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Advances in Materials Science and Engineering publishes research in all areas of materials science and engineering, including the synthesis and properties of materials, and their applications in engineering applications.
Chief Editor, Amit Bandyopadhyay, is based at Washington State University and is interested in the fields of additive manufacturing or 3D printing of advanced materials. His current research is focused on metal additive manufacturing, biomedical devices and multi‑materials structures.
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Sorptive Removal of Color Dye Safranin O by Fibrous Clay Minerals and Zeolites
The increased use of color dyes in industry imposes a great threat to the environment. As such, developing cost-effective techniques for dye removal from wastewater attracted great attention. Earth materials, particularly those with large specific surface area (SSA) and high cation exchange capacity (CEC), were evaluated for their potential use for wastewater treatment. In this study, palygorskite, sepiolite, and clinoptilolite were evaluated for their removal of cationic dyes using safranin O (SO+) as a model compound. The CEC values of the materials played a key role in SO+ removal while other physicochemical conditions, such as temperature, equilibrium solution pH, and ionic strength, had less influence on SO+ removal. Sorbed SO+ cations were limited to the external surfaces of the minerals, as their channel sizes are less than the size of SO+ cation. Molecular dynamic simulations showed dense monolayer SO+ uptake on palygorskite due to its relatively large CEC value. In contrast, loosely packed monomer SO+ uptake was adopted on sepiolite for its large SSA and low CEC. Dense multilayers or admicelles of SO+ formed on zeolite surfaces. As such, for the best SO removal, palygorskite is better than sepiolite, though both are fibrous clay minerals.
Vibration Response Analysis of Simply Supported Box Girder Bridge-Maglev Train in Accelerated Test of Changsha Maglev Express
In order to study and analyze the vibration response of simply supported box girder bridge-maglev vehicle, a 25 m span simply supported box girder bridge of Changsha Maglev Express was selected as the research object. Field tests were carried out to explore the dynamic response of maglev vehicle running on the bridge. Firstly, the dynamic characteristics of the bridge under the action of medium-low speed maglev train at different speeds were analyzed, and the vibration response of vehicle and bridge was studied at the design speed of 60∼130 km/h. Among them, the longitudinal acceleration of simply supported box girder ranged from 60 km/h to 130 km/h, which increased linearly with the speed of the train and reached the maximum 0.59 m/s2. Its longitudinal deflection also increased with the increase in train speed, which reached the maximum 1.605 mm at 130 km/h. When the speed is 130 km/h, the suspension gap of the maglev vehicle was concentrated in the range of 7.24∼11.50 mm. Through the test analysis, this study provides a basis for the vibration response analysis of simply supported box girder bridge-maglev train. It also provides a reference for the modification and formulation of relevant specifications and experimental verification for the acceleration work of medium-low speed maglev train in the future.
Hydrothermal Preparation of Ag/Ag1.69Sb2.27O6.25 Sesame-Hollow-Ball-Type Nanocomposites: The Formation Mechanism of Metallic Ag in the Ag-H2O System at 400 K
Ag/Ag1.69Sb2.27O6.25 sesame-hollow-ball-type nanocomposites were prepared via a facile one-step hydrothermal method at 400 K. Power X-ray diffraction analysis shows that all diffraction peaks were well consistent with JCPDS card no: 89-6552 of Ag1.69Sb2.27O6.25. Scanning electron microscopy and high-resolution transmission electron microscopy images of the composites indicate that some smaller metallic Ag particles with size∼18.3 nm uniformly dense on the surface of Ag1.69Sb2.27O6.25 hollow nanospheres with a mean size of about 170 nm, producing Ag/Ag1.69Sb2.27O6.25 hollow-sesame-ball nanocomposites. The surface chemical state of Ag/Ag1.69Sb2.27O6.25 is investigated by XPS, and all peaks of Ag 3d, O 1s, and Sb 3d show their different chemical states. The BET surface area of the sample is 7.268 m2/g, and the pore sizes of nanocomposites are more than 5 nm. The light absorption property of as-prepared materials is studied by UV-vis/DRS, and the adsorption band is located at 445 nm, and the estimated energy band gap (Eg) is 2.55 eV. The calculated partial φ-pH diagrams in the Ag-H2O system at 400 K predict that the Ag+ ion can react with H2 to form metallic Ag.
Microwave Heating Characteristics of Emulsified Asphalt Repair Materials Incorporated with Steel Slag
Emulsified asphalt needs to be cured for a certain age after demulsification to produce strength, which seriously affects the traffic opening time. In this work, microwave heating technology was applied for emulsified asphalt repair materials. Steel slag with high microwave activity was adopted to improve the performance of emulsified asphalt repair materials by microwave heating. Effects of steel slag sizes and contents on the heating rate, temperature distribution, and thermal performance of emulsified asphalt repair materials were analyzed by close microwave heating, open microwave heating, and repair simulation tests. Results show that the temperature of emulsified asphalt repair materials presents three different heating stages under microwave irradiation. The “critical point of phase transition” in the three stages is gradually advanced with the increase in steel slag content. The core temperature and maximum temperature of emulsified asphalt repair materials with different steel slag sizes are basically the same; however, the heat distribution of emulsified asphalt repair materials is significantly different. In contrast to conventional asphalt mixture, there exists a smaller temperature difference. The temperature of repairing materials can reach above 80°C. The interface area can form an embedded interface structure. Incorporation of steel slag and adoption of microwave heating are effective to improve the performance of emulsified asphalt repair materials.
Experimental Study on the Creep Characteristics of Cemented Backfill in a Goaf Underwater Pressure
As the groundwater environment changes in a goaf, the creep deformation of the backfill underwater pressure is worthy of attention. This paper takes the undercut goaf filling in the Yuzhou section of the middle route of the South-to-North Water Transfer Project as an example. Grading loading creep testing of the backfill under different water pressures was carried out using equipment developed by our research team. Based on the experimental results, the following key points were observed: (1) under the same axial stress, the creep strain and steady creep rate increase with increasing water pressure. Under the same water pressure, the creep strain and steady creep rate also increase with increasing axial stress. (2) The long-term strength of a backfill sample decreases with increasing water pressure and has a nonlinear relationship with water pressure. (3) The increase in water pressure exacerbates the damage of a backfill sample, which is manifested by the secondary crack propagation at the time of failure. Therefore, the increase in water pressure degrades the mechanical properties of the backfill to some extent. The results of this paper provide a reliable theoretical basis for the long-term stability analysis of goaf filling underwater pressure.
Orthogonal Analysis and Numerical Simulation of Rock Mechanics Parameters in Stress Field of Shaft Heading Face
This paper focuses on improving the blasting effect of the drilling and blasting method in the deep rock mass and solves the problems of blasthole collapse and misfire accident in the process of drilling and blasting construction of heading face. FEM software, ABAQUS, is used to simulate the stress distribution around the blasthole by extending a certain depth in the vertical direction of the shaft heading face. The sensitivity of different depths, different heading face sizes, and different lithologies on the horizontal stress distribution is analyzed by using a six-factor four-level orthogonal analysis method. The results show that the change of the radius of the heading face has the most considerable influence on the distance of the distressed zone and the stress concentration zone, followed by the lithology and the excavation depth. Also, the excavation depth has the most significant influence on the peak stress value. Through the industrial field experiment, the in situ stress of the shaft heading face is tested, and the numerical simulation results are consistent with the field monitoring results. The results reveal the law of stress distribution near the heading face, which can provide some reference for the design of blasthole depth in the drilling and blasting construction scheme.