Key Engineering Materials Vols. 575-576

Abstract: With the continuous spreading of scale in power system and introducing of fast excitation system, the problem of low frequency oscillation which is arosed because of lacking-damping becomes worse and worse. This paper analyzes the mechanism reasons of insufficient-damping, using an auxiliary control unitpower system stabilizer (PSS) to increase the damping torque. Through established a simulation model of excitation control system on a typical single machine-infinite bus system, simulates the synchronous generators transient operating characteristics under large and small disturbances, and the simulation results show that the design can improve the system damping and the generator operating characteristics, increase power system dynamic stability.

Abstract: By doing Erichsen experiments, samples of hot-dip galvanized sheet under different Erichsen depths (ED) were got. Surface and cross-section of these samples were analyzed by using SEM and EDS, which can show morphology and chemical composition respectively. Failure modes of galvanized sheet under different ED were researched. Then evolution process of zinc coating failure and effects of it on galvanized sheet formability were discussed. The results indicate that during hot-dip galvanized sheet stamping, zinc coating will pulverize, exfoliate and fracture for influence of friction and forming force, which leads to decrease of galvanized sheet formability.

Abstract: Rhodamine B is one of biodegradable azo dyes. In this thesis, the CoPc-LDHs were prepared by applying cobalt phthalocyanine on the Mg-Al hydrotalcites, and catalytic oxidation decolorization of rhodamine B (RhB) was studied. The results shown that compared with H₂O₂, CoPc-LDHs play a key role in catalytic oxidation of RhB. The optimal conditions about CoPc-LDHs/H₂O₂ system were H₂O₂ (30% w/w) 1.50 mL, pH 7 and 62.5°C. The catalytic oxidation decolorization effect of RhB reduced with the increase of initial concentration of RhB.

Abstract: Low-density proppants have been developed using two kinds of bauxites containing different ratios of aluminum as main raw materials and compound liquid as a binding agent. The influences of the amount of compound bonding agent and the sintering temperature on the performance of the proppant were studied. The phase composition of calcined sample was identified by X-ray diffraction (XRD) method. The microstructure of the sintered sample was characterized by scanning electron microscope (SEM). It is shown that the proppant prepared with increasing compound bonding agent can meet the national standard. With the increase of the sintering temperature, mullite with uniform grain size is formed.

Abstract: A closed isothermal forging process was adopted for precision forming of the Ti-6Al-4V wing with a variable cross-section asymmetric structure. Firstly, simulations under different process parameters, such as the deformation temperature, punchs velocity et al. were analyzed with DEFORM-3D software to eliminate the defects in the isothermal forming process. The simulation results demonstrated that the loads during isothermal deformation were determined not just by the forging temperature but the punchs velocity, the less velocity of punch, the better filling ability, and yet temperatures from 900 to 950°C had less influence on filling ability. To verify the validity of simulation results, the isothermal forging experiment was carried out on an isothermal forging hydraulic press (THP10-630). It is demonstrated that the optimized billet dimension can ensure the quality of forging part and the titanium alloy wing component with complex shape was successfully forged with the punch speed of 0.1mm/s at 950°C and its mechanical performances were improved.

Abstract: MAC cementing material was in-situ synthesized with different ratios of raw materials and sintering temperatures. The raw materials include hydrated lime, magnesite and alumina. X-ray diffraction analysis indicates that the major mineral phases in the MAC are monocalcium aluminate (CA), magnesium aluminate spinel (MA) and calcium aluminate (C₇A₁₂). The relative contents of the mineral and amorphous phase were simply calculated based on the relative diffraction peaks and MgO-Al₂O₃-CaO ternary phase diagram. SEM and EDS analysis indicate that the MAC cementing material includes layered structured CA, long strip C₇A₁₂ and octahedral MA.

Abstract: The reactions of aniline with CO₂ and CS₂ were investigated in the presence of sublimed AlCl₃ under the mild conditions (room temperature and ambient atmosphere). Reasonable mechanism, electrophilic substitution of carbonium and nitronium, was also provided according to GC/MS analysis of the reaction products. The resulting N,N-diphenylurea (DPU, high selectivity of 92.5mol%) and N,N-diphenyl thiourea (DPTU, high yield and selectivity of 80.1mol% and 99.7mol%, respectively) were purified by recrystallizing from ethanol and identified by melting point, element analysis, GC/MS, FTIR, UV and ¹H NMR data.

Abstract: The influences of the impact angle and the corrosive agent acidity on low-chromium and nickel contained cast iron were studied in the behavior of erosion wear. The wear rule was summarized and the mechanics of the erosion wear behavior were analyzed in this thesis. Erosion wear experiments were carried on MCF-30 erosion test machine, and then the structure and surface morphology of the samples were analyzed by Scanning Electron Microscopy (SEM). The results showed that the alloy carbide (Fe, Cr)3C was generated by a kind of reticulate distribution in the matrix after oil quench at 960°C and temper at 250°C. The continuous and homogeneous distribution, just like the skeleton of the material, enhanced the wear resistance. The shape of erosion wear curve was M at different impact angles. The biggest wear rate occurred at a 60-degree impact angle. The erosion wear property was greatly affected by the strong acid, but it can be ignored when pH3.

Abstract: Extraction with ionic liquids joined with adsorption and catalytic oxidation composed with commercially available tungsten carbide, 30% H₂O₂ and 1-n-octyl-3-methylimidazolium hexafluorophosphate ([omim]PF₆) could achieve the ultra-deep removal of dibenzothiophene (DBT) in model oil. In the case of the system increased the sulfur removal to 100% for 1h, which was remarkably superior to mere solvent extraction with IL (29.4%) or adsorption and catalytic oxidation without IL (2.0%). Especially, we found that the removal of 4,6-DMDBT could be up to 100%. The system could be recycled at least 12 times and the deep removal of DBT still could be achieved.

Abstract: Thermal microimprint is a promising technology for polymer microstructure, so it is used to form V-groove on the surface of optical devices. However, it is difficult to control the size accuracy of V-groove because of the elastic recovery of polymer. In order to solve the problem, the influencing factors on the polymer elastic recovery were firstly analyzed in this article. Then, it was proposed that the embossment height of mold should be modified according to the depth of V-groove and the modifier formulas should be constructed based on the theory of polymer viscoelasticity. In the end, the optimal technological parameters of thermal microimprint were obtained through the thermal imprint experiments, and the embossment height of the mold after modification was calculated according to the experimental data, and thus a new mold was produced as to verify the accuracy of the modifier formulas. The results showed that the approach of modification could not only ensure dimension accuracy of V-groove, by keeping the error within 1μm, but also shorten the imprint time, consequently the efficiency of thermal microimprint would be improved.