Nano-CeO₂ and -LaCrO₃ dispersed ferritic stainless steels as potential interconnect materials for solid oxide fuel cells

Mehran, Muhammad Taqi,Khan, Muhammad Shirjeel,Lee, Jung-Won,Song, Rak-Hyun,Lee, Seung-Bok,Lee, Jong-Won,Lim, Tak-Hyoung,Park, Seok-Joo Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.709 No.-

<P><B>Abstract</B></P> <P>Novel nano-oxide dispersed ferritic stainless steel alloys have been developed as potential interconnect materials for solid oxide fuel cells. Nanopowders of CeO<SUB>2</SUB> and LaCrO<SUB>3</SUB> were mixed with ferritic stainless steel powder (SUS430) using conventional ball milling. Rectangular pellets were prepared and sintered at 1400 °C in pure H<SUB>2</SUB>. The microstructural analysis of the sintered pellets showed a uniform distribution of oxide particles. Long-term area specific resistance (ASR) of the pellets was monitored using the four-probe DC method at 800 °C for 1000 h in air, revealing that an increase in the CeO<SUB>2</SUB> amount from 0.5 to 3 and 5 wt % increased the oxidation resistance of the steel. ASR values as low 32.2 and 5.5 mΩ cm<SUP>2</SUP> were observed, respectively, for 3 and 5 wt % nano-CeO<SUB>2</SUB> dispersed SUS430 steel. However, in the case of LaCrO<SUB>3</SUB> addition, no such relationship between the oxidation resistance and LaCrO<SUB>3</SUB> concentration was found. This study showed that the dispersed nano-CeO<SUB>2</SUB> particles effectively reduced the Cr<SUB>2</SUB>O<SUB>3</SUB> scale growth, likely by retarding the inward diffusion of oxygen, hence resulting in a high oxidation resistance at the SOFC operating conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The nano-oxide dispersed ferritic steels were developed for SOFC interconnects. </LI> <LI> The alloys showed uniform distribution of oxides present at grain boundary. </LI> <LI> 5 wt% nano-CeO<SUB>2</SUB> dispersed SUS430 showed lower ASR after 1000 h test at 800 °C. </LI> <LI> The dispersed oxide improved oxidation and electrical properties of the alloys. </LI> <LI> Especially, nano-CeO<SUB>2</SUB> dispersed steel is a good candidate of SOFC interconnects. </LI> </UL> </P>

Effects of applied current density and thermal cycling on the degradation of a solid oxide fuel cell cathode

Khan, Muhammad Zubair,Mehran, Muhammad Taqi,Song, Rak-Hyun,Lee, Seung-Bok,Lim, Tak-Hyoung Elsevier 2018 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.43 No.27

<P><B>Abstract</B></P> <P>Effects of applied current density and thermal cycles on the durability of a solid oxide fuel cell (SOFC) cathode have been studied. SOFC half-cells with and without a gadolinium-doped ceria (GDC) interlayer were fabricated and tested for 1000 h at 900 °C under various current densities and thermal cycles. Performance degradation of the half-cells was assessed by increment of the area specific resistance (ASR). Initially, the ASR of the half-cells without the GDC interlayer decreased for around 150 h due to cathode activation and thereafter increased. A rapid increase in the ASR was observed at higher applied current density, which is attributed to delamination of the electrolyte/cathode interface due to the formation of Sr zirconates, and microstructural change in the cathode. However, these adverse effects were prevented by the GDC interlayer. The half-cells with the GDC interlayer exhibited a smaller degradation rate as compared to that without the GDC interlayer. During the thermal cycling test, ASR values of all GDC interlayer thickness cells increased with an increasing number of thermal cycles. The thermally cycled cell with a GDC interlayer thickness of 3.4 μm showed a lower degradation rate due to the dense GDC interlayer, which resulted in less interfacial resistance and prevented elemental diffusion towards the electrolyte. However, the half-cells with GDC interlayer thickness of 2.4 and 4.5 μm showed a higher increase in the ASR due to relatively higher Sr diffusion and delamination of the cathode/GDC interlayer interface, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A rapid degradation was observed at higher applied current density. </LI> <LI> The adverse effects of the applied current were prevented by the GDC interlayer. </LI> <LI> Degradation of the cells increased with increasing number of thermal cycles. </LI> <LI> Performance degradation of the cells was attributed to Sr diffusion and cathode delamination. </LI> </UL> </P>

Improving sulfur tolerance of Ni-YSZ anodes of solid oxide fuel cells by optimization of microstructure and operating conditions

Mehran, Muhammad Taqi,Khan, Muhammad Zubair,Lee, Seung-Bok,Lim, Tak-Hyoung,Park, Sam,Song, Rak-Hyun Elsevier 2018 International journal of hydrogen energy Vol.43 No.24

