Grain Refinement by Cyclic Displacive Forward/Reverse Transformation in Fe-High-Ni Alloys

A novel method for grain refinement of martensite structures was proposed, in which transformation strain is accumulated by cyclic displacive forward and reverse transformations. This method can refine martensite structures in an Fe-18Ni alloy because a high density of austenite dislocations is introduced by a displacive reverse transformation in addition to an inheritance of dislocations in body-centered cubic martensite into austenite during cyclic transformation. The addition of a small amount of carbon accelerates structure refinement significantly, which results in the formation of ultra-fine-grained structures after ten cycles.

     

Selective hydrogenation of 4-isobutylacetophenone over a sodium-promoted Pd/C catalyst

The effect of sodium promotion on the selective hydrogenation of 4-isobutylacetophenone, 4-IBAP, was investigated over a Pd/C catalyst. A precipitation and deposition method was used to prepare the catalyst, and sodium was promoted on the Pd/C catalyst via post-impregnation while varying the sodium content. The sodium-promoted Pd/C catalyst resulted in a significantly improved yield greater than 96% of the desired product, 1-(4-isobutylphenyl) ethanol (4-IBPE), compared with the non-patented literature results under a mild hydrogenation condition. A detailed hydrogenation network over the Pd/C catalyst was suggested. The reaction mechanism for the yield and selectivity enhancement of 4-IBPE induced-by the promoted Pd/C was elucidated in relation to the geometric and electronic effects of reactant molecules in the microporous support depending on the reaction steps.     

One-pot synthesis of hierarchically macro/mesoporous Al2O3 monoliths from a facile sol–gel process

Based on the preparation of ordered mesoporous Al₂O₃ powder using P123/isopropoxide aluminum/HNO₃ reaction system, hierarchically macro/mesoporous alumina monoliths were successfully fabricated by introducing PEG8000 as the phase-segregation initiator to generate macropores. The effects of PEG8000 and P123 contents on the monolithic and hierarchical morphology were investigated systematically. With appropriate selection of the starting composition, monolithic skeletons with bimodal macropores interconnected by mesostructured walls can be synthesized in both the dried gels and calcined samples. The well-defined macropores are in close-celled structure dispersed in large-sized mesoporous matrix. The mesopore size can be regulated by adjusting the PEG8000 content while its shape is governed by P123 content. The well-developed alumina monolith, MMA-P20, exhibits high surface area of 287 m²/g and narrowly distributed mesopores with median size of 13 nm after calcinaton.     

Strength improvement and purification of Yb2Si2O7‐SiC nanocomposites by surface oxidation treatment

A two‐step processing was developed to prepare Yb₂Si₂O₇‐SiC nanocomposites. Yb₂Si₂O₇‐Yb₂SiO₅‐SiC composites were first fabricated by a solid‐state reaction/hot‐pressing method. The composites were then annealed at 1250°C in air for 2 hours to activate the oxidation of SiC, which effectively transformed the Yb₂SiO₅ into Yb₂Si₂O₇. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. The mechanism for crack healing and silicate transformation have been proposed and discussed in detail.     

Crystallography and Interphase Boundary of Martensite and Bainite in Steels

Grain refinements in lath martensite and bainite structures are crucial for strengthening and toughening of high-strength structural steels. Clearly, crystallography of transformation plays an important role in determining the “grain” sizes in these structures. In the present study, crystallography and intrinsic boundary structure of martensite and bainite are described. Furthermore, various extrinsic factors affecting variant selection and growth kinetics, such as elastic/plastic strain and alloying effects on interphase boundary migration, are discussed.     

Web Block Extraction System Based on Client-Side Imaging for Clickable Image Map

We propose a new Web information extraction system. The outline of the system and the algorithm to extract information are explained in this paper. A typical Web page consists of multiple elements with different functionalities, such as main content, navigation panels, copyright and privacy notices and advertisements. Visitors to Web pages need only a little of the pages. A system to extract a piece of Web pages is needed, our system enables users to extract Web blocks only by setting clipping areas with their mouse. Web blocks are clickable image maps. Imaging and detecting hyperlink areas on client-side are used to generate image maps. The specialty of our system is that Web blocks perfect layouts and hyperlinks on the original Web pages. Users can access and manage their Web blocks via Evernote, which is a cloud storage system. And HTML snippets for Web blocks enable users to easily reuse Web contents on their own Web site.     

Synthesis of β-MoO3 whiskers by the thermal evaporation method with flowing oxygen gas

β-MoO₃ is a monoclinic phase of MoO₃; it has been shown to be a promising material that can replace α-MoO₃ in chemical, optical, electronic, and electrochromic applications. However, the difficulty in synthesizing β-MoO₃ with a one-dimensional (1D) morphology has limited its use in applications requiring a large specific surface area. In the present work, β-MoO₃ whiskers were prepared by thermally evaporating α-MoO₃ powder in a tube furnace at temperatures (T_f) from 750 to 1000°C and under flowing O₂ gas. The collected samples were identified as mainly β-MoO₃ by X-ray diffraction measurements, and the highest purity β-MoO₃ was obtained at T_f = 1000°C. Scanning and transmission electron microscopy observations showed that whiskers with a width of 10 nm were successfully synthesized by this method. The whiskers were confirmed to be β-MoO₃ via lattice image analysis. Measurements of the temperature distribution in the tube furnace and comparisons with the Mo–O phase diagram led to the conclusion that the whiskers formed via a vapor–solid route. Prepared β-MoO₃ whiskers were compared with α-MoO₃ powder via the X-ray photoelectron spectroscopy characterization method. By elucidating the β-MoO₃ whisker synthesis mechanism, this research provides guidance for the large-scale production of β-MoO₃ whiskers.     

Structures and field emission properties of heat-treated C60 fullerene nanowhiskers

The structures and field electron emission properties of C₆₀ fullerene nanowhiskers were investigated. The single crystalline C₆₀ fullerene nanowhiskers were straight, surrounded by facets, and had a uniform submicrometer diameter along the long axis. Heat treatment of the nanowhiskers drastically transformed the inner structure from C₆₀ crystal to glassy carbon, while the outer structure kept its original morphology despite heat treatment. Field electron microscopy images of the heat-treated nanowhiskers showed striped patterns, characteristic of an agglomerate of crumpled graphitic layers.     

Facile preparation of a polysiloxane-based hybrid composite with highly-oriented boron nitride nanosheets and an unmodified surface

A facile technique was developed to fabricate polysiloxane-based hybrid composite films containing boron nitride (BN) nanosheets using a nanopulse-width electric field. BN nanosheets assumed anisotrophic alignment under the electric field, without requiring surface coating with metallic nano particles despite the wide band gap. BN was dispersed by sonication in a pre-polymer polysiloxane mixture. The homogeneous suspension was cast on a glass spacer and subjected to either a DC electric field or a nanopulse-width electric field before the mixture was cured through polymerization. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that BN nanosheets in the polysiloxane matrix were aligned with high anisotropy to the electric field direction, which was perpendicular to the film plane. The transmittance of the film samples, measured by UV–visible spectrometry, indicated that the composite, prepared using a nanopulse-width electric field manifested a significantly improved transmittance, compared with composites prepared without using the electric field.