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SUPERVISOR
Ahmad Rezaian,Mohammad Zhiani,Hossein Edris
احمد رضائيان (استاد راهنما) محمد ژياني (استاد مشاور) حسين ادريس (استاد راهنما)
 
STUDENT
Farhad Madadi
فرهاد مددي

FACULTY - DEPARTMENT

دانشکده مهندسی مواد
DEGREE
Doctor of Philosophy (PhD)
YEAR
1391

TITLE

Performance evaluation of NiCr, NiCrBSi and NiCoCrAlY coatings on Aluminum bipolar plates in polymer exchange membrane fuel cell.
The effect of surface roughness on wettability of different coating materials on bipolar plates employed in proton exchange membrane fuel cells (PEMFC) was investigated in this study. Aluminum substrate was coated with three different materials (NiCr, NiCrBSi, and Co(Ni)CrAlY) using high velocity oxy fuel (HVOF) process. Surface topology and roughness were then evaluated using atomic force microscopy and roughness profilometer. Moreover, the contact angle (CA) of different coatings was measured both in as-sprayed condition and after grinding in order to investigate the influence of roughness on the surface hydrophobicity parameter. It was found that among the three coatings with hydrophobic nature, NiCrBSi and Co(Ni)CrAlY showed the highest (128?) and the lowest (106?) CAs, respectively, whereas the CA of the uncoated Aluminum was determined to be 84? showing the hydrophilic nature of the substrate. The surface roughness of NiCrBSi, Co(Ni)CrAlY and NiCr were Ra = 7.632 µm, Ra = 5.510 µm and Ra =5.974, respectively. It shows that NiCrBSi and Co(Ni)CrAlY exhibited the highest and lowest surface roughness. It was also found that for all coating materials, power-current curves of the single cells illustrated a rising trend in power with increasing relative humidity from 30% to 100%. Such behavior was found to be due to the hydrophobic property of the coated surfaces through the removal of the produced water. This in turn prevented water blocking and flooding known as fuel cell performance and durability weakness points.. Among the sprayed coating materials used in this study, NiCrBSi exhibited the highest hydrophobic property, and hence, the greatest cell performance.
اثر پوشش هاي آب گريز اعمال شده به روش پاشش حرارتي بر روي صفحات دوقطبي پيل هاي سوختي پليمري و مطالعه تاثير آن ها بر عملکرد پيل سوختي در اين پژوهش مورد ارزيابي قرار گرفت. با استفاده از روش پاشش حرارتي، سه پوشش با ترکيب, NiCr، NiCrBSi و Co (Ni)CrAlY بر روي سطوح زيرلايه از جنس آلومينيوم خالص اعمال گرديد. آزمون هاي مختلفي نظير طيف نگار توزيع انرژي و مطالعه ساختار توسط پراش پرتو ايکس، مقاومت تماسي، ترشوندگي، مقاومت خوردگي شامل آزمون پلاريزاسيون تافل و طيف سنج امپدانس الکتروشيميايي، زبري سنجي، بررسي مورفولوژي و توپوگرافي سطح، آزمون هاي پلاريزاسيون پيل سوختي و همچنين آزمون شبيه سازي پايداري پيل به جهت بررسي و ارزيابي عملکرد پوشش هاي صفحات دوقطبي نمونه هايي انجام شد. بررسي تاثير سطوح آب گريز بر روي توان خروجي پيل در رطوبت هاي نسبي متفاوت و مقايسه آن با پيل سوختي استاندارد نيز صورت گرفت. مجموع نتايج حاصل نشان داد که پوشش NiCrBSi به جهت بيشترين تطابق با شرايط عملياتي پيل سوختي، بهترين گزينه براي پوشش سطح صفحات دوقطبي مي باشد.

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