Advanced Materials Research Vol. 905

Abstract: Molecular structures of pyridopyrimidines derivatives as known as dihydrofolate reductase (DHFR) inhibitors were investigated by using the neural network method. Based on the molecular connectivity, molecular connectivity index and molecular electronegativity distance vectors of 32 pyridopyrimidine derivatives were obtained. Among these parameters, three optimized structural parameters ¹χ³χ and M₁₇ as the input neurons of the artificial neural network were selected by step-wise regression. Then a 3:4:1 network architecture was employed and a satisfying neural network model for predicting anticancer activity (lg1/C) was constructed with the back-propagation (BP) algorithm. The total correlation coefficient R and the standard deviation S were 0.925 and 0.336 respectively that showed significantly nonlinear relationships between lg1/C and three structural parameters. It was concluded that the predictions of BP neural network are better than those of methods in the literatures.

Abstract: BiVO₄-graphene composites were prepared through a one-pot hydrothermal synthesis method, and the structure were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron emission spectroscopy (XPS), X-ray powder diffraction (XRD) and Transmission electron microscope (TEM). The results show that BiVO₄-graphene composites are successfully prepared, and BiVO₄ particles are almost uniformly deposited on the surface of graphene.

Abstract: This paper investigates the dispersion characteristics of shear horizontal waves propagating in a piezoelectric cylinder covered by orthotropic layer. The surface of the orthotropic layer is assumed to be mechanically free; The stress and displacement at the interface is continuous. The solution of the equation is expressed by Bessel function, and the dispersion equation is derived by using the boundary conditions and the interface conditions, the numerical examples are provided to show the influences of the orthotropic degree and the properties of piezoelectric materials on the dispersion characteristics of SH waves.

Abstract: Hypoeutectic and hypereutectic Al₂O₃+ZrO2 multiphase ceramic-lined composite pipes were produced by using the gravitational separation self-propagate high-temperature (SHS) process. The microstructure of the ceramics was observed by means of SEM and EPMA. The multi-phase ceramics base consists of lamellar or rod-like eutecticum of ZrO₂ with Al₂O₃, and Al₂O₃ dendrite is distributed between (Al₂O₃+ZrO₂) eutecticum and the ZrO₂ is distributed on boundary area between (Al₂O₃+ZrO₂) eutecticum in appearance of band and particle alone in the hypoeutectic multi-phase ceramics, and ZrO₂ is distributed between (Al₂O₃+ZrO₂) eutecticum in appearance of snowflake-like or fishbone-like in hypereutectic multi-phase ceramics. On the basis of combustion synthesis, material thermodynamics, metallurgy dynamics and ceramics materials theory, the formation of microstructure mechanism have been systematically investigated.

Abstract: A novel process of electroless Ni-P plating on magnesium-lithium alloy is discussed in this paper, by which nickel ions are provided by basic nickel carbonate and a new pretreatment method is introduced to obtain good quality coating. The corrosion behavior of magnesium-lithium alloy without or with coating was compared and the bonding strength of the electroless Ni-P coating to the matrix surface was also measured. The results showed that the process of electroless Ni-P plating can be easily achieved on the intermediate layer and a compact Ni-P coating without flaws is formed synchronously. The thickness of Ni-P coating is above 20 μm and its phosphorus content is about 10.501wt.%. The corrosion potential of magnesium-lithium alloy coated by Ni-P increases obviously (-0.315V) during the anodic polarization in 3.5 wt. % NaCl solution and this phenomenon indicates that an effective protection has been formed for the alloy. It was proved that the Ni-P coating adheres on magnesium-lithium alloy surface tightly through the file test and cross cut test.

