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71.
Biodegradability and mechanical properties of agro‐flour–filled polybutylene succinate biocomposites
The objective of this study was the production of rice husk flour (RHF) and wood flour (WF) filled polybutylene succinate (PBS) biocomposites as alternatives to cellulosic material filled conventional plastic (polyolefins) composites. PBS is one of the biodegradable polymers, made from the condensation reaction of 1,4‐butanediol and succinic acid that can be naturally degraded in the natural environment. We compared the mechanical properties between conventional plastics and agro‐flour–filled PBS biocomposites. We evaluated the biodegradability and mechanical properties of agro‐flour–filled PBS biocomposites according to the content and filler particle size of agro‐flour. As the agro‐flour loading was increased, the tensile and impact strength of the biocomposites decreased. As the filler particle size decreased, the tensile strength of the biocomposites increased but the impact strength decreased. The addition of agro‐flour to PBS produced a more rapid decrease in the tensile strength, notched Izod impact strength, and percentage weight loss of the biocomposites during the natural soil burial test. These results support the application of biocomposites as environmentally friendly materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1513–1521, 2005 相似文献
72.
β-SiC powder containing 6 wt% A12 O3 and 4 wt% Y2 O3 as sintering additives was pressureless sintered at 2000°C for 1 h (AYE-SiC) and 3 h (AYP-SiC). AYE-SiC consisted of an equiaxed grain structure and AYP-SiC exhibited a micro-structure with platelike grains as a result of grain growth related to β→α phase transformation during sintering, R -curve behavior and flaw tolerance for these silicon carbides were evaluated by the indentation-strength technique. For comparison, the R -curve behavior of conventional sintered, boron- and carbon-doped SiC (SS-SiC) was evaluated. AYE-SiC and AYP-SiC exhibited rising R -curve behavior with toughening exponents of m = 0.042 and m = 0.135, respectively. AYP-SiC exhibited better flaw tolerance and more sharply rising R -curve behavior than AYE-SiC. The more sharply rising R -curve behavior and the better flaw tolerance of AYP-SiC were attributed mainly to grain bridging of crack faces by platelike grains. Because of the high degree of transgranular fracture, SS-SiC exhibited a flat R -curve despite a microstructural feature with platelike grains. 相似文献
73.
Solid circulation characteristics in an internally circulating fluidized bed with orifice-type draft tube 总被引:1,自引:0,他引:1
Sang Done Kim Yo Han Kim Seon Ah Roh Dong Hyun Lee 《Korean Journal of Chemical Engineering》2002,19(5):911-916
Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate
(G,) have been determined in an internally circulating fluidized bed (0.28 m I.D. × 2m high) with an orifice type draft tube.
The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft
tube(U
d
) and annulus section (Ua) and consequent increase in pressure drop across the orifice (ΔPor). However, the values ofG
s
decrease by 7–21% with increasing particle size from 86 to 288 μm. The pressure drop across the orifice increases with increasingU
d
andU
a
. However, ΔPor decreases by 5–23% with increasing particle size. To predictG
s
in an internally circulating fluidized bed, a correlation is proposed as a function of ΔPor
This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement Korea University. 相似文献
74.
Jong-Ho Ryu Jong Hyun Seo Jae-Han Jeong Sung-Kap Kim Dong Nyung Lee 《Journal of Applied Electrochemistry》2004,34(9):879-884
A study has been made of the electrochemical etching of 99.99% aluminum foils at a current density of 50 mA cm–2in AlCl3–HCl solutions (1 m Cl–) at 80 °C. The solutions were made by dissolving metallic aluminum into 1m HCl solution, to give a Cl– concentration of 1 m. The number density of etch tunnels and the homogeneity of tunnel length decreased, and the mean pit size and its standard deviation increased with increasing Al3+ concentration. The results were discussed based on potential transients at a current density of 50 mA cm–2, current–potential curves at a scan rate of 10 m Vs–1 and electrochemical impedance spectra. 相似文献
75.
