【作者】 屈展；

【导师】 程晓农；

【作者基本信息】 江苏大学 ， 材料学， 2007， 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，负热膨胀性金属氧化物具有负热膨胀系数大、响应温度范围宽等特点，在制造生产、航空航天及日常生活等方面有巨大的潜在应用价值。其中Al₂（WO₄）₃材料在较宽温度范围内具有负热膨胀特性，制备过程较简单，在高温高压下保持稳定，是性能优良的负热膨胀材料。本文围绕着Al₂（WO₄）₃粉体和薄膜的合成及其负热膨胀特性开展了相关的研究工作。在本文中，Al₂（WO₄）₃粉体的制备采用两种方法：（1）以Al₂O₃和WO₃为原料，采用固相反应法制备Al₂（WO₄）₃粉体，工艺过程为把Al₂O₃粉体和WO₃粉体以1：3的比例混合球磨，烘干压片后在1000℃烧结30h，冷却后得到Al₂（WO₄）₃粉体；（2）以硝酸铝[Al（NO₃）₃·9H₂O]和钨酸铵[N₅H₃₇W₆O₂₄·H₂O]为原料，采用共沉淀法制备Al₂（WO₄）₃粉体，工艺过程为把硝酸铝和钨酸铵按一定的摩尔比混合搅拌，出现白色沉淀，烘干后得到Al₂（WO₄）₃前驱体，把此前驱体在800℃烧结10h得到Al₂（WO₄）₃粉体。在本文中，Al₂（WO₄）3薄膜采用Al₂O₃和WO₃双靶交替射频磁控溅射法制备，沉积的薄膜在1000℃热处理10min可得到Al₂（WO₄）₃薄膜。对固相法制得的Al₂（WO₄）₃粉体和沉淀法制得的Al₂（WO₄）₃前驱体进行热重—差热（TG-DSC）分析，考察Al₂（WO₄）₃粉体的热稳定性和前驱体的热力学性质；以X射线衍射仪（XRD）对所得粉体和薄膜进行分析，考察其结构组成；以扫描电子显微镜（SEM）和透射电子显微镜（TEM）对粉体和薄膜进行表征，考察粉体的颗粒形貌和薄膜的表面形貌。利用变温X射线衍射仪精确收集粉体和薄膜在不同温度下的XRD数据，分别计算其在不同温度下的晶胞参数，进而计算其热膨胀系数。把两种方法制得的粉体压制烧结成圆柱试样，用NETZSCH热膨胀仪分别测定试样的热膨胀性能，计算试样的热膨胀系数。结果表明，采用固相反应法和共沉淀法都制得了纯度极高的Al₂（WO₄）₃粉体，固相法制得的粉体颗粒呈长方形和椭圆形，平均尺寸大小为0.6×0.4μm，共沉淀法制得的粉体颗粒呈椭圆形，平均尺寸大小为0.2×0.1μm。两者的晶胞参数都表现出各向异性的热膨胀特性，其中a、c两轴随温度的升高而收缩，表现为负热膨胀性，b轴随温度的升高表现出强烈的正热膨胀性。两种粉体烧结试样的热膨胀性表现有差异，从室温到900℃，固相法的表现为负热膨胀，而沉淀法的在室温到520℃表现出一定的正膨胀性，520～900℃表现出较强的负膨胀性；两者的平均热膨胀系数分别为-1.56×10^-6K^-1和-1.13×10^-6。Al₂（WO₄）₃粉体热性能稳定，室温到其熔点范围内，不分解，无相变。采用磁控溅射法经后热处理制得了纯的Al₂（WO₄）₃薄膜，薄膜有择向生长性，在基体上分布均匀。薄膜的晶胞参数也表现出各向异性的热膨胀特性，但与粉体相比，薄膜的a、c轴的负热膨胀性表现不稳定，b轴也呈现出正热膨胀性。更多还原

【Abstract】 Negative thermal expansion (NTE) material becomes a new branch of materials science in recent years. The NTE dysphasia have the characteristic of large coefficient of NTE and wide range of response temperature. Their potential uses in products, voyage and livelihood vastly. As one kind of the NTE material, Al(WO) have NTE capability in large range of temperature. The synthesis of Al(WO) is simple and it retain stability at high temperature and stress, so it is good NTE material. Due to the strange properties and potential applications of Al(WO), the synthesis of Al(WO) powders and thin-film and the NTE property were studied in this paper.Two methods were used to synthesize the powders in this paper. The one, Al(WO) powders were prepared using the solid state reaction. AlO and WO powders, which were used as raw materials, were mixed at 1:3 ratios and milled, and then sintered at 1000℃for 30h to prepare Al(WO) powders. The other, Al(WO) powders were also synthesized using co-precipitation method. In this method, Al(NO)·9HO and NHWO·HO, which were used as raw materials, were mixed at certain ratios and stirred, and then they produced the white sedimentations which were sintered at 800℃for 10h to prepare Al(WO) powders.In this paper, the Al(WO) film were prepared using two-butt-rotating magnetron sputtering method by ZrO and WO which were used as butts. The heat treatment temperature was 1000℃and the time was 10min.The Al(WO) powders which were synthesize by solid state method and the precursors of Al(WO) which were synthesize by co-precipitation method were studied by Thermo gravimetric and differential scanning calorimetric (TG-DSC), and it used to research heat stability of Al(WO) powders and thermodynamic property of the precursors. The structure of the powders and thin film was studied by Powder X-ray diffraction (XRD) and the morphology of the resulting powders and thin film 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 the data collected at different temperatures by in Situ X-ray measurement. The thermal expansion characteristic of column sample, which was sintered by the powders of two method, was determinate by NETZSCH thermal expansion instrument and the coefficient of thermal expansion was calculated using the resulting data.The results showed that pure Al(WO) powders were synthesized by both solid state method and co-precipitation method. The granule of Al(WO) powders by solid state method was rectangle and ellipse and the average size was 0．6×0．4μm. The granule of Al(WO) powders by co-precipitation method was ellipse and the average size was 0．2×0．1μm. The lattice constants of powders by two method both showed anisotropic thermal expansion characteristic. The a and c axis showed NTE character that shrink when temperature rose. The b axis showed strong positive thermal expansive character when temperature rose. The macro performance of thermal expansion that were showed by the powders synthesized by two method was difference. The powders synthesized by solid state method showed NTE at the range of room temperature to 900℃. The powders synthesized by co-precipitation method first showed positive thermal expansion at the range of room temperature to 520℃and then showed NTE at the range of 520℃to 900℃. The average coefficient of thermal expansion of the powders by two method were-1．56×10Kand-1．13×10K respectively. The Al(WO) powders was no decomposition and no phase transition in the range of room temperature to melting point.The pure Al(WO) thin-film was synthesized by magnetron sputtering method and the growth of film showed the character of pick-direction. The film well distribute on the matrix. The lattice constants of thin-film also showed anisotropic thermal expansion characteristic. However, compared to powders, the negative thermal expansion character of a and c axis was not stabilization and the b axis also showed positive thermal expansive character.更多还原