• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.171-179
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• 2001

The purpose of this study was to evaluate the shear bond strength of compomers according to dentin surface treatment. Two materials of compomer were devided into six groups. The compomer used in this study were Dyract AP(D) and F2000(F), Group 1 (DN) and 4(FN) were treated according to manufacturers instructions as control groups. Group 2(DE) and 5(FE) were treated with 37％ phosphoric acid and group 3(DA) and 6(FA) were treated with air abrasion unit (80 psi, 50 m aluminum oxide particles) respectively as experimental groups. After dentin surface treatment, compomers were bonded. Completed samples were stored in 100％ humidity. 37C during 7 days, and then, the shear bond strength of specimens were evaluated. The results were as follows: 1. In the case of Dyract AP, the shear bond strength was showed the highest value of 9.10 MPa in dentin surface treatment with air abrasion unit. but there were no significant differences to the other groups. 2. In the case of F2000. the shear bond strength was showed the highest value of 13.51MPa and there were significant differences to the other groups(p<0.05). 3. The shear bond strength of F2000 was higher than Dyract AP in each dentin surface treatment. and in the case of etching and air abrasion. there were significant differences(p<0.05). 4. As a result of observation of SEM. the most of fracture pattern was adhesive failure in group 1(DN), 2(DE) and 4(FN), and cohesive failure in group 3(DA), S(FE) and 6(FA).

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2918-2922
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• 2010

We demonstrate a facile route to synthesize silver chloride nanocubes and derivative nanomaterials. For the synthesis of silver chloride nanocubes, silver nitrate and hydrochloric acid were used as precursors in ethylene glycol, and poly (vinyl pyrrolidone) as a surfactant. Molar ratio of the two precursors greatly influenced the morphology and composition of the final products. As-synthesized silver chloride nanocubes showed size-dependent optical properties in the visible region of light, which is likely due to a small amount of silver clusters formed on the surface of silver chloride nanocubes. Moreover, we show for the first time that simple reduction of silver chloride nanocubes with different reducing reagents leads to the formation of delicate nanostructures such as cube-shaped silver-nanoparticle aggregates, and silver chloride nanocubes with truncated corners and with silver-nanograin decorated corners. Additionally, we quantitatively investigated for the first time the evolution of silver chloride nanocubes to silver chloride nanocubes decorated with silver nanoparticles upon exposure to e-beam. Our novel and facile synthesis of silver chloride related nanoparticles with delicately controlled morphologies could be an important basis for fabricating efficient photocatalysts and antibacterial materials.

• Carbon letters
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• v.3 no.3
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• pp.127-132
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• 2002

Unidirectional polymer composites were prepared using high-strength carbon fibers as reinforcement and phenolic resin as matrix precursor with keeping fiber volume fraction at 30, 40, 50 and 60% respectively. These composites were carbonized at $1000^{\circ}C$ and graphitised at $2600^{\circ}C$ in the inert atmosphere. The carbonized and graphitised composites were characterized for mechanical properties as well as microstructure. Microscopic studies were carried out of the polished surface of carbonized and graphitised composites after etching by chromic acid, to understand the effect of fiber volume fraction on oxidation at fiber-matrix interface. It is found that the flexural strength in polymer composites increases with fiber volume fraction and so does for the carbonised composites. However, the trend was found to be reversed in graphitised composites. In all the carbonized composites anisotropic region has been observed at fiber-matrix interface which transforms into columnar type microstructure upon graphitisation. The extension of strong and weak columnar type microstructure is function of fiber volume fraction. SEM microscopy of the etched surface of the sample reveal that composites containing 40% fiber volume has minimum oxidation at the interface, revealing a strong interfacial bonding.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1971-1973
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• 2005

We fabricated an alumina membrane with nano-sized pore array by anodic oxidation using the thin film aluminum deposited on silicon wafer. It is important that the sample prepared by metal deposition method has a flat aluminum surface and a good adhesion between the silicon wafer and the thin film aluminum. The oxidation time was controlled by observation of current variation. The nano-sized pores with diameter of $60{\sim}120nm$ was obtained by $40{\sim}80$ voltage. The pore widening process was employed for obtaining the flat surface because the pores of the alumina membrane prepared by the fixed voltage method shows the structure of rough surface. Finally, the sample was immersed to the phosphoric acid with 0.1M concentration to etching the barrier layer. The sample will be applied to electronic sensors, field emission display, and template for nano- structure.

• Journal of Sensor Science and Technology
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• v.14 no.5
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• pp.337-342
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• 2005

A silicon-based micro-reactor to amplify small amount of deoxyribonucleic acid (DNA) has been fabricated using micro-electro-mechanical systems (MEMS) technology. Polymerase chain reaction (PCR) of DNA requires a precise and rapid temperature control. A Pt sensor is integrated directly in the chamber for real-time temperature measurement and an infrared lamp is used as external heating source for non-contact and rapid heating. In addition to the real-time temperature sensing, PCR needs a rapid thermocycling for effective PCR. For a fast thermal response, the thermal mass of the reactor chamber is minimized by removal of bulk silicon volume around the reactor using double-side KOH etching. The transparent optical property of silicon in the infrared wavelength range provides an efficient absorption of thermal energy into the reacting sample without being absorbed by silicon reactor chamber. It is confirmed that the fabricated micro-reactor could be heated up in less than 30 sec to the denaturation temperature by the external infrared lamp and cooled down in 30 sec to the annealing temperature by passive cooling.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.28-31
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• 2003

