Influence of reduction conditions of NiO on its mechanical and electrical properties

Yttria stabilized zirconia with a nickel catalyst (Ni-YSZ) is the most developed, widely used cermet anode for manufacturing Solid Oxide Fuel Cells (SOFCs). Its electro-catalytic properties, mechanical durability and performance stability in hydrogen-rich environments makes it the state of the art fuel electrode for SOFCs. During the reduction stage in initial SOFC operation, the virgin anode material, a NiO-YSZ mixture, is reduced to Ni-YSZ. The volume decrease associated with the change from NiO-YSZ to Ni-YSZ creates voids and causes structural changes, which can influence the physical properties of the anode. In this work, the structural, mechanical and electrical properties of NiO samples before and after reduction in pure H2 and a mixture of 5 vol. % H2-Ar were studied. The NiO to Ni phase transformations that occur in the anode under reducing and Reduction-Oxidation (RedOx) cycling conditions and the impact on cell microstruc-ture, strength and electrical conductivity have been examined. Results show that the RedOx treatment of the NiO samples influence on their properties controversially, due to structural transformation (formation of large amount of fine pores) of the reduced Ni. It strengthened the treated samples yielding the highest mechanical strength values of 25.7 MPa, but from another side it is resulting in lowest electrical conductivity value of 1.9×105 S m-1 among all reduced samples. The results of this investigation shows that reduction conditions of NiO is a powerful tool for influence on properties of the anode substrate

Nanomaterials in Dental Applications

score: 0collation: 133-14

Innovative transparent non-scattering TiO2 bactericide thin films inducing increased E. coli cell wall fluidity

This study presents the first account for transparent, non-scattering TiO2 films on radio-frequency (RF) plasma and ultraviolet light in the C-spectral region (UVC) pretreated polyethylene (PE). These pretreatments allow the PE to bind higher amounts of TiO2 necessary to induce E. coil inactivation in the minute range under simulated sunlight irradiation. The uniform TiO2 film was sputtered by direct current magnetron sputtering (DC). These higher TiO2 loadings were necessary to obtain faster bacterial inactivation kinetics on the PE films. The peak shifts in the stretching of the symmetric and asymmetric vibrational infrared spectra of the C H groups were followed during the time of bacterial inactivation (60 min). This time was concomitant with the time required for the hydrophobic to hydrophilic transition on PE-TiO2. The production of malondialdehyde (MDA) was observed during E. coli loss of viability. PE pretreatment led to a significant increase in the TiO2 loadings on the PE surface as shown by X-ray fluorescence (XRF), X-ray-diffraction (XRD) by X-ray photoelectron spectroscopy (XPS). (C) 2014 Elsevier B.V. All rights reserved

Effect of Ti on phase stability and strengthening mechanisms of a nanocrystalline CoCrFeMnNi high-entropy alloy

A CoCrFeNiMnTi0.1 high-entropy alloy (HEA) was processed by high-pressure torsion (HPT) followed by post-deformation annealing (PDA) at 200-900 °C. Microstructural evaluations revealed that the initial and HPT-processed microstructures consisted of a single fcc phase and there was no evidence for decomposition during severe plastic deformation. However, PDA at temperatures below 900 °C promoted the formation of a multi-phase microstructure containing new precipitates and significant grain coarsening occurred after PDA at >800 °C due to a dissolution of the precipitates. PDA at 800 °C for 60 min led to very good mechanical properties with an ultimate tensile strength (UTS) and elongation to failure of >1000 MPa and ~40%, respectively. The results demonstrate that the minor addition of Ti to the CoCrFeNiMn alloy has no direct effect on the strengthening mechanisms but nevertheless this addition significantly increases the thermal stability of the precipitates and these precipitates are effective in minimizing grain coarsening. Therefore, the Ti addition plays an important role in strengthening the HEA

The effect of MWCNT modification on structural and morphological properties of Li4Ti5O12

Lithium titanium oxide (Li4Ti5O12) particles were surface-modified with 1-5% wt. of multi-walled carbon nanotubes (MWCNT) using a new low temperature method (LTM). Subsequent techniques have been applied to characterize all materials: X-ray powder diffraction (XRD), Raman and X-ray photoelectron (XPS) spectroscopy, scanning electron (SEM), transmission (STEM), and atomic force (AFM) microscopy. The selected materials have been subjected to preliminary electrochemical analysis. The effect of the synthesis conditions on the obtained series of LTO/1-5% wt. MWCNT nanocomposites was analyzed. X-ray diffraction showed that the crystal structure of LTO is not affected by the multi-walled carbon nanotubes (MWCNT) modification. Raman spectroscopy confirms the XRD results that the MWCNTs do not affect the LTO structure and all nanocomposites show similar levels of defects and/or degree of graphitization. The XPS measurements showed the most intense line at the binding energy of 284.5 eV, which corresponds to the C=C/C-C bonding in carbon atoms in the graphitic structure on the surface of the LTO material. Additionally, the peak at 285.3 eV was attributed to aliphatic structures, edges, and defects in the graphitic nanotube structure, whereas the peaks at 286.1, 287.6, 289.0 and 290.1 eV, correspond to C-O, C- O, HO-C=O, and OCOO, carbon atoms attached to different oxygen-containing moieties, respectively. CNTs were well distributed between LTO particles, as revealed by STEM observations. Single CNTs or agglomerates by joining LTO particles created cross-links for electron transfer. The relationship and effect between the structural and morphological analysis of spinel Li4Ti5O12 structure modified with carbon nanotubes was examined for the first time in this work. The performed preliminary electrochemical measurements revealed that the best electrochemical properties was obtained for LTO powder modified with 1%wt. of MWCNT. After 50 cycles of charge/discharge processes at the current rate of 1 C, the LTO/1%wt. MWCNT powder retained more than 98% of its specific capacity.Web of Science113art. no. 10827

Preparation of high energy throughput SNOM probes

In this technical note we present technological steps of fabrication of high energy throughput SNOM probes. The core-metal coating interface of probes is corrugated what enhances photon-to-plasmon coupling. A strong evanescent field allows for reduction of aperture diameter, which together with skin depth of metal used for coating decide upon resolution. Probes are made of Ge-doped silica glass fibre, which is hydrogenated to increase its photosensitivity. A Bragg grating is recorded in the cores with UV light diffracted into +1 st/1st diffraction orders on a sinusoidal phase mask. Modulation of the refractive index is connected with different etch rates. Etching with the Turner method is made in aqueous solution of HF acid. A corrugated tapered fibre is then coated with aluminium in a special rotating holder. We present results of this novel multi step technology

Microstructure of Haynes\uae 282\uae Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components

Abstract: The aim of this work was to characterize the microstructure of the as-cast Haynes\uae 282\uae alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix