Haibo Ouyang

Li4Ti5O12 hollow mesoporous microspheres assembled from nanoparticles for high rate lithium-ion battery anodes

Li4Ti5O12 hollow mesoporous microspheres (HMMs) assembled from nanoparticles were successfully synthesized by a facile hydrothermal method and subsequent calcination. They exhibit superior rate capabilities with reversible capacities of 176, 125 and 86 mA h g−1 after 10 cycles at 0.1 C, 20 C and 40 C (7000 mA g−1), respectively. The Li4Ti5O12 HMMs also possess outstanding cycle performance with only 3% capacity degradation at 10 C after 500 cycles, which is equivalent to a fade of merely 0.006% per cycle. The comparison with other studies shows that the Li4Ti5O12 HMMs possess more promising reversible capacity and rate capability among the values reported for Li4Ti5O12. These excellent electrochemical properties may be attributed to the unique HMM structures.

Effects of NBR Particle Size on Performance of Carbon Fiber–Reinforced Paper-Based Friction Material

In the present work, three different sized nitrile–butadiene rubber (NBR) particles were used to modify carbon fiber–reinforced paper-based friction material (CFRPF). The effects of NBR particle size on performance of CFRPF were studied. The microstructure and properties of the samples were investigated by scanning electron microscopy, thermal analysis, and wet friction performance testing. Experimental results indicated that there were four stages in the thermal degradation of NBR-modified CFRPF. NBR particle size had a great effect on the first degradation stage (100–300°C). The highest friction coefficient was obtained with the sample containing the finest NBR particles. The wear rate of the friction materials decreased with an increase in NBR particle size. However, NBR particle size had little influence on the wear rate of the couple plate. The sample containing coarse NBR particles showed excellent friction stability under oil-lubricated conditions.

Effect of hydrothermal modified carbon fiber through Diels–Alder reaction and its reinforced phenolic composites

In this work, carbon fibers were chemically modified with maleic anhydride through the Diels–Alder reaction under hydrothermal conditions, and then the modified carbon fiber reinforced phenolic resin composites were prepared by liquid impregnation processing. The structural and surface characteristics of carbon fibers were investigated by the Fourier transform infrared (FTIR) spectrum, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The tensile strength of the composites was measured by a universal material testing machine. The friction and wear behaviors of the composites were evaluated by a friction tester. Experimental results revealed that the carboxyl group was successfully grafted on the carbon fiber surface leading to the increase of surface activity without damaging the skin region and core region of the carbon fibers. The tensile strength of modified carbon fibers reinforced composites increased significantly by about 200%, while the wear volume decreased by about 50% compared with unmodified carbon fiber reinforced composites, resulting from good adhesion between the carbon fibers and resin matrix.

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B2O3·H2O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn4B2O7·H2O (4ZnO·B2O3·H2O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B2O3·H2O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B2O3·H2O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm−2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm−2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm−2 after 10 h for direct comparison with the coated samples.

Cf/C–SiC–MoSi2 composites with good ablation performance prepared via a two-step hydrothermal method

Cf/C–SiC–MoSi2 composites were prepared via a simple hydrothermal method. The kinetics of the hydrothermal penetration process, the mechanical properties, and ablation behaviors of the composites were investigated. Results showed that the penetration activation energy was only 51.3 kJ mol−1. The flexural strength of the composites was 111.7 MPa. The Cf/C–SiC–MoSi2 composites exhibited good ablation properties after being exposed to plasma flame at 2300 °C. During the ablation, molten SiO2 could prevent carbon from oxidation. Moreover, the transformation from MoO2 to gaseous MoO3 consumed considerable amounts of oxygen and absorbed a large amount of heat, which prevented the composites from further ablation.

Antioxidant modification of C/C composites by in situ hydrothermally synthesized 4ZnO·B2O3·H2O

Abstract Antioxidant modification of carbon/carbon (C/C) composites by in situ hydrothermally synthesized 4ZnO·B2O3·H2O was successfully achieved. Samples were characterized by X-ray diffraction, scanning electron microscopy, isothermal oxidation test and thermogravimetry/differential scanning calorimetry. The influence of hydrothermal temperature on the phase composition and microstructure of as-prepared 4ZnO·B2O3·H2O, and the antioxidant modification of C/C composites were investigated. Results showed that 4ZnO·B2O3·H2O crystallite coating was achieved on the surface of C/C composites at the hydrothermal temperature range of 100–180°C. A smooth and crack-free 4ZnO·B2O3·H2O layer was obtained when the hydrothermal temperature reached 140°C. The isothermal oxidation test showed that the oxidation resistance of C/C composites was improved. The as-modified composites exhibited a weight loss of only 1.93 g/cm3 after oxidation at 600°C for 15 h, while the non-modified one had a weight loss of 5.20 g/cm3 after only 10 h of oxidation.