Papers by Author: Chun Wei

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Authors: Ming Zeng, Chun Wei, Xue Mei Xiong, Chuan Bai Yu
Abstract: Asbestos-free frictional material is developed by using phenol formaldehyde resins modified with nano- SiO2 as matrix while surface-treated sisal fiber and glass fiber are used as reinforcement. The friction and wear properties were investigated on Constant speed (D-SM) tester. The abrasion surfaces of composites were observed by scanning electron microscope (SEM). Test result shows that all the properties, such as, friction coefficient and wear can meet the GB5763-2008 requirement. When the sisal fiber and glass fiber hybrid ratio is 2:1, the composite has the high mechanical property, suitable and stable coefficient of friction and relatively low wearability especially at high temperature.
Authors: Chuan Bai Yu, Chun Wei
Abstract: Reinforced phenol formaldehyde resin (PF) matrix nanocomposites with different nano-SiO2 were fabricated with two-roll compounding and compression molding technology. The mechanical and tribological behaviors of the reinforced composites were studied. The friction and wear experiments were tested on a constant speed machine (D-SM). The impact and flexural strength of nanocomposites were increased by the addition of various types of SiO2, but the flexural modulus was decreased. The effects of the addition of various types of SiO2 on tribological properties of the composites were explored in this study. The results showed that the coefficient of friction of the composites increased, while the wear rate values decreased at various temperatures. Microstructure of worn surface of the tested composites was observed by scanning electronic microscope (SEM) and the wear mechanism of the reinforced composites was studied.
Authors: Kun Peng Jiang, Li Jiang, Lei Liao, Wei Ping Yu, Ai Miao Qin, Chun Wei
Abstract: This paper describes a one-step hydrothermal synthesis of rod-shaped HgTe nanocrystals (NCs). X-ray powder diffraction (XRD), field scanning electron microscopy (FE-SEM), transition electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX) have been used to characterize the HgTe NCs. The length, diameter, surface roughness and the aspect ratio of the HgTe nanorods are well controlled through Te precursor, reaction time and reductant.
Authors: Wei Zhong Lu, Chun Wei, Qui Shan Gao
Abstract: Polymethylene bis(p-hydroxybenzoates) were prepared from methyl p-hydroxybenzoate and different diols by melted transesterification reaction. Three liquid crystalline polyesters were synthesized from terephthaloyl dichloride and polymethylene bis(p-hydroxybenzoates). Its structure, morphology and properties were characterized by Ubbelohde viscometer, Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), polarized optical microscopy (POM) with a hot stage, and wide-angle X-ray diffraction (WAXD). Results indicated that the intrinsic viscosities were between 0.088 and 0.210 dL/g. Optical microscopy showed that the TLCP has a highly threaded liquid crystalline texture and a high birefringent schlieren texture character of nematic phase and has wider mesophase temperature ranges for all polyesters. DSC analysis were found that the melting point (Tm), isotropic temperature (Ti) of TLCPs decreased and the temperature range of the liquid crystalline phase became wider with increased number of methylene spacers in the polyester. The WAXD results showed that TLCPs owned two strong diffraction peaks at 2θ near 19° and 23°.
Authors: Chuan Bai Yu, Chun Wei, Dong Ming Pan
Abstract: The objective of this research was to investigate thermal stability and dynamic mechanical behavior of nano-SiO2/phenol formaldehyde resin (PF) nanocomposites with various nano-SiO2 at 2 wt% loading content. The nano-SiO2/PF nanocomposites were fabricated by two-roll compounding and compression molding technology. The storage modulus (E′) at the starting point of 50 was increased by adding various nano-SiO2 into PF matrix. The E′ of the nanocomposite with only 2 wt% of SiO2 synthesized under ultrasonic irradiation (U-SiO2) was 2 times higher than that of the control PF. Thermal expansion and the coefficient of thermal expansion of nano-SiO2 loaded nanocomposites were lower than that of the control PF in the range of 100–200 and 200–250 . Thermogravimetric analysis demonstrated that the thermal stability of nanocomposites was evidently enhanced. In comparison, U-SiO2 reinforced nanocomposites showed higher thermal properties than those reinforced by mesoporous silica (SBA-15) and SiO2 synthesized by stirring (S-SiO2).
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