• Journal of the Korean Society of Industry Convergence
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• v.7 no.3
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• pp.259-263
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• 2004

In the manufacture progress of LCD or semiconductor, there are used many kinds of gas like erosion gas, dilution gas, toxic gas as a progress which used these gas there are required high puritize to increase accumulation rate of semiconductor or LCD materials work progress of semiconductor or LCD it demand many things like the material which could minimize metallic dust that could be occured by reaction between gas and transfer pipe laying material, illumination of the surface, emition of the gas, metal liquation, welding etc also demand quality geting stricted. Material-Low-sulfur-contend (0.007-0010), vacuum-arc-remelt(VAR), seamless, high-purity tubing material is recommend for enhance welding lower surface defect density All wetted stainless steel surface must be 316LSS elecrto polishinged with ${\leq}0.254{\mu}m$($10.0{\mu}in$) Ra average surface finish, $Cr/Fe{\geq}1.1$ and $Cr_2O_3$ thickness ${\geq}25{\AA}$ From the AES analytical the oxide layer thickness (23.5~36 angstroms silicon dioxide equivalent) and chromum to iron ratios is similar to those generally found on electropolished stainless steel., molybdenum and silicon contaminants ; elements characteristic of stainless steel (iron, nickel and chromium); and oxygen were found on the surface Phosphorus and nitrogen are common contaminants from the electropolish and passivation steps.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.462-469
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• 2012

Cr(VI)-4,4'-bipyridine complex(4,4'-bipyridinium dichromate) was synthesized by the reaction of 4,4'-bipyridine with chromium trioxide in H2O, and characterized by IR, ICP. The oxidation of benzyl alcohol using 4,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene$CH_3$, H, m-Br, m-$NO_2$) smoothly in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.63(303K). The observed experimental data have been rationalized as follows; the proton transfer occurs after the prior formation of a chromate ester in the rate determining step.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.648-653
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• 2014

Cr(VI)-heterocyclic complex (2,4'-bipyridinium chlorochromate) was synthesized by the reaction between heterocyclic compound(2,4'-bipyridine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium chlorochromate in various solvents showed that the reactivity increased with the increase of the dielectric constant (${\varepsilon}$), in the order : N,N-dimet-hylformamide (DMF) > acetone > chloroform > cyclohexene. In the presence of DMF solvent with acidic catalyst such as hydrochloric acid (HCl solution), 2,4'-bipyridinium chlorochromate oxidized benzyl alcohol (H) and its derivatives (p-$CH_3$, m-Br, m-$NO_2$). Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.67 (303 K). The observed experimental data have been rationalize the proton transfer occurred followed the formation of a chromate ester in the rate-determining step.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.590-596
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• 2002

The resin : metal interface is at the basis of most bonding failures in resin-bonded prosthesis. Although debonding has been a problem with adhesive fixed partial dentures, various dentists classify them as long-term restorations. The advantages of resin-bonded fixed partial dentures include minimal tooth reduction and the possibility of rebonding. if resin-bonded protheses can be easily rebounded, it is of clinical importance to know if the lutingagents rebond as well the second time as they did originally. Several retentive systems for resin-to-metal bonding have recommended. Treatments such as electrolytic etching and silicone coating, despite the good result of bond strength, have proved to be time-consuming and technique-sensitive. Therefore a simple and more reliable method is desirable. This study evaluated the effect of metal surface treatments on the rebond strength of panavia 21 cement to a nickel-chromium(Ni-Cr) alloy. The samples were received the following surface treatments : Group No.1 (control or served as the control) treatment with sandblasting with 50um aluminum oxide and ultrasonically cleaned for 10minutes in double-deionized water, Group No.2 were no surface treatments. Group No.3 were treated with metal primer. Group No.4 were treated with sandblasting as previously described, and then metal priming. From the analysis of the results, the following conclusions were drawn. 1. Sandblasting and metal priming appears to be an effective method for treatment of metal after accidental debonding. 2. Group without surface treatment had significantly lower bond strengths compared with other groups. 3. The combination of sandblasting and metal priming may not develop superior bonding strengths compared with other techniques that used the Ni-Cr alloys. 4. Combination of cohesive and adhesive failures were the most common type observed. The results support the use of sandblasting as a viable procedure when rebonding accidentally lost adhesive partial denture. We concluded that sandblasting and metal priming of metal surface before bonding could provide the adequate bond strength during rebonding of resin-bonded fixed partial denture.