<P><B>Abstract</B></P> <P>In this study, we propose an improvement in the sulfur tolerance of nickel-yttria stabilized zirconia (Ni-YSZ) anodes for solid oxide fuel cells (SOFCs) by simultaneously employing optimized operating conditions and microstructural modifications. An electrolyte supported SOFC is operated at 20 ppm H<SUB>2</SUB>S impurity at 750 °C for 20 h degradation and 10 h recovery test. The current cycles with a higher amplitude and small pulse time during the constant current operation are beneficial for the mitigation of sulfur poisoning. The effect of humidity on the sulfur degradation of Ni-YSZ anode is also studied. The synergetic effect of microstructure modification and current cycling conditions improves the sulfur tolerance of Ni-YSZ anode. It has been found that, when an anode with a modified microstructure by infiltrated CeO<SUB>2</SUB> and Yb<SUB>2</SUB>O<SUB>3</SUB> nanoparticles is operated on 20 ppm H<SUB>2</SUB>S poisoned gas at 10% relative humidity and the optimum pulsed current cycling conditions, about 7 times less degradation of the SOFC performance is observed. This study shows that at lower H<SUB>2</SUB>S concentration, a stable operation of a SOFC with minimum degradation can be achieved with the combination of optimization of operating conditions and modification of the anode microstructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sulfur tolerance of Ni-YSZ anodes improved by a novel method. </LI> <LI> Pulsed current cycles at specific intervals regenerates sulfur poisoned Ni in anode. </LI> <LI> Uniform surface modification of anode by infiltration of CeO<SUB>2</SUB> Yb<SUB>2</SUB>O<SUB>3</SUB> nano-particles. </LI> <LI> Optimized conditions show 7 times improvement in sulfur tolerance of Ni-YSZ anodes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A simplified approach to predict performance degradation of a solid oxide fuel cell anode

Khan, Muhammad Zubair,Mehran, Muhammad Taqi,Song, Rak-Hyun,Lee, Jong-Won,Lee, Seung-Bok,Lim, Tak-Hyoung Elsevier 2018 Journal of Power Sources Vol.391 No.-

<P><B>Abstract</B></P> <P>The agglomeration of nickel (Ni) particles in a Ni-cermet anode is a significant degradation phenomenon for solid oxide fuel cells (SOFCs). This work aims to predict the performance degradation of SOFCs due to Ni grain growth by using a simplified approach. Accelerated aging of Ni-scandia stabilized zirconia (SSZ) as an SOFC anode is carried out at 900 °C and subsequent microstructural evolution is investigated every 100 h up to 1000 h using scanning electron microscopy (SEM). The resulting morphological changes are quantified using a two-dimensional image analysis technique that yields the particle size, phase proportion, and triple phase boundary (TPB) point distribution. The electrochemical properties of an anode-supported SOFC are characterized using electrochemical impedance spectroscopy (EIS). The changes of particle size and TPB length in the anode as a function of time are in excellent agreement with the power-law coarsening model. This model is further combined with an electrochemical model to predict the changes in the anode polarization resistance. The predicted polarization resistances are in good agreement with the experimentally obtained values. This model for prediction of anode lifetime provides deep insight into the time-dependent Ni agglomeration behavior and its impact on the electrochemical performance degradation of the SOFC anode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Life-time prediction model of SOFC anode is developed and experimentally validated. </LI> <LI> Performance degradation of SOFC due to Ni grain growth is predicted. </LI> <LI> Ni particles growth and TPB length reduction fits well with the prediction model. </LI> <LI> Results of study discriminate degradation associated with Ni particles coarsening. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of GDC interlayer thickness on durability of solid oxide fuel cell cathode

Khan, M.Z.,Mehran, M.T.,Song, R.H.,Lee, J.W.,Lee, S.B.,Lim, T.H.,Park, S.J. Ceramurgica ; Elsevier Science Ltd 2016 Ceramics international Vol.42 No.6

Long-term performance degradation of solid oxide fuel cell (SOFC) cathode as a function of gadolinium doped ceria (GDC) interlayer thickness has been studied under accelerated operating conditions. For this purpose, SOFC half-cells with GDC interlayer thicknesses of 2.4, 3.4 and 6.0@?m were fabricated and tested for 1000h at 900<SUP>o</SUP>C under constant current density of 1A/cm<SUP>2</SUP>. The half-cells consisted of lanthanum strontium cobalt ferrite (LSCF)/GDC composite cathode, GDC interlayer, scandia-ceria stabilized zirconia electrolyte and platinum anode as a counter electrode. Area specific resistance (ASR) of the half-cells was continuously measured over time. Higher increase in ASR was observed for the half-cells with GDC interlayer thickness of 2.4 and 6.0@?m, which is attributed to higher strontium (Sr) diffusion towards electrolyte and to cathode/GDC interface delamination coupled with small Sr diffusion, respectively. However, half-cell with GDC interlayer thickness of 3.4@?m showed smaller degradation rate due to highly dense GDC interlayer which had less interfacial resistance and suppressed Sr diffusion towards electrolyte.

