• Journal of Adhesion and Interface
• /
• v.18 no.2
• /
• pp.75-81
• /
• 2017

In this study, we synthesized mesoporous carbon (Carbonized Ni-FDU-15) containing nanoporous structures and magnetic nanoparticles. Carbonized Ni-FDU-15 was synthesized via evaporation-induced self-assembly (EISA) and direct carbonization by using a triblock copolymer (F127) as a structure-directing agent, a resol precursor as a carbon-pore wall forming material, and nickel (II) nitrate as a metal ion source. The mesoporous carbon has a well-ordered two-dimensional hexagonal structure. Meanwhile, nickel (Ni) metal and nickel oxide (NiO) were produced in the magnetic nanoparticles in the pore wall. The size of the nanoparticles was about 37 nm. The surface area, pore size and pore volume of Carbonized Ni-FDU-15 were $558m^2g^{-1}$, $22.5{\AA}$ and $0.5cm^3g^{-1}$, respectively. Carbonized Ni-FDU-15 was found to move in the direction of magnetic force when magnetic force was externally applied. The magnetic nanoparticle-bearing mesoporous carbons are expected to have high applicability in a wide variety of applications such as adsorption/separation, magnetic storage media, ferrofluid, magnetic resonance imaging (MRI) and drug targeting, etc.

• Korean Journal of Soil Science and Fertilizer
• /
• v.36 no.5
• /
• pp.263-271
• /
• 2003

Effects of the existence of $CO_2$ gas and pH on the silica surface characteristics at silica/Pb(II) and sodium dodecyl sulfonate (SDS, $C_{12}H_{25}SO_3Na$) solution interface were studied. The hydrophobic characteristics of silica surface was delineated by contact angle measurement and surface force measurement using atomic force microscopy (AFM). In $CO_2$ free condition provided by purging $N_2$ gas, the contact angle of fused silica surface in $10^{-4}M$ Pb(II) and SDS solution increased greatly up to $90^{\circ}$ compared with $40^{\circ}$ in atmospheric condition. It was due to the precipitation of $PbCO_3$ in atmospheric condition. In $CO_2$ free condition the change of contact angle and adhesion force ($F_{ad}$) in AFM, affected by pH change, was similar to the distribution of $PbOH^+$ ion in speciation diagram corresponding to $10^{-4}M$ total Pb(II). Therefore, it was convinced that the $PbOH^+$ ion among Pb(II) species would be the main adsorbing type on silica surface. Both of contact angle measurement and surface force measurement using AFM showed that the Pb only treatment made the silica surface hydrophobic. However, it could not be explained theoretically by current knowledge, and required further study in atomic level to solve the problem.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.1
• /
• pp.461-467
• /
• 2021

Among the defect factors that can occur when a wafer-level lens is molded using a thermosetting material, the mold sticking problem of a molded lens during the release process can damage the molded substrate and deform the substrate at the wafer level. An experiment was conducted to examine the factors affecting the demolding force in the lens forming process. The demolding force was examined according to the coating material of the molds. The mold was surface-treated with ITO and Ti, followed by plasma treatment in an O2 atmosphere. A DLC coating was then performed, and the curing and releasability were examined. A coating method for the pull-off experiment was selected based on the results. To measure the demolding force according to the curing process conditions, a method of curing at a constant pressure and a method of curing at a constant position were applied. As a result, the TiO2 surface treatment reduced the release force. When cured by controlling the location, curing shrinkage can reduce the adhesion energy of the interface during curing, resulting in better demolding.

