90
C. Balasubramanian
4.6 Preparation of Metal Nanoparticles
4.6.1 Tellurium Nanoparticles
As stated in the introduction part, metal nanoparticles can also be prepared by the
plasma process. Herein, preparation and analysis of tellurium nanoparticles is given
in detail. For metal nanoparticle preparation, it is essential the base vacuum of the
synthesis chamber is good. Though the operating pressure of the thermal plasma
synthesis route is atmospheric pressure, to avoid oxidation reaction, it is essential to
remove air/oxygen in the chamber and then fill with inert gases like argon or helium.
The level of base vacuum required is decided by the reactivity of the metal with
oxygen—especially at elevated temperatures. Higher the possibility of oxidation
reaction, the base vacuum required would be 10
−5 or 10
−6 mbar range.
For the Te nanoparticle synthesis, Te powder of micron size was placed in the
graphite crucible (which served as the anode) and with graphite rod as the cathode.
The chamber was evacuated to 10–4 mbar range vacuum and then filled with helium
gas till the pressure inside the chamber reaches 1 atmosphere. An arc current of
50 A was applied between the electrodes and synthesis done. The TEM analyses of
the samples indicated formation of pure Te nanoparticles with larger size of approximately 100 nm. X-ray diffraction analysis (shown in Fig. 12) of the samples indicated
the formation of highly crystalline tellurium structures.
Fig. 12 XRD spectra of tellurium nanoparticles
C. Balasubramanian
4.6 Preparation of Metal Nanoparticles
4.6.1 Tellurium Nanoparticles
As stated in the introduction part, metal nanoparticles can also be prepared by the
plasma process. Herein, preparation and analysis of tellurium nanoparticles is given
in detail. For metal nanoparticle preparation, it is essential the base vacuum of the
synthesis chamber is good. Though the operating pressure of the thermal plasma
synthesis route is atmospheric pressure, to avoid oxidation reaction, it is essential to
remove air/oxygen in the chamber and then fill with inert gases like argon or helium.
The level of base vacuum required is decided by the reactivity of the metal with
oxygen—especially at elevated temperatures. Higher the possibility of oxidation
reaction, the base vacuum required would be 10
−5 or 10
−6 mbar range.
For the Te nanoparticle synthesis, Te powder of micron size was placed in the
graphite crucible (which served as the anode) and with graphite rod as the cathode.
The chamber was evacuated to 10–4 mbar range vacuum and then filled with helium
gas till the pressure inside the chamber reaches 1 atmosphere. An arc current of
50 A was applied between the electrodes and synthesis done. The TEM analyses of
the samples indicated formation of pure Te nanoparticles with larger size of approximately 100 nm. X-ray diffraction analysis (shown in Fig. 12) of the samples indicated
the formation of highly crystalline tellurium structures.
Fig. 12 XRD spectra of tellurium nanoparticles