• Restorative Dentistry and Endodontics
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• 제18권2호
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• pp.431-445
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• 1993

The purpose of this study was to observe corrosion characteristics of six dental amalgams and was to analyse corrosion products electrochemically. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by using mechanical amalgamator, the triturated mass was inserted into the cylinderical metal mold ($12{\times}10mm$) and was condensed with 160kg/$cm^2$ by using the hydrolic press. The specimen was removed from the mold and was stored at room temperature for 1 week, and was polished with amalgam polishing kit. The anodic and cathodic polarization curve was obtained by using cyclic voltammetric method with 3-electrode potentiostat in saline for each amalgam and Ag, Sn, Cu plate specimen at $37{\pm}0.5^{\circ}C$. The potential sweep range was -1.7V~0. 4V(vs SCE) in working electrode and scan rate was 50mV/s and the exposed surface area of each specimen to the electrolytic solution was $0.79cm^2$. The results were as follows. 1. In anodic-cathodic polarization curve of amalgam specimens, two anodic current rising areas and two cathodic current peaks were obtained at the low Cu amalgam(CF, CS) specimen and three anodic current rising areas and three cathodic current peaks were obtained at the high Cu amalgam (TY, DS, HV) specimen. 2. As this compared with the anodic and cathodic current peak potentials of Sn, Cu and Ag specimen, the first cathodic current peak I c was caused by the reduction of divalent tin salt, second cathodic current peak IIIc results from the reduction of quadravalent tin salt, and third cathodic current peak me results from the reduction of copper salt. 3. As reverse potential sweeping was done repeatedly, anodic current was decreased slightly in all amalgam specimens.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권3호
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• pp.165-171
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• 2000

Experiments were carried out to measure variations in the oxidation potential and current density using the polarization curves of polycarbonate. The results were then examined to identify the influences affecting the oxidation potential related to various conditions, such as temperature, pH, and oxydase(citrate and lipase). The lines representing the active anodic and cathodic dissolution shifted only slightly in the potential direction relative to temperature, pH, and the effect of the enzyme. The Tafel slope for the anodic and cathodic dissolution was determined such that the reversibility polarization was indicated as being effected by various conditions. The slope of the polarization curves describing the active-to-passive transition region shifted noticeably in their direction. Also, by varying the conditions, the optimum conditions for the most ready transform were identified, including temperature, pH, oxidation rate, and resistance of oxidation potential. The critical oxidation sensitivity(I(sub)r/I(sub)f) of the anodic current density peak and maximum passive current density was also determined, which is used in measuring the critical corrosion sensitivity of a polycarbonate.

• 대한화학회지
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• 제21권4호
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• pp.276-283
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• 1977

산성용액중에서 백금음극을 사용하여 중크롬산이온의 환원을 전위주사법 및 정전위전해에 의하여 검토하였다. 지지전해질로서 황산나트륨(pH 1.5∼4.0)을 사용한 비완충용액중의 중크롬산칼륨의 분극곡선은 3단파가 생기며 첫째파 및 둘째파의 파고는 각각 크롬(Ⅵ)농도 및 수소이온의 활동도에 비례하나 셋째파는 어느 것에도 비례하지 않았다. 첫째 및 둘째 peak이 전류는 전위주사속도(${\nu}$)에 비례하나 셋째 peak는 50mV/sec이하의 늦은 주사속도에서 ${\nu}^{1/2}$에 비례하였다. 정전위전해에 의하면, 크롬(Ⅵ)의 환원은 셋째 peak보다 더 base이고 초기 pH가 약 2.3 이상이 되면 완전히 억제되었다. 그러므로 이 세 peak는 각각 $Cr_2O_7^{\to}Cr^{3+},\;2H^+{\to}H_2$ 및 음극피막의 형성으로 간주하였다.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.502-514
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• 1998

