• Title/Summary/Keyword: dissolution resistance

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Corrosion of Quartz Crystal Sensors in Sea Water (항만센서용 수정진동자의 해수에 의한 부식)

  • ;;;A. Egawa;H. Muramatsu
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1998.10a
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    • pp.183-188
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    • 1998
  • A quartz crystal analyzer is utilized to monitor the cmsion process of an aluminum surface of a quartz crystal by sea water. A quartz crystal having 2000${\AA}$ of aluminum layer is installed in a spedally designed cell and is in contact with an electrolyte solution. While a constant potential is applied to the cell, the resonant frequency and resonant resistance are simultaneously measured using the quartz crystal analyzer. In addition, surface topographs are taken with an atomic force microscope(AFM) and the element analysis of the surface is conducted using an energy dispersive X-ray spectrornetedEDX). The simultaneous measurement of resonant frequency and resonant resistance during the corrosion process explains the change of surface structure caused by the corrosion. The variation of resonant frequency addresses the amount surface metal dissolution. As a conclusion, it is found that a simple measurement using the quartz crystal analyzer can replace the complex monitoring employing large equipments in the investigation of a corrosion process of metal surface.

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Effect of Solution Treatment on Corrosion Behavior of AZ91-2%Ca Magnesium Casting Alloy (주조용 AZ91-2%Ca 마그네슘 합금의 부식 거동에 미치는 용체화처리의 영향)

  • Moon, Jung-Hyun;Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.28 no.4
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    • pp.190-199
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    • 2015
  • The study is intended to investigate the effect of solution treatment on microstructure and corrosion behavior of AZ91(Mg-9%Al-1%Zn-0.3%Mn)-2%Ca casting alloy. In as-cast state, the AZ91-2%Ca alloy consisted of intermetallic ${\beta}(Mg_{17}Al_{12})$, $Al_8Mn_5$ and $Al_2Ca$ phases in ${\alpha}-(Mg)$ matrix. After the solution treatment, Al within the ${\alpha}-(Mg)$ matrix was distributed more homogeneously, along with the slight decrease in the total amount of intermetallic compounds. The corrosion resistance of the AZ91-2%Ca alloy was improved after the solution treatment. The microstructural examinations for the solution-treated samples revealed that the better corrosion resistance may well be related to the incorporation of more oxides and hydroxides such as $Al_2O_3$, $Al(OH)_3$, CaO and $Ca(OH)_2$ into the surface corrosion product without dissolution of the intermetallic phases along the grain boundaries.

Differential Subcellular Responses in Resistance Soybeans Infected with Soybean Cyst Nematode Races

  • Kim, Young-Ho;Kim, Kyung-Soo;Riggs, Robert D.
    • The Plant Pathology Journal
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    • v.26 no.2
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    • pp.154-158
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    • 2010
  • Early nematode development and subcellular responses in resistant soybean lines PI 88788 and PI 437654 infected with races 3 (R3) and 14 (R14) of soybean cyst nematode (SCN), Heterodera glycines Ichinohe, were compared. SCN R14 nematodes penetrated and developed significantly more than R3 at 5-6 days after inoculation. Both races also penetrated and developed more in PI 88788 than in PI 437654. Syncytia, characterized by cell wall dissolution and cellular hypertrophy, were developed more in PI 88788 than in PI 437654 and more by R14 than R3, for which less necrotic responses occurred in the former than the latter. This suggests that the latter two may be more resistant and less virulent than the former two, respectively. A common structural feature found in each of PI 437654 and PI 88788 in relation to SCN-resistance was the formation of prominent cell wall appositions and nuclear degeneration prior to cytoplasmic degradation in syncytial cells, respectively. Necrosis and cell wall apposition are types of hypersensitive responses occurring at early stages of the nematode infection so that these structural modifications indicate the inhibition of initial syncytial development related to the early nematode development. As soybean cultivars and lines with identical or similar genotypes have the same types of structural features related to SCN-resistance, the structural modifications induced by SCN infection may result from the expression of inheritable resistance genes, of which the information can be used for breeding soybean cultivars and lines specifically resistant to SCN races.

