As the world turns its eye to the adverse effects of burning fossil fuels in our everyday application, the search for alternative, sustainable and renewable sources of energy is of high interest. Among these, Proton Exchange Membrane Fuel Cells (PEMFCs) are receiving considerable attention. DuPont's perfluorosulfonic acid membrane (Nafion) is the current most successful membrane for PEMFCs. Nafion depends solely on the presence of water molecules necessary for proton conduction [1]. Its conductivity is around 0.1 S cm-1 [2]. PEMFCs usually operate at temperatures around 80 ?C [2]. Increasing the operating temperature (T>1200C) enhances the fuel cell performance in many ways: It increases the kinetics of the redox reactions, reduces catalyst poisoning by CO, higher chance of recovering useful heat as well as solving the problem of accumulated water in the cathode [3,4]. However, high temperature operation is not permitted with the current perfluorosulfonic acid (Nafion) membrane. It dehydrates at temperatures higher than 100 ?C and its proton conductivity dramatically decreases. For example, , Nafion conductivity decreases from 0.066 to 0.00014 S cm-1 at 30?C when the relative humidity (RH) decreases from 100% to 34% [5]. Furthermore, the low glass transition temperature of Nafion (110 ?C) is problematic because above this point the polymer loses its mechanical stability and degradation eventually occurs [6]. Several studies were performed in the literature to either modify existing Nafion membranes or develop a new class of membranes as alternatives for Nafion. Solid proton conductors were proposed in this research. Zirconium phosphate (ZrP) was investigated as a proton conducting material [7]. Zirconium Phosphate was modified with Glycerol. ZrP was prepared by the reaction of Zirconium oxychloride solutions with phosphoric acid. Glycerol was used to modify the ZrP material. The modified ZrP material was then evaluated for proton conductivity using Electrochemical Impedance Spectroscopy (EIS). The preliminary experimental results indicated a higher conductivity compared to the modified ZrP on its own and that is mainly due to the addition glycerol. The second stage of the experimental work will focus on the synthesis of composite membranes based on ZrP and Glycerol. Polyaniline (PANI) and polytetrafluoroethylene (PTFE) are proposed as polymer supports. Polyaniline is a hydrophobic good conducting polymer that is formed from the polymerization of aniline followed by doping with sodium dodecyl sulfate (SDS) to modify its morphology and make it hydrophilic [8]. Initially, the polymerization of polyaniline on polytetrafluoroethylene (PTFE) alone has been conducted and promising conductivity results were obtained in the order of 10-5 S cm-1. Future work will aim at investigating ZrP. Glycerol and PANI supported on PTFE.
CRGO-CuFe2O4 was prepared using co-precipitation method and annealed at 400 oC and 500 oC. The prepared ferrites were characterized using XRD, FTIR and SEM to investigate the catalysts structures, chemical composition, purity, morphology and particle size. The photocatalytic and non-photo-catalytic activity of the catalysts were tested toward phenol degradation using high phase liquid chromatography (HPLC) to measure the phenol and its by-products presented in the reaction system.
The first use of paper dates to 2nd Century (BC). The consumption of paper worldwide has increased by 400% in the past 40 years leading to a rise in deforestation and consequently the global warming. This research focuses on developing calcium carbonate (CaCO3)/polymer composite sheets (paper) instead of the traditionally used wood fiber-based paper with higher mechano-chemical durability. The main aim of this research is to optimize CaCO3 and polymer contents, and their processing conditions for continuous manufacturing of polymer-based papers. Herein, CaCO3/polymer composite sheets with different compositions and their characterization using differential scanning calorimeter and thermogravimetric analyzer, will be presented.
Solid particle erosion is considered as one of the major concerns in engineering applications which can lead eventually to failure of components and potentially result in hazardous catastrophic consequences. The present work aims to investigate erosion in the curved converging channel. The model consists of three modules: Fluid Transport, Particle Transport and Particle Erosion. For Fluid Transport, Reynolds-Averaged Navier-Stokes (RANS) equations with standard k-? turbulence model are used to model the flowing fluid. For Particle Transport, the particles are treated as dilute discrete phase and their trajectories are obtained through Discrete Particle Modeling (DPM). Turbulence dispersion and particle-wall rebound interaction are also modeled. Then for Particle Erosion, Oka erosion model is selected to compute the erosion rate. The results show that the maximum erosion rate increases sharply as the converging ratio decreases.
