W18O49氧化鎢奈米材料及其特性之研究

Study on Properties of W18O49 Tungsten Oxide Nanomaterial

許金元(Chin-Yuan Hsu)

指導教授 ： 蘇程裕

國立臺北科技大學/機電學院/製造科技研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00190

摘要

本研究係利用電漿電弧氣凝合成法來製備氧化鎢奈米材料，分別探討不同腔體壓力（200~600 torr）、電漿電流（70~90 A）、製備（生成）時間（3~12 min）、氧分壓Ar：O2（1~6：1）、電漿氣含氫量（0~10 %）對於產物的形貌、相態影響，並使用常壓低溫電漿設備對氧化鎢奈米棒進行表面處理，且針對氧化鎢奈米材料的光學、場發射以及使用自行組裝氣體感測量測設備量測其氣體感測特性。研究結果顯示，隨著氧分壓增加時，氧化鎢材料呈現重量增加趨勢，其顏色從黑色至深藍色轉為淡黃色；隨著電漿氣中含氫氣比列的增加，氧化鎢材料呈現重量減少，其顏色從淡黃色至深藍色轉為黑色；針對於氧化鎢奈米棒而言隨了腔體壓力增加，奈米棒的數量也會隨之增加，而電漿電流的提高，促使奈米顆粒在成長過程中有了棒狀熔合現象，且隨了生成時間的增加奈米棒分布數量越多，直到12分鐘後呈現出多是奈米棒；本製程在適當製程條件下成功製備出單斜晶體W18O49奈米棒，每小時產量約為0.33 公克，與單斜晶體WO3氧化鎢奈米顆粒，每小時產量約為5.77公克，其成長機制可透過氣-固（Vapor-Solid, VS）相法解釋。
本研究應用常壓低溫電漿設備對氧化鎢奈米棒進行表面處理，其改質結果顯示使用電漿氣（O2）下，在一樣的高度距離下隨了處理次數的增多，試片表面隨之融合一起有形成小顆粒的趨勢，且在一樣的次數下隨了距離高度越高其形成小顆粒的趨勢越低；在使用電漿氣體為N2與Ar下，電漿氣體N2比Ar有較大幅度的電漿表面處理，且試片表面有些許部分奈米棒融合一起形成小方塊顆粒其方塊顆粒側邊有明顯的棒狀排立。場發射量測結果顯示；WO3奈米顆粒的場發射起始電場為4.76 V/µm，W18O49奈米棒的場發射起始電場為3.54 V/µm，電漿處理後W18O49奈米棒的起始電場約為3.27 V/μm。W18O49奈米棒在小於402 nm波長與WO3奈米顆粒在小於363 nm波長時，開始會有光吸收特性產生。W18O49奈米棒在24小時200 ℃的熱處理條件下具有良好的熱穩定性，適於作為氣體感測實驗使用，其在200 ℃溫度下對不同濃度（1~6 ppm）的NO2氣體具有感測性質，且隨著濃度的增加靈敏度由1.03至3.32且呈線性成長，電漿處理後的W18O49奈米棒在200 ℃溫度下對濃度3 ppm的NO2氣體的敏靈度為1.51。

關鍵字

氣凝合成法 ； 氣-固成長機制 ； 氧化鎢奈米材料 ； 電漿表面處理 ； 場發射 ； 氣體感測

並列摘要

In the present study, tungsten oxide nanomaterials were synthesized by a modified plasma arc gas condensation technique. The effects of the plasma currents (70~90 A), chamber pressures (200~600 torr), production time（3~12 min）, oxygen partial pressure Ar：O2（1~6：1）and plasma including the hydrogen（0~10 %）on the preparation of tungsten oxide nanostructures were investigated. Pre-treatment on the tungsten oxide nanorods for surface modification was investigated by atmospherical plasma jet. The optical, filed emission, and gas sensing characteristics of tungsten oxide nanopowders were also examined.
The results show that the increasing weight of tungsten oxide nanopowders and the color of tungsten nanomaterials turns light yellow from dark blue and black by increasing oxygen partial pressure in blown gas; the decreasing weight of tungsten oxide nanopowders and the color of tungsten oxide nanopowders becomes dark blue by the plasma that compares row increase including the hydrogen.The tungsten oxide nanomrods was increasing with chamber pressures. Urged nanoparticles to have the clavate fusion phenomenon in the development process with increasing plasma currents, and increased the nanorods distribution quantity along with the generated time to be more, 12 minutes later presents all nanorods. This system to prepare a monoclinic crystal W18O49 nanorods successfully, each hourly output approximately is 0.33 gram, and monoclinic crystal WO3 tungsten oxide nanoparticles, each hourly output approximately is 5.77 grams, its growth mechanism is Vapor-Solid solidly（VS） the physiognomy explanation.
Atmospherical plasma jet carries to the surface modification of tungsten oxide nanorod. The results showed that the modified use of plasma gas (O2), in the same distance to increase deal with test-chip of the surface then there is the formation of small particles with the trend, and in the higher distance to some deal with test-chip of the trend of the formation of small particles lower. N2 was more significant than that of Ar plasma for surface modification, and the test piece is somewhat part of the surface nano-rods box integration with the formation of small particle side of the box there is scheduling a clear rod-like. The turn-on field of WO3 nanopowers is 4.76 V/µm, the turn-on field of W18O49 nanorods is 3.54 V/µm and the turn-on field of pre-treatment on W18O49 nanorods by plasma surface modification is 3.27 V/µm. Characteristic absorption bands of W18O49 nanorods and WO3 nanoparticles are smaller than 402 nm and 363 nm, respectively. However, the thermal stability of W18O49 nanorods is good enough under the test environment of 200 ℃ and 24 hours. The sensitivity for NO2 gas with 1~6ppm is excellent under 200 ℃ and proportional to the NO2 gas concentration, and the sensitivity is 1.03 to 3.32 with density increase. W18O49 nanorods by plasma surface modification under 200 ℃ temperatures to the density 6 ppm NO2 gas' sensitive is 1.51.

並列關鍵字

Gas Condensation Technique ； Vapor-Solid Mechanism ； Tungsten Oxide Nanomaterial ； Surface Modification of Plasma ； Field Emission ； Gas Sensing

參考文獻

[61] 謝嘉民，賴一凡，林永昌，枋志堯，「光激發營光量測的原理、架構及應用」，奈米通訊，第十二卷，第二期，2005，第28-39頁。

[5] P. M. Woodward and A. W. Sleight, “Ferroelectric tungsten trioxide,” Journal of Solid State Chemistry, vol. 131, no. 1, 1997, pp. 9-17.

[6] K. Huang, Q. Pan, F. Yang, S. Ni and D. He, “The catalyst-free synthesis of large-area tungsten oxide nanowire arrays on ITO substrate and field emission properties,” Materials Research Bulletin, vol. 43 no. 4, 2008, pp. 919-925.

[7] J. Wang, P. S. Lee and J. Ma, ”Synthesis, growth mechanism and room-temperature blue luminescence emission of uniform WO3 nanosheets with W as starting material,” Journal of Crystal Growth, vol. 311, no. 2, 2009, pp. 316–319.

[8] Y. S. Kim, ”Thermal treatment effects on the material and gas-sensing properties of room-temperature tungsten oxide nanorod sensors,” Sensors and Actuators B, vol. 137, issue 1, 2009, pp. 297-304.