Hongyun Jin

Three dimensional architecture of carbon wrapped multilayer Na3V2O2(PO4)2F nanocubes embedded in graphene for improved sodium ion batteries

A novel Na3V2O2(PO4)2F@carbon/graphene three dimensional (3D)architecture (NVPF@C/G) is developed through a simple approach for the first time. It exhibits greatly improved rate capability and delivers a reversible capacity of 113.2 mA h g−1 at 1C.

The Effect of Spherical Silica Powder on the Tribological Behavior of Phenolic Resin–Based Friction Materials

The friction and wear behavior of friction materials filled with irregular silica, spherical silica and surface-treated spherical silica particles is discussed in this paper. Compared to irregular silica, spherical silica powders improve the wear resistance, but decrease the friction coefficient. Surface-treated spherical silica powder is more effective in the improvement in the wear resistance, but with the similar friction coefficient of irregular silica-filled materials. This makes it possible to be used as friction-improving fillers in brake materials. Mechanisms for the improvement are also discussed in this paper.

Al2O3–Fe3O4–expanded graphite nano-sandwich structure for fluoride removal from aqueous solution

In this study, a novel Al2O3–Fe3O4–expanded graphite nano-sandwich adsorbent was prepared to remove fluoride from aqueous solutions. Field emission scanning electron microscope examination was carried out to characterize its microstructure. Fe3O4 cubes, with the size of 60–80 nm, and pea-shaped Al2O3 particles, with the length of 20–50 nm, were observed on the surface of the expanded graphite. Fourier transform infrared spectra results indicated that new functional groups had occurred on the sandwich surface following the adsorption process. Identified X-ray powder diffraction curves determined that Al2O3 was amorphous, while Fe3O4 and expanded graphite were crystalline. Vibrating sample magnetometer experiments revealed that the saturation magnetization of the nano-sandwich was 3.7 emu g−1, which was strong enough to separate the sorbents from the solution. The adsorption kinetics followed the pseudo-second-order rate equation with intra-particle diffusion as the rate determining step. The adsorption pattern of the nano-sandwich followed the Langmuir isotherm better than the Freundlich isotherm and the adsorption capacity increased by rising temperature. Under optimized conditions, fluoride removal efficiency reached 96.8%. After two cycles of regeneration with 0.1 mol L−1 NaOH, fluoride removal efficiency could still reach 91.4% and the residual fluoride concentration was lower than 1.5 mg L−1. The sorbents demonstrated great potential in fluoride removal, in terms of higher adsorption efficiency, wider pH adsorption range, good regeneration as well as convenient solid–liquid separation characteristics.

Simulation of Temperature Distribution in Disk Brake Considering a Real Brake Pad Wear

AbstractThis paper presents a methodology for the modeling of the transient thermal behavior of the disk brake of the vehicles using finite element methods. The influence of the wear properties of friction materials on thermoelastic behaviors is investigated to facilitate the conceptual design of the model. The coupled characteristics of the friction heat flow between the disk and pad as well as the effects of the brake disk thermal stress because of the variable applied pressure was considered. At the same time, the model was optimized by the experiment. Repeated brake processes with varying load, sliding speeds and temperature are applied in the simulation of the disk brakes. Experimental dependencies of the coefficient of friction and wear rate on the temperature of brake pad were approximated and applied to the model. The temperature and pressure on the contact surface of the pad/disk brake system obtained for constant and speed/pressure sensitivity applications were confronted and compared. The thermo-distribution is operated to visualize the disk temperature.

Nanoporous carbon leading to the high performance of a Na3V2O2(PO4)2F@carbon/graphene cathode in a sodium ion battery

The Na3V2O2(PO4)2F/graphene sandwich cathode has attracted great attention as a potential candidate for sodium-ion batteries in view of its high capacity and good cycling ability. However, a big issue for Na3V2O2(PO4)2F/graphene is its extremely poor electronic conductivity due to the multilayer structure in which Na3V2O2(PO4)2F particles are located between the graphene layers. We introduced carbon in the Na3V2O2(PO4)2F/graphene sandwich to form a 3D architecture – Na3V2O2(PO4)2F@carbon/graphene (NVPF@C/G). A battery with the NVPF@C/G cathode presents good electrochemical properties, a high capacity, 135.8 mAh g−1 at 0.1C, with a capacity retention of 96.8% at 2C for fifty cycles. NVPF@C/G showed obvious advantage in the rate performance and cycle stability compared with the NVPF/G sandwich, which indicated that the nanoporous carbon integrated in the 3D structure plays a crucial role in improving the electrochemical performance. It is anticipated that such a new method of introducing nanoporous carbon for battery performance enhancement can be extended to other graphene-based sandwich structure electrodes.

Research on Synthesis of β-Ni(OH)2 Nanorods and Removing Congo Red from Polluted Water

For the first time, rod-like β-Ni(OH)2 was synthesized through the composite-hydroxide-mediated (CHM) method with NiCl2·6H2O as raw material and PEG20000 as modifier. Fourier transform infrared (FT-IR) spectra revealed the presence of new functional groups on the surface of the β-Ni(OH)2 after modified, which means better adsorption efficiency. In adsorption experiments with Congo Red (CR), the adsorption capacity for modified β-Ni(OH)2 was 149.25 mg g−1, which was a better adsorption capacity compared with some previously reported Ni(OH)2.