Mingchao Wang

Hierarchical Mesoporous NiO/MnO2@PANI Core–Shell Microspheres, Highly Efficient and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

We report on the new facile synthesis of mesoporous NiO/MnO2 in one step by modifying inverse micelle templated UCT (University of Connecticut) methods. The catalyst shows excellent electrocatalytic activity and stability for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline media after further coating with polyaniline (PANI). For electrochemical performance, the optimized catalyst exhibits a potential gap, ΔE, of 0.75 V to achieve a current of 10 mA cm-2 for the OER and -3 mA cm-2 for the ORR in 0.1 M KOH solution. Extensive characterization methods were applied to investigate the structure-property of the catalyst for correlations with activity (e.g., XRD, BET, SEM, HRTEM, FIB-TEM, XPS, TGA, and Raman). The high electrocatalytic activity of the catalyst closely relates to the good electrical conductivity of PANI, accessible mesoporous structure, high surface area, as well as the synergistic effect of the specific core-shell structure. This work opens a new avenue for the rational design of core-shell structure catalysts for energy conversion and storage applications.

Preparation and Properties of SiO2/Al2O3-SiO2 Fiber Mat Composite Materials

A light weight and heat-resistant composite material was successfully fabricated by impregnation-filtration process in which Al2O3-SiO2 fiber mat was used as the skeleton and silica was applied as reinforcing filler. The effects of both concentration of silica sol and sintering temperature on SiO2/Al2O3-SiO2 fiber composites were studied. The results indicated that the density of composites increased with the concentration of silica sol increasing. The heat-treatment temperature had little effect on the density of composites. As heat-treatment temperature increased, the compressive strength increased firstly and then decreased.

High Temperature Bonding Effect of the Room-Temperature-Curing Phosphate Adhesive for C/C Composites

A heat-resistant phosphate adhesive was developed for joining and repairing of C/C composites. The high-temperature bonding effect for both cured adhesive and 1300°C-calcined adhesive had been evaluated through testing high-temperature shear strength of corresponding joints. The results showed that the bonding strength of cured adhesive decreased from 7.9 MPa at RT to 0.9 MPa at 1300°C, while that of 1300°C-calcined adhesive could maintain about 4 MPa at temperature range from RT to 700°C and then decreased to 1.7 MPa at 1300°C. Besides, with the increasing thermal cycling times at 1300°C, the high-temperature bonding strength at this temperature could maintain at about 2.3 MPa.

Effect of Heat-Treatment on Microstructure and Mechanical Properties of Magnesium Phosphate Cement

Magnesium phosphate cement with M/P of 6, borax content of 4.8 wt% and water-to-cement ratio of 0.12, were made in this study. Heat-treatment was conducted from 200 °C to 1200 °C, and the physical and chemical evolution in the process of heating up was investigated via TG/DSC, XRD and SEM. Besides, the compressive strength, density and porosity of the heat-treated specimen were measured and the influence of treating temperature was discussed. The results show that magnesium phosphate cement possesses good chemical stability at 1200 °C and the strength has reduced only by 32.2% compared with none-treating specimens.

Tensile Strength and Bonding Mechanism of the Mullite Eramic/Ceramic Sample Joined by Phosphate Adhesive

The aluminum phosphate adhesive was prepared by aluminum dihydrogen phosphate and ceramic fillers. The mullite, silica and silicon powders were added as the fillers to improve the mechanical property and high temperature property. The specimens were prepared by joining the mullite ceramic/ceramic by phosphate adhesive. The strengths of the specimens treated at different temperatures were studied. The results indicated that the tensile strength at room temperature was 2.02 MPa, and it reached 5.06 MPa when the specimen was treated at 800°C. The bonding effect and bonding property at high temperature were discussed through the SEM analysis. Besides, the bonding mechanism was also explored.