Polypropylene (PP)/microcrystalline cellulose (MCC) composites and PP/MCC composites modified by maleic anhydride grafted PP (PP-g-MA) and methyl acrylic acid glycidyl ester grafted PP (PP-g-GMA) respectively were prepared in a twin-screw extruder. The mechanical properties, morphology, and thermal performance were investigated. The nonisothermal crystallization, melting behavior, and nonisothermal crystallization kinetics were investigated by DSC. The results indicated that the addition of MCC had led to the increase of the tensile strength, impact strength, and flexural strength of PP. PP-g-GMA modification was more conducive to the improvement in tensile strength, impact strength, and flexural strength. The three types of PP/MCC composites have higher thermal decomposition temperatures, Vicat softening temperatures, and dimensional stability. Nonisothermal crystallizations of PP/MCC composites were in accordance with tridimensional growth with heterogeneous nucleation. Meanwhile, MCC was acted as the nucleating agent in PP matrix, which increased the crystallization temperature. PP-g-GMA further increased the crystallization temperature while PP-g-MA weakened the heterogeneous nucleation effect of MCC. Avrami equation and Mo method give a satisfactory description of the crystallization kinetics process. The activation energy of crystallization, nucleation constant, and fold surface free energy of PP were markedly reduced in PP/MCC composites and its compatibilized composites. The value of F( T) systematically increased with increasing relative degree of crystallinity. The addition of microcrystalline cellulose has greatly reduced the spherulitic size of PP.
Using Sn and SnO powder as source material, SnO2 one-dimensional nanostructures (nanowires, nanorods, nanobelt and nanoneedles) with controllable diameters were successfully prepared by chemical vapor deposition. The nanostructure and morphology of the products depend strongly on the proportion of oxygen in the growth chamber, which can be altered by adjusting the proportion of SnO in the source material or the proportion of oxygen in the carrier gas. It is crucial to adjust the relative contents of Sn and O atoms in the region of high temperature growth of the Si wafer during controlled preparation of SnO2 one-dimensional nanostructures. We will also discuss the growth mechanism of SnO2 one-dimensional nanostructures under different growth conditions.
Large-area (10 mm×10mm), vertically aligned α-Fe2O3 one-dimensional nanostructure (nanobelts and nanowires with controllable diameters) arrays are successfully synthesized by thermally oxidizing iron foil directly, which grow in the [110] direction of the hexagonal crystal. The morphology and microstructure of the synthesized arrays depend strongly on the growth conditions such as the oxygen pressure, temperature and reaction time. We found that the growth of α-Fe2O3 one-dimensional nanostructures follows a top-growth mechanism, in which the ratio of iron and oxygen atoms near the point of growth plays a key role.
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