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21.
Jaroslav Holoubek Josef Baldrian Jiřina Hromádková Miloš Steinhart 《Polymer International》2011,60(4):635-646
This study deals with the investigation of microphase‐separated morphology and phase behaviour in blends of polystyrene‐block‐polyisoprene with homopolystyrene and blends of polystyrene‐block‐poly(methyl methacrylate) with homopoly(methyl methacrylate) or homopolystyrene in the strong segregation regime using small‐angle X‐ray scattering and transmission electron microscopy as a function of composition, molecular weight of homopolymers, rM and temperature. Parameter rM = MH/MC (where MH is the molecular weight of homopolymer and MC that of the corresponding block copolymer) was selected to encompass behaviour of the chains denoted as a ‘wet brush’ (i.e. rM < 1). The relative domain spacing D/Do increases in the regime 0 < rM?1 with increasing concentration of homopolymer wP and increasing rM but depends on the specific implemented morphology. We tested a new approximate D/Do versus wP relation in the strong segregation regime using block copolymers of high molecular weights. It is shown that the parameters rM and χ3/2N determine the slope of the D/Do versus wP relation in the strong segregation regime and the new approximation generally matches the experimental data better than the approximations used so far. Copyright © 2010 Society of Chemical Industry 相似文献
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Seung Min Lee Benjamin P. McCarthy Pavel Hrma Jaehun Chun Richard Pokorny Jaroslav Klouzek Albert A. Kruger 《Journal of the American Ceramic Society》2020,103(3):1615-1630
During the final stages of conversion of melter feed (glass batch) to molten glass, the glass-forming melt becomes a continuous liquid phase that encapsulates dissolving solid particles and gas bubbles that produce primary foam at the bottom of the cold cap (the reacting melter feed in an electric glass-melting furnace). The glass-forming melt viscosity plays a dominant role in primary foam formation, stability, and eventual collapse, thus affecting the rate of melting (the glass production rate per cold-cap area). We have traced the glass-forming melt viscosity during the final stages of feed-to-glass conversion as it changes in response to changing temperature and composition (resulting from dissolving solid particles). For this study, we used high-level waste melter feeds—taking advantage of the large amount of data available to us—and a variety of experimental techniques (feed expansion test, evolved gas analysis, thermogravimetric analyzer-differential scanning calorimetry, X-ray diffraction, and viscometer). Starting with a relatively low value at the moment when the melt connects, melt viscosity reached maximum within the primary foam layer and then decreased to its final melter operating temperature value. At the cold-cap bottom—the boundary between the primary foam layer and the thermal boundary layer—where physicochemical reactions of a melter feed influence the driving force of the heat transfer from the melt to the cold cap, the melt viscosity affects the rate of melting predominantly through its effect on the temperature at which primary foam is collapsing. 相似文献
25.
M. K. Mohanapriya Kalim Deshmukh Jaroslav Kadlec Kishor Kumar Sadasivuni Muhammad Faisal N. A. Nambi Raj 《Polymer-Plastics Technology and Engineering》2020,59(8):847-863
ABSTRACTNovel tertiary nanocomposite films comprising of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and titanium dioxide (TiO2) nanoparticles (NPS) were prepared using simple solvent casting method. The structural, thermal, morphological, thermo-mechanical and electromagnetic interference (EMI) shielding properties of PVA/PSSA/TiO2 nanocomposite films were investigated. The EMI shielding effectiveness (SE) of PVA/PSSA/TiO2 nanocomposite films in the X and Ku band was found to be 12 dB and 13 dB respectively at 25 wt% TiO2 NPs loading. These results demonstrate the possible applications of PVA/PSSA/TiO2 nanocomposite films as low cost, lightweight and flexible material for EMI shielding. 相似文献
26.
Vladislav Oliva Jaroslav Vclavík Ale Materna Patrick Lorenzetto Andreas Furmanek 《Fusion Engineering and Design》2009,84(7-11):1450-1454
An objective of experiments and finite element simulations was to check the stiffness, the strength and the fatigue resistance of the attachment of the First Wall panels onto a shield block of blanket modules according to the ITER 2001 design. The panel has a poloidal key at the rear side (in so-called option A with the rear access bolting) and it is attached by means of special studs located on a key-way in the shield block. Special device for a test of stud tensile pre-load relaxation during a thermal cycling was developed. True-to-scale panels, the shield block mock-up and simplified studs were fabricated and the assembly was loaded alternatively by radial moment, poloidal force or poloidal moment simulating the loading during off-normal plasma operations. Thermal cycling led to an acceptable stud pre-load relaxation. Mechanical cycling caused neither the pre-load relaxation nor the loss of the contact in the key-way nor a damage of the attachment system. The combination of poloidal moment and radial force during vertical displacement events (VDEs) seems to be a most dangerous case because it could lead to the loss of the key–key-way contact. 相似文献
27.