We propose an analytical model for a laminated beam consisting of a superelastic shape memory alloy (SMA) core layer bonded to two piezoelectric layers on its top and bottom surfaces. The model accounts for forward and reverse phase transformation between austenite and martensite during a full isothermal loading-unloading cycle starting a full austenite in the SMA layer. In particular, the laminated composite beam has a rectangular cross section and is fixed at one end while the other end is subjected to a concentrated transverse force acting at the tip. The momentcurvature relation is analytically derived. The generated electric displacement output from the piezoelectric layers is then determined using the linear piezoelectric theory. The results are compared to 3D simulations using finite element analysis (FEA). The comparison shows good agreement in terms of electric displacement, in general, throughout the loading cycle.
Carbon Fiber reinforced polymer (CFRP) composites are increasingly replacing metallic alloys in critical components of many applications. However, structural components made of composite materials often involve features such as drilled assembly holes. These induce stress concentrations in their vicinities and can reduce the overall load carrying capacity of the components. Damage resulting from such geometric features in CFRP composites has been extensively studied. Nevertheless, few works have investigated the behavior of notched CFRP composites under different environmental hazards. Accordingly, this work investigates the cooperative deteriorative effects of notches and moisture on CFRP composites. Tensile tests are conducted on aged and unaged samples with circular hole to assess the notch-moisture potential synergy. Digital Image Correlation technique is employed to measure the full-field strains during tests.
The demands for material with high strength to weight ratio is rapidly increasing. Sandwich structures are a group of composite material structures that are fabricated to have light weights, relatively high strengths and good dynamic properties. The purpose of this work is to optimize the performance of different configurations multilayer honeycomb structure including hexagonal, triangular and a combination of both, under out-of plane compressive and three-point-bending loadings. The optimization was conducted using ABQUS ISIGHT tool, which is a powerful optimization tool that uses the genetic algorithm optimization technique. The results showed that the single layers is the optimum configuration for buckling resistance in terms of magnitude, while increasing the number of layers influences the buckling modes regardless of the buckling load. Also, it was found out that increasing the number of layers increases the flexural rigidity of the structure.
Shape memory polymers (SMPs) continue to capture interest of the aerospace industry due to their unique properties. Compared to shape memory alloys, this class of smart materials is lighter in weight and can undergo significantly larger recoverable deformations. Despite significant work on characterizing mechanical and recovery properties of shape memory polymers, studies lack full field characterization of local recovery properties. In addition, the focus has been on SMPs having low transformation temperatures below 100 ?C. However, certain aerospace applications require SMPs with higher transformation temperatures to prevent undesirable actuation. This work aims to provide a full-field characterization technique to evaluate the recovery of a high temperature thermoset SMP.
This paper presents the wear behaviour of the AMC (reinforced with micro (5%, 10%) and nano (1%, 2%) particles) fabricated using stir casting process was investigated under different conditions of applied load (10N, 20N, and 30N), operation time (30 mins, 60 mins, 90 mins, and 120 mins). The analysis carried out at room temperature under the constant speed of 1450 rpm. The effectiveness of nanoparticles as compared to microparticles also satisfied by using the statistical technique. For optimization of wear parameters, Taguchi's method was used. An L27 Orthogonal array was selected for analysis of the output. Furthermore, a regression equation was developed for AMCs reinforced with nano and microparticles individually. The "smaller is better" characteristic was chosen as the objective of this model to analyse the wear resistance. From this research, it is observed that experiment time and applied load have the significant effect followed by SiC wt. % for microparticles, whereas for nanoparticles, experiment time and SiC wt. % have the significant effect followed by applied load. Finally, the experimental results were validated by the confirmation tests based on available experimental data.
Workplace learning is a concept that is gaining importance because of its effect on the employees and the organization as a whole. In parallel, employing persons with disabilities is at the forefront of the UAE government agenda, which necessitates the provision of equal opportunities of learning and development to all, including employees with disabilities. However, the definition of both learning in relation to performed tasks and assessment of the acquired learning are still not well tackled and thoroughly understood vis a vis employees with disabilities. This paper presents a case study of a male employee with cerebral palsy to explore his task- related learning and how it is assessed, in the context of a government organization in Dubai. The experience of the employee was analysed by means of interviews, and document analysis. The findings show positive development in the employee's learning because of the supervisor's and colleagues' roles, the thoroughness of assessment, and the consideration of the employee's strengths, weaknesses, and interests in the task planning. Further improvement could be achieved from applying more employee self-assessment and reflection; supervisor's training to a more facilitating role, and assessment of the physical, informational, and structural environment of the organization.
