半導體矽污泥再生二氧化矽應用於隔熱材料之製備與特性分析

Recycling of Semiconductor Silicon Sludge on the Preparation and Characterization of Silica for Thermal Insulation Applications

謝怡廷(I-TING HSIEH)

指導教授 ： 劉偉仁

中原大學/工學院/化學工程學系/博士(2022年)

https://doi.org/10.6840/cycu202201336

摘要

本研究製備具有低熱導係數之耐燃二氧化矽材料，並對其形貌結構和導熱性能進行探討，其中矽源為回收的半導體矽污泥所分離出來的含水矽酸鈉(Na2O=6.17%，SiO2=17.83%)。實驗共分為三部分：第一部分是以沉澱法並加入結構導向劑製備具有圓球形二氧化矽，並對熟化時間和結構導向劑之濃度效應做顆粒形貌的探討；第二部分為水熱法與微波水熱法製備具有之濃度效應做顆粒形貌的探討；第二部分為水熱法與微波水熱法製備具有閉鎖型孔洞之二氧化矽，其中討論反應溫度以及尿素濃度效應對結構所帶來的影響。兩種方法所獲得的二氧化矽皆經過場發射掃描式顯微鏡、高解析穿透式顯微鏡、孔洞及比表面積分析儀和X光光電子能譜儀等進行了研究。第三部分則是將第一部分與第二部分所得的二氧化矽製成薄膜複合材料，並且量測其熱傳導係數以及火焰燃燒穿透測試。
在第一部分的研究結果發現，隨著結構導向劑的增加，二氧化矽的形貌逐漸變為圓球形且顆粒尺寸也隨之增加，更發現當結構導向劑的濃度較低時，乙二胺在整體中對顆粒尺寸的影響較深，而在結構導向劑濃度高的時候，叔丁醇對二氧化矽的比表面積貢獻較大，其比表面積從404 m2/g上升至723 m2/g，提升了55.97%，55.97%，平均孔徑與孔體積則是大幅下降許多，因此P2513成為高比表面積、圓球形且低熱導率之二氧化矽，顆粒尺寸與密度分別約為225 ~ 320 nm與0.3571 g/cm3。
第二部分所製備的二氧化矽之比表面積雖然很低，但從穿透式顯微鏡可以發現整體結構中有許多閉鎖型孔洞，推測以發現其整體結構中有許多閉鎖型孔洞，這是H512-180與MH512-180具有非常低的熱傳導係數之原因，顆粒尺寸分別約為66 ~108 nm及51 ~69 nm，其密度皆大約都為0.3333 g/cm3。
第三部分是將沉澱法、水熱法以及微波水熱法所合成出來的二氧化矽製備成薄膜並以熱傳導分析儀量測其K值，在所有樣品中擁有最低的熱傳導係數之樣品為P2513-film、H512-180-film與MH512-180-film，其熱傳導係數分別是0.0233 W/m·K、0.0193 W/m·K和0.0192 W/m·K。然而，在火焰燃燒穿透測試中，MH512-180的表現更為突出，在接近800oC的丁烷噴槍下經過600秒的燃燒後依舊保持著34oC的溫度，且沒有因為在高溫下直接與火焰接觸而產生形變，證明此方法所製備的二氧化矽具有非常優異的熱阻隔效果。
綜述以上結果，以結構導向劑合成的二氧化矽雖然是高比表面積的材料，但是由於高比表面積材料的表面自由基越大顆粒之間越容易凝聚使其不易分散，而以尿素所製備出擁有閉鎖性孔洞的二氧化矽不但有較低的比表面積且也有較低的熱傳導係數，因此期望可以當作具有阻燃功能的填充材料。

關鍵字：矽酸鈉、二氧化矽、隔熱材料、熱傳導係數。

關鍵字

矽酸鈉 ； 二氧化矽 ； 隔熱材料 ； 熱傳導係數

並列摘要

This study synthesized a flame-resistant silica material with low thermal conductivity. The morphological structure and the thermal conductivity of the material were investigated and the silica source was aqueous sodium silicate derived from the recycled semiconductor silica sludge. First, spherical silica was prepared by a precipitation method with the addition of structure directing agent. The surface morphology of silica was controlled by the aging time and the concentration effect on the structure directing agent. Second, conventional hydrothermal method and microwave-assisted hydrothermal method are carried out to prepare closed-pore silica. The effects of reaction temperature and urea concentration for its surface morphology of as-synthesized silica was discussed. The silica obtained by both methods was examined by field emission scanning electron microscope, high-resolution transmission electron microscope, surface area and pore size analyzer and X-ray photoelectron spectroscopy. Third, the silica obtained in the first and second parts was made into a thin-film composite with polyvinylidene difluoride followed by the measurement of the thermal conductivity and combustion measurements.
With the increase of the structural guide, the surface morphology of silica became spherical gradually also the particle size increased. When the concentration of the structural guide was low, ethylenediamine had a greater effect on the overall particle size. On the other hand, when the concentration of the structural guide was high, the effect on the specific surface area was contributed by tert-butanol mostly. The specific surface area of P2513 increased from 404 m2/g to 723 m2/g, which displays 55.97% higher than before. Since the average pore size and pore volume decreased significantly. According to the results, P2513 became a material with high specific surface area, spherical and low thermal conductivity. The particle size and density of P2513 are about 225 ~ 320 nm and 0.3571 g/cm3, respectively.
Although the specific surface area of the silica prepared in the second step is very low, it can be found that there are many closed pores in the structure from the transmission electron microscope. Hence, H512-180 and MH512-180 have very low thermal conductivity, the particle size is about 66 ~ 108 nm and 51 ~ 69 nm and the density are about 0.3333 g/cm3. From the results of the third part, P2513-film, H512-180-film and MH512-180-film showed the lowest thermal conductivity, which is 0.0233 W/m·K, 0.0193 W/m·K and 0.0192 W/m·K, respectively. However, in the flame penetration and combustion test, MH512-180 demonstrates outstanding performance, maintaining a temperature of 34oC after 600 seconds of combustion under a butane torch at nearly 800oC. Furthermore, there is no deformation occurs when direct contact with the flame at a high temperature, proving that the silica produced by this method has a perfect thermal barrier effect.
In Summary, the silica synthesized by the structure guide is a material with a high specific surface area. However, because of the large surface free radicals of the high specific surface area material, particles are easier to coalesce but disperse. On the other hand, the silica with closed pores prepared by urea not only has a lower specific surface area but also has a lower thermal conductivity. Thus, it is expected to be used as a filler material with flame retardant function.

Keywords: sodium silicate; silica; thermal insulation material; thermal conductivity.

並列關鍵字

sodium silicate ； silica ； thermal insulation material ； thermal conductivity

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