科研之友
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摘要
The temperature distribution and bubble formation in silica glass produced by the spark plasma sintering (SPS) technique have been investigated. Alpha-quartz powder and amorphous silica nanopowder were used as raw materials in the production of cylindrical bulk samples of partially fused silica and vitreous silica. Experiments were conducted with a chamber pressure around 15 Pa, axial compression of approximately 2 kN and heating rates between 40 and 150 degrees C/min. The analysis of the fabricated samples shows that the temperature decreases from the sample centre to the edge in the radial direction and from sample faces to the interior in the axial direction. It was observed that gases are released from the sample at about 750 degrees C, and if high heating rates such as 150 degrees C/min are used at temperatures between 750 and 850 degrees C, bubbles are trapped in the silica bulk during the densification which occurs at around 850 degrees C. The use of high heating rates in this temperature range does not allow gases to escape completely from the sample. It was proved that it is possible to avoid the formation of bubbles in silica glass by using low heating rates (similar to 40 degrees C/min) until the beginning of densification. For temperatures higher than 850 degrees C high heating rates can be used to reduce the overall sintering time without compromising the production of clear silica glass at the end of the process. A holding time of about 4 min at the highest final temperature assists the output of the remaining gases in the compact after consolidation.
- 出版日期2016-6
