The Experts below are selected from a list of 6945 Experts worldwide ranked by ideXlab platform
Barbara Pacewska - One of the best experts on this subject based on the ideXlab platform.
-
some physicochemical properties of aluminium oxides obtained from basic aluminium Sulphates
Thermochimica Acta, 1992Co-Authors: Barbara PacewskaAbstract:Abstract Eight different kinds of aluminium oxide were obtained by thermal decomposition of isomorphous alunite compounds, namely, basic aluminium ammonium Sulphate (BAAS) and basic aluminium Potassium Sulphate (BAPS). The thermal decomposition of the basic salts was performed in an atmosphere of air, in vacuum, in an atmosphere of hydrogen, and in an environment of carbon and water vapour. The Particle size distribution, phase composition, specific surface area (adsorption of benzene vapour), and the Na 2 O and K 2 O contents were determined in the aluminium oxide samples obtained.
-
thermal decomposition of basic aluminium Potassium Sulphate baps in hydrogen atmosphere
Thermochimica Acta, 1991Co-Authors: Barbara Pacewska, J PysiakAbstract:Abstract The dissociation of basic aluminium Potassium Sulphate (BAPS) in hydrogen atmosphere was studied using thermal analysis, X-ray phase analysis and chemical analysis. It was found that under these conditions the desulphurisation of the basic salt is more complete and occurs at lower temperatures in comparison with this process in air. The solid products of decomposition of the studied compound at 1223 K are α-Al2O3 and β″-KAl5O8. The present work was preceded by a thermodynamic analysis of the reactions which could occur during desulphurisation of basic salt in a hydrogen atmosphere; the results of the calculations were compared with the experimental results.
Ram Kripal - One of the best experts on this subject based on the ideXlab platform.
-
zero field splitting parameters of cr3 in lithium Potassium Sulphate at orthorhombic symmetry site
Acta Physica Polonica A, 2013Co-Authors: Sangita Pandey, Ram KripalAbstract:(Received April 28, 2011; in nal form October 25, 2012) The superposition model is used to investigate the crystal eld parameters, Bkq of Cr 3+ in lithium Potassium Sulphate. The zero eld splitting parameters D and E are then determined using microscopic spin Hamiltonian theory and compared with the experimental values obtained by electron paramagnetic resonance. Both zero eld splitting parameters D and E evaluated theoretically are in good agreement with the experimental values. The results suggest that the Cr ion occupies substitutional K site in lithium Potassium Sulphate.
-
epr and optical absorption studies of cr3 doped lithium Potassium Sulphate single crystals
Materials Chemistry and Physics, 2010Co-Authors: Ram Kripal, Indrajeet MishraAbstract:Abstract X-band electron paramagnetic resonance (EPR) studies of Cr3+ doped lithium Potassium Sulphate single crystals have been done at room temperature. The Cr3+ crystal field and spin Hamiltonian parameters have been evaluated by employing resonance line positions observed in the EPR spectra for different orientations of external magnetic field. The evaluated g, D and E values are: gx = 2.0763 ± 0.0002, gy = 1.9878 ± 0.0002, gz = 1.8685 ± 0.0002 and D = 549 ± 2 × 10−4 cm−1, E = 183 ± 2 × 10−4 cm−1. Using EPR data the site symmetry of Cr3+ ion in the crystal is discussed. Cr3+ ion enters the lattice substitutionally replacing K+ site. The optical absorption study of the single crystal is also done in 195–925 nm wavelength range at room temperature. By correlating optical and EPR data the nature of bonding in the crystal is discussed. The calculated values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained as: B = 697, C = 3247, Dq = 2050 cm−1, h = 1.146 and k = 0.21.
-
epr and optical absorption of vo2 impurity in lithium Potassium Sulphate single crystal
Physica B-condensed Matter, 2009Co-Authors: Ram Kripal, Manju MauryaAbstract:Abstract Electron paramagnetic resonance (EPR) and optical absorption studies of VO 2+ doped lithium Potassium Sulphate single crystals are carried out at room temperature. The angular variation of the spectra is studied in the crystallographic a*b, bc and ca* plane. Vanadyl is found to have fixed orientations in the lattice and there are two magnetically inequivalent complexes in the lattice. The spin Hamiltonian parameters obtained from single crystal data for the two sites are, Site I: g xx =2.0015±0.0002, g yy =1.9835±0.0002, g zz =1.9211±0.0002, A xx =(48±2)×10 −4 cm −1 , A yy =(64±2)×10 −4 cm −1 , A zz =(169±2)×10 −4 cm −1 , Site II: g xx =2.0019±0.0002, g yy =1.9796±0.0002, g zz =1.9225±0.0002, A xx =(48±2)×10 −4 cm −1 , A yy =(83±2)×10 −4 cm −1 , A zz =(178±2)×10 −4 cm −1 . The first three bands observed in optical absorption spectrum are attributed to d–d transitions and the last band is probably charge transfer band. The band positions are calculated using energy expressions and compared with the observed values to confirm the transitions. Crystal field parameter ( D q ) and tetragonal parameters ( D s and D t ) are also evaluated. Using EPR and optical results, the molecular orbital parameters of VO 2+ ions in the lattice are evaluated with a tetragonal symmetry approximation (because the rhombic part is small) and the nature of bonding in the complex is discussed.
