Dissertation > Excellent graduate degree dissertation topics show

First-principles Study on the Influence of Doping on the Strength of Super-hard Materials

Author: LiangFuHong
Tutor: XuChangShan
School: Northeast Normal University
Course: Condensed Matter Physics
Keywords: W-BN DFT First-principles Volume elastic modulus Double-faces stress
CLC: O469
Type: Master's thesis
Year: 2011
Downloads: 17
Quote: 0
Read: Download Dissertation

Abstract


With the rapid development of modern science and technology, there’s an increased demand for the hardness of materials. In the many properties of materials, hardness is one of the most important and basic index of performance. The synthesis and research of superhard materials have been given more and more attention.Since the discovery of diamond in the 19th century, people believed that diamond is the hardest material in the world. But in 2009, Professor Sun Hong found that two nanocomposites (W-BN and C-BN) can come up to the hardness of diamond. The two substances are both hexahedral structure, the resistance to pressure are from the elastic valence bond, which will turn into 90 degrees to reduce pressure.The purpose of this work is to investigate the effects of C, N, Si, O doping in W-BN. The double-faces stresses (vertical and tangential stress) of the measuring tool in the hardness experiments, especially the vertical pressure, are accounted for. It is the positive pressure that greatly enhances the shear strength. The strain is not obvious when the forces is weak, the intensity increased with the increase of the external force, but it decreased when the external force reaches a certain degree, but after that, the structure of the crystal shows a big change, causing a remarkable increase of the strength.

Related Dissertations

  1. Density Functional Theory Study of Dimethyl Ether Adsorption on the Low-Index Pt Surface,O485
  2. Reactive Hot-Pressing and Mechanical Properties of （ZrB2-ZrO2）/BN Composites,TB332
  3. The Algorithm of DFT with a Subset of Output Points Based on TS101 and Its Software Implementation,TN911.72
  4. Study and Preparation of BaTiO3-based NTC Ceramic Thermistors,TQ174.1
  5. First- principles calculations of doped anatase titanium dioxide photocatalytic properties,O643.36
  6. First-Principles Studies of Blacl Phosphorus and LiMn2O4 as Electrode Material for Lithium Ion Batteries,TM912
  7. First-Principles Studies of Cathode Material LiMO2 （M=Co, Ni, Mn） of Lithium Ion Batteries,TM912
  8. Theoretical Studies on Cyclization Mechanism and Regioselectivities of Selected Organic Reactions,O643.12
  9. Hydrogen complex photochemical Theoretical Study,O641.1
  10. Pyridine Metal Complexes electronic spectra and redox properties of theoretical research,O627
  11. Eu- doped α-SiAlON phosphor First-principles study,TB34
  12. First-principles study of the structure and optical properties of the high-pressure alkali metal (Li, Na, K),O521.2
  13. A Density Functional Theory Study for Wn C0,± （n=1-6） Clusters,O641.1
  14. A Study for Structure and Properties of OsnN0, ± （n=1-6） Clusters,O641.1
  15. Flavonoids hydration and antioxidant molecules Quantum chemical study,TQ460.1
  16. Study of Intelligent Control on Power Phase Test Technology,TP368.1
  17. Implementation of DFT Based on First-order Moments Using FPGA,TN911.72
  18. First-principles Study on Magnetic and Optical Properties of Rutile TiO2,O614.411
  19. Preparation and Properties of ZnO-based Diluted Magnetic Semiconductors,TN304.21
  20. Hexagonal boron nitride micro- structure and adsorption properties of,TB383.3

CLC: > Mathematical sciences and chemical > Physics > Condensed Matter Physics
© 2012 www.DissertationTopic.Net  Mobile