Effect of Sintering on Structural Modification and Phase Transition of Al-Substituted LLZO Electrolytes for Solid State Battery Applications

Owing to high lithium ion conductivity and good stability with lithium metal, Li7La3Zr2O12 (LLZO—a solid electrolyte) has emerged as a viable candidate for solid-state battery applications. In the current study, Al-substituted LLZO (Al-LLZO) powder is synthesized using a typical solid-state reaction. The pellets are made with the synthesized powder and are subjected to annealing for different durations and its effect on the structural properties of the Al-LLZO is investigated in detail. Reitveld refinement of the powder X-ray diffraction pattern reveals that the sintered Al-LLZO belong to the cubic system with the Ia-3d space group at room temperature. Morphology and microstructural properties of sintered powder are analyzed using field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM)/selected area electron diffraction (SAED), respectively. The FESEM image of LLZO pellets shows well-structured cubic grains spread evenly over on the surface after sintering. The chemical compositions of the sample are identified using energy dispersive X-ray analysis (EDAX). The surface chemistry of the prepared samples is examined by X-ray photoelectron spectroscopy (XPS), which states that the observed photoelectron signals from O 1s at about 531 eV and Li1s at 54.52 eV correspond to the Li-O bond in Al-LLZO. Raman spectra have been analyzed and the observed Raman peaks appearing at 299 cm−1, 393 cm−1, 492 cm−1, and 514 cm−1 were assigned to Eg, F2g, A1g, and F2g, respectively. Phase transformation from C-LLZO to the pyrochore LZO phase is noticed when the sample is sintered for 12 h at 1100 °C. The impedance analysis is carried out to measure the conductivity of the Al-LLZO pellet and is found to be 0.3 × 10−5 S cm−1, which is suitable for solid electrolyte applications in lithium ion batteries.

Realization of structural transformation for the enhancement of magnetic and magneto capacitance effect in BiFeO3–CoFe2O4 ceramics for energy storage application

In this study, (1 − x) BFO-xCFO (CFO, x = 0.00, 0.05, 0.10 and 0.30) ceramics were synthesized by a solid-state reaction method; their compositions were driven by structural, microstructural, vibrational, electrical, magnetic properties; their enhanced magneto capacitance (MC) effect have also been carried out. Reitveld refinement studies of X-ray diffraction data shows composition-driven structural phase transformation from rhombohedral (R3c) to tetragonal (P4mm). Two phonon scattering Raman modes were observed for the higher wavenumber which supports the crystal structural transition in the BFO-CFO. Ferroelectric polarization shows that the polarization increased with increasing CFO concentration, which describes the changes of the polar symmetry of the crystal structure from rhombohedral (R3c) to tetragonal (P4mm). In Further, the maximum efficiency of energy density (η = 68.65%), reversible energy density of 0.138 J/cm3 and the strong magneto capacitance was observed in 0.9BFO-0.1CFO, which belongs to the morphotropic phase boundary (MPB) region near to the BiFeO3-rich region. The magnetic response analysis has shown, the saturation magnetization (Ms) values of 83 emu/gm and 139 emu/gm for pure CFO and 0.7BFO-0.3CFO composite, respectively, and their magnetic behaviours were also confirmed with Arrott–Belov–Kouvel (ABK) plot.

Partial Oxidation of Propylene over as Prepared and Acid Enriched Bi2Mo1-xWxO6 System

The compounds Bi2Mo1-xWxO6 (x = 0.0, 0.2, and 0.4) were obtained through a Citrate sol-gel process. Thermogravimetric differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were used for characterization. Reitveld refinement of the XRD data confirmed the crystal structure of all the compositions to be orthorhombic, having Pca21 space group. XPS studies indicated the presence of +6 as well as +4 oxidation state for Mo. Surface acid enrichment of all the catalysts was done and monitored by NH3-TPD studies. Partial oxidation of propylene was studied over all the compounds. The W doping was found to increase the catalytic activity. Moreover, as-prepared catalysts and acid enriched catalysts were compared for their catalytic activity wherein, acid-enriched catalysts showed the improved conversion of propylene without hampering the product selectivity profile. Copyright © 2017 BCREC Group. All rights reservedReceived: 16th September 2016; Revised: 1st December 2016; Accepted: 9th March 2017How to Cite: Parab, S.S., Naik, S.J., Salker, A.V. (2017). Partial Oxidation of Propylene over as Prepared and Acid Enriched Bi2Mo1-xWxO6 System. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (2): 197-205 (doi:10.9767/bcrec.12.2.702.197-205)Permalink/DOI: http://dx.doi.org/10.9767/bcrec.12.2.702.197-205

Powder XRD and TEM study on crystal structure and interstratification of Zn-chlorite (baileychlore)