Effect of nano-Al₂O₃ addition on mechanical durability of nickel-yttria stabilized zirconia anode support of solid oxide fuel cells

Mehran, Muhammad Taqi,Khan, Muhammad Zubair,Lim, Tak-Hyoung,Lee, Seung-Bok,Song, Rak-Hyun Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.12

<P><B>Abstract</B></P> <P>For anode supported solid oxide fuel cells (SOFCs), the strength and durability of the porous cermet support during long-term operation is critical for the reliability of the cells and stacks. The effect of adding nano-Al<SUB>2</SUB>O<SUB>3</SUB> on the long-term durability of the mechanical strength of nickel-yttria stabilized zirconia (Ni-YSZ) based SOFC anode supports was investigated in this study. The SOFC anode support materials, Ni-3YSZ (3 mol% YSZ), Ni-8YSZ (8 mol% YSZ), and nano-Al<SUB>2</SUB>O<SUB>3</SUB> added Ni-YSZ composites, were subjected to a long-term degradation test at 900 °C and 30% humidity in an H<SUB>2</SUB> environment and after 1000 h exposure, the flexural strength, phase, and microstructural changes were analyzed. The results suggest that the addition of nano-Al<SUB>2</SUB>O<SUB>3</SUB> to Ni-3YSZ improves the long-term strength and durability of the cermet while its addition to Ni-8YSZ cermet did not show any significant changes in the strength degradation behavior of the Ni-8YSZ based anode support. Further analysis by SEM and XRD shows that the tetragonal to monoclinic phase transformation in partially stabilized zirconia was suppressed due to the addition of nano-Al<SUB>2</SUB>O<SUB>3</SUB> in Ni-3YSZ resulting in improved long-term stability and higher mechanical strength. Replacing the Ni-8YSZ anode support with nano-Al<SUB>2</SUB>O<SUB>3</SUB> added Ni-3YSZ might significantly reduce the material cost of SOFCs without compromising long-term strength durability, thus bringing SOFCs a step closer to commercialization.</P>

EFFECT OF GDC INTERLAYER AND ITS THICKNESS ON THE LONG TERM STABILITY OF SOLID OXIDE FUEL CELL CATHODE

Muhammad Zubair Khan,Muhammad Taqi Mehran,Tak-Hyoung Lim,Rak-Hyun Song,Seung-Bok Lee,Jong-Won Lee,Seok-Joo Park 한국신재생에너지학회 2015 AFORE Vol.2015 No.11

The relationship between reinforcing index and flexural parameters of new hybrid fiber reinforced slab

Mingli Cao,Chaopeng Xie,Li Li,Mehran Khan 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.5

In this paper, a new hybrid fiber system (NHFS) is investigated for the application of slab. The steel fiber, polyvinyl alcohol (PVA) fiber and calcium carbonate (CaCO3) whisker is added to form NHFS. The four-point bending test is carried out on the flexural properties of slab with plain, steel fiber, traditional hybrid fiber system (THFS) and NHFS reinforced cementitious composites. The flexural behavior is evaluated by ASTM C1018-97, JCI-SF4 and post-crack strength (PCS) technique. The evaluation parameters of flexural toughness such as toughness index (TI), equivalent flexural strength (EFS) and PCS are determined. The size of slab specimens is 15 mm (thickness)×50 mm (width)×200 mm (length). The results show that adding CaCO3 whisker to THFS can significantly improve the flexural strength, TI, EFS, PCS of the slab. The empirical relation between reinforcing index (RIv) and flexural parameters show that flexural parameters of slabs increase first and then decrease; which indicates that optimum RIv values can be helpful in the considering the mix design of steel-PVA fibers-CaCO3 whisker composites for achieving the desired flexural-related properties. The scanning electron microscopy is performed to observe the micro-morphological characteristics of the fracture surface, which proved the positive hybrid effect among the different fibers in cementitious composites. The NHFS can arrest the generation and propagation of the crack from micro to macro level.

Techno-Economic Analysis of Grid-Connected Hybrid Renewable Energy System for Remote Areas Electrification Using Homer Pro

Ur Rashid Mamoon,Ullah Irshad,Mehran Muhammad,Baharom M. N. R.,Khan Faisal 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

Pakistan is facing a drastic scarcity of electricity for the last two decades. Most of the areas in Pakistan have no access to electricity especially in Balochistan where most of the population has no electricity and water supply. Concerning the electricity issues, this research study is investigated to design a technical and economical hybrid system for the remote areas of Balochistan. For this purpose, three remote sites have been selected named Gujar village in district Awaran, Plantak in Washuk, and Shahrak village in Kech of Balochistan. Proposed sites are analyzed to fi nd the potential of renewable energy i.e. Wind and solar in the targeted sites of Balochistan. The wind and solar potential data are taken from the PMD, NREL, and NASA websites. For the selected sites, three models have been designed in Homer Pro software by using diff erent component combinations. These components include a fuel cell, generator, batteries, hydrogen tank, electrolyzer, Wind and Solar modules, and Converters. These models are connected to the grid to sell back the excess energy to the grid through net metering. After simulation and optimization, the most feasible and economic solution is decided that is based on NPC, COE, initial cost, and operating cost.