| 1. |
- Dyachenko, O G, et al.
(författare)
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Structure and properties of Ba6 − xLnxNb10O30, Ln = La, Ce and Nd compounds
- 1997
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Ingår i: Materials research bulletin. - 0025-5408 .- 1873-4227. ; 32:4, s. 409-419
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Tidskriftsartikel (refereegranskat)abstract
- Ba6 − xLnxNb10O30 compounds, Ln = La, Ce and Nd, with a tetragonal tungsten bronze-type structure have been synthesized and were characterized by X-ray powder diffraction and EDS analysis. The homogeneity regions of the obtained compounds were found to be 0 ≤ x ≤ 2 for La, and 0 ≤ x ≤ 1.5 for Ce and Nd. The crystal structures of Ba5LaNb10O30 and Ba4La2Nb10O30 were refined using X-ray powder diffraction data. Refinement indicated the presence of vacancies in the positions. This observation was supported by oxidation studies of the La-substituted compounds. The temperature dependence of the normalized resistivity of the compounds showed a nonmetallic behavior. The increase in the ratio with decreasing temperature is less distinct for the phases with the higher concentration of rare-earth cation.
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| 2. |
- Nilsson, Mattias, et al.
(författare)
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Synthesis, structural characterisation and magnetic properties of Gd14W4O33-xNy(0<=x<=17+/-2, 0<=y<=9+/-2), a new fluorite-related oxynitride
- 1996
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 240:1-2, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- A series of crystalline Gd-W oxides, with Gd:W ratios spanning the values 0.1-3.5, has been prepared and treated with a flow of NH3(g) in the temperature range 700-1100 degrees C. Besides the previously reported formation of GdWO3N and Gd2WO3N2, the following new results were obtained: (i) cubic Gd0.1WO3 upon ammonolysis forms an (oxy)nitride Gd0.1W(O,N)(y) with an f.c.c. lattice; (ii) the previously described Gd2WO3N2 exhibits a solid solubility range Gd3-xW1+x(O,N)(y) with, approximately, 0 less than or equal to x less than or equal to 1; (iii) ammonolysis of Gd14W4O33 yields an oxynitride, the composition of which varies with the synthesis temperature according to Gd14W4O33-xNy(O less than or equal to x less than or equal to 17+/-2, 0 less than or equal to y less than or equal to 9+/-2). All strong diffraction lines, including those of the pure oxide (x = y = 0), can be indexed with a body-centred monoclinic unit cell derived from that of fluorite. For Gd14W4O33 the cell 3 parameters are a = 5.3592(11), b = 3.7295(7), c = 3.8636(8) Angstrom, beta = 92.170(2)degrees and V = 77.17 Angstrom(3). However, strong superstructure reflections in the electron diffraction patterns indicate that the true unit cell is considerably larger. A partial structure determination of Gd14W4O33-xNy has been carried out by the Rietveld method. Magnetic susceptibility measurements in the temperature interval 15-300 K show a Curie-Weiss law behaviour for Gd14W4O33-xNy, with mu(eff) = 8.08+/-0.06 Bohr magntons per Gd3+ and theta = -12.4+/-1.1 K for all compositions.
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| 3. |
- Grins, Jekabs, et al.
(författare)
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Synthesis, Structure and Magnetic Susceptibility of the Oxynitride Spinel Mn2(MnTa3)N6-δO2+δ, 0 ≤ δ ≤ 1
- 1995
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 117:1, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- The oxynitride spinel Mn-2(MnTa3)N6-deltaO2+delta, with 0 less than or equal to delta less than or equal to 1, has been synthesized at 1175 K by ammonolysis of a mixture of a Ta-containing xerogel and Mn(OAc)(2) . 4H(2)O. The N content was determined by combustion analysis and thermogravimetric oxidation, yielding a composition confined between Mn-2(MnTa3)N6O2 (delta = 0) and Mn-2(MnTa3)N5O3 (delta = 1). The structure is cubic, with space group Fd3m and a = 8.8353(3) Angstrom. It was refined using the Rietveld technique and neutron powder diffraction data collected at room temperature and 15 K, to R(F) = 2.9 and 3.8%, respectively. The tetrahedral sites are occupied only by Mn atoms and the octahedral sites statistically by 25% Mn and 75% Ta atoms. The N and O atoms are randomly distributed over the anion sites. The magnetic susceptibility exhibits a maximum at 29 K and a Curie-Weiss behavior at higher temperatures with theta(a) = -250(20) K and mu(eff) = 5.7(2) Bohr magnetons per Mn atom. The neutron powder diffraction data collected at 15 K showed no evidence of magnetic ordering. A NaCl-type phase with a = 4.4382(2) Angstrom and tentative composition Mn0.8Ta0.2(O,N) was observed in preparations at 1175 K. A hexagonal Mn4Ta2(O,N)(x) phase with cell dimensions a = 5.3024(4) Angstrom, c = 14.493(2) Angstrom was obtained at 973 K. (C) 1995 Academic Press, Inc.
