• 제목/요약/키워드: Hydrophobicity

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Effect of surface modifiers on the nano porous silica aerogels prepared by ambient drying process (상압건조 나노다공성 실리카 에어로젤에 대한 개질제 효과)

  • Kim, Tae-Jung;Oh, Young-Jei
    • Journal of Sensor Science and Technology
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    • v.16 no.1
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    • pp.77-83
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    • 2007
  • Nanoporous silica aerogels with various surface modifiers were prepared by ambient drying process. Tetraethylorthosilicate (TEOS) were used a raw material. Ambient drying process for various surface modifier was studied in the point of view of a crack-free monolith and thin films and low cost. Various kinds of surface modifiers like as hexamethyldisilazane (HMDSZ), trimethlychlorosilane (TMCS), methlytriethoxylsilane (MTES), and methlytrimethoxysilane (MTMS) were studied in order to enhance hydrophobicity for the silica aerogel. Surface modified aerogels were evaluated by FT-IR, TG, BET, SEM and wetting angle measurement. Homogeneous and crack-free aerogels were obtained by modifying the HMDSZ and the TMCS. However silica xerogel was obtained when modified with MTMS, MTES.

유류분해 미생물의 특성 및 제제화 가능성 평가

  • 윤정기;김태승;노회정;김혁;박종겸;고성환
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2004.04a
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    • pp.297-300
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    • 2004
  • The various microbial tests were performed to determine bioremediation agent capacity for eight strains isolated from the oil contaminated regions. Two tests for isolated strains were conducted such as cell hydrophobicity and emulsifying activity. The biodegradation of SHM (saturated hydrocarbon mixture) and AHM (aromatic hydrocarbon mixture) with the strains also was carried out. The strains having higher cell hydrophobicity and emulsifying activity degraded petroleum oil effectively. The degradation capacity for SHM was represented more than 90% in YS-7 and WLH-1 of isolated strains, and KH3-2 were capable of degrading AHM. Especially, WLH-1 as yeast was shown more than two or three times in the degradation capacity of automobile engine lubricants and the biomonitoring results of contaminated soil for residual oil degrading test showed that the hydrocarbon biodegradation was increased in the second treatment by this strain.

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Surface Chemical Studies on Flotation Processes -Importance of the Hydrophobic Property of Solid Particles in Flotation Efficiency- (부유부상 공정에 대한 표면화학적 연구 -부유부상 효율과 고형입자의 소수화도-)

  • 이학래;이진희;허용성;조중연;한신호
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.33 no.1
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    • pp.1-7
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    • 2001
  • The immediate purposes of this study is to establish the surface chemical principles associated with the flotation process of waste papers and to verify them by practical flotation experiments. To achieve this AKD sized hydrophobic microcrystallince cellulose (MCC) with different levels of hydrophobicity, and hydrophilic MCC dyed with black were prepared as model substances. The effects of surface characteristics on flotation efficiency were evaluated by measuing the brightness of the flotation rejects obtained after the flotation experiments carried out using MCC mixtures prepared with different ratios of hydrophobic and hydrophilic MCCs. Results showed that more than 90% of the flotation rejects consisted of hydrophobic MCC indicating the critical importance of the hydrophobicity of the materials in the flotation process. The proportions of hydrophobic materials in the reject remained constant when highly sized MCC was used as a model of hydrophobic substance.

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Physiological Responses of Bacillus amyloliquefaciens Spores to High Pressure

  • Ahn, Ju-Hee;Balasubramaniam, V.M.
    • Journal of Microbiology and Biotechnology
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    • v.17 no.3
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    • pp.524-529
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    • 2007
  • Pressure inactivation behavior of Bacillus amyloliquefaciens spores was investigated in deionized water. The spores of B. amyloliquefaciens were subjected to $105^{\circ}C$ and 700 MPa. The magnitude of the decrease in viability after pressure treatment was similar to that after pressure treatment followed by heat shock. The increase of dipicolinic acid (DPA) release was correlated with the spore inactivation, and the hydrophobicity did not significantly change during the pressure-assisted thermal processing (PATP). Lag phase duration increased with increasing pressure process time. The mechanisms of spore germination and inactivation during the PATP were related to a complex physiological process.

The Effect of Methylated Cyclodextrins on the Morphological Change of Poly(3-hydroxybutyrate) with and without the Formation of Inclusion Complex

  • Shin, Kyung-Moo;Dong, Tungalag;Inoue, Yoshio
    • Proceedings of the Polymer Society of Korea Conference
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    • 2006.10a
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    • pp.351-351
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    • 2006
  • The possible interactions between cyclodextrins and biodegradable polyesters were investigated. The hydrophobicity of cyclodextrin could be varied with the methyl substitution of host CD, and the possibility of IC formation and the types of interaction between respective CDs and polyesters were subsequently changed. Further, the effect of cyclodextrins on the morphological change of biodegradable polymer was shown to depend on the degree of IC formation between cyclodextrin and biodegradable polymer as well as on the type of interaction between respective CDs and polyesters. That is, the enhancement and/or the restriction of the crystallization of P(3HB) were observed by the incorporation of various kind of cyclodextrins with different cavity size and hydrophobicity.

