The Synthesis Of Tantalum Nitride Nanomaterials By DC Arc Discharge Plasma And Their High-pressure Studies

Nanomaterials and technology is a very vigorous and abundant branch of science in the regions of Nano-ST. Nanomaterials have a big specific surface area, and atomicity of surface, surface energy and surface tension quick increase with the decline of the size of particles. The light-sized effect, surface effect, quantum size effect and macroscopic quantum tunnel effect induce the difference of heat, light, magnetism, character of sensitivity and stability of surface between the nanomaterials and general materials. Therefore the nanomaterials have a wider foreground of appliance. The size of nanoparticles about 5～50nm are possible fabricated to nanomaterials under high pressure, coats of nanoparticles and function films of nanomaterials. So the nanoparticles attract more and more attentions of people. Because the synthesized techniques and methods have a big influence on the structure and capability of nanoparticles, the synthesized techniques and methods of nanoparticles have an important effect on the research region of Nanomaterials and technology. In order to fabricate near perfect nanoparticles in recent years, people take any high technology ways to exploit new fabricated methods. Transition metal nitrides belong to a class of interstitial compounds, in which the nitrogen atom was dissolved into the metal lattices. Transition metal nitrides have various unique properties such as good chemical stability, high strength, high hardness, high melting point, low electrical resistivity and high thermal conductivity, which have gained considerable interests. Therefore, transition metal nitrides have attracted much attention more and more. As an important candidate of these interstitial compounds, tantalum nitride has been found to be a promising material for many applications such as diffusion barrier, wear and corrosion-resistance, high speed thermal printing head, as well as precise and stable resistor used in silicon-based integrated circuits. What is more, Papaconstantopoulos et al. theoretically predicted the cubic TaN have high superconducting critical temperature.The high pressure physics give birth to new opportunity followed the rapid development of nanomaterials. The essential effect of pressure is to reduce interatomic distance, which leads to modification in lattice constants of crystalline material as well as to change inatomic positions within crystallographic cells. As a result, there is form a new phase of materials in physical properties and optical properties. Therefore the research of physical and optical properties has gained considerable interests.In this paper, the single-phase cubic TaN and h-Ta2N nanocrystallites were first obtained by dc arc plasma method, respectively. The XRD, TEM, XPS, FTIR techniques are used to characterize the as-synthesized sample. The growth mechanism of the as-synthesized sample was discussed. Furthermore, we study the high pressure behavior of cubic TaN nanocrystallites and h-Ta2N nanocrystallites by a diamond anvil cell and synchrotron radiation X-ray diffraction. We obtain main innovative results as follow.(1) It is difficult to synthesize single-phase cubic TaN by conventional methods, such as evaporation Ta in N2, because Ta has a high melting temperature and the lowest reactivity towards N2, In our experiment, the single-phase cubic TaN nanocrystallites were first obtained at lower N2 pressure by direct reaction between solid Ta and N2 using the dc arc plasma method. The XRD and TEM techniques are used to characterize the as-synthesized sample. The average size of cubic TaN nanocrystallites is about 5-10 nm. An intense and broad band was show in the FTIR spectroscopy of cubic TaN. The broadness of the absorption peaks in the IR spectra can be explained the existence of a size and shape distribution and the effects of defects and interfaces of the nanostructured crystals.(2) In our experiment, the single-phase Ta2N nanocrystallites were first obtained by direct reaction between solid Ta and mixture gas (N2–NH3) using the dc arc plasma method. We obtain the optimal conditions of nucleation are I=100 A, V=30V, P=10kPa and a mixed gas (20% NH3-80% N2) through many experiments. The XRD and TEM techniques are used to characterize the as-synthesized sample. The average size of single-phase Ta2N nanocrystallites is about 5-10 nm. There also is a intense and broad band in the IR spectra.(3) We firstly carried out in situ XRD studies of cubic TaN and Ta2N nanocrystallines under high pressure using a diamond anvil cell and a synchrotron radiation source. The high pressure up to 59.5 GPa and 55.48GPa, respectively. The fitting P-V data results by Birch-Murnaghan equation for cubic TaN and Ta2N nanocrystallines give the bulk modulus of nanocrystallines. This implies that the incorporation of N atom into TaN and Ta2N make their bulk modulus higher than that of metal Ta, which are accord with first principle calculation results.