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首页> 外文会议>American Society of Mechanical Engineers(ASME) Integrated Nanosystems Conference: Design, Synthesis, and Applications(NANO 2004); 20040922-24; Pasadena,CA(US) >LOW-DIMENSIONAL PHONON HEAT CAPACITY OF TITANIUM DIOXIDE NANOTUBES
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LOW-DIMENSIONAL PHONON HEAT CAPACITY OF TITANIUM DIOXIDE NANOTUBES

机译：二氧化钛纳米管的低维声热容

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摘要

These results show three different regimes of behavior for the anatase nanotubes compared to bulk anatase, delineated by transitions at ～50 K and ～3 K, and exceeding the bulk value by over 30 times at 1.5 K. The transition to nearly constant specific heat below ～3 K is particularly surprising and of fundamental scientific interest. Above ～70 K, the specific heat of anatase nanotubes converges to within 20% of bulk anatase. This important result affirms the guideline of Eq. 1: that even nanometer-sized systems may behave like bulk when the characteristic wavelengths are smaller than the sample dimensions. Because most of the interest in TiO_2 devices is at 300 K and above, it seems likely that the bulk specific heat would be an excellent approximation for the true nanotube specific heat in technological applications. To better understand the different contributions to the nanotube specific heat additional work would be required with a systematic variation of wall thickness and tube diameter, ideally on individual isolated nanotubes. For example, varying the wall thickness would aid the understanding of the upper transition at ～50 K, making it possible to estimate the strength of the interlayer coupling (covalent versus weakly bonded).
机译：这些结果表明，与本体锐钛矿相比，锐钛矿纳米管具有三种不同的行为方式，由〜50 K和〜3 K的跃迁来描述，在1.5 K时超过体积值超过30倍。 〜3 K特别令人惊讶，具有重要的科学意义。在〜70 K以上，锐钛矿型纳米管的比热收敛在整个锐钛矿的20％以内。这个重要的结果肯定了方程式的指导。 1：当特征波长小于样本尺寸时，即使是纳米尺寸的系统也可能表现得像块状。因为大多数对TiO_2器件的关注都在300 K以上，所以在技术应用中，体积比热似乎是真正的纳米管比热的极佳近似值。为了更好地理解对纳米管比热的不同贡献，可能需要系统地改变壁厚和管径，最好在单个隔离的纳米管上进行额外的工作。例如，改变壁厚将有助于理解〜50 K处的上限跃迁，从而有可能估计层间耦合的强度（共价键与弱键合）。

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