Applied Mechanics and Materials Vols. 174-177

Abstract: The pore structure characteristics of reactive powder concrete (RPC) were investigated by means of the mercury injection method at seven temperature levels, namely, 20°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, respectively. The characteristic parameters such as porosity, pore volume, average pore size and threshold aperture varied with temperatures were analyzed. The results indicate that the porosity, pore volume, threshold aperture and other characteristic parameters of RPC increased with the temperature increasing.

Abstract: By adopting a facile solution combustion synthesis (SCS) method, pure well-crystallized (Ba,Sr)MgAl₁₀O₁₇:Mn green phosphors were successfully prepared. The crystallinity, particle size, morphology, and luminescent properties were characterized by XRD, FE-SEM and spectrofluorometer respectively. The results indicated that the obtained phosphors have spherical morphology, good crystallinity, and strong green emission. The emission spectra of obtained nanophosphor on 147nm excitation consist of a wide band with the peak at 518nm, which corresponds to the transition from the 3d⁵(⁴T_1g) excited state to the 3d⁵(⁶A_1g) ground state of Mn2+. The synthesized phosphors can be efficiently excited at VUV light and have potential application in Plasma Display Panels (PDPs), 3D displays and mercury-free fluorescent lamps

Abstract: By this method of adding fly ash of equal amount in the mortar, making analysis including the decreasing water change、7d and 28d compressive strength as well as flexural strength. Results show that exists the optimum proportion of fly ash cement mortar, that is C：F：S：W=220：55：1410：275.On the basis of mixing only 20% fly ash and epoxy resin-polymer, doing analysis about the decreasing water change、7d compressive strength and flexural strength、application property. At the same time, this paper fits the regression equation which using the 7d compressive strength and flexural strength、decreasing water rate as the dependent variables, polymer cement ratio as the independent variable. More important is that the credibility of regression equation is much high.

Abstract: Effects of aluminum-leached coal fly ash residue on water-resistance, compression strength and efflorescence of MOC cement have been investigated. The results show that the compression strength of MOC cement curried for 28 days increases with the dosage of ACFAR. The water resistance of MOC cement can be improved obviously. This study has proved that aluminum-leached coal fly ash residue can be used as the filling material of MOC cement with high compression strength and good water-resistance.

Abstract: In this research, trace boron (4ppm, 8ppm, 11ppm) was added into the Nb-added HSLA H-beams. The impact toughness of H-beams with/without boron was examined by Charpy impact test (V-notch). The morphologies of the microstructure and the fracture surfaces of the impact specimens were observed by metalloscope, stereomicroscope and electron probe. The experimental results prove that the absorbed impact energy at -40°C for the 4ppm, 8ppm, 11ppm boron-added steels respectively reaches up to 80J, 126J, 85J from 15J and H-beams with boron have a lower FATT than that without boron. It is also found that the total oxygen content affects the absorbed impact energy to a certain extent. It is discovered by transmission electron microscope (TEM) that boron mainly exists in solid solution state, except that a little amount of Fe₂₃(C, B)₆ is formed at the grain boundaries, and the distribution of Nb(C, N) is also influenced by boron addition.

Abstract: Magnesium Hydroxide Sulfate Hydrate (MgSO4•5Mg(OH)2•3H2O, MHSH) whiskers were synthesized via the hydrothermal method in a mixed solution of magnesium sulfate (MS) and NH3•H2O . X-ray powder diffraction (XRD) investigations showed that the phase composition changed from Mg(OH)2 to MHSH as the volume ratio of MS / NH3•H2O increasing gradually. Accordingly, SEM images showed that the morphological structures changed from granule dominant to whisker dominant. The morphology of the samples changed from lathy to whisker gradually as the reaction time increasing under the same volume ratio of MS / NH3•H2O and reaction temperature of 180 °C.

Abstract: The biodegradable composite films were prepared from corn stalk microcrystalline cellulose as filler and chitosan as polymeric matrix. The crystallinity, the tensile properties and the thermal properties of the composites were tested. The results show that the tensile properties and thermal properties were improved with the addition of corn stalk microcrystalline cellulose. When corn stalk microcrystalline cellulose account for 10% of the chitosan quality, the initial decomposition and maximum weight loss rate temperature was raised by 13.19°C and 38.84°C, tensile strength increased by 83.55% and elongation at break increased by 77.38% compared to those of pure chitosan

Abstract: Polyurethane composite panel is a sandwich panel made up of polyurethane and structural surface board, formed by polyurethane foaming. Through bending test on 12 polyurethane composite panels in 4 groups, test results on bending capacity and load-deformation curve for this type of panel are obtained, which set the foundation for further experimental study and theoretical analysis.

Abstract: The bending strength and crack-resistance performance of blank concretes are poor, which are not favorable to the sustainable development of infrastructure. Engineered cementitious composite (ECC) is a high performance fiber-reinforced cementitious composite designed with micromechanical principles, which can improve concrete bending performance to prolong service life and to reduce maintenance cost of infrastructure, so there is important significance for sustainable development of infrastructure. In this study, we have experimentally evaluated the effectiveness of bending and crack-resistance performance of concretes reinforced by different kinds of fibers which include UF500 cellulose fiber (UF500), polyvinyl alcohol (PVA) fiber, polypropylene (PP) fiber and hybrid-fiber (PVA and UF500 cellulose fibers), respectively. The bending performance of concrete with different kinds of fibers is better than that of blank concrete. In addition, early crack-resistance performance of hybrid-fibres enhanced samples has been improved as confirmed by the three-point bending test.

Abstract: In order to reveal the constitutive behavior of recycled aggregate concrete (RAC) which is related to time effect, 33 prismatic specimens were designed to have uniaxial compression tests. The changing variation of elastic modulus and Poisson’s ratios of RAC specimens which were placed two years in the lab were inspected, and a related correction formula was put forward to describe the elastic modulus. The results show that with the aggregate replacement rate growing, the RAC brittleness was relatively obvious. Since time effect played a great role, the axial compressive strength and elastic modulus were larger than those of normal concrete and the standard age concrete which is calculated. Poisson's ratio did not change significantly and the values were relatively stable, while the higher replacement rate is, the lower values are.