Application of the Electrodiffusion Method to Measure Wall Shear Stress: Integrating Theory and Practice
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Lutz Böhm Sepideh Jankhah Jaroslav Tihon Pierre R. Bérubé Matthias Kraume 《化学工程与技术》2014,37(6):938-950
The electrodiffusion method has been used in fluid dynamic research for the past 50 years. It allows the measurement of wall shear stress, a crucial parameter, e.g., for the cleaning of membrane modules used in water filtration. Various authors have published articles dealing with the theory behind this technique. But no paper collects all the knowledge assembled over five decades of application. Here, comprehensive summary of the theory of steady flow, unsteady flow, and transient voltage step experiments is given. Factors influencing the accuracy of the measurements are discussed. Furthermore, a new approach to calibrate the system from voltage step experiments is introduced, and practical issues related to its application in flow measurements are discussed for an exemplary signal response to a near‐wall flow. 相似文献
28.
Thin composite layers (tin in plasma polymer matrix) were prepared in a stainless steel vacuum chamber. An RF powered magnetron with tin target was used to excite the discharge and to activate the monomer species (n-hexane). The gas mixture introduced comprised Ar and n-hexane vapours. The properties of the films and chemical composition were characterized by AFM (surface morphology), TEM and Electron tomography (bulk structure characterization), XPS and FTIR spectroscopy (chemical composition analyses). Current-voltage characteristics were measured to examine the electrical properties of the layers and their dependence on the deposition parameters. 相似文献
29.
Jaroslav Stejskal Miroslava Trchová Jir̆ina Hromádková Jana Kovár̆ová Andrea Kalendová 《Polymer International》2010,59(7):875-878
The carbonization of nanostructures afforded by conducting polymers represents a new route to the preparation of functional nanostructured carbons. The exposure of colloidal polyaniline particles stabilized with poly(N‐vinylpyrrolidone) or silica nanoparticles at 650 °C in inert atmosphere led, in both cases, to nitrogen‐containing carbonaceous materials with specific surface areas of 200 and 205 m2 g?1, respectively, and conductivities of 8.3 × 10?7 and 1.9 × 10?10 S cm?1, respectively. The latter material contained 77 wt% of silica. The original particulate nanostructure of the samples was preserved after carbonization. The carbon‐to‐nitrogen atomic ratio was 7.2 and 7.9; the nitrogen content in the carbonized polyaniline–poly(N‐vinylpyrrolidone) particles was 10.8 wt%. Thermogravimetric analysis in air revealed their stability to be up to 500 °C. This is comparable with commercial multi‐wall carbon nanotubes, which have similar areas of application. The nitrogen‐containing carbons are potentially useful as supports for catalysts and in applications where carbon of higher hydrophilicity would be of benefit. Copyright © 2010 Society of Chemical Industry 相似文献
30.
Mária Omastová Katarína Mosnáčková Miroslava Trchová Elena N. Konyushenko Jaroslav Stejskal Pavol Fedorko Jan Prokeš 《Synthetic Metals》2010,160(7-8):701-707
The conducting polymers, polypyrrole and polyaniline, were synthesized by chemical oxidative polymerization of the corresponding monomers in 0.1 M sulfuric acid using cerium(IV) sulfate as the oxidant at mole ratios of oxidant-to-monomer ranging from 0.5 to 3. The yields of the oxidation products were determined, and the samples were characterized with respect to their elemental composition, molecular structure, and morphology. The conductivity of polypyrrole prepared in 0.1 M sulfuric acid, 10?1 to 100 S cm?1, was higher compared with the conductivity of polyaniline prepared under the same conditions, 10?3 to 10?1 S cm?1. The loss of mass after deprotonation with ammonium hydroxide is reported, and discussed in terms of the type of protonation as also reflected by FTIR spectroscopy. The conductivity of polypyrrole bases remained at relatively high level, 10?5 to 10?3 S cm?1, while PANI bases became non-conducting, 10?12 to 10?10 S cm?1. The polymers had a granular morphology in all cases. 相似文献