Invariant Physical Properties in High Temperature Superconductivity

Applying our recently proposed slave-boson theory (Lee and Salk in Phys. Rev. B 64:052501, 2001; Phys. Rev. B 71:134518, 2005) of the t−J Hamiltonian which reproduces the dome-shaped phase diagram and consistently fits other physical properties including optical conductivity involved with charge dynamics, we study the magnetic susceptibility by resorting to a computed phase diagram. Specifically, we discuss the predicted invariant physical properties of both the magnetic susceptibility and the phase diagram.     

Synthesis of [10Ῑ]‐Oriented (Na1−xKx)NbO3 Platelets by Using Hydrothermally Produced (K8−8xNa8x)Nb6O19·nH2O Precursor

Micrometer size [10] (N_1?xK_x)NbO₃ (NKN) platelets were synthesized by annealing (K_8?8xNa_8x)Nb₆O₁₉·nH₂O (KNNH) precursors at 500°C. The plate‐like KNNH precursors were produced from (1?y)NaOH‐yKOH + Nb₂O₅ specimens using the hydrothermal process at 160°C. The size of the NKN platelets was similar to that of the KNNH precursor, but the surfaces of the NKN platelets were rough while the KNNH precursor had a smooth surface. The formation of a rough surface is related to the vigorous evaporation of the H₂O from the KNNH platelets during the annealing process at high temperatures. NKN platelets with smooth surfaces could be synthesized using KNNH platelets, which were heated to 150°C to evaporate H₂O before annealing at 500°C. These NKN platelets can be used for the fabrication of textured NKN ceramics.     

Controlled synthesis of nanoplate,nanoprism and nanopyramid-shaped CdSe decorated on porous TiO2 photocatalysts for visible-light-driven hydrogen evolution

Herein, we report a successful synthesis of porous TiO₂ monoliths decorated with unique nanoplate, nanoprism, and nanopyramid-shaped CdSe particles through a mild selenylation of CdO embedded inside porous TiO₂ monoliths via a hydrothermal method in a very controlled manner. Compared with pure TiO₂, as-synthesized CdSe/TiO₂ photocatalyst not only enhances light absorption but also leads to a highly efficient charge-carrier separation. Particularly, the nanoplate-shaped 7% CdSe/TiO₂ photocatalyst (molar percentages of CdSe to TiO₂ is 7:100) exhibits an exceptional hydrogen evolution rate up to 3650?μmol?h^?1 g^?1 without resorting to any noble-metal co-catalysts under visible-light irradiation owing to synergistic effects envisaged by a rational material design. Our results may provide a useful strategy to develop a highly-efficient visible-light-driven hydrogen production system via water splitting.     

Recent progress in hydrogenase and its biotechnological application for viable hydrogen technology

Despite increasing interest in hydrogen (H₂) as an alternative energy carrier, the current production of H₂ still depends on fossil fuels. Biotechnological hydrogen production can provide a more sustainable way to generate H₂. Hydrogenases are key enzymes involved in hydrogen metabolism of microorganisms with roles of H₂ oxidation or evolution. They have potential applications in H₂ production in vivo, in vitro and fuel cell. Important achievements have been made over the past decade in our understanding of hydrogenase and its biotechnological application as catalyst for H₂ production and fuel cell. This review summarizes recent progress in the study of hydrogenases, involving strategies for biosynthesis, maturation process, isolation of novel hydrogenases, heterologous expression system, structural feature of oxygen (O₂)-tolerant hydrogenases, and biotechnological applications for viable H₂ technology.     

Rheology and curing characteristics of dual-curable automotive clearcoats using thermal radical initiator derived from O-imino-isourea and photo-initiator

The curing characteristics of clearcoats, including a thermal curing initiator (TRI) newly designed from O-imino-isourea and photo-initiator (PI), were investigated by means of different mono-curing and dual-curing pathways. The competitive relationship between TRI and PI on the curing pattern, reacting with acrylate double bonds in a clearcoat was elucidated by altering the UV and thermal sequence in the dual-curing process, through various experimental methods. From the rheological properties of clearcoats along the curing time, two dual-curing methods showed the different evolution of curing patterns. In the UV–thermal dual-curing case, the initial infusion of UV light promoted free radical polymerization during the subsequent thermal curing by generating considerable free radicals, and exhibiting a higher growth rate of elastic modulus during the curing in comparison with the thermal–UV dual-curing case. However, the final modulus value in the thermal–UV dual-curing case was higher due to the suppression of thermal curing by the steric hindrance in the UV–thermal dual-curing. The level of crosslinked networks in clearcoats via different curing steps can be explicitly figured out from the double bond conversion from FT-IR, curing pattern from rigid-body pendulum test, and scratch properties from nano-scratch test.     