-
epr and optical absorption study of cu2 doped lithium Potassium Sulphate single crystals
Physica B-condensed Matter, 2008Co-Authors: Ram Kripal, Manisha Bajpai, Manju Maurya, Har GovindAbstract:Abstract EPR spectra of Cu 2+ ion doped in lithium Potassium Sulphate single crystal at room temperature are reported. The observed spectra are fitted to a spin Hamiltonian of orthorhombic symmetry with Cu 2+ (site I) g x =2.0930, g y =2.1421, g z =2.2900 (±0.0002) and A x =85, A y =89, A z =184 (±2×10 −4 cm −1 ); Cu 2+ (site II) g x =2.0795, g y =2.1580, g z =2.2876 (±0.0002) and A x =93, A y =95, A z =189 (±2×10 −4 cm −1 ); respective errors given in brackets. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The ground state wave function of the Cu 2+ ion in this lattice is determined as predominantly | x 2 − y 2 〉. The g -factor anisotropy is calculated and compared with the experimental value. The optical absorption of the crystal at room temperature is also recorded. Further, with the help of the optical absorption and EPR data, the nature of bonding in the complex is discussed.
Indrajeet Mishra - One of the best experts on this subject based on the ideXlab platform.
-
epr and optical absorption studies of cr3 doped lithium Potassium Sulphate single crystals
Materials Chemistry and Physics, 2010Co-Authors: Ram Kripal, Indrajeet MishraAbstract:Abstract X-band electron paramagnetic resonance (EPR) studies of Cr3+ doped lithium Potassium Sulphate single crystals have been done at room temperature. The Cr3+ crystal field and spin Hamiltonian parameters have been evaluated by employing resonance line positions observed in the EPR spectra for different orientations of external magnetic field. The evaluated g, D and E values are: gx = 2.0763 ± 0.0002, gy = 1.9878 ± 0.0002, gz = 1.8685 ± 0.0002 and D = 549 ± 2 × 10−4 cm−1, E = 183 ± 2 × 10−4 cm−1. Using EPR data the site symmetry of Cr3+ ion in the crystal is discussed. Cr3+ ion enters the lattice substitutionally replacing K+ site. The optical absorption study of the single crystal is also done in 195–925 nm wavelength range at room temperature. By correlating optical and EPR data the nature of bonding in the crystal is discussed. The calculated values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained as: B = 697, C = 3247, Dq = 2050 cm−1, h = 1.146 and k = 0.21.
Antonio Martins Figueiredo Neto - One of the best experts on this subject based on the ideXlab platform.
-
effect of alkyl chain length of alcohols on nematic uniaxial to biaxial phase transitions in a Potassium laurate alcohol k2so4 water lyotropic mixture
Liquid Crystals, 2012Co-Authors: Erol Akpinar, Dennys Reis, Antonio Martins Figueiredo NetoAbstract:Lyotropic liquid crystalline quaternary mixtures of Potassium laurate (KL), Potassium Sulphate (K2SO4)/alcohol (n-OH)/water, with the alcohols having different numbers of carbon atoms in the alkyl chain ( ), from 1-octanol to 1-hexadecanol, were investigated by optical techniques (optical microscopy and laser conoscopy). The biaxial nematic phase domain is present in a window of values of , where is the number of carbon atoms in the alkyl chain of KL. The biaxial phase domain became smaller and the uniaxial-to-biaxial phase transition temperatures shifted to relatively higher temperatures upon going from 1-nonanol to 1-tridecanol. Moreover, compared with other lyotropic mixtures these new mixtures present high birefringence values, which we expect to be related to the micellar shape anisotropy. Our results are interpreted assuming that alcohol molecules tend to segregate in the micelles in a way that depends on the relative value of n with respect to . The larger the value of n, the more alcohol molecules...
-
effect of the alkyl chain length of the alcohols on the nematic uniaxial to biaxial phase transitions in the Potassium laurate alcohol k2so4 water lyotropic mixture
arXiv: Soft Condensed Matter, 2012Co-Authors: Erol Akpinar, Dennys Reis, Antonio Martins Figueiredo NetoAbstract:Lyotropic liquid crystalline quaternary mixtures of Potassium laurate (KL), Potassium Sulphate (K2SO4)/alcohol (n-OH)/water, with the alcohols having different number of carbon atoms in the alkyl chain (n), from 1 octanol to 1-hexadecanol, were investigated by optical techniques (optical microscopy and laser conoscopy). The biaxial nematic phase domain is present in a window of values of n = nKL \pm 2, where nKL = 11 is the number of carbon atoms in the alkyl chain of KL. The biaxial phase domain got smaller and the uniaxial-to-biaxial phase transition temperatures shifted to the relatively higher temperatures on going from 1-nonanol to 1-tridecanol. Moreover, these new mixtures present high values of the birefringences comparing to other lyotropic mixtures. This result is expected to be related to the micellar shape anisotropy. Our results are interpreted assuming that alcohol molecules tend to segregate in the micelles in a way that depends on the relative value of n with respect to nKL . The larger the value of n, the more alcohol molecules tend to be located in the curved parts of the micelle, favoring the uniaxial nematic calamitic phase with respect to the biaxial and uniaxial discotic nematic phases.
J Pysiak - One of the best experts on this subject based on the ideXlab platform.
-
thermal decomposition of basic aluminium Potassium Sulphate baps in hydrogen atmosphere
Thermochimica Acta, 1991Co-Authors: Barbara Pacewska, J PysiakAbstract:Abstract The dissociation of basic aluminium Potassium Sulphate (BAPS) in hydrogen atmosphere was studied using thermal analysis, X-ray phase analysis and chemical analysis. It was found that under these conditions the desulphurisation of the basic salt is more complete and occurs at lower temperatures in comparison with this process in air. The solid products of decomposition of the studied compound at 1223 K are α-Al2O3 and β″-KAl5O8. The present work was preceded by a thermodynamic analysis of the reactions which could occur during desulphurisation of basic salt in a hydrogen atmosphere; the results of the calculations were compared with the experimental results.