• Title/Summary/Keyword: Surface wettability

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Thermodynamic Issues of Lead-Free Soldering in Electronic Packaging (전자 패키징에 사용되는 무연 솔더에 관한 열역학적 연구)

  • 정상원;김종훈;김현득;이혁모
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.3
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    • pp.37-42
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    • 2003
  • In soldering of electronic packaging, the research on substituting lead-free solder materials for Pb-Sn alloys has become active due to environmental and health concerns over the use of lead. The reliability of the solder joint is very important in the development of solder materials and it is known that it is related to wettability of the solder over the substrate and microstructural evolution during soldering. It is also highly affected by type and extent of the interfacial reaction between solder and substrate and therefore, it is necessary to understand the interfacial reaction between solder and substrate completely. In order to predict the intermetallic compound (IMC) phase which forms first at the substrate/solder interface during the soldering process, a thermodynamic methodology has been suggested. The activation energy for the nucleation of each IMC phases is represented by a function of the interfacial energy and the driving force for phase formation. From this, it is predicted that the IMC phase with the smallest activation energy forms first. The grain morphology of the IMC at the solder joint is also explained by the calculations which use the energy. The Jackson parameter of the IMC grain with a rough surface is smaller than 2 but it is larger than 2 in the case of faceted grains.

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Study on blood compatibility of diamond-like carbon and titanium nitride films (Diamond-like carbon 및 titanium nitride 박막의 혈액적합성 연구)

  • Yun Ju-Young;Bae Jin-Woo;Park Ki-Dong;Goo Hyun-Chul;Park Hyung-Dal;Chung Kwang-Wha
    • Journal of the Korean Vacuum Society
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    • v.14 no.3
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    • pp.165-170
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    • 2005
  • There is an increasing interest in developing novel coating to improve the blood compatibility of medical implants. Diamond-like carbon(DLC) and titanium nitride(TiN) films have been proposed as potential biomedical coatings due to their chemical k physical properties and moderate biocompatibility. To study the correlation between blood compatibility and physical properties of the films, the fibrinogen adsorption on the surface as well as morphology & wettability were investigated. The quantity of fibrinogen adsorption are Tower for TiN than DLC, which correlates with a higher hydrophilicity of TiN film. To reduce the quantity of fibrinogen adsorption on the film, plasma treatment and furnace annealing were performed, respectively. With the use of oxygen plasma and furnace annealing, the amount of fibrinogen adsorption on TiN film was remarkably reduced, while there was no decrease of the quantity with DLC.

Plasma Treatment of Carbon Nanotubes and Interfacial Evaluation of CNT-Phenolic Composites by Acoustic Emission and Dual Matrix Techniques (음향 방출과 이중 기지 기술을 이용한 탄소나노튜브의 플라즈마 처리 효과에 따른 탄소나노튜브-페놀 복합재료의 계면특성 평가)

  • Wang, Zuo-Jia;Kwon, Dong-Jun;Gu, Ga-Young;Lee, Woo-Il;Park, Jong-Kyoo;Park, Joung-Man
    • Composites Research
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    • v.25 no.3
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    • pp.76-81
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    • 2012
  • Atmospheric pressure plasma treatment on carbon nanotube (CNT) surfaces was performed to modify reinforcement effect and interfacial adhesion of carbon fiber reinforced CNT-phenolic composites. The surface changes occurring on CNT treated with plasma were analyzed by using Fourier transform infrared spectroscope (FT-IR). The significant improvement of wettability on CNT was confirmed by static contact angle test after plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from $118^{\circ}$ to $60^{\circ}$. The interfacial adhesion between carbon fiber and CNT-phenolic composites increased by plasma treatment based on apparent modulus test results during quasi-static tensile strength. Furthermore, the proposed database offers valuable knowledge for evaluating interfacial shear strength (IFSS).

Interfacial Durability and Electrical Properties of CNT or ITO/PVDF Nanocomposites for Self-Sensor and Micro Actuator (자체-센서와 미세 작동기를 위한 CNT/PVDF 및 ITO/PVDF 나노복합재료의 전기적 및 계면 내구성 비교 평가)

  • Gu, Ga-Young;Wang, Zuo-Jia;Kwon, Dong-Jun;Park, Joung-Man
    • Composites Research
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    • v.24 no.6
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    • pp.12-17
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    • 2011
  • Interfacial durability and electrical properties of CNT or ITO coated PVDF nanocomposites were investigated for self-sensor and micro actuator applications. Electrical resistivity of nanocomposites for the durability on interfacial adhesion was measured using four points method via fatigue test under cyclic loading. CNT/PVDF nanocomposite exhibited lower electrical resistivity and good self-sensing performance due to inherent electrical property. Durability on the interfacial adhesion was good for both CNT and ITO/PVDF nanocomposites. With static contact angle measurement, surface energy, work of adhesion, and spreading coefficient between either CNT or ITO and PVDF were obtained to verify the correlation with interfacial adhesion durability. The optimum actuation performance of CNT or ITO coated PVDF specimen was measured by the displacement change using laser displacement sensor with changing frequency and voltage. The displacement of actuated nanocomposites decreased with increasing frequency, whereas the displacement increased with voltage increment. Due to nanostructure and inherent electrical properties, CNT/PVDF nanocomposite exhibited better performance as self-sensor and micro actuator than ITO/PVDF case.

Interfacial Durability and Acoustic Properties of Transparent xGnP/PVDF/xGnP Graphite Composites Film for Acoustic Actuator (음향 작동기를 위한 투명한 xGnP/PVDF/xGnP 그래핀 복합재료 필름의 계면 내구성 및 음향 특성)

  • Gu, Ga-Young;Wang, Zuo-Jia;Kwon, Dong-Jun;Park, Joung-Man
    • Composites Research
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    • v.25 no.3
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    • pp.70-75
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    • 2012
  • Interfacial durability and electrical properties of CNT, ITO or xGnP coated PVDF nanocomposites were investigated for acoustic actuator applications. The xGnP coated PVDF nanocomposite exhibited better electrical conductivity than CNT and ITO case due to the unique electrical property of xGnP, and this nanocomposite also showed good sound characteristics. Interfacial adhesion durability between either neat CNT or plasma treated CNT and plasma treated PVDF were measured by static contact angle, surface energy, work of adhesion, and spreading coefficient tests. The optimum acoustic actuation performance of xGnP coated PVDF nanocomposite was measured using sound level meter with changing radius of curvature and coating conditions. As compared to CNT and ITO, the xGnP was known as more appropriate acoustic actuator due to the characteristic electrical property. It is the most appropriate condition when the radius of curvature is 15 degree. Although sound characteristics were different with various coating thicknesses, it is possible to manufacture transparent actuator with good sound quality.

Interfacial Behavior of Water Droplet on Micro-Nano Structured Surfaces (마이크로-나노 구조가 있는 표면에서의 액적 계면 거동 현상에 대한 연구)

  • Kwak, Ho Jae;Yu, Dong In;Kim, Moo Hwan;Park, Hyun Sun;Moriyama, Kiyofumi;Ahn, Ho Sun;Kim, Dong Eok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.5
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    • pp.449-453
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    • 2015
  • Recently, surfaces with micro and nano structures are the focus of various research and engineering fields to enhance wetting characteristics of the surfaces. Hydrophilic surfaces with hierarchical structures are generally characterized by the interfacial behavior of water droplets. In this study, the interfacial behavior of water droplets is experimentally investigated considering the scale of structures. Using the dry etching and conventional lithography method, quantitative hierarchical structured surfaces are developed. The behavior of the liquid-vapor interface on the test sections is visualized using an automatic goniometer and a high-speed camera. On the basis of the visualized data, the interfacial behavior of water droplets is intensively investigated according to surface geometrical characteristics.

Antioxidant Activity of Dopamine-Modified Hydrogels Containing Cross-linked Hyaluronic Acid (도파민이 적용된 히알루론산 가교 하이드로겔의 항산화 활성)

  • Ryu, Geun-Chang;Hwang, Jeong Hee;Lee, Cheol-Woo
    • The Korean Journal of Vision Science
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    • v.20 no.4
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    • pp.513-521
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    • 2018
  • Purpose : : In this study, we made dopamine-functionalized hydrogels containing a cross-linked hyaluronic acid (HA) network and investigated their antioxidant activities. Methods : In the first step, we made poly hydroxyethyl methacrylate(p(HEMA))-based hydrogels post-modified with an interpenetrating polymer network(IPN) structure composed of HA polymers and a p(HEMA) network. The subsequent functionalization with dopamine via an amide coupling reaction resulted in the antioxidant hydrogels. Their antioxidant activities were evaluated using 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays. Results : The dopamine-modified hydrogels exhibited significant antioxidant activities, when compared to unmodified control. The presence of the HA-IPN structure improved the surface wettability of the hydrogel while dopamine-conjugated IPN hydrogel did not demonstrate the significant difference compared to hydrogel control. Dopamine-modified hydrogels exhibited high transmittance (>88%). Conclusion : The results demonstrate that the development of antioxidant hydrogels based on dopamine-conjugated HA-IPN structures may help develop ophthalmic and biomedical materials.

