• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.403-411
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• 2001

The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Unifil(GC, Japan), Palfique(Tokuyama Japan). Definite$Degussa-H\ddot{u}ls$ AG, Germany). Revolution(Kerr, U.S.A.). Preweighed discs of each brand were exposed 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters: (a) mass loss(%) - determined from pre-and post-exposed specimen weights; (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth$({\mu}m)$ - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were follows: 1. The mass loss of Unifil was 3.21%, it was the highest of materials. But, there was no significant difference among the materials. 2. The degree of degradation layer depth was $107.69\sim47.40{\mu}m$, the sequence of the degree pf degradation layer depth was in descending order by Unifil, Palfique, Revolution, Definite. There was significant difference among the materials except Palfique and Definite. 3. The Si loss of Paltique was 8940.0ppm, it was the highest. There was significant difference among the materials, except Revolution and Definite(p<0.05). 4. The correlation coefficient between mass loss and degradation depth was relatively high(r = 0.06, p<0.05). 5. There was no significant coefficient correlation between Si loss and mass loss, and/or the degree of degradation layer depth and Si loss. 6. When observed with SEM, destruction of bonding is observed between resin matrix and filler. Above results suggested that the hydrolytic degradation is considered as evaluation factor of composite resins.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1078-1083
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• 2002

Ceramics are significantly used in many industrial applications due to their excellent mechanical and thermal properties such as high temperature strength, low density, high hardness, low thermal expansion, and good corrosion resistive properties, while their disadvantages are brittleness, poor formability and high manufacturing cost. To combine advantages of ceramics with those of metals, they are often used together as one composite component, which necessiates reliable joining methods between metal and ceramic. Direct brazing using an active filler metal has been found to be a reliable and simple technique, producing strong and reliable joints. In this study, the fracture characteristics of Si$_3$N$_4$ ceramic joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu (0.25-0.3 mm) interlayer are investigated as a function of strain rate and temperature. In order to evaluate a local strain a couple of strain gages are pasted at the ceramic and metal sides near joint interface. As a result the 4-point bending strength and the deflection of interlayer increased at room temperature with increasing strain rate. However bending strength decreased with temperature while deflection of interlayer was almost same. The fracture shapes were classified into three groups ; cracks grow into the metal-brazing filler line, the ceramic-brazing filler line or the ceramic inside.

• Advances in nano research
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• v.10 no.3
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• pp.295-312
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• 2021

A new ionic liquid functionalized magnetic silica nanoparticle was synthesized and characterized and tested as an adsorbent. The adsorbent was used for magnetic solid phase extraction on ICP-MS method. Simultaneous determination of precious metal Au has been addressed. The method is simple and fast and has been applied to standard water and surface water analysis. A new method for separation/analysis of trace precious metal Au by Magnetron Solid Phase Extraction (MSPE) combined with ICP-MS. The element to be tested is rapidly adsorbed on CoFe2O4@SiO2@[BMIM]PF6 composite nano-adsorbent and eluted with thiourea. The method has a preconcentration factor of 9.5-fold. This method has been successfully applied to the determination of gold in actual water samples. Hydrophobic Ionic Liquids (ILs) 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6) coated CoFe2O4@SiO2 nanoparticles with core-shell structure to prepare magnetic solid phase extraction agent (CoFe2O4@SiO2@ILs) and establish a new method of MSPE coupled with inductively coupled plasma mass spectrometry for separation/analysis of trace gold. The results showed that trace gold was adsorbed rapidly by CoFe2O4@SiO2@[BMIM]PF6 and eluanted by thiourea. Under the optimal conditions, preconcentration factor of the proposed method was 9.5-fold. The linear range, detection limit, correlation coefficient (R) and relative standard deviation (RSD) were found to be 0.01~1000.00 ng·mL-1, 0.001 ng·mL-1, 0.9990 and 3.4% (n = 11, c = 4.5 ng·mL-1). The CoFe2O4@SiO2 nanoparticles could be used repeatedly for 8 times. This proposed method has been successfully applied to the determination of trace gold in water samples.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.60-65
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• 2008

This study aims at investigating the wear properties of thermally sprayed $Al/Al_2O_3$ metal matrix composite(MMC) coating against different counterparts. $Al/Al_2O_3$ MMC coatings were fabricated using a flame spray system on an Al 6061 substrate. Dry sliding wear tests were performed using the sliding speeds of 0.2m/s and the applied loads of 1 and 2 N. AISI 52100, $Al_2O_3$, $Si_3N_4\;and\;ZrO_2$ balls(diameter: 8mm) were used as counterpart materials. Wear properties of $Al/Al_2O_3$ MMC coatings were analyzed using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear properties of $Al/Al_2O_3$ composite coatings were much influenced by counterpart materials. In the case of AISI 52100 used as counterparts, the wear rate of composites coating layer increased according to the increase of the applied load. On the contrary, in the case of ceramics used as counterparts, the wear rate of composites coating layer decreased according to the increase of the applied load.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.273-284
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• 2007