Belle Epoque and Dadaism in the Modern Culture (벨 에포크와 다다이즘 - 근대문화의 총체와 해체)

  • Lee, Byung Soo
    • Cross-Cultural Studies
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    • v.33
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    • pp.171-192
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    • 2013
  • The article is a research about the Belle Epoque era and Dadaism in the modern culture as a whole and separate. The years from 1890s to 1914, is known as the Belle Epoque era, in which the European continent including France had developed the climax of the modern culture after the Renaissance. At the same time, it was the period where the postmodern developments were being spread, leading to the present days. Moreover, the main ideologies in art that led to the cultural advancement of the time were impressionism, cubism, art nouveau, evolutionized painting category, symbolism and futurism. It was a literature category that was maintained to present Dadaism and surrealism. Dadaism began since the magazine, Bulletin Dada was published, originating in 1916 by Tristan Tzara of Zurich, Switzerland during the WWI. The extreme motto that the Dadaists supported was a contradiction, as they had to dissolve from their own art movements and expression techniques. However, until Andre Breton introduced 'Manifeste du Surrealisme' in 1924, the "Dada group" had a tremendous influence in France as an epicenter and rejected the modern cause and art that continued during the time, thus attempting its dissolution. First, they rejected the ideology, ethics and customs of rationalism from the previous system and demonstrate an anarchical and anti-bourgeoisie characteristic. They also reject the French lucid thoughts and the artistic techniques. They strongly emphasized on their motto "The idea is created from the mouth", while reframing from the philosophical ideology and at the same time, attempting to express the psychical unconsciousness. Second, the most important catchphrase that the Dadaists supported was the theory of negation. The question "Why do you write?" connotes the negative consciousness about the artistic value and the stereotyped method of the preexisting writing and drawing. Third, the Dadaists bring forward a radical query about all of the former esthetic and morals, and reveal an admirable resistance spirit. They emphasized on the slogan "Dada, means nothing" and insist on 'the anti-literal Dada, anti-artistic Dada, anti-musical Dada'. The Dadaist movement manifested their resistant spirit and the new artistic spirit through the publication of , , and most importantly through the magazine . Fourth, the Dadaists embodied the volume, density, and quality into an image through the auto-technical, cubistic writings and drawings. They ignored the fixed form of arrangements, verses, and rhymes of a poetic diction. The Dadaists utilized an unfamiliar and inversed expression method of applying the combination of the size of print, or capital letters and lowercase letters, even combining printed and handwritten writings. As presented, the auto-technical and cubistic characteristic of expressing the auto-psychical ideology into writing is called as the radical aesthetic and moral and can be considered as the most essential cause of the Dadaists' avant-garde features. As a conclusion, Dadaism demonstrated dual characteristics of consuming the nutritive elements of the modern culture through the most powerful resistance and liberation of the artistic movement of the Belle Epoque era, where at the same time, it deconstructed the modern art. By revolting against the former grounds and expression techniques, and dominating the era with the new artistic spirit, their resistant actions were artistic movements that symbolized the dissolution of the modern times. Moreover, the Dada's expressionism and resistance of saying "There's nothing" can be evaluated as postmodernity's initiative of outweighing the modern history and opening the door for new period of nowadays.

Role of Ca in Modifying Corrosion Resistance and Bioactivity of Plasma Anodized AM60 Magnesium Alloys

  • Anawati, Anawati;Asoh, Hidetaka;Ono, Sachiko
    • Corrosion Science and Technology
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    • v.15 no.3
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    • pp.120-124
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    • 2016
  • The effect of alloying element Ca (0, 1, and 2 wt%) on corrosion resistance and bioactivity of the as-received and anodized surface of rolled plate AM60 alloys was investigated. A plasma electrolytic oxidation (PEO) was carried out to form anodic oxide film in $0.5mol\;dm^{-3}\;Na_3PO_4$ solution. The corrosion behavior was studied by polarization measurements while the in vitro bioactivity was tested by soaking the specimens in Simulated Body Fluid (1.5xSBF). Optical micrograph and elemental analysis of the substrate surfaces indicated that the number of intermetallic particles increased with Ca content in the alloys owing to the formation of a new phase $Al_2Ca$. The corrosion resistance of AM60 specimens improved only slightly by alloying with 2 wt% Ca which was attributed to the reticular distribution of $Al_2Ca$ phase existed in the alloy that might became barrier for corrosion propagation across grain boundaries. Corrosion resistance of the three alloys was significantly improved by coating the substrates with anodic oxide film formed by PEO. The film mainly composed of magnesium phosphate with thickness in the range $30-40{\mu}m$. The heat resistant phase of $Al_2Ca$ was believed to retard the plasma discharge during anodization and, hence, decreased the film thickness of Ca-containing alloys. The highest apatite forming ability in 1.5xSBF was observed for AM60-1Ca specimens (both substrate and anodized) that exhibited more degradation than the other two alloys as indicated by surface observation. The increase of surface roughness and the degree of supersaturation of 1.5xSBF due to dissolution of Mg ions from the substrate surface or the release of film compounds from the anodized surface are important factors to enhance deposition of Ca-P compound on the specimen surfaces.

