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101.
Takuya Honma Ikue Sasaki Nobuhiro Tamura Junichi Tatami Shinichiro Fujichika Katsutoshi Komeya Takeshi Meguro 《International Journal of Applied Ceramic Technology》2013,10(2):348-353
To fabricate functionally graded materials, a highly concentrated slurry of SiO2‐Mo system was prepared and centrifugal force was applied in an attempt to achieve a graded composition. Subsequently, we formed a homogeneous green body with compositional gradation by floc‐casting at 80°C, which was then fired at 1750°C for 10 min in Ar. The sintered body had compositional ratios of SiO2 and Mo as well as electrical conductivities that changed gradually along the direction of centrifugal force. The results demonstrate that centrifugation and control of slurry characteristics such as flocculation are effective in fabricating functionally graded SiO2‐Mo materials. 相似文献
102.
Biodegradable plastics were synthesized for the effective use of sago starch‐extraction residue, which has been discarded as a waste. Two types of esterified sago starch‐extraction residue, P‐SP and L‐SP, were obtained. It had black color for P‐SP160 (esterified by palm oil) to light yellow color for L‐SP80 (esterified by lauric acid) and showed high carbon content, ranging from 399.3 to 537.1 g kg−1. Biodegradable plastics from the residue, which had high esterification degree showed thermoplasticity and slower decomposition in Andisols in Japan and Inceptisols in Philippines. The esterification degrees of P‐SP160 and L‐SP were 3.23 and 2.95 to 5.18 mmol g−1, respectively. In addition, L‐SP80 exhibited the most appropriate thermal softening behavior by heating. The cumulative decomposition of P‐SP160 in Andisols and Inceptisols showed 16.7 and 32.8% of total carbon during 31 day of the incubation. On the other hand, the decomposition rates of L‐SP80 in Andisols and Inceptisols were less than 10% of total carbon during 31 day of the incubation. The addition of triacetin as plasticizer to P‐SP160 and L‐SP80 remarkably influenced the decomposition rate of both molded P‐SP160 and L‐SP80. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
103.
Mikinori Hotta Junichi Tatami Cheng Zhang Katsutoshi Komeya Takeshi Meguro Mark R. Terner Yi-Bing Cheng 《Ceramics International》2010
The formation process of hollow spheres composed of nanosized Ca-α SiAlON particles was investigated using SiO2 starting powders with different characteristics in particle size, shape and crystalline state. TEM observations showed Ca-α SiAlON hollow spheres composed of a large number of nanosized particles in the products prepared at 1450 °C for 120 min in nitrogen. In all systems, the Ca-α SiAlON hollow spheres were always produced through an intermediate Si–Al–Ca–O liquid phase in the same mechanism, regardless of the characteristics of SiO2 starting powders used. Spherical solid particles consisted of amorphous phase containing Si, Al, Ca, O and a small amount of N were generated at the initial stage of carbothermal reduction–nitridation. These spherical solid particles changed into hollow particles with the progression of the reaction from the liquid phase to the crystalline Ca-α SiAlON with increasing temperature. 相似文献
104.
The non-isothermally and isothermally crystallized stereodiblock copolymers of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with equimolar l-lactyl and d-lactyl units and different number-average molecular weights (Mn) of 3.9 × 103, 9.3 × 103, and 1.1 × 104 g mol−1, which are abbreviated as PLLA-b-PDLA copolymers, contained only stereocomplex crystallites as crystalline species, causing higher melting temperatures of the PLLA-b-PDLA copolymers compared to those of PLLA homopolymers. In the case of non-isothermal crystallization, the cold crystallization temperatures of the PLLA-b-PDLA copolymers during heating and cooling were respectively lower and higher than those of PLLA homopolymers, indicating accelerated crystallization of PLLA-b-PDLA copolymers. In the case of isothermal crystallization, in the crystallizable temperature range, the crystallinity (Xc) values of the PLLA-b-PDLA copolymers were lower than those of the PLLA homopolymers, and were susceptible to the effect of crystallization temperature in contrast to that of homopolymers. The radial growth rate of the spherulites (G) of the PLLA-b-PDLA copolymers was the highest at the middle Mn of 9.3 × 103 g mol−1. This trend is different from that of the PLLA homopolymers where the G values increased monotonically with a decrease in Mn, but seems to be caused by the upper critical Mn values of PLLA and PDLA chains as in the case of PLLA/PDLA blends (in other papers), above which homo-crystallites are formed in addition to stereocomplex crystallites. The disturbed crystallization of PLLA-b-PDLA copolymers compared to that of the PLLA/PDLA blend is attributable to the segmental connection between the PLLA and PDLA chains, which interrupted the free movement of those chains of the PLLA-b-PDLA copolymers during crystallization. The crystallite growth mechanism of the PLLA-b-PDLA copolymers was different from that of the PLLA/PDLA blend. 相似文献
105.
Ken Ando Masataka Momoda Takeshi Azumi Sadakichi Kitajima 《Journal of the American Ceramic Society》1987,70(11):309-C
Solubility of NiO in Al2 O3 was determined by electron probe microanalysisy A diffusion couple method was used by coupling an NiO-doped Al2 O3 polycrystal to a pure single crystal of Al2 O3 . The solubility of NiO in Al2 O3 in air was 230 wt ppm (157 at. ppm of cations) and 170 wt ppm (116 at. ppm) at 2073 and 1973 K, respectively. The solubility of NiO in Al2 O3 obtained in this work was compared with our previous work of the solubility of MgO in Al2 o3 . 相似文献
106.
