Advanced Materials Research Vols. 418-420

Abstract: We investigated the structural evolution of Polystyrene films at various conditions through multi-wavelength ellipsometry. We studied the thickness of film dependent of the process of swelling/shrinking, and the influence of the intensity of atmosphere，combining with PM (polarization microscope) to characterize the surface morphology. Results indicated that the increase and reduction of the film thickness are non-linear. Maximum swelling ratio and the variation of film thickness depend on the initial thickness of film and the intensity of atmosphere. Furthermore, the results demonstrated that in-situ multi-wavelength ellipsometry is an unique means to investigate the behavior of swelling and shrinking of film.

Abstract: The fatigue tests of Q235B steel unload longitudinal fillet welded joints containing high welding residual stress were carried out. And the effect of welding residual stress on fatigue performance of the welded joints treated by ultrasonic peening has been studied. Specimens were divided into four groups: as welded, specimens treated by ultrasonic peening(UP), specimens treated by stress relief treatment(SRT) and specimens treated by both ultrasonic peening and stress relief treatment(UP+SRT). Test results show that the effect on fatigue performance of the welded joints treated by ultrasonic peening from welding residual stress is small. It is safe that using the small specimens treated by ultrasonic peening and not containing high welding residual stress to appraise the fatigue performance improvement on large-scale welded structures which are as the same junction style and thickness as the small.

Abstract: AlN powders were prepared via carbothermal reduction-nitridation of nonhydrolytic Al₂O₃ gels. The XRD results showed that only AlN phase formed when the sample was calcined at 1450 °C in N2 flow of 80 ml/min, which was lower than that using Al₂O₃ powders as starting materials. The AlN powders were near-spherical particles and their particle size was around 400 nm. The effect of the CaF₂ addition on the synthesis of AlN powders was aslo investigated. The results showed that the synthesis temperature of AlN powders colud decrease to 1400 °C, when 3wt% of atalytic agent CaF₂ was added. Meanwhile, the particles size of AlN powders decreased, but their size distribution became wide range.

Abstract: The mass loss rate of carbon-bearing pellet of coexisted iron and niobium ore during reduction process was investigated between 900 and 1050°C in inert atmosphere. The reduction mechanism was studied by analyzing reaction rate constant, apparent activation energy，and the controlling step. The results show that temperature has the significant effect on the reduction of carbon-bearing pellet. The reduction processes include the faster reaction stage and the slower reduction stage, and respective reaction rate constants in two stages are k1=exp (21.025-40484/(RT)) and k2= exp (21.060-42516/(RT))，while respective apparent activation energy are 337 and 353 KJ/mol. Both steps are controlled by carbon gasification.

Abstract: Study the properties of AlSi9Cu3 aluminum alloy test bars fabricated by liquid forging with instruments such as optical microscope, direct reading spectrometer and micro-controlled electronic universal testing machine. Further more，analyze the microstructure and forming mechanism of AlSi9Cu3 aluminum alloy fabricated by liquid forging, the study shows : AlSi9Cu3 aluminum alloy fabricated by liquid forging has excellent performance and good prospects in production.

Abstract: During the rolling process, temperature is an important factor that affects the die and the work-piece in metal forming procedure. The metal deformation is often carried along with the variety of temperature. Moreover, mechanical energy of plastic deformation is converted into heat during the metal deformation process. Thus, it is necessary to couple the deformation and thermal behaviors in an integrated manner in numerical simulation so as to improve the simulation accuracy. In this paper, we use a 3D rigid-plastic Finite Element Method (FEM) to simulate the hot rolling process by coupling the thermal effects. Based on the 3D FEM model, integrated equations of coupling velocity and temperature fields are formulated. The uniform of integrated equations is obtained by re-indexing the combination sequences and then a modified coupling method is proposed to solve the resulted equations. The numerical experiments are carried on the real data collected from a steel plant. A good agreement between the numerical result and measured value shows the availability of the proposed coupling method.

Abstract: Ba_0.95Ca_0.05)TiO₃ (BCT) ferroelectric ceramics were prepared from powders synthesized using a sol–gel process. Structural evolution of the BCT dry gels are investigated by thermal gravimetric analysis differential scanning calorimetry. It is found that BCT crystallites can be formed before 800°C. Well-sintered samples are synthesized at 1320°C for 2h. The crystal structure of the BCT ceramics is studied by XRD and ferroelectric properties of the ceramics are characterized by TF analyzer 2000. The Curie temperature T_c of the BCT ceramics is at about 130°C. The maximum dielectric constant (ε_r) reaches about 13678 at 130°C and hysteresis loops are measured with the temperature range from 25°C to 150°C.

Abstract: The tribological performances of mixed PTFE-based composites were evaluated on the MM-200 block-on-ring test rig under dry friction condition. The following filler contents: carbon fiber (CF), flake graphite (FG) and spherical graphite (SG) were adopted to investigate their effects on the tribological performances of the composites. The experiments were carried out by a four levels orthogonal table-L₁₆（4³）, and the experiment data were deal with the methods of range and variance analysis. The results shown that all the filler contents could reduce wear, and the wear rate was stable when the content of fillers were more than 10 wt.%. The degrees of three fillers affecting the wear of composites were CF>FG>SG, and that affecting the friction coefficient were SG>CF>FG. The friction coefficient decreased with increasing the contents of SG, increased with that of CF, first decreased and then increased with that of FG. When the contents of FG is 15 wt.%, the friction coefficient is the lowest. The main worn form was adhesion wear.

Abstract: An unascertained measurement model was proposed for regional water safety assessment after choosing the proper index system of water safety characteristics in Shandong province. Unascertained measurement was obtained by calculating the single index with the weight power of each index by project pursuit method. By applying the unascertained measurement model to water safety assessment in Shandong province, the results show that it provides an effective approach to water safety assessment.

Abstract: Autothermal reforming of methanol is considered to be a promising choice for hydrogen production. However, due to the fact that a series of complex chemical reactions are involved, an exact mathematical model is extremely hard to be established, which makes the control of the process a recognized difficulty. Therefore, an adaptive feedback control method is proposed in this work for the control of hydrogen production through autothermal reforming of methanol without the requirement of an accurate model. Theoretical analysis proves that this control strategy can achieve very good performance even when the system’s parameters change significantly. Moreover, simulation results demonstrate the feasibility of this approach.