Advanced Materials Research Vol. 815

Abstract: Linear and branched poly (ethylene terephthalate) were prepared by using terephthalic acid, ethylene glycol as main raw materials and pentaerythritol as polyfunctional monomer through melt polycondensation method. The samples were characterized with respect to intrinsic viscosity and differential scanning calorimeter (DSC). The results show that the low branched poly (ethylene terephthalate) could be obtained by the addition of tertrafunctional pentaerythritol through common melt polycondensation process.

Abstract: Single sided resistance spot welding (SSRSW) developed from RSW is a feasible plan to join vehicle structure to closed-form tube and is increasingly used in automobile manufacturing. During the process of SSSW, large deformation and complex contact status of the workpieces occur because there is no inside support. The complex contact status has directly influence on the size of the nugget which is critical to the quality of welding. In this study, the contact statuses during the current stage of sheet-to-tube spot welding were researched by numerical method. It was found that the widths of the contact regions of electrode to sheet and sheet and sheet to tube have dynamic change during welding process which decided the size and speed of the nugget formation. The results have direct guiding significance to the study on ring nugget formation during sheet-to-tube welding.

Abstract: To study the structure-property relationships of new chiral liquid crystalline materials based on menthol and explore their potential applications, a monomer 4-(4-allyloxybenzoyloxy) phenyl-4-menthyl-oxyacetyloxybiphenyl-4-carboxylate (LCM) and the corresponding homopolymer (LCP) were synthesized. The chemical structure was characterized by FT-IR and ¹H NMR. The liquid crystalline properties were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction. The monomer LCM formed a cholesteric phase when a flexible linkage chain was inserted between the mesogenic core and the terminal menthyl groups by reducing the steric effect. The homopolymer LCP exhibited a batonnet texture of a smectic A phase.

Abstract: In this paper, we studied the methods to synthesize good ZnO materials that can be applied in real environment. First we used spin coating method to form a layer of sol-gel driven ZnO, and then a hydrothermal method was used to synthesize nanowires of ZnO on the already obtained ZnO films. Some methods of test, including AFM and SEM, were performed to analyze the different characteristics of the material. Finally, their applications in the fields of TFT and solar cell were studied. We find that the ZnO films and nanowires are good in quality and their applications in TFT and solar cell are satisfactory.

Abstract: To characterize the degradation of material at low triaxiality, the shear modified GTN damage model proposed by Nahshon and Hutchinson (2008) was introduced in this study. The details of the numericalimplementation and validation of the model was conducted. And the shear modified parameter was determined by the comparisons of experimental and simulation results of the shear test. Then, the damage model was employed to simulate the cold rolling process, and the results showed that the shear modified GTN model can reveal the damage behavior and predict edge crackingof ductile materials in cold rolling.

Abstract: Bi₃NbTiO₉ (BNTO) powders were synthesized by a sol-gel chemical method using niobium oxalates, bismuth nitrate and tetra-n-butyl-titanate as starting materials. In order to determine the influence of the molar ratio of the deionized water to ethylene glycol on the particle morphology and crystallization, different molar ratios, the deionized water/ethylene glycol, were chosen to prepare BNTO powders. Single phase BNTO powders could be obtained at a calcinations temperature of 600°C. Moreover, the possible formation mechanism of BNTO powders was also proposed in this paper. In the baking process, perovskite phase BNTO was formed via a reaction between oxides and bismuth niobium.

Abstract: This paper presents a detailed analysis of the effect of slag refining and vacuum treatment on P removal from metallurgical-grade silicon using CaO-SiO₂-CaCl₂ slag. It demonstrates that both of CaO: SiO₂ ratio and CaCl₂ content have significant effects on the P removal. Increasing CaO: SiO₂ ratio was found to decrease the P removal efficiency after slag refining and vacuum treatment, and the distribution of P shows a tendency to concentrate in the precipitated phase after slag refining. It is also determined that the highest removal efficiency of P was attained when CaCl₂ content was 5wt%( CaO:SiO₂=1:1), but no obvious change was observed on P distribution after slag refining of varying CaCl₂ content.

Abstract: Used YAG pulse laser to weld 304 stainless steel nuts, studied about the parameters such as peak power, pulse width, defocus distance impacting on the performance of the joints welded by laser. The studies showed that the tensile strength and torque of the nuts increased as the peak power and the pulse width increased.Burn through in welding easy occur when laser pulse energy is too big, pulse width is too wide or defocus distance is too low.

Abstract: In this paper, the effect of rail head organization, cooling and quenching microstructure transformation time in different cooling speed are analyzed by the numerical simulation of the 60kg/m U75V, and study the change law of the rail temperature field and microstructure in the quenching process in the field.

Abstract: In this paper, the results of the first-stage research devoted to infrared thermographic detection of cracks in titanium alloys are presented. In application to the inspection of bottom-hole defects in 9.6 mm-thick Ti6Al4V titanium alloy samples, it has been found that a minimum detected defect should have diameter from one to two times greater than its depth. Images of phase are more noise-resistant and able to reveal deeper defects compared to images of amplitude. The test results obtained show that the Fourier analysis is a convenient data processing technique in active thermal NDT.