• Journal of the Korean Wood Science and Technology
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• 제38권4호
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• pp.316-322
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• 2010

본 연구의 목적은 폐식용유를 오존산화 처리에 의한 구조적 변성을 시도하고 이를 pMDI와 반응시켜 목재접착제로 개발하고자 하는 것이다. 폐식용유를 사용하여 1, 2, 3시간 오존산화 처리 한 후 화학적 변화를 알아보기 위하여 FT-IR을 측정하였다. 또한 접착강도를 조사하기 위하여 상태, 내수, 내온수, 반복끓임 실험을 하였다. FT-IR 측정 결과, 폐식용유의 오존산화가 진행될수록 불포화 이중결합에 기인한 3,010 $cm^{-1}$ 부근의 흡수가 사라지고 1,700 $cm^{-1}$ 부근의 카르복실기의 흡수가 크게 나타났다. 특히 3시간대에 3,010 $cm^{-1}$ 부근에 이중결합이 거의 사라짐을 알 수 있었다. 3시간 처리한 폐식용유의 상태 접착력 시험 결과, 폐식용유: pMDI 비율이 1 : 0.5일 때 8.08 kgf/$cm^2$, 1 : 0.75일 때 9.53 kgf/$cm^2$, 1 : 1일 때 44.16 kgf/$cm^2$ 1 : 2일 때 58.08 kgf/$cm^2$, 1 : 3일 때 61.41 kgf/$cm^2$, 1 : 4일 때는 46.95 kgf/$cm^2$를 나타내어 MDI와의 적정당량이 1 : 2, 1 : 3 부근에서 결정됨을 알 수 있었다. 중량비 1 : 2, 1 : 3만을 선택하여 각각 내수, 내온수, 반복끓임 상태로 접착강도 시험을 실시하였다. 내수 접착강도에서는 1 : 3의 경우가 더 높은 값을 보였으나 실험조건이 강화된 내온수, 반복 끓임에서는 혼합비율 1 : 2와 1 : 3이 비슷한 값을 나타내었다.

• 한국재료학회지
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• 제18권9호
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• pp.503-506
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• 2008

The effect of silver nanoparticles (NPs) incorporation on the electronic properties of poly (3, 4-ethylenedioxythiphene) : poly(styrenesulfonate) (PEDOT : PSS) films was investigated. The surface of silver NPs was stabilized with trisodium citrate to control the size of silver NPs and prevent their aggregation. We obtained ca. 5 nm sized silver NPs and dispersed NPs in PEDOT : PSS solution. Sheet resistance, surface morphology, bonding state, and work function values of the PEDOT : PSS films were modified by silver NPs incorporation as well as annealing temperature. Sodium in silver NPs solution could lead to a decrease of work function of PEDOT : PSS; however, large content of silver NPs have an effect on the increase in work function, resulting from charge localization on the silver NPs and a decrease in the number of charge-trapping-related defects by chemical bond formation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.467-470
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• 2004

Diamond-Like Carbon (DLC) thin film is a semiconductor with high mechanical hardness, low friction coefficient, high chemical inertness, and optical transparency. DLC thin films have widespread applications as protective coatings and solid lubricant coatings in areas such as Hard Disk Drive (HDD) and Micro-Electro-Mechanical-Systems (MEMS). In this work, the wear characteristics of DLC thin films deposited on silicon substrates using a DC-magnetron sputtering system were analyzed. The wear tracks were measured with an Atomic Force Microscope (AFM). To identify the sp2 and sp3 hybridization of carbon bonds and other bonds Raman spectroscopy was used. The structural information of DLC thin films was obtained with Fourier transform infrared spectroscopy and wear tests were conducted by using a micro-pin-on-reciprocator tester. Results showed that the wear characteristics were dependent on the sputtering conditions. The wear rate could be correlated with the bonding state of the DLC thin film.

• Carbon letters
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• 제13권3호
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• pp.139-150
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• 2012

Poly-L-lactic acid (PLLA), PLLA/hydroxyapatite (HA), PLLA/multiwalled carbon nanotubes (MWNTs)/HA, PLLA/trifluoroethanol (TFE), PLLA/gelatin, and carbon nanofibers (CNFs)/${\beta}$-tricalcium phosphate (${\beta}$-TCP) composite membranes (scaffolds) were fabricated by electrospinning and their morphologies, and mechanical properties were characterized for use in bone tissue regeneration/guided tissue regeneration. MWNTs and HA nanoparticles were well distributed in the membranes and the degradation characteristics were improved. PLLA/MWNTs/HA membranes enhanced the adhesion and proliferation of periodontal ligament cells (PDLCs) by 30% and inhibited the adhesion of gingival epithelial cells by 30%. Osteoblast-like MG-63 cells on the randomly fiber oriented PLLA/TEF membrane showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel fiber oriented membrane. Classical supersaturated simulated body fluids were modified by $CO_2$ bubbling and applied to promote the biomineralization of the PLLA/gelatin membrane; this resulted in predictions of bone bonding bioactivity of the substrates. The ${\beta}$-TCP membranes exhibit good biocompatibility, have an effect on PDLC growth comparable to that of pure CNF membrane, and can be applied as scaffolds for bone tissue regeneration.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.203-210
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• 2004

Consolidation properties were analysed by means of depositional environments. Depositional environments including geochemical properties, porewater chemistry, sediment structures, particle size distributions and carbon age dating were analysed using undisturbed samples retrieved successively from a boring hole in the study area. Laboratory oedometer tests and anisotropic consolidated triaxial tests(CKoUC) were performed to examine the overconsolidation phenomenons. Based on the carbon age dating results and profiles of geochemical properties, porewater chemistry, salinity and pH, it was founded that the upper silt/clay complex layer was deposited under marine condition while sand and clay layers were deposited under fluvial condition. Planar laminated structures of silts and clays were dominant in marine deposits. Although there was no clear evidences that geological erosion had been occurred in marine deposits, overconsolidation ratio obtained from oedometer tests were greater than unity. Stress paths of samples behaved similar to those of normally consolidated clays. Data plotted in stress state charts proposed by Burland(1990) and Chandler(2000) showed that the marine deposits were geologically normally consolidated. These apparent overconsolidations can be explained by the fabric and chemical bonding due to the difference of the rate of deposition.