Improved Coating of PEDOT : PSS onto CVD Graphene by the Addition of PVA (PVA의 첨가에 의한 CVD 그래핀상 PEDOT : PSS의 코팅성 향상)

  • Park, Min Ui;Shin, Chaeyeon;Kim, Hyeji;Kim, Seung Yeon;Choi, Young Ju;Chung, Dae-won
    • Applied Chemistry for Engineering
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    • v.29 no.6
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    • pp.734-739
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    • 2018
  • We successfully coated poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) on CVD graphene by adding poly(vinyl alcohol) (PVA) to PEDOT : PSS. Extensive studies on the wettability of coating solutions and electrical properties of formed films led us to conclude that PVA with 89% of the degree of saponification and the molecular weight of less than $100,000gmol^{-1}$ produced optimum results. Furthermore, the optimum content of PVA was found to be 5% of PEDOT : PSS by the solid weight. The film coated by PEDOT : PSS with PVA on CVD graphene displayed a conspicuous improvement in the surface roughness, adhesive property, bending durability and stability in resistance at $160^{\circ}C$, compared to those of using CVD graphene films.

Applying nano-HA in addition to scaling and root planing increases clinical attachment gain

  • Uysal, Ozge;Ustaoglu, Gulbahar;Behcet, Mustafa;Albayrak, Onder;Tunali, Mustafa
    • Journal of Periodontal and Implant Science
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    • v.52 no.2
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    • pp.116-126
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    • 2022
  • Purpose: This study evaluated the efficacy of treating periodontitis using subgingival nano-hydroxyapatite powder with an air abrasion device (NHAPA) combined with scaling and root planing (SRP). Methods: A total of 28 patients with stage III periodontitis (grade B) were included in this study, although 1 was lost during follow-up and 3 used antibiotics. The patients were divided into a test group and a control group. All patients first received whole-mouth SRP using hand instruments, and a split-mouth approach was used for the second treatment. In the test group, the teeth were treated with NHAPA for 15 seconds at 70% power per pocket. Subgingival plaque samples were obtained from the 2 deepest pockets at the test and control sites before treatment (baseline) and 3 months after treatment. The full-mouth plaque index (PI), gingival index (GI), papillary bleeding index (PBI), bleeding on probing (BOP), probing depth (PD) and clinical attachment level (CAL) were recorded at baseline and at 1- and 3-month post-treatment. Real-time polymerase chain reaction was used to determine the colonisation of Treponema denticola (Td), Porphyromonas gingivalis (Pg), and Aggregatibacter actinomycetemcomitans in the subgingival plaque. Results: From baseline to the first month, the test group showed significantly larger changes in BOP and CAL (43.705%±27.495% and 1.160±0.747 mm, respectively) than the control group (36.311%±27.599% and 0.947±0.635 mm, respectively). Periodontal parameters had improved in both groups at 3 months. The reductions of PI, GI, BOP, PD, and CAL in the test group at 3 months were greater and statistically significant. The total bacterial count and Td and Pg species had decreased significantly by the third month in both groups (P<0.05). Conclusions: Applying NHAPA in addition to SRP improves clinical periodontal parameters more than SRP alone. Subgingival NHAPA may encourage clot adhesion to tooth surfaces by increasing surface wettability.

Electrochemical Properties of Activated Carbon Supecapacitor Containing Sulfonated Polypropylene Separator Coated with a Hydrogel Polymer Electrolyte (하이드로겔 고분자 전해질이 코팅된 술폰화 폴리프로필렌 격리막을 포함하는 활성탄 수퍼커패시터 특성)

  • Yoon, Choong Sub;Ko, Jang Myoun;Latifatu, Mohammed;Lee, Hae Soo;Lee, Young-Gi;Kim, Kwang Man;Won, Jung Ha;Jo, Jeongdai;Jang, Yunseok;Kim, Jong Huy
    • Korean Chemical Engineering Research
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    • v.52 no.5
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    • pp.553-557
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    • 2014
  • Sulfonated polypropylene (S-PP) is prepared by sulfuric acid-acetone aldol condensation reaction of polypropylene (PP) separator to yield hydrophilic separator surface with a moderate amount of $-SO_3H$ groups. Activated carbon supercapacitor is also fabricated adopting the S-PP separator coated with potassium polyacrylate (PAAK) hydrogel polymer electrolyte. As a result, the hydrophilic surface of S-PP separator involves better physical and electrochemical properties such as decrease in contact angle, improvements of wettability, electrolyte uptake, and ionic conductivity to give higher specific capacitance and long cycle-life.