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51.
Interfacial tension between demixed solutions of polystyrene + methylcyclohexane has been measured near the critical temperature as a function of temperature using polystyrenes with molecular weights 9000 ~ 1.26 × 106. The critical exponent for the interfacial tension was determined to be about 1.30 for the lower molecular weight systems. However, for higher molecular weights the exponent could not be obtained because the system departed from critical behaviour. Magnitudes of the interfacial tension were proportional to about N?0.44, where N is the polymerization index. Experimental results were compared with the recently-proposed theories and found to be in qualitative agreement. The tricritical theory of polymer solutions was also compared with the experimental results. 相似文献
52.
Dielectric and piezoelectric properties of 0.02Pb(Y2/3 W1/3 )O3 0.98Pb(Zr0.52Ti0.48)O3 ceramics doped with additives (Nb2 O5 , La2 O3 , MnO2 , and Fe2 O3 ) were investigated. The grain sizes of these ceramics decreased with increasing amounts of additives. For additions of MnO2 and Fe2 O3 , dielectric losses decreased, while for Nb2 O5 and La2 O3 , these values increased. The maximum values of the mechanical quality factor Qm were found to be 956 and 975 for additions of 0.9 wt% Fe2 O3 and 0.7 wt% MnO2 , respectively, but donor dopants (Nb2 O5 and La2 O3 ) did not change the values of Qm . On the other hand, the piezoelectric constant d33 and the electromechanical coupling factor kp decreased with additions of MnO2 and Fe2 O3 , but improved with additions of Nb2 O5 and La2 O3 . 相似文献
53.
Masahiro Kato Kazuaki Nakagawa Kenji Essaki Yukishige Maezawa Shin Takeda Ryosuke Kogo Yoshikazu Hagiwara 《International Journal of Applied Ceramic Technology》2005,2(6):467-475
We have discovered a series of lithium-containing oxides that immediately react with ambient carbon dioxide (CO2 ) up to 700°C. The products react and return reversibly to the oxides at a temperatures higher than about 700°C. The absorption capacity surpasses that of other CO2 absorbents by a factor of 10. Utilizing these absorbents, the possibility of a CO2 separation system that operates at around 500°C is proposed. It is generally believed that a CO2 separation process operable at temperatures higher than 500°C has the special benefit of a small energy penalty. Moreover, the absorption also proceeds at ambient temperature in the atmospheric environment. This property offers the possibility of many other applications, such as air cleaners or cartridges. Therefore, we think these materials have the potential to make a valuable contribution to the realization of CO2 emission control. 相似文献
54.
Poly(L ‐lactic acid) (PLLA: Mw = 19.4 × 104)/poly(ethylene glycol) (PEG: Mw = 400) blend films were formed by use of a solvent‐cast technique. The properties and structures of these blend films were investigated. The Young's modulus of the PLLA decreased from 1220 to 417 MPa with the addition of PEG 5 wt %, but the elongation at break increased from 19 to 126%. The melting point of PLLA linearly decreased with increases in the PEG content (i.e., pure PLLA: 172.5°C, PLLA/PEG = 60/40 wt %: 159.6°C). The PEG 20 wt % blend film had a porous structure. The pore diameter was 3–5 μm. The alkali hydrolysis rate of this blend film was accelerated due to its porous structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 965–970, 2004 相似文献
55.
Keiichi Tomishige Shogo Kanazawa Motoki Sato Kenji Ikushima Kimio Kunimori 《Catalysis Letters》2002,84(1-2):69-74
Pt(0.3)/Ni(10)/Al2O3, prepared by a sequential impregnation method, exhibited a more excellent performance in methane reforming with CO2 and O2 in terms of the catalytic activity and the temperature profile of the catalyst bed than Pt(0.3) + Ni(10)/Al2O3 prepared by a coimpregnation method, Ni(10)/Al2O3, Pt(0.3)/Al2O3, and Pt(10)/Al2O3. It is thought that this is because the surface Pt atoms on Ni catalyst can contribute to the enhancement of the catalyst reducibility. 相似文献
56.
