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21.
Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O2 at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room
temperature, a turnover frequency of 5 s−1 could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon
was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic
oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania
is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as
that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl
concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C3) and glycolic acid (C2) with O2 (1–10 atm) at 308–333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation
in liquid water, H2O2 is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed
to peroxide in the reaction. 相似文献
22.
Monooctadecyl maleate, as a polymerizable surfactant, was synthesized by the mono-esterification of maleic anhydride and octadecanol,
and was utilized to surface-modify nano-Fe3O4 particles. A polymerizable magnetic fluid was obtained by directly dispersing modified nano-Fe3O4 particles into styrene monomer, and the polystyrene/nano-Fe3O4 composite was prepared through free radical polymerization of polymerizable magnetic fluid. The structure and dispersion
status in different dispersion phases of modified nano-Fe3O4 particles were studied by Fourier transform infrared (FTIR) spectrometry, X-ray diffraction (XRD) and transmission electron
microscopy (TEM), respectively. The experimental results show that the nano-Fe3O4 particles modified by monooctadecyl maleate with the size of about 7–10 nm can be uniformly dispersed into styrene and fixed
in the composite during the procedure of polymerization. Thermogravimetric analysis (TGA) and vibrating sample magnetometry
(VSM) indicate that the thermal stability of polystyrene/nano-Fe3O4 composite is improved compared to that of pure polystyrene, and the composite is a sort of superparamagnetic materials. 相似文献
23.
Pulsed Electric Current Sintering of Silicon Nitride 总被引:1,自引:0,他引:1
Motohiro Suganuma Yasunori Kitagawa Shigetaka Wada Norimitsu Murayama 《Journal of the American Ceramic Society》2003,86(3):387-394
Pulsed electric current sintering (PECS) has been used to densify α-Si3 N4 powder doped with oxide additives of Y2 O3 and Al2 O3 . A full density (>99%) was achieved with virtually no transformation to β-phase, resulting in a microstructure with fine equiaxed grains. With further holding at the sintering temperature, the α-to-β phase transformation took place, concurrent with an exaggerated grain growth of a limited number of elongated β-grains in a fine-grained matrix, leading to a distinct bimodal grain size distribution. The average grain size was found to obey a cubic growth law, indicating that the growth is diffusion-controlled. In contrast, the densification by hot pressing was accompanied by a significant degree of the phase transformation, and the subsequent grain growth gave a broad normal size distribution. The apparent activation energy for the phase transformation was as high as 1000 kJ/mol for PECS, almost twice the value for hot pressing (∼500 kJ/mol), thereby causing the retention of α-phase during the densification by PECS. 相似文献
24.
Setsuo?TakakiEmail author Toshihiro?Tsuchiyama Koichi?Nakashima Hideyuki?Hidaka Kenji?Kawasaki Yuichi?Futamura 《Metals and Materials International》2004,10(6):533-539
The microstructure development during plastic deformation was reviewed for iron and steel which were subjected to cold rolling
or mechanical milling (MM) treatment, and the change in strengthening mechanism caused by the severe plastic deformation (SPD)
was also discussed in terms of ultra grain refinement behavior. The microstructure of cold-rolled iron is characterized by
a typical dislocation cell structure, where the strength can be explained by dislocation strengthening. It was confirmed that
the increase in dislocation density by cold working is limited at 1016m−2, which means the maximum hardness obtained by dislocation strengthening is HV3.7 GPa. However, the iron is abnormally work-hardened
over the maximum dislocation strengthening by SPD of MM because of the ultra grain refinement caused by the SPD. In addition,
impurity of carbon plays an important role in such grain refinement: the carbon addition leads to the formation of nano-crystallized
structure in iron. 相似文献
25.
