Hamimah Abd Rahman

Durability and Stability of LSCF Composite Cathode for Intermediate-Low Temperature of Solid Oxide Fuel Cell (IT-LT SOFC): Short Review

Solid oxide fuel cell (SOFC) is well known as power and heat generation device which converts chemical energy directly from fuel into electricity. SOFC operate at high temperature becomes obstacle for SOFC which reducing ionic conductivity material of current electrolyte, reduce lifetime of cell components, high fabrication cost, limited durability and performance issues. This introduce to environment pollution and decrease the SOFC lifetime. The fabrication of durability and stability composite cathode are comprised from mixing of perovskite La0.6Sr0.4CO0.2Fe0.8 (LSCF) powders with nanoscale ionically conducting ceramic electrolyte materials, SDC-carbonate (SDCc) was overcome this problems. Powder preparation and composite cathode fabrication must consider which as main factors in the development of durability and stability of LSCF-SDCc composite cathode. Powders must in nanoscale to enhance the conductivity and decrease the interfacial polarization resistance and the composite cathode should in nanoporous morphology for achieve high power density over than 500 h and remarkable durability. Calcination also plays in important role and its operations will effects to the SOFC durability and performance. The necessary to prolong the lifetime and increase the SOFC performance has lead to development of durability and stability of SOFC. This paper reviews the durability and stability of the composite cathode and focus on the challenges in material technology.

Pressure Drop Analysis of Square and Hexagonal Cells and its Effects on the Performance of Catalytic Converters

Stringent emission regulations around the world necessitate the use of high-efficiency catalytic converters in vehicle exhaust systems. Therefore, determining the optimum geometry of the honeycomb monolith structure is necessary. This structure requires a high surface area for treating gases while maintaining a low pressure drop in the engine. In the present paper, an adapted sub-grid scale modeling is used to predict the pressure loss of square- and hexagonal-cell-shaped honeycomb monoliths. This sub-grid scale modeling represents the actual variations in the pressure drop between the inlet and outlet for various combinations of wall thickness and cell density. A comparison is made between the experimental and numerical results established in literature. The present approach is found to provide better and more comprehensive results than the single channel technique.

Fabrication and Characterisation of La0.6Sr0.4Co0.2Fe0.8O3-δ-SDC Composite Cathode

Composite cathode is a promising material to be used as electrodes in fuel cells. The fabricated composite cathode materials in this study are comprised of a mixture of submicron La0.6Sr0.4Co0.2Fe0.8O3- (LSCF6428) powders with two types of nanoscale ionically conducting ceramic electrolyte materials, samarium-doped ceria (SDC) and SDC-carbonate (SDCc). 30 – 50 wt% of electrolyte materials are added to the LSCF6428 cathode via the solid state method. The composite powders were ball-milled in ethanol and calcined at the temperature range of 800°C to 900°C for 2 hours in air. The composite cathode powders are characterised in terms of morphology and crystal structure. It is found that after calcining, the LSCF and the electrolyte materials retained their original structures as there was no chemical reaction between the two components. In addition, the LSCF-SDC composite cathode powders were found to exhibit a narrower distribution in size compared to the LSCF-SDC carbonate powders.

The Effect of Milling Speed and Calcination Temperature towards Composite Cathode LSCF-SDC Carbonate

The effects of milling speed and calcinations temperature towards La0.6Sr0.4CO0.2Fe0.8O3-δ-SDC carbonate (LSCF-SDC carbonate) composite cathodes were investigated. The preparation of samarium-doped ceria (SDC) carbonate was firstly done by milling the SDC nanopowder with carbonate using the high-energy ball milling (HEBM) in air at room temperature. The obtained SDC carbonate was then used to mill with composite powder of lanthanum strontium cobalt ferrite (LSCF) which is one of the promising materials for the cathode of solid oxide fuel cells (SOFC). The purpose of milling LSCF composite powder with SDC carbonate was to get new composite cathode for intermediate-to low-temperature solid oxide fuel cells (IT-TLSOFC). LSCF composite powder with SDC carbonate was milled using high-energy ball milling with milling speed of 150 rpm and 550 rpm and calcinations temperatures of 750°C, 800°C, 850°C and 900°C. Field emission scanning electron microscopy (FESEM) analysis revealed the presence of large particle resulting from the increasing of calcinations temperature. FESEM also shows the particle size decrease in size with the increasing of milling speed. Therefore, the speed of 550 rpm and temperature of 900°C were found to be the best milling speed and calcinations temperature in producing the composite cathode of LSCF-SDC carbonate.

Electrophoretic Deposition of La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode Film on Stainless Steel Substrates

The electrophoretic deposition (EPD) of positively charged La0.6Sr0.4Co0.2Fe0.8O3-(LSCF6428) particles onto stainless steel 304 (SUS304) cathodes was performed by using 0.3-0.6 μm LSCF6428 particles dispersed in deionised water. Stable LSCF6428 aqueous suspensionwith 1 wt% of particles at pH 3 has been used for the deposition of the films. The sedimentationbehaviour of the LSCF6428 suspension in aqueous media was also studied. The deposition atapplied voltages between 3 and 7 V was found able to produce LSCF6428 films. The characteristicsof the electrophoretic deposition of those positively charged LSCF6428 particles onto SUS304cathode were investigated. The results show that the morphology and weight of the deposited filmsare affected by the applied voltage and deposition time of the EPD process.