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four esthetic restorative materials in an alkaline solution(0.1N NaOH). The composite resins studied were Composan LCM flow(Promedica, Germany). Clearfil ST(Kuraray medical, Japan), Durafi VS1(Heraeus Kulzer, U.S.A), Point 4(Kerr, U.S.A). The results were as follows : 1. The mass loss of each brand was $1.02{\sim}6.04%$ and highest value in Durafil VS$(6.04{\pm}0.29%)$. 2. The sequence of the degree of degradation layer depth was in descending order by Durafil VS, Clearfil ST, Point 4 and Composan LCM flow. There were significant differences between Point 4, Composan LCM flow and the others (p<0.001). 3. The sequence of the Si loss was in descending order by Clearfil ST, Durafil VS, Composan LCM flow and Point 4. There were significant differences among the materials (p<0.001). 4. On SEM, destruction of bonding between matrix and filler and on CLSM, the depth of degradation layer of specimen surface was observed. 5. The sequence of maximum wear depth was in descending order by Durafil VS, Composan LCM flow, Point 4 and Clearfil ST. There were no significant differences among the materials (p>0.001) 6. The correlation coefficient between Si loss and degradation layer depth (r=0.892, p<0.01) and Si loss and mass loss(r=0.736, p<0.01) were relatively high. These results indicate that hydrolytic degradation, wear and another factor may consider as evaluation factors of composite resins.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.673-682
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• 2001

The use of resin composites has continued to increase over the last several years. In spite of their growing popularity, composites continue to exhibit a number of undesirable characteristics. One of the major deficiencies of composite restorative resins is their inadequate resistance to wear. Of the multitude of factors that have been associated with wear, subsurface degradation within the restoration is considered to be one. The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. This solution with a high concentration of hydroxyl ions is a convenient medium for accelerated degradation of silane coupling and filler particles. The brands studies were Definite($Degussa-H\ddot{u}ls$ AG, Germany), Prodigy(Kerr, USA), Pyramid(Bisco, USA) and Synergy(Coltene, Swiss). Preweighed discs of each brand were exposed to 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters : (a) mass loss(%)-determined from pre-and post-exposed specimen weights : (b) Si loss(ppm)-obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation $depth({\mu}m)$-measured microscopically (SEM) from polished circular sections of exposed specimens. The results were follows: 1. Mass loss of Synergy was $1.24{\pm}0.002%$, it was the highest, there was no significant difference among the materials. 2. The degree of degradation layer depth of Synergy was $107.83{\pm}2.52{\mu}m$, it was the highest, there was no significant difference among any other materials than Synergy. 3. There was no difference among the four materials in Si loss. 4. The correlation coefficient between mass loss and degradation depth was relatively high(r=0.06, p<0.05). 5. There was no coefficient correlation between Si loss and mass loss, the degree of degradation layer depth and Si loss. 6. When observed with SEM, destruction of bonding is observed between resin matrix and filler.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.685-695
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• 2004

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four composite resins in an alkaline solution. The resistance to degradation was evaluated on the basis of mass loss(%), degradation depth(${\mu}m$), Si loss(ppm) and wear depth. The brands studied were Heliomolar flow, Filtek supreme, Point4, Tetric flow. The results were as follows: 1. The sequence of the mass loss was in descending order by Heliomolar flow, Filtek supreme, Point4, Tetric flow. There was significant differences among the materials except Heliomolar flow and Filtek supreme. 2. The sequence of the degree of degradation layer depth was in descending order by Filtek supreme, Heliomolar flow, Tetric flow, Point4. There were significant differences among the materials except Heliomolar flow and Tetric flow. 3. The sequence of Si loss was in descending order by Filtek supreme, Heliomolar flow, Point4, Tetric flow. There were significant differences among the materials except Point 4 and Tetric flow. 4. The sequence of maximum wear depth was in descending order by Heliomolar flow, Point4, Fillet supreme, Tetric flow and there was increasing wear depth on soaking in 0.1N NaOH solution. 5. When observed with SEM, destruction of bonding between matrix and filler was observed and when observed with CLSM, the depth of degradation layer of specimen surface was observed. There results indicate that wear and hydrolytic degradation could be considered to be evaluation factors of composite resins.

• Journal of environmental and Sanitary engineering
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• v.13 no.2
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• pp.147-155
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• 1998

In this study, we prepared non-porous plasma membrane for having high permeability and selectivity and this membrane was deposited on the $Al_{2}O_{3}$ membrane by using $CHF_{3}$ & $SiH_{4}$ monomer. Also, we investigated for the permeation characteristics of the plasma polymer membrane by Ar plasma treatment. When the position of substrate was near cathode, the selectivity was increased with Ar plasma treatment time and rf-power. The pore size of $Al_{2}O_{3}$ membrane had an effect on the permeability and the position of substrate affected selectivity.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.530-539
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• 2003

The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Charisma, Filtek P 60, Palpique Estelite, and Spectrum. Preweighed discs of each brand were exposed to 0.1N NaOH solution at $60^{\circ}C$. After 2 weeks they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters: (a) mass loss(%) - determined from pre-and post-exposed specimen weights; (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth(${\mu}m$) - measured SEM and CLSM from polished circular sections of exposed specimens. The results were as follows: 1. The sequence of mass loss was in descending order by Palpique Estelite, Filtek P 60, Charisma, and Spectrum. 2. The sequence of the degree of degradation layer depth was in descending order by Filtek P 60, Charisma, Palpique Estelita, and Spectrum. 3. The sequence of the Si loss was in descending order by Chrisma, Spectrum, Palpique Estelite, and Filtek P 60. 4. The correlation coefficient between mass loss and degradation layer depth was relatively high(r=0.704, p<0.05). 5. When observed with SEM, destruction of bonding was observed between resin matrix and filler. 6. When observed with CLSM, degradation layer depth of composite resin surface was observed.