Advanced Materials Research Vols. 915-916

Abstract: According to the GH3044 nickel-based superalloy with high yield strength, a new approach for superalloy tube named Tube Solid Granules Medium Forming (SGMF) was present, and tube SGMF process principle and the mechanical model of solid granules were designed. The superalloy tube SGMF process was investigated numerically by using User subroutine of Abaqus software, the deforming simulations of two groups of tube products were performed separately, and the elongation rate and thickness distributions of the products were analyzed. An experimental system was designed and developed for tube SGMF, typical GH3044 superalloy tubes were deformed, good correlation was observed between the simulation results and experimental data.

Abstract: Density functional theory (DFT) is used to calculate the C-NO₂ bond dissociation energies (BDEs) in nitrobenzene; 3-amino-nitrobenze; 4-amino-nitrobenze; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-methyl-nitrobenzene; 4-methyl-nitrobenzene and 1,3,5-trinitrobenzene nitroaromatic molecular system. B3P86 and PBE0 methods in combination with 6-31G** and 6-311G** basis sets are employed. Comparison between the computational results and the experimental values reveals that the calculated C-NO₂ bond BDEs can be improved from B3P86 to PBE0 functional. Level of theory employing PBE0/6-311G** is found to be sufficiently reliable to compute BDEs of C-NO₂ bond for nitroaromatic molecules with an average absolute error of 0.98 kcal mol^-1.

Abstract: Frequency selective surfaces (FSS) and recent metamaterials (MTM) have shown unique electromagnetic characteristics and are of potential benefits for radome applications. To make the radomes/windows high-temperature resistant, the substrates of the frequency selective surfaces or metamaterials should be made of ceramic/glass-based materials of a low dielectric constant and a low loss tangent. However, fabricating ceramic/glass-based FSS or MTM is always challenging. In this paper, a constrained low-temperature co-fired ceramic (LTCC) technique was used to produce quartz glass-based radome material consisting of a frequency selective surface (FSs) layer embedded in a surface laminate. Due to the constrained sintering shrinkage, the geometry and the dimensions of the unit cells of the FSs were not subjected to significant variations and thus the measured electromagnetic (EM) wave transmission spectra matched those of the computer simulation results quite well. This preliminary work marks the beginning of our long-term efforts toward the goal of achieving high-temperature resistant, highly electromagnetic wave transparent, as well as carefullydesigned and fabricated radome materials.

Abstract: With the methods of studying conventional concrete mechanical performance, the influence of concrete performance on the rubber powder replacement rate is investigated. Based on the test data, the relationship of between the elastic modulus and the rubber powder replacement rate is fitted. The results show that the concrete slump decreases with the rubber substitution rate increasing. The compressive strength of the cube of the concrete, the axial compressive strength and the elastic modulus go down in different degree with the increment of the rubber substitution rate.

Abstract: For the purpose of investigating the influence of graphite addition on the property of carbonyl iron absorber, some samples were made by mixing graphite and carbonyl iron powders. The electro-magnetic parameters were then measured and compared between samples containing different graphite mass ratio. Microstructures of these samples were observed to make sure that additions were uniformly distributed in these samples. By this way, the influence of graphite addition was systematically analyzed.

Abstract: For the purse of improving the microwave absorption ability of carbonyl iron, Co power was chosen as additions to add into the sample. Both analyze and measurement proved that the addition of Co power effectively decreased the conductivity, while not obviously destroyed the magnetic property of the sample. In this way, the addition of Co power improved the sample surface matching effect, and correspondingly, the absorption ability is increased.

Abstract: Anti-lightning strike protection for composite structures is catching great attention to design optimum lightning protection solution. Based on lightning direct effect, optimizations of flame spraying aluminum thickness and composite laminate plies were conducted by combining electrical-thermal analysis procedure and corresponding optimization programs. Optimized thickness was acquired for flame spraying aluminum layer. Meanwhile, non-uniform thick plies and optimized stacking angles were given for anti-lightning strike composite laminate. Comparisons were conducted to investigate changes of lightning direct effects on composite laminates fore and after optimization. Synergetic protections of flame spraying aluminum and laminate plies design were listed. The conclusions can be used as suggestions for lightning strike protection of advanced aircraft.

Abstract: Full thickness cold recycling subgrade materials were prepared by cement-emulsified asphalt solidified RAP and stabilized soil.The effect of adding amount of emulsified asphalts change on unconfined compressive strength, indirect tensile strength and water stability of cold recycled mixtures with different ratios was studied,and the mechanism of action of cement and emulsified asphalt in the mixtures was analysised via microscopic test. The results show that a proper addition of emulsified asphalt can improve the performance of cold recycled mixtures and the best emulsified asphalt mixing content is 3%. Microscopic test indicate that the cement hydration products space network structure interfinger with the emulsified asphalt network structure, so the cold recycled mixture tightly coupled to a semi-rigid whole, and the mixtures strength can form and develop.

Abstract: In this paper nanoSiO₂ particles were prepared with the surface grafted fluorine coupling agents and double bond by using surface modification technology. Dispersion effect of nanoSiO₂ particles were studied in different solvents ultrasound cavitation. Test results showed in infrared spectroscopy, TEM and laser particle size distribution analyzer that both F8261 and KH-570 have been grafted onto the surface of nanoSiO₂ , particle size and distribution of nanoSiO₂ after modified by the two coupling agent became smaller and more narrow; Tg-DSC analysis showed that when the amount of of the coupling agent is up to 10%, fluorine coupling agent and double bond grafted onto surface of nanoSiO₂ particles reach the saturation.

Abstract: In this investigation, Schiff bases aluminum complex was synthesized and used as the initiator in the polymerization of D,L-lactide. The aluminum complex was characterized by infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). The influences of different factors, including reaction time, reaction temperature, and the ratio of D, L-lactide/Al³⁺ on the synthesis of polylactide were described. The results showed that Schiff bases aluminum complex could be successfully applied in the ring opening polymerization. The optimum condition of the ring opening polymerization of D,L-lactide, which included D,L-lactide/Al³⁺ (mol/mol) ratio of 250, reaction temperature of 120 °C, and reaction time of 16 hours.