The purpose of this study is to observe the corrosion characteristcs of four dental amalgams(CAULK FINE CUT, CAULK SPHERICAL, DISPERSALLOY, TYTIN) and to determine a function of chloride concentration through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylinderical metal mold, and condensed by hydrolic pressure. Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 6 months. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam m KCl and KCl-NaCl solution, which had chlonde concentration of 0.4 g/l, 0.8 g/l, 1.2 gil, and 1.6 gil at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was - 1500mV ~+800mV(vs. S.C.E.) in the working electrode and the scan rate was 50mV/sec. The results were as follows, 1. The corrosion potential. the potential of anodic current peak, and transpassive potential in the solution of high chloride concentration shifted to more cathodic direction than those in the solution of low concentration, and the current density in the solution of high chloride concentration was higher than that in the solution of low concentration. 2. The corrosion potential, the potential of anodic current peak, and transpassive potential for CAULK FINE CUT amalgam were the most cathodic among the others, and the current density were the highest among the others. 3. In the solution of low chloride concentration, the corrosion potential, the potential of anodic current peak, and transpassive potential for DISPERSALLOY were the most anodic among the others, however in the solution of high chloride concentration, those for TYTIN were the most anodic among the others. 4. The anodic polarization curve for CAULK SPHERICAL was similar to that for high copper amalgams.

• Journal of Electrochemical Science and Technology
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• 제15권3호
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• pp.405-413
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• 2024

Several techniques for determining the reverse peak current from a cyclic voltammogram (CV) for a reversible system are described in the literature: CV itself as a baseline with long switching potential (E_λ) that serves as a baseline for other CVs, Nicholson equation that uses CV parameters to calculation reverse peak current and linear extrapolation of the current obtained at the switching potential. All methods either present experimental difficulties or large errors in the peak current determination. The paper demonstrates, both theoretically and experimentally, that trapezoidal cyclic voltammetry (TCV) can be used as a baseline to determine anodic peak current (i_ap) with high accuracy and with a switching potential shorter than that used by CV, as long as E_λ is at least 130 mV away from the cathodic peak. Beyond this value of switching potential the electroactive specie is completely depleted from the electrode surface. Using TCV with E_λ = 0.34 V and a switching time (t_λ) of 240 s as a baseline, the determination of the reverse peak current presents a deviation from the expected value of less than 1% for most of the CVs studied (except cases when E_λ is close to the direct potential peak). This result presents better accuracy than the Nicholson equation and the linear extrapolation of the current measured at the switching potential, in addition to presenting a smaller error than that obtained in the acquisition of the experimental current. Furthermore, determining the reverse peak current by extrapolating the linear fit of i_ap vs. ${\sqrt[1/]{t_{\lambda}}}$ to infinite time gave a reasonable approximation to the expected value. Experiments with aqueous potassium hexacyanoferrate (II) and ferrocene in acetonitrile confirmed the theoretical predictions.

• 분석과학
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• 제5권4호
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• pp.417-423
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• 1992

음극 벗김 전압전류법을 이용하여 비소(III)의 벗김 봉우리에 대한 금속 이온의 영향에 대하여 조사하였다. 비소(III)의 환원 벗김 봉우리 이론적인 전위값이 -0.84V(vs. Ag/AgCl)인데 비하여, 0.1N- 염산을 사용하였을 때 전위값은 -0.79V(vs. Ag/AgCl)이고, 여기에 구리(II)를 10배 첨가하였을 때 -0.84V로써 이론적인 전위값과 일치하였으며 전류값은 $0.86{\mu}A$로 가장 높게 나타났다. 비소(III)의 벗김 봉우리를 증가시키는 금속이온으로 납(II), 구리(II) 등이 있었고, 특히 구리(II)이온이 비소(III)의 벗김 봉우리를 가장 많이 증가시켰다.

• 대한화학회지
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• 제39권1호
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• pp.23-28
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• 1995

Sn(II)-cupferron 착물에 대한 펄스차이 음극벗김 전압전류법적 연구를 pH 4.20의 0.1 M 아세트산 완충용액에서 수행하였다. 수은전극 표면에 흡착된 Sn(II)-cupferron 착물의 환원피크전류 크기에 미치는 용액의 pH, 착화제의 농도, 축적전위 및 축적시간의 영향을 검토하였다. 또한 Sn(II)-cupferron 착물의 환원피크전류에 영향을 주는 다른 금속 양이온들의 방해효과도 검토하였다. 이 방법에 의한 Sn(II)의 검출한계는 축적시간을 60 sec로 하였을 때 $3.1{\times}10^{-9}$ M(0.37 ppb)이었으며, $5{\times}10^{-8}$ M의 Sn(II) 분석에 대한 상대표준편차(n=8)는 3.0%이었다.

