Abstract: Combined of refractory metal W and ultra-high temperature ceramic ZrC, W/ZrC ultra-high temperature cermets have exhibited high temperature strength, excellent resistance to thermal shock and ablation, possessing a wide application prospect in high temperature fields. At present, W/ZrC cermets are mainly fabricated by Hot Pressing (HP), Spark Plasma Sintering (SPS), in Situ Reactive Sintering (SRS) and Displacive Compensation of Porosity (DCP). Characters and developments of all these fabrications are reviewed in this paper, and a comparison of advantages and shortages between them is made, also the properties of W/ZrC cermets are analyzed. At last, the development directions of future work are prospected.
Abstract: This paper presents an investigation of the exchange bias of the Fe/Fe3O4 layer deposited on the Ag/hollow glass microspheres. The results show that exchange bias is affected by different thickness of Fe3O4 layer which is caused by different reaction time. The exchange bias field (HE) increases gradually with increasing reaction time, and achieves maximum value when the reaction time reaches 30min; after that, it decreases. It is also found that the changes of exchange bias field (HE) are proposed to the frozen interfacial spins and the structural lattice disorder
Abstract: F doping BiFeO3-xFx (x=0, 0.02, 0.04, 0.06, 0.08) thin films were successfully fabricated on ITO/glass substrates by sol-gel method. X-ray diffraction analysis indicated that the un-doped BiFeO3 and F doping BiFeO3 thin films presented rhombohedral structure with the space group R3c. F-doping is found to significantly enhance the dielectric constant and decrease the leakage current density for x=0.08 compared with x=0. This study provides direct evidence that the multiferroic characteristics of BiFeO3 are sensitive to the anion doping, such as F, providing a convenient alternative to manipulate the electric polarization in multiferroic oxides.
Abstract: During the machining, the places of tool and work piece may change as influenced by various factors, consequently, the machined parts can not meet the needs of actual use. Therefore, before machining, various influencing factors on machining accuracy should be taken into consideration. This paper analyzed the influencing factors on machining accuracy and proposed measures to reduce machining errors and provide a guarantee for improving the machining accuracy.
Abstract: Insulating BiFeO3 ceramics with a small amount of secondary phase Bi2Fe4O9 were prepared by rapid sintering at 840 °C using sol-gel derived fine powders. The ceramics are dense and consist of grains of 3∼8 μm in size. Their leakage current density remains lower than 5.5×10−5 A/cm2 under the applied electrical field below 100 kV/cm. The main conduction mechanism from 50−190 kV/cm is space-charge-limited-current relating to oxygen vacancies. The ceramics exhibit a saturated ferroelectric hysteresis loop with a remanent polarization (2Pr = 22 μC/cm2) under the applied field of 165 kV/cm. Weak ferromagnetism was observed with a remanent magnetization 2Mr of 1.2×10−4 μB/Fe at 300 K and of 1.8×10−4 μB/Fe at 10 K.
Abstract: The effects of co-solvent to the solubility of ginger bioactive compounds, 6-gingerol, 6-shogaol, 8-gingerol and 10-gingerol in hot water were calculated using the conductor-like screening model for real solvent (COSMO-RS). In this work, ethanol was used as the co-solvent. The σ-profiles of the molecules were calculated using Gaussian software and the solubility were calculated using the COSMO-RS method. The solubility of these ginger bioactive compounds were calculated at 50 to 150°C.The amounts of ethanol used were 0 mol (binary system), 0.005, 0.010 and 0.015 mol. The results show that when the concentration (mole fraction of ethanol) of co-solvent increases, the solubility of ginger bioactive compounds increase. While the temperature increases, the concentration (mole fraction of ethanol) of co-solvent decreases.
Abstract: In order to realize the mechanized transplanting of rice pot seedling and ensure our food security, The pitch curve of non-circular gear is fitted based on cubic, non-uniform and rational B-spline curve. The planetary gear train transplanting mechanism has been invented for ride type, and kinematics mathematical model has been built through the kinematics analysis of transplanting mechanism. The computer aided analytical and optimized software has been developed by using software platform of Matlab. Through tuning the data points by man-machine interaction, pitch curve of non-circular gear is optimized and structural parameters are obtained, which can meet the demand of track and attitude in the transplanting process for rice pot seedling. In condition of the parameters, the correctness of the established model is verified by the virtual experiment by software of Adams.
Abstract: The tightness of bolted flange joints will weaken due to the loss of bolt load as a result of creep under high temperature. There exists no mature calculation procedure that can accounts for creep. Based on the finite element simulation of a combined flanged joint under four various conditions, the strength integrity and sealing performance of it are evaluated according to the code JB4732-2005. The results show that the integrity and tightness of the combined flanged joint under pre-loading condition, pressure condition and operating condition (except local film stress) meet requirements. However, more than 50% of the bolt load relaxation is found due to creep, part of the gasket residual stress is lower than the required minimum sealing pressure. It can lead to leakage. Bigger bolt pre-tightening force, materials with good creep relaxation resistance and hot-tighting method are recommended to reduce the influence of creep.
Abstract: The main objective of this study is to analyze the influence of joint interface on mechanical behavior of two cylinders by modeling different geometry with Finite Element Method (FEM). The structures are continuum model (CM), joint interface model with different materials (JIM1) and joint interface model with same materials (JIM2). The displacement-load relationship, equivalent plastic strain (EPS), deformation and contact pressure based on three models are gained. FEM results indicate that under the same load, the displacements of three models are various in loading and unloading processes. The EPSCM is relative stable originally and then decerase quickly while the EPSJIM1 and EPSJIM2 grow rapidly and fall slowly later.The deformation of CM, JIM1 and JIM2 under 300Mpa are 62.5μm, 33μm and 68.13μm respectively. The contact pressure of JIM1 is smaller than JIM2. The effects of frictional coefficients (vary from 0 to 1.0) on deformation and contact pressure are also investigated. Results show that joint interface make the structure’s behaviors different compared with continuum structure and this study can provide reference for the design of structures with joint interface in machinery.
Abstract: The microstructures and mechanical properties of a high carbon DP steel and a low carbon Nb microalloying DP steel were investigated. The two types of DP steels have both qualified to meet European standard performance. But the high carbon content DP steel exhibits relatively low elongation and low hole expansion rate as well as poor bending performance. The martensite island in high carbon DP steel appears obvious band structure, and the size of martensite islands is big. Contrary, the matensite islands in low carbon and Nb microalloying DP steel are dispersed and fine, which lead to perfect comprehensive performance.