Hideyuki Azegami Liren Zhou Kimihiro Umemura Naoya Kondo 《Structural and Multidisciplinary Optimization》2013,48(1):115-125
This paper presents a numerical solution for shape optimization problems for link mechanisms, such as a piston-crank mechanism. The dynamic behavior of a link mechanism is described by a differential-algebraic equation (DAE) system consisting of motion equations for each single body and constraints of linkages and rigid motions. In a shape optimization problem, the objective function to maximize is constructed from the external work done by a given external force, which agrees with the kinetic energy of the link mechanism, for an assigned time interval, and the total volume of all the links forms the constraint function. The Fréchet derivatives of these cost functions with respect to the domain variation, which we call the shape derivatives of these cost functions, are evaluated theoretically. A scheme to solve the shape optimization problem is presented using the H 1 gradient method (the traction method) proposed by the authors as a reshaping algorithm, since it retains the smoothness of the boundary. A numerical example shows that reasonable shapes for each link such that mobility of the link mechanism is improved are obtained by this approach. 相似文献
26.
Isao Kobayashi Yoichi Murayama Takashi Kuroiwa Kunihiko Uemura Mitsutoshi Nakajima 《Microfluidics and nanofluidics》2009,7(1):107-119
This paper reports the production of monodisperse water-in-oil (W/O) emulsions using new microchannel emulsification (MCE)
devices, asymmetric straight-through MC arrays that were hydrophobically modified. The silicon asymmetric straight-through
MC arrays consisted of numerous pairs of microslots and circular microholes whose cross-sectional sizes were 10 μm. This paper
primarily focused on investigating the effect of the osmotic pressure of a dispersed phase (Πd) on MCE. This paper also investigated the effects of the type of continuous-phase oils and the dispersed-phase flux (J
d) on MCE. The dispersed phases were Milli-Q water and Milli-Q water solutions containing sodium chloride. The continuous phases
were decane (as control), hexane, medium chain triacylglyceride (MCT), and refined soybean oil (RSO) solutions containing
tetraglycerin monolaurate condensed ricinoleic acid ester (TGCR) as a surfactant. At Πd of exceeding threshold, highly uniform aqueous droplets with coefficients of variation of less than 3% were stably generated
via hydrophobic asymmetric straight-through MCs. Monodisperse W/O emulsions with average droplet diameters between 32 and
45 μm were produced using the alkane–oil and triglyceride–oil solutions as the continuous phase. This work also demonstrated
that the hydrophobic asymmetric straight-through MC array had remarkable ability to produce highly uniform aqueous droplets
at very high J
d of up to 1,200 L m−2 h−1. 相似文献
27.
Hideyuki Nakano Hiroyuki Tetsuka Michelle J. S. Spencer Tetsuya Morishita 《Science and Technology of Advanced Materials》2018,19(1):76-100
Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts. 相似文献
28.
29.
New pixel driving circuit using self‐discharging compensation method for high‐resolution OLED micro displays on a silicon backplane 下载免费PDF全文
Kei Kimura Yusuke Onoyama Taizo Tanaka Naobumi Toyomura Hideyuki Kitagawa 《Journal of the Society for Information Display》2017,25(3):167-176
A new 4T2C pixel circuit formed on a silicon substrate is proposed to realize a high‐resolution 7.8‐μm pixel pitch AMOLED microdisplay. In order to achieve high luminance uniformity, the pixel circuit compensates its Vth variation of the MOSFET for the driving transistor internally by using self‐discharging method. Also presented are 0.5‐in Quad‐VGA and 1.25‐in wide Quad‐XGA microdisplays with the proposed pixel circuit. 相似文献
30.
Investigations were made of varistor microstructure, the morphology of Bi2O3 at multiple ZnO grain junctions, Bi2O3/ZnO grain boundaries and ZnO/ZnO grain boundaries (especially whether Bi2O3 is present or not at the ZnO/ZnO grain boundary) by means of high-resolution transmission electron microscopy and X-ray microanalysis in the scanning transmission electron microscope. Bi2O3 at multiple ZnO grain junctions consists of small particles of 0.1m in diameter, and they are vitrified to some extent. It is suggested that bismuth ions dissolve into ZnO grains over a 30 nm range from a Bi2O3/ZnO grain boundary; however, there is no bismuth at ZnO/ZnO grain boundaries. 相似文献