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51.
A. Yu. Vasil’kov I. P. Suzdalev Yu. V. Maksimov L. N. Nikitin A. V. Naumkin S. S. Abramchuk E. M. Tolstopyatov P. N. Grakovich 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(6):985-991
A method for synthesizing iron-containing nanocomposite based on fibroporous polytetrafluoroethylene (PTFE) is described. Fibroporous PTFE obtained under the radiation of a CO2 laser on block PTFE is modified in supercritical carbon dioxide (sc CO2) to form micro- and nanoporous structures. Porous fluoropolymer is treated with a solution of bis(toluene)iron(0) obtained by metal-vapor synthesis (MVS). The composition and structure of iron-containing fluoropolymer is studied by transmission electron microscopy and X-ray photoelectron and Mössbauer spectroscopy. Fe nanoparticles with an average size of 9 nm, consisting of ~30% FeO and ~70% Fe3+, are registered in the sample. Fe0 nanoparticles are stabilized in fluoropolymer pores and are coated with nanoparticles of nonstoichiometric iron oxides that have superparamagnetic properties. 相似文献
52.
C. Zhu A. Javed P. Li G. Y. Liang P. Xiao 《Surface and interface analysis : SIA》2013,45(11-12):1680-1689
In this study, the initial oxidation behaviour of laser‐treated Al/NiCrAlY bond‐coat is investigated. Two approaches, (i) Al film sputtering on the surface of bond‐coat and (ii) laser treatment, have been taken to enhance the oxidation resistance of NiCrAlY bond‐coat. Experimental results showed that after laser treatment, the Al/NiCrAlY bond‐coat exhibited a columnar dendritic microstructure without cracks and voids. A dense and continuous α‐Al2O3/Cr2O3 multilayer was found to form on the bond‐coat surface. Results on the cyclic oxidation at 1200 °C (for time ≤ 204 h) revealed that the laser‐treated Al/NiCrAlY bond‐coat exhibited better oxidation resistance compared to as‐sprayed NiCrAlY, Al/NiCrAlY and laser‐remelted NiCrAlY bond‐coat. The formation of θ‐Al2O3, NiO, Cr2O3 and NiCr2O4 spinel oxides was observed to be suppressed due to the preformed α‐Al2O3 scale during initial oxidation on the surface of laser pre‐oxidized Al/NiCrAlY bond‐coat. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
53.
Pattana Kueseng Pongdhorn Sae-oui Chakrit Sirisinha Karl I. Jacob Nittaya Rattanasom 《Polymer Testing》2013
50/50 NR/NBR blends with various MWCNT loadings were prepared by mixing with MWCNT/NR masterbatches on a two-roll mill and sheeted off at the smallest nip gap. Then, the effect of milling direction, machine direction (MD) and transverse direction (TD), on the mechanical and electrical properties of the blends was elucidated. Dichroic ratio and SEM results confirmed that most of the MWCNTs were aligned along MD when MWCNT was less than 4 phr, and the number of agglomerates increased when MWCNT was more than 4 phr. Additionally, anisotropic properties were clearly observed when 4 phr MWCNT was loaded. At 4 phr MWCNT, 100% modulus and tensile strength in the MD were about 1.5 and 1.3 times higher than those in the TD, respectively. Moreover, electrical conductivity in the MD was superior to that in the TD by about 3 orders of magnitude. Results from dynamic mechanical tests also showed that the maximum tan δ in the MD sample was lower than that in the corresponding TD sample. In addition, the storage modulus at 30 °C for the MD sample containing 4 phr MWCNT was 1.15 higher than that of the corresponding TD sample. This stronger reinforcement efficiency resulted from the combination of the greater alignment and dispersion of most MWCNTs in the MD sample. 相似文献
54.
55.
Ilya Kuselman Elena Kardash Emil Bashkansky Francesca Pennecchi Stephen L. R. Ellison Karen Ginsbury Malka Epstein Aleš Fajgelj Yury Karpov 《Accreditation and quality assurance》2013,18(6):459-467
A new technique for quantification of human errors in chemical analysis using expert judgments is described. This technique is based on the house-of-security approach developed recently in the field of safety and security for prevention of terrorist and criminal attacks against an organization. The following relative quantification parameters (expressed in %) are proposed in the technique: (a) likelihood score of human error in a chemical analytical measurement/testing method, (b) severity score of human error for reliability of the test results, (c) importance score of a component of a laboratory quality system, and (d) effectiveness score of the quality system as a whole in preventing/blocking human error. As an example, 34 scenarios of human error in pH measurement of groundwater are discussed and quantified. 相似文献
56.
Shao‐Bo Mi 《Surface and interface analysis : SIA》2014,46(2):102-105
Structural properties of YBa2Cu3O7‐δ/PrBa2Cu3O7‐δ heterointerfaces have been investigated by aberration‐corrected electron microscopy. Experimental evidence shows that c‐axis‐oriented YBa2Cu3O7‐δ/PrBa2Cu3O7‐δ heterostructures with atomically sharp interface epitaxially grow on SrTiO3(001) substrates. In terms of the contrast analysis, no apparent interdiffusion between YBa2Cu3O7‐δ and PrBa2Cu3O7‐δ occurs at the interface. In addition, stand‐off misfit dislocations and planar faults appear within PrBa2Cu3O7‐δ layer near the interface. Both misfit dislocations and interfacial dislocations resulting from the termination of planar faults contribute to misfit relaxation at the YBa2Cu3O7‐δ/PrBa2Cu3O7‐δ interface. The defect configuration of planar faults and stand‐off misfit dislocations is explored. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
57.
