L.Y. Zhang

Preparation and optical properties of TiO2 nanocrystalline particles dispersed in SiO2 nano-composites

Abstract Nano-composites of TiO 2 nanocrystalline particles dispersed in SiO 2 have been successfully prepared by the two-step hydrolysis of Si(OC 2 H 5 ) 4 derived by the sol-gel technique using TiO 2 ultrafine powder as a active component. The influence of processing factors has been investigated; a two-step rapid gelation method in sol-gel processing has been developed. The optical absorption spectrum and the third-order nonlinear susceptibility χ (3) of the nano-composites were measured, the highest χ (3) of the sample was 4.1 × 10 −11 esu measured by the DFWM method.

Optical properties of sol-gel derived lead titanate nanocrystallites in silica glass

Abstract Lead titanate nanocrystallites in silica glass have been successfully prepared by sol–gel process. The influence of heat treatment on optical absorption and energy gap was studied. The optical energy gap of sample was shifted about 0.2 eV due to nanocrystallite size effect. The nonlinear refractive index, n2, of the silica glasses with lead titanate concentration of 45% (weight fraction), was measured by a generated four-wave mixing (DFWM) technique. An n2 value as high as 2.86×10−18 m2/W was obtained. It is about 200 times larger than fused glasses.

Experimental Study on Enhanced Falling Film Absorption Process Using H2O/LiBr Nanofluids

Absorption air conditioning system could be driven by low grade energy, such as solar energy and industrial exhaust heat, for the purposes of energy conservation and emission reduction. Its development is limited by its huge volume and high initial investment. The nanofluids, which possess the superior thermophysical properties, exhibit a great potential in enhancing heat and mass transfer performance. In this paper, nanofluids of H2O/LiBr with Fe3O4 nanoparticles were introduced into absorption air conditioning system. The effects of some parameters, such as the flow rate of H2O/LiBr nanofluids, nanoparticle size and mass fraction, on the falling film absorption were investigated. The H2O/LiBr nanofluids with Fe3O4 nanoparticle mass fractions of 0.01 wt%, 0.05 wt% and 0.1 wt%, and nanoparticle size of 20 nm, 50 nm and 100 nm were tested by experiment. The results imply that the water vapour absorption rate could be improved by adding nanoparticles to H2O/LiBr solution. The smaller the nanoparticle size, the greater enhancement of the heat and mass transfer performance. The absorption enhancement ratio increases sharply at first by increasing the nanoparticle mass fraction within a range of relatively low mass fraction, and then exhibits a slow growing even reducing trends with increasing the mass fraction further. For Fe3O4 nanoparticle mass fraction of 0.05wt% and nanoparticle size of 20nm, the maximum mass transfer enhancement ratio is achieved about 2.28 at the flow rate of 100 L·h−1.Copyright