The mechanism of foaming and thermal conductivity of glasses foamed with MnO2
The mechanism of foaming and thermal conductivity of glasses foamed with MnO2
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DOI：
10.1016/j.jnoncrysol.2015.05.030
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发表时间：
2015-10-01
影响因子：
3.5
通讯作者：
Yue, Yuanzheng
中科院分区：
文献类型：
--
作者：
Petersen, Rasmus R.;Konig, Jakob;Yue, Yuanzheng
我们使用 MnO2 作为发泡剂，在不同温度下、不同持续时间下，从阴极射线管 (CRT) 面板制备泡沫玻璃。 MnO2 还原成 Mn2O3 导致形成 O-2 气体，从而引起初始发泡。 Mn2O3颗粒溶解到玻璃熔体中并随后还原，导致进一步形成O-2气体并使玻璃熔体发泡。提高处理温度和时间可增强泡沫膨胀、Mn2O3 溶解并降低闭孔率。一旦泡沫达到渗透阶段，泡沫就会继续增长。这是由新气泡的成核和随后的生长引起的。我们从孔数密度、孔径和闭孔率方面讨论了孔形态的演变。泡沫玻璃的导热率与密度线性相关。通过将实验数据与结构数据和分析模型进行比较，揭示了传热机理。我们表明，孔径、晶体夹杂物的存在和闭孔程度的影响不会影响整体导热率。 (C) 2015 Elsevier B.V. 保留所有权利。
We prepare foam glass from cathode ray tube (CRT) panels using MnO2 as foaming agent at different temperatures for various durations. The reduction of MnO2 to Mn2O3 leads to formation of O-2 gas, and hence, causes initial foaming. The Mn2O3 particles dissolve into the glass melt and subsequently reduce, causing further formation of O-2 gas and foaming of the glass melt. Increasing the treatment temperature and time enhances foam expansion, Mn2O3 dissolution, and lowers the closed porosity. Once the foam reaches a percolated stage, the foam continues to grow. This is caused by nucleation of new bubbles and subsequent growth. We discuss evolution of pore morphology in terms of pore number density, pore size and closed porosity. The thermal conductivity of the foam glasses is linearly dependent on density. The heat transfer mechanism is revealed by comparing the experimental data with structural data and analytical models. We show that the effect of pore size, presence of crystal inclusions and degree of closed porosity do not affect the overall thermal conductivity. (C) 2015 Elsevier B.V. All rights reserved.