Bosak Alexei, Dideikin Artur, Dubois Marc, Ivankov Oleksandr, Lychagin Egor, Muzychka Alexei, Nekhaev Grigory, Nesvizhevsky Valery, Nezvanov Alexander, Schweins Ralf, Strelkov Alexander, Vul' Alexander, Zhernenkov Kirill
European Synchrotron Radiation Facility, 71 Avenue des Martyrs, F-38042 Grenoble, France.
Ioffe Institute, Ru-194021 St. Petersburg, Russia.
Materials (Basel). 2020 Jul 27;13(15):3337. doi: 10.3390/ma13153337.
If the wavelength of radiation and the size of inhomogeneities in the medium are approximately equal, the radiation might be intensively scattered in the medium and reflected from its surface. Such efficient nanomaterial reflectors are of great scientific and technological interest. In previous works, we demonstrated a significant improvement in the efficiency of reflection of slow neutrons from a powder of diamond nanoparticles by replacing hydrogen located on the surface of nanoparticles with fluorine and removing the residual amorphous shells of nanoparticles via the fluorination process. In this paper, we study the mechanism of this improvement using a set of complementary experimental techniques. To analyze the data on a small-angle scattering of neutrons and X-rays in powders of diamond nanoparticles, we have developed a model of discrete-size diamond nanospheres. Our results show that fluorination does not destroy either the crystalline cores of nanoparticles or their clustering in the scale range of 0.6-200 nm. This observation implies that it does not significantly affect the neutron scattering properties of the powder. We conclude that the overall increase in reflectivity from the fluorinated nanodiamond powder is primarily due to the large reduction of neutron losses in the powder caused by the removal of hydrogen contaminations.
如果辐射的波长与介质中不均匀性的尺寸近似相等，辐射可能会在介质中强烈散射并从其表面反射。这种高效的纳米材料反射体具有重大的科学和技术意义。在之前的工作中，我们通过用氟取代位于纳米颗粒表面的氢，并通过氟化过程去除纳米颗粒的残余非晶壳层，证明了从金刚石纳米颗粒粉末反射慢中子的效率有显著提高。在本文中，我们使用一组互补的实验技术研究这种提高的机制。为了分析金刚石纳米颗粒粉末中中子和X射线的小角散射数据，我们开发了离散尺寸金刚石纳米球模型。我们的结果表明，氟化既不会破坏纳米颗粒的晶体核心，也不会破坏其在0.6 - 200 nm尺度范围内的聚集。这一观察结果意味着它不会显著影响粉末的中子散射特性。我们得出结论，氟化纳米金刚石粉末反射率的总体提高主要是由于去除氢污染物导致粉末中中子损失大幅减少。
