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41.
Miroslav Mrlik Michal Sedlacik Vladimir Pavlinek Pavel Bazant Petr Saha Petra Peer Petr Filip 《应用聚合物科学杂志》2013,128(5):2977-2982
One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
42.
Triblock copolymer additives are found to stabilize thin-film dewetting of B-type homopolymers with degree of polymerization (DOP) P deposited on silicon oxide. The triblock copolymers’ architectures are ABA and BAB, where A and B represent anchoring and nonadsorbing blocks with DOP's N A and N B, respectively. Upon adding 1 vol.% of the ABA additive, dewetting is only observed for anchoring block molar fractions, f A, below 4%. Dewetting is arrested in films containing 1 vol.% ABA, BAB, or AB that have similar values of f A ~ 8%, showing that chain architecture is not the only indicator of a successful additive. Compared with films containing diblock copolymers, the interfacial excess, z*, of triblock copolymers at the melt/substrate interface is relatively small as measured by low-energy forward-recoil spectrometry. Because adsorbed copolymers can reduce the capillary driving force for dewetting and participate in entanglements with matrix chains, the higher coverage and grafting density observed for diblock copolymers suggests that diblocks are more effective than triblocks in improving thin-film stability. 相似文献
43.
Petr Praus Ladislav Svoboda Richard Dvorský Martin Reli 《Ceramics International》2018,44(4):3837-3846
Tin dioxide nanoparticles were prepared in the presence of graphitized carbon nitride (g-C3N4) forming nanocomposites with different contents of SnO2 up to 40 %. G-C3N4 was synthetized by heating of melamine at 550 °C in the open air and Sn2+ ions were precipitated by sodium hydroxide in g-C3N4 aqueous dispersions. Resulting mixtures were dried by freezing at ?20 °C and calcined at 450 °C to obtain SnO2/g-C3N4 nanocomposites.The nanocomposites were characterized by common characterization methods in solid state and in their aqueous dispersions using dynamic light scattering (DLS) analysis and photocatalysis. SnO2 nanoparticles in the nanocomposites were found to have an average size of 4 nm, however, those precipitated without g-C3N4 had an average size of 14 nm. Separation of photoinduced electron and holes via heterojunction between SnO2 and g-C3N4 was demonstrated by photocatalytic decomposition of Rhodamine B (RhB) under LED visible irradiation (416 nm) and photocurrent measurements. The most photocatalytically active nanocomposite contained 10 % of SnO2. Graphitized carbon nitride was assumed to serve as a template structure for the preparation of SnO2 nanoparticles with a narrow size distribution without using any stabilizing additives. 相似文献
44.
Fabio La Mantia Fabio Rosciano Nicolas Tran Petr Novák 《Journal of Applied Electrochemistry》2008,38(7):893-896
Li1+x
(Ni1/3Mn1/3Co1/3)1−x
O2 (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau”
was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li+ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric
(x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed
that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li+, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric
material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds
and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V
vs. Li/Li+. No oxygen evolution was detected for the stoichiometric compound. 相似文献
45.
Petr Ptá?ek František Šoukal Tomáš Opravil Jaromír Havlica Ji?í Brandštetr 《Powder Technology》2011,208(1):20-25
The thermal decomposition of kaolinite was studied by differential thermogravimetry (DTG) technique under non-isothermal conditions. Samples of industrially treated (washed) kaolin with high content of the medium ordered kaolinite were calcined using a heating rate from 1 to 40 K min− 1. The apparent activation energy and frequency factor for the dehydroxylation of kaolinite was evaluated by Kissinger method as 195 ± 2 kJ × mol− 1 and (8.58 ± 0.33) × 1014 s− 1, respectively. Avrami exponent of the process was estimated using Kissinger empirical kinetic models and Carne equation. 相似文献
46.
Alexander Kromka Marina Davydova Bohuslav Rezek Milan Vanecek Martin Stuchlik Petr Exnar Martin Kalbac 《Diamond and Related Materials》2010,19(2-3):196-200
Toxic gas sensing device with metal electrodes built into nanocrystalline diamond (NCD) is investigated. The NCD morphology is controlled via seeding and/or deposition time. The surface properties and morphology of NCD are studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). AFM measurements reveal increase in NCD surface area by up to 13%. Gas sensing properties of H-terminated NCD device show high sensitivity towards oxidizing species where the surface conductivity is increased by an order of magnitude for humid air and by three orders of magnitude for COCl2. The surface conductivity exhibits a small decrease to reducing spices (CO2, NH3). 相似文献
47.
