• 한국산림과학회지
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• 제83권1호
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• pp.32-37
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• 1994

리기다소나무와 잣나무 유묘에 인위적으로 산도를 조절한 인공산성우(pH 3.0, 4.0 및 5.0)와 지하수(pH 6.5)를 1992년 4월부터 1993년 8월까지, 생육기간 중에는 주 2회, 겨울철은 주 1회 1회 5mm의 강도로 처리하였다. 인공산성우를 처리하면서 수종별 침엽의 접촉각(contact angle)을 조사 비교하여 얻은 결과는 다음과 같다. 침엽의 표면과 물방울이 이루는 접촉각을 측정한 결과, 처리산성우의 산도수준이 높을수록 엽령이 높을수록 접촉각의 크기는 낮아졌다. 침엽의 접촉각을 측정 비교하는 방법은 야외에서 침엽수류에 대한 산성우 피해의 조기판단을 위한 매우 효과적인 기준이라 판단된다.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.6-9
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• 2010

Surface properties of polytetrafluoroethylene(PTFE) films fabricated by rf-magnetron sputtering system with UV surface treatment were investigated to increase water contact angle for their hydrophobic property. We found that the surface morphology and water contact angles of PTFE film modified as a function of the UV treatment times using UV-irradiation were influenced. The water contact angle of PTFE film with optimized UV treatment time for 15 minute showed a high hydrophobicity compared with the film without any surface treatment. We thought that it was due to the energy change of PTFE surface with an adhesion improvement to the glass surface as a smoothing a rough surface with needle-shape and/or the enhancement of an interface property as a removing some defects on the surface like a cleaning effect.

• 반도체디스플레이기술학회지
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• 제19권1호
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• pp.73-78
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• 2020

There appears lateral capillary force in a hydrophilic flat needle employed for the fabrication of fine organic thin-film stripes, bringing in an increase of the stripe width. It also causes the stripe thickness to increase with increasing coating speed, which is hardly observed in a normal coating process. Through computational fluid dynamics (CFD) simulations, we demonstrate that the lateral capillary flow can be substantially suppressed by increasing the contact angle of the needle end. Based on the simulation results, we have coated the outer surface of the flat needle with a hydrophobic material (polytetrafluoroethylene (PTFE) with the water contact angle of 104°). Using such a hydrophobic needle, we can suppress the lateral capillary flow of an aqueous poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) to a great extent, rendering the stripe narrow (63 ㎛ at 30 mm/s). Consequently, the stripe thickness is decreased as the coating speed increases. To demonstrate its applicability to solution-processable organic light-emitting diodes (OLEDs), we have also fabricated OLED with the fine PEDOT: PSS stripe and observed the strong light-emitting stripe with the width of about 68 ㎛.

• Computers and Concrete
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• 제23권5호
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• pp.351-359
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• 2019

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various $CO_2$ pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing $CO_2$ pressure and temperature, and reached to an optimum value at around $90^{\circ}C$. The maximum static water contact angle of 128.7 degree was obtained at the $CO_2$ pressure of 2 atm and temperature of $90^{\circ}C$. It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of $CaCO_3$ synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.

• 한국환경생태학회지
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• 제7권1호
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• pp.10-21
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• 1993

소나무, 곰솔, 젓나무 및 독일가문비를 대상으로 인위적으로 산도를 조절한 인공산성우(PH 3.0, 4.0 및 5.0)와 지하수(pH 6.5)를 1991년 4월부터 1993년 8월까지, 생육기간 중에는 주 2~3회, 겨울철은 주 1회 1회 5mm의 강도로 처리하였다. 인공산성우를 처리하면서 수종별 발아 및 득묘율, 토양산도, 유묘의 생장 및 접촉각(contact angle)을 조사.비교하여 얻은 결과는 다음과 같다. 묘목의 생장관련 형질(묘고, 지하부, 엽량 및 개체당 건중량)의 경우에는 산성우처리 초기에는 산성우 처리가 양료로서의 효과를 가지는 것으로 판단되며, 수종별로 상이한 반응을 보였다. 그러나 처리가 2년 이상 지속된 3차년도에서는 처리산성우의 산도수준이 높을수록 모든 수종에서 생장관련 형질들이 감소되는 경향을 보였으며, 이는 토양완충력의 한계 이상으로 투하되는 산집적에 의한 결과로 판단된다. 엽피해율이나 엽량(낙엽율)등의 자료는 처리산성우의 산도수준과 관련지어져 있는 것으로 나타나 산성우 피해의 조기판단 기준으로 사용가치가 높을 것으로 판단된다. 토양산도는 처리간 고도의 통계적 유의차가 인정되었다. 침엽의 표면과 물방울이 이루는 접촉각을 측정한 결과, 처리산성우의 산도수준이 높을수록 엽령이 높을수록 접촉각의 크기는 낮아졌다. 접촉각을 측정비교하는 방법은 야외에서 침엽수류에 대한 산성우 피해의 조기판단을 위한 알맞고 훌륭한 기준이라 판단된다.