Abstract: In situ aluminum matrix composites were fabricated through exothermic dispersive (XD) reaction from a powder mixture of Al and Cr₂O₃. The reaction mechanism was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and differential scanning calorimetry (DSC) analysis. When the temperature increases to around 1050K, Al can react with Cr₂O₃ to form the reinforcments Al₂O₃ particles and CrAl₄ blocks. With the increase of heating rate, DSC analysis shows that the reaction peak shifts to a higher temperature and the corresponding ignition temperature also increases. Based on DSC curves with different heating rates, the activation energy can be calculated and its value is 191.8 kJ/mol.

Abstract: 0Cr18Ni10Ti stainless steel was coated by hot-dipping in a molten aluminum bath, and then diffusing annealing at 950°C for 2h. The high temperature isothermal oxidation behaviors of the hot-dipped aluminized steel and 0Cr18Ni10Ti steel were tested at 900 °C for 24h using Thermo gravimetric analyzer. The high temperature cyclic oxidation behaviors of the hot-dipped aluminized steel and 0Cr18Ni10Ti steel were tested at 900 °C for 24h using resistance furnace. The morphology was studied by SEM, the phase composition was characterized by EDS. The result of high temperature isothermal and cyclic oxidation test showed that the hot-dipped aluminum can dramatically improve the isothermal and cyclic oxidation of the 0Cr18Ni10Ti steel. The hot-dipping aluminum coating is consists of an outer layer of FeAl and an inner Iron solid solution with aluminum, after diffusion annealing at 950°C for 2 h. The Al2O3 oxide layer was formed on the hot-dipped aluminum coating during isothermal and cyclic oxidation process, which provides an additional protection for the steel from high temperature oxidation.

Abstract: The vulcanized styrene-butadiene rubber (SBR) was studied using X-ray absorption near edge spectroscopy (XANES). The effect of the sulfur containing molecules left over in the sample on the precision of the sulfur K-edge XANES spectrum was focused. The six rubber compounds used here were vulcanized with different curing systems including convention, semi-efficiency and efficiency. For each compound, the measurements were preformed on two different samples which were the untreated and treated chloroform samples. The results showed when compounds were cured with conventional or semi-efficient vulcanization system, the XANES spectra between the untreated and treated sample was changed with very high sulfur to accelerator ratio. On the other hand, the tremendous dissimilarity was observed when compounds were cured with the efficient vulcanization system. Thus the sample treatment was necessary when using XANES to identify sulfur crosslink.

Abstract: The aim of work consists in the study of interactions on solder/substrate boundary in fluxless soldering of Al with 4N purity by ultrasound activation. The ZnAg6Al6 and ZnAl4 solders were used in experiments. The soldering parameters were as follows: soldering temperature from 400 oC to 420 oC, acting time of ultrasonic vibrations 5 to 20 s, ultrasound frequency 40 kHz. Soldered joints were assessed by optical light microscopy, EDXmicroanalysis and XRD analysis. It was found out that the ZnAg6Al6 solder is composed of αAl, βZn solid solutions and AgZn₃phase. The ZnAl4solder consists of βZn primary solid solution and a lamellar eutectic Zn-Al structure. The main mechanism of joint formation between the solders type Zn-Al and Al substrate during soldering consists in eutectic reaction between the liquid Zn and solid Al. An eutectic βZn-αAl mixture was observed on the joint boundary in case of both solders. In case of Al/ZnAg6Al6 joint also AgZn₃intermetallic compound was observed in the transition zone.

Abstract: Structural steels have been developed in terms of users needs. Particularly, easy welding is one of the most important factors of steel works that results in submarine structural steel (SM). The SM has become a popular structural steel in building construction in columns and beams proving as good as ordinary structural steels (SS). However, evaluation of fire resistance at H-section made of SM steels was not suggested in terms of boundary conditions. In this paper, to compare the fire resistance of H-section made of SM steels, such as SM 400, SM 490, and SM 520 was tested and analyzed in terms of load carrying capacity at high temperature. The facts showed that as the strength is increased, the reduction ratio of an allowable load is rapid and fixed to fixed boundary condition was more robust than others in high temperatures.