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排序方式: 共有823条查询结果,搜索用时 15 毫秒
811.
The effect of chemical reaction rate on the generation of titania nanoparticles by chemical vapor deposition using two different precursors was investigated by FTIR, XRD, and microscopy. The size of the primary particle exhibited a minimum with increasing reactor temperature. At lower reaction temperatures, the continuous and gradual formation of titania monomers occurred followed by coagulation and/or surface reaction on the existing particles. In addition, unreacted precursor condensed at the reactor exit. As the reaction temperature increased, the rate of monomer production increased, the dominant characteristics of particle growth were coagulation and sintering. The reactor temperature where the minimum primary particle diameter was produced was different for the two precursors due to differences in chemical reaction rates. Phase composition as well as the primary particle diameter of product titania were affected by the chemical reaction rate. Particle-laden reactor wall enhanced the precursor conversion at low reactor temperatures, where surface reactions compete effectively with gas-phase precursor conversion. 相似文献
812.
Ryoichi Furushima Yuki Nakashima Yutaka Maruyama Kiyoshi Hirao Tatsuki Ohji Manabu Fukushima 《Journal of the American Ceramic Society》2023,106(8):4944-4954
Two mechanical properties, fracture toughness (KIC) and bending strength (σ), of silicon nitride (Si3N4) ceramics were determined from their microstructural images via convolutional neural network (CNN) models. The Si3N4 samples used for database were fabricated using various kinds of sintering additives under different process conditions. In total, 330 data sets were prepared and used for building the CNN models for artificial intelligence-bassed determination of the two mechanical properties and testing the determination accuracy of the trained models. The determination coefficients (R2), which were used as accuracy indices, were approximately 0.85 for KIC and 0.92 for σ. Although both the R2 values were relatively high, the lower value for KIC suggests that it is influenced more by what is little obtained from the microstructural information, such as grain-boundary characteristics. Furthermore, gradient-weighted class activation mapping, which can visualize which parts of the image the CNN models focus on, showed that the trained models determined the two mechanical properties based on correct recognition of the microstructural difference among the images. 相似文献
813.
Sumin Im Hyeonseok Jee Heongwon Suh Manabu Kanematsu Satoshi Morooka Koyama Taku Nishio Yuhei Akihiko Machida Jihoon Kim Sungchul Bae 《Journal of the American Ceramic Society》2021,104(9):4803-4818
This study aims to elucidate the effect of heating on the local atomic arrangements, structure, phase transformation, and mechanical properties of synthesized calcium–silicate–hydrate (C–S–H). The alteration in the atomic arrangement of the synthesized C–S–H (Ca/Si =0.8) and the formation of crystalline phases that occurred in three distinct transformation stages of dehydration (105°C–200°C), decomposition (300°C–600°C), and recrystallization (700°C–1000°C) were investigated via powder X-ray diffraction, 29Si nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. Further, the deformation of the local atomic bonding environment and variations in mechanical properties during the three stages were assessed via pair distribution function analysis based on in-situ total X-ray scattering. The results revealed that the C–S–H paste before heating exhibited a lower elastic modulus in real space than that in the reciprocal space in the initial loading stage because water molecules acted as a lubricant in the interlayer. At the dehydration stage, the strain as a function of external loading exhibited irregular deformation owing to the formation of additional pores induced by the evaporation of free moisture. At the decomposition stage, the structural deformation of the main d-spacing (d ≈ 3.0 Å) was similar to that of the real space before the propagation of microcracks. At the recrystallization stage, the elastic modulus increased to 48 GPa owing to the thermal phase transformation of C–S–H to crystalline β-wollastonite. The results provide direct experimental evidence of the microstructural and nanostructural deformation behavior of C–S–H pastes after exposure to high temperature under external loading. 相似文献
814.
815.
Manabu Tanaka 《Polymer》2007,48(20):5884-5888
The thiol group-terminated polythiophenes were prepared via the Pd-catalyzed coupling reaction of the bromo group-terminated polythiophene derivatives and methylthiophenylboronic acid, and were mixed with the nanometer-sized gold particle to form a self-assembled network film of the alternate conjugation of the polythiophene with the gold nanoparticle. The electron microscopy and X-ray photoelectron spectroscopy of the films supported the formation of a polythiophene/gold nanoparticle alternate network structure through the S-Au linkages. The high electric conductivity and its low activation energy on the network film suggested that the conductive characteristic of the film originated from that of the π-conjugated polythiophene backbone connected with the gold nanoparticle. 相似文献
816.
One of the critical problems in the operation of microchemical processes is blockage in microchannels. Therefore, a process monitoring system which can detect and diagnose blockage is indispensable for effective and stable operation of microchemical processes. In the present research, two types of diagnosis systems, a data-based blockage diagnosis system (DB-BDS) and a model-based blockage diagnosis system (MB-BDS), are proposed. To realize efficient diagnosis for various degrees of blockage, the proposed DB-BDS uses the ratios of temperature differences between normal and abnormal operating conditions at one sensor to those at the other sensor. On the other hand, MB-BDS, which uses simple physical models of the process, diagnoses blockage by calculating the correlation coefficients between the prepared temperature distribution vectors and the actual temperature distribution vector when blockage is detected. The performance of the proposed systems is evaluated with their applications to a stacked microreactor. DB-BDS and MB-BDS are applied to various types of blockage, i.e., various locations and degrees. The results show that both DB-BDS and MB-BDS can diagnose the blockage location successfully even when blockage degree is less than 10%. 相似文献
817.