• 한국표면공학회지
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• 제46권4호
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• pp.145-152
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• 2013

The growth behavior of nanocrystalline diamond (NCD) film has been studied for three different substrates, i.e. bare Si wafer, 1 ${\mu}m$ thick W and Ti films deposited on Si wafer by DC sputter. The surface roughness values of the substrates measured by AFM were Si < W < Ti. After ultrasonic seeding treatment using nanometer sized diamond powder, surface roughness remained as Si < W < Ti. The contact angles of the substrates were Si ($56^{\circ}$) > W ($31^{\circ}$) > Ti ($0^{\circ}$). During deposition in the microwave plasma CVD system, NCD particles were formed and evolved to film. For the first 0.5h, the values of NCD particle density were measured as Si < W < Ti. Since the energy barrier for heterogeneous nucleation is proportional to the contact angle of the substrate, the initial nucleus or particle densities are believed to be Si < W < Ti. Meanwhile, the NCD growth rate up to 2 h was W > Si > Ti. In the case of W substrate, NCD particles were coalesced and evolved to the film in the short time of 0.5 h, which could be attributed to the fact that the diffusion of carbon species on W substrate was fast. The slower diffusion of carbon on Si substrate is believed to be the reason for slower film growth than on W substrate. The surface of Ti substrate was observed as a vertically aligned needle shape. The NCD particle formed on the top of a Ti needle should be coalesced with the particle on the nearby needle by carbon diffusion. In this case, the diffusion length is longer than that of Si or W substrate which shows a relatively flat surface. This results in a slow growth rate of NCD on Ti substrate. As deposition time is prolonged, NCD particles grow with carbon species attached from the plasma and coalesce with nearby particles, leaving many voids in NCD/Ti interface. The low adhesion of NCD films on Ti substrate is related to the void structure of NCD/Ti interface.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권6호
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• pp.566-574
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• 2006

Purpose : This study was performed to provide an anatomical information of the mandibular ramus for the successful inferior alveolar nerve block. Three dimensional images were reconstructed from the computerized tomography (CT) and the anatomical evaluation of the mandibular ramus was done. Materials and methods : Sixty-four patients who had been taken the facial CT scans from 2000, Jan to 2003, June was selected. The patients who had the anterior or posterior teeth misssing, edentulous ridge, and jaw fracture were excepted. In the occulusal plane, the lingual surface angle (LSA) between the mid-sagittal plane and the mandibular molar lingual surface from the 2nd premolar to the 2nd molar, the inner ramal surface angle (IRSA), the maximum inner ramal surface angle (MxIRSA), and the outer ramal surface angle (ORSA) to the-mid sagittal plane were measured. The inner ramal surface angle in the ligular tip level (IRSA-L) and the outer ramal surface angle in the ligular tip level (ORSA-L), the ramal length (RL), and the anterior ramal length (ARL) were also measured in the lingular tip level. Results : In the lingular tip level, the mean IRSA-L and ORSA-L were $28.6{\pm}6.3^{\circ}$ and $17.9{\pm}4.9^{\circ}$ respectively. The larger was the IRSA, the larger was the ORSA. In the lingular tip level, the mean ramal length was 35.8${\pm}$3.4 mm. The larger was the IRSA-L, the shorter was the ramal length. On the lingular tip level, the mean anterior ramal length from anterior ramus to lingular tip was 19.6${\pm}$3.3 mm. when the ramal length was longer, the anterior ramal length was also longer. On the lingular tip level, there was positive correlation vetween the IRSA and the ORSA, negative correlation between the IRSA and the ramal length, and positive correlation between the ramal length and the lingular tip level to the anterior ramus. There was no statistical meaning of data between sex and age. Conclusion : In the clinical view of the results so far achieved, if the direction of needle is closer to posterior it is able to contact bone on lingular tip when the internal surface of ramus is wided outer.

• Journal of Korean Dental Science
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• 제10권1호
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• pp.10-21
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• 2017

Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.