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Carbon spheres with size of 50−300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform as reactants in a sealed autoclave. The morphologies and microstructures of carbon spheres before and after high temperature treatment (HTT) were characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), energy diffraction spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of carbon spheres was discussed. The results indicate that the carbon spheres convert to hollow polyhedron through HTT. Carbon spheres are composed of entangled and curve graphitic layers with short range order similar to cotton structure, and carbon polyhedron with dimension of 50−250 nm and shell thickness of 15−30 nm. The change of solid spheres to hollow polyhedron with branches gives a new evidence for formation mechanism of hollow carbon spheres.

Considerable effort has been exerted using theoretical calculations to determine solid surface energies. Nanomaterials with high surface energy depending on morphology and size exhibit enhanced reactivity. Thus, investigating the effects of morphology, size, and nanostructure on the surface energies and kinetics of nanomaterials is important. This study determined the surface energies of silver phosphate (Ag3PO4) micro-/nanocrystals and their kinetic parameters when reacting with HNO3by using microcalorimetry. This study also discussed rationally combined thermochemical cycle, transition state theory, basic theory of chemical thermodynamics with thermokinetic principle, morphology dependence of reaction kinetics, and surface thermodynamic properties. Results show that the molar surface enthalpy, molar surface entropy, molar surface Gibbs free energy, and molar surface energy of cubic Ag3PO4micro-/nanocrystals are larger than those of rhombic dodecahedral Ag3PO4micro-/nanocrystals. Compared with rhombic dodecahedral Ag3PO4, cubic Ag3PO4with high surface energy exhibits higher reaction rate and lower activation energy, activation Gibbs free energy, activation enthalpy, and activation entropy. These results indicate that cubic Ag3PO4micro-/nanocrystals can overcome small energy barrier faster than rhombic dodecahedral Ag3PO4micro-/nanocrystals and thus require lower activation energy.

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The relaxation of a one-dimensional magnetic nanoparticle linear chain with lattice constant a is investigated in absence of applied field. There is an equilibrium state (or steady state) where all magnetic moments of particles lie along the chain (x-axis), back to which the magnetic nanoparticle chain at other state will relax. It is found that the relaxation time Tx is determined by Tx = 10 β × a 3 . This relaxation is compared with that of single magnetic nanoparticle system.