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61.
Marine antifouling coating using functional polymers has emerged as an important tool to combat marine fouling. Owing to their natural abundance, polysaccharides represent a more sustainable option than synthetic polymers and carrageenan, a sulfated polysaccharide, is identified as a promising candidate for further research based on its excellent marine antifouling properties. However, existing research has only explored the application of carrageenan-based coatings for 2D objects, using techniques such as spin-coating. Here, a spray-coating method is proposed to apply carrageenan-based coatings to the surfaces of 2- and 3-D objects. The coated surfaces exhibit high stability under various chemical/physical stresses and high resistance to protein adsorption and marine diatom adhesion. 相似文献
62.
Koo Hyun Lee Ki Suk Nam Youl Min Park Pyung Woo Shin Deuk Yong Lee Yo-Seung Song 《Metals and Materials International》2002,8(4):381-385
Plasma nitrocarburized AISI 1020 steels were oxidized for 15, 30 and 60 min to evaluate their corrosion and microstructural properties. After plasma nitrocarburizing for 3 h at 570°C in a gas mixture comprising 85 vol.% N2, 12vol.% H2 and 3 vol.% CH4, the compound layer composed of ɛ-Fe2–3(N,C) and γ’-Fe4(N,C) phases and the diffusion layer above the matrix were observed. The top oxide layer, consisting mainly of magnetite (Fe2O4) and hematite (Fe2O3) phases, forms after post-oxidation treatment at 500°C. However, the oxide layer was severely degraded by spallation as a result of increases in post-oxidizing time. The difference in corrosion resistance should be attributed to the thickness of the top oxide layer, which was governed by post-oxidizing time. 相似文献
63.
Irina Tsarenko Sang Park Honghua Du Woo Y. Lee 《Journal of the American Ceramic Society》2003,86(9):1622-1624
A 25 nm thick α-alumina layer was deposited on a turbine-grade silicon nitride by sol-gel dip coating and subsequent heat treatment in air at 1200°C. This layer had a nanometer grain structure. Silicon nitride protected by this thin layer showed a significant improvement in oxidation resistance over its uncoated counterpart after 200 cyclic exposures in air at 1250°C. The oxide layer grown on the coated silicon nitride also exhibited superior surface morphology, compared with the uncoated silicon nitride. 相似文献
64.
Copoly(amide-ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt-spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo-betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide-ether) was melt-spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on-line with spinning and drawing within a short reaction time, this modification technique is called “spin-finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity. 相似文献
65.
High‐density polyethylene (HDPE) beads were successfully surface‐crosslinked in a modified plasma reactor. The modified plasma reactor treats large amounts of beads, which are uniformly surface‐crosslinked. In this study, effects of the gas pressure, radio‐frequency (RF) power, and the treatment time on the degree of surface crosslinking were systematically investigated. Degree of surface crosslinking was measured by solvent extraction method (boiling xylene method, BXM). The gel content of plasma‐treated HDPE increases from 0.0 to 1.05% within 10 min at 100 mTorr, 200 W. FTIR and DSC analyses show that the crosslinked layer after plasma treatment is limited only at HDPE surface without changing the bulk thermal property of HDPE. Through the analysis of FTIR, it was confirmed that main peaks corresponding to CH2 bands were decreased and two peaks corresponding to CF2 and CF3 were observed after plasma surface modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2921–2929, 2002; DOI 10.1002/app.10295 相似文献
66.
Summary The surface modification of low-density polyethylene(PE) by liquid phase photograft polymerization with acrylic acid(AA), acrylamide(AM) and glycidyl methacrylate(GMA) was described. The grafting of AA and AM was proved and characterized by electron spectroscopy for chemical analysis(ESCA). It was found that fully hydrophilic surface can be obtained in very short irradiation time. With ESCA and attenuated total reflection infrared spectroscopy(ATR-IR), it can be confirmed that bifunctional monomer GMA was grafted onto the PE film surface. Through further reaction with GMA grafted film, heparin and protamine were immobilized onto the grafted film surface. 相似文献
67.
Jin-Kwang Bok Heeman Lee Jay Woo Chang Sunwon Park 《Korean Journal of Chemical Engineering》2002,19(4):545-551
This paper presents a hybrid refinery scheduling system combining mathematical programming model and expert system. Mixed-integer
linear programming models for crude oil movement between units are merged into the expert system that is for qualitative issues
concerning crude vessel unloading operations. The target problem ranging from the crude unloading to the crude charging to
distillation towers is decomposed into several module problems for efficiency. Compared with existing scheduling approaches
for oil movement, the proposed hybrid refinery scheduling system is very effective in dealing with timing decisions involving
vessel unloading operations due to the advantages of an expert system. Since the proposed scheduling system can generate solutions
so fast, it is expected to play a key role in the real processes.
This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University. 相似文献
68.
Pd catalysts supported on TiO2, ZrO2, ZSM-5, MCM-41 and activated carbon were used in catalytic wet oxidation of hydrocarbons such as phenol, m-cresol and m-xylene.
It was found that the Pd/TiO2 catalyst was highly effective in the wet oxidation of hydrocarbon. The activities of catalysts with various hydrocarbon species,
catalyst support, oxidation state of catalyst performed in a 3-phase slurry reactor show that reaction on Pd surface is more
favorable than that in aqueous phase and that the active site is oxidized Pd in catalytic wet air oxidation of hydrocarbons.
Based on the experimental results, a plausible reaction mechanism of wet oxidation of hydrocarbons catalyzed over Pd/TiO2 catalyst was proposed. This catalyst is superior to other oxide catalysts because it suppressed the formation of hardly-degradable
organic intermediates and polymer. 相似文献
69.
Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY- and HY-zeolite were examined as a catalyst for producing gasoline
from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged
Y-zeolite with O2 and H2 at 300°C., respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed
desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to
Pt/NaY monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C5–C7 and skeletal isomers of C5–C7- and C8–C10 than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline
these days. However, deactivation with reaction time was much more pronounced on HY-zeolite-supported catalyst. When the catalyst
was prcsulfided with H,S, the stability with time on stream was enhanced and the selectivity was quite different from that
of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activny,
selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction. 相似文献
70.
Hyoung Jin Choi Yong Woo Inn Myung S. Jhon 《Korean Journal of Chemical Engineering》1994,11(3):145-152
Polymer migration is a generally well-known phenomenon in a flow field, and it has been verified that the sources of such
phenomena are nonhomogeneity of the flow, concentration effects and hydrodynamic interactions between the polymer molecules.
In addition, temperature effects were found to be another source of polymer migration. The Langevin equation for a polymer
molecule was first derived from single chain dynamics using a kinetic theory for the bead-spring elastic harmonic dumbbell
model, as described in part I (reference [1]). In this paper the diffusion equation and concentration profile of the polymer
molecules induced by a temperature gradient are obtained from the Fokker-Planck equation. A new differential operator is also
introduced to calculate the concentration profile. From the concentration equation obtained in the general flow geometry,
we find that in dilute polymer solution there are significant effects on the polymer migration not only due to the nonhomogeneity
of the flow field but also due to temperature gradients. 相似文献