• Corrosion Science and Technology
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• 제2권3호
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• pp.141-147
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• 2003

Sputter-deposited Nb-Al-Cr alloys. $3-5{\mu}m$ thick, have been prepared on quartz substrates as oxidation-and sulfidation-resistant materials at high temperatures. The oxidation or the alloys in the $Ar-O_2$ atmosphere of an oxygen partial pressure of 20 kPa follows approximately the parabolic rate law, thus being diffusion controlled. Their oxidation rates are almost the same as or even lower than those ofthc typical chromia-forming alloys. The multi-lavered oxide scales are formed on the ternary alloys. The outermost layer is composed of $Cr_2O_3$, which is"mainly responsible for the high oxidation'resistance of these alloys. In contrast to sputter-deposited Cr-Nb binary alloys reported previously, the inner layer is not porous. TEM observation as well as EDX analysis indicates that the innermost layer is a mixture of $Al_2O_3$ and niobium oxide. The dispersion of $Al_2O_3$ in niobium oxide may be attributable to the prevention of the formation of the porous oxide layer. The sulfidation rates of the present ternary alloys arc higher than those of the sputter-deposited Nb-AI binary alloys, but still several orders of magnitude lower than those of conventional high temperature alloys. Two-layered sulfide scales are formed, consisting of an outer $Al_2S_3$ layer containing chromium and an inner layer composed of $NbS_2$ and a small amount of $Cr_2S_3$. The presence of $Cr_2S_3$ in the inner protective $NbS_2$ layer may be attributed to the increase in the sulfidation rates.

• 대한치과교정학회지
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• 제33권5호
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• pp.351-358
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• 2003

니켈과 크롬은 대부분의 교정장치를 제작하는데 사용되는 합금을 구성하는 주요한 금속이다. 그러나 이들 금속은 과민반응, 피부염, 천식 등의 주요한 원인이 되며, 이들 금속의 우발적인 흡입에 의해 암이 유발될 수 있음이 보고된 바 있다 이에 하악 standard edgewise브라켓을 이용한 사분악의 교정장치를 $37^{\circ}C,\;,0.05\%$ NaCl용액에 저장하여 교정장치의 부식에 의해 유리된 니켈과 크롬을 Inductively Coupled Plasma(ICP) spectroanalyzer를 이용하여 측정하였다. 교정장치로부터, 1일 평균 $9.83-70.0{\mu}g/day$의 니켈이 유리되었으나, 크롬은 10ppb 측정한계에서 측정불가능 하였다. 니켈 유리량은 제품에 따라 유의한 차이를 가져왔다 Galvanic조건이나 Sand blasting처리는 니켈 유리량에 증가를 가져왔으나 통계학적으로 유의하지 않았다.

• 대한치과교정학회지
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• 제27권3호
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• pp.493-502
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• 1997

본 연구에서는 치과용 니켈-크롬합금의 표면에 전처리없이 치과용 브라켓을 Super-bond로 접착한 대조군과 샌드블라스팅 및 tin-plating을 각각 혹은 병용으로 표면처리후 Super-bond로 접착한 실험각군의 인장접착강도, 브라켓 탈락양상 및 주사전자현미경 소견을 비교하여 임상적용 가능성을 알아보고자 하였으며 다음과 같은 결과를 얻었다. 1. 인장장접착강도는 니켈-크롬합금의 표면에 샌드블라스팅 처리후 Super-bond로 브라켓을 접착한 실험 I군이 $14.41{\pm}2.24MPa$로 가장 높았고, tin-plating처리후 Super-bond로 접착한 실험 III군이 $13.59{\pm}1.51MPa$, 샌드블라스팅후 tin-lating처리를 하고 Super-bond로 접착한 실험 II군이 $12.27{\pm}1.45MPa$, 특정한 표면처리 없이 Super-bond로 접착한 대조군이 $10.50{\pm}1.57MPa$로 가장 낮게 나타났으나 실험 I군과 실험 III군간, 실험 III군과 실험 II군간, 실험 II군과 대조군간에는 유의한 차이가 없었다(p>0.05). 2. 브라켓의 주된 탈락양상은 대조군의 경우 $70\%$가 브라켓과 접착제 계면에서 adhesive failure를, $30\%$가 니켈-크롬합금과 접착제 계면에서 adhesive failure를 나타내었고, 실험 각군은 모두 브라켓과 접착제 계면에서 adhesivefailure 를 나타내었다. 3. 주사전자현미경 소견에서 대조군의 경우 일부 레진이 브라켓 기저면에 부착되어 나타났으나 실험 각군에서는 거의 대부분의 레진이 니켈-크롬합금면에 부착되어 관찰되었고, 샌드블라스팅만 시행한 시편면이 가장 균일하고 조밀한 표면 요철상을 나타내었다.

