An Research on Solid-phase Combustion Synthesis of Metal Nitride
| Autor: | Chuang, H. C., 莊賀傑 |
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| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 The self-propagating high-temperature synthesis (SHS) of titanium nitride (TiN), niobium nitride (NbN) and vanadium nitride (VN) was studied. Effects of nitrogen pressure in the range of 0.27 ~ 1.48 MPa, sample density and diluent concentration on the flame-front velocity, combustion temperature and conversion percentage of combustion products were investigated. The influence of preheating was also discussed in V-N2 system. It was found that all these three kinds of SHS processes were characterized by afterburning reaction. The spin-burning phenomenon was observed in Nb-N2 and part of V-N2 experiments. The combustion process indicated melting in Ti-N2 and V-N2 systems. The flame-front propagation velocities increased with nitrogen pressure, but decreased with sample density. The increase in diluent concentration led to a noticeable decrease in flame-front propagation velocities. The flame-front propagation velocities in this study were in the region between 0.9 and 34.3 mm/s. The activation energies of SHS processes associated with Nb-N2 and V-N2 systems were calculated to be 38.81 and 133.92 kJ/mole, respectively, based upon the measurement of flame-front velocity and combustion temperature. The degree of conversion from metal to nitride was substantially affected by the dilution with product nitride in the metal reactants. The conversion percentages of TiN, NbN and VN were found to be enhanced up to about 83.7%, 71.8% and 76.4%, respectively, by the addition of diluents. The results of X-Ray Diffraction (XRD) analysis indicated the existence of unreacted metal in the products while samples were undiluted. It also found β-Nb2N and β-V2N in the products of Nb-N2 and V-N2 systems, respectively. The burned samples with diluent were composed mainly of stoichiometric metal nitrides. The microstructures of synthesized products shown by Scanning Electron Microscope (SEM) photographs indicated the formation of liquid phase in Ti-N2 and V-N2 systems. However, the Nb samples remained in solid phase during the SHS process. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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