Electric pulse current (EPC) was employed to treat ZA27 alloy cast in the sand mould during the solidification. The experiment results indicated that the shrinkage cavity and the porosity in the ZA27 alloy was apparently reduced. And correspondingly, the mechanical properties of the castings were certainly improved. The current pulse applied in the initial stage of the solidification produced a better treatment result. The density of the casting ZA27 alloy treated with EPC in initial stage and later stage increased by 4.1 and 1.6 percent than that without EPC, respectively.

AB ST R ACT : In order to improve the optical properties and enhance the stability of Zn 1Àx Cd x S nanoparticles, which are important optoelectrical materials, the ternary Zn 1Àx Cd x S nanoparticles were enclosed in a layered octosilicate by a three-step process, namely (i) protonation of Naoctosilicate, (ii) ion-exchange in order to introduce Zn and Cd ions into the interlayer space, and (iii) addition of S 2À to form Zn 1Àx Cd x S particles in the interlayer space of the octosilicate. The basal spacing (~10 Å ) of the final ZnCdS-Oct-n (n = 1, 2, 3, 4) composites noticeably increased in comparison with that of the precursor H-Oct (7.5 Å ). This may be attributed to the incorporation of larger size Zn 1Àx Cd x S particles into the interlayer space of H-Oct. The UV-visible spectra of the composites suggested that the transmission band-edges gradually shifted to low energy with increasing molar ratio of Cd/Zn. Moreover, the transmission band-edges of the composites are between those of layered Octosilicate, ZnS, and CdS. TEM observation confirmed that the size of Zn 1Àx Cd x S nanoparticles enclosed in the layered silicate was about~3À5 nm.

In the paper, the polyurethane/carbon nanotubes composites were prepared by solution-blending method. The polyurethane dissolution, carbon nanotubes dispersion agent, dispersion method and preparation of composites were analyzed. The results showed that the tetrahydrofuran and N-N-dimethylfomamide could used as the dissolution of polyurethane. The dissolution is most even with the ratio of tetrahydrofuran and N-N-dimethylfomamide of 1:1, and 1g polyurethane grains were resolved with 20ml solutions about 72 h. The N-N-dimethylfomamide was used as dispersion agent of carbon nanotubes by ultrasonic dispersion about 2h. The producing process of polyurethane/carbon nanotubes composites was successively heating, drying, and solidifing in the air, so the smooth surface could be received. The results indicated that the dispersion effect from good to poor is ultrasonic dispersion, magnetic dispersion and machining dispersion. With extension in time and increasing disperse frequency, the dispersion effect is better and better. But it also presented that the carbon nanotubes were reunited by magnetic and ultrasonic dispersion after the certainly scattered time, their best dispersion time were respectively two hours and one and a half hours.

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