铝纳米晶的低温电阻率特性研究

发布时间：2018-01-11 12:34

本文关键词：铝纳米晶的低温电阻率特性研究　出处：《西南科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：铝因有良好的导热导电性、抗腐蚀性能、加工成型等特性而被广泛应用于工业、军事、航空航天等领域。随着科技发展,许多领域对材料性能的要求越来越高。而纳米级结构材料的相关性能得到显著提高,如块体铝纳米晶的硬度和强度相比于粗晶铝增大3~11倍。激光惯性约束聚变(ICF)物理实验要求选用的材料在低温环境中不仅要有良好的蓄冷能力,还需具备一定的抗辐照性。研究表明铝纳米晶的蓄冷能力和抗辐照性能都高于粗晶铝,从而使铝纳米晶有望成为ICF物理实验的一种主选材料。研究铝纳米晶低温电阻率特性,不仅可以完善纳米晶材料的物性特性,更有望发掘铝纳米晶的潜在应用价值。如:具有良好的抗辐射性、灵敏度以及选择性的铝纳米晶制成传感器能适应更加恶劣的工业环境;纳米级厚度的铝纳米晶薄膜能节省更多的空间,有望制成微型加热器等。为此,本文就铝纳米晶块体/薄膜电阻率随温度(8 K~300 K)变化的相关规律展开初步研究,主要研究成果有:(1)温度在8 K~30 K范围内,粗晶铝电阻率随温度变化呈现出T4规律。由于电子的平均自由程远大于晶粒尺寸,形成晶界/表面电子-声子散射,从而使铝纳米晶低温电阻率随温度变化不仅呈现出T4变化,还呈现出显著的T3变化。(2)当温度高于120 K时,由于电子平均自由程小于晶粒尺寸,晶界/表面效应对电子输运过程没有影响,铝纳米晶和粗晶铝一样,其电阻率随温度呈线性增加趋势。(3)铝纳米晶块体颗粒之间存在大量孔洞等缺陷,增大电子散射概率;而且铝纳米颗粒表面包裹着非晶氧化铝层,降低电子平均浓度,从而使铝纳米晶块体残余电阻率(5.24×10-4Ω·m)比粗晶铝(2.01×10-10Ω·m)高5~6个数量级。(4)随着铝纳米晶薄膜厚度的增加,平均晶粒尺寸增加,则电子与晶内声子散射几率增大,被晶界散射的概率降低。铝纳米晶薄膜晶界电子-声子散射形成的T3项的系数随着厚度的增加而降低,晶内电子-声子散射产生的T4项的系数随着厚度的增加而增加,即晶内电子-声子散射强度随着厚度的增加而增强,晶界电子-声子散射强度逐渐变弱。(5)由于表面散射、晶界散射、晶内缺陷散射和杂质散射,使铝纳米晶薄膜残余电阻率比粗晶铝的残余电阻率大2~3个数量级,并且残余电阻率随着薄膜厚度的增加而降低。当薄膜厚度低于电子平均自由程及晶粒尺寸时,影响薄膜残余电阻率的主要散射机制为电子-表面散射。当薄膜厚度大于晶粒尺寸时,残余电阻率随厚度变化不明显,表明电子-表面散射对薄膜残余电阻率影响很弱。由于铝纳米晶薄膜中纳米颗粒紧密相连,薄膜致密度高,孔洞等宏观缺陷含量低,则铝纳米晶薄膜残余电阻率(8.69×10-8Ω·m)小于铝纳米晶块体残余电阻率(5.24×10-4Ω·m)。
[Abstract]:Aluminum has been widely used in industrial, military, aerospace and other fields due to its good thermal conductivity, corrosion resistance, processing and molding properties. With the development of science and technology. In many fields, the requirement of material properties is higher and higher, and the correlation of nanostructured materials can be improved significantly. For example, the hardness and strength of bulk aluminum nanocrystalline is 3 ~ 11 times higher than that of coarse aluminum. The material selected for ICFF physics experiment should not only have good cold storage ability in low temperature environment. The results show that the cold storage ability and radiation resistance of aluminum nanocrystalline are higher than that of coarse aluminum. So that aluminum nanocrystalline is expected to become a main material in ICF physical experiment. The study of low temperature resistivity properties of aluminum nanocrystals can not only improve the physical properties of nanocrystalline materials. It is expected to explore the potential application value of aluminum nanocrystals, such as: good radiation resistance, sensitivity and selectivity of aluminum nanocrystalline sensors can adapt to the worse industrial environment; Nano-thickness aluminum nanocrystalline film can save more space, it is expected to be made into micro heater. In this paper, the correlation law of resistivity of aluminum nanocrystalline bulk / film with temperature of 8Kg ~ (300K) is studied. The main research results are as follows: (1) the temperature of Al nanocrystalline bulk / thin film is in the range of 8K ~ (-1) K ~ (30 K). The resistivity of coarse-grained aluminum exhibits T _ 4 law with the change of temperature. Because the average free path of electrons is far larger than the grain size, the grain boundary / surface electron-phonon scattering is formed. Therefore, the low temperature resistivity of aluminum nanocrystalline changes not only T4, but also T3. 2) when the temperature is higher than 120K, the average free path of electrons is smaller than grain size. The grain boundary / surface effect has no effect on the electron transport process. The resistivity of aluminum nanocrystals increases linearly with temperature. Increasing the probability of electron scattering; Moreover, the surface of aluminum nanoparticles is covered with amorphous alumina layer, which reduces the average electron concentration. The residual resistivity of aluminum nanocrystalline bulk is 5.24 脳 10 ~ (-4) 惟路m), which is 5 ~ 6 orders of magnitude higher than that of coarse grain aluminum (2.01 脳 10 ~ (-10) 惟路m). With the increase of the thickness of aluminum nanocrystalline films. With the increase of average grain size, the probability of electron and phonon scattering increases and the probability of scattering by grain boundary decreases. The coefficient of T3 term formed by electron-phonon scattering at grain boundary decreases with the increase of thickness. The coefficient of T4 produced by electron-phonon scattering in crystal increases with the increase of thickness, that is, the intensity of electron-phonon scattering in crystal increases with the increase of thickness. The grain boundary electron-phonon scattering intensity gradually weakens. 5) due to surface scattering, grain boundary scattering, intragranular defect scattering and impurity scattering. The residual resistivity of aluminum nanocrystalline film is 2 ~ 3 orders of magnitude higher than that of coarse aluminum. And the residual resistivity decreases with the increase of the film thickness, when the thickness of the film is lower than the electron mean free path and grain size. The main scattering mechanism affecting the residual resistivity of the film is electron-surface scattering. When the thickness of the film is larger than the grain size, the residual resistivity does not change significantly with the thickness. The results show that the electron-surface scattering has a weak effect on the residual resistivity of the films. Because the nanocrystalline aluminum films are closely connected, the films have high density and low content of macroscopical defects such as pores. The residual resistivity of aluminum nanocrystalline films is 8.69 脳 10 ~ (-8) 惟路m ~ (-1), which is less than 5.24 脳 10 ~ (-4) 惟路m ~ (-1) of aluminum nanocrystalline bulk.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O614.31;TB383.1

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