Bo Zhou,Wei Wang,Zhendong Zhou,Xiangdong Liu,Yongping Chen
The hollow polymer spheres preparation technique of micro-encapsulation requires quantative and precise understandings of the complex evaporation, gelation and solidification processes of the polymer solution. This study focused on the mass transfer during the evaporation-gelation process of a PS-benzene solution inside a Stefan tube. Liquid level reductions of polymer solutions were accurately measured using an image-recognition method with 50 μ m accuracy. An evaporation model was developed to successfully predict the variation of liquid level, concentration and mass transfer flux, considering solution activity and density as lumped parameters that depend on concentration. This carefully validated evaporation model is expected to be invaluable for the analysis and design of polymer solution evaporation, accommodating various geometries and boundary conditions. Despite the observation of complex processes such as precipitation of polymer molecules and solution-gel phase separation, we characterized and explained them using the effective concentration-density relation. The study showed that reaching a mass fraction of benzene of 0.6 is a significant event in the evaporation process, indicating the end of gelation and the beginning of solidification.
Wei Chen,Chaoxing Wu,Tailiang Guo,Hailong Hu,Fushan Li
Metals used in the electronics, machinery manufacturing, and construction industry are often chemically reactive and corrosion-prone, while barriers on a metal as a conventional method for anticorrosion always have negative effects including a toxic nature, thickness increase over time, and changes of electrical and optical properties after surface coating. This study employs a benzene solution to induce a rapid formation of a polycrystalline graphene film on copper foils or iron sheet substrates under atmospheric conditions by electromagnetic induction, which is non-toxic and environment-friendly and produces favorable anticorrosive effects. The microscopic analysis shows that the as-grown film is a polycrystalline graphene complex of graphene crystallites. It is revealed that the copper foils or iron sheets with the graphene film is significantly resistant to strong corrosion, with the corrosion current density is one order of magnitude lower when compared with samples without the graphene films. The polycrystalline structure of the graphene film can prevent the electronic conduction of the surface, thereby reducing corrosion and local over-corrosion phenomena when metals are situated in a long-term exposure to corrosive environments.
Jiong Ding,Liming Yu,Jichen Wang,Qiyue Xu,Suijun Yang,Shuliang Ye
The thermal inertia determination and correction are the significant steps in accelerating rate calorimetric based kinetics calculation and thermal hazard evaluation. However, the existing kinetics approaches based on the constant thermal inertia ignore the fact that the sample’s heat dissipation is varying during the pseudo-adiabatic reaction. To overcome this shortcoming, an amended thermal inertia expression is proposed and a symmetric dual-channel accelerating rate calorimeter is developed in this article. A novel kinetics approach is presented with the varying thermal inertia consideration based on the measured electrical power data. With the different mass percent DTBP/toluene solutions experiments, the validities and advantages of the proposed calorimetry and the corresponding thermal analysis method are verified. Meanwhile, the challenges in the engineering implementation of this proposed method are analyzed and discussed at the end of the article.
A calix[4]arene-based dimeric-cholesteryl derivative with naphthalene in the linkers (C2N2C) was designed and synthesized. The gelation behaviors of the compound in 36 liquids were evaluated. It was demonstrated that C2N2C could gel 16 of the liquids tested, which include both polar and apolar liquids. SEM and AFM studies revealed that the morphologies of the gel networks are dependent on the concentrations of C2N2C and the nature of the liquids under study. Importantly, rheological studies revealed that the gel of the compound in benzene possesses sensitive, fast and fully reversible thixotropic property. More importantly, the Tgel of the C2N2C/benzene gel could be at least more than 60 degrees higher than the boiling point of benzene when the gelator concentration is greater than 6% (w/v), a result never reported before. CD measurements revealed the chiral nature of the assemblies of the gel networks. Further investigation by AFM measurements confirmed the right-hand helical structures of the gel networks of C2N2C/benzene gel. As anticipated, hydrogen bonding and π–π stacking are the two main driving forces for the formation of the gels.
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