• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.103-109
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• 2007

In this study, the rheological properties of cement pastes containing blastfurnace slag of different fineness were investigated. The fluidity of cement pastes with low Blaine value blastfurnace slag was increased with decreasing the plastic viscosity and the yield stress of pastes. And the optimum dosage of polycarboxylate type superplasticizer to the cement pastes was confirmed according to the fineness and the replacement ratio of blastfurnace slag. All cement pastes showed the thixotropy behavior. And also it was formed that the segregation range of cement pastes was occurred below $10D/cm^2$ of the yield stress and below 350 cPs of the plastic viscosity by the coaxial cylinder viscometer.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.69-78
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• 2016

Liquid crystals are important materials because of their applications in display technology and many other scientific applications. Different mixtures of liquid crystals and their doped samples have gained interest because a single liquid crystal compound cannot fulfill all the required parameters for the display application. The doping can be accomplished with dyes, polymers, or composite nanoparticles among other substance. The addition of nanoparticles can modify the physical properties of the host liquid crystal and enhances the performance of electro-optical devices. The present study is focused on investigations of possible changes in dielectric and electro optical properties of liquid crystals caused by doping with ceramic nanoparticles. Including smaller nanoparticles were found to be better candidates for use in suppressing the unwanted ion effects in liquid crystal displays.

• Journal of the Korean Ceramic Society
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• v.51 no.1
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• pp.32-36
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• 2014

The effects of an amphiphilic agent and the orientation of BN on the microwave dielectric properties of BN / polyvinyl butyral (PVB) composites were investigated as a function of the BN content in volume fractions from 0.1 to 0.5 ($V_f$). The plate-shaped BN samples were oriented in the PVB matrix by physical processes, in this case tape casting and laminate methods. With an increase in the BN content, the dielectric constant (K) increased because the K of BN was higher than that of the PVB. At the same BN content, composites with an in-plane orientation of the BN showed a higher dielectric constant than that of composites with a transverse orientation of the BN because the ceramics were oriented parallel to the electric field. All of the composites showed nearly constant K values ranging from 1 to 9.4 GHz, indicating good frequency stability over a wide frequency range. At the same frequency, the K values of the composites increased with an increase in the BN content.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1507-1512
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• 1994

High strength cement hardened body was prepared by ordinary portland cement, silica-fume, super-plasticizer and the industrial by-product powder such as tailing, paper sludge ash and granulated slag. These raw materials were mixed and formed with w/c=0.18. The cement hardened body is cured in the autoclave at 18$0^{\circ}C$, 10atm. These admixtures made the compressive strength of all specimens develope by 170~230%. The highest compressive strength could be obtained by 236 MPa when mix composition was 14 wt% of silica-fume and 26 wt% of granulated slag. The compressive strength increased with decreasing the average pore size and the amount of the poe over the size of 50 nm by which the appearance of high compressive strength of the cement hardened body were mainly influenced. In the result, the hydration products were C-S-H, tobermorite and ettringite and it was realized that the reason why the cement hardened body became dense and revealed the higher strength was that those hydrates were formed inside of the pore and filled in it and the unhydrated materials played the role of an inner-filler.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.212-215
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• 2010

$BiFeO_3/Pb(Zr_{0.95}Ti_{0.05})O_3$ (BFO/PZT) heterolayered thin films were fabricated by the spin coating method on a Pt/Ti/$SiO_2$/Si substrate using metal alkoxide solutions. The coating and heating procedure was repeated 6 times to form the heterolayered films. The thickness of the BFO/PZT films after one cycle of drying/sintering is about 30-40 nm. All BFO/PZT films show a void free uniform grain structure without the presence of rosette structures. It can be assumed that the crystal growth of the upper BFO layers can be influenced by the lower PZT layers. As the number of coatings increased, the dielectric constant increased, so that the value for the 6-layer film was 1360 at 1 KHz.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.777-786
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• 2005

