SiO2•nH2O在水熱反應中的相轉變

Phase transformation in the hydrothermal reaction of SiO2•nH2O

汪秉宏(Pin-Hung Wang)

指導教授 ： 王玉瑞

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00015

摘要

本研究之目的在於探討silica xerogel、magadiite、kenyaite、cristobalite、quartz間相轉變的情形，並以水熱合成法在短時間內嘗試合成單一相且結晶性良好的magadiite、kenyaite、cristobalite和quartz。本研究以價錢低廉的水玻璃加入稀鹽酸沉澱出非晶質SiO2．nH2O作為起始原料，再與NaOH + Na2CO3和水一起進行水熱反應，反應溫度為160 ℃ ~ 200 ℃之間。並改變下列參數：礦化劑的含量、有無添加催化劑等，來探討反應溫度及時間對相轉變之影響。
研究的結果顯示：隨著反應溫度的提高，本水熱系統中礦物的相轉變速率變快，相對的所需反應的時間減低。又相轉變的速率亦隨著氫氧化鈉溶液濃度的增加而加速。然而，在未添加催化劑(Na2CO3)之SiO2•nH2O-H2O-NaOH系統中，亦可快速合成出單一相的magadiite、kenyaite與quartz，且相轉變的速率略為變慢。以掃描式電子顯微鏡分析結果顯示，magadiite晶體呈現由許多平板團聚似玫瑰花之外形，kenyaite晶體則呈現似平板狀之外形，而quartz則為似稜柱狀之外形。

關鍵字

水矽鈉石 ； 斜水矽鈉石 ； 石英 ； 水熱法 ； 水玻璃

並列摘要

In order to synthesize well-crystallized Na-magadiite, Na-kenyaite, cristobalite and quartz as a single phase in short reaction time and explore the transformation of an amorphous silica into crystalline phase, we use hydrous silica precipitated from water glass with dilute HCl in aqueous dispersions of NaOH and Na2CO3 and carry out in a stainless steel autoclave in the various reaction time and molar ratios of reactants at 160 ~ 200 ℃ under autogenous pressure.
The related phenomena have been investigated, in the course of which- depending on the temperature, run duration, concentration of mineralizers-quite, catalytic agents added or not, to observe transformation of different reaction phase from amorphous silica to quartz.
The results show that as temperature increases, the speed of phase transformation increases and the reaction time decreases, respectively. In addition, as the concentration of mineralizers increase the phases transform get fast.

並列關鍵字

magadiite ； kenyaite ； quartz ； hydrothermal ； water glass

參考文獻

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