The rice husk powder was modified by polymer (lactic acid) (PLA) and Maleic anhydride (coupling agent, MAPP). Composite material was prepared in the way of melt blending. The mechanical properties, water absorbability of rice husk/polymer (lactic acid) (PLA) composites, and the relations between these properties and microscopic characteristics were investigated. The result showed that, with the increasing content of rice husk power, the maximum bearable tension and tensile strength increased; Water absorbability after 2 hours’ immersion hadn't significant change, but after 24 hours’ immersion, the water absorbing capacity had obvious addition. The study also showed that coupling agent could significantly reduce the water absorbability of composite materials; The use of scanning electron microscope (SEM) found that the interface became smoother, the adhesion between PLA and rice husk powder became closer when add the coupling agent to the rice husk powder, it also could well explain the differences between water absorbability and mechanical properties.

Exciton tunneling through ZnSe barrier layer of various thicknesses is invest igated in a novel Zn072Cd028Se/CdSe coupled quantum well/quantum dots (QW/QDs) structure using photoluminescence spectra and nearresonant pumpprobe mea surements. Fast exciton tunneling from quantum well to quantum dots is observed by transient differential transmission. The tunneling time is 18ps, 44ps, 39 ps for barrier thickness of 10nm, 15nm, 20nm, respectively.

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Abstract. By using Na2S•9H2O as source precursor and citric acid as stabilizer, ZnS:Mn nanocrystallines were synthesized by solvothermal method. They were annealed at 800 oC in the charcoal powder. The structure, morphology and optical properties were investigated by using X-ray diffraction spectra (XRD), scanning electron microscopy (SEM), and Spectrofluorophotometer respectively. The results showed that all unannealed ZnS:Mn nanocrystallines were about 3~5 nm of particle size and have cubic structure, and all annealed samples were about 30-70 nm of particle size and have mixed structure of the cubic phase and hexagonal phase. Moreover, Mn2+ took the place of Zn2+ in ZnS:Mn. With the increment of Mn2+ content, there occurred a strong emission peak at about 596nm which can be attributed to the Mn2 + leap from 4T1 to 6A1. In addition, the intensity of 596nm emission peak first increased and then decreased with the increment of Mn2+ content, reaching a maximum at about 15% of Mn2+ content. After annealing Mn2+ emission peak intensity is about 20 times that before annealing, and the luminescence peak also showed slightly blue shift.

A new type of (CdZnTe,ZnSeTe)/ZnTe complex quantum wells was designed. Exciton tunneling process was investigated in this complex structure using absorption spectra, photoluminescence (PL) spectra and pump-probe measurements. The exciton decay time was measured in CdZnTe/ZnTe quantum well layers and ZnSeTe/ZnTe quantum well layers, respectively. And a fast exciton tunneling from CdZnTe/ZnTe quantum well to ZnSeTe/ZnTe quantum well was observed by transient differential trans mission. The tunneling time is 5.5ps.