Preparation of Zircon Whisker Using Carbon Black as Reducing Agent

Zircon whisker was synthesized at 700 °C 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.