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Ingår i: Materials research bulletin. - : Elsevier Science B.V., Amsterdam.. - 0025-5408 .- 1873-4227. ; 46:7, s. 1088-1091
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Tidskriftsartikel (refereegranskat)abstract
- Cold-pressed alpha-Ta(4)AlC(3) powders were annealed up to 1750 degrees C to test first-principles predictions of alpha-beta phase-stability reversal at 1600 degrees C. Up to 1600 degrees C, the alpha-Ta(4)AlC(3) samples were stable with no indications of any alpha-beta transformation, as shown by the strong characteristic X-ray diffraction peaks of alpha-Ta(4)AlC(3) and the zigzag stacking observed by transmission electron microscopy. These results show that, in this experimental situation, high temperature alone is not sufficient to cause the alpha-beta transformation.
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| 18. |
- Leone, Stefano, 1978-, et al.
(författare)
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Growth of smooth 4H-SiC epilayers on 4° off-axis substrates with chloride-based CVD at very high growth rate
- 2011
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Ingår i: Materials research bulletin. - : Elsevier. - 0025-5408 .- 1873-4227. ; 46:8, s. 1272-1275
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Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC epilayers grown on 4º off-axis substrates at high rates usually suffer from step-bunching (very high surface roughness) or of extended triangular defects, both detrimental for device performance. In this study we developed a novel in situ pre-growth surface preparation based on hydrogen chloride (HCl) addition at a temperature higher than that used for the growth. This pre-growth etching procedure minimizes the density of triangular defects which usually occur at low temperatures and simultaneously enables growth at a temperature low enough to avoid stepbunching. Thanks to this surface preparation step, chloride-based CVD could be used for rapid epitaxial growth of high quality layers. In this study, layers were grown at rates of 100 μm/h yielding defect free epitaxial layers with very smooth surface (RMS value of 8.9 Å on 100x100 μm2 area).
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| 19. |
- Shafiu, S., et al.
(författare)
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Facile synthesis of PVA-MnFe2O4 nanocomposite : Its magnetic investigation
- 2013
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 48:10, s. 4066-4071
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Tidskriftsartikel (refereegranskat)abstract
- Manganese ferrite (MnFe2O4)-polyvinyl alcohol (PVA) nanocomposite was prepared by a PVA assisted sot-gel auto-combustion method. The magnetic core of the carriers was manganese ferrite (MnFe2O4), with average crystallite size of 9.1 +/- 2.1 nm. The PVA-MnFe2O4 nanocomposite exhibited superparamagnetic behavior at room temperature and ferromagnetic behavior at low temperatures. Zero-field-cooled and field-cooled measurements further confirm the superparamagnetic behavior with a blocking temperature of 160 K. The lower reduced remanent magnetization values than theoretical value of 0.5 indicate that the PVA/MnFe2O4 nanocomposite used in this study has uniaxial anisotropy rather than the expected cubic anisotropy according to the Stoner-Wohlfarth model. The calculated magnetic anisotropy constant of the sample is similar to 1.45 x 10(6) erg/cm(3) which is significantly higher than that of the bulk MnFe2O4 due to the strong magnetic coupling between magnetic core and surface spins.
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| 20. |
- Svensson, Gunnar, 1960-, et al.
(författare)
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Synthesis and characterisation of the novel double perovskites La2CrB2/3Nb1/3O6, B = Mg, Ni, Cu
- 2012
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:9, s. 2449-2454
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Tidskriftsartikel (refereegranskat)abstract
- The novel perovskites La2CrB2/3Nb1/3O6, B = Mg, Ni, and Cu have been synthesised at 1350 degrees C in air via the citrate route. Rietveld refinements using neutron powder diffraction (NPD) data showed that the compounds adopt the GdFeO3 type structure with space group Pbnm, and unit cell parameters a approximate to b approximate to root 2 x a(p) and c approximate to 2 x a(p), where a(p) approximate to 3.8 angstrom. Selected area electron diffraction (SAED) of B = Ni and Cu samples confirmed space group Pbnm. However, distinct reflections forbidden in Pbnm symmetry, but allowed in the monoclinic sub-group P2(1)/n and unit cell parameters a approximate to b approximate to root 2 x a(p) and c approximate to 2 x a(p), beta approximate to 90 degrees were present in SAED patterns of B = Mg sample. This indicates an ordering of the B-cations within the crystal structure of La2CrMg2/3Nb1/3O6. High-resolution electron microscopy (HREM) study indicating uniform, without formation of clusters, ordering of B-cations in the crystallites of La2CrMg2/3Nb1/3O6. Magnetic susceptibility measurements show that the compounds are antiferromagnetic (with some glass or spin clustering effects due to additional ferromagnetic interactions between the B-cations) with T-N for La2CrB2/3Nb1/3O6, B = Mg, Ni, Cu being 90, 125 and 140K, respectively.
