• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.521-530
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• 2017

Improving the microstructure of NiO/YSZ is one of several approaches used to enhance the electrical and mechanical properties of an anode support in Solid Oxide Fuel Cells (SOFCs). The aim of the work reported in this paper was to predict the relationship between these microstructural changes and the resulting properties. To this end, modification of the anode microstructure was carried out using different sizes of Poly (Methyl Methacrylate) (PMMA) beads as a pore former. The electrical conductivity and mechanical strength of these samples were measured using four-probe DC, and three-point bend-test methods, respectively. Thermal etching followed by high resolution SEM imaging was performed for sintered samples to distinguish between the three phases (NiO, YSZ, and pores). Recently developed image analysis techniques were modified and used to calculate the porosity and the contiguity of different phases of the anode support. Image analysis results were verified by comparison with the porosity values determined from mercury porosimetry measurements. Contiguity of the three phases was then compared with data from electrical and mechanical measurements. A linear relationship was obtained between the contiguity data determined from image analysis, and the electrical and mechanical properties found experimentally. Based upon these relationships we can predict the electrical and mechanical properties of SOFC support from the SEM images.

• Journal of Adhesion and Interface
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• v.6 no.3
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• pp.10-18
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• 2005

The hard coatings on the polycarbonate plate were performed with the object of substitution the glass in the car to the polycarbonate plate. In this research, tetraethyl orthosilicate (TEOS), methyltriethoxysilane (MTES) were used to prepare the coatings by sol-gel process. The optimum conditions and formulation to get the excellent physical properties were determined. The pretreatment condition of polycarbonate plate, the mole ratio of TEOS and MTES, selection of the solvent, the aging time, the amount of acid catalyst, and the number of folds of coating were characterized. Pretreatment with poly(methyl methacrylate) was very effective to increase the adhesion strength. The smooth coating which got the 2 H class in pencil hardness was formed in this research by sol-gel process.

• Clean Technology
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• v.17 no.3
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• pp.209-214
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• 2011

The effects of inlet gas velocity (0.26-0.31 m/s), inlet gas temperature (315-353 K) and the mass ratio (0.1-0.4) of fine polymer (crosslinked poly methyl methacrylate beads) to inert medium particles on the drying rate of fine polymer in a 0.15 m-ID ${\times}$ 1.0 m-high inert medium fluidized bed dryer have been investigated. Crosslinked PMMA beads of 20 ${\mu}m$ (group C) were used as fine polymer, and glass beads of 590 ${\mu}m$ (group B) were used as the inert medium. The drying rate increases with increasing inlet gas temperature and velocity. However, the drying rate decreases slightly as the mass ratio of fine polymer to inert medium particles increases. The particle size distribution of dried fine polymers was mono distribution.

• Macromolecular Research
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• v.15 no.2
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• pp.95-99
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• 2007

The most recent developments in two areas: (a) synthesis of inorganic particles with control over size and shape by polymer additives, and (b) synthesis of inorganic-polymer hybrid materials by bulk polymerization of blends of monomers with nanosized crystals are reviewed. The precipitations of inorganics, such as zinc oxide or calcium carbonate, in presence and under the control of bishydrophilic block or comb copolymers, are relevant to the field of Biomineralization. The application of surface modified latex particles, used as controlling agents, and the formation of hybrid crystals in which the latex is embedded in otherwise perfect crystals, are discussed. The formation of nano sized spheres of amorphous calcium carbonate, stabilized by surfactant-like polymers, is also discussed. Another method for the preparation of nanosized inorganic functional particles is the controlled pyrolysis of metal salt complexes of poly(acrylic acid), as demonstrated by the syntheses of lithium cobalt oxide and zinc/magnesium oxide. Bulk polymerization of methyl methacrylate blends, with for example, nanosized zinc oxide, revealed that the mechanisms of tree radical polymerization respond to the presence of these particles. The termination by radical-radical interaction and the gel effect are suppressed in favor of degenerative transfer, resulting in a polymer with enhanced thermal stability. The optical properties of the resulting polymer-particle blends are addressed based on the basic discussion of the miscibility of polymers and nanosized particles.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.659-659
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• 2013

Recently, graphene has been intensively studied due to the fascinating physical, chemical and electrical properties. It shows high carrier mobility, high current density, and high thermal conductivity compare with conventional semiconductor materials even it has single atomic thickness. Especially, since graphene has fantastic electrical properties many researchers are believed that graphene will be replacing Si based technology. In order to realize it, we need to prepare the large and uniform graphene. Chemical vapor deposition (CVD) method is the most promising technique for synthesizing large and uniform graphene. Unfortunately, CVD method requires transfer process from metal catalyst. In transfer process, supporting polymer film (Such as poly (methyl methacrylate)) is widely used for protecting graphene. After transfer process, polymer layer is removed by organic solvents. However, it is impossible to remove it completely. These organic residues on graphene surface induce quality degradation of graphene since it disturbs movement of electrons. Thus, in order to get an intrinsic property of graphene completely remove of the organic residues is the most important. Here, we introduce modified wet graphene transfer method without PMMA. First of all, we grow the graphene from Cu foil using CVD method. And then, we deposited several metal films on graphene for transfer layer instead of PMMA. Finally, we fabricate graphene FET devices. Our approaches show low defect density and non-organic residues in comparison with PMMA coated graphene through Raman spectroscopy, SEM and AFM. In addition, clean graphene FET shows intrinsic electrical characteristic and high carrier mobility.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.291-296
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• 2007

