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221.
Cristian-Dragos Varganici Oana Ursache Constantin Gaina Viorica Gaina Bogdan C. Simionescu 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1561-1570
New polyurethane chemically crosslinked networks containing silica were synthesized by both Diels–Alder polymerization and Michael addition reaction. Structural characterization of the products was evidenced by proton nuclear magnetic resonance and attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy techniques. Differential scanning calorimetry was used to demonstrate the thermally remendable character of the materials obtained through Diels–Alder polymerization. The influence of increasing silica content on the glass transition temperatures was studied. It was observed that the glass transition temperatures increased with increasing silica content. Absolute heat capacities and crosslinking densities were determined for the thermoreversible materials. A comparison between materials obtained through Diels–Alder process and Michael addition method was studied. A kinetic study was conducted via an isoconversional method. Morphological studies were conducted by atomic force microscopy technique. 相似文献
222.
Periodica Mathematica Hungarica - In this paper we consider individual stability for linear skew-product semiflows over semiflows by using the standard Perron’s method. To our knowledge, in... 相似文献
223.
Monica Dan Adriana Vulcu Sebastian A. Porav Cristian Leostean Gheorghe Borodi Oana Cadar Camelia Berghian-Grosan 《Molecules (Basel, Switzerland)》2021,26(13)
Four N-doped graphene materials with a nitrogen content ranging from 8.34 to 13.1 wt.% are prepared by the ball milling method. This method represents an eco-friendly mechanochemical process that can be easily adapted for industrial-scale productivity and allows both the exfoliation of graphite and the synthesis of large quantities of functionalized graphene. These materials are characterized by transmission and scanning electron microscopy, thermogravimetry measurements, X-ray powder diffraction, X-ray photoelectron and Raman spectroscopy, and then, are tested towards the oxygen reduction reaction by cyclic voltammetry and rotating disk electrode methods. Their responses towards ORR are analysed in correlation with their properties and use for the best ORR catalyst identification. However, even though the mechanochemical procedure and the characterization techniques are clean and green methods (i.e., water is the only solvent used for these syntheses and investigations), they are time consuming and, generally, a low number of materials can be prepared, characterized and tested. In order to eliminate some of these limitations, the use of regression learner and reverse engineering methods are proposed for facilitating the optimization of the synthesis conditions and the materials’ design. Thus, the machine learning algorithms are applied to data containing the synthesis parameters, the results obtained from different characterization techniques and the materials response towards ORR to quickly provide predictions that allow the best synthesis conditions or the best electrocatalysts’ identification. 相似文献
224.
Alina Tirsoaga Diana Visinescu Bogdan Jurca Adelina Ianculescu Oana Carp 《Journal of nanoparticle research》2011,13(12):6397-6408
Nanosized metal aluminates, MAl2O4 (M = Ni, Co), have been prepared following a nonpolluting, low temperature, and self-sustaining starch single-fuel combustion
synthesis. The mixed fuel-coordinating actions of starch have given rise to an intermediary precursor which afforded monodisperse
metal aluminate nanoparticles. The thermal analysis of the [M(II), Al(III)]-starch precursors indicates a similar thermochemical
reactivity for the two compounds, displaying a sequence of well-defined decomposition stages associated with three endothermic
effects and three/four (nickel/cobalt) exothermic ones. The XRD data confirm the formation of spinelic phase and a continuous
growth of particle sizes with the increase of calcination temperatures. The mechanisms proposed for the formation of metal
aluminates essentially consist in a combination of solid-state reactions of amorphous NiO/Co3O4 and Al2O3 simple oxides. The evaluation criterion of Ni(II) cations into the spinelic lattice is original and is based on the distinct
occupancy degree of tetrahedral and octahedral sites in NiAl2O4 and γ-Al2O3. TEM/HRTEM investigations performed on the cobalt(II) and nickel(II) aluminate oxide powders resulted after calcination at
800 and 900 °C, respectively, for 1 h show the formation of irregular and isolated plate-like particles for Co(II)-based spinelic
oxides (the average particle size is 16.6 nm) and submicron aggregates of small, bimodal, and almost uniform (as shape and
size) of NiAl2O4 mixed oxide (the mean particle size is 33.6 nm). The NIR–UV–Vis spectra for the resulted MAl2O4 (M = Co, Ni) mixed oxides reveal a massive presence of tetrahedral divalent cations both for short- and long-time calcined
samples. NiO impurities are detected using FTIR and electronic spectra for all NiAl2O4 samples. 相似文献
225.