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11.
Dr. Qiao Chen Xin Yi Meirong Huang Wenjia Wu Qiyang Song Changjiang Nie Prof. Shun Wang Prof. Hongwei Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(33):7463-7469
Precursors and catalysts play vital roles in chemical reactions. Considerable efforts have been devoted to the investigation of catalysts for graphene growth by chemical vapor deposition in recent years. However, there has been little research on precursors because of a lack of innovation in term of creating a controllable feeding method. Herein, we present a novel sustained and controlled release approach, and develop a convenient, safe, and potentially scalable feeding system with the assistance of matrix materials and a simple portable feeder. As a result, a highly volatile liquid precursor can be fed accurately to grow large-area, uniform graphene films with optimal properties. This feeding approach will further benefit the synthesis of other two-dimensional materials from various precursors. 相似文献
12.
A CE instrument that can be assembled from commercially available components with minimal construction effort is described. Except for the electronic control circuitry no specially made parts are required. It is based on a flexible design of microfluidic, electropneumatic, and electronic sections and different configurations can easily be implemented. Automated injection into the capillary is performed hydrodynamically by the application of a pressure for a controlled length of time. The performance of the device was tested with a contactless conductivity detector by separating different metal ions. In addition, nine metal cations related to the quality of honey were separated in 2.3 min and four honey samples were analysed quantitatively to demonstrate the applicability of the method. 相似文献
13.
This article deals with the various heat source responses in a transversely isotropic hollow cylinder under the purview of three-phase-lag (TPL) generalized thermoelasticity theory. In presence of magnetic field and due to the rotating behavior of the cylinder, the governing equations are redefined for generalized thermoelasticity with thermal time delay. In order to obtain the stress, displacement and temperature field, the field functions are expressed in terms of modified Bessel functions in Laplace transformed domain. When the outer radius of hollow cylinder tends to infinity, the corresponding results are discussed. Finally an appropriate Laplace transform inversion technique is adopted. 相似文献
14.
Yingying Wang Yang Zhou Min Lei Jinjun Hou Qinghao Jin Dean Guo Wanying Wu 《Tetrahedron》2019,75(9):1180-1185
A straightforward and general method has been developed for the synthesis of phthalimide derivatives from 2-iodobenzamides and PPh3/I2/HCOOH in the presence of a catalytic amount of Pd(OAc)2. The reaction results demonstrate that PPh3/I2/HCOOH is a facile, efficient and safe CO source. The whole process is carried out in toluene at 80?°C and furnishes the desired products in good to excellent yields. 相似文献
15.
An Ensemble Kalman Filter Approach Based on Level Set Parameterization for Acoustic Source Identification Using Multiple Frequency Information 下载免费PDF全文
In this paper, a reconstruction problem of the spatial dependent acoustic source from multiple frequency data is discussed. Suppose that the source function is supported on a bounded domain and the piecewise constant intensities of the source are known on the support. We characterize unknown domain by the level set technique. And the level set function can be modeled by a Hamilton-Jacobi system. We use the ensemble Kalman filter approach to analyze the system state. This method can avoid to deal with the nonlinearity directly and reduce the computation complexity. In addition, the algorithm can achieve the stable state quickly with the Hamilton-Jacobi system. From some numerical examples, we show these advantages and verify the feasibility and effectiveness. 相似文献
16.
利用具有同步辐射源的反射式飞行时间质谱仪,研究甲基环己烷的真空紫外光电离和光解离. 观测到母体离子C7H14+和碎片离子C7H13+,C6H11+,C6H10+,C5H10+,C5H9+,C4H8+,C4H7+和C3H5+的光电离效率曲线. 测定甲基环己烷的电离能为9.80±0.03 eV,通过光电离效率曲线确定其碎片离子的出现势. 在B3LYP/6-31G(d)水平上对过渡态、中间体和产物离子的优化结构进行表征,并使用G3B3方法计算其能量. 提出主要碎片离子的形成通道. 分子内氢迁移和碳开环是甲基环己烷裂解途径中最重要的过程. 相似文献
17.
氮化镓单晶衬底上的同质外延具有显著的优势,但是二次生长界面上的杂质聚集一直是困扰同质外延广泛应用的难题,特别是对电子器件会带来沟道效应,对激光器应用会影响谐振腔中的光场分布。本文通过金属有机化合物化学气相沉积(MOCVD)生长的原位处理,实现了界面杂质聚集的有效抑制。研究发现,界面上的主要杂质是C、H、O和Si,其中C、H、O可以通过原位热清洗去除;界面Si聚集的问题主要是由衬底外延片保存过程中暴露空气带来的,其次是氮化镓衬底中Si背底浓度,在外延过程中,生长载气对氮化镓单晶衬底不稳定的N面造成刻蚀,释放的杂质元素会对二次生长界面产生影响,本文较系统地阐明了界面杂质的形成机制,并提出了解决方案。 相似文献
18.
针对有机合成过程中碳及碳化物的残余,传统方法中普遍使用除碳的工艺,而很少有文章针对非晶碳的结构和形貌进行表征。为此,本文采用高尿素含量的前驱盐体系,通过在氮气保护气氛中煅烧获得AlN粉体。采用X射线衍射分析、红外和拉曼光谱分析、扫描电子显微镜和透射电子显微镜对850~1 500 ℃温度范围内煅烧获得产物的结构和形貌进行表征,对AlN合成过程中含碳产物结构形貌的变化,以及AlN和含碳产物之间相互的依存生长关系进行分析。结果表明,AlN生长的过程中伴随着无定形碳的石墨化转变,AlN颗粒的形貌也受含碳残余产物形貌的影响而出现有规律的变化。 相似文献
19.
A copper-catalyzed synthesis of methyl esters from aromatic aldehydes in the presence of tert-butyl hydrogen peroxide (TBHP) was developed via a radical reaction mechanism. TBHP acts not only as an efficient oxidant, but also as a green methyl source in such transformation. Moreover, this method could also be efficiently extended to the methyl esterification of benzylic alcohols. 相似文献
20.
We present an implementation of localization based three-dimensional super-resolution imaging on a regular microscope. We retain the original arc lamp as the photoactivation light source, and incorporate an inexpensive diode laser for imaging. As alterations to the standard microscope is minimal, this optical setup can be easily adapted in a typical research laboratory and even undergraduate teaching experiments, providing an inexpensive system for students and research scientists who require such super resolution capabilities. With this simple design, a spatial resolution of better than 40 nm at a reasonable frame rate has been achieved, adequate for most routine applications. 相似文献