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31.
Raluca Marinica Albu Ecaterina Avram Iuliana Stoica Silvia Ioan 《Polymer Composites》2012,33(4):573-581
The formation conditions of new quaternized polysulfones with chelating groups (methyl 3‐pyridyl ketone) (KQPSF) and the major factors influencing the retention process of copper ions were analyzed by attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, environmental scanning electron microscopy, and differential scanning calorimetry. The investigations showed that the percentage of copper ions retained by KQPSF increases by increasing both the time of immersion in a CuCl2·2H2O aqueous solution, and molarity, the maximum value being attained on immersion for 48 h, at a temperature of 60°C and a molarity of 1.5 M. It can be concluded that methyl 3‐pyridyl ketone might be used for obtaining complex polysulfone structures employed by multiple applications, including wastewater purification. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers 相似文献
32.
Luminita‐Ioana Buruiana Ecaterina Avram Adriana Popa Iuliana Stoica Silvia Ioan 《应用聚合物科学杂志》2013,129(4):1752-1762
A new quaternized polysulfone with triphenylphosphonium pendant groups was synthesized by reacting chloromethylated polysulfone with triphenylphosphine. The molecular restructurations, generated by hydrogen bonding, electrostatic interactions, and association phenomena in ternary quaternized polysulfone/N,N‐dimethylformamide (solvent)/water (nonsolvent) systems, were evaluated by rheological investigations. The polyelectrolyte effect, induced by enhanced dissociation of the ionizable groups and by mixed solvents' quality, modify the rheological functions, that is, dynamic viscosity, elastic shear modulus, and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent activation energy. These results were correlated with the morphological properties of the films obtained from solutions in solvent/nonsolvent mixtures and compared with other quaternized polysulfones, having different hydrophobic characteristics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
33.
In addition to their high sodium content, cheeses are thought to induce an acid load to the body, which is associated with deleterious effects on consumers' health. Our objective was to explore the use of alkalinizing salts in partial substitution of NaCl to reduce both the sodium content and the acid-forming potential of cheese, without altering its sensory properties. Blue-veined cheeses were produced under industrial conditions, using brine salting followed by dry salting with a 4:1 (wt/wt) mixture of calcium lactate:NaCl or calcium citrate:NaCl. Sodium chloride was used in 2 granulometries: coarse (control treatment) and fine, to obtain homogeneous mixtures with the organic salts. Cheeses were then ripened for 56 d. No major appearance defects were observed during ripening. Calcium lactate substitution decreased the Na content of the cheese core by 33%, and calcium citrate substitution increased the citrate content of the cheese core by 410%, respectively, compared with fine NaCl. This study highlighted the substantial role of salt granulometry in sodium content, with the use of the coarse salt reducing the sodium content by 21% compared with fine salt. Sensory profiles showed nonsignificant differences in bitter and salty perceptions of salt-substituted cheeses with calcium lactate and calcium citrate compared with control cheeses. The use of calcium lactate should be considered to reduce the sodium content and improve the nutritional quality of cheeses while maintaining the sensory quality of the products. Alkalinizing organic salts could replace the acidifying salts KCl or CaCl2, which are currently used in salt replacement and are not recommended for consumers with renal disease. The method described here should be considered by cheese-making producers to improve the nutritional quality of cheese. Additional nutritional optimization strategies are suggested. 相似文献
34.