Copper CMP in terms of the effect of slurry chemicals (oxidizer, corrosion inhibitor, complexing agent) on the process characteristics has been performed. Corrosion inhibitors, benzotriazole (BTA) and tolytriazol (TTA) were used to control the removal rate and avoid isotropic etching. When complexing agent is added with H$_2$O$_2$ 2 wt% in the slurry, the corrosion rate was presented very well. In the case of complexing agent, it was estimated that the proper concentration is 1 wt%, because the addition of tartaric acid to alumina slurry causes low pH and the slurry dispersion stability become unstable. There was not much change of the removal rate. It was assumed that BTA 0.05 wt% is suitable. Most of all, it was appeared that BTA is possible to be replaced by TTA. TTA was distinguished for the effect among complexing agents.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.101-108
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• 1987

The purpose of this study was to investigate the pulpal responses of dental adhesive resins. A total of 40 cavities of the permanent healthy teeth from 4 dogs were prepared. In the experimental group, the cavities were etched for 1 minute with citric acid and filled with experimental resins (ie. Super-Bond C & B$^{(R)}$). In the control group, the cavities were filled with calcium hydroxide base materials (ie. Dycal$^{(R)}$) without etching. The dogs were sacrificed at one, two, three and four weeks after the time of filling and the specimens were routinely prepared and stained with Hematoxylin-Eosin. The microscopic findings were as follows: Infiltration of inflammatory cells was not observed in both experimental and control groups. Change in the odontoblastic layer was not observed in all control groups but severe swelling was observed in deep dental pulp tissue of the control two and three week cases. Pulp tissue was recovered with plenty of fibrous component in the control four week case and reparative dentin formation was not occurred in all cases. Slight changes of the odontoblastic layer beneath the cavity were observed in the experimental one week case. In experimental two and three week cases, swelling of deep pulp tissue was increased and localized reparative dentin formation was observed. In the experimental four week case, odontoblastic layer was recovered with regular appearance and fibrous component of the pulp was increased, but reparative dentin formation was not evident.

• Restorative Dentistry and Endodontics
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• v.21 no.2
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• pp.635-641
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• 1996

This study was designed to evaluate the anti cariogenic effect of F in primers, bonding agents, composite resins or glass ionomer cements in enamel. Twenty-five extracted teeth were selected and a cavity was prepared on either the buccal or the lingual surface of each tooth. After pumicing and etching, the samples were divided into 5 groups. In group A, the samples were primed, bonded and filled with ART bond and Brilliant Enamel (Coltene, Switzerland). Group B composed of Optibond and Herculited XRV (Kerr, USA), group C composed of Syntac and Tetric(Vivadent, Lichtenstein), and group D composed of Scotch-bond Multipurpose and Z 100 (3M, YSA). In group E, the samples were filled with glass ionomer cement (Fuji II LC, Japan), All surfaces except the 2mm beyond the cavosurface margin of the sample were protected, and samples were then put into an acid buffer for 3 days to develop the initial caries. The samples were then sectioned through the filling body into thin wafers and then examined with a polarizing microscope under water imbibition. The fluoride in primer, bonding agent, or composite filling material did not prevent the initial caries in the enamel area adjacent to the filling body whereas the fluoride in the glass ionomer did prevent the initial stage caries.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.50-53
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• 2023

In this study, the photolithography process was chosen to reduce the aspect ratio of the cross-section of a high-temperature superconducting (HTS) tape by dividing the superconducting layer of the tape. Reducing the aspect ratio decreases the magnetization losses in the second-generation HTS tapes generated by AC magnetic fields. The HTS tape used in the experiment has a thin silver (Ag) layer of about 2 ㎛ on top of the REBCO superconducting layer and no additional stabilizer layer. A dry film resist (DFR) was laminated on top of the HTS tape by a lamination method for the segmentation. Exposure to a 395 nm UV lamp on a patterned mask cures the DFR. Dipping with a 1% Na₂CO₃ solution was followed to develop the uncured film side and to obtain the required pattern. The silver and superconducting layers of the REBCO films were cleaned with an acid solution after the etching. Finally, the segmented HTS tape was completed by stripping the DFR film with acetone.

• Journal of Integrative Natural Science
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• v.17 no.3
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• pp.67-73
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• 2024

Hydrophilic contact lens was prepared by dispersing MXene material in a hydrogel mixture, and the purpose of this study was to evaluate its properties as an ophthalmic material. The MXene used in the experiment was manufactured through an etching process using titanium aluminum carbide 312 [Ti3AlC2] and hydrofluoric acid [HF]. For the preparation of hydrophilic contact lenses, 2-hydroxyethyl methacrylate [HEMA], a photoinitiator 2-hydroxy-2-methylpropiophenone [2H2M], and a cross-linker Ethylene glycol dimethacrylate [EGDMA] were used, and UV-rays was irradiated for 50 seconds for photopolymerization. Optical transmittance, refractive index, water content, contact angle, electromagnetic wave shielding ability, and photo-thermal conversion effect were measured to evaluate the physical properties of the manufactured contact lens. Compared to MXene materials, MXene mixed with Dimethyl sulfoxide [DMSO] had superior dispersion ability in organic solvents, and the transparency of the prepared hydrophilic contact lenses was high. MXene did not significantly affect the refractive index and water content, and improved the wettability of the contact lens. In addition, the MXene material used as an additive showed electromagnetic wave shielding ability and photo-thermal conversion effect based on its excellent electrical conductivity. It is judged that the mixture using MXene as an additive can be used as a functional contact lens material for electromagnetic wave shielding and ocular photo-thermal therapy.