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31.
Isabelle Minet Laszlo Hevesi Manuel Azenha Joseph Delhalle Zineb Mekhalif 《Journal of chromatography. A》2010,1217(17):2758-2767
We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 μg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products. 相似文献
32.
V.E. Panin V.S. Pleshanov S.A. Kobzeva S.P. Burkova 《Theoretical and Applied Fracture Mechanics》1998,29(2):99-102
Studied is the mesoscale behavior of plastic deformation and fracture of weld joints for austenic steels. Large-scale rotational modes of deformation in heat affected zones are identified with the first stage of formation of band structures; it is related to the “traveling neck” phenomenon in the base metal. The second stage is connected with crack generation and the state of affairs in the heart-affected zone. 相似文献
33.
Andrea Kühl Dietrich Bergner Hans-J. Ullrich Matthias Schlaubitz Peter Karduck 《Mikrochimica acta》1992,107(3-6):295-302
Parameters of the diffusion of N (up to 0.3 wt.%) in austenitic stainless steels (12 to 19 wt.% Cr, 12 to 16 wt.% Ni, up to 2 wt.% Mo) were determined within the temperature range of 1283–1573K. The small concentration gradients of N were successfully investigated using (1) mechanical serial sectioning technique in combination with either chemical N analysis or X-ray precision lattice parameter determination, and (2) measurements on microsections by means of either electron probe microanalysis or Kossel technique.The diffusion coefficients of N were found to be independent of its concentration. The alloying elements Cr and Mo reduce the N diffusivity in austenitic stainless steels which on the other hand is increased by Ni. 相似文献
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Coating properties of a novel water stationary phase in capillary supercritical fluid chromatography 下载免费PDF全文
The coating properties of a novel water stationary phase used in capillary supercritical fluid chromatography were investigated. The findings confirm that increasing the length or internal diameter of the type 316 stainless‐steel column used provides a linear increase in the volume of stationary phase present. Under normal operating conditions, results indicate that about 4.9 ± 0.5 μL/m of water phase is deposited uniformly inside of a typical 250 μm internal diameter 316 stainless‐steel column, which translates to an area coverage of about 6.3 ± 0.5 nL/mm2 regardless of dimension. Efforts to increase the stationary phase volume present showed that etching the stainless‐steel capillary wall using hydrofluoric acid was very effective for this. For instance, after five etching cycles, this volume doubled inside of both the type 304 and the type 316 stainless‐steel columns examined. This in turn doubled analyte retention, while maintaining good peak shape and column efficiency. Overall, 316 stainless‐steel columns were more resistant to etching than 304 stainless‐steel columns. Results indicate that this approach could be useful to employ as a means of controlling the volume of water stationary phase that can be established inside of the stainless‐steel columns used with this supercritical fluid chromatography technique. 相似文献
36.
A novel cedar-like Au nanoparticles (AuNPs) coating was fabricated on an etched stainless steel (SS) wire by direct chemical deposition and used as an efficient and unbreakable solid phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent growth of AuNPs in chloroauric acid solution. As a result, the uniform cedar-like AuNPs coating with larger surface area was tightly attached to the etched SS wire substrate. The AuNPs coated etched SS fiber (AuNPs/SS) was examined for SPME of ultraviolet (UV) filters, phthalate esters and aromatic hydrocarbons coupled to high-performance liquid chromatography with UV detection. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some aromatic hydrocarbons. Influential parameters of extraction and desorption time, temperature, stirring rate and ionic strength were investigated and optimized. The limits of detection ranged from 0.008 μg L−1 to 0.037 μg L−1. The single fiber repeatability varied from 3.90% to 4.50% and the fiber-to-fiber reproducibility ranged from 5.15% to 6.87%. The recovery of aromatic hydrocarbons in real water samples spiked at 2.0 μg L−1 and 20 μg L−1 ranged from 94.38% to 106.2% with the relative standard deviations below 6.44%. Furthermore the growth of the cedar-like AuNPs coating can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and withstands at least 200 extraction and desorption replicates. 相似文献
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采用氢化物发生-原子荧光光谱法测定低合金钢中砷的含量。样品经盐酸-硝酸混合酸消解,以盐酸(5+95)溶液为反应介质,15g·L~(-1)硼氢化钾-2g·L~(-1)氢氧化钾的混合溶液为还原剂,采用柠檬酸作为掩蔽剂。砷的质量浓度在60.0μg·L~(-1)以内与荧光强度呈线性关系,方法的检出限(3s/k)为0.023μg·L~(-1)。应用此法对标准钢样进行了分析,测定结果与认定值相符合,可满足钢铁中微量砷(质量分数0.001%~0.04%)的测定要求。 相似文献
39.
LI Dang-guo CHEN Da-rong WANG Jia-dao CHEN Hao-sheng State Key Laboratory of Tribology Tsinghua University Beijing P.R.China 《高等学校化学研究》2011,(4):697-702
The semi-conductive performances of hot growth film on 316L stainless steel were studied by means of electrochemical impedance spectroscopy(EIS) and Mott-Schottky analysis.The chemical compositions of the hot growth films were detected by X-ray photoelectron spectroscopy(XPS).The results show that the transfer resistance and film resistance increase with increasing temperature to 400℃,then they decrease sharply with further continuously increasing temperature.Formation time plays an important role in determ... 相似文献
40.
Nitin KarwaTatiana Gambaryan-Roisman Peter Stephan Cameron Tropea 《Experimental Thermal and Fluid Science》2011,35(7):1435-1443
An experimental study of heat transfer during quenching of a cylindrical stainless steel test specimen has been performed. A subcooled water jet is directed onto the upward facing flat face of the cylinder. The test specimen is heated to an initial temperature slightly above 900 °C and then quenched. The resulting boiling curves and heat transfer distributions are presented for impingement velocities of 2.85 and 6.4 m/s (Re = 7900 and 18,900). High-speed imaging shows that three distinct regions on the quenched surface can be identified: an expanding circular wetted region surrounding the impinging point, annular transition zone just outside the wetting front, and a unwetted region outside this zone. The free-surface of the liquid in the wetted region is smooth in the nucleate and transition boiling regimes. The annular transition zone or the wetting front region outside the wetted region is characterized by a highly disturbed liquid-gas interface, which can be attributed to intense vapor generation. At the outer edge of the transition zone, the liquid is deflected away from the surface. The velocity of the wetting front significantly increases with the jet impact velocity, which indicates that the wetting front position is governed by the ability of the flowing liquid to transport the bubbles radially outwards from the wetted region. 相似文献