Morphology and optical absorption of Bi2Fe4O9 crystals via mineralizer-assisted hydrothermal synthesis

Submicron-sized Bi₂Fe₄O₉ crystals were successfully synthesized via the hydrothermal method,while micron-sized Bi₂Fe₄O₉ crystals with rod-like morphologies were obtained in the presence of the mineralizer KNO₃.X-ray diffraction,scanning electron microscopy and transmission electron microscopy were employed to characterize the products.According to a series of time-dependent experiments,it was concluded that the likeliest formation mechanism for the microrods was the Ostwald ripening process.It was proposed that the blocking effect of NO₃^- contributed to the formation of the rod-like powders.Moreover,the optical absorption of the prepared Bi₂Fe₄O₉ crystals was measured using an UV-vis spectrophotometer,indicating that Bi₂Fe₄O₉ powders can be used as effective photocatalysts under visible light.     

Uneven splitting-ratio 1×2 multimode interference splitters based on silicon wire waveguides

Two types of 1×2 multi-mode interference(MMI) splitters with splitting ratios of 85:15 and 72:28 are designed.On the basis of a numerical simulation,an optimal length of the MMI section is obtained.Subsequently,the devices are fabricated and tested.The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3(μm).The minimum excess losses are 1.4 and 1.1 dB.The results of the test on the splitting ratios are consistent with designed values.The devices can be applied in ultra-compact photonic integrated circuits to realize the "tap" function.     

Study of catalytic effect of ammonium molybdate on the bisphthalonitrile resins curing reaction with aromatic amine

A kind of catalyst, ammonium molybdate was developed in this paper to promote the curing reaction of bisphthalonitrile resins with aromatic amine as curing agent, and the catalytic effect was studied by differential scanning calorimetry (DSC), rheometric measurements and thermogravimetric analysis (TGA). The results indicated that the catalyst could improve the curing rate and increase the curing degree, which could be regulated by the content of the catalyst used in the reaction.