Synthesis and characterization of novel Schiff‐base polyamides from copper/benzil bisthiosemicarbazone complexes

A new copper‐containing Schiff‐base diamine, benzil bis(thiosemicarbazonato)copper(II) (CuLH₄), was synthesized in two steps from benzil bisthiosemicarbazone (LH₆). The ligand LH₆ and the complex CuLH₄ were characterized with Fourier transform infrared spectroscopy, ¹H‐NMR, and elemental analysis. CuLH₄ was used to prepare novel polyamides. The low‐temperature solution polycondensation of the complex CuLH₄ with various aromatic and aliphatic diacid chlorides afforded copper‐containing Schiff‐base polyamides with inherent viscosities of 0.25–0.36 dL/g in N,N‐dimethylformamide (DMF) and 0.75 dL/g in H₂SO₄ at 25°C. The polyamides were generally soluble in a wide range of solvents, such as DMF, N,N‐dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, ethyl acetate, tetrachloroethane, hexamethylene phosphoramide, N‐methylpyrrolidone, and pyridine. Thermal analysis showed that these polyamides were practically amorphous, decomposed above 270°C, and exhibited 50% weight loss at and above 400°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of high performance polyamides utilizing copper‐catalyzed amidation of a dibromoarene with different diamides

A series of diphenylquinoxaline‐containing polyamides were prepared from the condensation polymerization of 2,3‐bis (4‐bromophenyl) quinoxaline (DBQ) with various primary and secondary diamides via copper‐catalyzed amidation reaction. The polyamides were characterized with FTIR, NMR, GPC, differential scanning calorimeter, and thermo gravimetric analysis, and their solubility and viscosity were measured. The polyamides synthesized here are amorphous and showed relatively good solubility in polar aprotic solvents and demonstrate the ability to form brownish hard films by solvent casting; their inherent viscosities ranged from 49 to 55 mL/g. The average molecular weights of polyamides were in the range of M_w = 11,950–5592 g/mol (MWD = 1.21–1.87). These polyamides had relatively high thermal stability with T_g values up to 276°C, 10% weight loss temperatures (T_10%) in the range of 364–476°C, and char yields at 600°C in N₂ up to 72%. They also exhibit emission in the solid state and in dilute (0.2 g/dL) DMAc solution at 425–484 nm with photoluminescence quantum (?_f) yields in the range of 14–23%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Compositional dependence of thermal stability, glass-forming ability and fragility index in some Se-Te-Sn glasses

Non-isothermal DSC thermograms were obtained for the ternary Se₉₀Te_10−xSn_x (x = 2, 4, 6 and 8) chalcogenide glasses in order to determine the melting temperature T_m, glass transition temperature T_g, onset T_c and peak T_p temperatures of crystallization. These temperatures were utilized to investigate the thermal stability through the calculations of temperature difference (T_c − T_g), the glass transition activation energy E_t, the parameter S and the average value of crystallization rate factor 〈K_p〉. In addition, the glass forming ability was estimated by the criteria of reduced glass transition temperature, T_rg and Hruby parameter H_R. The fragility index m for the present glasses was determined in order to see whether these materials are obtained from strong or fragile glass-forming liquid. Results reveal that, both thermal stability and glass forming ability exhibit a maximum at x = 4 at.% of Sn. Meanwhile, the prepared glasses were obtained from strong glass-forming liquid as evident from the fragility index calculations. The compositional dependence of the above parameters was discussed on the basis of Philips and Thorpe topological model and the critical composition occurs at an average coordination number 〈r〉 = 2.16 but not 2.40. This is due to the formation of iono-covallent bonds when the glass doped with heavy elements like Sn.     