• The Journal of Advanced Prosthodontics
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• v.15 no.2
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• pp.63-71
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• 2023

PURPOSE. The aim of this study was to assess the effect of hemispherical dimple structures on the retention of cobalt-chromium (Co-Cr) crowns cemented to titanium abutments, with different heights and numbers of dimples on the axial walls. MATERIALS AND METHODS. 3.0-mm and 6.0-mm abutments (N = 180) and Co-Cr crowns were prepared. The experimental groups were divided into two and four dimple groups. The crowns were cemented by TempBond and PANAVIA F 2.0 cements. The retention forces were measured after thermal treatments. A two-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test were conducted to analyze change in retention forces by use of dimples between groups, as well as t test for the effect of abutment height change (α = .05). RESULTS. Results of the two-way ANOVA showed a statistically significant difference in retention force due to the use of dimples, regardless of the types of cements used (P < .001). A significantly higher mean retention forces were observed in the groups with dimples than in the control group, using the post hoc Tukey HSD test (P < .001). Results of t test displayed a statistically significant increase in the retention force with 6.0-mm abutments compared with 3.0-mm abutments (P < .001). The groups without dimples revealed adhesive failure of cements, while the groups with dimples showed mixed failure of cements. CONCLUSION. Use of hemispherical dimples was effective for increasing retention forces of cemented crowns.

• The Journal of Advanced Prosthodontics
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• v.16 no.2
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• pp.91-104
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• 2024

PURPOSE. The objectives of the current study were to estimate the influence of self-reinforced hollow structures with a graded density on the dimensional accuracy, weight, and mechanical properties of Co-Cr objects printed with the direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS. Sixty-five dog-bone samples were manufactured to evaluate the dimensional accuracy of printing, weight, and tensile properties of DMLS printed Co-Cr. They were divided into Group 1 (control) (n = 5), Group 2, 3, and 4 with incorporated hollow structures based on (spherical, elliptical, and diamond) shapes; they were subdivided into subgroups (n = 5) according to the volumetric reduction (10%, 15%, 20% and 25%). Radiographic imaging and microscopic analysis of the fractographs were conducted to validate the created geometries; the dimensional accuracy, weight, yield tensile strength, and modulus of elasticity were calculated. The data were estimated by one-way ANOVA and Duncan's tests at P < .05. RESULTS. The accuracy test showed an insignificant difference in the x, y, z directions in all printed groups. The weight was significantly reduced proportionally to the reduced volume fraction. The yield strength and elastic modulus of the control group and Group 2 at 10% volume reduction were comparable and significantly higher than the other subgroups. CONCLUSION. The printing accuracy was not affected by the presence or type of the hollow geometry. The weight of Group 2 at 10% reduction was significantly lower than that of the control group. The yield strength and elastic modulus of the Group 2 at a 10% reduction showed means equivalent to the compact objects and were significantly higher than other subgroups.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.704-713
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• 2003

The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr-5Ni-3Mo duplex stainless steel(DSS) aging heat treated in a temperature range of 600~$1000^{\circ}C$ has been investigated. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSS had decreased, After aging for 2min at 700~$900^{\circ}C$, the pitting potential of the 3Mo steel decreased remarkably, while that of the W-substituted steel hardly changed. During aging. the intermetallic $\sigma$ and secondary austenite ($\gamma_2$) phases were precipitated. and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700~$750^{\circ}C$ for 10 h, which could be caused by the $\gamma_2$ formation. The ${\gamma}$$_2$ phase could affect the depletion of molybdenum and chromium in the $\gamma_2/\alpha and \gamma_2/\sigma$ boundaries.