Effect of Stacking Layers on the Microwave Dielectric Properties of MgTiO3/CaTiO3 Multilayered Thin Films

Effect of stacking layers on the microwave dielectric properties of the MgTiO₃/CaTiO₃ (MTO/CTO) multilayered thin films prepared by the metalorganic solution deposition technique (MOSD) was investigated. As the thickness of CTO film in the MTO/CTO multilayered films increased, the dielectric constant ( K ) increased and temperature coefficient of dielectric constant ( TCK ) changed from positive to negative values by dielectric series mixing rule. Especially, MTO(100 nm)/CTO(200 nm) multilayered films exhibited a TCK of +10 ppm/°C, indicating temperature stability. The dielectric losses (tan δ) of MTO/CTO multilayered films increased with an increase of CTO layers. This result was attributed to the fact that the stresses induced by the higher thermal-expansion coefficient of CTO than that of MTO. Also, as compared with MTO(100 nm)/CTO(200 nm) film, the K and TCK of MTO(50 nm)/CTO(200 nm)/MTO(50 nm) film were not changed, but the dielectric losses increased. This result indicated that the dielectric loss was affected by the number of interfaces between CTO and MTO layers.     

Hydrogen-induced change in microstructure and properties of steels: 18Cr10Mn–0.4N vis-à-vis 18Cr10Ni

ABSTRACT

Cr–Mn–N stainless steels have a cost and strength advantage over conventional Cr–Ni stainless steels. In this study microstructure and mechanical property of hydrogen-charged 18Cr10Mn-0.4N was compared with 18Cr10Ni austenitic stainless steel. This is the first such study for 18Cr10Mn–0.4N austenitic stainless steel. Electron microscopy was used to compare the deformed microstructure of the uncharged and hydrogen-charged specimens. The results are discussed in view of the current knowledge on hydrogen embrittlement. The 18Cr10Mn–0.4N steel suffered higher embrittlement mainly because it absorbed moref hydrogen.     

High roughness Ag back reflector on a metal underlayer for thin film solar cell applications

The roughness development of Ag film was investigated for potential as a back reflector material in thin film solar cells on flexible stainless steel (STS) substrates. The influence of metal underlayers was evaluated in order to obtain a rough Ag film at a low deposition temperature (≤400 °C). By depositing Ag on a 100 nm Al underlayer to induce Ag–Al alloying, the film roughness was increased three times more than that of Ag films on bare STS at 400 °C. The Ag film deposited on an Al underlayer at 350 °C exhibited 75 nm roughness and uniformly distributed crystallites, which was effective for visible light scattering. The Ag–Al alloy phase was also controlled using the thickness ratio of Ag and Al. The present work clearly demonstrated that an Ag back reflector film with a higher roughness could be fabricated through inserting a metal underlayer at a deposition temperature much lower than the 500 °C that has been reported in earlier works.     

Effect of nanocarbides and interphase hardness deviation on stretch-flangeability in 998 MPa hot-rolled steels

By performing various laboratory hot-rolling simulation tests, effective rolling conditions for steel with a composition (mass %) of 0.06C–2.0Mn–0.5Si–0.5Cr–0.2(Ti + Nb + V) was studied. Very remarkable mechanical properties were obtained when the coiling simulation temperature was 650 °C: a hole-expanding ratio of 65%, total elongation of 19%, and ultimate tensile strength of 998 MPa were achieved in the hot-rolled state. These results were associated with the Ti–Nb–V multi-microalloyed carbides (10–50 nm in size) precipitated in the ferrite matrix, and with the minimized deviation in interphase hardness.