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  • 1
    Publication Date: 2018-08-30
    Description: Biomass resources have the potential to produce clean-energy. However, their physico-chemical properties are inferior to those of coal, and thus, biomass resources are not regarded as ideal feedstock for industrial application. In the present study, the pyrolysis of corn (maize) straw pellets was performed under different temperatures (400, 450, 500, 550 and 600°C) at a 10°C min –1 heating rate and 30 min residence time, and the characteristics of biochar pellets were carefully investigated, particularly their elemental composition, hydrophobicity and mechanical resistance. Fourier transform infrared, proximate analysis and scanning electron microscopy were performed. Results indicated that the mass and energy yields of the biochar pellets decreased from 35.46 to 28.65% and from 50.17 to 45.52%, respectively, at increased temperature. Meanwhile, the higher heating value of the biochar pellets increased from 15.45 MJ kg –1 in the raw materials to 21.86 and 24.55 MJ kg –1 in the biochar produced at 400 and 600°C, respectively. In addition, biochar pellets showed good hydrophobicity, which benefited their storage and transportation, though mechanical resistance decreased. The pellets had compact structures, regular shapes and weakened or no functional groups in contrast with raw pellets, and these properties played important roles in the improvements.
    Keywords: energy
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 2
    Publication Date: 2018-07-19
    Description: High-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) fibre composites were prepared via solution crystallization to investigate the components of epitaxial crystal growth on a highly oriented substrate. Scanning electron microscopy morphologies of HDPE crystals on UHMWPE fibres revealed that the edge-on ribbon pattern crystals that were formed initially on UHMWPE fibres converted afterwards to a sheet shape as crystallization progressed. Wide-angle X-ray diffraction confirmed that the polymer chain oriented along the fibre axis and the orthorhombic crystal form of HDPE remained unchanged in HDPE/UHMWPE fibre composite systems. The thermal behaviour of the fibre composites measured by differential scanning calorimetry showed double melting peaks, the nature of which, as disclosed by partial melting experiments, is ascribed to bilayer components existing in the induced crystals: the inner layer is composed of more regularly folded chain crystals induced by UHMWPE fibres, and the outer layer formed on the inner one with a thinner and lower ordered crystal structure.
    Keywords: chemical physics
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 3
    Publication Date: 2018-11-22
    Description: The characteristics of pure α - and β -form of the cyclic dimer (1,8-diazacyclotetradecane-2,9-dione) were systematically and integrally investigated during this study. The results showed that the α -form could dissolve and rapidly transform into the β -form in methanol, and in caprolactam solution at a lower temperature, an interesting transition occurred and formed co-precipitates, which refract colourful light under PLM. However, these dimers can aggregate in water, and they are then transformed into multi-slice layers and compact structures. The detailed transition behaviours between the two forms were further measured by FT-IR, XRD and DSC by varying the temperature from 25°C to 360°C, respectively, which showed that there are two endothermic transitions over the course of the heating programme. At a temperature of approximately 242°C, the β crystals were initially converted into α crystals, and then they melted when the temperature reached over 345°C. A video recorded under a light microscope also showed that the sublimation of the β cyclic dimer occurred after the transition. However, the α -form might sublimate at temperatures lower than 150°C when mixed with volatile matter.
    Keywords: materials science, crystallography
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 4
    Publication Date: 2019-03-01
    Description: Prior to the Mars Atmosphere and Volatile Evolution mission, the only information on the composition of the Martian ionosphere came from the Viking Retarding Potential Analyzer data, revealing the presence of substantial ion outflow on the dayside of Mars. Extensive measurements made by the Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer allow us to examine the morphology of the Martian ionosphere not only in unprecedented detail but also on both the dayside and the nightside of the planet. Above 300 km, various ionospheric species present a roughly constant density scale height around 100 km on the dayside and 180 km on the nightside. An evaluation of the ion force balance, appropriate for regions with near-horizontal magnetic field lines, suggests the presence of supersonic ion outflow predominantly driven by the ambient magnetic pressure, with characteristic dayside and nightside flow velocities of 4 and 20 km/s, respectively, both referred to an altitude of 500 km. The corresponding total ion outflow rates are estimated to be 5 × 1025 s−1 on the dayside and 1 × 1025 s−1 on the nightside. The data also indicate a prominent variation with magnetic field orientation in that the ion distribution over regions with near-vertical field lines tends to be more extended on the dayside but more concentrated on the nightside, as compared to regions with near-horizontal field lines. These observations should have important implications on the pattern of ion dynamics in the vicinity of Mars.
    Print ISSN: 2169-9097
    Electronic ISSN: 2169-9100
    Topics: Geosciences , Physics
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  • 5
    Publication Date: 2019-07-19
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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