液相與氣相法直接合成奈米銀負載之氧化矽溶膠與粉體

Direct Synthesis of Nano-Silver Loaded Silica Sols and Powders via Liquid and Gas Phase Methods

江學墀(Shiue-Chih Chiang)

指導教授 ： 張幼珍

元智大學/工程學院/化學工程與材料科學學系/碩士(2006年)

摘要

本實驗是利用液相法(溶膠凝膠法)及氣相法(火焰合成法)合成銀-矽複合材料粒子。其中，以液相法合成銀-二氧化矽複合粒子可分為兩種做法︰一種是將銀直接合成在二氧化矽表面上，另外一種則是利用已修改過的Stobe方法製備。在液相法中，我們將討論不同的配製方法及不同的還原處理步驟，對於銀分布在二氧化矽上的影響。而至於氣相法，我們將討論銀的添加量多寡對於生成粒子特性的影響。
在“合成銀附著於二氧化矽複合粒子”這個實驗中，我們可以由XRD及EDX的分析結果發現，產物粒子中的銀跟二氧化矽已經順利結合。利用[Ag(NH3)2]+ 錯離子所配製的複合粒子，其所附載的銀元素量大於由Ag+ 離子所配製的粒子。根據TEM的分析結果，利用硼酸氫鈉所還原的銀粒子，其粒子大小較利用熱還原處理的銀粒子大。而這個結果將影響到銀附著在二氧化矽的量及分佈，因為當銀粒子大到某個程度將會影響銀的附著能力。粒子大其附著能力較差，因此銀粒子容易在清洗的實驗過程中流失。因此利用熱還原的複合粒子的銀負載量大於利用還原劑還原的複合粒子。至於另一種利用修改過的Stobe方法所配製的實驗，我們得到銀-二氧化矽複合粒子相互連結的結構。
至於火焰合成法，在先驅物中添加不同酸鹼催化劑，此舉將可以得到截然不同形貌的銀-二氧化矽複合產物。在酸性條件下(硝酸)，我們可得到具有完美圓形的球形粒子產物，其粒子大小落在50nm至700nm之間。當銀的添加量比例達到0.15 (Ag/Si)，其合成的複合粒子其形貌和未加銀的粒子形貌差不多，其粒徑一樣介於50nm到700nm之間。在高濃度的銀條件下(Ag/SiO2 = 0.5)，其複合粒子的形貌已經開始有些變形，似乎不若先前的圓。利用TEM觀察分佈在二氧化矽中的銀粒子，其粒徑大小分較先前的複合粒子粒徑廣，粒境介於5nm to 40nm之間。在鹼性條件下(氨水)，我們可得到片狀的薄膜結構，並且隨著銀的添加量增加，其薄層的厚度將逐漸減少並趨於緻密。

關鍵字

溶膠凝膠 ； 火焰噴霧熱解 ； 二氧化矽 ； 複合材料 ； 銀

並列摘要

Silver-loaded composite particles have been synthesized by liquid method (sol-gel technique) and gas method (flame synthesis). It can separate into two sol-gel fabrication processes were investigated to make silica sphere containing Ag nanoparticles: (1) a Ag-coated process on silica particle, and (2) a modified Stober method for silica spheres. In synthesis of Ag-coated composite particle, it discussed not only the effects of preparation for the distribution of Ag-loaded on silica surface, but also observed the influence of reducing treatment. The experiment of synthesis of Ag-doped silica particle was studied to fabricate the Ag/SiO2 miscellaneous composite by various preparations. At last, we discussed the effect of the adding of Ag/Si ratio in investigation of synthesis of Ag/SiO2 composite via flame technique.
For synthesis of Ag-coated composite particle, the results of XRD and EDX represented that the silver was combined with silica successfully. It had more silver on silica particles which employed [Ag(NH3)2]+ to manufacture, and the fewer quantity of silver loaded on silica surface by used Ag+ ion to prepare. Silver particle would grow larger by NaBH4 reducing regent by TEM analysis, and this result would cause the adsorption of silver reduced and easy to lose away by wash treatment. Therefore the quantity of Ag-loaded which prepared by reducing agent was lower than it prepared by heat reducing treatment. For the other liquid method, It obtained the linked structure of Ag/SiO2 composite by modified Stober method.
For flame synthesis, there were obtained that Ag/SiO2 composite had the different morphology by employed different of catalyst. In the acid condition (HNO3), perfect circular spheres were obtained which size range was between 50nm to 700nm by SEM analysis. At the ratio of Ag/SiO2 was 0.15, there were smaller silver particle distributed well in or on silica nano-particle, which the range of diameter between 2nm to 6.5nm by TEM analysis. At higher the adding of silver (Ag/SiO2 = 0.5), the morphology of particle was changed slightly. By TEM analysis, the size range of silver was more extensive than before (Ag/SiO2 = 0.15) which between 5nm to 40nm. There were the flaky structure was obtained which prepared by NH4OH. At the condition of Ag-added, the structure thickness was seam more thin than sample without Ag-added, and the density of structure was also higher than without Ag-added sample.

並列關鍵字

sol-gel ； flame spray pyrolysis ； silver ； composite ； silica

參考文獻

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