【作者】 孙秀娟；

【导师】 程晓农；

【作者基本信息】 江苏大学 ， 材料学， 2006， 硕士

【摘要】 负热膨胀（Negative thermal expansion，简称NTE）材料研究是材料科学中近年来新兴的学科分支，其中负热膨胀性金属氧化物具有负热膨胀系数大、响应温度范围宽等优点，在光学平面镜、光纤通信领域、医用材料、低温传感器、热电偶及日常生活等方面有巨大的潜在应用价值。特别是新型氧化物ZrW₂O₈材料，在很宽的温度范围内（0.3K-1050K）表现为良好的各向同性负热膨胀特性，热膨胀系数达到-8.7×10^-6K^-1。鉴于ZrW₂O₈的独特性质，本文围绕着ZrW₂O₈粉体的合成及其负热膨胀特性开展了相关的研究工作。 以三种方法制备ZrW₂O₈粉体：以ZrO₂和WO₃为原料，在传统固相法的基础上采用分步焙烧的方法制备ZrW₂O₈粉体，考察热处理温度对粉体的结构组成、颗粒大小、负热膨胀系数的影响；以硝酸氧锆[ZrO（NO₃）₂·5H₂O]和钨酸铵[N₅H₃₇W₆O₂₄·H₂O]为原料，分别通过溶胶凝胶法和共沉淀法制备ZrW₂O₈粉体，重点考察粉体的合成工艺条件以及负热膨胀特性。为降低共沉淀法制备的粉体粒径，以聚乙二醇（PEG）为分散剂，考察加入量对粉体粒径的影响，进而探索负热膨胀系数与粉体粒径的关系。 对所得前驱体进行热重—差热（TG-DSC）分析；以X射线衍射仪（XRD）对所得粉体进行物相分析；以扫描电子显微镜（SEM）和透射电子显微镜（TEM）对粉体的形貌进行表征。利用变温X射线衍射仪精确收集粉体在不同温度下的XRD数据，以Powder X软件分别计算在不同温度下的晶胞参数，进而计算其负热膨胀系数。 结果表明，分步固相法在1220℃保温3h后得到纯ZrW₂O₈粉体，与传统固相反应相比，缩短了合成时间，提高了粉体的纯度，减小了粉体颗粒尺寸，其颗粒尺寸大约为1.5×1.0μm。所得粉体具有很好的负热膨胀特性，在室温到500℃范围内其热膨胀系数为-6.31×10^-6K^-1。采用溶胶凝胶法也制备出高纯度的ZrW₂O₈粉体，但与固相法相比，热处理温度明显降低，在610℃保温5h就得到平均粒径为100nm的ZrW₂O₈粉体；在室温到700℃范围内粉体的热膨胀系数为-3.81×10^-6K^-1，但该方法制备粉体的周期较长。共沉淀法具有原料混合均匀、合成工艺简单、合成周期短、易于工业化等优点。本论文于1180℃制备出了ZrW₂O₈更多还原

【Abstract】 Negative thermal expansion （NTE） material becomes a new branch of materials science in recent years. Their potential uses include electronic, optics, fuel cell, oxygen sensors, thermostats and dental filling products. Particularly, ZrW₂O₈ exhibits large isotropic NTE property over its entire stability range from 0.3K to 1050K, the thermal expansion coefficient is -8.7×10^-6K^-1. Due to the strange properties and potential applications of ZrW₂O₈, the synthesis of ZrW₂O₈ powders and the NTE property were studied in this paper.Three methods were used to synthesize the powders: solid state method, Sol-Gel method and co-precipitaiton method. First, ZrW₂O₈ powders were prepared using the improved solid state reaction by ZrO₂ and WO₃ powders which were used as raw materials. The influence of reaction temperature on the particle size and the negative thermal coefficient were studied. ZrW₂O₈ powders were also synthesized using Sol-Gel route and co-precipitation method using ZrO（NO₃）₂·5H₂O and N₅H₃₇W₆O₂₄-H₂O as raw materials and the reaction conditions and negative thermal expansion coefficient were investigated. In order to decrease the particle size, polyethylene glycol （PEG） was used as dispersant and the influence of the amount of PEG on the particle size and negative thermal expansion coefficient were also studied.The precursors of ZrW₂O₈ were studied by Thermogravimetric and differential scanning calorimetry （TG-DSC）. The structure of the products was studied by Powder X-ray diffraction （XRD） and the morphology of the resulting powders was characterized by Scanning electron microscopy （SEM） and Transmission electron microscopy （TEM）. The negative thermal expansion coefficient was calculated using the lattice constants obtained by Powder X software using the data collected at different temperatures by in Situ X-ray measurement.The results showed that samples obtained at 1220℃ synthesized by improved solid state reaction were single phase with average size of 1.5×1.0μm. Compared with conventional solid state reaction, the pure powders with small particle size were obtained with shorter reaction time. The resulting powders had strong NTE property and the thermal expansion coefficient was -6.31×10^-6K^-1 at the temperature range from room temperature to 500℃. Pure ZrW₂O₈ powders with average dimension of更多还原