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对天空说lrj金虫 (正式写手)
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急，毕设论文摘要请帮忙检查一下有没有什么错误
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VO2作为一种传统的多晶型二元化合物，具有B、M 和R 等晶相。VO2（B）是亚稳态的单斜金红石结构，VO2（M）是单斜金红石结构，VO2（R）是四方金红石结构。由于其能在低温下发生由半导体向金属相的转变并具有特殊的光学和电学性质，使其成为一种具有广泛应用前景的功能材料。本文以偏钒酸铵作为钒源来制备V2O5粉体，再以乙醇作为还原剂，采用一步水热合成法来制备介稳相VO2（B），并在有限条件下研究VO2（B）向VO2（M）转变的条件。实验中，产物用XRD、SEM手段进行表征分析，并通过改变V2O5与乙醇的配比，反应时间，反应温度，和反应液的pH值等因素来逐步改进实验条件。实验结果表明：在200℃下水热反应24h，乙醇还原V2O5得到较纯净的VO2（B），当温度升高到240℃反应时间增加到72h时有少量的VO2（B）转变为VO2（M）。此外，随着合成温度的升高，反应时间的增加，产物颗粒由棒状变化为雪花状。 Vanadium dioxide（VO2）with different polymorphs is a traditional binary compound. It has polymorphs of B with a metastable monoclinic rutile structure, M with a monoclinic rutile structure and R with a tetragonal rutile structure. VO2 is a potential functional material in various fields for its unique MTS phase transition at low temperature and specific optical and electrical properties. This dissertation used NH4VO3 as the resource of vanadium, and ethanol was treated as reducing agent. The metastable phase VO2 (B) powders were synthesized under the hydrothermal conditions. And under this limited condition, this paper studied the phase transition condition of VO2 (B) and VO2 (M). In this experiment, the means of characterization, such as XRD, SEM, were used to observe the structure and morphology of the products. By changing the molar ratio of V2O5 powder and ethanol, the temperature of hydrothermal reaction, the time of hydrothermal and the pH value of the solution, the experiment condition was improved gradually. The experimental results showed that: by the hydrothermal method, at 200 ℃ for 24h, V2O5 was reduced to pure VO2 (B) by ethanol. When the temperature rises to 240 ℃ and the reaction time is increased to 72h, there is a small amount of VO2 (B) transformed to VO2 (M). In addition, with the increase of temperature and time, the product particle is changed from rod-like shape to snowflake shape. 其实时态有时候不太明白是过去时还是现在时更恰当 |
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2楼2013-06-15 23:34:05
fuboluben
铁杆木虫 (小有名气)
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对天空说lrj: 金币+4 2013-06-18 22:06:01
对天空说lrj: 金币+4 2013-06-18 22:06:01
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描述背景时候，若没有提及前人工作，基本都是一般现在时； 描述实验内容和结果的时候，使用的是过去时态 This dissertation used， this paper studied这样的句式可以用，但是以in this dissertation， sth was used。。这样的被动形式出现会比较习惯一点，就像你自己写的in this experiment一样； 最后两句应该都为过去时，虽然是你的实验规律，但是依然属于你实验中获得结果的一部分； 其他没问题，基本功很扎实 |
3楼2013-06-16 07:52:20
luodiheng
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对天空说lrj: 金币+4, 翻译EPI+1 2013-06-18 22:05:46
对天空说lrj: 金币+4, 翻译EPI+1 2013-06-18 22:05:46
| As a traditional polymorphic binary compound, Vanadium dioxide（VO2）has polymorphs of B, M, R and et ac. The polymorph B has a metastable monoclinic rutile structure, polymorph M has a monoclinic rutile structure and polymorph R has a tetragonal rutile structure. VO2 is a potential function material with broad applications for its unique MTS phase transition characteristic at low temperature and specific optical and electrical properties. This dissertation focused on an one step synthesis of metastable phase VO2 (B) powders under hydrothermal conditions, using NH4VO3 as the resource of vanadium and ethanol as reducing agent. And, this paper studied the phase transition condition from VO2 (B) to VO2 (M) under provided circumstances as well. For the experiment, the means of characterization, such as XRD, SEM, were used to observe the structure and morphology of the products. The experiment was optimized by adjusting the molar ratio of V2O5 powder to ethanol, the temperature, reaction time and pH value of the reaction solution. The experimental results showed that: under hydrothermal method, V2O5 was reduced to pure VO2 (B) by ethanol at 200 ℃ in 24h. When the temperature rose to 240 ℃ and the reaction time was increased to 72 h, a small amount of VO2 (B) was transformed to VO2 (M). In addition, with the increase of temperature and time, the shape of the product particle changed from rod-like to snowflake. |
4楼2013-06-16 14:21:15