• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.504-508
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• 1998

Experimental investigation on the adsorption of heavy metal confounds as $Fe^{2+}$, $Cu^{2+}$, $Mn^{2+}$, $Zn^{2+}$, $Ni^{2+}$, $Pb^{2+}$, $Cd^{2+}$, $Cr^{6+}$ using chitosan was carried out. The adsorption of each component of heavy metal compounds was measured by Atomic Absorption apparatus. The range of optimum pH for the removal rates of heavy metal compounds was found pH 7.0~9.0. The maximum time for the removal rate of $Fe^{2+}$ was observed about 15 min. The maximum time for the removal raters of $Cu^{2+}$, $Mn^{2+}$, $Zn^{2+}$, $Ni^{2+}$, $Pb^{2+}$, $Cd^{2+}$, and $Cr^{6+}$ was observed about 25 min. The adsorption rates of heavy metal compounds by chitosan have been found in the order of $Fe^{2+}>Cu^{2+}>Mn^{2+}>Zn^{2+}>Ni^{2+}>Pb^{2+}>Cd^{2+}>Cr^{6+}$.

• Journal of Technologic Dentistry
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• v.38 no.2
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• pp.69-77
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• 2016

Purpose: This study was to evaluate the shear bond strength of ceramic fused to Ni-Cr alloy(Alophaloy) by heat treatment. Methods: The specimens were divided into 5 groups according to heat treatment conditions prior to porcelain application. Eighteen specimens from each group were subjected to the shear load a universal testing machine using a 0.1mm/min cross-head speed and two specimens from each group were observed with SEM and EDX line profile. Results: The observation of the oxide film on the metal surface by SEM photograph showed a coarsening with an increasing degassing hold time. The diffusion of metal oxide was observed farther from the opaque layer in the heat treated specimen than no heat treated specimen. The shear bond strength measured highest to A5(55.23MPa) in the 10min holding group and measured lowest from A1(24.38MPa) in the no heat treated group, and there was a significant difference(p<0.05). Conclusion: The shear bond strength of Ni-Cr alloy improved in the heat treatment compared to the no heat treatment specimen.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.211-215
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• 2014

The Pt-, Ni- and Cr-decorated tubular $SnO_2$ nanofibers for gas sensors were prepared by the electrospinning of polyvinylpyrrolidone (PVP) nanofibers containing Pt, Ni, and Cr precursors, the sputtering of $SnO_2$ on the electrospun PVP nanofibers, and the removal of sacrificial PVP parts by heat treatment at $600^{\circ}C$ for 2 h. Pt-decorated tubular $SnO_2$ nanofibers showed high response ($R_a/R_g=210.5$, $R_g$: resistance in gas, $R_a$: resistance in air) to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ with negligible cross-responses to other interference gases (5 ppm trimethylamine, $NH_3$, HCHO, p-xylene, toluene and benzene). Cr-decorated tubular $SnO_2$nanofibers showed the selective detection of p-xylene at $400^{\circ}C$. In contrast, no significant selectivity to a specific gas was found in Ni-decorated tubular $SnO_2$ nanofibers. The selective and sensitive detection of gases using Pt-decorated and Cr-decorated tubular $SnO_2$ nanofibers were discussed in relation to the catalytic promotion of gas sensing reaction.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.931-932
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• 2006

The microstructures of Ni-containing P/M steels produced by admixed powders or diffusion alloyed powders are usually heterogeneous. To improve the microstructure homogeneity, the effects of Mo and Cr additions in the prealloyed powder form were examined. The results showed that the microstructural homogeneity was improved and superior mechanical properties were achieved with increases in the alloy content, particularly for the Cr. Such a beneficial effect was attained due to the reduction of the repelling effect between Ni and C, as was demonstrated through thermodynamic analysis using the Thermo-Calc software.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.3
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• pp.185-189
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• 1999

Effects of alloy modification with the $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy for an electrode use have been investigated. For the alloy composition, a part of Mn was substituted by Co, Cr and Fe. The experimental results showed that Co accelerated activation of alloy, and Fe and Cr improved the discharge capacity. These results agree with P-C-T curves of each alloy. But substituting Fe for Mn showed the decrease of the discharge capacity when discharged at high rate (60mA, about 1C rate). Considering both the discharge capacity and the high rate discharge property, $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$ alloy was found to be the best alloy among the alloys subjected to the test.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.264-271
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• 2017

Purpose: The purpose of this study is to investigate the differences in bond strength of four different indirect composites to the gold alloy and Ni-Cr alloy according to type of metal surface treatment after water storage. Materials and methods: Type IV gold alloy and Ni-Cr alloy were used for casting alloy while four types of indirect composite resins (Gradia, Tescera Sinfony and in;joy) were used in this study. Metal specimens were produced by casting and total of 240 specimens (60 specimens per one indirect composite group) were prepared. After bonding indirect composite resin and undergoing 24 hours of polymerization, customized jig was attached to the metal specimen and shear bond strength were measured using universal testing machine. Also, differences in shear bond strength before and after water storage for 240 hours were also measured. Results: In the measurement of shear bond strength according to the metal surface treatments, bead group showed high strength followed by loop and flatting group (P<.05). After being stored in water bath for 240 hours, Gradia showed statistically significant high bond strength compared to other indirect composite resins in all groups (P<.05). Conclusion: Shearbond strength was found to be different according to type of metal surface treatment and type of metal used after storage in water. Further studies need to be developed for clinical practices as three are still problems of microleakage, stain or wear.

• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.271-281
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• 2001

The Purpose of this study was fourfold - to evaluate the general laws of friction applied to orthodontic conditions, to compare archwire materials under these controlled conditions, to compare ligation method, and to measure the effect of the artificial saliva on friction with these materials Three wire alloys (Cobalt-chromium, Nickel-titanium, Beta-titanium) in two size wires (.016" , .016" ${\times}$.022" ) were examined respect to the bracket (.018" ${\times}$.025" standard), and two ligature material (stainless steel, elastomeric) in dry and wet conditions The results were as follows, 1. The order of frictional force against alloy materials was Co-Cr (lowest), Ni-Ti, and ${\beta}$-Ti(highest) - with the exception of elastomeric ligation under wet conditions. 2. S.S. ligation gave rise to significantly greater friction than elastomeric ligation did. 3. Testing in the presence of saliva, rather than in dry conditions, decreased the frictional force for S.S. ligation with .016" Co-Cr, Ni-Ti, ${\beta}$-Ti. but, increased the frictional force for S.S. ligation with .016" ${\times}$ .022" Co-Cr, Ni-Ti, ${\beta}$-Ti. 4. .016" ${\times}$.022 " wire generated more friction than .016" wire.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.63-74
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• 2009

Partial or complete prosthesis is needed when teeth are lost due to various kinds of reason. Artificial teeth recover occlusion instead of natural teeth. Artificial teeth are required of esthetics, fragile resistance and abrasive resistance. Artificial tooth is made of acrylic resin or porcelain. Nowadays, acrylic resin artificial teeth are mainly used. Acrylic resin teeth are occluded with natural teeth, gold alloy, Ni-Cr alloy or porcelain etc. Acrylic resin teeth have similar translucency, gloss of natural teeth. And it has good chemical bond with denture base material, but it has low wear resistance. The aim of this study is to compare wear resistance among several denture teeth(Endura, SR-orthosit-PE, Planustar) and between artificial resin denture teeth and opposing 3 restorative materials(gold, Ni-Cr alloy, porcelain). Wear tests were conducted with a rotating wear testing apparatus(pin-on-disk type wear tester) under conditions of rpm 180, 75 minutes and constant loading of 50N. The upper part was the cusp of maxillary first molar and the lower part was a disk type restorative materials. To make similar oral environment, water was supplied continually. The acrylic resin teeth wear was determined by weighing the cusp each 5 minutes during 75 minutes test. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows: 1. Wear rates of acrylic resin teeth opposing to the restorative materials were high in order of Porcelain, Gold, Ni-Cr alloy (p<.05). 2. Wear resistance rate opposing to the Porcelain disk, was shown in order of Endura, SR-orthosit-PE, Planustar. The wear rate of opposing to porcelain disk was above two times more than that of other groups (p<.05). 3. Wear resistance rates opposing to the Gold, Ni-Cr alloy disk, was shown in order of Endura, SR-orthosit-PE, Planustar (p<.05). 4. A degree of the surface hardness is directly proportional to the degree of wear resistance. There are statistically significant differences between each groups (p<.05).

• Journal of the Korean institute of surface engineering
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• v.40 no.3
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• pp.131-137
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• 2007

The typical MCFC (molten carbonate fuel cell) anode is made of Ni-10%Cr alloy. The work of this paper is focused concerning long life of anode because Ni-10% Cr anode is suffering from sintering and creep behavior during cell operation. Therefore, Ni-coated Alumina powder($20{\mu}m$) was developed by electroless nickel plating. Optimum condition of electroless nickel coation on $20{\mu}m$ alumina is as follows: pH 11.7, temperature $65{\sim}80^{\circ}C$, powder amount $100cm^2/l$. The deposition rate for Ni-electroless plating was as a function of temperature and activation energy was evaluated by Arrhenius Equation thereby activation energy calculated slope of experimental data as 117.6 kJ/mol, frequency factor(A) was $6.28{\times}10^{18}hr^{-1}$, respectively.

• Journal of the Korean institute of surface engineering
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• v.30 no.2
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• pp.93-103
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• 1997

High temperature materials used in the elevated temperature and corrosive atmosphere must have the good oxidation resistance and preserve their own mechanical properties simultaneously. For the oxidation resistance, it is very important to form a protective oxide scale such as $Al_2O_3$ or $Cr_2O_3$ on the substrate. However, the additions of protective oxide forming elements such as Cr and Al in the alloy to enhance its oxidation resistance are limited due to the deleterious effects on their mechanical properties. PECVD(P1asma Enhanced Chemical Vapor Deposition) coating processes were employed to improve the oxidation resistance at high temperature. Cr and/or A1 were coated on the substrates of Ni and Inconel 600 at various temperatures of 400, 500, $600^{\circ}C$ and at different conditions of specimen surfaces. Then, coated specimens were exposed to isothermal and cyclic oxidation conditions in air at 1000 and $1100^{\circ}C$. In order to enhance the adhesion between the substrate and coated layer, heat treatments of the coated specimens were conducted in a vacuum. At isothermal oxidation experiments, Al-coated Ni specimen showed better oxidation resistance than pure Ni. At cyclic oxidation experiments at $1000^{\circ}C$. Cr and Al-coated specimen showed better oxidation resistance. Cr-coated Inconel 600 had also showed better oxidation resistance due to Cr in the substrate. By PECVD coating process, oxidation resistance could be improved, but it was not improved as expected due to the weakness of the adhesion between the substrate and the coated layer.