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可以通过简单地控制乙酸浓度的方法,在相似的水热合成条件下合成2种同一家族的金属有机框架材料(MOFs):MIL-88B(Cr)和MIL-101(Cr)。在相对较低的乙酸浓度下,可以得到平均粒径为100 nm的MIL-101(Cr),并拥有很高的BET比表面积(3543 m^2·g^-1)。而在相对较高的乙酸浓度下,则可得到另一种具有“呼吸”特性结构的MOF——MIL-88B(Cr)。利用粉末X射线衍射、扫描电镜、N2吸附-脱附分析、热重分析等对它们的结构、形貌、孔隙率等性质做了详细的分析。 相似文献
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The precise spectrum of electrons and positrons at high energies plays an important role in understanding their origin.DArk Matter Particle Explorer has reported their first measurement of the e+e-spectrum from 25 GeV to4.6 TeV.This spectrum reveals a tentative peak at ~1.4 TeV,which requires a nearby source of e+e-.In this work,we study the properties of a large nearby dark matter subhalo that accouns for this spectral peak,such as its mass and distance from Earth,for different concentration models.We compare spectra of the sources in 3 FGL with that from DM annihilation in the subhalo,and find ten candidates that have comparable gamma-ray spectra.However,according to the N-body simulation,the probability that such a large subhalo is close enough to Earth is less than 0.1%. 相似文献
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Recently, many new dwarf spheroidal satellites(dSphs) have been discovered by the Dark Energy Survey(DES). These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter(DM) annihilation.However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II(DES J0335.6-5403) as a spatially extended source, and find that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section. 相似文献
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