Dye removal from colored‐textile wastewater using chitosan‐PPI dendrimer hybrid as a biopolymer: Optimization,kinetic, and isotherm studies

Preparation of a biopolymer chitosan‐polypropylene imine (CS‐PPI) as a biocompatible adsorbent and its reactive textile dyes removal potential were performed. Chemical specifications of CS‐PPI were determined using Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR. The surface morphology of the CS‐PPI surface was characterized by scanning electron microscopy. Results confirmed that the linkages between the NH₂ groups of PPI dendrimer and carboxylic groups of modified Chitosan were accomplished chemically. Two textile reactive dyes, reactive black 5 (RB5) and reactive red 198 (RR198), were used as model compounds. A response surface methodology was applied to estimate the simple and combined effects of the operating variables, including pH, dye concentration, time contact, and temperature. Under the optimal values of process parameters, the dye removal performance of 97 and 99% was achieved for RB5 and RR198, respectively. Furthermore, the isotherm and kinetic models of dyes adsorption were performed. Adsorption data represented that both examined dye followed the Langmuir isotherm. The adsorption kinetics of both reactive dyes were satisfied by pseudo‐second order equation. Based on this study, CS‐PPI due to having high adsorption capacity (6250 mg/g for RB5 and 5882.35 mg/g for RR198), biocompatibility and ecofriendly properties might be a suitable adsorbent for removal of reactive dyes from colored solutions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of a biopolymer chitosan-poly(propylene)imine dendrimer hybrid as an antimicrobial agent on the wool fabrics

In this research, chitosan-poly(propylene)imine dendrimer hybrid (CS-PPI) was applied to wool fabrics; and weight gain and antibacterial properties of the grafted wool fabric by CS-PPI were investigated. A response surface methodology employed for optimization of the important factors such as pH, processing time, and CS-PPI and cross-linking agent (CA) concentrations. The physical properties showed sensible changes regardless of weight gain. The maximum weight gain was obtained when the wool fabrics were treated with pH 5, processing time 24 h, CS-PPI 20 %(owf) and CA 5 % over weight of fiber (owf). Scanning electron microscopy analysis showed the presence of foreign particles determinedly fixed to the surface of the wool fabric. Fourier transform infrared spectroscopy and differential scanning colorimetry revealed the grafting of CS-PPI onto wool fabric by forming novel chemical bonds between the wool and CS-PPI molecules. The treated wool fabrics showed broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria. Antimicrobial activities of the treated wool by CS-PPI at a concentration of 20 % over weight of fiber (owf) demonstrated 100 % bacterial growth inhibition, which was preserved more than 84 % even after being washed in 12 various conditions repeatedly. The grafted wool fabrics have antibacterial potential due to the antibacterial property of CS-PPI molecules. The mechanism of CS-PPI grafting onto wool fabric using CA was proposed. The findings of this study support the potential production of the new environmentally friendly textile fibers.     

Modeling Growth Rate and Assessing Aflatoxins Production by Aspergillus flavus as a Function of Water Activity and Temperature on Polished and Brown Rice

Abstract: The aim of this study was to model the radial growth rate and to assess aflatoxin production by Aspergillus flavus as a function of water activity (a_w 0.82 to 0.92) and temperature (12 to 42 °C) on polished and brown rice. The growth of the fungi, expressed as colony diameter (mm) was measured daily, and the aflatoxins were analyzed using HPLC with a fluorescence detector. The growth rates were estimated using the primary model of Baranyi, which describes the change in colony radius as a function of time. Total of 2 secondary models were used to describe the combined effects of a_w and temperature on the growth rates. The models were validated using independent experimental data. Linear Arrhenius–Davey model proved to be the best predictor of A. flavus growth rates on polished and brown rice followed by polynomial model. The estimated optimal growth temperature was around 30 °C. A. flavus growth and aflatoxins were not detected at 0.82 a_w on polished rice while growth and aflatoxins were detected at this a_w between 25 and 35 °C on brown rice. The highest amounts of toxins were formed at the highest a_w values (0.90 to 0.92) at a temperature of 20 °C after 21 d of incubation on both types of rice. Nevertheless, the consistencies of toxin production within a wider range of a_w values occurred between 25 to 30 °C. Brown rice seems to support A. flavus growth and aflatoxin production more than the polished rice. Practical Application: The developed models can be used to estimate to what extent the change in grain ecosystem conditions affect the storage stability and safety of grains without the need for running long‐standing storage study. By monitoring the intergranular relative humidity and temperature at different locations in the storage facility and inputting these data into the models, it is directly possible to assess either the conditions are conductive for the growth of A. flavus or aflatoxin production.     