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| 21. |
- Wang, Cao, et al.
(författare)
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Transparent polycrystalline ruby ceramic by spark plasma sintering
- 2010
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 45:9, s. 1127-1131
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Tidskriftsartikel (refereegranskat)abstract
- Fine-grained and transparent polycrystalline ruby ceramics (Cr2O3-doped Al2O3) were successfully prepared by spark plasma sintering (SPS). The effect of Cr2O3 concentration on the grain size, hardness, fracture toughness and thermal conductivity of ruby ceramics was investigated systematically. For 0.05 wt.% Cr2O3, high in-line transmittance of 85% at 2000 nm can be reached, further increase of Cr2O3 concentration leads to the decrease in transmittance. High hardness of 23.95-25.05 GPa can be achieved due to the fine grain size in all ruby ceramics. The fracture toughness of 1.9-2.29 MPa m(1/2) indicates that no improvement in fracture toughness over pure Al2O3 can be obtained by Cr2O3 doping in these submicron grained ruby ceramics. High thermal conductivity of 28-29.8 W/(m K) at room temperature, close to that of single crystal sapphire, can be achieved. The change in grain size for different Cr2O3 concentrations is the major reason for the change in mechanical and thermal properties, but not for the change in optical properties.
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| 22. |
- Wang, Dandan, et al.
(författare)
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Ultrafast carrier dynamics of near-band-edge emission in single-crystal ZnO nanorods
- 2011
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Ingår i: Materials research bulletin. - : Elsevier Science B.V., Amsterdam.. - 0025-5408 .- 1873-4227. ; 46:6, s. 937-940
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Tidskriftsartikel (refereegranskat)abstract
- We report on rational synthesis and optical characteristics of highly crystallined ZnO nanorods which were grown by a facile chemical vapor transport method. Temperature-dependent photoluminescence spectra of as-fabricated ZnO nanorods are dominated by near-band-edge emission with a characteristic fine structure due to high crystallinity. Furthermore, the recombination emission involving carrier dynamics of near-band-edge emission in ZnO nanorods was systematically investigated by temperature-dependent time-resolved photoluminescence spectroscopy. Recombination peaks pertaining to the exciton emissions are monitored and resolved in both temporal and spatial regimes.
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| 23. |
- Eriksson, Annika, 1975, et al.
(författare)
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Phase stability study of Bi0.15Sr0.85-xAexCoO3-δ (x = 0 and Ae = Ba0.28; Ca0.17) perovskites by in-situ neutron diffraction
- 2010
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 45:12, s. 1875-1882
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen deficient perovskites, Bi0.15Sr0.85-xAexCoO3-δ, x = 0 and Aex = Ba0.28, Ca0.17, were studied with in-situ neutron powder diffraction and combined TGA/DSC in order to investigate their behaviour at elevated temperatures in oxidising conditions. The phase stability of the I4/mmm supercell structure adopted by Bi0.15Sr0.85CoO3-δ is shown to be dependent on temperature and the oxygen content of the phase, with three structural events, at T 250, 590 and 880 °C, detected. The first transition occurs as the perovskite supercell vanishes due to oxygen absorption; the second transition is also associated with oxidation and involves the decomposition of the perovskite phase via an exothermic process to yield a dominant hexagonal phase. Finally, at T 900 °C the perovskite phase re-forms. For the Ba and Ca containing materials the decomposition to the hexagonal phase occurs at T 600 °C and 650 °C respectively. The presence of Ca at the A-site is found to stabilise the I4/mmm supercell structure in the range RT - 650 °C. The antiferromagnetic to paramagnetic transitions occur at TN 250 °C, TN 175 °C and TN 145 °C for the samples with Aex = Ba0.28, x = 0 and Aex = Ca0.17, respectively.
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| 24. |
- Manuel, J., et al.
