• Title, Summary, Keyword: Electrochemical properties

Search Result 1,804, Processing Time 0.06 seconds

An Evaluation of Degraded Damage for Superaustenitic Stainless Steel by Electrochemical Polarization Technique (전기화학기법에 의한 슈퍼 오스테나이트 스테인리스강의 열화손상 평가)

  • Kwon, Il-Hyun;Lee, Song-In;Baek, Seung-Se;Lee, Jong-Gi;Iino, Y.;Yu, Hyo-Sun
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.143-148
    • /
    • 2001
  • This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel. The steel was artificially aged at $300{\sim}650^{\circ}C$ for $240{\sim}10,000hrs$. and investigated at $-196{\sim}650^{\circ}C$ using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and ${\eta}-phase(Fe_2Mo)$ precipitated in the grain bounderies seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain bounderies and promote the current density observed in electrochemical polarization curves. The electrochemical and mechanical properties of superaustenitic stainless steel was drastically decreased in the specimen aged at $650^{\circ}C$.

  • PDF

An Nondestructive Evaluation of Degraded Damage for Superaustenitic Stainless Steel (슈퍼 오스테나이트 스테인리스강의 열화손상에 대한 비파괴적 평가)

  • Kwon, Il-Hyun;Baek, Seung-Se;Iino, Y.;Yu, Hyo-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.7
    • /
    • pp.1332-1339
    • /
    • 2002
  • This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel and to detect the material degradation nondestructively. The steel was artificially aged at $300{\sim}650^{\circ}C$ for $240{\sim}10,000h$ and the mechanical properties were investigated at $-196{\sim}650^{\circ}C$ using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging on superaustenitic stainless steel was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and ${\eta}-phase(Fe_2Mo)$ precipitated in the grain boundaries seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain boundaries and to promote the current density observed in electrochemical polarization curves, The electrochemical and mechanical properties of superaustenitic stainless steel decreased significantly in the specimen aged at $650^{\circ}C$ corresponding to the sensitization temperature for conventional austenitic stainless steels.

Recent Advances in Electrochemical Studies of π-Conjugated Polymers

  • Park, Su-Moon;Lee, Hyo-Joong
    • Bulletin of the Korean Chemical Society
    • /
    • v.26 no.5
    • /
    • pp.697-706
    • /
    • 2005
  • We review the evolution of electrochemical studies of conducting polymers into the current state-of-the-art based primarily on our work. While conventional electrochemical experiments sufficed for the needs in the phase of studies of both electrochemical synthesis and characterization of conducting polymers, developments of various new experimental techniques have led to their introduction to this field for more refined information. As a result, the conventional electrochemical, spectroelectrochemical, electrochemical quartz crystal microbalance, impedance, and morphological as well as electrical characterization studies all made important contributions to a better understanding of the polymerization mechanisms and the conductive properties of these classes of polymers. From this review, we hereby expect that the electrochemical techniques will continue to play important roles in bringing this field to the practical applications such as nanoscale electronic devices.

Pore Structure and Electrochemical Properties of Carbon Aerogels as an EDLC-Electrode with Different Preparation Conditions (EDLC 전극용 카본에어로젤의 합성조건에 따른 기공구조 및 전기화학적 특성)

  • Seo, Hye Inn;Jung, Ji Chul;Kim, Myung-Soo
    • Korean Journal of Materials Research
    • /
    • v.28 no.1
    • /
    • pp.50-61
    • /
    • 2018
  • Various carbon aerogels (CAs) were prepared from polymerization of resorcinol and formaldehyde and applied as the electrode materials of an electric double layer capacitor (EDLC) with the aim of controlling the textural and electrochemical properties of CAs by the type of base catalyst and the ratio of resorcinol to catalyst (R/C). The CAs from $NaHCO_3$ and $KHCO_3$ with $H^+$ ions had higher specific surface areas but exhibited lower electrochemical properties than those from $K_2CO_3$ and $Na_2CO_3$, which had more uniform pore size distributions. The electrochemical properties of $Na_2CO_3$ were superior to those of $K_2CO_3$ probably because the polarizing power of $Na^+$ ions was higher than $K^+$ ions. With an increasing R/C ratio, the pore sizes of CA showed a tendency to increase but the uniformity of the pore size distribution got worse. For the four base catalysts, the highest electrochemical property was obtained at the R/C ratio of 500.

Electrochemical Properties of Novel Metal Powder Electrodes for Polymer Electrolyte Membrane Electrolysis

  • Kim, Chang-Hee;Kang, Kyung-Soo;Park, Chu-Sik;Hwang, Gab-Jin;Bae, Ki-Kwang
    • Proceedings of the Korean Powder Metallurgy Institute Conference
    • /
    • /
    • pp.1227-1228
    • /
    • 2006
  • The electrochemical properties of novel metal powders were investigated for the electrode materias of polymer electrolyte memebrane electrolysis. Two types of Pt black and $IrO_2$ powder electrodes were hot-pressed on the polymer electrolyte membrane to form membrane electrode assembly. The galvanodynamic polarization methode was used to characterize the electrochemical properties of both electrodes. From the experimental results, we concluded that the $IrO_2$ powder electrode exhibits better electrochemical performance than Pt black as cathode material for the electrolysis.