• International Journal of Highway Engineering
• /
• v.3 no.4 s.10
• /
• pp.117-126
• /
• 2001

In this research, evaluation of adhesion in tension property of SBR-modified concrete to ordinary portland cement concrete was conducted with uniaxial direct tensile bond test which was proposed by Kuhlmann. A test set-up was fabricated in order to minimize the eccentric force by introducing a joint which might fully rotate. The main experimental variables were cement-latex ratios, surface preparations and moisture levels. The results obtained were as follows: The LMC specimen at 15% latex-cement ratio increased the adhesion in tension by range of 37% compared to that of conventional cement concrete. This might be due to latex film formed between cement paste and aggregate. The effects of surface preparation on bond of latex modified concrete to conventional concrete were significant at the conditions by sand paper and wire brush. A better bond could be achieved by rough surface rather than smooth. The saturated and surface dry (SSD) condition were considered to be the most appropriate moisture level followed by wet, finally by dry. Thus, a proper surface preparation and moisture level are quite necessity in order to obtain better bonding at LMC overlay.

• Journal of Life Science
• /
• v.33 no.4
• /
• pp.334-342
• /
• 2023

Forty species of lactic acid bacteria isolated from gajami sikhae were identified as Lactobacillus plantarum, Leuconostoc mesenteroides, Lactobacillus brevis, and Weissella paramesenteroides. 10 of the 40 strains were selected and used for the test. In this study, experiments such as those using acid and artificial gastric juice resistance, bile acid resistance, autoaggregation, coaggregation, and cell surface hydrophobicity were conducted to utilize lactic acid bacteria separated from gajami sikhae as probiotics. The separated lactic acid strains showed high survival rates through displaying resistance to acidic and artificial gastric juices; L. plantarum GS11 showed the best resistance. Also, as a result of a measurement of bile acid resistance, all lactic acid bacteria stocks showed survival of more than 100% with a probiotic number of 10⁸ to 10⁹ log CFU/ml. After evaluating cohesion to indirectly measure cell surface adhesion, autoaggregation ability was shown to be more than 46%. Measurement of xylene adhesion for cell surface hydrophobicity evaluation revealed better cell adhesion than B. subtilis, which has 32.2% hydrophobicity in isolated lactic acid strains. Antibacterial force measurement found antibacterial activity in lactic acid bacteria, excluding L. plantarum GS12 and L. plantarum GS13. Therefore, it was judged that lactic acid bacteria separated from gajami sikhae could be used as probiotics with various probiotic properties.

• Journal of the Microelectronics and Packaging Society
• /
• v.19 no.3
• /
• pp.77-82
• /
• 2012

In this paper, the research of IC embedded PCB process is carried out. For embedding chips into PCB, solder-balls on chips were etched out and ABF(Ajinomoto Build-ip Film), prepreg and Cu foil was laminated on that to fabricate 6 layer build-up board. The chip of which solder ball was removed was successfully interconnected with PCB by laser drilling and Cu plating. However, de-lamination phenomenon occurred between chip surface and ABF during reflow and thermal shock. To solve this problem, de-smear and plasma treatment was applied to PI(polyimide) passivation layer on chip surface to improve the surface roughness. The properties of chip surface(PI) was investigated in terms of AFM(Atomic Force Micrometer), SEM and XPS (X-ray Photoelectron Spectroscopy). As results, nano-size anchor was evenly formed on PI surface when plasma treatment was combined with de-smear(NaOH+KMnO4) process and it improved thermal shock reliability ($260^{\circ}C$-10sec solder floating).