Won Seok Lyoo Han Do Ghim Hee‐Sam Kim Joon Ho Kim Sam Soo Kim Won Sik Yoon Jinwon Lee Sang‐Seob Lee 《应用聚合物科学杂志》2002,86(14):3667-3672
N‐Vinylcarbazole (VCZ) was solution‐polymerized in tetrahydrofuran (THF) at ?20, 0, and 20°C using the photoinitiation method; the effects of the amount of solvent, polymerization temperature, and photoinitiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Low polymerization temperature using photoinitiation proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of a high molecular weight with a smaller temperature rise during polymerization; nevertheless of free radical polymerization by 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The photo‐solution polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at ?20°C using a photoinitiator concentration of 0.00005 mol/mol of VCZ, a weight‐average molecular weight of 510,000 was obtained, with a polydispersity index of 1.73, and a degree of lightness converged to about 99%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3667–3672, 2002 相似文献
76.
All experiments of pressure fluctuations were carried out in a bubble column with a moderately large column of 0.376 m ID.
The recently developed technique of wavelet packet transform based on localized wavelet functions is applicable to analysis
of the fluctuating signals. The time series of pressure fluctuation signals have been analyzed by means of wavelet packet
transform components, decomposition through best basis algorithm and timefrequency representation. By resorting to this technique,
the objects in bubbly flow regime have fine scales and frequencies than ones in churn-turbulent flow regime. Thus, this wavelet
packet transform method enables us to obtain the frequency content of local complex flow behaviors in a bubble column. 相似文献
77.
We prepared poly(p‐phenylene pyromellitimide) (PMDA–PDA), poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10?10 to 11.3 × 10?10 cm2/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in‐plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003 相似文献
78.
Jeung Hee Lee Kerby C. Jones Thomas A. Foglia Alberto Nuñez Jong Ho Lee Yu Mi Kim Phuong-Lan Vu Ki-Teak Lee 《Journal of the American Oil Chemists' Society》2007,84(3):211-217
Using a 1,3-regioselective lipase as a catalyst, soybean oil and olive oil were interesterified with the short-chain triacylglycerol
tributyrin (1,2,3-tributyrylglycerol) to produce mixtures of structured triacylglycerols (SL-TAG). The SL-TAG were purified
by column chromatography and analyzed by both normal-phase (silica column; NPSIL) and reversed-phase [octadecyl silane (ODS) column] high-performance liquid chromatography (HPLC). Individual SL-TAG molecular
species were detected by evaporative light-scattering detection, and characterized by mass spectrometry. NPSIL HPLC successfully separated the newly synthesized SL-TAG into two groups of TAG: one composed of one butyryl group and two
long-chain fatty acyl groups (from soybean or olive oil); the second was composed of two butyryl groups and one long-chain
fatty acyl group. The SL-TAG species were further analyzed by reversed-phase HPLC which gave a more detailed separation of
the TAG species present in the two SL-TAG. 相似文献
79.
Yongwon Seo Sung-Ho Jo Ho-Jung Ryu Hee Dal Bae Chong Kul Ryu Chang-Keun Yi 《Korean Journal of Chemical Engineering》2007,24(3):457-460
A bubbling fluidized bed reactor was used to study CO2 capture from flue gas by using a potassium-based solid sorbent, sorbKX35 which was manufactured by the Korea Electric Power
Research Institute. A dry sorbent, sorbKX35, consists of K2CO3 for absorption and supporters for mechanical strength. To increase initial CO2 removal, some amount of H2O was absorbed in the sorbent before injecting simulated flue gas. It was possible to achieve 100% CO2 removal for more than 10 minutes at 60°C and a residence time of 2 s with H2O pretreatment. When H2O pretreatment time was long enough to convert K2CO3 of sorbKX35 into K2CO3 · 1.5H2O, CO2 removal was excellent. The results obtained in this study can be used as basic data for designing and operating a large scale
CO2 capture process with two fluidized bed reactors.
This work was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
80.
Jae Ryong Kim Do-Hyeong Kim Chong Hee Kim 《Journal of the American Ceramic Society》1990,73(8):2567-2569
The effects of ZrO2 and Y2 O3 on the densification of hotpressed Si3 N4 -Zr(Y)O2 composites have been studied. High density could not be obtained by the addition of pure or 3-mol%-Y2 O3 -doped ZrO2 in this composite; however, nearly full density (>97%) could be obtained in Si3 N4 using 6- and 8-mol%-Y2 O3 -doped ZrO2 . It is concluded that Y2 O3 diffusing out from the added Zr(Y)O2 promoted the densification and that ZrO2 also had some role in the formation of an oxynitride glass. 相似文献