臺灣博碩士論文加值系統

在整個陶瓷領域中,傳統陶瓷的用量最多, 應用也最為廣泛,而在傳統
陶瓷中日用瓷,瓷磚或絕緣瓷等,高嶺土是相當重要的原料之一o 本研究針
對純高嶺土和高嶺土/氧化鋁兩系統反應成模來石的過程,來探討材料的燒
結行為,微結構以及機械性質o 研究的結果顯示,高嶺土於燒結升溫過程
中,500C時偏高嶺土會放熱而形成尖晶石相,
並釋出非晶質的石英,此時液相亦開始生成;1190C時尖晶石相會開始轉變
成模來石結晶,模來石生成的溫度範圍為1190C-1400C之間, 此亦為高嶺土
緻密化的溫度範圍,因此高嶺土的燒結反應屬於反應燒結o 高嶺土試樣燒
結至1400C時可達緻密狀態,其相對密度最高只達91%,且1500C後會發生冒
泡現象o 1400C時試樣達最佳機械性質o 在高嶺土/氧化鋁系統中,氧化
鋁的添加並不會影響高嶺土本身的相變化,並於1300C-1500C之間與液相反
應成二次模來石,此二次模來石的生成會抑制試樣緻密化的進行,使使得燒
結行為變為先反應後燒結, 直到1600C時方達緻密狀態,且由於氧化鋁的添
加而抑制冒泡現象的發生,各組成平均相對密度最大皆只達91% o 除此之
外,氧化鋁的添加會使高嶺土的機械性質有顯著提昇,各組成平均強度皆較
純高嶺土系統提昇34% ,而韌性值隨殘留氧化鋁的增加而增加,較純高嶺土
系統最高可提昇87% o 由實驗發現,不論純高嶺土和高嶺土/氧化鋁系
統,因燒結後會殘留過多的孔洞, 最大相對密度值皆約91%左右,並於燒結
過後有殘留液相的存在, 而造成機械性質無法大幅提昇 o

Applications of traditional ceramics for daily use has been
proved successfully.Among the raw materials for traditional
ceramics,kaolin is one of the most importantmaterials. In the
present study, kaolin and powder mixtures of kaolin and
aluminaare used to prepare mullite. The correlation between
processing, microstructureand mechanical properties is
investigated. Kaolin underwent many reactions as temperature is
raised. Kaolin endothermallytransforms to metakaolin with the
accompaniment of water release at 500C. Thenmetakaolin
exthermally transforms to a sipnel phase and released amorphous
liquidat 980C. Between 1190C to 1400C, the spinel phase converts
to mullite. Densification is also taken place at the same time
temperature range. The sintering of kaolin is therefor a
reaction sintering. The mullite prepared from kaolin reach as
amaximum density, 91% relative. As sintering temperature is as
high as 1500C, kaolinsample produces bubbles on surface. In the
kaolin/alumina system, alumina do not affect the phase
transformation ofkaolin itself. But it reacts with liquid phase
at 1300C to 1500C to form a secondarymullite. The secondary
mullite retards the densification. The maximum density canonly
be obtained until temperature is higher than 1600C. However, the
addition ofsamples with various alumina content obtained are 91%
relative density. The flexuralstrength was improved by addition
of alumina to kaolin. The toughness of sample increases with the
increase of alumina content. From microstructural observation,
many pores are formed in both kaolin and kaolin/alumina systems.
Furthermore, the presence of residual liguid phase restricts
theenhancement of mechanical properties.