《中国化学快报》2022,33(8):3757-3761
Selective hydrogenation of cinnamaldehyde (CAL) toward cinnamyl alcohol (COL) is an extremely important and challenging reaction. Herein, a series of PtxFey-Al2O3 bimetallic catalysts with varied Pt to Fe ratios were prepared by incipient wetness impregnation method. The introduction of Fe significantly modifies the electronic and surface properties of Pt, which clearly enhances the C=O hydrogenation selectivity. Among all the catalysts, Pt3Fe-Al2O3 displays the best catalytic performance and the conversion of CAL is 96.6% with 77.2% selectivity of COL within 1 h. In addition, Pt3Fe-Al2O3 had excellent reusability with 76% COL selectivity after five runs of the recycle process. Further characterization of the fresh, used and cycled catalysts revealed that the structure and electronic state of the synthesized PtxFey-Al2O3 are unchanged after hydrogenation reaction. The identical-location transmission electron microscopy (IL-TEM) results revealed that the interaction between the nanoparticles and the supports was strong and the catalyst was relatively stable. 相似文献
58.
Ying Zhang Tongtong Gao Chengshan Dai Liyun Zhang Yiming Niu Junnan Chen Zhong-Wen Liu Bingsen Zhang 《中国化学快报》2022,33(6):2911-2914
Selective hydrogenation of substituted nitroarenes is an important reaction to obtain amines.Supported metal catalysts are wildly used in this reaction because the surface structure of supports can tune the properties of the supported metal nanoparticles (NPs) and promote the selectivity to amines.Herein,Pt NPs were immobilized on Fe OOH,Fe3O4andα-Fe2O3nanorods to synthesize a series of iron compounds supported Pt catalysts by liquid phase reduction me... 相似文献
59.
为积极应对化石能源枯竭和生态环境日益严峻等问题,可再生生物质资源的深度开发并进一步替代传统能源或石化原料被广泛认可.利用高效催化技术将生物质资源转化为高附加值的平台化合物,有望衍生出大量具备新颖结构与功能的绿色化学品.2,5-呋喃二甲酸(FDCA)作为重要的生物质基平台化合物之一,具有巨大的市场应用价值,其中因其与化石基对苯二甲酸(PTA)有着极其相似的化学结构,以FDCA替代PTA作为合成单体制备大宗聚合物备受关注.以5-羟甲基糠醛(HMF)为原料,采用多相催化体系(主要是贵金属催化剂)选择氧化制备FDCA是目前广泛采用的方法.但“HMF路线”面临一些基础性的难题,如HMF熔点较低,需低温存储,增加了实际应用中的运输成本;HMF在碱性溶液中易降解,导致反应过程中碳平衡损失;HMF结构中含有的不对称的羟基和醛基官能团在氧化反应中会发生竞争反应,致使反应副产物较多;此外,碱性反应介质中通常会得到醛基优先氧化的中间体5-羟甲基-2-呋喃甲酸(HMFCA),但由于HMFCA结构中羧基官能团的存在使得羟基进一步氧化较为困难,通常需要增加碱浓度、提升温度或压力,使反应条件变得苛刻.因此,寻求新的原料替代HMF,实现温和条件下高效合成FDCA具有重要意义.本文采用改性后的碳纳米管负载Pd催化剂(Pd/o-CNT),从具有独特对称结构的2,5-二羟甲基呋喃(BHMF)出发,提出一种新颖、高效催化合成FDCA的“BHMF路线”.反应在60°C常压下进行,BHMF在20 min内即可完全转化,60 min后FDCA的产率最高可达93.0%,优于相同条件下HMF为原料时的性能(FDCA产率仅为35.7%).相比于未作处理的碳纳米管负载钯催化剂(Pd/CNT),Pd/o-CNT催化剂具有更高含量的氢化钯(PdHx)物种,显著促进了FDCA产率的提升.Pd/o-CNT在循环使用10次后,BHMF仍能完全转化,FDCA产率维持在75%.稳定性下降可能与活性物种流失、团聚及价态变化有关.基于对照试验,本文提出了可能的反应路径,即BHMF主要是通过2,5-二甲酰基呋喃和5-甲酰基-2-呋喃甲酸作为过程中间体,有效转化为FDCA,从而规避并减少生成HMF和活性较低的HMFCA.本文通过以新原料BHMF作底物,实现了高效制备生物基平台化合物FDCA,为生物质的产业化应用提供了新的研究思路. 相似文献
60.
建立了电感耦合等离子体质谱法测定新型抗菌不锈钢在生理盐水和磷酸盐缓冲液中的镓溶出量的分析方法. 为了消除盐沉积的影响,在进样系统中引入了Burgerner AriMist耐高盐雾化器和加厚嵌片. 同时,通过稀释样品并使用铟作为内标校正了基体干扰. 在选定的分析条件下,校准曲线的线性相关系数大于0.999,方法检出限为0.08 μg/L,测定结果的相对标准偏差小于3.0%(n=6),加标回收率为98.3%~105.4%. 方法操作简单快速,可用于生理盐水和磷酸盐缓冲液中痕量镓的快速测定. 相似文献