Advanced Materials Research Vol. 702

Abstract: This paper examines the effect of metal loading (Zr-, V-, Ti-, and K-compounds) on the hydrogen storage property of mechanically milled graphite. The hydrogen adsorption took place at room temperature and 11 MPa measured by thermal volumetric analysis. The results showed that the graphite loaded with ZrCl₄ provided a maximum hydrogen storage capacity of 0.6 wt%. Moreover, a milling time of 2 h seems to be the best, offering the highest hydrogen adsorption capacity due to the high specific surface area and the appropriate pore diameter created after the milling. In addition, it was found that the transition metals (ZrCl₄ and VCl₃) could stabilize the graphite structure and enlarge the gap between the grapheme layers to be suitable trapping sites for hydrogen adsorption. On the other hand, the K₂CO₃ and TiO₂ loaded graphite did not show any improvement for hydrogen adsorption.

Abstract: The La_0.3Sr_0.7Ti_0.9Nb_0.1O₃ (LSTN) is a good anode material in solid oxide fuel cell (SOFC) due to its resistance to sulfur poison and carbon fiber deposition. The LSTN was studied by a novel microwave processing in activated carbon and flowing atmosphere of (5%H₂+95%Ar). The pure perovskite structure is obtained for different microwave power and duration to indicate that the fast microwave reduction process could maintain stable perovskite structure. The conductivity of LSTN increases with the decrease of flow rate of 5%H₂+95%Ar. More semiconducting characteristics but less metallic conductivities are achieved by microwave process. A stable microwave power 300W and a dwell time 12 min with an appropriate flow rate 40 cc/min can achieve the best conductivity of LSTN. The microwave reduction sintering obtains high conductivity of LSTN which is far higher than the one by conventional sintering at 1500°C-3 h.

Abstract: A series of novel azo-containing twin liquid crystalline (LC) epoxy monomers were cured with anhydrides without extra catalyst and the curing kinetics was investigated by non-isothermal differential scanning calorimetry (DSC) technique. The results showed that the effect of phase behavior on activation energy (Ea) was very great. The chemical kinetic control and diffusion control mechanisms dominant the curing together, which gives a larger value of Ea. Azo group also served as a catalyst to accelerate the curing reaction.

Abstract: A series of novel azo-containing twin liquid crystalline (LC) epoxy monomers were cured with anhydrides without extra catalyst and the curing kinetics was investigated by non-isothermal differential scanning calorimetry (DSC) technique. The effect of Azo group on the Curing Kinetics of Epoxy/anhydride System was investigated and the result showed that Azo group served as a catalyst to accelerate the curing reaction. The curing mechanism was confirmed by the UV-Vis spectrum.

Abstract: The anodized TiO₂ nanotube arrays (TNAs) have a benefit to provide large surfaces and straight electron transmitting routes to the electrode. However, it is difficult to fulfill with solid state electrolytes or photosensitive materials into the long TiO₂ nanotubes. The substrate of Ti/wave-like TiO₂ was prepared by peel-off the TNAs. The In₂S₃ buffer layer between wave-like TiO₂ and CuInS₂ determines the photosensitivity of the Ti/wave-like TiO₂/In₂S₃/CuInS₂ thin structure. The In₂S₃ and CuInS₂ are well-crystallized at 300oC. The CuInS₂ phase forms in In₂S₃ layer due to Cu diffusion independent on the slight loss of sulfur. The CuInS₂ direct deposition on Ti/wave-like TiO₂ substrate can not exhibit photosensitivity. When CuInS₂ deposited on In₂S₃ to form Ti/wave-like TiO₂/In₂S₃/CuInS₂ structure, the short-circuit current and the open-circuit voltage increase with the thickness increase of In₂S₃ layer while illuminated by 50 mW/cm₂ white light.

Abstract: The original micro structure of the base metal is significantly affected by a welding thermal cycle, irrespective of the type of the heat source. Hence, new phases and different grain size result in the welding bead. The tensile strength of the overall structure is affected in turn. Tensile tests are normally conducted to eventually test a square butt joint configuration. In conjunction, micro hardness is thought to be a good indicator to predict where the fracture would occur in the welded structure. Referring to common metal alloys for aerospace and considering a diode-pumped disk-laser source, the response of the base metal to the laser beam is investigated in this paper. Autogenous welding of aluminum alloy 2024, autogenous welding of titanium alloy Ti-6Al-4V and dissimilar welding of Haynes 188 with Inconel 718 are discussed, with respect to micro structure changes in the fused zone and in the heat affected zone. The failure mode is examined.

Abstract: Galvanic corrosion behavior of 2A12/45 couple under different tensile stresses is investigated using the electrochemical test. Surface morphologies of the specimens are observed by scanning electron microscopy (SEM). The results show that the applied stress have an important effect on the galvanic corrosion of 2A12/45 couple. The couple current density and galvanic corrosion sensitivity increases with the increase of the applied stresses.

Abstract: The Uranium and Titanium corrosion rates are described by a Tafel’s relationship, and the cathodic protection of Uranium is a function of a Wagner number. A numerical simulation of galvanic corrosion of Uranium surface under thin layer electrolyte is presented. The model considered that the effect of a circular defect and oxygen reduction and corrosion in the Uranium surface, the effect of electrolyte thickness and conductivity and defect radius on corrosion current distribution of Uranium with is investigated. The results shows that the corrosion rate at the center is non-uniform, and it could lead to the formation of a hemispherical-shaped pit. And the effect of radius is to increase the importance of the electrode kinetics relative to ohmic resistance, and to increase the potential difference between the center and edge of the Uranium surface, resulting in non-uniform corrosion current distribution.

Abstract: The interaction among Lanthanum, Arsenic and Iron at 1223K were studied by means of electron probe microanalysis, optical microscopy and X-ray diffraction. The result shows that the gray phase might be a ternary compound La10Fe50As40, and the binary compound LaAs and the ternary compound La10Fe50As40 are the main interaction products when the atomic ratio of La to As is 1:3. The eutectic compound Fe2As can be precipitated from ferrite with the temperature decreasing.

Abstract: Oxygen plasma was utilized to etch the epitaxial graphene films grown on carbon-terminated 6H-SiC substrate. XPS spectra show that the intensity ratio between the graphene peak and SiC peak decreases with oxygen plasma etching time. It indicates that with increasing etching time from 0 to 42 s, the thickness of graphene dramatically decreases from eight to one monolayers following a first-order exponential decay function. Meanwhile, AFM images show that the ridges among domains are preferred to be etched by oxygen plasma and they will almost disappear after etched for 42 s. It indicates that the oxygen plasma will not decrease the mobility of graphene layer obviously when the graphene thickness is over two monolayers; however, further etching the graphene with thickness less than two monolayers will leads to significantly decrease the mobility due to the formation of many more defects.