From cellulosic waste to nanocomposites. Part 2: synthesis and characterization of polyurethane/cellulose nanocomposites

New polyurethane (PU)-based nanocomposites were synthesized through two-step in situ polymerization by incorporating low loading levels of spherical cellulose nanoparticles (CNs). Structural, mechanical, thermal, and morphological characterization of the nanocomposites was done with infrared spectroscopy, X-ray diffraction, tensile test, dynamic mechanical thermal analysis, thermogravimetry, differential scanning calorimetry, and field emission scanning electron microscopy. The results showed with incorporation of CNs there was no significant change in the structure of PU. However, the addition of 1 % CNs into PU increased the modulus nearly 42 % and tensile strength by 112 %. On the contrary, elongation at break decreased with increasing nanoparticles contents, but the nanocomposites maintained an elongation of greater than 800 %, which was still a large elongation. The thermal stability of PU enhanced with increasing the small amounts of nanoparticles. Also, incorporating of the CNs improved the phase separation between the soft and hard domains which led to an upward shift in melting temperatures and enthalpy of crystalline phase melting. These results were very encouraging in terms of using CNs as an inexpensive nanofiller and improving the mechanical and thermal properties of PU without using solvents in nanocomposite preparation.     

Adsorption and kinetic performance of Cs+, Co2+, and Ce4+ radionuclides on zirconium vanadate as a cation exchanger

Amorphous zirconium vanadate samples with different molar ratios have been prepared under optimum conditions. The experimental parameters such as the order of mixing and mixing ratios were established. The ion-exchange powders were characterized by X-ray diffraction, IR spectroscopy, and differential thermal analysis. The materials are thermally and chemically stable. The sorption behavior of Cs⁺, Co²⁺, and Ce⁴⁺ radionuclides was studied at varied values of Zr: V molar ratio, pH, and temperature. The thermodynamic equilibrium constants and the values of ΔG ₀, ΔH ₀, and ΔS ₀ for the exchange of Cs⁺, Co²⁺ and Ce⁴⁺ radionuclides at Zr: V = 1: 6 were calculated from the exchange isotherms. At Zr: V = 1: 6, the capability of the material to sorb Cs⁺, Co²⁺, and Ce⁴⁺ ions is the highest. The process kinetics can be descirbed by first- or second-order equations.     

Numerical simulation of mixing process in T-shaped and DT-shaped micromixers

Recently, numerous studies have been done on the micro- and nano-scale equipment because of their importance and wide range of application. Micromixers are among the equipment in which two or more fluids are mixed and have applications in the processes, such as chemical synthesis. In this research, a numerical investigation using finite volume approach is done on mixing two incompressible fluids in 3D mixers with T- and double-T-(DT) shaped geometries in the range of Reynolds numbers 75–400. One of the important parameters for the quantitative analysis of the mixing performance of micromixers is the mixing index. So, the effects of different geometries, Reynolds number and channel length on this parameter are studied. The results show that, at different Reynolds numbers, the mixing index of fluids in the DT-shaped channel with 90° is less than the corresponding one in T-shaped mixers because changing the flow regime occurs at higher Reynolds numbers in the DT-shaped channels. The amount of mixing index increases by decreasing the angle of branches in the DT-shaped channel. It is observed that the mixing index of fluids increases along the channel, which tends to a constant value far away from the inlet.     

A Step-Down Technique to Calibrate AC Current Down to 10?μA Using a Precision 10?mA Current Shunt

This paper describes a calibration procedure for AC current measurements at 1?mA, 100 ??A and 10???A using a NIST-calibrated 10?mA current shunt as a reference standard. The procedure involves a step-down technique using the reference transfer standards (RTS) as a precision current divider. The RTS is used at values of 370???, 3.3 and 30?k?? to provide the intended currents. Uncertainty calculations are estimated for calibrating the AC current of 10?mA, 1?mA, 100 ??A and 10???A at 55?Hz and 1?kHz. The expanded uncertainties are around the values of 37 nA and 1?nA for the ranges of 1?mA?C10???A respectively.     

Room Temperature Radiolytic Synthesized Cu@CuAlO2-Al2O3 Nanoparticles

Colloidal Cu@CuAlO₂-Al₂O₃ bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP) and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a ⁶⁰Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO₂-Al₂O₃ nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD) showed that Cu@CuAlO₂-Al₂O₃ nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation.     

Selective Ozonolysis of Cis-Crotamiton: Free Catalyzed Oxidative Synthesis of N-ethyl-N-(o-tolyl)formamide as a New Compound

A novel method for the synthesis of a N-ethyl-N-(o-tolyl)formamide was described which involves ozonolysis of a cis-crotamiton. The reaction proceeds via ozone attack on the enolic double bond, cleavage, and aldehyde formation through the free hydroxyl group. The present study establishes the conditions for selective ozonolysis of cis-crotamiton, leading to N-ethyl-N-(o-tolyl)formamide 2 (55.7%). The N-ethyl-N-(o-tolyl)formamide was characterized by spectroscopical techniques.