Time filter

Source Type

Li J.,Harbin Institute of Technology | Zhouyang H.,China Electronic Product Reliability and Environmental Testing Research Institute | Lou Y.,Harbin Institute of Technology
International Journal of Advanced Manufacturing Technology

Generally, tool path is generated in a computer-aided manufacturing software considering only the geometry of machining parts. It is converted into numerical control (NC) codes in the postprocessor based on the particular machine kinematics. For some special types of five-axis machine tools, e.g., non-orthogonal five-axis machine tools, the generated NC codes may produce unqualified parts because of the existence of the non-linear error. Conventional commercialized postprocessors usually do not have the function of non-linear error checking. Observing that the tool path is a non-smooth trajectory full of corners and a series of connected line segments, cubic spline interpolation is applied to smooth the tool path at regular points in this study. The cutter tip center points are computed by the cubic spine interpolation, while the cutter posture vectors are obtained via linear interpolation. At the splines (for regular points) and the line segments (feature points), more points are chosen to be converted into NC codes to reduce the non-linear error, which is called data densification. Using the cubic spline to smooth the tool path and the data densification to reduce the non-linear error, a novel tool path optimization algorithm in postprocessor is proposed. Experiments were carried out on an inclined rotary spindle axis non-orthogonal five-axis machine tool. It shows that the proposed tool path optimization provides improved accuracy and surface quality. © 2013 Springer-Verlag London. Source

Lu H.-F.,China Electronic Product Reliability and Environmental Testing Research Institute | Yan W.-P.,Dalian University of Technology | Liu Z.-H.,Dalian University of Technology | Li J.-C.,Dalian University of Technology
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis

The UV/ozone surface treatment was a simple and low cost hydrophilic modification method. In this paper, UV/ozone treatment is utilized to hydrophilize the surface of PDMS and the results are compared. Contact angle is applied to estimate the effect and stability of the modified surfaces. The results show that the contact angle is around 60° on the PDMS surface with UV/ozone treatment after 12 hours, and it can maintain the surface hydrophilicity in two weeks under ambient atmosphere. The results of FTIR spectroscopy indicate that many chemical functional groups of PDMS surface have been changed with UV/ozone modification, -CH3 hydrophobic group gradually decrease over time, -OH and Si-OH hydrophilic groups increase obviously, and the characteristic peaks of SiO2 gradually appear. Through SEM/EDS analysis, it has been found that the major constituent of the surface of PDMS is SiO2 after the surface modification. These results demonstrate that the more hydrophilic groups and the glass-like SiOx layer are formed on the PDMS surface modified with UV/ozone, which enhance the surface hydrophilic and minimize the hydrophobic recovery. © 2016, Peking University Press. All right reserved. Source

Zhou J.,General Research Institute for Non Ferrous Metals and Grirem Advanced Materials Co. | Shen H.,Jilin University | Feng G.,China Electronic Product Reliability and Environmental Testing Research Institute | Xu D.,Jilin University
Modern Physics Letters B

Fe-doped In2O3 nanotubes were successfully synthesized by electrospinning technique followed by subsequent heat treatment. The as-prepared samples appeared as an apparently open-end one-dimensional (1D) and tubular-like morphology with the diameter of approximately 150 nm and the wall thickness about 20 nm. The diffraction peak of the obtained nanotubes shifts toward bigger angle direction with the increase of the Fe content. Comparing to the In2O3 nanotubes, the Fe-doped In2O3 nanotubes exhibit better sensing characteristics toward ethanol gases, including higher sensing response, lower operating temperature and higher selectivity. Enhanced sensing properties are attributed to 1D hollow nanostructures and the role of doping Fe element. © 2016 World Scientific Publishing Company. Source

Hu C.,China Electronic Product Reliability and Environmental Testing Research Institute | Zhou L.,Guangzhou City Polytechnic
Proceedings of the Electronic Packaging Technology Conference, EPTC

As an important packaging material, much work has been done in an attempt to improve DGEBA epoxy resins to be used in electric industry. In order to improve heat resistance, the cross-linking density of epoxy resins has been attempted to increase, or rigid groups have been introduced to copolymerize with epoxy resin. However, these methods have been confirmed that they will induce friability. In addition, as Si-O-Si bonding is more flexible than C-C bonding, siloxane oligomer is introduced to the matrix to improve toughness of epoxy resins, but the glass transition temperature (Tg) becomes lower by reason of low compatibility between epoxy resin and siloxane. Moreover, the pure epoxy resins are flammable. It is worth notice that halogen-containing resins are considered to limit the use by reason that they will release toxic gases while heating. Phosphorus-containing epoxy resins could substitute for halogen-containing resins for the use of flam-retardant. The introductions of phosphoric ethers, DOPO or its derivatives to the matrix have been reported. Such methods are confirmed to improve flam-retardant with epoxy, but The decreasing of heat resistance and toughness can't be ignored when too much phosphorus is in the resins. From the above, it is known that present achievements can improve the property of epoxy resins at one side, but they can not improve or at least keep the other properties. In this study, a kind of novel silicon, phosphorus-containing hybrid material was prepared and it could be used as the modifier of DGEBA epoxy resins. The thermal stability, toughness and flam-retardant of the modified resins were all improved. For one thing, the hybrid material was mainly composed of polysiloxane, and the Si-O-Si chains in the matrix would improve toughness for the resins. For another, the hybrid material contained a lot of hydroxyl groups in the structure. The compatibility with epoxy resins and the modifier is good. The Si-OH groups in the hybrid material could react with the hydroxyl groups in DGEBA when the resins were cured. The heat resistance was improved on account of higher cross-linking density of the resins. What's more, phosphorus-containing groups were introduced in the hybrid material. P and Si could both act to exhibit the considerable synergistic effect on flam-retardant even though the weight of P was low. In this paper, the thermal, mechanical and flammable properties of the cured samples were investigated in detail by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), as well as tensile, impact and limited oxygen index (LOI) testing. The result showed that the hybrid modified epoxy resins exhibited good thermal stability, toughness and flam-retardant property. With the ratio m(DGEBA): m(SPCH)=100: 25, Tg of the modified sample was 49.35 °C higher than that of the pure sample, and LOI was raised from 21.5 to 29.8. The char yield of E-25 at 800°C reached to 37.8 %, which compared to 12.9 % of the pure sample. But the toughness of E-25 was not so prominent if compared with E-15. The impact stress of sample E-15 reached to 24.1 kJ·m-2. For all modified samples, the tensile strengths were all basically maintained. SEM micrographs of the fracture surfaces indicated that these modified resins were homogeneous and tough. In the practical application, the different ratios of the modifier in epoxy resin were chosen with actual demand. © 2014 IEEE. Source

Cheng L.X.,South China University of Technology | Li G.Y.,South China University of Technology | Wang X.Q.,China Electronic Product Reliability and Environmental Testing Research Institute | Li Z.L.,South China University of Technology | Wu Z.Z.,South China University of Technology
Materials Letters

To reveal the effects of Titanium on active bonding between Sn3.5Ag4Ti(Ce,Ga) alloy filler and Silicon, the characteristics of the as-bonded Si/Si substrates and bonded Si/Si substrates aged at 190 °C for 720 h were investigated. The active element Ti is found to be segregated at the interface of Sn3.5Ag4Ti(Ce, Ga)/Si joint, and the TiSi and TiSi2 phases are identified to be formed discontinuously along the interface. Experiment results reveal that active element Ti plays an important role for obtaining reliable bonding at low temperature, and shear strength of the Si/Si joints meets the requirements of die or wafer bonding application. © 2015 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations