• Title/Summary/Keyword: Ni-YSZ cermet

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Current Collector Effects on High Temperature Electrolysis by NI-YSZ Cermet Supported Solid Oxide Cells (집전체에 따른 NI-YSZ Cermet 기반의 가역적 고체산화물 연료전지를 이용한 고온 수증기 전기분해 특성)

  • Shin, Eui-Chol;Ahn, Pyung-An;Seo, Hyun-Ho;Lee, Jong-Sook;Yu, Ji-Haeng;Woo, Sang-Kuk
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.6
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    • pp.533-539
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    • 2010
  • Ni-YSZ supported button cells were prepared by spray-coating YSZ and screen-printing YSZ-LSM powder as an electrolyte and oxygen electrode on Ni-YSZ cermet disks. In order to identify the polarization loss mechanism in high temperature electrolysis current-voltage characteristics coupled with electrochemical impedance spectroscopy were investigated as a function of temperature, current load, and the humidity. The effects of the different current collectors of platinum and silver for oxygen electrodes were compared. With Ag current collector two polarization losses were distinguished. The high frequency component was attributed to the Ni-YSZ cermet which was less susceptible to temperature variation but increasing in loss with humidity. The lower frequency component was attributed to the LSM electrode. Platinum current collector led to a much lower polarization loss.

Characterization of Ni-YSZ cermet anode for SOFC prepared by glycine nitrate process (Glycine nitrate process에 의한 제조된 SOFC anode용 Ni-YSZ cermet의 물성)

  • Lee, Tae-Suk;Ko, Jung-Hoon;Lee, Kang-Sik;Kim, Bok-Hee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.21 no.1
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    • pp.21-26
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    • 2011
  • Ni-YSZ (Yttria Stabilized Zirconia) composite powders were fabricated by glycine nitrate process. The prepared powders were sintered at $1300{\sim}1400^{\circ}C$ for 4 h in air and reduced at $1000^{\circ}C$ for 2 h in a nitrogen and hydrogen atmosphere. The microstructure, electrical conductivity, thermal expansion and mechanical properties of the Ni-YSZ cermets have been investigated with respect to the volume contents of Ni. A porous microstructure consisting of homogeneously distributed Ni and YSZ phases together with well-connected grains was observed. It was found that the open porosity, electrical conductivity, thermal expansion and bending strength of the cermets are sensitive to the volume content of Ni. The Ni-YSZ cermet containing 40 vol% Ni was ascertained to be the optimum composition. This composition offers sufficient open porosity of more than 30 %, superior electrical conductivities of 917.4 S/cm at $1000^{\circ}C$ and a moderate average thermal expansion coefficient of $12.6{\times}10^{-6}^{\circ}C^{-1}$ between room temperature and $1000^{\circ}C$.

Preparation and characteristics of modified Ni/YSZ cermet for high temperature electrolysis (고온 수전해 전극용 modified Ni/YSZ cermet 제조 및 전극특성)

  • Chae, Ui-Seok;Park, Geun-Man;Hong, Hyeon-Seon;Choo, Soo-Tae;Yun, Yongseung
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.2
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    • pp.98-107
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    • 2004
  • Modified Ni/YSZ cermets for high temperature electrolysis were synthesized by dry or wet mechanical alloying methods. The Ni/YSZ composit particle was directly fabricated from the ball milling of Ni and YSZ powder or obtained from the reduction of NiO/YSZ particle after the ball milling of NiO and YSZ. In the case of the NiO/YSZ composite particle, the dry milling increased the average particle size whereas the wet milling decreased the size. The dry milling showed that fine YSZ particles were distributed over large Ni surfaces while Ni and YSZ particles similar in size were well mixed in the wet milling method. These features were the same in the Ni/YSZ composite particle prepared from Ni and YSZ powders. The electrical conductivity of the wet-milled Ni/YSZ cermet showed the highest value of $2{\times}10^2S/cm$ among the specimens and this value was increased to $1.4\times10^4S/cm$ after the sintering at $900^\circ{C}$ for 1 h.

Microstructural Characteristics of Ni/YSZ Cermet for High Temperature Electrolysis by Mechanical Alloying (기계적 합금화법으로 제조된 고온 수전해용 Ni/YSZ 전극의 미세구조 특성)

  • Park Keun-Man;Chae Ui-Seok;Hong Hyun Seon;Choo Soo-Tae
    • Korean Journal of Materials Research
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    • v.14 no.10
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    • pp.743-748
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    • 2004
  • Modified Ni/YSZ cermets for high temperature electrolysis were synthesized by the direct ball milling of Ni and YSZ powder. The ball milling was carried out in dry process and in ethanol with varying milling time. While the dry-milling decreased the average size from 65 to $80{\mu}m$, the wet-milling decreased the average size down to $10{\mu}m$. In addition, very fine particles less than $0.1{\mu}m$ were observed in the wet-milling condition. The subsequent process of cold-pressing and sintering at $900^{\circ}C$ for 2 h did not affect the particle size of dry-milled powder. The electrical conductivity of the dry-milled Ni/YSZ cermet showed the value of $5{\times}10^{2}\;S/cm$ and this value was increased to $1.4{\times}10^{4}\;S/cm$ after the sintering at $900^{\circ}C$ for 2 h.

Fabrication and Characterization of Cu-Ni- YSZ SOFC Anodes for Direct Utilization of Methane via Cu pulse plating (펄스 도금법에 의한 메탄연료 직접 사용을 위한 Cu-Ni-YSZ SOFC 연료극 제조 및 특성평가)

  • Park, Eon-Woo;Moon, Hwan;Lee, Jong-Jin;Hyun, Sang-Hoon
    • Journal of the Korean Ceramic Society
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    • v.45 no.12
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    • pp.807-814
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    • 2008
  • The Cu-Ni-YSZ cermet anodes for direct use of methane in solid oxide fuel cells have been fabricated by electroplating Cu into the porous Ni-YSZ cermet anode. The uniform distribution of Cu in the Ni-YSZ anode could be obtained via pulse electroplating in the aqueous solution mixture of $CuSO_4{\cdot}5H_{2}O$ and ${H_2}{SO_4}$ for 30 min with 0.05 A of average applied current. The power density ($0.17\;Wcm^{-2}$) of a single cell with a Cu-Ni-YSZ anode was shown to be slightly lower in methane at $700^{\circ}C$, compared with the power density ($0.28\;Wcm^{-2}$) of a single cell with a Ni-YSZ anode. However, the performance of the Ni-YSZ anode-supported single cell was abruptly degraded over 21 h because of carbon deposition, whereas the Cu-Ni-YSZ anode-supported single cell showed the enhanced durability upto 52 h.

Electrochemical Properties of Segmented-in-series SOFC Using Ni-Fe/YSZ Core-shell Anode (Ni-Fe/YSZ 코어-쉘 구조 연료극을 사용한 다전지식 고체산화물 연료전지의 전기화학적 특성)

  • An, Yong-Tae;Ji, Mi-Jung;Hwang, Hae-Jin;Lee, Min-Jin;Hong, Sun-Ki;Kang, Young-Jin;Choi, Byung-Hyun
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.357-361
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    • 2014
  • An Ni-Fe/YSZ core-shell structured anode for uniform microstructure and catalytic activity was synthesized. Flat tubular segmented-in-series solid oxide fuel cell-stacks were prepared by decalcomania method using synthesized anode powder. The Ni-Fe/YSZ core-shell anode exhibited better electrical conductivity than a commercially available Ni-YSZ cermet anode. Also power output increased by 1.3 times with a higher open circuit voltage. These results can be attributed to the uniformly distributed Ni particles in the YSZ framework. The impedance spectra of a Ni-Fe/YSZ core-shell anode showed comparable reduced ohmic resistance similar to those of the commercially available Ni-YSZ cermet anodes.

Synthesis of Ni-YSZ cermets for SOFC by glycine nitrate process (Glycine nitrate process에 의한 SOFC용 Ni-YSZ cermets 제조)

  • Lee, Tae-Suk;Ko, Jung-Hoon;Kim, Bok-Hee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.20 no.6
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    • pp.289-294
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    • 2010
  • Ni-YSZ (Yttria Stabilized Zirconia) composite powders for SOFC were fabricated by glycine nitrate process. $ZrO(NO_3)_2{\cdot}2H_2O$, $Y(NO_3)_3{\cdot}6H_2O$, $Ni(NO_3)_2{\cdot}6H_2O$ and glycine were chosen as the starting materials. The structural properties of the sintered Ni-YSZ cermets have been investigated with respect to the volume contents of Ni. A porous microstructure consisting of homogeneously distributed Ni and YSZ phases together with well-connected grains was observed. The sintered Ni-YSZ cermets showed a porous microstructure consists of homogeneously distributed Ni and YSZ phases and the grains were well-connected. It was found that the open porosity is sensitive to the volume content of Ni. The Ni-YSZ cermet containing 35 vol% Ni seems to be suitable for the electrode material of SOFC since it provides sufficient open porosity higher than 30%.

Characteristics of Ni/YSZ Cermet Prepared by Mechanical Alloying Method for the High Temperature Electrolysis of Steam

  • Choo, Soo-Tae;Kang, Kyoung-Hoon;Chae, Ui-Seok;Hong, Hyun-Seon;Hwang, Kab-Jin;Bae, Ki-Kwang;Shin, Seock-Jae
    • Journal of the Korean Ceramic Society
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    • v.43 no.12 s.295
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    • pp.764-767
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    • 2006
  • Ni/YSZ $(Y_2O_3-stabilized\;ZrO_2)$ composite as an electrode component for High Temperature Electrolysis (HTE) was fabricated by mechanical alloying method using Ni and YSZ powders. Characterization of the synthesized composite was investigated with various analysis tools, including XRD, SEM and PSA, and a self-supporting planar unit cell prepared with the Ni/YSZ composite was prepared to study the electrochemical reactions for the production of hydrogen. The Ni/YSZ cermet is composed of crystalline Ni and YSZ, in a sub-micro scale, and has an even distribution without aggregated particles. In addition, under an electrochemical reaction, the unit cell showed an $H_2$ evolution rate from steam of 14 Nml/min and $600mA/cm^2$ of current density at the electrode.

Morphologies of Brazed NiO-YSZ/316 Stainless Steel Using B-Ni2 Brazing Filler Alloy in a Solid Oxide Fuel Cell System

  • Lee, Sung-Kyu;Kang, Kyoung-Hoon;Hong, Hyun-Seon;Woo, Sang-Kook
    • Journal of Powder Materials
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    • v.18 no.5
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    • pp.430-436
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    • 2011
  • Joining of NiO-YSZ to 316 stainless steel was carried out with B-Ni2 brazing alloy (3 wt% Fe, 4.5 wt% Si, 3.2 wt% B, 7 wt% Cr, Ni-balance, m.p. 971-$999^{\circ}C$) to seal the NiO-YSZ anode/316 stainless steel interconnect structure in a SOFC. In the present research, interfacial (chemical) reactions during brazing at the NiO-YSZ/316 stainless steel interconnect were enhanced by the two processing methods, a) addition of an electroless nickel plate to NiO-YSZ as a coating or b) deposition of titanium layer onto NiO-YSZ by magnetron plasma sputtering method, with process variables and procedures optimized during the pre-processing. Brazing was performed in a cold-wall vacuum furnace at $1080^{\circ}C$. Post-brazing interfacial morphologies between NiO-YSZ and 316 stainless steel were examined by SEM and EDS methods. The results indicate that B-Ni2 brazing filler alloy was fused fully during brazing and continuous interfacial layer formation depended on the method of pre-coating NiO-YSZ. The inter-diffusion of elements was promoted by titanium-deposition: the diffusion reaction thickness of the interfacial area was reduced to less than 5 ${\mu}m$ compared to 100 ${\mu}m$ for electroless nickel-deposited NiO-YSZ cermet.