Yoshihiko Okada Kaori Sasaki Baiqian Zhong Hideki Ishida Takeshi Mitsuda 《Journal of the American Ceramic Society》1994,77(5):1319-1323
A mixture of CaO and silicic acid prepared with a Ca/Si ratio of 2.0 was hydrothermally synthesized at 80° to 200°C, and the thermal decomposition behavior of the products (C-S-H with Ca(OH)2 ) was analyzed using XRD, 29 Si MAS NMR, and the trimethylsililation method (TMS). It was found that the main silicate anion structure of C-S-H was a mixture of a dimer and a single-chain polymer (larger than Si5 O16 ) and that polymerization advanced with an increase of the synthesizing temperature. On heating, the products decomposed to form β-C2 S. It was found that the decomposition was gradual and that the-higher the temperature of hydrothermal synthesis, the lower was the temperature of the decomposition into β-C2 S. Although the decomposition proceeded to form a monomer (β-C2 S) from the polymer and dimer, this dimer was resistant to heat and did not decompose unless heated to above 400°C. 相似文献
107.
We previously reported that a copolymer consisting of N-isopropylacrylamide (NIPAM) and benzophenone (BP) units, behaves as a photosensitizer showing temperature-controlled oxygenation activity in water (J. Am. Chem. Soc.2006, 128, 8751). This polymer shows a heat-induced oxygenation enhancement at low temperature region (5-20 °C), while showing a heat-induced oxygenation suppression at high temperature region (20-60 °C), resulting in an off-on-off activity profile against the temperature window. This is driven by a heat-induced phase transition of the polymer from coil to micelle and then to globule states. In the present work, effects of adding an amine component (N-[3-(dimethylamino)propyl]acrylamide: DMAPAM) to the polymer on the sensitization activity were studied, where the relationship between the phase transition behavior and the activity was clarified by several spectroscopic analyses. The polymers, poly(NIPAMx-co-BPy-co-DMAPAMz), show activity controlled by temperature and pH. The off-on-off activity profile shifts to higher temperature with a pH decrease. This is because protonation of the DMAPAM units leads to an increase in the polymer polarity and, hence, the polymer aggregates at higher temperature. In addition, increase in the DMAPAM content of the polymer leads to further shift of the activity profile. In contrast, at pH < 8, no activity enhancement is observed because complete protonation of the DMAPAM units suppresses polymer aggregation. 相似文献
108.
Water management in cathode gas diffusion electrode (GDE) of polymer electrolyte fuel cell (PEFC) is essential for high performance operation, because liquid water condensed in porous gas diffusion layer (GDL) and catalyst layer (CL) blocks oxygen transport to active reaction sites. In this study, the average liquid water content inside the cathode GDE of a low-temperature PEFC is experimentally and quantitatively estimated by the weight measurement, and the relationship between the water accumulation rate in the cathode GDE and the cell voltage is investigated. The liquid water behavior at the cathode is also visualized using an optical diagnostic, and the effects of operating conditions and GDL structures on the water transport in the cathode GDE are discussed. It is found that the liquid water content in the cathode GDE increases remarkably after starting the fuel cell operation due to the water production at the CL. At a high current density, the cell voltage drops suddenly after starting the operation in spite of a low water content in the cathode GDE. When the GDL thickness is increased, much water accumulates near the cathode CL and the fuel cell shuts down immediately after the operation. In the final section of this paper, the structure of cathode GDL that has several grooves for water removal is proposed to prevent water flooding and improve fuel cell performance. This groove structure is effective to promote the removal of the liquid water accumulated near the active catalyst sites. 相似文献
109.
In order to improve the solubility of C60 fullerene in conventional solvents, grafting of hydrophilic poly(ethylene oxide) (PEO) by utilizing the radical-trapping nature of C60 fullerene was investigated. Macroazo initiators containing a poly(ethylene oxide) unit, known as Azo-PEO, were prepared at various molecular weights by the reaction of 4,4′-azobis(4-cyanopentanoyl chloride) with poly(ethylene glycol) methyl ether. PEO radicals formed by thermal decomposition of Azo-PEO were successfully trapped by C60 fullerene to give PEO-grafted C60 fullerene. Their structures were confirmed by FT-IR spectroscopy, size exclusion chromatography, UV-vis spectroscopy, and differential scanning calorimetry. When Azo-PEO with low-molecular weight was reacted with C60 fullerene, a bis-adduct, C60-(PEO)2, and a tetrakis-adduct, C60-(PEO)4, were formed. In contrast, in reactions with Azo-PEO of higher molecular weight, only the bis-adduct was formed, and no formation of the tetrakis-adduct was observed. The structure of bis-adduct was found to be 1,4-type. The solubility of C60 fullerene in water, THF, methanol, and other conventional organic solvents was remarkably improved by grafting of PEO. In addition, the thermal stability of PEO was dramatically increased by grafting onto C60 fullerene. 相似文献
110.
Summary: Silk fibroin cast film was prepared using a ternary solvent system of CaCl2/CH3CH2OH/H2O (1/2/8 in mole ratio). A drying temperature at casting influenced crystal structure of fibroin. When a drying temperature was set lower than 9 °C, the cast film became amorphous. When a drying temperature was set higher than 40 °C, a fibroin film of silk‐II structure was obtained. In order to produce a fibroin film of silk‐I structure, a preferable temperature range was from 20 to 26 °C. The crystal transformation from random coil structure into silk‐I could be made through exposure of an amorphous film to water vapor. As for the crystal transformation from silk‐I into silk‐II, the treatment with a glycerin solution was effective. In the course of the treatment a film showed self‐thinning and self‐expanding. The expansion ratio exceeded 40% at maximum. The film produced accompanying self‐expansion was ductile in nature.