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1.
We propose a dynamic model for the copolymerization of α‐methyl styrene (α‐MS) and methyl methacrylate (MMA) in a batch reactor. The parameters are based on data from the literature and our own laboratories over the full conversion range. A two‐parameter model with constant reactivity ratios shows the most reasonable results. The dynamic model depicts the reaction kinetics and reactor behavior more clearly. Termination occurs mainly by the cross reaction of unlike radicals, and its rate increases with the molar ratio of α‐MS to MMA. The model enables us to predict the instantaneous and cumulative properties of the copolymer and also provides us with a basic tool for the optimization and control of industrial reactors. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 261–270, 2004 相似文献
2.
Nd-doped bismuth titanate Bi4 − x
Nd
x
Ti3O12 ceramics (x = 0–1.0) were prepared by the solid state reaction method. The temperature dependence of the dielectric dispersion and ferroelectric
properties were investigated. With the increase of the Nd substitution for Bi ion, the Curie temperature decreased and the
corresponding dielectric constant peak broadened. In addition, the strong low-frequency dielectric dispersions were exhibited.
The Nd doping decreases the temperature dependence of the ac conductivity and increases the temperature dependence of the
remanent polarization, which is caused by the induced polarization by defects, such as bismuth and oxygen vacancies. 相似文献
3.
Chang Won Ahn Hee Sung Kim Won Seok Woo Sung Sik Won Hae Jin Seog Song A Chae Bong Chan Park Ki Bong Jang Yun Po Ok Hyon Ho Chong Ill Won Kim 《Journal of the American Ceramic Society》2015,98(6):1877-1883
We investigated the influence of CuO amount (0.5–3.0 mol%), sintering temperature (900°C–1000°C), and sintering time (2–6 h) on the low‐temperature sintering behavior of CuO‐added Bi0.5(Na0.78K0.22)0.5TiO3 (BNKT22) ceramics. Normalized strain (Smax/Emax), piezoelectric coefficient (d33), and remanent polarization (Pr) of 1.0 mol% CuO‐added BNKT22 ceramics sintered at 950°C for 4 h was 280 pm/V, 180 pC/N, and 28 μC/cm2, respectively. These values are similar to those of pure BNKT22 ceramics sintered at 1150°C. In addition, we investigated the performance of multilayer ceramic actuators made from CuO‐added BNKT22 in acoustic sound speaker devices. A prototype sound speaker device showed similar output sound pressure levels as a Pb(Zr,Ti)O3‐based device in the frequency range 0.66–20 kHz. This result highlights the feasibility of using low‐cost multilayer ceramic devices made of lead‐free BNKT‐based piezoelectric materials in sound speaker devices. 相似文献
4.
Ill Yong Kim Ryota Iwatsuki Koichi Kikuta Yumi Morita Toshiki Miyazaki Chikara Ohtsuki 《Materials science & engineering. C, Materials for biological applications》2011,31(7):1472-1476
Osteoconductive materials with self-setting ability have received much attention because their properties allow developing injectable materials for bone defects. Thermosensitive hydrogel with ability of bone-like apatite formation in a body environment is a candidate of injectable bone fillers with osteoconductivity because the apatite formation on materials is an essential to show osteoconduction. The present study focused on the development of a thermosensitive hydrogel through modifications of the sulphonic groups of the polysaccharide, κ-carrageenan, with potassium chloride (KCl) and calcium chloride (CaCl2). We found that the gelation temperature of κ-carrageenan solutions increased with increasing amounts of K+ ions. Apatite formation was observed on the gel after exposure to simulated body fluid for 0.5 day when the gel was prepared with a molar ratio of Ca2+/sulfonic groups = 1.5. These results indicate that a thermosensitive κ-carrageenan hydrogel with apatite-forming ability was obtained through the incorporation of K+ and Ca2+ ions into the solution. 相似文献
5.
F. E. López-Suárez A. Bueno-López M. J. Illán-Gómez B. Ura J. Trawczynski 《Topics in Catalysis》2009,52(13-20):2097-2100
The activity for soot combustion in NO x /O2 and stability, under reaction conditions, of two potassium-perovskite catalysts (K/SrTiO3 and Sr0.8K0.2TiO3) and a potassium-copper perovskite catalyst (K–Cu/SrTiO3) has been studied. In fresh catalysts, potassium is more active than copper. However copper is stable under reaction conditions while potassium-catalysts are progressively deactivated due to the loss of this metal during consecutive TPR cycles. 相似文献
6.
Regulated Breathing Effect of Silicon Negative Electrode for Dramatically Enhanced Performance of Li‐Ion Battery
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Xingcheng Xiao Weidong Zhou Youngnam Kim Ill Ryu Meng Gu Chongmin Wang Gao Liu Zhongyi Liu Huajian Gao 《Advanced functional materials》2015,25(9):1426-1433
Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (≈3600 mAh g–1). However, the huge volume swelling and shrinking during cycling, which mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic efficiency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well‐developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response at electrode level. For the first time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle efficiency. In situ transmission electron microscopy and finite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion. 相似文献
7.
8.
Byung?Moon?JinEmail author Ill?Won?Kim Jin?Soo?Kim Dae?Su?Lee Chang?Won?Ahn Jeong?Ho?Kwon Jae?Shin?Lee Jae?Sung?Song Soon?Jong?Jeong 《Journal of Electroceramics》2005,14(2):119-122
The dielectric and piezoelectric properties of 0.2Pb(Mg1/3Nb2/3)O3-0.8Pb(Zr0.475Ti0.525)O3 (abbr. as PMNZT) ceramics were measured. Extremely low sintering temperatures of 950∘C using liquid-phase sintering aid of Li2O is achieved which was very useful for multi-layered applications. X-ray study shows the splitting of rhombohedral (200) in pure PMNZT to (002) and (200) peaks in Li2O doped samples. 10 times higher dielectric constant was achieved in Li2O doped samples to compare to pure ones although the Curie temperature (Tc = 322∘C) of Li2O doped PMNZT ceramics was not changed. The value of kp and k33 increased up to 0.1 wt% of Li2O and saturating thereafter. 相似文献
9.
10.
Mun-Seok Choi Sung-Hoon Kim Young-Hyeok Kim Ill Won Kim Soon-Jong Jeong Jae-Sung Song Jae-Shin Lee 《Journal of Electroceramics》2008,20(3-4):225-229
Ag–ceramic composite materials were investigated as low-cost internal electrodes for low firing piezoelectric multilayer ceramic
actuators (MLCA). Ag–ceramic pastes were prepared by adding Pb(Mg1/3Nb2/3)O3–Pb(Zr0.475,Ti0.525)O3 (PMNZT) ceramic powders to a commercial Ag paste in the range of 0 to 50 wt.%. PMNZT/Ag–PMNZT multilayered laminates were
fabricated using tape casting and subsequently cofired at 925°C for 10 h. The addition of PMNZT into Ag electrode decreased
the thermal shrinkage mismatch between the composite layers, which led to improve mass producibility of MLCA through reducing
delamination probability during cofiring process. 相似文献