羥基化鈦酸鋇漿料中有機添加劑之膠化與解膠化機制研究

Gelation and Degelation Mechanisms of Organic Additives in Hydroxylated BaTiO3 Aqueous Suspensions

張中璿(Chung-Hsuan Chang)

指導教授 ： 李嘉甄

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2014年)

摘要

水系鈦酸鋇(BaTiO3)漿料系統中搭配之黏結劑聚乙烯醇(PVA)與助熔劑氧化硼(B2O3)之間會產生交聯反應形成三維(three dimentional; 3-D)網狀凝膠態結構，進而使漿料形成不利於塗佈製程的高黏度膨脹性流體。藉由表面羥基化改質之鈦酸鋇粉末的使用，可避免 PVA 和 B2O3 之間的交聯反應，從而達到使水系漿料解膠之目的，並得到適於塗佈製程之較低黏度的牛頓流體。本研究主要由動態流變與 11B NMR 兩方面分別討論羥基化鈦酸鋇粉體與添加劑 PVA 和 B2O3 之間的交互作用，並深入探討羥基化鈦酸鋇可能存在之解膠化機制。實驗結果指出使羥基化鈦酸鋇水系漿料解膠的相關機制以下列三種型態為主：(1) 解離自 B2O3 之硼酸離子(B(OH)4-)於羥基化鈦酸鋇上的吸附量增加而減少其於水懸浮液中的自由濃度；(2) PVA 於羥基化鈦酸鋇上的吸附量增加而減少其於水懸浮液中的自由濃度；(3) 鈦酸鋇的羥基化造成水系漿料平衡 pH 值下降所致使之 B(OH)4-自由濃度減少。上述機制皆有抑制 PVA 和 B(OH)4-於水系懸浮液中發生交聯反應的作用，故可改善鈦酸鋇水系漿料的膠化現象。另一方面，本研究亦藉由理論計算求得各種解膠機制之解膠能力與其貢獻相對比例。

關鍵字

鈦酸鋇 ； 水系漿料 ； 聚乙烯醇 ； 氧化硼 ； 膠化 ； 解膠化

並列摘要

The gelation between PVA and B2O3 causes the aqueous BaTiO3 suspension to form a three-dimensional gel-like structure,resulting in a dilatant rheological behavior, which will harm the later process like slurry casting. The crosslinking reaction between PVA and the dissociated B(OH)4
- was found less effective in the aqueous suspension prepared with the hydrioxylated BaTiO3 than with the original BaTiO3 powder. The resulted inhibition in the gelation between PVA and B(OH)4- just meets our expectation of the improvement on the rheology of suspensions. In this
investigation, the interactions among the hydroxylated BaTiO3, PVA and B(OH)4- were identified by analyzing the dynamic rheologies and the 11B NMR spectroscopies, and also the degelation mechanisms were characterized and clarified. According to our experimental results, three possible mechanisms of degelation were proposed: (1) the more attraction of the hydroxylated BaTiO3 for B(OH)4- causes more adsorptions of B(OH)4- on powder and reduces its free concentration that is able to crosslink with PVA in the aqueous suspension, (2) the more attractive hydroxylated BaTiO3 to PVA reduces the free concentration of PVA in the aqueous suspension because of its higher adsorption on powder, and (3) the lower equilibrium pH of the aqueous suspension caused by the more acidic hydroxylated BaTiO3 retards the crosslinking between PVA and B(OH)4-. The effectiveness and the relativecontributions of the above three mechanisms on the degelations of PVA were also theoretically calculated and discussed in this thesis.

並列關鍵字

Barium titanate ； BaTiO3 ； Aqueous Suspensions ； Polyvinyl alcohol ； PVA ； boric oxide ； B2O3 ； Gelation ； Degelation

參考文獻

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