• 대한화학회지
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• 제43권2호
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• pp.161-166
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• 1999

Ionophore ETH4120의 이온담체작용에 의한 란탄족원소이온의 액체/액체계면에서의 상전이를 순환전압전류법(cyclic voltammetry)과 순환전류주사 대시간전위차법(Chronopotentiometry with cyclic linear current scanning; CPCLCS)으로 고찰하였다. 수용액 중의 란탄족원소이온농도가 유기용액중의 착화제 농도보다 훨씬 높을 때 순환전압전류법과 CPCLCS 곡선에서 하나의 양극전류(수용액상에서 유기상으로 전이)파와 두개의 음극전류(유기상에서 수용액상으로 전이)파가 관찰되었다. 양극전류파는 1:1(금속:착화제) 착물형성과 관계되는 봉우리이고, 두 음극전류파는 각각 1:2와 1:3의 연속적인 착물형성과 관계된 파이다. 그러나 1:1 착물의 양극전류파와 대응하는 1:1 착물의 음극파와, 1:2 착물과 1:3 착물의 음극전류파에 대응되는 양극전류파는 나타나지 않았다. 이와 관련되는 이온 상전이 메카니즘을 검토하였다.

• 한국응용과학기술학회지
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• 제16권3호
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• pp.205-210
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• 1999

The Mo(V) $di-{\mu}-oxo$ type $[Mo_2O_4(H_2O)_2L]Cl_2$ complexes(L: 4,4'-Diphenyl-2,2'-dipyridyl, 4,4'-Dimethyl-2,2'-dipyridyl, 4,7-Diphenyl-1,10-phenanthroline) have been prepared by the reaction of $[Mo_2O_4(H_2O)_6]^{2+}$ with a series of chelate ligands. These complexes are completed by two terminal oxygens arranged trans to one another and each ligand forms a chelate types. In $Mo_2O_4(H_2O)_2L$ two $H_2O$ coordinated at trans site of terminal oxgens. The prepared complexes have been characterized by elemental analysis, infrared spectra, electronic spectra, $^1H$ nuclear magnetic resonance spectra, and thermal analysis(TG-DTA). In the potential range -0.00V to -1.00V at scan rate of $50mVs^{-1}$, a cathodic peak at -0.83V ${\sim}$ -0.88V (vs SCE) and an anodic peak at -0.54V ${\sim}$ -0.88V (vs SCE) have been observed in aquous solution. The ratio of the cathodic to anodic current(Ipc/Ipa) is almost 2, we infer that redox is irreversible as dimer forms broken.

• 대한화학회지
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• 제57권5호
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• pp.568-573
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• 2013

A selective and sensitive method for simultaneous determination of copper in blood by adsorptive differential pulse cathodic stripping voltammetry is presented. The procedure involves an adsorptive accumulation of Cu(II)-ETSC (4- ethyl-3-thiosemicarbazide) on a hanging mercury drop electrode, followed by a stripping voltammetry measurement of reduction current of adsorbed complex at about -715 mV. The optimum conditions for the analysis of copper (II) ion are : pH 10.3, concentration of 4-ethyl-3-thiosemicarbazide $3.25{\times}10^{-6}$ M and an accumulation potential of -100 mV. The peak current is proportional to the concentration of copper over the range 0.003-125 ng/mL with a detection limit of 0.001 ng/mL and an accumulation time of 60 s. Moreover, with the use of the proposed method, there is a considerable improvement in the detection limit, the linear dynamic range and the deposition time, compared with the methods of adsorptive stripping voltammetry for the determination of copper. The developed method was validated by analysis of whole blood certified reference materials.