The Solid Oxide Fuel Cell (SOFC) is an electrochemical device to convert chemical energy of a fuel into electricity at temperatures from about 600 to $1000^{\circ}C$. The SOFC offers certain advantages over lower temperature fuel cells, notably its ability to use CO as a fuel rather than being poisoned by it, and high grade exhaust heat for combined heat and power, or combined cycle gas turbine applications. This paper reviews the operating principle, materials for different cell and stack components, cell designs, and applications of SOFCs. Among all designs of Solid Oxide Fuel Cells (SOFCs), the most progress has been achieved with the tubular design. However, the electrical resistance of tubular SOFCs is high, and specific power output $(W/cm^2)$ and volumetric power density $(W/cm^3)$ low. Planar SOFCs, in contrast, are capable of achieving very high power densities.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.6
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• pp.821-828
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• 2000

Metal - ceramic restorations have been the standard of fixed oral rehabilitation for over 30 years, and while many advances have been made in materials and research, the esthetic challenges of the light reflective metal substructure will always put clinician in an esthetic dilemma, for only a very talented ceramist / dentist team can create esthetics that rival nature on a repeatable basis. All ceramic restorations have also been a choice in our restorative armamentarium, but in the past, the materials have also had their own limitation, number on being question-able strength to withstand occlusal forces generated during mastication. IPS Empress 2 offers dentistry a metal free alternative to traditional restorative techniques. This clinical report describes the treatment of patients with esthetic problem of anterior dentition using Empress 2 system.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.525-529
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• 2018

The antireflective (AR) coated poly methyl methacrylate (PMMA) substrate was deposited by atomic layer deposition (ALD) on a self-assembled monolayer (SAM) to improve hydrophobicity and mechano-chemical properties of organic thin films. The water contact angles (WCA) were tested to characterize the surface wettability of SAM octadecyltrichlorosilane (OTS) films. Results showed that a contact angle of $105.9^{\circ}$ was obtained for the SAM films with an annealing process, and the highest WCA of $120^{\circ}$ was achieved for the films prepared by the SAM and ALD multi-process. The surface morphology of the SAM films with different assembly times and varying number of ALD cycles was obtained by atomic force microscopy (AFM). The maximum light transmittance for the SAM films on the PMMA substrate reached 99.9% at a wavelength of 450 nm. It was found that the SAM surfaces were not affected at all by the ALD process.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.419-423
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• 2018

A newly conceived geopolymer composite was fabricated by a combination of the geopolymer and polyurethane sponge. The density and porosity of hardened geopolymer composite, corresponded to different pore sizes of polyurethane sponge, exhibited no significant differences from each other. However, the mechanical behavior, the compressive strength and flexural strength, showed slight differences accordingly. Fracture of the geopolymer composite exposed to high compressive load was not observed from all specimens containing polyurethane sponge. The toughness enhancement of the geopolymer composite, due to spontaneous elasticity of polyurethane sponge, crack spread, and crack diffraction, was identified through the stress-strain curve and microstructure of fracture surface. The newly designed geopolymer composite having a 3-dimensional sponge skeleton showed relatively higher flexural strength of 8.0 MPa than other conventional geopolymer composites.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.198-209
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• 1995

In order to evaluate the fitness and the degree of rounding of porcelain margins in collarless metal cermic restorations, collarless metal ceramic restorations were fabricated with shoulder margins of 90 and 120 degress, each consisting of ten specimens, on master dies through the direct lift technique. And ten metal ceramic restorations with a shoulder 90 degrees were fabricated. All specimens were embedded in resin and sectioned longitudinally. The sections were observed under a stereomicroscope and photographed(${\times}$200). The labial marginal gap between the die and the porcelain margin were measured with a scale. The space between the porcelain margin and the die, that is formed from marginal rounding and cementation were calculated with a computer coordinating area curvimeter. The following results were obtained. 1. There was no statistical difference between the fitness of porcelain margin of collarless metal ceramic restorations and marginal fitness of metal ceramic restoration. 2. There was no statistical difference between a shoulder of 90 and 120 degrees in the fitness of porcelain margin of collarless metal ceramic resorations. 3. Collarless metal ceramic restorations with a shoulder of 90 degrees and 120 degrees showed significantly more labial marginal rounding than metal ceramic restorations. 4. There was no statistical difference between a shoulder of 90 and 120 degrees in rounding of porcelain margin of collarless metal ceramic restorations. According to the results, rounding of porcelain margins can be observed in collarless metal ceramic restorations. Thus, there is a need for improvement in dental materials and techniques to minimize this problem, Furthermore, care should be exercised during the clinical procedure.