• Nuclear Engineering and Technology
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• v.30 no.3
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• pp.262-272
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• 1998

The experiences and causes of pressure tube cracking accidents in the CANDU reactors and the development of the fuel channel at AECL(Atomic Energy Canada Limited) have been described. Most of the accidents were caused by Delayed Hydride Cracking(DHC). In the cases of the Pickering units 3&4 and the Bruce unit 2, excessive residual stresses induced by an improper rolled joint process played a role in DHC. In the Pickering unit 2, cracks formed by contact between the pressure and calandria tubes due to the movement of the garter spring were the direct cause of the failure. To extend the life of a fuel channel, several R&D programs examining each component of the fuel channel have been carried out in Canada. For a pressure tube, the main concern is focused on changing the fabrication processes, e.g., increasing cold working rate, conducting intermediate annealing and adding a third element like Fe, V, and Cr to the tube material. In addition to them, chromium plating on the end fitting and increasing wall thickness at both ends of the calandria tube are considered. There has also been much interest in the improvement of fuel channel performance in our country and several development programs are currently under way.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.514-520
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• 2000

The mechanism of corrosion behavior has to be understood clearly to select an optimum material for handling molten salts to be used in the oxide reduction process of PWR spent fuel. In this study, the oxidation states of corrosion products on the surface of Inconel 600 and 800H as well as their chemical compositions and structural informations were determined by using XPS, ICP-AES, AAS, EPMA and XRD after the corrosion experiment with lithium molten salts at 75$0^{\circ}C$ for 25 hours. Nickel and oxygen were detected from the corrosion products on the surface of Inconel plates and chromium was found to be dissolved out into lithium molten salts leaving cracks on the surface. The corrosion products were identified as metal oxides such as Fe$_2$O$_3$, Cr$_2$O$_3$, NiO, NiFe$_2$O$_4$and MnO by using XPS and XRD.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.717-729
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• 1999

Although many studies on the cytotoxicity of the dental cast base metal alloys and their components have been carried out, the results are rather conflicting because of the different type of cells used and the various experimental procedures taken. Recently a number of scientists have claimed that it would be preferable to focus on the use of cells from relevant specific location of the human bodies. Consequently, the primary cultured oral keratinocyte derived from oral mucous along with nickel chloride and several of widely used dental cast base metal alloys(two Ni-Cr alloys and one Co-Cr alloy)in domestic were selected for this study, from which 1) The amounts of released metal ions were determined using atomic absorption spectrometry, 2) The cytotoxicity of nickel chloride and dental cast base metal alloys was evaluated via MTT assay, and finally, 3) The amounts of released metal ions and the cytotoxicity of nickel chloride were correlated with the cytotoxicity of dental cast base metal alloys And, the results were summarized as follows; 1. Nickel ion from Ni-Cr alloys and Cobalt ion from Co-Cr alloys resulted in maximum releasing rate during first 2h hours, followed by a decrease in releasing rate with time. Chromium ion were found to be minimal in all alloys. 2. In cytotoxic test. with $40{\mu}M,\;80{\mu}M$ of nickel chloride, there were observed an increase in the relative cell number compared to control samples after 24 hours. With $160{\mu}M$, there was found to be no difference in the relative cell number with control, except that 48 hour showed a increase in relative cell number. With $320{\mu}M$, the relative cell number remained constant and decreased after 48 hours, and with $640{\mu}M$, a continuing decrease in relative cell number was observed throughout test period. 3 The sensitivity of primary cultured oral epithelium to nickel was lower compared to the cells used in other studies. 4. CB-80 Soft and Regalloy showed no cytotoxicity to primary cultured oral epithelium and New crown resulted in a slight cytotoxicity. In conclusion, it was shown that the primary cultured oral keratinocytes could be applied successfully as testing cells in cytotoxicity test. Futhermore, the dental cast base metal alloys used in this study were found to be biocompatible.