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921.
Steven Hostyn Gitte VanBaelen Guy L.F. Lemire Bert U.W. Maes 《Advanced Synthesis \u0026amp; Catalysis》2008,350(16):2653-2660
9H‐α‐Carbolines have been prepared via consecutive intermolecular Buchwald–Hartwig reaction and Pd‐catalyzed intramolecular direct arylation from commercially available 2,3‐dichloropyridines and substituted anilines. The combination of a high reaction temperature (180 °C) and the use of DBU were found to be crucial for the intramolecular direct arylation reactions of the 3‐chloro‐N‐phenylpyridin‐2‐amines as no reaction was observed at 120 °C and 180 °C using different inorganic and other organic bases. On the other hand, nitrogen‐methylated pyridine analogues of these substrates {N‐[3‐chloro‐1‐methylpyridin‐2(1H)‐ylidene]anilines} do undergo ring closure at 120 °C, with K3PO4 as base, affording the respective 1‐methyl‐1H‐α‐carbolines in good yields. 相似文献
922.
923.
The exceptional properties associated with nanocrystalline materials are, to a large extent, a result of their high inter-crystalline volume fraction. However, the intrinsic instability of the nanostructured state may compromise the gain in properties by the occurrence of grain growth during exposure at elevated temperatures. Thermal stability is, therefore, a fundamental materials issue for nanocrystalline materials. This article describes what can be deduced from calorimetric measurements in the context of what is known about the microstructural evolution upon annealing of nanocrystalline Ni- and Co-based pulsed current electrodeposits. Special emphasis is put on interpreting the shape of the curves obtained by a differential scanning calorimetry (DSC). The temperature ranges for relaxation, segregation, precipitation, as well as abnormal and normal grain growth can be predicted. Also, by evaluating the shift in peak temperature with heating rate (Kissinger plot), the activation energies for grain growth can be obtained for the different materials. 相似文献
924.
925.
926.
Effect of Al content on high temperature erosion properties of arc-sprayed FeMnCrAl/Cr_3C_2 coatings
Three types of FeMnCrAl/Cr3C2 coatings with different Al content were deposited on 20# steel substrates by the high velocity arc spraying (HVAS) process. Surface microstructures of the coatings were analyzed by optical microscopy (OM) and X-ray diffractometry (XRD). High temperature erosion (HTE) tests were performed in an erosion tester at different impact angles. The surface morphologies of the eroded coatings were observed on a field emission scanning electron microscope(FE-SEM). The laminated structure is found on all the prepared coatings with the porosity and oxide fraction in the coatings decreasing with the Al content from 0 to 15% (mass fraction). Sample FA3 with 15% Al, possessing the lowest porosity and oxide fraction, has the best HTE resistance, which demonstrates that Al addition can improve the HTE resistance of the coatings. The erosion rate of sample FA1 exhibits a maximum value at 90° impact angle. The maximum erosion rates of both FA2 and FA3 samples appear in the range of 60°-90° impact angles. Erosion loss of the coatings occurs through brittle breaking, cutting and fatigue spalling. 相似文献
927.
928.
A magnetic field-assisted finishing process has been studied for high-aspect-ratio ion-etched silicon curvilinear micropore structures, which have potential application as mirrors for satellite-borne X-ray telescopes. The micropore sidewalls act as X-ray focusing mirrors, and lead to reductions in the mass-to-effective-area ratio of 10-1000 times, compared to traditional X-ray telescopes. This paper describes the processing principle for the surface finishing of the sidewalls of micropore structures (10, 20 μm and depth: 300 μm (aspect ratio ≈ 15, 30)), and the feasibility of achieving roughness ∼4 nm rms and improving the X-ray reflectivity of micropore sidewall surface are demonstrated. 相似文献
929.
The oxidation of a quasicrystal with the nominal compositionAl63Cu25Fe12 was studied around 800°Cin environmental and synthetic air by means of thermogravimetric analysis,electron microscopy, and analytical electron spectroscopy. In an earlyoxidation stage, -Al2O3 formed with an orientational relationship tothe quasicrystal. At the oxide–metal interface, -Al2O3transformed into large hexagonal shaped -Al2O3grains. The change in surface morphology indicated that at theoxide–gas interface -Al2O3 continued togrow as -Al2O3. Locally the metastable aluminalayer was transformed thoroughly into -Al2O3,which then continued to grow with a nodular morphology. On top of the oxidenodules, several at.% of Cu2+ were detected. 相似文献
930.
The Effect of Inorganic Pollutants on the Biocorrosivity of Marine Environment to a Low-Carbon Steel
The effect of heavy metals such as Fe, Zn, Pb, Cd, and Cu in quantities simulating economical pollution of natural sea water
on its biological pollution and corrosivity to a low-carbon CT3 steel is investigated under laboratory conditions. It is shown that under the experimental conditions, the steel corrosion
is controlled by biological factor of the medium.
__________
Translated from Zashchita Metallov, Vol. 41, No. 6, 2005, pp. 614–619.
Original Russian Text Copyright ? 2005 by Suponina, Koryakova, Kharchenko. 相似文献