Vanadium dioxide exhibits a reversible crystal transition from monoclinic phase to rutile phase, but the quantitative regularity of the effect of particle size on crystal transition thermodynamics still remains unclear. Herein, a new core−shell model was proposed and the universal equations for size-dependent crystal transition thermodynamics have been deduced. Experimentally, we researched the crystal transition behaviors of VO 2 (M) with different particle sizes. The results indicate that with the particle size of nano-VO 2 (M) decreasing, the temperature, enthalpy, and entropy of the crystal transition decrease, and these thermodynamic properties are all linearly related with the reciprocal of particle radius, which are consistent with the theoretical formulas. More importantly, by using the quantitative influence regularity of the particle size on the crystal transition temperature, we can obtain different crystal transition temperatures for different applications by purely controlling the particle sizes.

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The synthesis, crystal structure, nonlinear optical (NLO) property and some other properties of a new material, Hg(2)BrI(3), are reported. The crystal structure has been established by single crystal X-ray diffraction studies. Hg(2)BrI(3) belongs to the HgBrI type and crystallizes in the orthorhombic space group Cmc21 (No. 36). The compound shows a phase-matchable second harmonic generation (SHG) of about 1.2 times as strong as that of KTiOPO(4) (KTP) based on the powder SHG measurement. It exhibits a wide transparency in the IR region (from 2.5 to 30 μm), and a good thermal stability. It is believed that Hg(2)BrI(3) is a new candidate for NLO materials in the IR region.

in Wiley Online Library (wileyonlinelibrary.com) Asphaltene precipitation has been a major concern for petroleum industry due to its adverse effect on upstream production, midstream transportation, and downstream refining. As a complex phenomenon involving solubility, aggregation, and clustering, asphaltene precipitation has been extensively investigated and correlated with empirical models and equations. Based on the insight regarding hierarchical structure of asphaltenes recently elucidated by Mullins, we present a thermodynamic formulation for asphaltene aggregation, the onset of asphaltene precipitation. The thermodynamic formulation accounts for asphaltene aggregation driving force as a two-step process: (1) molecular asphaltene forming imaginary "nanocrystals", and (2) "nanocrystals" re-dissolving as colloidal nanoaggregates. Applying UNIFAC with this thermodynamic formulation, we show semi-quantitative predictions of asphaltene precipitation in 13 binary solvents with wide varieties of chemical structures and solvent combinations.

A new ring-like VO2 (M) was successfully synthesized for the first time by a template-free hydrothermal method, and the formation mechanism of the ring-like structure through aggregation of nanocrystals around the bubbles was proposed. Furthermore, the crystal transition temperature of ring-like VO2 (M) exhibits a more distinct size effect compared to nanoparticles. The results here point to the importance of carefully controlling the morphology of VO2 (M) to tune the crystal transition.