Advanced Materials Research Vol. 1098

Abstract: Recently there has been a very high demand for small scale magnetic storage devices. The industry sector has consistently demanded sub micron or even nanometer scale magnets. Magnetic thin films often contain several layers of coating. For the purpose of this study, we prepared thin film magnets by spin coating a precursor containing iron into a glass substrate. The thickness of the films was controlled by the spin rate. Precursor films on the substrate were then annealed to 600⁰ C for 3 hours in air. The micro structure of iron in the films was investigated using the pre-edge feature that appears in the X-ray Absorption Near Edge Structure (XANES) for samples containing different iron layers. The main absorption edge peak position and pre-edge energy position were identical in all of the samples. This indicates that there was no change in the charge state of the iron regardless of the number of layers. However the intensity of the pre-edge feature decreases as number of layers increases which shows a decrease of Fe-O compounds as the number of layers increases.

Abstract: Two key issues in graphene-based p-n junction applications are the manipulation of the type and density of carrier in graphene and the development of a facile fabrication process. Here we reported the formation of graphene films with tunable carrier type by doping of ethoxylated polyethylenimine (PEIE) and Au nanoparticles (NPs). The carrier density of doped graphene can be tuned by altering the concentration of the dopant solutions. The doping effects of PEIE and Au NPs on graphene were monitored by resonant Raman spectroscopy and electrical transport measurements. Graphene p-n junction arrays were assembled by simple soft-lithographic patterning and cross-stacking of n-and p-type doped graphene films, showing a graphene p-n junction behavior with two V_CNDP.

Abstract: Yttrium doped barium cerate is considered a promising electrolyte material for solid oxide fuel cell applications due to its excellent proton conductivity. The proton conductivity characteristics of the ceramic material can be influenced by the different synthesis processing parameters. This study aimed to obtain yttrium doped barium cerate BaCe_1-xY_xO_3-δ (x = 0.15, 0.20) using a sol-gel modified Pechini method. The phase formation and surface morphology of the yttrium doped barium cerate were investigated using x-ray diffraction and scanning electron microscopy. The thermal decomposition of the calcined ceramic material was examined using thermogravimetric analysis. Diffraction analysis confirmed the formation of perovskite crystalline structure with the presence of secondary phase yttrium doped ceria. Larger grain size with homogeneous distribution and coalescence was observed in the sintered BaCe_0.80Y_0.20O_3-δ.

Abstract: The gamma irradiation was utilized to facilitate the synthesis of poly (glycerol sebacate)-co-lactic acid (PGS-co-LA). The effect of methyl methacrylate (MMA) crosslinker and varying dosage of irradiation to the structural composition and thermal properties of the synthesized PGS-co-LA was investigated. Compositional analyses of the polymer materials using infrared spectroscopy confirm the covalent formation of ester linkage. The use of methyl methacrylate enhances the formation of the characteristic bonds in the polymer structure. The intensity of these peaks increases with increasing irradiation dosage and high amount of crosslinker. The melting temperature of the PGS-co-LA becomes more negative with the incorporation of high amount of MMA.

Abstract: Rice husk is the covering of rice seeds and a by-product of milling rice grain. This study is conducted to investigate the production of silica (SiO₂) formed from waste rice hull (RH) at different processing temperatures and study its structure, morphology, and thermal properties. Thermal analysis by thermogravimetric analysis (TGA) of the dried RH showed two mass-loss steps associated to the moisture desorption and thermal decomposition. Powder X-ray diffraction patterns of the rice hull calcined at 550 ^oC showed a purely amorphous SiO₂ structure while those calcined for 900 ^oC for 1 hour and for 3 hours showed a glass-ceramics and crystalline SiO₂ structure, respectively. This structural result is supported by the results obtained from the FTIR and Raman analyses of the samples. On the other hand, the Scanning electron microscopy (SEM) images showed the morphology of the samples revealing an increasing particle and grain size of the samples calcined at higher temperatures and longer heat treatment duration. In addition, Energy dispersive X-ray (EDX) spectra of both amorphous and crystalline SiO₂ samples confirm that the sample contains mostly silicon and oxygen. Thus, in this study, the desired form of either amorphous or crystalline SiO₂ from waste rice hull can be successfully obtained by controlled heat treatment.