• 한국포장학회지
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• 제5권2호
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• pp.1-8
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• 1999

The state of compatability of poly(vinyl alcohol)(PVA) and methyl cellulose(MC), prepared by an aqueous solution casting, were investigated over the entire compositions by dynamical mechanical analyzer(DMA) and differential scanning calorimetry(DSC). The glass transition temperatures of the blends, estimated by DMA, indicate that the blends of PVA and MC showed a definite degree of partial miscibility by showing two glass transition temperatures below 80 wt % MC contents in the blends and one glass transition temperature above 80 wt % of MC contents. The DSC results show a depression of melting point and crystallization temperature of PVA in the blends containing more than 80 wt % MC. This indicates that a considerable compatibility in the blend above 80 wt % MC contents may be attribute to the presence of interaction of hydroxyl groups of component polymers through hydrogen bonding. The DMA study of the effect of plasticizer on the polymers showed that water was a good plasticizer for PVA and PEG400 for MC. The addition of water and PEG400 in the blends showed a synergic plasticizing effect on these blends, which resulted in the large extent of the improvement of the compatibility. The elongation of PVA, MC and blonds was found to increase with addition of PEG400 in the blends, but the tensile strength to decrease with addition of plasticizer.

• 한국산학기술학회논문지
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• 제11권5호
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• pp.1768-1772
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• 2010

분자내부 회합은 계면활성제계, 특히 콜로이드와 생체물질에 있어서 수소결합 중에서 매우 중요한 역할을 나타낸다. 미셀과 마이크로에멀젼을 형성하는 양친매성 계는 분자간 회합뿐만 아니라 분자내부 회합 때문에 매우 비이상적인 거동을 나타낸다. 본 연구의 목적은 계면활성제를 함유한 혼합물의 상거동을 계산하기 위하여, 내외부 분자 회합을 설명할 수 있는 수정된 베이츠만 통계역학이론과 결합된 유사화학반응 비무질도서 격자모델을 제시하는 것이다. 본 논문에서 제시된 격자모델은 알칸과 계면활성제의 실험결과를 매우 잘 설명할 수 있다.

• 열처리공학회지
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• 제13권2호
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• pp.91-97
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• 2000

The structure and mechanical properties of TiN and TiCN thin films deposited on STD61 steel substrates by the RF-sputtering methods has been studied by using XPS, XRD, micro-hardness tester, scratch tester, and wear-resistance tester. XPS results showed that the TiCN thin film formed with chemical bonding state. The TiN thin films grew with (111) orientation having the lowest strain energy by compressive stress, whereas the TiCN thin films grew with both (111) and (200) orientation, but (200) orientation having the lowest surface energy becomes dominant as carbon contents increase. The pre-etching treatment of substrate did not affect on the preferred orientation of thin films, but it played an important role in improving mechanical properties of thin films such as the hardness, adhesion and wear- resistance. Especially, the TiCN thin films showed the superior wear resistances due to high hardness and low friction coefficient compared with TiN thin films.

• 한국기계가공학회지
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• 제9권1호
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• pp.106-113
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• 2010

The most suitable condition for plasma source ion implantation(PSII) was found based on the study of the characteristics of PSIIed tool and machined surfaces. The depth analysis according to the chemical bonding state of elements and surface component elements through the XPS and SIMS, was conducted to find the improved property of the PSIIed surface. Due to the diffusion of PSII, the nitrogen was found up to a depth of about 150nm according to the supplied voltage and ion implanted time. The deep diffusion by nitrogen caused the surface modification, but the formation of oxide component was found due to the residual gas contamination on the surface. Statistical method of ANOVA was conducted to find the effects of spindle speed and feed rate in interaction for machined surface roughness with PSIIed tools. The surface modification was found largely occurred by the nitrogen implanted surface with 2 hours for 27kV, 35kV and 43kV.

• Elastomers and Composites
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• 제54권3호
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• pp.209-219
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• 2019

It is important to analyze crosslink densities of rubber articles because the physical properties are dependent on the crosslink densities. In this paper, analytical techniques for the measurement of crosslink densities of rubber vulcanizates are described. The most widely used method to measure the crosslink density is a swelling method combined with the Flory-Rehner equation. Application of the interaction parameter (${\chi}$) of rubber and swelling solvent is critical because the crosslink density is absolutely dependent on the ${\chi}$ value. Methods for obtaining ${\chi}$ employ not only solubility parameters of the polymer and swelling solvent but also inverse gas chromatography (IGC). The solubilities of rubbers can be obtained using micro differential scanning calorimetry (${\mu}DSC$), intrinsic viscosity measurement, and UV-visible spectroscopy. Nuclear magnetic resonance (NMR) spectroscopy has been also used for the measurement of the crosslink density using the $T_2$ relaxation time, which is determined by spin-spin relaxation in solid-state NMR. For sulfur-cured rubber vulcanizates, crosslink densities according to the crosslink types of mono-, di-, and polysulfides are measured by treating the rubber samples with a chemical probe composed of thiol and amine compounds. Measurement methods of physical crosslinking by filler, crystallization, and ionic bonding have also been introduced.