Sintesis Polianilin yang Diperkaya γ-Fe2o3 dari Pasir Besi Lokal Sulawesi Tenggara untuk Aplikasi

This research is aimed to develop the radar absorbing material based on polyaniline enriched by γ-Fe2O3 synthetized from the sandstone. γ-Fe2O3 is, then, derived from calcination process of Fe3O4 powder at the temperature of 400-600oC. Fe3O4 powder itself is extracted from the local sandstone of South East Sulawesi area by using the co-precitipation method with both HCl and NH4OH act as the solvent and precitipation agent, respectively. The polyaniline is synthetized from its monomer, aniline, where both HCl and NH4OH are also used as a dopant and an oxydator agent, respectively. Effect of reaction pH on the crystal size of Fe3O4 is also investigated. The XRD spectrum shows that a rather high purity of Fe3O4 in nano size is being achieved at the pH value of 8 and 9. However, at a rather low pH value (6.5 and 7.5), the additional weak peaks in XRD spectrum shows the existence other metal compounds impurity. The crystal sizes is approximately ~8.01 and 11.07 nm for pH value of 8 and 9. The VSM measurement result shows that the saturated magnetization value of Fe3O4 is 24.45 emu/g. The Fe3O4 is calcined at temperature of 500oC for 3 hours to get γ-Fe2O3. Finally, the polyaniline-γ-Fe2O3 composites were synthetized using an insitu polymerization method where the weight contents of γ-Fe2O3 are 5, 10, 15, and 20 percent. Those materials will be useful as a prospective application in radar absorbing materials technology at frequency ranges of 9-17 GHz

Reflections in gyrotrons with axial output

Influence of reflections on operation of gyrotrons with axial output is studied both theoretically and experimentally. By way of example the Fukui large orbit gyrotron with a permanent magnet operating in third harmonic at frequency 89 GHz is considered. In the case of strong reflection (|R|=0.6), extreme sensitivity of output power on the reflection phase is found. A qualitative agreement between theory and experiment is observed

Formation Mechanisms of Co-existence of α-Fe and Iron Oxides Nanoparticles Decorated on Carbon Nanofibers by a Simple Liquid Phase Adsorption-Thermal Oxidation

We propose formation mechanisms of co-existence of α-Fe and iron oxides nanoparticles decorated on CNFs. The α-Fe nanoparticles are produced via oxidation-reduction mechanisms, which occur in liquid phase adsorption (LPA) assisted by ultrasonic energy, while α-Fe2O3 nanoparticles are thermally formed through mechanisms of Lewis acid-base. In addition, Fe3O4 is thermally formed by reducing Fe2O3 by CNFs. Liquid phase adsorption assisted by ultrasonic energy under ambient temperature using Fe(NO3)3•9H2O as a precursor of iron oxides and α-Fe has been applied. Then, as prepared, Fe(III)@CNFs were thermally calcined at 573 K under air atmosphere in various holding times ranging from 0.5 to 2 h. XRD data confirmed that α- Fe2O3 and Fe3O4 had been successfully grown onto CNFs. Moreover, the presence of the iron oxides and iron nanoparticles was studied by the SEM-EDX technique. The iron oxide nanoparticles appeared after a heating period of 0.5h. However, at a holding time of 0.5 h, we found an exciting and unexpected phenomenon where oxygen content is zero percent while Fe is 0.23 wt %. It implies that α-Fe nanoparticles were formed earlier than α-Fe2O3 and Fe3O4 as the proposed mechanisms. Formation mechanisms of iron and its oxides such as α-Fe2O3 and Fe3O4 decorated on CNFs through liquid-phase adsorption followed by thermally treatment technique in this work is expected to give significant contribution in the field of nanocomposite materials, especially for anode materials based on iron oxides