Influence of Austenitizing Conditions on the Mechanical Properties in 420J1 Martensitic Stainless Steel (420J1 마르텐사이트계 스테인리스강의 오스테나이트화 조건이 기계적 성질에 미치는 영향)

  • Kim, Y.J.;Joo, D.W.;Park, S.H.;Kim, G.D.;Sung, J.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.1
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    • pp.25-34
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    • 1994
  • To investigate the effect of austenitizing tempratures on the mechanical properties and corrosion resistance of 0.19%C-13.6%Cr martensitic stainless steel, the changes in martensitic trasformation temperatures, mechanical properties and anodic polarization curve were examined after changing the austenitizing temperatures and tempering temperatures. On increasing heating rate at the same austenitizing temperatures, $A_s$, $A_r$ and $M_s$ increased. And the $M_s$ temperature showed to be decreased with increasing austenitizing temperature. With increasing tempering temperature up to $500^{\circ}C$, strength, hardness and impact value were not changed remarkably, on the other hand the tensile strength and hardness decreased and impact value increased after tempering above $550^{\circ}C$ owing to the $M_{23}C_6$ carbide precipitation. The abrupt decrease in elongation at the tempering temperture of $500^{\circ}C$ proved to the precipitation of $M_7C_3$ carbide. The effect of austenitizing temperature on the mechanical properties of the tempered specimen showed to be decreased in impact value and elongation at the austenitizing temperature of $1150^{\circ}C$. At low tempering temperatures the corrosion resistance of the tempered specimen was not changed obviously with increasing tempering temperature. On the other hand, the resistance decreased above the tempering temperature of $600^{\circ}C$ due to the precipitation of $M_{23}C_6$ carbides. The corrosion resistance showed to be improved with increasing the austenitizing temperature owing to the dissolution of carbides.

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Electrochemical Characteristics of Osteoblast Cultured Ti-Ta Alloy for Dental Implant (골아세포가 배양된 치과 임플란트용 Ti-Ta합금의 전기화학적 특성)

  • Kim, W.G.;Choe, H.C.;Ko, Y.M.
    • Journal of the Korean institute of surface engineering
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    • v.41 no.2
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    • pp.69-75
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    • 2008
  • Electrochemical behaviors of surface modified and MC3T3-E1 cell cultured Ti-30Ta alloys have been investigated using various electrochemical methods. The Ti alloys containing Ta were melted by using a vacuum furnace and then homogenized for 6 hrs at $1000^{\circ}C$. MC3T3-E1 cell culture was performed with MC3T3-E1 mouse osteoblasts for 2 days. The microstructures and corrosion resistance were measured using FE-SEM, XRD, EIS and potentiodynamic test in artificial saliva solution at $36.5{\pm}1^{\circ}C$. Ti-Ta alloy showed the martensite structure of ${\alpha}+{\beta}$ phase and micro-structure was changed from lamellar structure to needle-like structure as Ta content increased. Corrosion resistance increased as Ta content increased. Corrosion resistance of cell cultured Ti-Ta alloy increased predominantly in compared with non cell cultured Ti- Ta alloy due to inhibition of the dissolution of metal ion by covered cell. $R_p$ value of MC3T3-E1 cell cultured Ti-40 Ta alloy showed $1.60{\times}10^6{\Omega}cm^2$ which was higher than those of other Ti alloy. Polarization resistance of cell-cultured Ti-Ta alloy increased in compared with non-cell cultured Ti alloy.

