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1.
The hot corrosion Type II of the alloys FeCr20, FeCr20Ni10, FeCr20Ni20, and FeCr20Co10 is investigated at 700°C in air + 0.5% SO2 with deposits consisting of Na2SO4 and a eutectic mixture of Na2SO4 and MgSO4 for 24, 100, and 300 h. The alloying elements nickel and cobalt have a positive influence when tests are conducted using a MgSO4‐Na2SO4 deposit. In this case, they reduce the metal loss and increase the time to the propagation stage. In contrast, when the alloys are exposed with a Na2SO4 deposit, these alloying elements increase the metal loss and allow for the transition to the propagation stage because they can form molten phases with the Na2SO4. During the incubation stage an oxide scale forms on the FeCr20 alloy, which is thicker than the one formed during exposure without a deposit, and iron oxides are observed, which precipitate in the deposit. The propagation stage occurs by a dissolution and precipitation mechanism forming localized pitting attack. Iron is the main species that dissolves and precipitates, while chromium remains mainly as an oxide beneath the initial surface. The additional elements are found in the pit and in the salt deposit. 相似文献
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Celin Gürler Mathias Feyen Silke Behrens Nina Matoussevitch Annette M. Schmidt 《Polymer》2008,49(9):2211-2216
Much effort is conducted to construct artificial objects that are capable of converting chemical or electromagnetic energy into a specific, predetermined motion on the nanoscale. We present results on the synthesis of core–shell nanoparticles capable to be set in rotation by the application of electromagnetic fields. The nanorotors implied in the study are based on the cobalt nanospheres decorated with a stabilizing brush shell composed of poly(?-caprolactone) that is attached by surface-initiated polymerization. The functional cores used as macroinitiators can be fabricated alternatively by a two-step or a one-step process. 相似文献
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Martin Gneiser Julia Heidemann Mathias Klier Andrea Landherr Florian Probst 《Information Systems and E-Business Management》2012,10(1):61-84
Online social networks have been gaining increasing economic importance in light of the rising number of their users. Numerous
recent acquisitions priced at enormous amounts have illustrated this development and revealed the need for adequate business
valuation models. The value of an online social network is largely determined by the value of its users, the relationships
between these users, and the resulting network effects. Therefore, the interconnectedness of a user within the network has
to be considered explicitly to get a reasonable estimate for its economic value. Established standard business valuation models,
however, do not account for these aspects sufficiently. Thus, we propose an economic model for the valuation of online social
networks, which takes into account the users’ interconnectedness within the network. Furthermore, we analyze different centrality
measures, which can be used to quantify users’ interconnectedness in online social networks and propose a measure which is
based on the PageRank-algorithm. Finally, the practical application of the model is illustrated by an example of the European
online social network XING.com. 相似文献
8.
An extensive experimental investigation of the Fe-Al-Ti system by metallography, microprobe analysis, and XRD on quenched specimens and on diffusion couples is presented. Two isothermal sections at 800 and 1000 °C were established; they differ substantially from the existing (800 °C) or partly determined (1000 °C) diagrams. From these results, existence of the τ1 phase (Fe2AlTi) can be ruled out. Existence of the ternary compounds, τ2 (Al2FeTi) and τ3 (Al22Fe3Ti8), is confirmed. The composition limits of both phases were determined; they differ considerably from those given in earlier reports. The τ2 phase apparently exists in a cubic and a tetragonal polymorph, depending on composition. The cubic form exists at high titanium contents. At 1000 °C, the two polymorphs are separated by a miscibility gap. At compositions where the “X phase” (Al69Fe25Ti6) was previously reported, single-phase samples were obtained at both temperatures. From the present results, there is no evidence to assume that this is a new ternary phase rather than the ternary homogeneity range of the Al3Fe phase. In addition, extensions of the binary intermetallic phases into the ternary system were determined. 相似文献
9.
H. B. Knight Lee P. Witnauer W. E. Palm R. E. Koos Daniel Swern 《Journal of the American Oil Chemists' Society》1959,36(9):382-388
Summary Thirty-one acyloxy or aryloxy esters prepared from hydroxystearic acids have been evaluated as plasticizers for a vinyl chloride-vinyl
acetate copolymer (95∶5). Many of them were found to be primary plasticizers, having outstanding low-temperature performance
when employed at the 35% level. Formulations with these compounds compared quite favorably in tensile properties with those
containing the di-2-ethylhexyl esters of phthalic, sebacic, azelaic, and adipic acids. Volatility losses were similar to those
of the four di-2-ethylhexyl esters. The loss of plasticizer through migration was equal to or less than that from compositions
containing the esters of sebacic, azelaic, and adipic acids but was greater than that of the phthalate ester.
A mechanistic scheme of plasticizer-polymer interaction has been presented, proposing that the rate of diffusion of plasticizer
through the polymer mass is a controlling factor in both good low-temperature performance and the resulting high migration
losses. Methyl esters, some aromatic esters, and esters containing three or more polar centers have improved permanence but
show a more rapid change in torsional modulus as the temperature is lowered during the determination of the Clash-Berg stiffening
temperature.
Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture. 相似文献
10.
Semra Kurama Gunes Cigdemir Hasan Mandal Mathias Herrmann 《Journal of the American Ceramic Society》2006,89(2):714-716
In the present work, multi-cation-doped (Sr2+ –Mg2+ ) SiAlON ceramics were investigated. MgO and SrO were used in 100:0 and 50:50 molar ratios. The mixture was sintered at 1800° and 1830°C for 1 h in a gas pressure-sintering furnace. The results showed that sintered samples were composed of mainly α- and β-SiAlON phases and small amounts of some Sr-containing phases and SiAlON polytypes. According to Rietveld analysis of X-ray diffraction patterns, Mg is incorporated into the α-SiAlON structure. However, the incorporation of Sr is limited. 相似文献