Influence of Silver Addition on the Morphological and Thermal Characteristics of Nickel Oxide-Samarium Doped Ceria Carbonate (NiO-SDCC) Composite Anode

Addition of silver (Ag) as an electro-catalyst has been widely investigated to enhance the cathode performance for intermediate-to-low temperature SOFCs. Nevertheless, Ag is seldom incorporated into composite anode materials, especially for low temperature application. Therefore, this study aims to investigate the effects of small amount of Ag on the microstructure and thermal behaviour of NiO-SDC carbonate (NiO-SDCC) composite pellets. NiO-SDCC composite anode powder was prepared through fast milling method. Subsequently, small amount of Ag (1, 3, and 5 wt.%) was added into NiO-SDCC composite powder via ball milling. The pellets were manually pressed and sintered at 600 °C. Characterisation of the composite anodes include X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), dilatometry and porosity measurement. NiO-SDCC had maintained good chemical compatibility regardless of Ag loading. FTIR analysis also confirmed the existence of carbonates, suggesting Ag did not influence the carbonate bonding in all NiO-SDCC. Nonetheless, the porosity of all composite anodes was found within the acceptable range for good anodic performance (20-40%). The thermal expansion of the composite samples matched well with the SDCC electrolyte. This indicates the that addition of small Ag loading into NiO-SDCC is within the acceptable range that had demonstrated promising potential as LTSOFC composite anode.

Effects of Milling Speed and Calcination Temperature on the Phase Stability of Ba0.5Sr0.5Co0.8Fe3-δ

The phase instability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is widely reported in atmospheres containing carbon dioxide, which affects the long term electrochemical performance. The aim of this study is to investigate the phase stability of BSCF under the influence of milling and calcination temperature. Commercial BSCF powder was milled at 200 and 500 rpm and subsequently calcined at 750, 800 and 900 °C. The BSCF samples were characterized by using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). Secondary phases that were triggered after milling, however reduced with the increase of calcination temperature up to 800 °C. It was also found that the reduction of crystallite size and particle size at increased calcination temperature might be affected by the removal of these secondary carbonate phases. Moreover, the removal of carbonate was clearly evidenced in FTIR spectra by the reduction of carbonate signal intensities. In brief, a minimum calcination temperature of 900 °C was suggested for successful carbonate removal and recovery of single BSCF phase.

Assessment and Evaluation for Programme Learning Outcomes in Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia

Universiti Tun Hussein Onn Malaysia (UTHM) is the 15th of the 20 public universities established in Malaysia. UTHM consists of eight faculties. One of them is the Faculty of Mechanical and Manufacturing Engineering (FKMP). The programme offered – Bachelor of Mechanical Engineering with Honours (BDD), undergoes continuous auditing and accreditation by the Engineering Accreditation Council (EAC). To fulfill the requirement for accreditation, EAC requires the faculty to assess and evaluate the programme learning outcomes’ (PLOs) attainment of the graduates, such that all graduates are targeted to achieve the performance indicator (PI) upon graduation. This paper discusses the methods developed by the FKMP for PLOs’ measurement and evaluation. Two approaches are utilized in this regards, (i) the direct assessment based on students’ performance in courses, and (ii) the indirect assessment based the industrial and graduates’ perception. The PLOs’ attainment for graduates of cohort 2010-2012 are analysed in this study. Consolidation data shows that the PI for majority of the PLOs are achieved, indicating that the programme offered complies with the standard expected by different stakeholders.

Programme Learning Outcomes Assessment and Continuous Quality Improvement in Faculty of Mechanical and Manufacturing, UTHM

This paper describes the assessment and continuous quality improvement of Programme Learning Outcomes (PLOs) in the Faculty of Mechanical Engineering and Manufacturing. PLO is known as an elementary requirement in Outcome Based Education (OBE) system. All PLOs have been mapped with graduate attributes by EAC Manual 2012. Conceptual process for establishing and reviewing PLOs has been explained in the Plan-Check-Do-Act cycle. PLO assessment has been shown in different types which classified as direct and indirect methods. Continuous Quality Improvement has been extracted from a variety of assessment and has been discussed. Seven (7) CQIs are identified using different assessment methods of PLO during years 2013 to 2016 and subsequent improvement actions have been taken by the faculty within three years.

Morphological and Physical Behaviour of LSCF-SDCC-Ag Composite Cathode with the Incorporation of Ag as an Additive Element

The composite cathode, lanthanum strontium cobalt ferrite-samarium-doped ceria carbonate-argentum (LSCF–SDCC–Ag), was developed and investigated for low-temperature solid oxide fuel cell (LTSOFC) applications. This research studied the effect of Ag on the development and properties of the composite cathode. The composite cathode powders, LSCF– SDCC–Ag with an Ag addition of 1–5 wt% were developed via high energy ball milling technique, and all prepared pellets were sintered at 500, 550, and 600 °C. The morphological properties of the composite cathode powders were observed via FESEM micrograph, and the average particle sizes of the composite powders were measured via SmartTiff Software. The total porosity (%) of the LSCF–SDCC–Ag composite cathode pellets was determined using the Archimedes method. The FESEM micrograph revealed that the obtained composite cathode powder is homogeneous, with particle sizes of 100–200 nm. The particle size of the LSCF– SDCC–Ag cathode increased with the increase of Ag content. Meanwhile, the porosity decreased in value with the increase of the Ag content and the sintering temperature. The porosity percentage range from 26.6% to 33.8%.