Abstract: One of the promising material for proton-conducting solid electrolyte operating at intermediate temperature range (400-600 °C) is the Yttrium-doped BaZrO₃ (BZY) due to its high conductivity and chemical stability. In this study, a modified citrate-nitrate combustion method (Pechini method) has been employed for BZY powder preparation. A stoichiometric amounts of starting nitrates and oxide raw materials with nitric acid, citric acid and ethylene glycol for the synthesis of 20 mol% Y-doped BaZrO₃ (BZY20) were prepared, then calcined and sintered at 1000 °C for two heat treatment durations of 24 hours and 48 hours. The obtained BZY20 powder samples have been fully characterized for its structure, morphology, and thermal properties. From the X-ray diffraction (XRD) results, the sample sintered for 48 hours showed a cubic phase of BZY20 which can be indexed to a Pm3m cubic structure which is also supported by Raman analysis. The calculated lattice parameter is 4.2067 Å which is higher than the reported lattice parameter of a pure BaZrO₃ (BZ) of 4.1930 Å which indicates a successful doping due to higher ionic radius of Y³⁺ dopant as compared to Zr⁴⁺ in the B-site ABO₃ perovskite sub-lattice. In addition, SEM-EDX analyses of the sintered pellet revealed a uniform distribution of Yttrium dopant in the BZY20 prepared solid electrolyte.

Abstract: Intermediate temperature solid oxide fuel cells (IT-SOFCs) operating at 400-700°C utilizes proton conducting electrolytes and are now being one of the focus of many research studies with regards to efficient, clean power sources and energy conversion. Potential electrolyte materials include acceptor-doped barium zirconates and barium cerates. In this study, preparation of a core-shell structured proton-conducting solid electrolytes of 20 vol% BaZr_0.8Y_0.2O_3-δ (20BZY20) for the core and 80 vol% BaCe_0.8Y_0.2O_3-δ (80BCY20) for the shell is done by wet chemistry route. The synthesized core-shell structured material (20BZY20/80BCY20) is developed to possibly address the problem of high grain boundary impedance of Y-doped BaZrO₃ and low chemical stability of Y-doped BaCeO₃. The obtained samples were characterized for its structure, thermal stability, morphology and elemental distribution of the material. At a lower sintering temperature of 1150°C, a densified pellet was obtained as observed by SEM analysis. The diffraction pattern of 20BZY20/80BCY20 powder shows two distinct phases corresponding to BZY20 and BCY20 suggesting a successful synthesis of the core-shell solid electrolyte.

Abstract: The modification of the surface of cellulose-containing materials by copolymers of polyglycidyl methacrylate (PGMA) obtained by means of two ways: acylation of PGMA by stearic acid and copolymerization of glycidyl methacrylate and lauryl methacrylate is proposed. It is demonstrated, that the use of obtained copolymers allows to get the superhydrophobic coatings on the surface of cellulose-containing materials with reaching of contact angles up to 161°. Such modified materials can be used as filters for the separation of the water-oil emulsions.

Abstract: Rare-earth-doped BaCeO₃ and BaZrO₃ electrolytes with perovskite structure have been studied extensively in developing proton conducting intermediate temperature SOFC. Acceptor doped alkaline earth cerates and zirconates have been thoroughly studied because of the great interest in their possible applications as solid proton conductors. The perovskite type proton conductor BaCe_0.5Zr_0.35In_0.1Zn_0.05O_3-δwas prepared in the traditional solid state reaction method. The density of the sample obtained about 96% of the theoretical density after sintering at 1350 °C and X-ray diffraction study confirms the pure phase. Rietveld refinement of the neutron and X-ray powder diffraction data shows that this material crystallizes in the orthorhombic symmetry in the space group Pm3m. Particle size measurement shows that the average particle size is about 2.4 μm. The average thermal expansion at 894 °C was 9.49 x 10^-6/°C. Thermogravimetric analysis (TGA) traces obtained for the sample on heating in wet air shows that the maximum proton uptake occurs from 595 °C.

Abstract: We carried out simulations of contact interaction between BCC iron crystallite and various pure FCC metals under shear loading by means of molecular dynamics. It was shown that the result of this interaction is the transformation of FCC atomic lattice of contacted material into BCC one within a thin layer in the contact zone. The results of simulations can be used to control strength of the interfacial layers of coated materials, as well as to understand the processes which are taking place in surface layers of materials under the contact.