Temperature dependences of optical properties,chemical composition,structure,and laser damage in Ta2O5 films

Ta2O5 films are prepared by e-beam evaporation with varied deposition temperatures,annealing temperatures,and annealing times.The effects of temperature on the optical properties,chemical composition,structure,and laserinduced damage threshold(LIDT) are systematically investigated.The results show that the increase of deposition temperature decreases the film transmittance slightly,yet annealing below 923 K is beneficial for the transmittance.The XRD analysis reveals that the film is in the amorphous phase when annealed below 873 K and in thehexagonal phase when annealed at 1073 K.While an interesting near-crystalline phase is found when annealed at 923 K.The LIDT increases with the deposition temperature increasing,whereas it increases firstly and then decreases as the annealing temperature increases.In addition,the increase of the annealing time from 4 h to 12 h is favourable to improving the LIDT,which is mainly due to the improvement of the O/Ta ratio.The highest LIDT film is obtained when annealed at 923 K,owing to the lowest density of defect.     

纳米Sb2O3及其在云母表面的组装与阻燃性能

纳米Sb2O3及其在云母表面的组装与阻燃性能;Sb2O3; 纳米微粒; 云母; 阻燃; 氯化石蜡     

高岭土对不饱和聚酯树脂的热稳定性、阻燃及力学性能的影响

不饱和聚酯树脂;高岭土;纳米复合材料;原位聚合;阻燃;成炭     

Infrared Spectra and Pyrolysis of Selected Molecular Models of Coal: Insight from Density Functional Calculations

Equilibrium structures and infrared spectra of four typical molecular models of coal have been studied by density functional calculations. Combining theoretical calculations on the coal models with experimental FT-IR spectra of selected low rank perhydrous coals, a plausible molecular representation for this kind of coals was proposed, and its predicted IR spectra reasonably match the experimental observation. Calculations indicate that the cleavage of the C-C bridge bond for the coal structures considered here occurs at about 540 ℃ and the C-O ether bridge bond may break under temperature ranging from 500 to 600 ℃ for the aryl-CH2-O-CH2-aryl ether bond or from 200 to 300 ℃ for the aryl-CH2-O-aryl ether bond, showing remarkable effect of the local structural environment. The coal model containing the carboxyl group may release CO2 at about 300 ℃ through the decarboxylation with a barrier of 69 kcal/mol.     

Excellent polarization-independent reflector based on guided mode resonance effect

A broad band polarization-independent reflector working in the telecommunication C+L band is proposed using the guided mode resonance effect of a periodic surface relief element deposited by a layer of silicon medium. It is shown that this structure can provide high reflection (R>99.5%) and wide angular bandwidth (θ≈20°, R>98%) for both TE and TM polarizations over a wide spectrum band 1.5 μm～1.6 μm. Furthermore, it is found by rigorous coupled wave analysis that the polarization-independent reflector proposed here is tolerant of a deviation of grating thickness, which makes it very easy to fabricate in experiments.