Hydrogen storage thermodynamic and kinetic characteristics of PrMg12-type alloys synthesized by mechanical milling

To improve the hydrogen storage performance of PrMg12-type alloys, Ni was adopted to replace partially Mg in the alloys. The PrMgllNi＋x wt.% Ni （x=100, 200） alloys were prepared via mechanical milling. The phase structures and morphology of the experimental alloys were in vestigated by X-ray diffraction and transmission electron microscopy. The results show that increasing milling time and Ni content accelerate the formation of nanocrystalline and amorphous structure. The gaseous hydrogen storage properties of the experimental alloys were determined by differential scanning calorimetry （DSC） and Sievert apparatus. In addition, increasing milling time makes the hydrogenation rates of the alloys augment firstly and decline subsequently and the dehydrogenation rate always increases. The maximum capacity is 5. 572 wt. % for the x = 100 alloy and 5. 829 wt. % for the x = 200 alloy, respectively. The enthalpy change （ △H ）, entropy change （△S） and the dehydrogenation activation energy （Exde） markedly lower with increasing the milling time and the Ni content due to the generation of nanocrystalline and amorphous structure.

Synthesis of newly cationic surfactant based on dimethylaminopropyl amine and their silver nanoparticles:Characterization;surface activity and biological activity

The chemical structure of newly synthesized cationic surfactants based on Schiff base was confirmed using Fourier transform infrared spectroscopy,proton nuclear magnetic resonance spectroscopy,and mass spectroscopy.The synthesized surfactants were used in the synthesis of silver nanoparticles by a simple one-step method.The silver nanoparticle（AgNPs） formation was confirmed using transmission electron microscopy（TEM）,electron diffraction（SAED）,dynamic light scattering（DLS）,and energy dispersive X-ray spectroscopy（EDX）.The structure of the surfactant played an important role in the synthesis process.Increasing the hydrophobic chain length,the stability,and the amount of surfactant increased the quantity of AgNPs formed.The surface activity of the synthesized cationic surfactants was determined using surface tension measurements at three different temperatures.The synthesized surfactants showed a high tendency toward adsorption and micellization.Increasing the hydrophobic chain length of the synthesized surfactant increased its adsorption.Screening the synthesized cationic surfactants and their nano-form against bacteria and fungi showed that they are highly effective.The silver nanoparticles enhanced the biological activity of the synthesized cationic surfactants.

Adsorption of Mn^(2+) from aqueous solution using Fe and Mn oxide-coated sand

The adsorption of Mn2＋ onto immobilized Mn-oxide and Fe-oxide adsorbent such as manganese oxide-coated sand 1 （MOCS1）, manganese oxide-coated sand2 （MOCS2）, iron oxide-coated sand2 （IOCS2）, and manganese and iron oxide-coated sand （MIOCS）was investigated. The effects of pH （5.5 to 8.0） and temperature （25 to45°C） on the equilibrium capacitywere examined. Equilibrium studies showed that there is a good fitwith both Freundlich and Langmuir isotherm,which indicates surface heterogeneity and monolayer adsorption of the adsorbents. Kineticdata showed high correlationwith the pseudo second-order model,which signifies a chemisorption-controlled mechanism. The activation energies, activation parameters （ΔG＊,ΔH＊,ΔS＊）, and thermodynamic parameters （ΔG0 , ΔH0 , ΔS0 ） confirmed that adsorptionwith MIOCSwas endothermic and more spontaneous at higher temperaturewhile an opposite trendwas observed for the other adsorbents. Thermodynamic studies showed that adsorption involved formation of activated complex,where MOCS1 and MIOCS follow a physical-chemical mechanism,while MOCS2 and IOCS2 follows purely chemical mechanism.

Electrochemical behavior of praseodymium and Pr-Al intermetallics in LiCl-KCl-AlCl_3-PrCl_3 melts

The electrochemical behavior of Pr（Ⅲ） and formation process of Pr-Al intermetallics were investigated by different electrochemical methods. The reduction of Pr（Ⅲ） ion to metallic Pr is an one-step three-electrons reaction. The reversibility of Pr（Ⅲ）/Pr（0） system was evaluated by cyclic voltammograms with different scan rates. The co-reduction of Pr（Ⅲ） and Al（Ⅲ） ions formed three different Pr-Al intermetallics at electrode potentials around-1.40,-1.80,and-1.95V vs.Ag/AgCl at 723 K,respectively.Open-circuit chronopotentiometry and electromotive force（emf） measurements were carried out to estimate the relative molar Gibbs energies of Pr for the formation of different Pr-Al intermetallics in the temperature range of 723–843K.The activities of Pr in the Pr-Al intermetallic compounds were calculated.