Yumi Fukuda Koichi Harada Maki Yonetsu Ariane K. Albessard Yasushi Hattori Kenji Essaki Yasuhiro Goto Tomohiro Suetsuna 《Journal of the American Ceramic Society》2021,104(12):6563-6571
When reaction-bonded silicon nitride containing MgO/Y2O3 additives is sintered at three different temperatures to form sintered reaction-bonded silicon nitride (SRBSN), the thermal conductivity increases with sintering temperature. The β-Si3N4 (silicon nitride) crystals of SRBSN ceramics were synthesized and characterized to investigate the relation between the crystal structure and the lattice oxygen content. The hot-gas extraction measurement result and the crystal structure obtained using Rietveld analysis suggested that the unit cell size of the β-Si3N4 crystal increases with the decrease in the lattice oxygen content. This result is reasonable considering that the lattice oxygen with the smaller covalent radius substitutes nitrogen with the larger one in the β-Si3N4 crystals. The lattice oxygen content decreased with increasing sintering temperature which also correlated with increase in thermal conductivity. Moreover, it is noteworthy from the viewpoint that it may be possible to apply the lattice constant analysis for the nondestructive and simple measurement of the lattice oxygen content that deteriorates the thermal conductivity of the β-Si3N4 ceramics. 相似文献
57.
Lingyun Lyu Takeshi Hanada Naohiro Yamahira Jun Morita Ryota Yamamoto Ken Itomi Takumi Adachi Sho Kubouchi Shin Horiuchi 《应用聚合物科学杂志》2021,138(45):51443
The distribution of nano-sized silica in binary rubber blends is characterized by scanning transmission electron microscopy (STEM) tomography combined with energy dispersive X-ray spectrometry (EDX). 3D distribution of silica is visualized by STEM-EDX tomography with the tilt-series of silicon elemental maps, while the phase-separated morphologies of polyisoprene rubber (IR) and styrene-butadiene rubber (SBR) are visualized by STEM-tomography in high-angle-annular-dark field (HAADF) mode. The combination of STEM-EDX and STEM-HAADF tomography enables us to determine the distribution of silica between the two rubber phases quantitatively even with high contents of silica up to 70 phr (weight parts per hundred rubber). It is found that silica is preferentially distributed in the SBR phase, but it is also distributed in the IR phase when the IR fraction in the total rubber components is higher than 40 wt%. The preferential distribution of silica in the SBR phase improves the dispersion of the IR domains. This is the first use of this technique for a multicomponent polymer system, showing the advantage to characterize the complicated multicomponent polymer composite morphologies. 相似文献
58.
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
59.
Amorphous Al50Ta60 alloy powders have been synthesized by mechanical alloying (MA) from elemental powders of aluminium and tantalum, and mechanical disordering (MD) from crystalline intermetallic compound powders of AlTa respectively using the rod milling technique. The mechanically alloyed and the mechanically disordered alloy powders were characterized by X-ray diffraction, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, differential thermal analysis, differential scanning calorimetry and chemical analysis. The results have shown that the crystal-to amorphous transformation in the MD process occurs through one stage, while the crystallineto-amorphous formation in the MA process occurs through three stages. At the early and intermediate stages of the MA time, heating the alloy powders to 700 K leads to the formation of an amorphous phase by a solid-state amorphizing reaction. At the final stage of the MA time, the amorphous phase is crystallized through a single sharp exothermic peak. Contrary to this, amorphous alloy powders produced by MD are crystallized through two broad exothermic peaks. 相似文献
60.
Time Averaging Algorithms with Stopping Rules for Multi‐Agent Consensus with Noisy Measurements 下载免费PDF全文
A time averaging technique is introduced to consensus algorithms in networked multi‐agent systems under a noisy environment. Each agent communicates with its neighboring agents via a constant gain, while the time averaging states of the agents are considered as the values for agreement. The variation of the time averaging states then is evaluated at a specific number of iterations, where the number is given explicitly in terms of parameters related to the consensus accuracy and its probabilistic guarantee. This result establishes a rigorous stopping rule for the multi‐agent consensus with noisy measurements. Several results on this type of stopping rules are provided for undirected, directed, and time‐varying communication graphs. These theoretical results are illustrated through numerical examples. 相似文献