定向硅基陶瓷型芯的高温强化

High-temperature strengthening technology of directional silica based ceramic core

采用热压注法制备氧化硅基陶瓷型芯,以硅酸乙酯水解液为强化液对型芯进行高温强化,研究强化液浓度和强化次数对型芯的高温挠度、开气孔率以及室温抗弯强度的影响。结果表明:强化液浓度对型芯的高温挠度影响显著,而对型芯室温性能影响不大,随着强化液中硅酸乙酯体积分数增加,型芯的高温挠度呈先减小后增大的趋势,当硅酸乙酯的体积分数为90%时,强化效果最佳,高温挠度由强化前的3.43 mm降至1.89 mm;另外,随着强化次数增加,型芯的高温挠度降低,开气孔率和室温抗弯强度都大幅度下降,因此在进行高温强化时,应该选择适当的强化次数,使型芯的高温性能和室温性能达到最优。扫描电镜(SEM)和X射线衍射(XRD)分析结果表明:高温强化在陶瓷型芯中形成的无定形SiO2在高温下转变成为方石英,是型芯高温挠度降低的主要原因。

Silica based ceramic core was prepared by heat-press molding method,using tetra ethyl ortho silicate（TEOS） as strengthening agent.Influences of strengthening agent＇s concentration and strengthening times on high temperature deflection,open porosity and flexural strength of the core were studied by SEM and XRD.Experimental results show that the strengthening agent＇s concentration affects the high temperature deflection significantly but slightly for the room temperature properties.With the increasing of volume fraction of TEOS in the strengthening agent,the high temperature deformation decreases first and then rises again.When the volume fraction of TEOS reaches 90%,the high temperature deflection drops down from 3.43 mm to 1.89 mm,which exhibits the best strengthening effect;In addition,as strengthening times increasing,the high temperature deflection associated with open porosity and flexural strength lowers obviously,so appropriate strengthening times should be selected to make the properties both at high and room temperatures of the core optimal.SEM and XRD analysis reveal that amorphous silica in ceramic core formed by high temperature strengthening transforming into cristobalite at high temperature is the main reason of high temperature deformation decreasing of the core.