Mingzhang Lan

Characteristics of Self-Healing Microcapsules for Cementitious Composites

Urea formaldehyde/epoxy resin microcapsules were prepared by an in situ polymerization method and the effect of emulsifier on the syntheses process of the microcapsules was discussed. The surface morphology of the microcapsules was observed by optical microscopy and scanning electron microscopy (SEM). Chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR). Thermal stability was obtained using simultaneous thermal analysis (STA). The microcapsules were composed of urea-formaldehyde resin shell and epoxy resin core. Emulsifier played an important role in the polymerization process when the core material was packed by pre-polymer, so the effects of different emulsifiers (OP-10, SDS and SDBS) were discussed respectively. Results showed that the particle size of the microcapsules was uniform when SDBS as an emulsifier. Microcapsules showed good thermal stability below 240 °C and the initial decomposition temperature of the microcapsules was 265 °C. The core materials released after microcapsules rupturing, which could be proven by the images of SEM. When implanted in cementitious composites, complete shape of microcapsules and good interface between microcapsules and cement specimen substrate could also be observed.

Effect of Conductivity and Radiation on Heat Dissipation Performance of Coating

Aiming at the problem of heat dissipation of electronic devices in low temperature environment, the effect of thermal conductivity and emissivity of coating on its heat dissipation performance was studied by theoretical calculations and experiments in this study. The results show that the heat dissipation performance of organic coating with emissivity of 0.7–0.95 is improved as its thermal conductivity increasing. And temperature difference between inside and surface of object is inversely proportional to thermal conductivity. That is, when thermal conductivity exceeds a certain value, it will no longer affect heat dissipation performance of coating. In addition, emissivity of coating directly affects its cooling performance, and the proper matching interaction between thermal conductivity and emissivity of coating can enhance heat dissipation effects. In the case of non-forced convection cooling, the thermal conductivity of the organic coating is preferably 2–10 W/m·K.

Influence of characteristics of alumina-silicate raw materials on the formation process of clinker

The traditional alumina-silicate raw materials, for example, clays, in the precalcining technique of cement production, have been replaced by low grade and high silica content sandstones, shales, and industrial waste residues, including fly ashes, slag, and others. The results are the change of compositions and characteristics of raw materials applied and a great effect on cement calcination process and clinker formation. In this work, the cement clinker formation process of different alumina-silicate raw materials to replace clay raw material was studied by chemical analysis, X-ray diffraction, differential thermal analysis, and high temperature microscope based on the characteristics of the alumina-silicate raw materials. The formation heat of the clinker was determined by the acid dissolution method. Influence of different alumina-silicate raw materials on the clinker burnability and formation process was studied. The results show that the changing of alumina-silicate raw materials, especially using industrial waste residues, can reduce the formation temperature of high temperature liquid phases, improve the burnability of raw materials, reduce the formation temperature and formation heat of clinker. And this study also observed the formation temperature and transformation of high temperature liquid phases in the heating process of raw materials by high temperature microscope.