Determination and correlation of solubility and solution thermodynamics of saccharin in different pure solvents

The solubility of saccharin in seven pure solvents, including methanol, ethanol, n-propanol, isopropanol, isobutanol, ethyl acetate and acetone, was determined from 278.15 K to 323.15 K by using a gravimetric method at atmospheric pressure. The solubility of saccharin is positively related to temperature in all selected solvents. The cooperation effect between polarity and interaction bonding was revealed by the molecular simulation study to give the explanation for the sequence of solubility in various solvents. Besides, the experimental solubility data was correlated by the modified Apelblat equation lambda h equation, Wilson model and NRTL model. The results indicate that all the models could give satisfactory correlation results, whereas the modified Apelblat model shows the best fitting result. Furthermore, the thermodynamic properties of the dissolution process of saccharin in the appointed solvents, including the Gibbs energy, enthalpy and entropy of dissolution, were also calculated and discussed according to the Wilson model and the result turns out that the dissolution process of saccharin is endothermic. (C) 2019 Elsevier Ltd

Rational Design of Superior Microwave Shielding Composites Employing Synergy of Encapsulating Character of Alginate Hydrogels and Task-Specific Components (Ni NPs, Fe₃O₄/CNTs)

Three-dimensional (3D) porous magnetic carbonaceous bead-like (MCB) composites (SA-Ni-(Fe₃O₄/CNTs)-<i>X</i>; SA stands for sodium alginate, CNTs means carbon nanotubes and <i>X</i> means Fe₃O₄/CNTs percentage) have been successfully fabricated through a facile one-step encapsulation process, followed by carbonization at 600 °C in nitrogen atmosphere. These magnetic nickel nanocrystals and Fe₃O₄/CNTs were uniformly dispersed into the entire porous carbon matrix without aggregation; and various techniques like scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and vector network analyzer (VNA) were conducted to demonstrate the morphology, structure, chemical content and electromagnetic parameters of the SA-Ni-(Fe₃O₄/CNTs)-<i>X</i> composites. The effect of the Fe₃O₄/CNTs molar percentage on the electromagnetic parameters and electromagnetic wave absorbing properties of the SA-Ni-(Fe₃O₄/CNTs)-<i>X</i> composites were investigated in the frequency range of 2–18 GHz. It was proven that the composites would be superior lightweight microwave absorbers when the Fe₃O₄/CNTs molar percentages were relatively high. When a 25% Fe₃O₄/CNTs molar percentage was used, it could lead to a maximum reflection loss (RL) of −32 dB at 10.8 GHz even with a thickness of 2 mm; the effective microwave absorption bandwidth (RL < −10) reached 3.2 GHz (from 9.3 to 12.5 GHz). The superior electromagnetic wave absorbing properties could be assigned to the high attenuation, Debye relaxation, electric polarization, interfacial polarization and high conductivity of the task-specific components. It is thus considered that the newly synthesized SA-Ni-(Fe₃O₄/CNTs)-<i>X</i> composite could be a promising candidate for novel types of lightweight and high-performance electromagnetic wave absorbing materials with great potentiality in practice