Cultivar differences of total anthocyanins and anthocyanidins in red and purple-fleshed potatoes and their relation to antioxidant activity 总被引:1,自引:0,他引:1
Jaromír Lachman Karel Hamouz Miloslav Šulc Matyáš Orsák Vladimír Pivec Alena Hejtmánková Petr Dvořák Jaroslav Čepl 《Food chemistry》2009
Total anthocyanins (TAC) and individual anthocyanidins (AN) after hydrolysis were measured in 15 red and purple-fleshed potato cultivars produced in five different locations in the Czech Republic and a new cultivar Blaue St. Galler from Switzerland. It was found that TAC, expressed as cyanidin content, varied between 0.7 mg 100 g−1 FW (cv. Blue Congo) and 74.3 mg 100 g−1 FW (cv. Blaue Ludiano). Major differences in cultivars were found for AN relative abundance. For cv. Highland Burgundy Red a high proportion of pelargonidin (98.7%) was characteristic, whereas cv. British Columbia Blue contained almost exclusively cyanidin. Cultivars Violette and Vitelotte showed a relatively high content of malvidin. Cultivar Shetland Black differed from others with its higher content of peonidin (on average 36.7%). High petunidin abundance in the cultivars Valfi, Blue Congo, Salad Blue, Blaue St. Galler, Blaue Hindel Bank, Blaue Ludiano, Blaue Schweden, Farbe Kartoffel and Salad Red was found. TAC and AN contents highly corresponded with antioxidant activity (AA) determined with the ABTS, FRAP and DPPH assays in vitro. High AA was shown by the cultivars Vitelotte, Violette, Blaue Ludiano, Hafija, and Highland Burgundy Red. Increased height above sea level, higher annual sum of precipitation, and lower annual average temperatures caused higher AA and TAC. A high degree of hydroxylation and/or methoxylation of individual anthocyanidins could contribute in conjunction with other phenolics to high AA (peonidin, delphinidin and malvidin in the cultivars Blue Congo, Highland Burgundy Red and Shetland Black). Consequently, new red and purple-fleshed cultivars with high TAC and highly methoxylated and/or hydroxylated AN could be a promising source of favourable antioxidants in human nutrition. 相似文献
48.
为了正确将表面活性剂使用到制革的酶处理工序中,本试验分别在胰酶和AS1.398酶溶液中添加质量浓度10%的明胶和不同量的十二烷基苯磺酸钠(阴离子型表面活性剂)、十二烷基三甲基氯化铵(阳离子型表面活性剂)和平平加O(非离子型表面活性剂),来测定不同表面活性剂对酶活力和明胶水解程度的影响。试验表明:3种表面活性剂对酶活均起到激活作用;但添加阴离子型表面活性剂后,明胶的水解程度提高。为了探究它们在溶液中所起的主导性作用,在试验第二步,将3种表面活性剂加入到质量浓度0.4%明胶+酶的混合液中,研究混合液在37℃时的Zeta电位的变化。试验表明:加入阴离子型,Zeta电位的绝对值提升;加入阳离子型,Zeta电位从负变为正;加入非离子型,Zeta电位绝对值降低。结合实际制革生产中对皮革高性能的要求,研究表明:在进行酶软化时,应优先选择非离子型表面活性剂。 相似文献
49.
Vandana Srivastava Petr Chýlek R G. Pinnick R. L. Dod T. Novakov 《Aerosol science and technology》2013,47(1):151-160
We collected several samples of fresh snow from the areas of southern New Mexico and western Texas. Samples were analyzed to determine graphitic carbon content of snow in rural and urban areas and to compare these present values with those obtained from deep ice core samples several thousand years old. To model the optical properties of snow grains containing carbon we used several different versions of effective medium approximations. Calculations are compared with microwave analog measurements to determine which of these approximations can reasonably well predict the properties of mixtures such as snow and carbon. Suggestions regarding which of the effective medium approximations that should not be used are presented. 相似文献
50.
Petr Hlubina 《Journal of Modern Optics》2013,60(10):1745-1756
Abstract The effect of a variable Gaussian response function of a monochromator in a detecting system with a broadband detector is included in the theoretical and experimental analysis of time-domain and spectral-domain interference of two light beams from a source of a multimode Gaussian spectrum. The time-domain theoretical analysis gives the analytic expressions for the measured complex degree of temporal coherence of the light with and without the effect of variable spectral bandpass of the detecting system. The spectral-domain theoretical analysis of the two-beam interference gives the spectral interference law from which the visibility of the spectral interference fringes resolved for a given delay in the interferometer by a spectrometer is expressed as a function of the bandpass of the spectrometer. The theoretical conclusions are confirmed experimentally in the Michelson interferometer configuration using a laser diode operated below the threshold, a prism monochromator and a p-i-n photodetector. From the width of the central peak in the measured visibility dependence that narrows with increasing slit width of the monochromator, the spectral bandpass of the monochromator is evaluated. It is also shown how the visibility of the spectral interference fringes decreases as the slit width of the prism spectrometer increases. 相似文献