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°Ù¶ÈËÑË÷Ï£¬¶àÄØ£º http://www.baidu.com/s?wd=XRD++%C4%C9%C3%D7&cl=3 ľ³æÏà¹ØÊéÒ²²»ÉÙ Characterizing nanomaterials with XRD±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ X-ray diffraction (XRD) is a powerful method for the study of nanomaterials (m±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ aterials with structural features of at least one dimension in the range of 1-±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ 100 nm). Nanomaterials have a characteristic microstructure length comparable ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ with the critical length scales of physical phenomena, giving them unique mech±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ anical, optical and electronic properties.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ X-ray diffractograms of nanomaterials provide a wealth of information - from p±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ hase composition to crystallite size, from lattice strain to crystallographic ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ orientation. The Georgia Institute of Technology's Center for Nanoscience and ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Nanotechnology (Georgia Tech; Atlanta, Georgia, USA) is well equipped for nano±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ material research with PANalytical X'Pert PRO MRD, X'Pert PRO MPD and Alpha-1 ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ systems, each used for particular applications.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Growth orientation of ZnO nanobelts±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Nanobelts are single crystal, defect-free, shape-specific semiconductors requi±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ring no protection against oxidation - properties that have many potential app±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ lications. At Georgia Tech, the X'Pert PRO MRD was used to study the growth or±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ientation of nanobelts with respect to the single crystal Al2O3 substrate.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Professor Z L Wang's research group, working with ZnO nanobelts, has shown tha±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ t under certain conditions these can be grown in different crystallographic or±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ientations with specific dimensions and shapes. Figure 1 shows the TEM image o±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ f a typical ZnO nanobelt. [attachment=15920] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 1: TEM micrograph of a ZnO nanobelt. The sphere at the tip of the nanob±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ elt is the Au catalyst used in this specific study.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 2 shows nanobelts with a definite preferred growth orientation, with re±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ spect to a single crystal substrate. The Fourier transform of the SEM microgra±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ph (Figure 3) confirms the XRD findings. While microscopy techniques and XRD a±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ re complementary, in this study XRD has the advantage of being able to sample ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ a large volume of material, providing an average representation of the microst±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ructure.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15923] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 2: XRD pole figure of 0002±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15924] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 3a: SEM micrograph of ZnO nanobelts±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15925] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 3b: Fourier transform of SEM micrograph±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Studying the defects of nano-structured metals±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ A high-resolution diffractometer such as the X'Pert PRO Alpha-1 may not be an ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ obvious choice for studying dislocation type and density evolution in nano-str±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ uctured Cu by deformation at liquid nitrogen temperature, considering that mat±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ erials with small crystallite size will have correspondingly broad, low intens±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ity diffraction peak profiles. However, for some materials, broadening may be ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ due to more than just crystallite size and the Alpha-1's ability to eliminate ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ the redundant Ka2 contribution to the profile means less error in the final an±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ alysis.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 4 shows crystallite size distributions at four levels of deformation by±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ rolling copper under liquid nitrogen temperature. The total dislocation densi±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ty and types of dislocations were then extracted from the XRD line profile ana±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ lysis (figure 5). Studies like these help researchers understand the unique me±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ chanical properties of nano-structured metals.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15926] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 4: Crystallite size distribution at different deformation levels±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 5: Dislocation character and densities in deformed nano-structured Cu a±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ s a function of deformation±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ In situ high temperature analysis of 3D nanostructures±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Georgia Tech's X'Pert PRO MPD is fitted with an HTK1200 oven - an in situ diff±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ raction tool used in this case to convert silica-based diatom nanostructures t±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ o materials such as MgO, while preserving their complex shapes.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Diatoms are single-celled aquatic microorganisms, which assemble complex silic±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ a microshells (frustules) containing channels, pores or other intricate featur±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ es. Although the sizes of diatoms vary, typical frustule dimensions are around±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ 100 micrometers. Such 3D assemblies of magnesia nanocrystals could have agric±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ultural, pharmaceutical, petrochemical, environmental and structural applicati±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ons.±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Diffractograms collected every five minutes during the isothermal annealing pr±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ocess document the progress of the chemical conversion of the diatoms in the p±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ resence of Mg vapor (Figure 6).±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15927] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Silica diatom±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15928] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Diatom converted to MgO±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ [attachment=15929] ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Figure 6: X-ray diffraction patterns collected during annealing±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ Above information is mostly based on following literatures:±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ * ZnO nanobelts: R. Yang, I. Dragomir-Cernatescu, Z.L. Wang and R. L. Snyder±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ * MgO Nanodevices: M. S. Haluska, I. Dragomir-Cernatescu, K. H. Sandhage and R±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ . L. Snyder±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ * Deformed Nano-structured Cu: I. Dragomir-Cernatescu, M. Gheorghe, N. Thadha±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ni and R. L. Snyder±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ More detailed descriptions of the above studies can be found in:±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ 1. Dragomir-Cernatescu I., Gheorghe M., Thadhani N. and Snyder R. L.: "Disloca±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ tion densities and character evolution in copper deformed by rolling under liq±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ uid nitrogen from X-ray peak profile analysis"; Powder Diffraction pp. 109-111±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ , 20(2), (2005).±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ 2. M. S. Haluska, I. Dragomir-Cernatescu, K. H. Sandhage and R. L. Snyder: "X-±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ray diffraction Analysis of 3-D MgO Diatom Replicas Synthesized by Low-Tempera±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ ture Gas/Solid Displacement Reaction"; Powder Diffraction pp. 306-310, 20(4), ±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ (2005).±¾ÎÄÀ´×Ô:²©ÑÐÁªÃËÂÛ̳ |

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