Pulsed laser deposition and processing of wide band gap semiconductors and related materials 总被引:1,自引:0,他引:1
R. D. Vispute S. Choopun R. Enck A. Patel V. Talyansky R. P. Sharma T. Venkatesan W. L. Sarney L. Salamancariba S. N. Andronescu A. A. Iliadis K. A. Jones 《Journal of Electronic Materials》1999,28(3):275-286
The present work describes the novel, relatively simple, and efficient technique of pulsed laser deposition for rapid prototyping
of thin films and multi-layer heterostructures of wide band gap semiconductors and related materials. In this method, a KrF
pulsed excimer laser is used for ablation of polycrystalline, stoichiometric targets of wide band gap materials. Upon laser
absorption by the target surface, a strong plasm a plume is produced which then condenses onto the substrate, kept at a suitable
distance from the target surface. We have optimized the processing parameters such as laser fluence, substrate temperature,
background gas pressure, target to substrate distance, and pulse repetition rate for the growth of high quality crstalline
thin films and heterostructures. The films have been characterized by x-ray diffraction, Rutherford backscattering and ion
channeling spectrometry, high resolution transmission electron microscopy, atomic force microscopy, ultraviolet (UV)-visible
spectroscopy, cathodoluminescence, and electrical transport measurements. We show that high quality AlN and GaN thin films
can be grown by pulsed laser deposition at relatively lower substrate temperatures (750–800°C) than those employed in metal
organic chemical vapor deposition (MOCVD), (1000–1100°C), an alternative growth method. The pulsed laser deposited GaN films
(∼0.5 μm thick), grown on AlN buffered sapphire (0001), shows an x-ray diffraction rocking curve full width at half maximum
(FWHM) of 5–7 arc-min. The ion channeling minimum yield in the surface region for AlN and GaN is ∼3%, indicating a high degree
of crystallinity. The optical band gap for AlN and GaN is found to be 6.2 and 3.4 eV, respectively. These epitaxial films
are shiny, and the surface root mean square roughness is ∼5–15 nm. The electrical resistivity of the GaN films is in the range
of 10−2–102 Θ-cm with a mobility in excess of 80 cm2V−1s−1 and a carrier concentration of 1017–1019 cm−3, depending upon the buffer layers and growth conditions. We have also demonstrated the application of the pulsed laser deposition
technique for integration of technologically important materials with the III–V nitrides. The examples include pulsed laser
deposition of ZnO/GaN heterostructures for UV-blue lasers and epitaxial growth of TiN on GaN and SiC for low resistance ohmic
contact metallization. Employing the pulsed laser, we also demonstrate a dry etching process for GaN and AlN films. 相似文献
35.
Maria Elena Zarif Saa Alexandra Yehia Bogdan Bi Veronica Stulu Sorin Vizireanu Gheorghe Dinescu Alina Maria Holban Florica Marinescu Ecaterina Andronescu Alexandru Mihai Grumezescu Alexandra Ctlina Bîrc Alexandru Titus Farcaiu 《International journal of molecular sciences》2021,22(23)
Despite the technological progress of the last decade, dental caries is still the most frequent oral health threat in children and adults alike. Such a condition has multiple triggers and is caused mainly by enamel degradation under the acidic attack of microbial cells, which compose the biofilm of the dental plaque. The biofilm of the dental plaque is a multispecific microbial consortium that periodically develops on mammalian teeth. It can be partially removed through mechanical forces by individual brushing or in specialized oral care facilities. Inhibition of microbial attachment and biofilm formation, as well as methods to strengthen dental enamel to microbial attack, represent the key factors in caries prevention. The purpose of this study was to elaborate a cold plasma-based method in order to modulate microbial attachment and biofilm formation and to improve the retention of fluoride (F−) in an enamel-like hydroxyapatite (HAP) model sample. Our results showed improved F retention in the HAP model, which correlated with an increased antimicrobial and antibiofilm effect. The obtained cold plasma with a dual effect exhibited through biofilm modulation and enamel strengthening through fluoridation is intended for dental application, such as preventing and treating dental caries and enamel deterioration. 相似文献
36.