Influences of Coating Cycles and Composition on the Properties of Dimensionally Stable Anode for Cathodic Protection

  • Yoo, Y.R.;Chang, H.Y.;Take, S.;Kim, Y.S.
    • Corrosion Science and Technology
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    • v.5 no.2
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    • pp.45-51
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    • 2006
  • Properties of the anode for cathodic protection need low overvoltage for oxygen evolution and high corrosion resistance. It is well known that DSA (Dimensionally Stable Anode) has been the best anode ever since. DSA is mainly composed of $RuO_2$, $IrO_2$, $ZrO_2$, $Co_2O_3$, and also $Ta_2O_5$, $TiO_2$, $MnO_2$ are added to DSA for better corrosion resistance. The lifetime of DSA for cathodic protection is also one of the very important factors. $RuO_2$, $IrO_2$, $RhO_2$, $ZrO_2$ are well used for life extension, and many researches are focused on life extension by lowering oxygen evolution potential and minimizing dissolution of oxide coatings. This work aims to evaluate the influence of constituents of MMO and coating cycles and $ZrO_2$ coating on the electrochemical properties and lifetime of DSA electrodes. From the results of lifetime assessment in the anodes coated with single component, $RuO_2$ coating was more effective and showed longer lifetime than $IrO_2$ coating. Also, an increased coating cycle and an electrochemically coated $ZrO_2$ could enhance the lifetime of a DSA.

Corrosion Behavior of Titanium for Implant in Simulated Body Fluids (인공 체액 조건에서 임플랜트용 티타늄 소재의 부식 특성)

  • 이중배;최기열
    • Journal of the Korean institute of surface engineering
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    • v.37 no.2
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    • pp.110-118
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    • 2004
  • The corrosion of pure titanium (CP- Ti Grade 2) and titanium alloy (Ti6Al4V ELI) were studied under various conditions of simulated body fluids. The static immersion test and the electrochemical test were performed in accordance with ISO 10271 : 2001. For the electrochemical test, the open circuit potential was monitored as a function of time, and the cyclic polarization curve was recorded. The corrosion resistance was evaluated from the values of corrosion potential, passivation current density, breakdown potential, and the shape of hysteresis etc. The effects of alloy type, surface condition, temperature, oxygen, and constituents in the fluids such as acid, chloride were estimated. Both specimens had extremely low dissolution rate in the static immersion test. They showed strong passivation characteristics in the electrochemical test. They maintained negligible current density throughout the wide anodic potential range. The passive layer was not broken up to 2.0 V (vs. SCE). The hysteresis and the shift of passivation potential toward the anodic direction was observed during the reversed scan. The passivation process appeared to be accelerated by oxygen in air or that dissolved in the fluids. The passivation also proceeded without oxygen by the reaction of constituents in the fluids. Acid or chloride in the fluids, specially later weakened the passive layer, and then induced higher passivation current density and less shift of passivation potential in the reversed scan. CP-Ti Grade 2 was more reactive than Ti6Al4V ELI in the fluids containing acid or chloride, but thicker layer produced on its surface provided higher corrosion resistance.

Evaluation of Plasma Spray Hydroxy Apatite coatings on Metallic Materials

  • Take, S.;Mitsui, K.;Kasahara, M.;Sawai, R.;Izawa, S.;Nakayama, M.;Itoi, Y.
    • Corrosion Science and Technology
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    • v.6 no.6
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    • pp.286-290
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    • 2007
  • Biocompatible Hydroxy apatite (HAp) coatings on metallic substrate by plasma spray techniques have been developed. Long-term credibility of plasma spray HAp coatings has been evaluated in physiological saline by electrochemical measurements. It was found that the corrosion resisitance of SUS316L based HAp/Ti conbined coatings was excellent even after more than 10 weeks long-term immersion. It was shown that postal heat treatment improved both the crystallinity and corrosion resistance of HAp. By lowering cooling rate during heat treatment process, less cracks produced in HAp coating layer, which lead to higher credibility of HAp during immersion in physiological saline. The ICP results showed that the dissolution level of substrate metallic ions was low and HAp coatings produced in this research can be acceptable as biocompatible materials. Also, the concentration of dissolved ions from HAp coatings with postal heat treatment was lower compared to those from samples without postal heat treatment. The adherence of HAp coatings with Ti substrate and other mechanical properties were also assessed by three-point bending test. The poor adhesion of HAp coating to titanium substrate can be improved by introducing a plasma spray titanium intermediate layer.