One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex

[NiCl₂(C₁₄H₁₂N₂)(H₂O)] complex has been synthesized from nickel chloride hexahydrate (NiCl₂·6H₂O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM).     

Optimal characteristics and heat transfer efficiency of SiO2/water nanofluid for application of energy devices: A comprehensive study

In a comprehensive study, the thermal conductivity, dynamic viscosity, and the rheological behavior of a SiO₂/water nanofluid are investigated experimentally at the temperatures, solid concentrations, and the shear rates of 25°C to 50°C, 0% to 1.5%, and 400 to 1400(s^?1), respectively. The Response Surface Methodology (RSM) is utilized to obtain regression models for the thermal conductivity and the dynamic viscosity. Subsequently, the sensitivity of the aforementioned models to 10% changes in the temperature, and the nanofluid concentration is analyzed. Afterward, Nondominated Sorting Genetic Algorithm II (NSGA‐II) is utilized to find the maximum thermal conductivity and the minimum viscosity. The nondominated optimal points are presented through a fitted correlation on a Pareto front to make the results more practical. The measurements of the investigated nanofluid could be summarized as a paper of a handbook. The workability of the investigated nanofluid is also examined in both laminar and turbulent flow regimes through analysis of the heat transfer merit graphs. To this end, the ratio of the dynamic viscosity enhancement to the thermal conductivity enhancement and the Mouromtseff number are chosen as two criteria of the laminar and turbulent flow regimes, respectively. Finally, the results are compared with those for SiO₂/glycerin and SiO₂/ethylene glycol nanofluids to check the workability in different base fluids. From a thermal‐efficiency point of view, the SiO₂/water nanofluid is not suggested for use in both laminar and turbulent pipe flows, except in temperatures higher than 30°C and volume concentrations lower than 1% for the case of laminar flow. This is because the favorable heat transfer enhancement of the nanofluid is more than the unfavorable increase of the pumping power. From the rheological point of view, though, a SiO₂/water nanofluid would be a good choice in lubricating moving surfaces for both laminar and turbulent flow regimes. It is found that in higher nanofluid concentrations, the thermal conductivity of a SiO₂/water nanofluid is highly influenced by temperature. Moreover, adding nanoparticles at temperatures of 35°C to 40°C would have the highest increasing effect on the thermal conductivity. It is also revealed that increasing the temperature does not significantly affect the viscosity when 1% SiO₂ nanoparticles are suspended within the water.     

Optimizing Radiographic Sensitivity in the In-Service Testing of Pipes

Russian Journal of Nondestructive Testing - In the in-service radiographic testing of water-filled pipes, the interaction of radiation with water diminishes the quality of the transmitted radiation...     

Synthesis of a new self-supported Mgy(CuxNi0.6-xMn0.4)1-yFe2O4 oxygen carrier for chemical looping steam methane reforming process

Novel self-supported Mg_y(Cu_xNi_0.6-xMn_0.4)_1-yFe₂O₄ with (y = 0, 0.05, 0.1, 0.15, and x = 0, 0.15, 0.3, 0.45, 0.6) oxygen carriers (OCs) are synthesized through the co-precipitation method. The synthesized OCs’ properties are characterized by X-ray powder diffraction (XRD), Raman spectra, transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and Thermogravimetric Analysis (TGA). The synthesized OCs are assessed in Chemical Looping Steam Methane Reforming (CL-SMR) process subject to different mesh sizes, reaction temperatures, Steam/Carbon (S/C) molar ratios, Mg concentrations, and Cu and Ni concentrations. The characterization of the OCs and process results indicate the contributive effect of Mg incorporation on the Cu_xNi_0.6-xMn_0.4Fe₂O₄ support structure. The redox results reveal that Mg_0.1(Cu_0.3Ni_0.3Mn_0.4)_0.9Fe₂O₄ OC is of the highest activity, even at low reduction temperatures. This OC exhibits the highest activity and stability with lowest coke deposition during 24 redox cycles at 650 °C and S/C = 2.5. The highest CH₄ conversion of about 99.4% and H₂ yield of about 84.4% are obtained.