臺灣博碩士論文加值系統

本研究分為兩部份；第一部份是以熱碳還原法(carbothermal reaction)並加入過渡金屬為添加劑合成β-SiC粉末，探討添加劑的種類與添加量對β-SiC生成溫度及生成粉末特性的影響。實驗結果發現，添加Pd、Mn無法有效降低β-SiC生成溫度，而添加Fe、Co、Ni、Cu有利於在1300℃下生成β-SiC；添加Cu雖然可以於低溫（1300℃）就有β-SiC生成，但因為其熔點較低造成產物結塊使得無法轉化成β-SiC。添加Mn無法於低溫下生成β-SiC，其熔點低於反應溫度很多，造成產物結塊，雖有SiO(g)生成卻無法轉化成β-SiC。
比較添加1wt％Fe、1wt％Co、1wt％Ni、1wt％Cu於1400℃下反應後產物的β-SiC含量發現，添加1wt％Fe、1wt％Co、1wt％Ni於此溫度下之β-SiC含量高於無添加劑於1500℃反應後的產物，由此可知添加1wt％Fe、1wt％Co、1wt％Ni有助低溫生成β-SiC，其β-SiC含量以添加1wt％Fe最高（76.87％），1wt％Co次之（73.14％），1wt％Ni僅30.40％但也接近無添加劑於1500℃反應後的產物（32.07％）。添加1wt％Fe之產物有燒結現象成品仍需經過粉碎及研磨；添加1wt％Co其β-SiC生成量與添加1wt％Fe相近，其粉末除含少量whisker其餘皆是粒子形態且粒徑小（約100~200nm）。添加1wt％Ni之產物大部份以whisker形態存在，由此我們可得知若欲製備β-SiC whisker，Ni應是一極佳的添加劑。第二部份是以形狀記憶合成法(shape memory synthesis)製備具起始碳形態之β-SiC；吾人以活性碳纖維布(activated carbon fabric)為起始碳源，TEOS為矽源；經1500℃持溫8小時於氬氣下進行反應後，製備出碳化矽纖維布(silicon carbide fabric)。

This research is divided into two parts. In the first part, I will use phenolic-resin and Ludox were as the starting materials and add transition metals and use carbothermal reduction to synthsize β-SiC powder. I will discuss the effect of the kinds and the amount of additive on reaction temperature of β-SiC and powder properties. The other part of this research is that I will use activated carbon fabric and TEOS to prepare SiC fabric by shape memory synthesis. I hope that the morphology of SiC preserved the morphology of carbon.
Adding Fe, Co, Ni, Cu enhance β-SiC formation at lower temperature. Adding Fe and Cu caused product to sinter. The product remained as powder when reactants contained Co and Ni. Although reactant with Cu can form β-SiC at 1300℃, the melting point of Cu is lower than reaction temperature, which leads reactants stick together as a cake the reaction surface decreases. Consequently, the reactant can not effectively convert into β-SiC. Adding Mn into reactants can not produce β-SiC at lower temperature. The reason is similar to that of adding Cu. The existence of Mn promoted SiO(g) formation but can not enhance reactants to convert to β-SiC. The yields of adding 1wt% Fe, Co, Ni after reaction at 1400℃ are higher than that of reactants without additives after reaction at 1400℃. The yields of adding 1wt% Fe, Co are even higher than reactants without additives after reaction at 1500℃. It can be seen that adding 1wt% Fe, Co, Ni can promote β-SiC formation at low temperature. The highest yield is by adding 1wt% Fe which is 76.87%. Adding Co has the second highest yield (73.14%) and adding Ni has 30.40% of yield, but it near to reactants without additives after reaction at 1500℃ (32.07%). The product of adding 1wt% Fe was sintered so that it needed to crush and mill. The yield of samples adding 1wt% Co was near to that of sample adding 1wt% Fe. The powder contained few whisker. Its particle size is about 100~200nm. The product of samples adding 1wt% Ni contains a lot of whisker.
After reaction at 1500℃ for 8hr, activated carbon fabric can convert to β-SiC fabric. The product remains the shape of carbon and is flexible. Activated carbon fabric has many micro-pore on surface after activated process. The micro-pore provides many reaction area and promote reaction.

