碳奈米管應用於放電加工電極材料之研究

Investigation the EDM Behaviour of arbon Nanotube for Electrode Material

吳俊霖(Chun-Lin Wu)

指導教授 ： 黃豐元

國立中央大學/工學院/機械工程學系/碩士(2007年)

摘要

現今應用在放電加工(Electric Discharge Machine, EDM)的電極大都採用銅以及銅合金，主要是因為銅具備優良的電極條件，但銅的熔點只有一千多度，並不適合應用於大能量放電加工。本研究主題是探討一種以碳奈米管(Carbon Nanotube, CNT)與銅微粒製成之CNT/Cu複合電極的放電行為。其研究動乃是利用碳奈米管增加銅電極的熱傳導[1-2]以及放電能量，以改善銅在高能量放電時的之不足，使其成為具有高材料移除率(Material Removal Rate, MRR)以及低電極消耗率(Electrode Wear Rate, EWR)的優良電極材料。本研究使用碳奈米管為增強材料，其為多壁碳奈米管(Multi-Walled Carbon Nanotube, MWCNT)，直徑為20～40 nm、長度為5～15 μm，添加量分別為重量百分比等於0、0.5、1.0、3.0 wt %，而基材使用銅粉，其粒徑尺寸大小大約為40～50μm。二者使用熱壓燒結結合，其燒結條件溫度為1050℃、壓力為16 MPa、真空度保持在10-2 Torr、時間持續1小時，試件外觀為圓餅狀電極材料，再以銑床及線切割機進行機械加工成長條狀，以不同的放電參數進行放電加工，包括脈衝時間、峰值電流、碳奈米管添加量、放電波形以及表面粗糙度(Surface Roughness, SR)的探討。
由實驗測得知在脈衝時間為100 μs時有較佳之MRR，另外在峰值電流為8 A時，探討有添加與無添加碳奈米管的電極之差異發現：在電流8 A以下時，添加CNT電極與銅電極之EWR有降低現象但MRR相差不多；而在8 A以上時，EWR反而升高MRR也亦相對的增高，而當3.0 wt %之電極在電流18 A時可達到增33 % MRR之改善率。

關鍵字

CNT/Cu複合電極 ； 碳奈米管 ； 多壁碳奈米管

並列摘要

Copper and its compounds such as Cu-W alloy are the most common electrode materials in application of electrical discharge machining (EDM). However, due to its intrinsic modest melting temperature and high coefficient of thermal expansion which result in low working efficiency, it is not suitable for high current (>100Amp) and high material removal rate (MRR) EDM condition.
An innovative electrode material was fabricated by adding different amount of Multi-Walled Carbon Nanotube (MWCNT) into copper matrix to enhance its material removal rate and durability in view of carbon nanotube’s remarkable properties such as high thermal conductivity and electrical conductivity. The purpose of this master thesis is to investigate the electrical discharge machining behaviors by this new type of electrode material.
In this approach, the nano-size (diameter：20~40 nm; length：5~15 μm) MWCNT with 0.5, 1.0, 3.0 wt % were mixed with copper powder (40~50 μm). After well dispersed by shaking/ball-milling process, the mixture was poured into the graphite die and underwent 16 MPa pressure to hot press for 1050℃and 60 min under 10-2 Torr vacuum condition. The hot-pressed disk-shape Cu/MWCNT composite was then machined into rectangle by mill and WEDM to serve as electrode for investigating the EDM behavior. The effect of EDM parameters such as pulse duration (Ton), discharging current (Ip) and the improvement of material removal rate (MRR) were analyzed.
From the experimental results, the highest MRR with Cu/MWCNT electrode was achieved by using 100 μs pulse duration. To compare with electrode wear rate (EWR) between pure copper and Cu/MWCNT electrodes, it was found that all three compositions of Cu/MWCNT electrodes have lower EWR when the Ip is below 8 A. On the other hand, copper composite with
3.0 wt % MWCNT has the best MRR up to 33 % by using the Ip at 18 A.

並列關鍵字

Multi-Walled Carbon Nanotube (MWCNT) ； Electrical Discharge Machining (EDM) ； Cu/MWCNT composite

參考文獻

[16].何萬清，“熱化學氣相沉積法製備橫向碳奈米管之研究”，國立中央大學

[18].陳紹良，“以微波化學氣相沉積法成長碳奈米管之研究”，國立中央大學，

Baik, S., “The Effects of Interfacial Bonding on Mechanical Properties of

Nanocomposites,” Nanotechnology, Vol.17, pp.5759-5764, 2006.

Single-Walled Carbon Nanotube Purity on the Thermal Conductivity of Carbon Nanotube-Based Composites,” Applied Physic Letters, Vol.89.