Display omitted
•Earth abundant CuI catalyzes the Henkel reaction.•Yield and selectivity are improved compared to previous catalyst, CdI2.•Benzoate is converted into benzene and terephthalic ...acid.•Furan carboxylate is converted into furan and 2,5-furan dicarboxylic acid (FDCA)
Copper(I) iodide catalyzes the disproportionation of aromatic and heteroaromatic carboxylic acids to give dicarboxylic acids. Potassium furoate heated to 280 – 300 °C in the presence of 10 mol % CuI under carbon dioxide (40 bar) forms dipotassium 2,5-furandicarboxylate (2,5-FDCK), which is isolated as pure 2,5-dicarboxylic acid (2,5-FDCA) in up to 75 % isolated yield and in excellent selectivity over the regioisomeric 2,4-furandicarboxylate (92 % selectivity). Starting materials are recovered in experiments lacking CuI or with pressurized N2 replacing CO2, whereas high conversion and low yields of 2,5-FDCA are obtained with moderate CO2 pressures, suggesting several roles for carbon dioxide in the transformation. Similarly, potassium benzoate heated to 320 – 350 °C in the presence of 10 mol % CuI under carbon dioxide (40 bar) produces terephthalic acid after workup in up to 60 % yield.
In this work, CoFe2O4 magnetic nanoparticles (MNPs) were synthesized by an eco-friendly co-precipitation method. The effect of Triethylene glycol (TEG) coating on the structural, magnetic and ...magnetothermal properties of MNPs was investigated. The formation of crystalline MNPs with a cubic spinel structure and the single phase state was confirmed by the X-ray diffraction (XRD) and infrared spectra (FT-IR) techniques. The spherical morphology and aggregation of the MNPs, as a sign of the presence of interparticle interactions, were revealed by the field emission scanning electron microscopy imaging. A remarkable result has been found by the SQUID and Mössbauer spectroscopy measurements revealing that the polymer coating increases the saturation magnetization through the control of the metal-oxygen-metal bonds and reduction of the spin disorder at the nanoparticle surface. Furthermore, the Henkel plots indicated a dominant role of the dipole-dipole over exchange magnetic interactions in the samples which affected the heating efficiency of the ferrofluids measured under different AC magnetic fields (2.2, 2.7, and 3.3 mT) with a frequency of 92 kHz showing a linear dependence of the thermal efficiency with the AC field amplitude. It was shown that TEG coating increases the heating efficiency of the CoFe2O4 MNPs, which was attributed to an increase in saturation magnetization and a decrease in the strength of the magnetic interactions between the coated nanoparticles.
The present study investigated the preparation of 2,5‐furandicarboxylic acid (FDCA) via the Henkel reaction between furoic acid alkali metal salts and zinc chloride under a continuous CO2 flow at ...atmospheric pressure. The results obtained were compared with those of previous studies that used high‐pressure conditions or toxic cadmium catalysts. The pathways and rate‐determining steps of the reaction are revealed for the first time. Furthermore, the enhanced formation of FDCA through the promotion of carboxyl exchange and rearrangement during the reaction under a CO2 flow was examined. The CO2‐rich environment afforded a high FDCA yield of 86.30 %, which is the highest yield obtained to date using the Henkel reaction. The findings of this study offer economically improved conditions for large‐scale FDCA production.
The pathways and rate‐determining steps of the preparation of 2,5‐furandicarboxylic acid are identified. The approach includes CO2 flow via the Henkel reaction. The improvements include the mild operating conditions such as atmospheric condition and highest yield among the literatures.
Abstract
The propagation of H-polarized electromagnetic (EM) waves in polymeric (PEI)-chalcogenide (As
2
Se
3
) photonic materials (PCCPM) has been theoretically optimized and investigated in the ...current work. We used the Transfer Matrix Technique (TMT) and Hankel Realism (HR) in columnar coordinates to show numerical findings for the unit columnar junction and columnar slab for both polymeric (low refractive index) and chalcogenide (high refractive index) materials composed at least loss wavelength window (632.8 nm). The optical transmittance with wavelength for both materials for the cylindrical unitary slab displays oscillating and non-oscillating signatures, indicating that the starting radius has a significant impact on the transmittance at a constant slab width. The oscillatory transmittance becomes squizzing when the starting radius is increased. Furthermore, for smaller modal numbers, optical transmittance is an oscillatory function of slab thickness, and for (m=4), it becomes minimum and flat. These scientific breakthroughs pave the door for a variety of photonic devices and sensor applications.
•Simulations of δM(H) plots of nanocrystalline hard magnetic alloys were performed.•Intergrain exchange interaction constant was estimated from δM(H) of Nd-FeCo-B alloy.•Effect of grain size ...dispersion on δM(H) of nanocrystalline alloys was considered.