• KSTLE International Journal
• /
• v.6 no.1
• /
• pp.13-16
• /
• 2005

Friction characteristics at nano-scale of self-assembled monolayers (SAMs) having different chain lengths and end groups were experimentally studied.51 order to understand the effect of the chain length and end group on the nano-scalefriction: (1) two different SAMs of shorter chain lengths with different end groups such as methyl and phenyl groups, and (2)four different kinds of SAMs having long chain lengths (C10) with end groups of fluorine and hydrogen were coated on siliconwafer (100) by dipping method and Chemical Vapour Deposition (CVD) technique. Their nano-scale friction was measuredusing an Atomic Force Microscopy (AFM) in the range of 0-40 nN normal loads. Measurements were conducted at the scanning speed of 2 $mu$m/s for the scan size of 1$mu$m x 1 $mu$m using a contact mode type $Si_3N_4$ tip (NPS 20) that had a nominal spring constant0.58 N/m. All experiments were conducted at anlbient temperature (24 $pm$1$circ$C) and relative humidity (45 $pm$ 5%). Results showedthat the friction force increased with applied normal load for all samples, and that the silicon wafer exhibited highest frictionwhen compared to SAMs. While friction was affected by the inherent adhesion in silicon wafer, it was influenced by the chainlength and end group in the SAMs. It was observed that the nano-friction decreased with the chain length in SAMs. In the caseof monolayers with shorter length, the one with the phenyl group exhibited higher friction owing to the presence of benBenerings that are stiffer in nature. In the case of SAMs with longer chain length, those with fluorine showed friction values relativelyhigher than those of hydrogen. The increase in friction due to the presence of fluorine group has been discussed with respect tothe siBe of the fluorine atom.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.17 no.6
• /
• pp.665-674
• /
• 2015

A TSL (Thin Spray-on Liner) which consists of polymers has a higher initial strength, faster construction time and higher waterproofing performance than the conventional cementitious shotcrete. Main supporting mechanism of TSL is the adhesion and tensile strength which is distinct from the conventional shotcrete. Even though highly in demand due to its outstanding characteristics, TSL is not yet well-known support material. In this study, to evaluate contact behavior of TSL, numerical analysis was performed with comparing result from laboratory tests. From the analysis, cohesive behavior at the contact surface between TSL and rock can be evaluated by using combination of cohesive and the damage model. In addition, results show that the cohesive stiffness controled slope between force and displacement, the fracture energy controled level of force at the contact.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.12 no.2 s.27
• /
• pp.225-235
• /
• 1988

The effects of surface free energy of substrates on the soiling and on the detergency of the oily soil were studied. The surface tension consisted of dispersion force and polar force components of substrate, oily soil and surfactant solutions were calculated by extended Fowkes' equation. From these values, work of adhesion($W_a$), work of detergency($W_D$), ana residual work of detergency($W_{D,R}$) were calculated. The correlations between these theoretical values of the works and detergency were discussed. MAA grafted PET film was used as substrate, triolein as oily soil and nonylphenol polyoxyethylene ether(NPE) having various mole numbers of oxyethylene adducts and dodecylbenzene sulfonate (DBS) as surfactants. Detergency was estimated by means of radioactive tracer method using $C^{14}-triolein$. The results showed that $W_a$ was decreased with the increase of surface free energy of substrate. In water, $W_D\;and\;W_{D,R}$ were decreased and detergency of tiolein was increased with the increase of surface free energy of substrate. In surfactant solutions, the lower the surface free energy of substrate and the lower oxyethylene adducts of NPE were the more effective on detergency. The detergency of DBS solution was the lowest in the case of ungrafted PET film, but even small increase in surface free energy by grafting showed much increase in detergency.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.6
• /
• pp.513-519
• /
• 2014

For depth machining in die and mold, Electrical Discharge Machining (EDM) is used generally. To make deep hole and deep shape efficiently, cemented carbide endmill for depth machining is necessary. For this purpose, cemented carbide endmill was designed using design of experiment (DOE). To improve cutting performance, endmill was coated with multilayer surface treatment, TiAlCrSiN and TiAlCrN, for higher wear resistance. In order to evaluate the endmill, Transverse Rupture Strength (TRS) test was tried for investigating the relationship between surface treatment and strength in endmill body. Scratch test was also used for measuring adhesion force of each surface treatment. To evaluate hardness of surface treatment, Atomic Force Microscope (AFM) analysis was carried out. Wear test was executed for characteristics of each surface treatment in high temperature. Consequently, TiAlCrSiN was superior to the TiAlCrN coating in case of high temperature environment such as cutting.