Preparation and Properties of the Composite Enhancement Layer of Bearing Ring

In this paper, the NU308 bearing rings were subjected to strengthen grinding treatment (SGT) at ambient temperature. And the running reliabilities of specimens that subjected to SGT and conventional treatment (CT) were respectively investigated by testing dynamic properties including the running temperature, vibrations, and surface burning. Moreover, the residual stress, microtopography, and microstructures on the cross-section were respectively tested with residual stress analyzer and field-emission scanning electron microscopy. The results showed that the running reliabilities of the specimen after SGT had been significantly improved with the reduction of running temperature, vibration, and surface burning. Further study showed that the specimen’s surface was filled with disordered micropores after SGT compared to the regular strip texture on the CT specimen’s surface, and the maximum residual compressive stress induced by SGT was about −900 MPa. Moreover, the thickness of the residual compressive stress layer was over 180 µm, while the thickness of severe plastic deformation layer was about 50 µm.

TiO2-Loaded WO3 Composite Films for Enhancement of Photocurrent Density

Titanium dioxide （TiO2） loaded tungsten trioxide （WO3） composite films are prepared by an E-beam vapor system. Associated with the existence of a heterojunction at the interface of TiO2 and WO3, the prepared TiO2-WO3 composite film shows enhanced photocurrent density, four times than the pure WO3 film illuminated under xenon lamp, and higher incident-photon-to-current conversion e^ciency. By varying the initial TiO2 film thickness, such composite structures could be optimized to obtain the highest photocurrent density. We believe that thin TiO2 films improve the light response and increase the surface roughness of WO3 films. Furthermore, the existence of the heterojunction results in the e^cient charge carriers＇ separation, transfer process, and a lower recombination of electron-hole pairs, which is beneficial for the enhancement of photocurrent density.

Torsional postbuckling characteristics of functionally graded graphene enhanced laminated truncated conical shell with temperature dependent material properties

Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented in this study.In the thickness direction,the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded(FG)distribution,with each layer containing a variable volume fraction for graphene reinforcement.To calculate the properties of temperaturedependent material of GEC layers,the extended Halpin-Tsai micromechanical framework is used.The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous,laminated cylindrical,and conical shells,the FEM model is validated.The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength.Also,the geometric parameters have a critical impact on the stability of the conical shell.However,a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell’s postbuckling strength.

Preparation of ZnO/GO composite material with highly photocatalytic performance via an improved two-step method

ZnO/graphene oxide（ZnO/GO） composite material,in which ZnO nanoparticles were densely coated on the GO nanosheets,was successfully prepared by an improved two-step method and characterized by IR, XRD,TEM,and UV-vis techniques.The improved photocatalytic property of the ZnO/GO composite material,evaluated by the photocatalytic degradation of methyl orange（MO） under UV irradiation,is ascribed to the intimate contact between ZnO and GO,the enhanced adsorption of MO,the quick electron transfer from excited ZnO particles to GO sheets and the activation of MO molecules viaπ-πinteraction between MO and GO.

Enhanced wetting and properties of carbon/carbon-Cu composites with Cr_3C_2 coatings by Cr-solution immersion method

A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140°to 60°, demonstrating the significant improvement in the wettability. The Cr3C2- coated C/C-Cu composite with only 4.2% porosity and 3.69 gcm^-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.

Enhancement of Mechanical Properties of Natural Rubber with Maleic Anhydride Grafted Liquid Polybutadiene Functionalized Graphene Oxide

An effective procedure has been developed to synthesize the functionalized graphene oxide grafted by maleic anhydride grafted liquid polybutadiene（MLPB-GO）. Fourier transform spectroscopy and X-ray photoelectron spectroscopy indicate the successful functionalization of GO. The NR/MLPB-GO composites were then prepared by the co-coagulation process. The results show that the mechanical properties of NR/MLPB-GO composites are obviously superior to those of NR/GO composites and neat NR. Compared with neat NR, the tensile strength, modulus at 300% strain and tear strength of NR composite containing 2.12 phr MLPB-GO are significantly increased by 40.5%, 109.1% and 85.0%, respectively. Dynamic mechanical analysis results show that 84% increase in storage modulus and 2.9 K enhancement in the glass transition temperature of the composite have been achieved with the incorporation of 2.12 phr MLPB-GO into NR. The good dispersion of GO and the strong interface interaction in the composites are responsible for the unprecedented reinforcing efficiency of MLPB-GO towards NR.

Stretch-shear mode laminated metglas/Pb(Zr,Ti)O3/metglas composite with an enhanced magnetoelectric effect

Magnetoelectric(ME)composites have recently attracted an ever-increasing interest and provoked a great number of research activities,driven by the potential applications in novel multifunctional devices,such as sensors and transducers[1].Direct ME effect,which describe the appearance of an electric polarization P upon applying a magnetic field H,is usually evaluated by the

Effects of Rectangular Wing Vortex Generators on the Thermal-Hydraulic Performance of Louvered Fin and Flat Tube Heat Exchanger

In this paper,a novel composite heat transfer enhancement technique comprised of louvered fins(LFs)and rectangular wing vortex generators(RWVGs)is proposed to improve the LF side thermal-hydraulic performance of louvered fin and flat tube heat exchangers(LFHEs).After validation of the LF side pressure dropΔP and heat transfer coefficient hLFof the baseline by experiments,the numerical method is applied to investigate the influential mechanisms of the RWVG parameters(the number N(7 to 15),attack angleβ(30°to 90°),height H_(VG)(0.8 mm to 2 mm)and width W_(VG)(0.8 mm to 1.2 mm))on the performance of the LFHE in the velocity range of 3 m/s to 10 m/s.Results show that thermal-hydraulic performance of the LFHE is significantly impacted by the RWVGs,and according to the performance evaluation criteria(PEC),the LFHE achieves its optimal thermal-hydraulic performance when N=7,β=45°,H_(VG)=1.8 mm and W_(VG)=1 mm.Compared to the baseline,the maximum,minimum and average increments of PEC for the optimal case are 13.85%,4.67%and 8.39%,respectively.