Magnetic properties of nanocrystalline hard magnetic alloys such as coercivity and maximum energy product are strongly depended on microstructure and interactions between grains. There are a lot of advanced experimental techniques for microstructure characterization but the analysis of intergrain interactions is still challenging. One of the wide-spread methods for doing that is plotting δM(H). This work is aimed to elucidate how different factors effect δM(H) plots for high-anisotropy nanocrystalline alloys. Specifically, changes of δM(H) plots caused by both intergrain exchange and magnetostatic interactions, grain size dispersion, and demagnetization factor are analyzed systematically using macrospin-based simulations. It is demonstrated that all these factors should be considered for a reliable evaluation of exchange coupling in alloys. A concept of such analysis is presented and applied to rapidly quenched Nd-FeCo-B alloy.
Exchange-spring systems offer various technological applications. In this study, BaFe12O19-Ni0.5Zn0.5Fe2O4 nanocomposite magnets with single-step hysteresis loops were synthesized through a simple ...combustion method. Their composition, microstructure, and magnetic properties were also investigated. It was found that the magnetic properties and the mechanisms governing the magnetization of these nanocomposite magnets are strongly influenced by the calcination temperature as well as the molar ratios of the hard and soft phases. The exchange-coupling between the hard and soft magnetic phases was confirmed by the study of Henkel plots and the variation in the magnetic properties could also be explained by the dominant role of exchange and dipolar interactions in the nanocomposites. The study provides a simple but efficient route for the fabrication of exchange-coupled nanocomposite magnets based on ferrites having controllable magnetic properties.
Recent advances in the field of magnetic materials emphasize that the development of new and useful magnetic nanoparticles (NPs) requires an accurate and fundamental understanding of their collective ...magnetic behavior. Studies show that the magnetic properties are strongly affected by the magnetic anisotropy of NPs and by interparticle interactions that are the result of the collective magnetic behavior of NPs. Here we study these effects in more detail. For this purpose, we prepared Co
Fe
O
NPs, with
= 0-1 in steps of 0.2, from soft magnetic (Fe
O
) to hard magnetic (CoFe
O
) ferrite, with a significant variation of the magnetic anisotropy. The phase purity and the formation of crystalline NPs with a spinel structure were confirmed through Rietveld refinement. The effect of Co doping on structure, morphology and magnetic properties of Co
Fe
O
samples was investigated. In particular, we examined the interparticle interactions in the samples by δ
graphs and Henkel plots that have not been reported before in literature. Finally, we studied the hyperthermia properties and observed that the heat efficiency of soft Fe
O
is about 4 times larger than that of hard CoFe
O
ferrite, which was attributed to the high coercive field of samples compared with the external field amplitude.
Sensory investigations of the functional textiles could be an alternative for the quality inspection and control of the products. The purpose of this research is to use subjective evaluation ...technique for assessing the tactile comfort of some functional textile fabrics based on AATCC Evaluation procedure 5-2011. Blind subjective evaluations and visual subjective evaluations were performed for sensory investigation. Ten fabric-skin-contact and comfort-related sensory properties were used to evaluate the handle of the functional textile fabrics. The reliability of the sensorial data obtained by subjective tests was evaluated using statistical data analysis techniques. A minimum and maximum consensus distances recorded were 0.58 and 1.61, respectively, using a descriptive sensory panel analysis and proves the consistency and similar sensorial perception between panelists. The Pearson correlation coefficient between panelists was up to 96% and hence a strong agreement between the panelist’s judgment. The results allowed to consider the subjective evaluation using a panel of experts could be validated in the case of functional fabrics. For functional textiles, additional visual subjective evaluation should be considered to have a similar human perception in addition to blind subjective evaluation.
Co/CoFe2O4 nanoparticles with the mean size of 8.8, 10.8 and 16.9nm were prepared by thermal decomposition of metal salts in the presence of citric acid. The X-ray diffraction patterns and Rietveld ...refinements confirmed coexistence of Co-ferrite and metallic cobalt phases in the nano-powders. Scanning electron microscope images showed an increase in particles aggregates mean diameter with increasing the annealing temperature. Magnetic hysteresis loops showed a demagnetization jump at low fields, which was attributed to different reversal fields of ferrite and the cobalt phases. Field-dependent behavior of maximum magnetization (Mmax), remanence (Mr), squareness (S) and coercivity (Hc) were studied through minor loops measurements. The calculated S value of the loops showed a maximum, between anisotropy and coercive fields. A sharp increase in Hc of larger particles was observed with increasing the applied field when compared to smaller particles. Henkel plots showed that the samples are interacting. Negative deviation of Henkel plots from linear behavior and negative δm plots revealed the dominant role of dipole–dipole interactions in the nano-aggregates.
PDF
