Enhancement of V2O5 Li-ion cathode stability by Ni/Co doped Li-borate-based glass.

In this research, we investigate the stability of a Li-ion cathode created by mixing a borate based glass which has been doped with Ni/Co and vanadium pentoxide (V2O5). V2O5 has a high specific capacity in battery systems because of its layered structure and variety of oxidation states. However, due to the flimsy structure, the capacity stability of V2O5 is fairly low. In this case, we seek to overcome the problem by mixing Ni/Co-doped borate based glass. The voltage-capacity graph demonstrates that the form of the glass mix was changed from a stairway shape to a straight line while the capacity was not much decreased. The crystallography study using X-ray diffractograms looked at whether the cycling test had changed the crystal structure of V2O5. The X-ray Absorption Near Edge Structure (XANES) results also reveal that V2O5's oxidation state changed from V5+ to V4+. The glass mix can retain more of the V5+ state, indicating that glass mixture helps to release the Li-ions trapped in the structure. The findings of this study might contribute to the rapid advancement of renewable energy and electric vehicle technology.

A compact furnace for in situ X-ray absorption spectroscopy: design, fabrication and study of cationic oxidation states in Pr6O11 and NiO.

A well designed compact furnace has been designed for in situ X-ray absorption spectroscopy (XAS). It enables various heat ramps from 300 K to 1473 K. The furnace consists of heaters, a quartz tube, a circulated refrigerator and a power controller. It can generate ohmic heating via an induction process with tantalum filaments. The maximum heating rate exceeds 20 K min-1. A quartz tube with gas feedthroughs allows the mixing of gases and adjustment of the flow rate. The use of this compact furnace allows in situ XAS investigations to be carried out in transmission or fluorescence modes under controlled temperature and atmosphere. Moreover, the furnace is compact, light and well compatible to XAS. The furnace was used to study cationic oxidation states in Pr6O11 and NiO compounds under elevated temperature and reduced atmosphere using the in situ X-ray absorption near-edge structure (XANES) technique at beamline 5.2 SUT-NANOTEC-SLRI of the Synchrotron Light Research Institute, Thailand. At room temperature, Pr6O11 contains a mixture of Pr3+ and Pr4+ cations, resulting in an average oxidation state of +3.67. In situ XANES spectra of Pr (L3-edge) show that the oxidation state of Pr4+ cations was totally reduced to +3.00 at 1273 K under H2 atmosphere. Considering NiO, Ni2+ species were present under ambient conditions. At 573 K, the reduction process of Ni2+ occurred. The Ni0/Ni2+ ratio increased linearly with respect to the heating temperature. Finally, the reduction process of Ni2+ was completely finished at 770 K.

SUT-NANOTEC-SLRI beamline for X-ray absorption spectroscopy.

The SUT-NANOTEC-SLRI beamline was constructed in 2012 as the flagship of the SUT-NANOTEC-SLRI Joint Research Facility for Synchrotron Utilization, co-established by Suranaree University of Technology (SUT), National Nanotechnology Center (NANOTEC) and Synchrotron Light Research Institute (SLRI). It is an intermediate-energy X-ray absorption spectroscopy (XAS) beamline at SLRI. The beamline delivers an unfocused monochromatic X-ray beam of tunable photon energy (1.25-10 keV). The maximum normal incident beam size is 13 mm (width) × 1 mm (height) with a photon flux of 3 × 108 to 2 × 1010 photons s-1 (100 mA)-1 varying across photon energies. Details of the beamline and XAS instrumentation are described. To demonstrate the beamline performance, K-edge XANES spectra of MgO, Al2O3, S8, FeS, FeSO4, Cu, Cu2O and CuO, and EXAFS spectra of Cu and CuO are presented.

Polymerized Complex Synthesis and Effect of Ti Dopant on Magnetic Properties of LaFeO3 Nanoparticles.

Structure, characterization, and magnetic properties of Ti-doped LaFeO3 (LaFe(1-x)Ti(x)O3, x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles synthesized by polymerized complex method are investigated. All LaFe(1-x)Ti(x)O3 nanoparticles were successfully obtained from calcination of the precursor at 1050 degrees C in air for 2 h. The calcined LaFe(1-x)Ti(x)O3 samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge spectroscopy (XANES) and vibrating sample magnetometry (VSM). The XRD and TEM results showed that all LaFe(1-x)Ti(x)O3 samples had a single phase nature with the orthorhombic structure. The valence states were mixed in the Fe3+ and Fe4+ state for Fe ions and Ti4+ state for Ti ions, as confirmed by XPS and XANES results. The weak ferromagnetic behavior with the highest magnetization (M) of -0.23 emu/g at 10 kOe was obtained for x = 0.4. The origin of the ferromagnetism (FM) for all LaFe1-x)Ti(x)O3 samples supports the magnetic coupling between Fe3+ and Fe4+ ions via double exchange (DE) interaction.

The DC Bias Voltage Effect and Non-Linear Dielectric Properties of Titanate Nanotubes.

This work reports the nonlinear current-voltage behavior and the effects of dc bias voltage on the dielectric and electrical properties of titanate nanotubes (TNTs) prepared by hydrothermal method at 130 degrees C for 24 h. The TNTs sample exhibited high dielectric constant of > 10(4) at 100 Hz at room temperature with slight dependence on frequency in the range of 10(2)-10(4) Hz. The external resistance forms at the interface between electrode and surface sample. It was found that the dielectric constant of the sample decreased with increasing dc bias voltage due to the decrease in the electrode capacitance. For the study of the non-linear dielectric properties, the breakdown electric field (E(b)) value of the prepared TNTs sample obtained with J = 1 mA cm(-1) was found to be 149 V cm(-1). The E(b) value of the sample was significantly decreased with increasing temperature. The non-ohmic behavior tends to become linear ohmic in characteristic as the temperature increased.

Structure of the hydrated Ca(2+) and Cl(-): Combined X-ray absorption measurements and QM/MM MD simulations study.

A combination of X-ray absorption spectroscopy (XAS) measurements and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations has been applied to elucidate detailed information on the hydration structures of Ca(2+) and Cl(-). The XAS spectra (extended X-ray absorption fine structure, EXAFS, and X-ray absorption near-edge structure, XANES) measured from aqueous CaCl(2) solution were analyzed and compared to those generated from snapshots of QM/MM MD simulations of Ca(2+) and Cl(-) in water. With regard to this scheme, the simulated QM/MM-EXAFS and QM/MM-XANES spectra, which correspond to the local structure and geometrical arrangement of the hydrated Ca(2+) and Cl(-) at molecular level show good agreement with the experimentally observed EXAFS and XANES spectra. From the analyses of the simulated QM/MM-EXAFS spectra, the hydration numbers for Ca(2+) and Cl(-) were found to be 7.1 +/- 0.7 and 5.1 +/- 1.3, respectively, compared to the corresponding values of 6.9 +/- 0.7 and 6.0 +/- 1.7 derived from the measured EXAFS data. In particular for XANES results, it is found that ensemble averages derived from the QM/MM MD simulations can provide reliable QM/MM-XANES spectra, which are strongly related to the shape of the experimental XANES spectra. Since there is no direct way to convert the measured XANES spectrum into details relating to geometrical arrangement of the hydrated ions, it is demonstrated that such a combined technique of XAS experiments and QM/MM MD simulations is well-suited for the structural verification of aqueous ionic solutions.