The effect of pressure ranging from ambient atmosphere to 28.5 MPa on the free radical polymerizations of methyl methacrylate (MMA) in carbon dioxide (CO 2 ) was investigated and discussed. The poly (methyl methacrylate) (PMMA) with high molecular weight was synthesized at quite high conversion of MMA in the polymerization at or below 9.2 MPa, as compared to those polymerized under 11.8-28.5 MPa. A phase transition behavior of MMA-CO 2 binary mixture from homogeneous state to vapor-liquid equilibrium (VLE) state was observed below 10.51 MPa. In such a VLE system, almost all MMA was found to exist in the liquid phase with higher concentration than that in homogenous system. Thus, the fast polymerization rate of MMA and high molecular weight of PMMA could be related to the VLE state of MMA/CO 2 under low pressure. Similar phenomena were also observed in the polymerization systems of styrene and vinyl acetate in CO 2 , respectively.
Cobblestone-like CoSb3 nanoparticle films have been achieved via a catalyst-free vapor transport growth technique. The thermoelectric properties of the nanoparticle films were measured from room temperature to around 500 oC. The resultant CoSb3 nanoparticle films show high electrical conductivities due to clean particle surfaces. A maximum power factor reaches 1.848×10−4 W/mK2 at 440 oC. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.
To understand the effects of environmental factors, such as the light intensity, reaction time, the concentration of reactant on the growth of secondary organic aerosol is very important. This paper investigated the effect of environmental factors on SOA formation from biogenic volatile organic compounds (BVOCs), results show that SOA formed from OH-initiated photooxidation of BVOCs is predominantly in the form of fine particles, which have diameters less than 2.5 µm. This paper also highlighted that both the number and mass concentration of SOA particles were increasing with the prolonging of the radiation time, the increasing of light intensity, and the increasing of the reactant concentrations. The results could provide useful information to infer possible emission sources of atmospheric particles in future field measurement.
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