Materials Science Forum Vol. 950

Abstract: The main goal of this study was to optimize the compressive strength of reactive powder concrete (RPC) for an energy storage pile application using response surface method (RSM). The compressive strength of 9 different RPC mixtures along with 3 plain concrete mixtures was determined. Silica fume (SF) content and the water-to-binder ratio (w/b) were selected as parameters to influence the compressive strength of the concrete mixture. RSM regression analysis was used to develop a prediction model of compressive strength. Based on test results and linear interpolation, the combination of 20.46% SF and w/b=0.20 was determined to achieve the highest compressive strength.

Abstract: Nickel and yttria-stabilized zirconia (Ni-YSZ) ceramic-metal composite electrodes are commonly used for solid oxide electrochemical cells because of their good ionic and electronic conductivity. In this study, a thin film of NiO-YSZ was prepared via screen-print method and subsequently reduced to Ni-YSZ. The precursor powder for screen-printing was prepared via glycine-nitrate combustion process. The effect of precursor particle size and of the use of PVP as binder on film uniformity and quality were investigated. For the NiO-YSZ film, scanning electron microscopy (SEM) micrographs and X-ray diffraction (XRD) patterns confirmed that size reduction and the use of binder both improved the quality and uniformity of the deposit without changing the composition of the sintered film. SEM with energy-dispersive spectroscopy (EDS) showed elemental mapping of unreduced and reduced films, revealing micro grain size faceted particles of NiO and Ni, while smooth and much larger YSZ grains were also observed. XRD of reduced Ni-YSZ film revealed that the NiO peaks had been replaced by Ni.

Abstract: Natural rubber latex was chemically modified by enzymatic deproteinization, degradation, and epoxidation to produce deproteinized liquid epoxidized natural rubber (DP-LENR). Polyvinylidene difluoride (PVDF) was blended with DP-LENR and then electrospun to produce nanofibers. Scanning electron microscopy shows reduction in the fiber diameter and beading formation with increasing concentration of DP-LENR. Smooth surface of nanofibers suggests miscibility and chemical compatibility of PVDF with low concentration of DP-LENR. Infrared spectroscopy and X-ray diffraction analysis show the addition of DP-LENR has no effect on chemical structure and crystallinity of electrospun PVDF.

Abstract: Zirconium oxide was obtained via traditional precipitation from a ZrOCl₂ solution with ammonia followed by drying at 110 °C. The carbon-coated samples were synthesized by calcination of the pristine zirconia mixed with polyvinylalcohol. The obtained ZrO₂@C samples of core-shell structure as well as the reference samples of pristine zirconia were calcined at different temperatures from 500 to 1400 °C. All the materials were examined by a set of physicochemical methods (a low-temperature argon adsorption, transmission electron microscopy, X-ray diffraction analysis, photoluminescence spectroscopy). It was found that the carbon coating prevents the sintering of the oxide nanoparticles, which allows one to maintain the specific surface area, the size of the oxide core and, finally, stabilize its phase composition. Transformation of the cubic phase into monoclinic phase becomes significantly complicated. Thus, 40% of the cubic phase was detected even after calcination of the ZrO₂@C sample at 1400 °C. Moreover, the carbon-coated samples treated at elevated temperatures with subsequent removal of the carbon shell were found to possess the highest concentration of the defects related to a presence of the anion vacancies in zirconia.

Abstract: The aims of this study are to synthesize and characterize gold nanoparticles (AuNPs) crosslinked by pH-responsive polymer poly (acrylic acid) (PAA) and its application for detection of some analytes in herbal medicine product. In this study, a pH-responsive polymer, poly (acrylic acid) was prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization method. The polymer was then cross-linked by gold nanoparticles, which was synthesized by the Turkevich method. The response of the AuNPs-crosslinked PAA was observed by the color change from red to blue at a specific pH (4-5) and was characterized by TEM. The reversible color change was resulted from aggregation and disaggregation of the AuNPs due to the shrinking and swelling of the polymer when different pH was introduced as a stimulant. This sensor has the capability of recognizing analytes such as aspirin and tolbutamide added in the herbal medicine product at the concentration of 0.04-0.05 M.