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| 4. |
- ZUBKOV, VG, et al.
(författare)
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Synthesis and Structural, Magnetic and Electrical Characterization of the Reduced Oxoniobates BaNb8O14, EuNb8O14, Eu2Nb5O9 and EuxNbO3 (x = 0.7, 1.0).
- 1995
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Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 226, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- Powder samples of the reduced oxoniobates Eu0.7NbO3, EuNbO3, Eu2Nb5O9, EuNb8O14 and BaNb8O14 have been synthesised. EuNbO3 and Eu0.7NbO3 adopt the perovskite type structure (space group Pm3m) with unit cell parameters a = 4.021 (1) and 3.981 (3) Angstrom, respectively. Eu,Nb,Og exhibits an intergrowth structure which can be described as alternating slabs of NbO and EuNbO3. It crystallises in P4/mmm with a = 4.131(1) and c = 12.043(5) Angstrom. EuNb8O14 and the here synthesised modification of BaNb8O14 is isostructural with SrNb8O14. The structures of EuNb8O14 and BaNb8O14 have been refined from X-ray powder diffraction data with the Rietveld technique, They have the unit cell parameters a = 9.2272(1), b = 10.2647(2), c = 5.9381(1) and a = 9.3451(1), b = 10.2689(2), c = 5.9470(4) Angstrom, (space group Pbam), respectively. In all the studied compounds AO(12) cuboctahedra (A = Eu, Ba) form either chains (in ANb(8)O(14)), double layers (in Eu2Nb5O9) or three-dimensional nets (in EuNbO3 and Eu0.7NbO3). Magnetic susceptibility measurements show temperature independent paramagnetism for BaNb8O14, while the susceptibilities of the Eu niobates follow Curie-Weiss laws with effective magnetic moments in good agreement with the expected mu(eff)=7.9 mu(B) for EU(2+). Eu0.7NbO3 and Eu1.0NbO3 exhibit ferromagnetic ordering below 4 K. BaNb8O14 and EuNb8O14 are semiconductors, while Eu2Nb5O9, EuNbO3 and Eu0.7NbO3 are metallic.
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| 5. |
- Tyutyunnik, A P, et al.
(författare)
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Phases in the Mn-Nb-N-O system, formed by ammonolysis of mixtures of Mn acetate tetrahydrate and a Nb xerogel
- 1998
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Ingår i: Materials research bulletin. - 0025-5408 .- 1873-4227. ; 33:7, s. 1035-1044
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Tidskriftsartikel (refereegranskat)abstract
- Phase formation in the system Mn-Nb-O-N has been studied by ammonolysis of mixtures of Mn acetate tetrahydrate and an Nb xerogel at 600-900 degrees C. Observed phases were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, combustion analysis, and thermogravimetric analysis. An Nb4N5-related phase, with a metal content of less than or equal to 15 at% Mn, was obtained pure at 650-700 degrees C. A new hexagonal phase MnNb2(N,O)(3) was obtained at 750-900 degrees C, Its structure is related to, but not isotypic with, that of Nb5N6. In addition, the preparations contained cubic NaCl-type (Mn, Nb)(N,O) phases. The Mn-free Nb4-y(N,O)(5) and Nb5-y(N,O)(6) (y signifying metal vacancies), with Nb4N5- and Nb5N6-type structures, respectively, were synthesized, to make possible structural comparisons with the Mn-containing phases. A black trigonal phase Mn-3.66(6)Nb-2.34(6)(O,N)(9) with a structure closely related to that of Mn4Nb2O9 was obtained at 700 degrees C. (C) 1998 Elsevier Science Ltd.
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| 6. |
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| 7. |
- Berg, Helena
(författare)
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The rational design of lithium insertion materials for battery applications
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transition-metal oxide spine1 LiMn2O4 is a promising cathode material for high-capacity lithium-ion batteries. Structure-property relationships pertaining to the electrochemical cycling behaviour of LiMn2O4 have been studied. The techniques exploited have been in situ X-ray and neutron diffraction, in combination with quantum-mechanical band-structure calculations. The results obtained lay the ground for an improved basis for designing new insertion materials.Substitution of Mn by Ni in LiMn2O4 and by Li in Li1+xMn2-xO4 give qualitatively different results: Ni is found to replace Mn directly, while Li takes up entirely new sites not observed earlier. Band-structure calculations have been used to better understand the crystallographically observed x-dependence of the Li1+xMn2-xO4 structure, and the underlying mechanisms of lithium-ion extraction/insertion.Quantitative observation of charge passed through the cell has also been related to the amount of lithium extracted to indicate possible sources of irreversible capacity loss, and how synthesis technique can influence cell performance.The LiMn2O4 structure has also been studied by neutron diffraction after treatment in strong-acid solutions, where Li ® H ion-exchange has been observed to take place. This process has strong implications for the dissolution of Mn2+ ions from the cathode into the electrolyte, especially at elevated temperatures, and the related corrosion process occurring at the cathode surface.
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| 8. |
- Erlandsson, Lars, et al.
(författare)
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Purification process for trimethylolethane
- 1996
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- A process for combined recovery and purifn. of trimethylolethane from aq. reactions mixts. obtained by reacting formaldehyde with propionic aldehyde in the presence of a metal hydroxide comprises a no. of steps including evapg. the reaction mixt. allowing only trimethylolethane to at least partially crystallize as crude trimethylolethane, evapg. remaining water, heating obtained reaction mixt. and/or obtained crude trimethylolethane, and sublimating trimethylolethane for recovery as purified product
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| 9. |
- Tyutyunnik, A P, et al.
(författare)
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Synthesis, superconducting properties and structural (including electron diffraction) studies of Na chi NbO2 and Li chi NbO2
- 1996
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Ingår i: European Journal of Solid State and Inorganic Chemistry. - : Wiley. - 0992-4361 .- 1873-3751. ; 33, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- Monophasic NaxNbO2 (x = 0.5 - 0.6), T-c approximate to 4.1 K was prepared by solid state reaction between Na3NbO4 and Nb. X-ray powder diffraction data from a monophasic sample were used for a refinement of the structure of Na0.5NbO2 (R(p) = 7.4 % and R(I) = 5.3 %), using the Rietveld method. At low x-values a closely related second phase can occur. Rietveld refinement using X-ray powder diffraction data showed this phase to be isostructural with NaNbO2 but with the chemical formula Na0.1NbO2. Transmission electron microscopy studies of NaxNbO2 and LixNbO2 revealed the presence of superstructures in some crystallites. The electron diffraction patterns resemble to some extent those reported for transformations among tantalum chalcogenides.
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| 10. |
- Buch-Rasmussen, Thomas
(creator_code:cre_t)
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A device for the administration of a liquid medicament suspension
- 1998
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- In an ampoule for a medicament the space accommodating the medicament is defined by an ampoule wall (1) a pierceable seal (5) closing one end of the ampoule and a piston (7) closing the other end of the ampoule. A metal containing fixation element (8) is secured to one of the parts defining the medicament accommodating space. A mixing element (9, 10) also containing a metal and having a density larger than 1,0 g/cm<3> is movable in medicament accommodating space. At least one of the elements, the fixation element (8) and the mixing element (9, 10), can be attracted by a magnet, and at least one of these elements is a magnetic element, the magnetic strength being so that the mixing element (9, 10) can during normal handling of the ampoule be fixed relative to this ampoule by the magnetic attraction between the fixation element (8) and the mixing element (9, 10) but may be released from its fixed position by manual operation.
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