Effects of Heat Treatment on Thermoelectric and Infrared Properties of Bi_2Te_3 Films

In this work,Bi2Te3 films（250 nm） are fabricated on Si O2/Si substrates by radio frequency（RF） magnetron sputtering at room temperature,and the prepared films are annealed over the temperature range of 200 °C to 400 °C.Crystallinity and electrical properties of the films can be tuned correspondingly.The power factors of Bi2Te3 films of 0.85 μW/K2 cm to 11.43 μW/K2 cm were achieved after annealing.The infrared reflectance measurements from 2.5 μm to 5.0 μm demonstrate that there is also a slight red-shift of the plasma oscillation frequency in the Bi2Te3 films.By means of plasmonic calculations,we attribute the red-shift of absorption peaks to the reduction of carrier concentration and the change of effective mass of Bi2Te3 films with the increased annealing temperature.

Out-of-Plane Magnetic Anisotropy and Microwave Permeability of Magnetoelastic FeCoSiB Amorphous Thin Films

Theamorphous magnetoelastic Fe66Co17Si1B6 thin films have been deposited by dc magnetron sputtering. A lot of ＂nano-trenches＂ have been observed on the fdm surfaces by AFM. The permeability of amorphous Fe66COlTSilB6 thin films was measured within the frequency range of 0.6GHz-10.2 GHz. The ferromagnetic resonance frequency was found to be 1.2 GHz. MFM shows that the domain of thin film is a maze-type pattern, which indicates that an out-of-plane magnetic anisotropy exists. The out-of-plane anisotropy is believed due to the stress-induced magnetic anisotropy. It can be inferred that the internal stress is tensile stress and normal to the film plane. Index Terms

Effective corrosion protection of magnetic microwave absorber with designed macromolecular network barrier

Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate type polymer network layers with thickness ranging from tens of nanometers to around one hundred nanometers were formed continuously around CI.The crosslinked coating layer(named FT)effectively increases CI’s thermal decomposition temperature by at least 34%.The FT-coated CI(named CI-FT)was able to resist both inorganic and organic corrosive media attacking efficiently compared with bare CI.The surface polymer network could also help CI withstand organic medium dissolution which proved the firmness of coating.Cyclic voltammetry(CV)test revealed that the coating layer could significantly reduce maximum oxidation current density of CI by more than 45 times.Tafel polarization study during CV tests also confirmed that thicker FT coating layer could help CI sample stabilize corrosion current density.Meanwhile,the surface coating also enhanced the impedance matching properties of CI as microwave absorber and the CI-FT samples demonstrated improved microwave absorption properties which degenerated little after corrosive medium soaking compared with that of CI.

Influence of filling atoms on radial collapse and elasticity of carbon nanotubes under hydrostatic pressure

Using molecular mechanics and molecular dynamics simulations, we focus on the influence of filling atoms on radial collapse and elasticity of single-walled carbon nanotubes(SWNTs). It is shown that the filled argon(Ar) and silicon(Si) atoms can effectively improve the resistance to high pressure and radial elasticity of SWNT, which may attribute to the strong repulsive force from the filled Ar(Si) atoms. However, due to the strong interaction of Cu atoms, filling Cu atoms deteriorate SWNT's radial elasticity. In addition, it is found that the phase transitions of the atoms filled in SWNT occur in the process of loading and unloading pressure, so that the electrical properties of the SWNTs filled with atoms change in the process of loading and unloading pressure. In view of the restorability of SWNT filled with Si atoms upon unloading, the filled SWNTs can be used to develop a new class of nano-electronic devices such as pressure sensor, relay and memory, etc.

Strategy to boost hydrolysis resistance and stabilize low infrared emissivity of ZrB_(2) via nanoscale LaF_(3) surface modification

Owing to its excellent high-temperature resistance and high conductivity,zirconium diboride(ZrB_(2)) has been applied as an infrared suppression coating.However,ZrB_(2)is susceptible to hydrolysis under high-moisture conditions and even under mild working temperatures.The improvement in the hydrophobicity of the ZrB_(2)surface effectively reduces wetting by water and suppresses hydrolysis reaction,particularly under high-temperature and high-moisture conditions.Herein,we report a novel,easy,and highly reproducible method for producing a fully coated ZrB_(2)surface by developing a nanoscale hydrophobic layer of glassy LaF_(3)on the surface of ZrB_(2)powder particles in situ(i.e.,during the carbothermal synthesis of ZrB_(2)).Through the tests carried out at 200 ℃for 100-300 h in a hydrothermal reactor,the produced powders displayed remarkably high long-term hydrolysis resistance and pronounced chemical stability.Compared with treated ZrB_(2),ZrB_(2)@LaF_(3)remained lower infrared emissivity when continuously intensifying hydrolyzation process.The results suggest that a nanoscale surface modification strategy can be applied to stabilize the infrared emissivity of ZrB_(2)in a water-oxygen coupling environment.