以炭黑为还原剂制备硅酸锆晶须的研究

Preparation of Zircon Whisker Using Carbon Black as Reducing Agent

以无水四氯化锆为锆源,正硅酸乙酯（TEOS）为硅源,氟化锂为矿化剂,乙醇为溶剂,炭黑为还原剂,采用非水解溶胶–凝胶法在700℃制备得到硅酸锆晶须,借助TG-DTA、XRD和TEM等测试手段研究了炭黑加入方式及用量对硅酸锆合成与形貌的影响。结果表明：炭黑以悬浮液形式加入有助于硅酸锆的一维择优生长;炭黑用量为6wt%时能获得直径为30~90 nm,长径比为6~15,沿[001]方向择优生长的硅酸锆晶须。炭黑与氧反应形成二氧化碳和一氧化碳,炭黑加入方式及用量能够调控反应体系的氧分压。降低氧分压有利于形成更多的气相SiF4,这是促进ZrSiO4一维定向生长的基础,但氧分压过低又妨碍ZrSiO4晶体的合成。因此,适当氧分压有利于ZrSiO4晶须的生长。

Zircon whisker was synthesized at 700 ℃ via non-hydrolytic Sol-Gel method using anhydrous zirconium tetrachloride（ZrCl4） as zirconium source, tetraethylorthosilicate（TEOS） as silicon source, lithium fluoride（LiF） as mineralizer, ethanol as solvent and carbon black as reducing agent. Thermogravimetric analysis and differential thermal analysis（TG-DTA）, X-ray diffraction analysis（XRD） and transmission electron microscope（TEM） were employed to characterize the influences of adding ways and amount of carbon black on the synthesis and morphology of zircon whisker. The results show that the carbon black added in form of suspension is favorable to the one-dimension growth of zircon. When 6wt% carbon black is added, optimized zircon whiskers are achieved along the growth direction of [001], which diameter and aspect ratio are in the range of 30–90 nm and 6–15, respectively. Because of carbon black reacting with oxygen to form carbon dioxide and monoxide, the adding way and amount of carbon black efficiently regulate the oxygen partial pressure in the reaction system. Reducing oxygen partial pressure can form more SiF4 gas, which is the basis of one-dimensional direction growth of zircon. However, excessively low oxygen partial pressure is against the ZrSiO4 formation. Therefore, appropriate oxygen partial pressure can promote the growth of zircon whisker.