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VO2作為一種傳統(tǒng)的多晶型二元化合物，具有B、M 和R 等晶相。VO2（B）是亞穩(wěn)態(tài)的單斜金紅石結(jié)構(gòu)，VO2（M）是單斜金紅石結(jié)構(gòu)，VO2（R）是四方金紅石結(jié)構(gòu)。由于其能在低溫下發(fā)生由半導(dǎo)體向金屬相的轉(zhuǎn)變并具有特殊的光學(xué)和電學(xué)性質(zhì)，使其成為一種具有廣泛應(yīng)用前景的功能材料。本文以偏釩酸銨作為釩源來制備V2O5粉體，再以乙醇作為還原劑，采用一步水熱合成法來制備介穩(wěn)相VO2（B），并在有限條件下研究VO2（B）向VO2（M）轉(zhuǎn)變的條件。實(shí)驗(yàn)中，產(chǎn)物用XRD、SEM手段進(jìn)行表征分析，并通過改變V2O5與乙醇的配比，反應(yīng)時(shí)間，反應(yīng)溫度，和反應(yīng)液的pH值等因素來逐步改進(jìn)實(shí)驗(yàn)條件。實(shí)驗(yàn)結(jié)果表明：在200℃下水熱反應(yīng)24h，乙醇還原V2O5得到較純凈的VO2（B），當(dāng)溫度升高到240℃反應(yīng)時(shí)間增加到72h時(shí)有少量的VO2（B）轉(zhuǎn)變?yōu)閂O2（M）。此外，隨著合成溫度的升高，反應(yīng)時(shí)間的增加，產(chǎn)物顆粒由棒狀變化為雪花狀。 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. 其實(shí)時(shí)態(tài)有時(shí)候不太明白是過去時(shí)還是現(xiàn)在時(shí)更恰當(dāng) |
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2樓2013-06-15 23:34:05
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對(duì)天空說lrj: 金幣+4 2013-06-18 22:06:01
對(duì)天空說lrj: 金幣+4 2013-06-18 22:06:01
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描述背景時(shí)候，若沒有提及前人工作，基本都是一般現(xiàn)在時(shí)； 描述實(shí)驗(yàn)內(nèi)容和結(jié)果的時(shí)候，使用的是過去時(shí)態(tài) This dissertation used， this paper studied這樣的句式可以用，但是以in this dissertation， sth was used。。這樣的被動(dòng)形式出現(xiàn)會(huì)比較習(xí)慣一點(diǎn)，就像你自己寫的in this experiment一樣； 最后兩句應(yīng)該都為過去時(shí)，雖然是你的實(shí)驗(yàn)規(guī)律，但是依然屬于你實(shí)驗(yàn)中獲得結(jié)果的一部分； 其他沒問題，基本功很扎實(shí) |
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對(duì)天空說lrj: 金幣+4, 翻譯EPI+1 2013-06-18 22:05:46
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| 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. |
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