Baileychlore is Zn-end member trioctahedral chlorite, named by Audrey C. Rule and Frank Radke in 1988 for the honor of Professor Sturges W. Bailey of the University of Wisconsin – Madison, USA. Baileychlore occurs as dark green chlorite on calcite veins from garnet-vesuvianite skarn clasts at Red Dome ore deposit, Chillagoe, Queensland, Australia. The baileychlore has been studied by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray energy-dispersive analytical electron microscopy analyses to determine crystal structure and interstratified layers. Baileychlore with stacking disorder displays streaking reflections of 0k0 (≠6n) hhl (h ≠ 3n). Unit-cell parameters for baileychlore (type I polytype) with a space group of C$ \bar 1$ are: a = 5.351(3), b = 9.266(5), c = 14.418(8) Å, α = 89.741(3)°, β = 96.741(4)°, and γ = 90.122(2)°. The strong lines of the measured XRD pattern [d(Å)(I)(hkl)] are: 14.331(7.151)(90.5)(002); 4.574(23.2)(1$ \bar 1$0, 11$ \bar 1$); 3.572(38.5)(004); 2.653(31.4)($ \bar 1$31, 200, 13$ \bar 1$); 2.406(49.4)(202, $ \bar 1$33, 13$ \bar 3$); 1.543(27.6)($ \bar 3$31, 060, 33$ \bar 1$), respectively. Reitveld refinement provides a composition (Zn2.49Al0.09Fe2+ 0.09□0.33)0.61− for the octahedral sheet and (Si3.53Al0.47)0.47− for the tetrahedral sheets within the 2:1 layer with (Al1.08Fe1.08Mg0.84)1.08+ for the interlayer sheet. The refinement results indicate that baileychlore is an intergrowth of type I and II polytypes. High-resolution TEM images show stacking disorder of baileychlore with small amount of isolated smectite layers.

The Rietveld Refinement of Thermal Synthesized Rhombohedra Boron Nitride Micro-Rod

We reported on a convenient route to synthesize rhombohedra boron nitride (r-BN) micro-rod using urea (CO(NH2)2) and sodium borohydride (NaBH4) through thermal treatment at 1300 °C. The structure, morphology, and chemical composition of the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). In order to determine the phase composition and abundance of the as-synthsized simples, Rietveld refinement has been performed to analyze the XRD data using the Rietan-2000 program. The results show that the abundance of r-BN is about 90.6 wt % and h-BN is 9.4 wt % deduced from Reitveld refinement.

Synchrotron X-ray Diffraction Study of Ba4.5Nd9Ti18O54 Microwave Dielectric Ceramics at 10–295 K

The structure of ceramic Ba4.5Nd9Ti18O54 was investigated by synchrotron x-ray powder diffraction from 10 to 295 K. Reitveld refinement and Le Bail profile analysis were applied to the data. Based on an orthorhombic structure, unit cell parameters of a = 22.3479(3) Å, b = 7.6955(1) Å, and c = 12.2021(2) Å were obtained at room temperature and a = 22.3367(5) Å, b = 7.6738(1) Å, and c = 12.1842(3) Å at 10 K. No evidence was found for any major structural change from 10 to 295 K. Within the tungsten bronze framework the two pentagonal channels were fully occupied by Ba; the remaining Ba atoms shared the rhombic channels with Nd. Thermal expansion of the unit cell was found to be anisotropic. The largest expansion occurs along the b cell edge, and the least along the a cell edge. It is proposed that the anisotropy is due to enhanced bending of the TiO6 polyhedra chains along the b direction.

The determination of the residual strains and stresses in a tungsten inert gas welded sheet of IN718 superalloy using neutron diffraction

The residual stress state in a tungsten inert gas (TIG) welded sheet of IN718, a high-strength nickel-based superalloy, has been characterized using neutron diffraction. The measurements were performed using a time-of-flight diffractometer, which allowed lattice strains from the γ-γ′ {111} and γ-γ′ {311} composite peaks to be compared with the Reitveld-refined spectra. Residual stresses were estimated using plane-specific values of Young's modulus and Poisson's ratio for the {311} and {111} peaks, and the macroscopic material response for the Reitveld-refined data. These values were obtained from a theoretical analysis of existing data after Kröner. The weld considered was an autogenous TIG weld 180mm long placed centrally on to a 2mm × 100mm × 200mm solution heat-treated sheet of IN718. The strain was mapped over the central 140mm of the plate; within this region, the measured strains were almost constant along the length, with the peak bulk longitudinal strain of 1700 × 10-6 detected 4mm from the weld centre, in the heat-affected zone. The corresponding peak longitudinal stress was 270 MPa, and the tensile region 11 mm wide, with the longitudinal residual stresses typically up to 2.5 times greater than those in the transverse direction. It was also found that, while in-weld stresses derived from analysis of single peaks may be incorrect due to textural and compositional effects, those derived from Reitveld refinement of the entire spectrum showed reasonable agreement with those obtained from incremental hole drilling measurements made with the Matthar-Soete method.