粉末冶金法製作銅/奈米碳管複合材料及其場發射性質研究

The powder metallurgy process and field emission properties of copper-carbon nanotube composites

李宗翰

指導教授 ： 張士欽

國立清華大學/工學院/材料科學工程學系/碩士(2013年)

摘要

本實驗研究粉末冶金法製作銅/奈米碳管複合材料及其場發射性質。銅粉與奈米碳管經球磨混合、粉末成形後在1000℃真空下燒結兩小時得到厚度為5mm的試片。燒結過後的試片經過一次平面應變擠型與兩次滾壓和製成退火得到最終的試片，而其厚度達到0.5mm。
為了取適當的退火條件，試片都經過了硬度的測試，在這實驗中也發現，當奈米碳管的含量在4vol%以下時，碳管對複合材料硬度的影響並不顯著。經過這個實驗，700℃作為本實驗的退火溫度。
只經燒結後的試片與加工後的薄試片都會先經過拋光蝕刻再做表面的觀察。只經燒結後的試片，奈米碳管多覆蓋在晶粒表面，而經過加工的薄試片，碳管更均勻的分佈在晶界上與晶粒內。
使用不同的蝕刻條件可以控制試片上碳管暴露的量進而控制場發射的性質。而加工後的薄試片得到最低的起始電場為0.875 V/um。

關鍵字

奈米碳管 ； 場發射元件 ； 粉末冶金 ； 複合材料

並列摘要

The powder metallurgy process and field emission properties of copper/carbon nanotube composites were studied in this work. Pure copper powder and multi-wall carbon nanotubes were mixed by ball milling, compacted and sintered in vacuum at 1000 ℃ for two hours. The sintered 5 mm thick specimens were plane-strain extruded 50% followed by rolling and process annealing to get a final thickness of 0.5 mm.
The hardness of the specimens was measured to determine the appropriate annealing condition. It is found that by adding less than 4 vol% CNTs, there were little effects on the hardness of the specimens. The process annealing temperature of 700℃was chosen.
The as-sintered specimens and thin sheet specimens were then polished and etched. Optical microscope and scanning electron microscope were used to study the morphology of the specimens. It was found that in the as sintered specimens the CNTs were covered on the grains. In contrast, in the worked and annealed specimens the CNTs were more randomly distributed both at grain boundaries and in grains.
Different etching condition was adopted to get different appearance of CNTs on the exposed surface of the specimens for the field emission properties measurement. The lowest turn-on voltage of the thin sheet sample was found to be 0.875 V/um.

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