Sun Zhen-ya

Structure and property investigation of composite ZnO/SnO 2 nanocrystalline particles after high-pressure treatment

Composite ZnO/SnO2 nanocrystalline particles (ZnO/SnO2) were synthesized by sol-gel method and with treatment of high pressure at 6GPa. The crystallinity and the particle size of the prepared samples were analyzed by X-ray diffraction (XRD) spectroscopy. The results indicated that all the samples had the good crystallinity, and the particle size of ZnO and ZnO/SnO2 decreased after high-pressure treatment. The infrared (IR) spectra showed that the distance of crystal lattice was shortened after high-pressure treatment, and the size distribution became more uneven after SnO2 doping. With the high-resolution transmission electron microscope (HRTEM), we got some morphology information and evidence to support the IR and XRD analysis results. The results of ultraviolet-visible absorption (UV-Vis) spectra showed that ZnO/SnO2 might improve the photocatalytic property of the samples after high-pressure treatment.

Properties of nano SiO2 modified PVF adhesive

Some properties of nano SiO2 modified PVF adhesive were studied. The experimental results show that nano SiO2 can improve the properties of PVF adhesive very well. Meanwhile the modification mechanism of nano SiO2 to PVF adhesive and the applications of this adhesive in paper-plastic composite, concrete and fire-proof paint were discussed by using IR and XRD determination.

Preparation of High-Density Nanocrystalline Bulk Selenium by Rapid Compressing of Melt

The melts solidification behavior of elemental selenium is investigated by a series of experiments including rapid compressing to 2.8 and 3.5 GPa within 20ms respectively, slow compressing to 2.8 GPa for 20 min and natural cooling at ambient pressure. Based on the x-ray diffraction, scanning electron microscope and transmission electron microscope results of the recovered samples, it is clearly shown that homogenous nanostructures are formed only by the rapid compression processes, and that the average crystal sizes are about 18.7 and 19.0 nm in the samples recovered from 2.8 and 3.5 GPa, respectively. The relative density of the nanocrystalline bulk reaches 98.17% of the theoretical value. It is suggested that rapid compression could induce pervasive nucleation and restrain grain growth during the solidification, which is related to fast supercooling, higher viscosity of the melt and lower diffusivity of atoms under high pressure.

Preparation of Thermo-Stable Bulk Metallic Glass of Nd 60 Cu 20 Ni 10 Al 10 by Rapid Compression

Melt of Nd60Cu20Ni10Al10 alloy is solidified by rapid compression from 0.1 to 5.5 GPa at 793K and from 0.1 to 3.2 GPa at 873K within 20 ms, separately. A fully bulk metallic glass is obtained by the rapid compression method. By comparing with as-cast bulk metallic glass (BMG), it is found that Nd60Cu20Ni10Al10 BMG prepared by rapid compression exhibits a higher thermodynamic stability and a paramagnetic property. The relationship between the glass-formation temperature and the pressure in rapid compression for the BMG is demonstrated in the P – T phase diagram.

Preparation of Intercalated Clay/Phenolic Resin Nanocomposites under High Pressure

High pressure method was used for the first time to produce rectorite clay (REC)/phenolic resin (PF) and organic rectorite clay (OREC)/phenolic resin and montmorillonite (MMT)/phenolic resin (PF) nanocomposites. The structure of the material phase was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and atomic force microscopy (AFM). The experimental results show that intercalated clay/resin nanocomposites could form under normal temperature and high pressure conditions by the intercalation of polymeric molecules rather than interlayer polymerization.

Effects of high-pressure high-temperature sintering on the microstructures of Pb0.55Te0.45

The n-type nonstoichiometric Pb0.55Te0.45 materials were prepared by melting and quenching combined with a subsequent high pressure high temperature (HPHT) sintering. After adequately annealed at 623 K in the argon atmosphere, the microstructures and thermal transferring performance of the prepared samples have been systematically investigated. The results show that the grains of samples were apparently refined, as well as a large quantity of twisty layered structure and numerous particles with a size of ∼200nm distributing in the grain boundary can be observed. These refined microstructures significantly block the transports of phonons, and result in a remarkable reduction of the lattice thermal conductivity compared with the corresponding melting ingots.

Notice of Retraction Effects of high-pressure high-temperature sintering on the thermoelectric properties of Pb 0.55 Te 0.45

The n-type nonstoichiometric Pb0.55Te0.45 materials were prepared by melting and quenching combined with a subsequent high pressure high temperature (HPHT) treatment. After adequately annealed at 623 K in the argon atmosphere, the thermoelectric transport properties of the prepared samples have been systematically investigated. The results show that the pressure effectively adjusts the carrier concentration and its transport properties, and hence commendably tunes thermoelectric performances of the samples. Therefore, the maximum ZT of the sample treated by 2 GPa reaches 0.84 at 580 K, which is ~ 400% improvement in comparison with the melting ingot.