Morphology uniformity control

Yanyan X., Shuang Y, Guoying Z., Yaqiu S., Dongzhao G. and Yuxiu S. (2011). Uniform hematite a-Fe Oj nanoparticles Morphology, size-controlled hydrothermal synthesis and formation mechanism. Mater Lett, 65( 12), 1911 -1914. 

Properties of materials are largely dependent on size and morphology, so control over synthetic methodologies is important. This is because the growth of the materials in nanoscale is largely dependent on the thermodynamic and kinetic barriers in reactions, as defined by the reaction trajectory and influenced by vacancies, defects and surface reconstruction. The simultaneous control of particle size and shape together with their uniformity is one of the key objectives in many synthetic procedures. In the present chapter, new developments in various preparation methodologies for the fabrication of ceria-based materials are addressed. The reactivity of ceria-based nano-oxides for non-selective oxidation or catalytic combustion or oxidation reactions is also discussed. 

TPEs from thermoplastics-mbber blends are materials having the characteristics of thermoplastics at processing temperature and that of elastomers at service temperature. This unique combination of properties of vulcanized mbber and the easy processability of thermoplastics bridges the gap between conventional elastomers and thermoplastics. Cross-linking of the mbber phase by dynamic vulcanization improves the properties of the TPE. The key factor that controls the properties of TPE is the blend morphology. It is essential that in a continuous plastic phase, the mbber phase should be dispersed uniformly, and the finer the dispersed phase the better are the properties. A number of TPEs from dynamically vulcanized mbber-plastic blends have been developed by Bhowmick and coworkers [98-102]. 

We found recently that the viscosity (//vac) of the colloidal thiolate precursor is a key parameter in controlling the shape of the nanoproducts in the solventless method [8]. Uniform nanowires, rods, or spheres could be made from the corresponding precursors that came from the solutions with different viscosities. The viscosity is a measure of the polymerization of the metal-thiolate complexes. Accordingly, the precursor with the highest viscosity produces nanowires (Fig. 20.5 a), and with decreases in the viscosity, the product morphology changes to rods (Fig. 20.5b) and then spheres (Fig. 20.5c). 

Morphology of the enzymatically synthesized phenolic polymers was controlled under the selected reaction conditions. Monodisperse polymer particles in the sub-micron range were produced by HRP-catalyzed dispersion polymerization of phenol in 1,4-dioxane-phosphate buffer (3 2 v/v) using poly(vinyl methyl ether) as stabihzer. °° ° The particle size could be controlled by the stabilizer concentration and solvent composition. Thermal treatment of these particles afforded uniform carbon particles. The particles could be obtained from various phenol monomers such as m-cresol and p-phenylphenol. 

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