多壁碳纳米管填充4-氰基-4 '-戊基联苯（5CB）的低温相变
Low temperature phase transformations in 4-cyano-4'-pentylbiphenyl (5CB) filled by multiwalled carbon nanotubes
摘要：
采用差示扫描量热法（DSC）、低温光致发光和电导率测量等方法研究了多壁碳纳米管（NTs）对5CB低温相变的影响。NT的浓度在0- 1%wt内变化。通过DSC和在加热模式下的光致发光测量获得的纯5CB的实验数据证明在T->229 K和T->262 K存在两个结晶过程，其对应于C1 a-> C1 b和C1 b->C2相变。温度T从10 K升高到229 K引起了光致发光光谱带的红移，这可以用5 CB分子构象的平坦化来解释。此外，光致发光数据允许得出结论，在T=229 K下的结晶导致构象转变为非平面5CB结构特征的理想晶体。非平面构象在α相占主导地位，即，在T>297 K. NTs-5CB复合材料的电导率数据显示，在229 K-296.8 K的温度范围内，较早确定的稳定结晶相C2内的补充异常。它可以反映界面层中5CB的相变对载流子在碳纳米管之间输运的影响。
英文摘要：
The effects of multiwalled carbon nanotubes (NTs) on low-temperature phase transformations in 5CB were studied by means of differential scanning calorimetry (DSC), low-temperature photoluminescence and measurements of electrical conductivity. The concentration of NTs was varied within 0-1% wt. The experimental data, obtained for pure 5CB by DSC and measurements of photoluminescence in the heating mode, evidenced the presence of two crystallization processes at T->229 K and T->262 K, which correspond to C1a->C1b, and C1b->C2 phase transformations. Increase of temperature T from 10 K to 229 K provoked the red shift of photoluminescence spectral band that was explained by flattening of 5CB molecule conformation. Moreover, the photoluminescence data allow to conclude that crystallisation at T=229 K results in conformation transition to non-planar 5CB structure characteristic to ideal crystal. The non-planar conformations were dominating in nematic phase, i.e., at T>297 K. Electrical conductivity data for NTs-5CB composites revealed supplementary anomaly inside the stable crystalline phase C2, identified earlier in the temperature range 229 K-296.8 K. It can reflect the influence of phase transformation of 5CB in interfacial layers on the transport of charge carriers between NTs.
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