• 대한치과보철학회지
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• 제33권3호
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• pp.584-609
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• 1995

The purpose of this study was to evaluate the difference of the galvanic corrosion behaviour of the titanium in contact with gold alloy, silva-palladium alloy, and nickel-chromium alloy using the immersion and electrochemical method. And the effects of galvallit couples between titanium and the dental alloys were assessed for their usefulness as materials for superstructure. The immersion method was performed by measuring the amount of metal elementsreleased by Inductivey coupled plasma emission spectroscopy(ICPES) The specimen of fifteen titanium plates, the five gold alloy, five silver-palladium, five nickel-chromium plates, and twenty acrylic resin plates ware fabricated, and also the specimen of sixty titanium plugs, the thirty gold alloy, thirty silver-palladium, and nickelc-hromium plugs were made. Thereafter, each plug of gold alloy, silver-palladium, and nickel-chromium inserted into the the titanium and acrylic resin plate, and also titanium plug inserted into the acrylic resin plate. The combination specimens uf galvanic couples immersed in 70m1 artificial saliva solution, and also specimens of four type alloy(that is, titanium, gold, silver-palladium and nickel-chromium alloy) plugs were immersed solely in 70m1 artificial sativa solution. The amount of metal elements released was observed during 21 weeks in the interval of each seven week. The electrochemical method was performed using computer-controlled potentiosta(Autostat 251. Sycopel Sicentific Ltd., U.K). The wax patterns(diameter 11.0mm, thickness,in 1.5mm) of four dental casting alloys were casted by centrifugal method and embedded in self-curing acrylic resin to be about $1.0cm^2$ of exposed surface area. Embedded specimens were polished with silicone carbide paper to #2,000, and ultrasonically cleaned. The working electrode is the specimen of four dental casting alloys, the reference electrode is a saturated calmel electrode(SCE) and the ounter electrode is made of platinum plate. In the artificial saliva solution, the potential scanning was carried out starting from-700mV(SCE) TO +1,000mV(SCE) and the scan rate was 75mV/min. Each polarization curve of alloy was recorded automatically on a logrithmic graphic paper by XY recorder. From the polarization curves of each galvanic couple, corrosion potential and corrosion rates, that is, corrosion density were compared and order of corrosion tendency was determined. From the experiments, the following results were obtained : 1. In the case of immersing titanium, gold alloy, silver-palladium alloy, and nickel-chromium alloysolely in the artificial saliva solution(group 1, 2, 3, and 4), the total amount of metal elements released was that group 4 was greater about 2, 3 times than group 3, and about 7.8 times than group 2. In the case of group 1, the amount of titanium released was not found after 8 week(p<0.001). 2. In the case of galvanic couples of titanium in contact with alloy(group 5, 6), the total amount of metal elements released of group 5 and 6 was less than that of group 7, 8, 9, and 10(p<0.05). 3. In the case of galvanic couples of titanium in contact with silver-palladium alloy(group 7, 8), the total amount of metal elements released of group 7 was greater about twice than that of group 5, and that of group 8 was about 14 times than that of group 6(p<0.05). 4. In the case of galvanic couples of titanium in contact with nickel-chromium alloy(group 9, 10), the total amount of metal elements released of group 9 and 10 was greater about 1.8-3.2 times than that of group 7 and 8, and was greater about 4.3~25 times than that of group 5 and 6(p<0.05). 5. In the effect of galvanic corrosion according to the difference of the area ratio of cathode and anode, the total amount of metal elements released was that group 5 was greater about 4 times than group 6, group 8 was greater about twice than group 7, and group 10 was greater about 1.5 times than group 9(p<0.05). 6. In the effect of galvanic corrosion according to the elasped time during 21 week in the interval of each 7 week, the amount of metal elements released was decreased markedly in the case of galvanic couples of the titanium in contact with gold alloy and silver-palladium alloy but the total amount of nickel and beryllium released was not decreased markedly in the case of galvanic couples of the titanium in contact with nickel-chromium alloy(p<0.05). 7. In the case of galvanic couples of titanium in contact with gold alloy, galvanic current was lower than any other galvanic couple. 8. In the case of galvanic couples of titanium in contact with nickel-chromium alloy, galvanic current was highest among other galvanic couples.

