本文關鍵詞： 三氧化鉬 微納結構 三甲胺 氣敏性能　出處：《天津理工大學》2015年碩士論文　論文類型：學位論文

【摘要】：Mo O3是禁帶寬度為3.3 e V的n型半導體氧化物,近年來因其對易燃易爆有毒氣體優(yōu)良的氣敏性能而得到了人們的廣泛關注。Mo O3常見物相有正交相(α-Mo O3)、六方相(h-Mo O3)和單斜相(β-Mo O3)三種,其中正交相是熱力學穩(wěn)定相,六方相與單斜相是熱力學介穩(wěn)相。本文利用條件溫和的水浴法和水熱法,在不添加表面活性劑的條件下,合成了h-Mo O3和α-Mo O3微結構,并研究了其氣敏性能。利用條件溫和的溶液法,以濃硝酸酸化的鉬酸銨飽和溶液為初始反應物,通過改變反應介質的水醇比和反應時間,65oC水浴下制備出不同形貌的h-Mo O米棒。利用所制備的h-Mo O3微米棒作為基體制備燒結型氣敏傳感器件,340oC的工作溫度下對不同濃度的三甲胺氣體進行氣敏性能測試。結果表明,水醇比為15:15、反應時間為30 min時制備的樣品氣敏性能最好,器件對500 ppm的三甲胺氣體測量靈敏度可達95.2,響應時間和恢復時間分別為10 s和7 s。尤其是,在這種反應條件下制備的h-Mo O3對低濃度的三甲胺有著良好的氣敏性,當三甲胺氣體濃度為1 ppm時,其靈敏度仍可達2.61。這種良好的氣敏性能可能是由于反應介質中無水乙醇的加入,使得到的h-Mo O3六棱柱表面出現(xiàn)層片狀結構;且反應時間適中,所得到的h-Mo O3尺寸適中,因而使得其具有較大的比表面積,從而有利于還原性氣體的表面反應過程。利用低溫水浴法,對酸化若干天的鉬酸銨飽和溶液進行處理,通過研究改變酸化天數(shù)和反應時間,在95oC下制備了不同形貌的h-Mo O米花球。利用所得到的h-Mo O3微米花球制備燒結型氣敏傳感器件,340oC工作溫度下對不同濃度的三甲胺氣體做了氣敏性能測試。結果表明,酸化時間為40天、反應時間30 min時制備的樣品氣敏性能最佳,對500 ppm三甲胺靈敏度可達到272,較前述h-Mo O3微米棒提高了2.85倍,響應和恢復時間分別為8 s和7 s,在低濃度1 ppm下,其靈敏度能夠達到4.44。h-Mo O3微米花球較h-Mo O3微米棒氣敏性有了較大的提升,可能是由于酸化一段時間后的鉬酸銨飽和溶液在水浴反應的過程中生成的微米棒自組裝成微米花球,從而大大提高其比表面積,且增加了(001)面的比例,改善了其氣敏性能。將市售Mo O3溶于33%的雙氧水中,并在硝酸的作用下170oC水熱反應,得到了α-Mo O3納米帶。為進一步提升其氣敏性能,采用簡單的液相法在其表面進行修飾,制備了p-Cu O/n-Mo O3異質結納米帶。對制備出的樣品進行氣敏性能測試結果表明,當Cu O與α-Mo O3理論摩爾比為0.5:1時氣敏性最佳,300oC工作溫度下對500 ppm三甲胺靈敏度可達到84.2,是單純a-Mo O3納米帶的3.89倍,其響應恢復時間分別為12 s和15 s。低濃度1 ppm下,其靈敏度可達到4.32。這主要是因為在p-Cu O納米顆粒與n-Mo O3納米帶之間形成的p-n結,在界面形成較厚的耗盡層,因此氣敏性能得到了明顯提升。
[Abstract]:MoO3 is an n-type semiconductor oxide with a band gap of 3.3 EV. In recent years, due to its excellent gas sensitivity to flammable and explosive toxic gases, people have paid more and more attention to the common phase of MoO _ 3, which consists of the normal phase (偽 -MoO _ 3, hexagonal phase) and the monoclinic phase (尾 -MoO _ 3), in which the orthotropic phase is a thermodynamically stable phase. The hexagonal phase and monoclinic phase are thermodynamically metastable phases. In this paper, h-MoO3 and 偽 -MoO3 microstructures were synthesized without adding surfactants by water bath and hydrothermal method with mild conditions. The gas sensing properties were studied. The saturated solution of ammonium molybdate, which was acidified by concentrated nitric acid, was used as the initial reactant by the solution method with mild conditions. H Mo O O rods with different morphologies were prepared by changing the water / alcohol ratio of reaction medium and reaction time of 65oC in water bath. The sintered gas sensing devices were prepared by using the prepared h-MoO 3 micron rods as the substrate for different operating temperatures. The concentration of trimethylamine gas was tested by gas sensitivity test. When the ratio of water to alcohol is 15: 15, and the reaction time is 30 min, the gas sensitivity of the device is up to 95.2, the response time and recovery time are 10 s and 7 s, respectively. The h-MoO3 prepared under this reaction condition has good gas sensitivity to trimethylamine at low concentration. When the concentration of trimethylamine is 1 ppm, The sensitivity is still up to 2.61.This good gas sensing property may be due to the presence of lamellar structure on the surface of h-MoO _ 3 hexagonal prism due to the addition of anhydrous ethanol in the reaction medium, and the appropriate reaction time and the appropriate size of h-MoO _ 3. Therefore, it has a large specific surface area, which is beneficial to the surface reaction process of reductive gas. The saturated solution of ammonium molybdate for several days was treated by low temperature water bath method. The h-MoO _ 2 flower balls with different morphologies were prepared at 95oC. The gas sensing properties of different concentrations of trimethylamine were measured by using the h-MoO _ 3 micron spheres to prepare sintered gas sensing devices (340oC) at different temperatures. When the acidizing time was 40 days and the reaction time was 30 min, the gas sensitivity of the sample was 272for 500 ppm trimethylamine, which was 2.85 times higher than that for h-MoO _ 3 micron rod mentioned above. The response and recovery time were 8 s and 7 s, respectively, and at low concentration of 1 ppm. Its sensitivity can reach 4.44.h-MoO3 micron flower ball, which is more sensitive than h-MoO3 micron rod gas sensitivity. It may be due to the formation of micron bouquet by self-assembly of micron rod formed by saturated ammonium molybdate solution during water bath reaction after acidizing for a period of time. Therefore, the specific surface area is greatly increased, the ratio of the surface is increased, and the gas sensing property is improved. The available MoO3 is dissolved in 33% hydrogen peroxide and hydrothermal reaction is carried out in 170oC under the action of nitric acid. 偽 -MoO _ 3 nanobelts were obtained. In order to further improve their gas-sensing properties, p-Cu O _ (-) / n-MoO _ 3 heterojunction nanobelts were prepared by a simple liquid-phase method. The gas sensing properties of the prepared nanobelts were measured. When the theoretical molar ratio of Cu O to 偽 -MoO 3 is 0.5: 1, the optimum gas sensitivity of 300oC is 84.2% for 500 ppm trimethylamine, which is 3.89 times higher than that of pure a-MoO 3 nanobelts. The response recovery time is 12 s and 15 s 路1 ppm, respectively. The sensitivity is 4.32. This is mainly due to the formation of p-n junctions between p-CuO nanoparticles and n-MoO3 nanobelts and the formation of a thicker depletion layer at the interface.
【學位授予單位】：天津理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ136.12

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