Interactions between some dis‐azo dyes, different by either the position of their sulfonic groups or their number (Ponceau SS, Crocein Scarlet MOO, Congo Red, and Direct Blue 1), and some strong polycations (PCs), with cationic centers in their side chains and dye removal from artificial wastewaters were systematically investigated in this study. PCs with variable charge densities (CDs) were prepared from poly(dimethylaminoethyl methacrylate) by controlled quaternization with benzyl chloride. Even when the main process in the dye removal was charge neutralization (coagulation) for all of the dyes, significant effects of the CD and dis‐azo dye structure on the metachromatic behavior of the dyes in dilute aqueous solutions and on the dye removal efficiency were observed. The stability of the PC/azo dye complex and, connected with this, the flocculation window were higher when the PC with the highest CD was used. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
37.
Heavy metals adsorption on some iminodiacetate chelating resins as a function of the adsorption parameters 总被引:2,自引:0,他引:2
The adsorption properties of some novel chelating resins (CRs) bearing iminodiacetate groups for removal of heavy metal ions like: Cu(II), Co(II) and Ni(II) from aqueous solutions comparative with the commercial resin Amberlite IRC-748 have been studied in this work by a batch equilibrium technique. Quantitative analysis for adsorption was conducted using UV–vis spectroscopy to investigate the kinetics, adsorption isotherm and thermodynamics of the removal process considering equilibration time, pH, metal ion concentration and temperature as controlling parameters. The metal adsorption capacities, at pH 5, were in the order Cu(II) > Ni(II) > Co(II), for both the CR with 10 wt.% DVB (CR-10) and the commercial resin Amberlite IRC-748. The adsorption capacities on CR-10 were higher for Ni(II) and Co(II) ions, but lower for Cu(II) ions compared with Amberlite IRC-748. Both Freundlich and Langmuir isotherms well fitted on the adsorption results of Cu(II), Ni(II) and Co(II) ions on all iminodiacetate resins. 相似文献
38.
Ecaterina Avram Cornelia Luca Camelia Petrovan Camelia Mihailescu 《Polymer-Plastics Technology and Engineering》2013,52(5):757-768
The study attempted to establish the optimum reaction conditions for obtaining soluble chloromethylated polystyrene with a transformation degree higher than 50%. A paraformaldehyde and chlorotrimethylsilane mixture as chloromethylation agent and SnCl4 as catalyst were used. The transformation degree followed by the chlorine content depends on the following parameters: temperature, time, and [SnCl4]/[PS] and [Me3ClSi]/[PS] molar ratios. 相似文献
39.
The conformational behavior and unperturbed dimensions of polysulfone and chloromethylated polysulfone with different degrees of substitution were investigated by viscometry in N,N‐dimethylformamide; we intended to use these results with more complicated structures with different properties and applications. The effects of concentration and temperature on the coil densities and dimensions and of chlorine content on the unperturbed dimension parameters are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 524–531, 2006 相似文献
40.
Jose Maria Calderon Moreno Ecaterina VasilescuPaula Drob Petre OsiceanuCora Vasilescu Silviu Iulian DrobMonica Popa 《Materials Science and Engineering: B》2013,178(18):1195-1204
An advanced Ti–20Zr alloy was obtained by double vacuum melting in a semi-levitation furnace with cold crucible. The alloy shows fully lamellar α + β microstructure. Cyclic potentiodynamic polarization curves revealed that the alloy passivated easier, more rapid than Ti, having a more stable passive film in Ringer solutions of different pH values, simulating severe functional conditions of an implant. In neutral and alkaline Ringer solutions, the alloy passive film improved its properties in time (1500 h) by the deposition of protective hydroxyapatite, as was demonstrated by XPS, SEM, EDX, Raman and FT-IR measurements. Alloy presented lower corrosion rates and higher polarization resistances (from linear polarization measurements) than those of Ti (tens of times) proving a more resistant passive film. Alloy open circuit potentials had more electropositive values in comparison with Ti and tended to nobler values in time, which denote better passive state and its enhancement in time, due to the new depositions from the physiological solutions. Nyquist and Bode spectra depicted a more protective passive film on the alloy surface than on Ti surface. The passive film is formed by two layers: an inner barrier layer and an outer porous layer. An electric equivalent circuit with two time constants was modeled. 相似文献