A new rare-earth polyborate, trisodium europium octaborate, Na3EuB8O15, was prepared using the high-temperature molten-salt method and structurally determined by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic space group P\overline{1} and contains a one-dimensional [B8O15]∞ tube structure that is constructed from BO3 and BO4 polyhedra. The Eu3+ and Na+ cations reside in this structure to ensure cohesion and neutrality. The excitation spectra, emission spectra, decay time and Commission Internationale de l'Éclairage (CIE) chromaticity index of Na3EuB8O15 were studied. Under near-UV light excitation (393 nm), the polyborate shows an intense red emission, which mainly originates from the highest intensities of the 5D0→7F1 and 5D0→7F2 transitions.
Two different extraction methods, microwave extraction and traditional soxhlet extraction, were used to evaluate the optimal extraction process of coal for direct carbon fuel cells through enrichment efficiency of the organic components and extraction time required under the same extraction rate. The experimental results showed that the extraction rate of microwave extraction was 9.7368% when adopted tectonic coal of 8th coal mine as sample, selected 80mL pyridine as solvent, set 95W as microwave power and 3min as extraction time. Under the same extraction rate condition, soxhlet extraction time is 35.73h, and the extraction efficiency of the microwave extraction was 714.6 times that of the soxhlet extraction. The microwave extraction was a simplify and promising working for coal, which was used as raw fuel for direct carbon fuel cells, with fast extraction speed, large sample capacity, energy saving and environmental friendly.
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