Activated carbons are prepared from raw hemp stem (hurd and bast) via hydrothermal processing and chemical activation. Both hemp bast and hemp hurd are converted into activated carbons of low-dimensional structures under certain experimental conditions. The experimental results show that hemp hurd is a better precursor than hemp bast for the preparation of activated carbons. The activated carbons are used to construct the electrodes of supercapacitor cells. The electrochemical performance of the activated carbons used in the supercapacitor cells is dependent on hydrothermal processing conditions and the mass ratio of KOH/biochar in the chemical activation. Excellent electrochemical performance metrics are achieved, including a specific capacitance of 160 F/g, and a high energy density of 19.8 Wh/kg at a power density of 21 kW/kg. Both the specific capacitance and capacitance retention increase with the increase of surface area and mesopore fraction. A simple relationship between the specific area capacitance and the fraction of micropores is proposed, via the rule of mixtures, and is supported by the experimental results. This relationship reveals the effect of the distribution of pore sizes on the specific area capacitance of electrochemical double layer capacitors.

The absence of mixing between Y3+ and Cu2+ results in a more idealized Kagomé lattice in YCu3(OH)6Cl3 compared to hebertsmithite and kapellasite.

One of the key questions concerning frustrated lattices that has lately emerged is the role of disorder in inducing spin-liquid-like properties. In this context, the quantum kagome antiferromagnets YCu3(OH)6Cl3, which has been recently reported as the first geometrically perfect realization of the kagome lattice with negligible magnetic/non-magnetic intersite mixing and a possible quantumspin-liquid ground state, is of particular interest. However, contrary to previous conjectures, here we show clear evidence of bulk magnetic ordering in this compound below TN = 15 K by combining bulk magnetization and heat capacity measurements, and local-probe muon spin relaxation measurements. The magnetic ordering in this material is rather unconventional in several respects. Firstly, a crossover regime where the ordered state coexists with the paramagnetic state extends down to TN /3 and, secondly, the fluctuation crossover is shifted far below TN . Moreover, persistent spin dynamics that is observed at temperatures as low as T /TN = 1/300 could be a sign of emergent excitations of correlated spin-loops or, alternatively, a sign of fragmentation of each magnetic moment into an ordered and a fluctuating part. arXiv:1904.02878v2 [cond-mat.str-el] 1 Jul 2019

Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129 I and 131 I) in contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO 3 −) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO 3 concentrations (0.002; 0.004; 0.008 M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO 3 − is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I 5+ ion of