Abstract: Ni-Pd alloy was prepared by a co-precipitation technique. Catalytic decomposition of a model chlorinated hydrocarbon (1,2-dichloroethane) was performed in a quartz flow-through reactor system. Both the temperature regime and the composition of the reaction mixture were varied during the experiments. Concentration of 1,2-dichloroethane was found to affect significantly the kinetics of the process, the yield of the nanostructured carbon product and its textural and morphological characteristics. In terms of optimal temperature, the maximum carbon yield was obtained within a range of 650-670 °C.

Abstract: Silver-doped TiO₂ nanotubes (Ag-TiNTs) were synthesized in a top-down approach by single-step anodization of titanium sheets. The highly-ordered array of Ag-TiNTs was confirmed by scanning electron microscopy with an average inner diameter of 41.28 nm and a wall thickness of 35.38 nm. Infrared spectroscopy confirmed the presence of O-Ti-O bonds. Analysis of the X-ray powder diffraction profiles showed the characteristic peaks for anatase and titanium for both pristine TiNTs and Ag-TiNTs. Ag-doping caused no observed changes in the crystalline structure of pristine TiNTs. High-definition X-ray fluorescence spectroscopy revealed that the synthesized Ag-TiNTs have 0.05 wt% Ag-loading. Even at low Ag-loading, the Ag-TiNTs were shown to be photo-active, achieving 10.13% degradation of Acid Orange 52 under UV illumination after 120 min.

Abstract: Utilizing two different synthesis methods, solid-state reaction and glycine-nitrate process, composite lanthanum strontium manganite and yttria-stabilized zirconia (LSM-YSZ) powders were prepared. The powders were then mixed with 0, 5, and 10 wt% carbon black nanosized pore former and pressed into 10mm diameter pellets then sintered at 1150 °C for 5 hours. The pellet composition and microstructure were investigated using FTIR, XRD, SEM-EDX, and their density and open porosity were measured using the Archimedes principle. The resulting microstructure of the composite pellets obtained using the two fabrication methods and different pore former weight percentages were studied and compared. It was found that the addition of 5 wt% carbon black pore former yields about 40% desired open porosity, and synthesis via GNP results to finer and more evenly distributed LSM and YSZ particles.

Abstract: Solid electrolytes such as lithium lanthanum zirconate have shown a lot of promise in an all-solid-state Lithium-based battery since the discovery of its highly conductive cubic garnet structure. In this study, different concentrations of Al-doped Lithium Lanthanum Zirconate (Al-doped LLZ) having the formula of Li_7-.3xAl_xLa₃Zr₂O₁₂ with x = 0.1,0 .2, 0.3, were synthesized via modified Pechini method and the effect of sintering temperatures, 1150 and 1200 °C, on the resulting properties were investigated. X-ray diffraction results have shown that cubic Al-doped LLZ can be obtained at a lower temperature using Pechini method. Significant effect to the conductivity on the different sintering temperatures was observed for the 0.1 Al-doped LLZ. With the different studied compositions synthesized via modified Pechini method, it was revealed that the 0.2 Al doped LLZ sintered either at 1150 or 1200 °C showed the highest conductivity of about 1.4x10^-4 S/cm.

Abstract: Enhancement in plasmonic response of metal nanoparticles in the form of metal/metal oxide nanocomposites is very interesting from both the theoretical understanding and application. Metal based oxide/Ag nanocomposites were synthesized by polyol process. Metal oxide nanoparticles present in nanocomposites as core and noble metal as a shell are of interest in investigation of plasmonic behavior of noble metals and sensing application. Cobalt ferrite (CoFe₂O₄) and ZnO were used as oxide core in the form of spherical and rod nanostructures respectively. Presence of Ag was confirmed by XRD and SEM analysis. In this paper we summarize the synthesis and characterization of plasmonic properties of composite nanostructures. Optical absorption studies performed on CoFe₂O₄@Ag and ZnO@Ag exhibit sharp plasmonic resonance but shifted towards lower wavelength (blue shift). An attempt has been made to explain this shift using the Mie scattering calculations based on size variation and change in the dielectric of the surrounding medium.