Krzysztof Matyjaszewski Jerzy Chrusciel Jim Maxka Manabu Sasaki 《Journal of Inorganic and Organometallic Polymers》1995,5(3):261-279
Tetrafunctional silicon monomers have been incorporated into soluble branched polysilanes. Tetrakis(chlorodimethylsilyl)silane has been homopolymerized to form an irregular branched polymer which may contain some spiro and some bicyclic units. This polymer shows weak absorption at 300 nm, the region of the linear polysilane chains. It emits broadly in the region from 400 to 500 nm. The copolymers of tetrakis(chlorodimethylsilyl)silane with dichlorodimethylsilane are also soluble and in the presence of l ge amount of the tetrakis monomer emit in the region from 400 to 500 nm. By contrast, copolymers with phenyltrichlorosilane emit strongly at 450 to 650 nm, due to the phenylsilane hyperbranched structure. Small amounts of tetrachlorosilane can be incorporated into soluble polysilanes. Incorporation of =Si=units into polymers withn-hexyl substituents is very inefficient but leads to minor changes in emission spectra. Incorporation into polymers with phenyl substituents affects luminescence and increases molecular weights and broadens polydispersities. Reaction with dimethyldichlorosilane provides soluble low molecular weight oligomers and polymers. Polymers prepared with a small proportion of tetrachlorosilane show absorption and emission typical for linear polymers. Polymers synthesized with higher proportion of tetrachlorosilanes emit broadly at 400 to 500 nm, indicating the presence of Si clusters. The silicon clusters entrapped into soluble polymers are very easily oxidized as seen by the siloxane peaks in29Si NMR spectra and they should be treated under complete exclusion of oxygen. 相似文献
818.
Takeshi Higashi Ryoji Tsujino Kiyoshi Matsuura Yoshiaki Ueda Manabu Iguchi 《机械工程与自动化:英文版》2013,(10):595-601
In developing the new friction welding technology, the thermal elastic-plastic stress analysis by the finite element method was carried out to seek the suitable welding conditions such as the friction pressure, the friction speed and the upset pressure. The results obtained are as follows: Heat transfer to the specimens and the intermediate material during friction process was made clear; The operational conditions such as the rotation number of the intermediate material and the friction pressure to reach the liquidus in the interface could be estimated; Further, as the overhang length near the interface is well related to the joint efficiency, we tried to obtain the operational conditions by numerical analysis to acquire a certain length of the overhang length near the interface. 相似文献
819.
In order to apply thin film heads to digital video cassette recorders, wear behavior, machinability of head materials, and level difference of the heads were evaluated. The tests, performed with metal evaporated tapes, were divided into two stages. First, wear rate and machinability of individual materials were evaluated. It was found that adhesive wear was dominant for every material. Wear damage was especially-severe for metal magnetic films. Machinability was satisfactory for most bulk materials except for those with a hardness of more than 1000 kgf/mm2, ZrO2 ceramics and devitalized glass. Secondly, wear damage and level difference were evaluated using model heads. After the test, a number of flows were formed on sliding surfaces, mainly on the film surfaces, indicating that abrasive wear occurred. With bulk material of larger wear rate, the level difference reached the final value faster and its deviation was smaller. With Co-Zr-Nb magnetic metal and an Al2O3 protective layer, the level difference was less than 20 nm using CaTiO3 or ZrO2-Ta2O5, bulk substrates. 相似文献
820.
Microstructural Characterization of Porous Silicon Carbide Membrane Support With and Without Alumina Additive 总被引:1,自引:0,他引:1
Manabu Fukushima You Zhou Hiroyuki Miyazaki Yu-ichi Yoshizawa Kiyoshi Hirao Yuji Iwamoto Satoshi Yamazaki Takayuki Nagano 《Journal of the American Ceramic Society》2006,89(5):1523-1529
Porous silicon carbide (SiC) membrane supports sintered at 1500°–1800°C were prepared by cold isostatic pressing (CIP) under different pressures and using different amounts of alumina additive (0%–4%). The relationship between processing factors and pore size and microstructure was examined. Varying the sintering temperature, the CIP pressure and the amount of additive used were found to be effective for controlling pore size and microstructure. The pore size and particle size of the membrane support prepared without alumina were found to increase with increasing sintering temperature. This was attributed to surface diffusion. Densification of the undoped support did not occur, however, because of concurrent pore development. In the SiC membrane support containing 4% alumina, small particles and a pore size of around 100 nm were retained. This was because of the formation of a limited amount of SiO2 –Al2 O3 liquid phase during sintering. 相似文献