Character and Preparation of Nano-SiO2/PI Composites by Sol-Gel Method

Polyimide/nano-SiO2 (PI/SiO2) composites with different contents of SiO2 were prepared by in situ polymerization. The transmittance, solubility, thermal property, flame retardant properties and mechanics properties of PI/nano-SiO2 composites were investigated. The results showed that with the increased addition of SiO2 content, the transmittance of PI/SiO2 compositions reduced; tensile strength changed with the amount of nanometer powder, when the addition content was 10 wt%, it achieve the maximum value. Thermal resistance of the composite was improved obviously while with the amount of nanometer powder increased, volume resistivity coefficient of volume resistance would have decreased.

The Physical Essence of Mono-dispersed Nanometer Particle Surface Energy by Boundary bond Interaction

ABSTRACTThe surface energy quantifies the disruption of intermolecular bond that occurs when a surface is created. The paper discusses critical size dc of mono-dispersed nanometer particle by analyzing the change of interfacial surface energy. The traditional theory neglects that the mono-dispersed nanometer particle has quantum standing wave in its internal structure with a size below critical dc. During the preparation of mono-dispersed nanometer powder, the large surface energy is formed ont only by cutting surface bond but also by forming quantum standing wave that opposites to interfacial edge unsaturated bond on the nanometer partcile surface atom. The preparation process of nanometer material needs more energy than the size surpass dc material. The new theory can explain why the melting point of nanometer powder decreases and other phenomina of nanometer material.

Research of Preparation and Ultraviolet Shielding for Nanometer Powder of Tin Dioxide Coated with Zinc Oxide

The preparation of tin dioxide coated with zinc oxide nanometer powder by factional homogeneous precipitation method is reported in this paper. The diameter of prepared nanometer powder is 32nm. UV shielding , XRD, SEM and EDS of prepared nanometer powder have been investigated. The results show that tin dioxide coated with zinc oxide nanometer powder has excellent UV-shielding performance , and the UV shielding characteristic is better than single tin dioxide or zinc oxide used.