الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Direct methanol fuel cells (DMFCs), which use methanol as the fuel, have many advantages over other fuel cell systems because methanol has a high energy density and is liquid at room temperature. DMFC has paid considerable attention and developed very quickly because of the abundance source, low price, safe transportation, and storage of methanol, and, therefore, it is attractive for portable applications such as laptops and mobile phones, However, DMFC still has some problems that need to be solved. One is the methanol crossover from the anode side to the cathode through the mostly used Nafion membranes. That led to lowering the efficiency of the cells as a result of fuel losses at the anode and mixed potential formed by methanol oxidation at the cathode. Firstly, grafting of (2-acryloyamido-2-methylpropane sulfonic acid-co-methyl methacrylate) onto the cellulose acetate chains using potassium per sulphate as initiator and the resulted grafted membranes were categorized as CA-g-P(AMPS-co-MMA) membranes. Further, the fabricated membranes were then characterized using various analysis tools such as FT-IR, H-NMR, XRD, TGA, DSC, SEM, AFM, and EDX to provide the success of the grafting process. Factors affecting the grafting process including; concentration of cellulose acetate, initiator concentration, comonomer concentration and composition, reaction time, and temperature were studied and their impact on the grafting parameters such as grafting efficiency (GE%), grafting yield (GY%), and add-on (%) was also investigated. Finally, the optimized CA-g-P(AMPS-co-MMA) membranes were evaluated and experimented as alternative PEM. Fuel cell properties such as water and methanol uptake, dimensional stability, contact angle measurements, ion exchange capacity (IEC), mechanical properties, thermal oxidation stability, methanol permeability, surface roughness, optical properties, proton conductivity, and membrane performance were investigated.This thesis is divided into four major chapters:Chapter one: Introduction, which focuses on providing a quick overview of the fuel cells.Chapter two: discusses the ory and varieties of fuel cells, the operation of DMFCs, and the polymer electrolyte membranes used in DMFCs.Chapter three: Describes materials, experimental procedures and techniques used in the processes of preparation, characterisation, and evaluation.Chapter four: Result and discussion, presenting the obtained results as follow:o Part 1: preparation and characterization of CA, P(AMPS-co-MMA) and CA-g-P(AMPS-co-MMA). Part 2: examining the variables that influence the grafting process. Part 3: evaluation of grafted membranes for DMFC applications.The study discovered the following results: All grafted membranes exhibit excellent thermal oxidative stability at elevated temperatures (up to 80 °C) and thermal stability as determined by TGA results. As a result, the IEC reach its maximum value of 6.7 (meq/g) at an add-on percentage of 70%. The grafted membrane has a methanol permeability of (8.071×10-8 cm2.s-1), compared to 85.9 10-7 and 24.9 10-7 in case of CA and Nafion® 212 membranes, respectively. The developed membrane’s proton conductivity was found to be superior to that of the pristine CA membrane and increased with increasing graft PAMPS, moderate water uptake (27%), to reach maximum value (6.44×10-3 S/cm) at the ambient temperature compared with the pristine CA membrane (0.035×10-3 S.cm-1) the calculated T50 (the temperature needed to lose 50% of the original weight), was shifted from 360.85 °C in case of CA membrane to 302.72 °C in the case of CA-g-(AMPS-co-MMA) membrane. This thermal stability is quite enough for DMFCs, which are usually operated at the temperature of lower than 200 °C. Based on the studying grafting parameters the selected Optimal conditions (to obtain the max. possible IEC) for DMFCs are 15% CA, reaction time; 9 h, KPS concentration; 0.1M and 1:1 M ratio of AMPS/MMA, 15wt/v% co-monomer concentration, 9:6 comonomer composition at 55 °C These previous results indicate that the CA-g-P(AMPS-co-MMA) membrane exhibited superior characteristics, making it a great alternative for the high-cost commercial Nafion membrane in DMFC applications.