X-ray diffraction studies of thermal properties of bulk- and surface-atoms of nanocrystalline SiC

Svitlana Stelmakh 1Stanisław Gierlotka 1Ewa Grzanka 1,2Bogdan F. Palosz 1

1. Polish Academy of Sciences, High Pressure Research Center (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
2. Warsaw University, Faculty of Physics, Hoża 69, Warszawa 00-681, Poland

Abstract

Until recently no definite experimental evidence of a presence of strain and/or of reconstruction of the surface structure of nanocrystals has been presented. Using powder diffraction techniques we were able to determine the atomic structure of nanocrystalline grains. In a series of powder diffraction experiments, using synchrotron and neutron sources, we showed that powder diffraction techniques can be effectively applied for studies on nanopowders with crystallite dimensions below 20 nm and can differenciate between the structure of the grain interior and its surface. A meaningful and unique interpretation of such diffraction experiments requires that the data are collected in a large diffraction vector range, 150 nm-1 or more. We evaluated the structure of nanocrystals of SiC, diamond, and GaN using the following characteristics: (a), the type of strains at the surface (compressive or tensile), (b), the profile of the strain field, (c), thickness of the surface layer and, (d), a response of the lattice of the grain interior to the stress exerted by the surface atoms. In this paper we report preliminary results of examination of thermal properties of SiC nanocrystals aiming at, (1), determination of the thermal expansion coefficient and, (2) the Debye temperature, assuming that thermal vibrations are different in the grain core than at its surface. The experiments were performed at SNBL station, ESRF, Grenoble (wavelength of 0.05 nm) in the temperature range of 130 - 920 K. We examined 15 nm SiC powders: (i), as synthesized, (ii), sintered under high-pressure high-temperature conditions, and (iii), embedded in a nanocomposite with (Zn + Al) matrix. The elaboration of the experimental data is based on the theoretical diffraction patterns calculated for nanocrystals with different thermal vibrations modes.


 

Related papers
  1. Analysis of density waves in CdSe, SiC, and diamond nanocrystals by application of NanoPDF software package to experimental Pair Distribution Functions.
  2. Crystallite size determination from diffraction data: a do-it-yourself tutorial.  
  3. Diamond-tungsten carbide nanocomposite
  4. GaN substrates with variable surface miscut for laser diode applications
  5. Semipolar (2021) UV LEDs and LDs grown by PAMBE
  6. High-pressure diffraction study of structural and elastic properties of zircon-type and scheelite-type RVO4 (R = Nd, Eu)
  7. Looking at the real structure of nanocrystals with powder diffraction: the apparent lattice parameter approach
  8. Looking beyond limitations of diffraction methods of structural analysis of nanocrystalline materials
  9. Synthesis of doped ZnO nanopowders in microwave hydrothermal reactors
  10. Characterization of nanopowders
  11. Combining microwave and pressure techniques for hydrothermal synthesis of ZnO and ZrO2 nanopowders doped with a range of metal ions
  12. Luminescence properties of zinc oxide nanopowders doped with Al ions obtained by the hydrothermal and vapour condensation methods.
  13. Yttrium-Aluminum Garnet Synthesized in the Medium of Supercritical Fluids
  14. Growth of GaN layers on silicon and sintered GaN nano-ceramic substrates – TEM investigations
  15. Doping of ZnO nanopowders with Mn, Ni and Cr In an ultrasound and microwave driver hydrothermal reaction
  16. Characterization of nanocrystalline ZrO2 doped with Rare-Earth elements synthesized via High Pressure Hydrothermal Method
  17. Morphology of Al doped Zinc Oxide Obtained using Hydrothermal and Vapour Condensation Methods
  18. Growth and properties of ytterbium doped KY(WO4)2 nanocomposites
  19. Doping of ZnO nanopowders with Mn and Cr in an ultrasound and microwave driven hydrothermal reaction
  20. Dyfraktometryczna analiza mikro- i makro-naprężeń w spiekach i kompozytach otrzymanych pod wysokim ciśnieniem i wysoką temperaturą.
  21. Badania własności termicznych nanokryształów metodami dyfraktometrycznymi
  22. Morphology of Al doped zinc oxide obtained by the vapour condensation method
  23. Morphology of Al-Doped Zinc Oxide Obtained by the Vapour Condensation Methods
  24. Structure of nano-crystals: a key to understanding the unique properties of nano-materials
  25. Fabrication and micro-structure characterization of Al2O3/Ni-P composites with interpenetrating phases
  26. Nanocrystalline SiC compacts obtained by sintering of laser synthesized nanopowders under extreme pressures
  27. High-pressure Induced Structural Decomposition of RE-doped YAG Nanoceramics
  28. Sintering of nanopowders under high pressure
  29. Synthesis and properties of GaAs nano-composites
  30. MD simulation of atomic structure of nanocrystals
  31. SiC-Zn nanocomposites obtained using high-pressure infiltration technique
  32. Sintering temperature effect on structure and properties of Al2O3/Ni-P composites with interpenetrating phases
  33. Influence of synthesis conditions on the particles size and the morphology of zinc oxide nanopowders
  34. Structural and luminescence properties of yttrium-aluminum garnet (YAG) nanoceramics
  35. Fabrication and electrical properties of Eu3+:BaTiO3 nanoceramics for SOFC
  36. Characterization of nanostructured hydroxyapatite ceramics densified at high-pressure and temperature
  37. Powder precursors for nanoceramics: cleaning and compaction
  38. Examination of the atomic Pair Distribution Function (PDF) of SiC nanocrystals by in-situ high pressure diffraction
  39. Investigation of the microstructure of SiC-Zn nanocomposites by microscopic methods: SEM, AFM and TEM
  40. Sythesis of metal-ceramic nanocomposites by high-pressure infiltration
  41. X-Ray investigations of the natural and artificial White Etching Layer
  42. Zinc oxide nanopowders obtained by the microwave-hydrothermal route
  43. Microwave driven hydrothermal synthesis of Pr-doped zirconia nanopowders
  44. The influence of temperature and pressure on possibility of obtaining Al2O3/Ni-P nanocomposite through hot pressing process.
  45. X-Ray Characterization of Nanostructured Materials
  46. Generetion and Relaxation of Strain in SiC and GaN under Extreme Pressure
  47. Surface Diffraction Effects from Nanopowders under Pressure
  48. Influence of high pressure on the polytype structure of nanocrystalline GaN
  49. Transformation of fractal microstructure of nanocrystalline SiC and diamond in high pressures - Small Angle Scattering Study
  50. Synthesis of Nanocomposites Based on Superhard Ceramic Nanopowders

Presentation: poster at E-MRS Fall Meeting 2003, Symposium B, by Svitlana Stelmakh
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-08-11 15:06
Revised:   2009-06-08 12:55