Porous $Al_2O_3-(m-ZrO_2)$ composites were fabricated by pressureless sintering, using different volume percentages (40% - 60%) of poly methyl methacrylate (PMMA) powders as a pore-forming agent. The pore-forming agent was successfully removed, and the pore size and shape were well-controlled during the burn-out and sintering processes. The average pore size in the porous $Al_2O_3-(m-ZrO_2)$ bodies was about $200\;{\mu}m$ in diameter. The values of relative density, bending strength, hardness, and elastic modulus decreased as the PMMA content increased; i.e., in the porous body (sintered at $1500^{\circ}C$) using 55 vol % PMMA, their values were about 50.8%, 29.8 MPa, 266.4 Hv, and 6.4 GPa, respectively. To make the $Al_2O_3-(m-ZrO_2)$/polymer hybrid composites, a bioactive polymer, such as PMMA, was infiltrated into the porous $Al_2O_3-(m-ZrO_2)$ composites. After infiltration, most of the pores in the porous $Al_2O_3-(m-ZrO_2)$ composites, which were made using 60 vol % PMMA additions, were infiltrated with PMMA, and their values of relative density, bending strength, hardness, and elastic modulus remarkably increased.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.929-934
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• 2010

Improvements in characteristics of a single junction AlGaAs/GaAs solar cell are observed by capping a PMMA lens on it. In order to show the effect of the lens, characteristics of a single junction AlGaAs/GaAs solar cell before and after the lens formation are compared under the one-sun illumination condition ($100mW/cm^2$). Characteristics of the solar cell under very weak illumination condition (about 1200 lux) is also measured with the lighting of a fluorescent desk lamp. About 5% of cell efficiency is improved after the capping of PMMA lens on the single junction AlGaAs solar cell and $83\;{\mu}m/cm^2$ of electrical power was generated with the lighting of a desk lamp.

• Journal of the Korean Chemical Society
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• v.62 no.4
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• pp.269-274
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• 2018

Surface renewable nano-$RuO_2$/poly(methyl methacrylate) polymeric composite pH electrodes were prepared. The composite electrode with 53 wt% of nano-$RuO_2$ showed similar good response characteristics to nano-$IrO_2$ composite electrode reported earlier. It showed response slope of -58.7 mV/pH, response time of <1 s, surface renewability of $-57.0{\pm}0.3mV/pH$ (n=5) and long time stability for a month as well as low interferences but high interferences by electrochemically active species like $I^-$ and $Fe(CN){_6}^{3-}$. However, the response slope and time became worse at higher pH than 9 compared to those of nano-$IrO_2$ composite electrodes possibly due to the difference of physical properties resulting from higher content of nano-$RuO_2$ in polymeric composite matrix.

• Polymer(Korea)
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• v.37 no.6
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• pp.764-769
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• 2013

Starch was grafted by poly(methyl methacrylate) through the emulsion polymerization method. Modified starch/(acrylonitrile-butadiene rubber) (NBR) compounds were prepared by a latex blend method. The morphology, thermal properties and mechanical properties of the modified starch/carbon black/NBR composites were investigated with the change of starch concentration. The mechanical properties of the composites were improved by the addition of modified starch. But, when the concentration of modified starch was higher than 40 phr, the mechanical properties were deteriorated due to the poor dispersion of modified starch. At the same ratio of starch to carbon black, the composite showed a synergistic reinforcing effect by the good dispersion and high cross-linking density. In addition, the tensile strength, storage modulus, hardness, swelling and other properties were the best.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.170-170
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• 2000

Synthetic polymers such as polyimide, polycarbonate, and poly(methyl methacrylate) are long chain molecules which consist of carbon, hydrogen, and heteroatom linked together chemically. Recently, polymer surface can be modified by using a high energy ion beam process. High energy ions are introduced into polymer structure with high velocity and provide a high degree of chemical bonding between molecular chains. In high energy beam process the modified polymers have the highly crosslinked three-dimensionally connected rigid network structure and they showed significant improvements in electrical conductivity, in hardness and in resistance to wear and chemicals. Polyimide films (Kapton, types HN) with thickness of 50~100${\mu}{\textrm}{m}$ were used for investigations. They were treated with two different surface modification techniques: Plasma Source Ion Implantation (PSII) and conventional Ion Implantation. Polyimide films were implanted with different ion species such as Ar+, N+, C+, He+, and O+ with dose from 1 x 1015 to 1 x 1017 ions/cm2. Ion energy was varied from 10keV to 60keV for PSII experiment. Polyimide samples were also implanted with 1 MeV hydrogen, oxygen, nitrogen ions with a dose of 1x1015ions/cm2. This work provides the possibility for inducing conductivity in polyimide films by ion beam bombardment in the keloelectronvolt to megaelectronvolt energy range. The electrical properties of implanted polyimide were determined by four-point probe measurement. Depending on ion energy, doses, and ion type, the surface resistivity of the film is reduced by several orders of magnitude. Ion bombarded layers were characterized by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), XPS, and SEM.