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首页> 外文期刊>Applied Magnetic Resonance >Quadrupole effects in Cu-63 NMR spectroscopy of copper nanocrystals
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Quadrupole effects in Cu-63 NMR spectroscopy of copper nanocrystals

机译：铜纳米晶体的Cu-63 NMR光谱中的四极效应

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摘要

Quadrupole effects in room-temperature continuous-wave (CW) Cu-63 nuclear magnetic resonance (NMR) spectra, "pi/2" pulse length shortening and amplitudes of two-pulse generated echoes were investigated on nanocrystalline copper powders produced by cryogenic melting and by ball milling techniques. Systematic measurements on the parent polycrystalline copper and on copper-based copper-palladium dilute alloys on the basis of the same experimental techniques were also made and the results were compared to that of the nanophase samples. Fractions of Cu nuclei contributing to the specific NMR responses and average field gradients coming from noncubic neighborhoods were estimated in all the investigated cases. The satellite and/or central component origins of NMR spectra of the samples are not a priori trivial even in the simplest case. Comparative analysis of CW and pulsed experiments allowed a surprising technological conclusion to be drawn by finding a smaller chemical impurity content inside the nanograins than the value characteristic of the entire sample. The measured decrease of the impurity concentration in the inner region of the copper nanoparticles is the consequence of the applied technologies: cryogenic melting and ball milling. These preparation methods cause grain-boundary segregation and result in a cleaner inside of copper nanoparticles.
机译：研究了通过低温熔融法制备的纳米晶铜粉在室温连续波（CW）Cu-63核磁共振（NMR）光谱中的四极效应，“ pi / 2”脉冲长度缩短和两个脉冲产生的回波幅度。通过球磨技术。在相同的实验技术基础上，还对母体多晶铜和铜基铜钯稀合金进行了系统测量，并将结果与​​纳米相样品进行了比较。在所有调查的案例中，估计了有助于特定NMR响应的Cu核分数和来自非立方邻域的平均场梯度。即使在最简单的情况下，样品的NMR谱图的卫星和/或中心成分起源也不是先验的。连续波和脉冲实验的比较分析通过发现纳米颗粒内部的化学杂质含量小于整个样品的特征值，得出了令人惊讶的技术结论。铜纳米颗粒内部区域中杂质浓度的测量降低是所应用技术的结果：低温熔融和球磨。这些制备方法导致晶界偏析并导致铜纳米颗粒内部更清洁。

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