• 대한치과교정학회지
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• 제20권2호
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• pp.381-390
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• 1990

The purpose of this study was to evaluate the effects of heat treatment on mechanical properties in $0.016^{{\prime}{\prime}}{\times}0.022^{{\prime}{\prime}}$ blue Elgiloy wires and to measure the amounts of nickel and chromium released from the wires in artificial saliva. Ultimate tensile strength, yield strength and elongation were measured with universal testing machine (Instron). and the amounts of nickel and chromium released from the sample were measured with atomic absorption spectrophotometer after one week immersion in the artificial saliva. Ultimate tensile strength and yield strength were progressively increased below $1000^{\circ}F$, but elongation was decreased. And the results were reversed above $1100^{\circ}F$. After heat treatment of the sample for 9 minutes at $1000^{\circ}F$, the maximum tensile strength and yield strength were $213.6kg/mm^2$, $140.1kg/mm^2$, respectively. Both tensile strength and yield strength were decreased progressively above $1100^{\circ}F$. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at $1000^{\circ}F$. There was a pronounced increase in nickel and chromium liberation with increasing time and temperature. The maximum amounts of nickel and chromium released form the sample were $4.947{\mu}m/cm^2$, $3.088{\mu}g/cm^2$, respectively after heat treatment for 12 minutes at $1300^{\circ}F$. Heat treatment is applied to orthodontic wires, especially cobalt-chromium alloys, for the purpose of stress-relievning and hardening. When the heat-treatment of orthodontic wires, the heating procedure should be well controlled in order to have no effect on corrosion resistance and mechanical properties.

• Corrosion Science and Technology
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• 제9권5호
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• pp.196-200
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• 2010

Recently porous metal has been used as supporting metal in planar type SOFC. In order to search optimum alloys for porous metal support and estimate the stability of metal-supported SOFC at high temperature, it is necessary to investigate the oxidation behaviors of porous material for metal support in comparison with dense material. Oxidation tests of porous and dense stainless steels were conducted at $600^{\circ}C$ and $800^{\circ}C$. Since the specific surface area of porous material is much larger than that of dense material, surface area should be considered in order to compare the oxidation rate of porous stainless steel with that of dense stainless steel. The specific surface area of porous body was measured using image analyzer. The weight gain of porous stainless steel was much greater than those of dense stainless steels due to its larger specific surface area. considering the specific surface area, the oxidation rate of porous stainless steel is likely to be the same as that of dense stainless steel with the same surface area. The change in chromium content in stainless steel during oxidation was also investigated. The experimental result in chromium content in stainless steel during oxidation corresponded with the calculated value. While the change in chromium content in dense stainless steel during oxidation is negligible, chromium content in porous stainless steel rapidly decreases with oxidation time due to its large specific surface area. The significant decrease in chromium content in porous stainless steel during oxidation may affect the oxidation resistance of porous stainless steel support and long term stability of metal-supported SOFC.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.362-362
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• 2006

Chromic acid anodizing of aluminium is an effective process for producing a substrate which provides excellent surface properties to assembly. However, new chromium-free finishing metal treatments are being developed to reach new environmental goals. Present study deals with chromium free experimental conditions for both deoxidizing and anodizing treatments. Results clearly demonstrate the potentiality for environmentally friendly treatments to get suitable metal-adhesive performance. In particular, the role of both metal surface porosity and chemical composition has been highlighted thus allowing to propose alternative to classical treatments for aeronautic applications.

• 대한치과보철학회지
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• 제17권1호
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• 소성∙가공
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• 제8권3호
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• pp.319-319
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• 1999

From isothermal and cyclic oxidation tests on thermomechanically treated Ti-5%Al, Ti47%Al-4%Cr, and Ti-48%Al-2%Cr-2%Nb alloys at 800, 900, 1000℃ in air, it was found that Ti-48%Al-2%Cr-2%Nb and Ti-47%Al-4%Cr had the best and the worst oxidation resistance, respectively. The oxide scales consisted primarily of TiO₂and Al₂O₃, with and without a small amount of dissolved Cr and 7b ions, depending on the alloy composition. These ions were slightly enriched inside the inner oxide layer, and strongly enriched around the scale-matrix interface. The outer TiO₂-rich layer was formed by the outward diffusion of Ti ions, while the inner (TiO₂+A1₂O₃,) mixed layer was formed by the inward transport of oxygen. The outward movement of Al ions farmed the intermediate Al₂O₃-rich Iayer, above talc prepared alloys.

• 한국표면공학회지
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• 제35권4호
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• pp.232-240
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• 2002

The composition and the microstructure of the Zn-Cr alloys electroplated in chloride bath with EDTA were studied according to electrolysis conditions. The cathode current efficiency decreased with increasing both Cr/(Cr+Zn) ratio and current density. The Cr content of the alloy deposits increased with Cr/(Cr+Zn) ratio and current density The phase structure of Zn-Cr alloy deposits changed from η-Zn through η-Zn+${\gamma}$'-ZnCr to ${\gamma}$'-ZnCr with increasing Cr content of alloys. The surface morphology of Zn-Cr alloy deposits changed from fine needle shaped crystallites through the mixed structure of needle-shaped and granular one to the colony structure with fine granular crystallites according to the change of phase structure