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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/64973


    Title: Blends of shape-stabilized poly(ethylene glycol)/silica Fume composites as tunable sustained release phase change materials
    Authors: 李昀;Lee,Yun
    Contributors: 化學工程與材料工程學系
    Keywords: 相轉移材料;聚乙二醇;燻矽;phase change materials;poly(ethylene glycol);silica fume
    Date: 2014-07-24
    Issue Date: 2014-10-15 14:37:14 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本篇研究主要目的是找到固-液轉換上型態穩定的相轉移材料,聚乙二醇/燻矽複合物,它不僅有較寬廣的結晶溫度範圍而且具有毛細管作用力可使得聚乙二醇在液態時並不會從孔洞內流出,這樣的結果可應用在更廣的能源儲存上。
    固-液轉換上型態穩定的相轉移材料,利用含浸法製備聚乙二醇/燻矽複合物,以不同重量比例的聚乙二醇負載於燻矽載體上。結果發現,負載較少的聚乙二醇 (25%) 於燻矽載體上,會明顯的看到結晶溫度變得比較寬廣不像純的聚乙二醇有很精準的結晶溫度。因為燻矽載體孔內有牆壁效應會影響聚乙二醇在孔洞內的結晶行為。使得靠近牆壁的聚乙二醇無法結晶成為非晶相,只有遠離牆壁的聚乙二醇不受牆壁影響能順利結晶。所以負載較少的聚乙二醇的結晶性比較差,導致其有較寬廣的結晶溫度約為攝氏24.1至-4.2度且結晶點也較低約為攝氏12度。然而負載較高(75%)的複合物擁有較多遠離牆壁的聚乙二醇結晶使得其結晶行為與純的聚乙二醇相似,其結晶溫度範圍約為攝氏41.7至12.8度。
    因此,若我們想要調製寬廣的固-液轉換上型態穩定的相轉移材料,只需要混摻25%的複合物及75%的複合物。25%的複合物及75%的複合物以不同重量比例混摻1:3、1:5及1:8。我們猜測大量的25%複合物會把少量的75%複合物給包圍。使得在降溫過程中至攝氏41度時,75%的複合物應該要開始放熱結晶,但因為被大量的25%複合物所包圍,使得熱無法很快地傳遞出去。隨著溫度持續下降,驅動力的不足使冷卻速率下降,而影響了75%複合物的結晶速率,當溫度在持續下探至攝氏24度時也到達了25%複合物開始放熱結晶的溫度,所以混摻後的複合物有更寬廣的結晶溫度行為約為攝氏35.2至-5.4度。
    再者,這樣的一個混摻行為即可得到較寬廣的結晶溫度範圍。那麼將25%複合物改成低成本的燻矽載體也會有相同的影響。75%的複合物與燻矽載體以不同比例混摻1:1及1:2。同樣的,我們猜測大量的燻矽會把少量的75%複合物給包圍,而熱被包圍無法很快地傳遞出去。隨著溫度持續下降,驅動力的不足使冷卻速率下降,也影響了75%的複合物的結晶速率,其結晶溫度範圍為攝氏36.9至-2.2度。
    我們期待這樣的混摻方式,使得廣泛的結晶溫度範圍在儲能方面能有更多的價值。
    ;The aim of this thesis was to prepare a solid-liquid shape-stabilized phase change materials (PCMs), polyethylene glycol/silica fume (PEG/SF) composite, which not only had a broad PEG crystallization temperature range for more suitable thermal energy storage applications but also had the melted PEG retained in porous SF through the capillary force of the pore.
    Shape-stabilized PEG/SF composites with various weight ratios of PEG from 5 to 75% were prepared by the impregnation method. As the results, the wall-effect of SF had caused a broad phase transition temperature range going from 24.1o to -4.2oC and lowered the crystallization point to about 12oC for PEG in the PEG25/SF composite. A higher weight ratio of PEG could have made more PEG crystallize in the SF pore and the crystallization temperature range going from 41.7o to 12.8oC was close to the pure PEG in the PEG75/SF composite. Moreover, blends of PEG75/SF composite and PEG25/SF composite by weight ratios of 1:3, 1:5 and 1:8 were prepared to produce tunable sustained heat release PCMs. The PEG25/SF composites in large had encompassed the PEG75/SF composites. So, the heat release from the partial crystallization of PEG in the PEG75/SF composite initially could not be totally transferred due to the insulation of the PEG25/SF composites and the small driving force of the temperature difference had slowed down the heat transfer rate within the PEG75/SF composite. So, the crystallization rate of PEG in the PEG75/SF composite was also slowed down. Consequently, the blended materials exhibited a broad crystallization temperature range going from 35.2o to -5.4oC. Finally, we also used the low-cost SF powders to replace the PEG25/SF composite to form physical blends with the PEG75/SF composite to broaden the crystallization temperature range going from 36.9o to -2.2oC which could also have applications in thermal energy storage.
    Appears in Collections:[化學工程與材料工程研究所] 博碩士論文

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