Book List

Abstract………………………………………………………………….Ⅰ
Book List…………………………………………………...………….. Ⅱ
Table List………………………………………………………………..Ⅲ
Figure List………………………………………………………………Ⅳ


Introduction………………………………………………………………1
Literature Review………………………………………………………...3
2-1 The characteristics of SiC…..………………………………………3
2-2 The synthesis of SiC….…….……………………………………….6
2-3 Discussion of thermodynamic on carbothermal reduction of SiO2..10
2-4 The effects of additives on carbothermal reduction……………….14
2-5 Shape memory synthesis…………………………………………..14
Experiment……………………………………………………………...16
3-1 Chemicals……………………………………………………….....16
3-2 Instrument………………………………………………………....16
3-3 Experimental design……………………………………………….17
Results and discussion…………………………………………………..26
Adding transition metals to prepare β-SiC powder
4-1 XRD analysis…………………………………...………………….26
4-2 Weight analysis…………………………………………………….28
4-3 SEM microstructure……………………………………………….28
Preparation of SiC fabric by shape memory synthesis
4-4 XRD analysis……………………………………………………...30
4-5 SEM microstructure……………………………………………….30
Conclusion………………………………………………………………31
Reference………………………………………………………………..46









Table List

Table 1-1 Properties of common structural materials……..……………...1

Table 2-1 Physical properties of β-SiC…………………………………...4

Table 2-2 Comparison of SiC manufacture methods…………………......9

Table 3-1 The weight ratio additives and reactants……………………..25





























Figure List

Fig.2-1 β-SiC structure…………………………………………………...3
Fig.2-2 The flexural strength of various structural materials at high temperature………………………………………………………5
Fig.2-3 Free energy change for reactions (2.10),(2.11) and(2.12)………10
Fig.2-4 Free energy change for reactions (2.11) and(2.14) ~ (2.16)……11
Fig.2-5 Free energy change for Reaction (2.12)and(2.17)~(2.20)……...12
Fig.2-6 Purposed reaction mechanism of SiC from C and SiO2………..13
Fig.2-7 SEM of (a) starting activated charcoal and (b) equivalent final
β-SiC obtained by shape memory synthesis…………………...15
Fig.3-1 Flow chart experimental procedures on the effects of the
transition metals on synthesis of β−SiC……………………….21
Fig.3-2 Flow chart of experimental procedures on the preparation of
β−SiC fabric by Shape Memory Synthesis…………………….22
Fig.3-3 IR spectra of colloidal silica (Ludox), phenolic resin and SiC precursor, which were heat treatment at 300℃,450℃,650℃,750℃,1000℃ for 1hr……………………………………………..23
Fig.3-4 X−ray diffraction patten of β−SiC and CaF2………………...…24
Fig.3-5 Calibration curve of β−SiC…….……………………………….24
Fig.4-1 X-ray diffraction patterns of reactants without additive after
reaction at different reaction temperature……………………...32
Fig.4-2 X-ray diffraction patterns of reactants with 1 wt% additive after
reaction at 1300℃ for 4h………………………….…………....33
Fig.4-3 X-ray diffraction patterns of reactants with 0.5wt%、1 wt%、3wt%
Fe after reaction at 1400℃ for 4h………………………………34
Fig.4-4 X-ray diffraction patterns of reactants with 0.5wt%、1 wt%、3wt%
Co after reaction at 1400℃ for 4h………………………………35
Fig.4-5 The ratio of the β-SiC, carbon and SiO2 in products….………..36
Fig.4-6 Weight loss versus temperature in reactants with different
additives……………………………………………………....37
Fig.4-7 Scanning electron micrograph of reactants without additive after reaction at 1500℃ for 4h………………………………………38
Fig.4-8 Scanning electron micrograph of reactants with 1wt% additives after reaction at 1400℃ for 4h…………………………………38
Fig.4-9 The growth mechanism of SiC whisker………………………...39

Fig.4-10 The profile of products with 1wt％(a) Fe (b)Cu after reaction at
1400℃ for 4h………………………………………………...39
Fig.4-11 Scanning electron micrograph of reactants without additive after reaction at 1500℃ for 4h and after carbon removal…..………40
Fig.4-12 Scanning electron micrograph of reactants with 1wt% additives after reaction at 1400℃ for 4h and after carbon removal……...40
Fig.4-13 Scanning electron micrograph of reactants with 1wt％ Mn after
reaction at 1400℃ for 4h………………….………………......41
Fig.4-14 X-ray diffraction patterns of reactants with 0.5wt%, 1wt%, 3wt% Co, Fe after reaction at 1500℃ for 4h……………….....42
Fig.4-15 X-ray diffraction pattern of activated carbon fabric soaked with TEOS and after reactionat 1500℃ for 4h……………….…….43
Fig.4-16 Scanning electron micrograph of activated carbon fabric…….44
Fig.4-17 Scanning electron micrograph of activated carbon fabric after
reaction at 1500℃ for 8h…………………………………......45

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