(författare)
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Electrochemical properties of lithium polymer batteries with doped polyaniline as cathode material
- 2012
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 47:10, s. 2815-2818
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Konferensbidrag (refereegranskat)abstract
- Polyaniline (PAN!) was doped with different lithium salts such as LiPFG and LiClO4 and evaluated as cathode-active material for application in room-temperature lithium batteries. The doped PANT was characterized by FTIR and XPS measurements. In the FTIR spectra, the characteristic peaks of PANT are shifted to lower bands as a consequence of doping, and it is more shifted in the case of PANI doped with LiPFG. The cathodes prepared using PANT doped with LiPF6 and LiClO4 delivered initial discharge capacities of 125 mAh g(-1) and 112 mAh g(-1) and stable reversible capacities of 114 mAh g(-1) and 81 mAh g(-1), respectively, after 10 charge-discharge cycles. The cells were also tested using polymer electrolyte, which delivered highest discharge capacities of 142.6 mAh g(-1) and 140 mAh g(-1) and stable reversible capacities of 117 mAh g(-1) and 122 mAh g(-1) for PANT-LiPF6 and PANI-LiClO4, respectively, after 10 cycles. The cathode prepared with LiPFG doped PANT shows better cycling performance and stability as compared to the cathode prepared with LiClO4 doped PANT using both liquid and polymer electrolytes.
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| 25. |
- Mattisson, Ingela, et al.
(författare)
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Surface characterization and electrochemical properties of hierarchically structured titanium surfaces
- 2013
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408. ; 48:2, s. 389-398
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Tidskriftsartikel (refereegranskat)abstract
- Newly designed implant surfaces with hierarchic structure have been characterized with respect to chemical composition, topography, electrical properties and cell culturing. Three levels of surface roughness are induced starting from a blasted surface with the naturally formed oxide layer. Dissolution of the blasted surface is obtained by chemical treatment in oxalic acid. The surface becomes smoother with multitude of shallow depressions in the walls and bottoms of the blasted structure. The surface oxide layer formed is somewhat thicker than the naturally formed oxide and may contain oxalate. In the final step, part of the oxide layer is dissolved in hydrofluoric acid leading to a high concentration of soluble titanium species. A nanostructured surface is formed by precipitation of titanium oxide at spots on the surface where locally the pH is increased due to hydrogen evolution. The surface roughness is only marginally changed by the chemical treatment while the conductivity of the surface layer is lower for the chemically treated surfaces compared with the blasted reference. The hierarchical structure mimics many natural processes for achieving high shear strength.
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| 26. |
- Mattisson, I., et al.
(författare)
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Surface characterization, electrochemical properties and in vitro testing of hierarchically structured titanium surfaces
- 2013
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Ingår i: Materials Research Bulletin. - : Elsevier BV. - 0025-5408. ; 48:2, s. 389-398
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Tidskriftsartikel (refereegranskat)abstract
- Newly designed implant surfaces with hierarchic structure have been characterized with respect to chemical composition, topography, electrical properties and cell culturing. Three levels of surface roughness are induced starting from a blasted surface with the naturally formed oxide layer. Dissolution of the blasted surface is obtained by chemical treatment in oxalic acid. The surface becomes smoother with multitude of shallow depressions in the walls and bottoms of the blasted structure. The surface oxide layer formed is somewhat thicker than the naturally formed oxide and may contain oxalate. In the final step, part of the oxide layer is dissolved in hydrofluoric acid leading to a high concentration of soluble titanium species. A nanostructured surface is formed by precipitation of titanium oxide at spots on the surface where locally the pH is increased due to hydrogen evolution. The surface roughness is only marginally changed by the chemical treatment while the conductivity of the surface layer is lower for the chemically treated surfaces compared with the blasted reference. The hierarchical structure mimics many natural processes for achieving high shear strength. © 2012 Elsevier Ltd.
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| 27. |
- Ivarsson, David, et al.
(författare)
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Comparison of in vitro methods of measuring mucoadhesion: Ellipsometry, tensile strength and rheological measurements.
- 2012
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Ingår i: Colloids and Surfaces. B, Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 92, s. 353-359
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Tidskriftsartikel (refereegranskat)abstract
- In this work three in vitro methods for the measurement of mucoadhesion have been compared: ellipsometry, tensile strength and rheology. The conditions used for the three methods have been as similar as possible. Six different polymers were investigated: sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), chitosan, polyvinyl pyrrolidone (PVP) and two cross-linked polyacrylic acids, Noveon (hydrophobically modified) and Carbopol. The results showed that PVP did not exhibit mucoadhesion according to any of the methods used. Chitosan, Noveon, Carbopol, CMC and HEC showed good mucoadhesion in the tensile strength and the rheological measurements, but not in the ellipsometry investigation. Chitosan was the only polymer showing good mucoadhesion with the ellipsometry method. No two methods gave the same ranking of mucoadhesive strength of the polymers. The conflicting results obtained with the different methods underline the need for further improvements in existing experimental techniques and theoretical concepts for the correct assessment of mucoadhesive properties.
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