  • PDF

The Synthesis and Electrochemical Properties of Lithium Manganese Oxide (Li2MnO3)

  • Seo, Hyo-Ree;Lee, Eun-Ah;Yi, Cheol-Woo;Kim, Ke-On
    • Journal of Electrochemical Science and Technology
    • /
    • v.2 no.3
    • /
    • pp.180-185
    • /
    • 2011
  • The layered lithium-manganese oxide ($Li_2MnO_3$) as a cathode material of lithium ion secondary batteries was prepared and characterized the physico-chemical and electrochemical properties. The morphological and structural changes of MnO(OH) and $Li_2MnO_3$ are closely connected to the changes of electrochemical properties. The crystallinity of $Li_2MnO_3$ is enhanced as the annealing temperature increase, but its capacity is reduced due to the easier structural changes of less crystalline $Li_2MnO_3$ than highly crystalline one. Moreover, the addition of buffer material such as MnO(OH) into cathode causes to reduce the morphological and structural changes of layered $Li_2MnO_3$ and increase the discharge capacity and cycleability.

Electrochemical Removal Efficiency of Pollutants on ACF Electrodes

  • Oh, Won-Chun;Park, Joung-Sung;Lee, Ho-Jin;Yum, Min-Hyung
    • Carbon letters
    • /
    • v.5 no.4
    • /
    • pp.191-196
    • /
    • 2004
  • The electrochemical removal (ECR) of water pollutants by activated carbon fiber (ACF) electrodes from wastewater was investigated over wide range of electrochemical reaction time. The ECR capacities of ACF electrodes were associated with their internal porosity and were related to physical properties and to reaction time. And, surface morphologies and elemental analysis for the ACFs after electrochemical reaction are investigated by SEM and EDX to explain the changes in adsorption properties. The FT-IR spectra of ACFs for the investigation of functional groups show that the electrochemical treatment is consequently associated with the homogeneous removal of pollutants with the increasing surface reactivity of the activated carbon fiber surfaces. The ACFs were electrochemically reacted to waste water to investigate the removal efficiency for the COD, T-N and T-P. From these removal results of pollutants using ACFs substrate, satisfactory removal performance was obtained. The outstanding removal effects of the ACFs substrate were determined by the properties of the material for adsorption and trapping of organics, and catalytic effects.

  • PDF

Effect of Hydrofluoric Acid on the Electrochemical Properties of Additive Manufactured Ti and Its Alloy (적층가공된 티타늄 합금의 전기화학적 특성에 미치는 불산의 영향)

  • Kim, K.T.;Cho, H.W.;Chang, H.Y.;Kim, Y.S.
    • Corrosion Science and Technology
    • /
    • v.17 no.4
    • /
    • pp.166-175
    • /
    • 2018
  • In this study, the electrochemical properties of CP-Ti (commercially pure titanium) and Ti-64 (Ti-6Al-4V) were evaluated and the effect of hydrofluoric acid on corrosion resistance and electrochemical properties was elucidated. Additive manufactured materials were made by DMT (Directed Metal Tooling) method. Samples were heat-treated for 1 hour at $760^{\circ}C$ and then air cooled. Surface morphologies were studied by optical microscope and SEM. Electrochemical properties were evaluated by anodic polarization method and AC-impedance measurement. The oxide film formed on the surface was analyzed using an XPS. The addition of HF led to an increase in the passive current density and critical current density and decreased the polarization resistance regardless of the alloys employed. Based on the composition of the oxide film, the compositional difference observed by the addition of HF was little, regardless of the nature of alloys. The Warburg impedance obtained by AC-impedance measurement indicates the dissolution of the constituents of CP-Ti and Ti-64 through a porous oxide film.

Change of pore structure and uniaxial compressive strength of sandstone under electrochemical coupling

  • Chai, Zhaoyun;Bai, Jinbo;Sun, Yaohui
    • Geomechanics and Engineering
    • /
    • v.17 no.2
    • /
    • pp.157-164
    • /
    • 2019
  • The effect of electrochemical modification of the physical and mechanical properties of sandstone from Paleozoic coal measure strata was investigated by means of liquid nitrogen physical adsorption, X-ray diffraction and uniaxial compressive strength (UCS) tests using purified water, 1 mol/L NaCl, 1 mol/L $CaCl_2$ and 1 mol/L $AlCl_3$ aqueous solution as electrolytes. Electrochemical corrosion of electrodes and wire leads occurred mainly in the anodic zone. After electrochemical modification, pore morphology showed little change in distribution, decrease in total pore specific surface area and volume, and increased average pore diameter. The total pore specific surface area in the anodic zone was greater than in the cathodic zone, but total pore volume was less. Mineralogical composition was unchanged by the modification. Changes in UCS were caused by a number of factors, including corrosion, weakening by aqueous solutions, and electrochemical cementation, and electrochemical cementation stronger than corrosion and weakening by aqueous solutions.

Electrochemical Characteristics of Nano-sized A2MnPO4F (A = Li, Na) as Cathode Materials for Lithium ion Batteries

  • Cho, Woosuk;Song, Jun Ho;Kim, Sang-Min;Kim, Dong-Jin;Kang, Min-Gu;Kim, Jeom-Soo;Kim, Young-Jun
    • Journal of Electrochemical Science and Technology
    • /
    • v.4 no.3
    • /
    • pp.113-118
    • /
    • 2013
  • Fluorophosphate, $Na_2MnPO_4F$ as new cathode material was synthesized by carbothermal treatment method. Prepared $Na_2MnPO_4F$ has particle size under 100 nm and residual carbon exists in surface of $Na_2MnPO_4F$. Additional carbon coating was performed in order to increase the electrochemical properties. Even capacity and overpotential were improved by carbon coating using mechanical ball milling, the reduced crystallinity limited the drastic improvement of the electrochemical properties. To solve this problem, re-heat treatment was involved to recover crystallinity and then notable improvement of electrochemical properties was obtained. Specific amount of $Li^+$ that participates in electrochemical $Li^+$ insertion / extraction reaction, was x = 1 in $Li_xNa_{2-x}MnPO_4F$ within the voltage range of 2.0 to 4.8 V. The doubled capacity by 2 electron reaction can be obtained when NMPF is charged to higher voltage over 4.8 V.