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Surface Modification of Silica Aerogels (실리카 에어로겔의 표면 개질)

  • 현상훈;이찬호;김동준
    • Journal of the Korean Ceramic Society
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    • v.33 no.12
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    • pp.1319-1324
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    • 1996
  • Silica aerogels were synthesis by the sol-gel-supercritical drying process using isopropanol as a solvent. Effets of the heat-treatment and the surface modification through propoxylation on the structural reinforcement as well as the surface hydrophobic/hydrophilic characteristics of aerogels were investigated. Silica aerogels synthesized by supercritical drying were hydrophobic but aerogels heat-treated above 20$0^{\circ}C$ were transformed to be hydrophilic. In particular it was found that the skeletal structure of aerogels heat-treated at 50$0^{\circ}C$ was strong enough not to crack after adsorbing a large amount of water vapor. Hydrophilic aerogels modified by propoxylation at 28$0^{\circ}C$ for 20 h were reversed to the hydrophobic form. Transition between hydrophobicity and hydrophilicity was reversible. The hydrophobicvity and the hydrophilicity of silica aerogels were attributed to the Si-Oh bond and the nonpolar C-H bond groups of orgainc species respectively.

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Effect of the Hydrophobicity of Hybrid Gate Dielectrics on a ZnO Thin Film Transistor

  • Choi, Woon-Seop;Kim, Se-Hyun
    • Transactions on Electrical and Electronic Materials
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    • v.11 no.6
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    • pp.257-260
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    • 2010
  • Zinc oxide (ZnO) bottom-contact thin-film transistors (TFTs) were prepared by the use of injector type atomic layer deposition. Two hybrid gate oxide systems of different polarity polymers with silicon oxide were examined with the aim of improving the properties of the transistors. The mobility and threshold voltage of a ZnO TFT with a poly(4-dimethylsilyl styrene) (Si-PS)/silicon oxide hybrid gate dielectric had values of 0.41 $cm^2/Vs$ and 24.4 V, and for polyimide/silicon oxide these values were 0.41 $cm^2/Vs$ and 24.4 V, respectively. The good hysteresis property was obtained with the dielectric of hydrophobicity. The solid output saturation behavior of ZnO TFTs was demonstrated with a $10^6$ on-off ratio.

Surface free-energy and hydrophobicity of MWCNT using glow plasma at low pressure (저진공 글로플라즈마를 이용한 탄소나노튜브의 표면 자유에너지와 소수성 특성)

  • Cho, Soon-Gook;Lee, Kun-A;Kim, Jung-Won;Ko, Kwang-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.123-123
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    • 2010
  • The hydrophobic coating for multi-walled nanotubes was treated with toluene and trimethylchlorosilane glow discharge plasma under low pressure, and the hydrophobic surface of the treated MWCNT was investigates. In order to investigate the effects of -CH components from the toluene and TMCS glow plasma, we conducted on the total surface free energies of the MWCNT powder, which was calculated by measuring the contact angle between the cushion of MWCNT powder and the probe liquids. The total surface free energies were determined by Owens-Wendt equation and drastically decreased.

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Effects of solution, sorbate, and sorbent chemistries on polycyclic aromatic hydrocarbon sorption to hydrated mineral surfaces

  • Yim, Soobin
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2003.09a
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    • pp.132-135
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    • 2003
  • Solution chemistry, sorbate chemistry, and sorbent chemistry were widely investigated to find important factors that affect PAH sorption on mineral surfaces and to elucidate its microscopic mechanism. The solution chemistry, pH and ionic strength caused measurable change of HOC sorption reaction to minerals. The detectable change of Ka occurred at a pH region crossing the PZC (Point of Zero Charge) of each mineral. The PAH hydrophobicity, one of sorbate chemistry, was observed to have a strong correlation with PAM sorption to mineral. Mineral surface area was not found to be a predominant factor controlling PAH sorption. The mineral type might be more likely to play a crucial role in controlling the PAH sorption behavior. The CEC (Cation Exchange Capacity) of mineral, representing surface charge density, has meaningful correlation with regression slope of sorption coefficients (log $K_{d}$) versus aqueous activity coefficients (log Υ$_{w}$).).).

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Surface Aging Properties of Silicon Rubber Insulator by salt-fog (Silicon rubber 애자의 salt-fog 표면열화 특성)

  • Lee, Jong-Chan;Lee, Un-Yong;Cho, Han-Goo;Park, Dae-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.255-257
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    • 2001
  • In this paper, the silicon rubber insulator for transmission line was experimented for 1,000 hours aging test in salt-fog condition. To evaluate and examine the aging properties of silicon rubber insulator for test, the leakage current of surface was measured. Also hydrophobicity and scanning electron microscopy were compared with initial and aged sample respectively. Above results, we can confirm that the surface properties of silicon rubber insulator easily aged by salt-fog condition.

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