A comparison of the field emission characteristics of vertically aligned graphene sheets grown on different SiC substrates

The field emission （FE） properties of vertically aligned graphene sheets （VAGSs） grown on different SiC substrates are reported. The VAGSs grown on nonpolar SiC （10-10） substrate show an ordered alignment with the graphene basal plane-parallel to each other, and show better FE features, with a lower turn-on field and a larger field enhancement factor. The VAGSs grown on polar SiC （000-1 ） substrate reveal a random petaloid-shaped arrangement and stable current emission over 8 hours with a maximum emission current fluctuation of only 4%. The reasons behind the differing FE characteristics of the VAGSs on different SiC substrates are analyzed and discussed.     

石墨烯基纳米复合物修饰印刷电极伏安法测定水中镉

构建了基于石墨烯(GS) -纳米金(Au)复合纳米微粒修饰印刷电极(SPCEs)的电化学传感器(SPCEs |GS/Au),建立了微分脉冲溶出伏安(DPSV)法测定水中痕量镉的电分析方法.采用扫描电镜(SEM)对电极表面进行了表征,DPSV法研究了镉的电化学性质.在优化实验条件下,溶出峰电流与Cd2+的质量浓度在2.5...     

Calculation of sound absorption characteristics of porous sintered fiber metal

Focusing its attention on porous sintered fiber metal, this paper presents a simple extended acoustical model on the basis of Biot-Allard model by using the idea of convective heat transfer in metallic tube for reference in order to calculate the sound absorption characteristics of porous sintered fiber metal. The sound absorption coefficients and the specific surface acoustic impedances of one-layer porous fiber metal sheets, two-layer-assembled and three-layer-assembled porous fiber metal sheets are calculated by using the extended and Biot-Allard model and then compared with the corresponding measured values. By comparing, it is shown that the theoretical results calculated by using the extended model fit the measured ones better. Finally, those above-mentioned results are further discussed and analyzed.     

Effects of total CH4/Ar gas pressure on the structures and field electron emission properties of carbon nanomaterials grown by plasma-enhanced chemical vapor deposition

The effects of total CH₄/Ar gas pressure on the growth of carbon nanomaterials on Si (1 0 0) substrate covered with CoO nanoparticles, using plasma-enhanced chemical vapor deposition (PECVD), were investigated. The structures of obtained products were correlated with the total gas pressure and changed from pure carbon nanotubes (CNTs) through hybrid CNTs/graphene sheets (GSs), to pure GSs as the total gas pressure changed from 20 to 4 Torr. The total gas pressure influenced the density of hydrogen radicals and Ar ions in chamber, which in turn determined the degree of how CoO nanoparticles were deoxidized and ion bombardment energy that governed the final carbon nanomaterials. Moreover, the obtained hybrid CNTs/GSs exhibited a lower turn-on field (1.4 V/μm) emission, compared to either 2.7 V/μm for pure CNTs or 2.2 V/μm for pure GSs, at current density of 10 μA/cm².     

Modulation of the crystallinity of hydrogenated nitrogen-rich graphitic carbon nitrides

An hydrogenated nitrogen-rich graphitic carbon nitride, structurally related to the theoretical graphitic phase of C₃N₄, has been synthesized in a bulk well-crystallized form. This new material was prepared by thermal decomposition of thiosemicarbazide up to 600 °C at ambient pressure under nitrogen flow. Its composition was determined by elemental combustion analysis. Powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and C¹³ MAS NMR characterizations were performed. This material can be schematically described with a two-dimensional framework and a composition close to C₃N_4.17H_1.12. In this nitrogen-rich material, C₃N₃ voids are fully occupied by water molecules which are strongly trapped into the material. A loss of crystallinity associated with a modification of the thermal behavior is observed when the amount of trapped molecules decreases in the graphitic material, order being damaged both between and in the graphitic planes.     

Graphitic carbon nitride C6N9H3·HCl: Characterisation by UV and near-IR FT Raman spectroscopy

The graphitic layered compound C₆N₉H₃·HCl was prepared by reaction between melamine and cyanuric chloride under high pressure-high temperature conditions in a piston cylinder apparatus and characterised using SEM, powder X-ray diffraction, UV Raman and near-IR Fourier transform Raman spectroscopy with near-IR excitation. Theoretical calculations using density functional methods permitted evaluation of the mode of attachment of H atoms to nitrogen sites in the structure and a better understanding of the X-ray diffraction pattern. Broadening in the UV and near-IR FT Raman spectra indicate possible disordering of the void sites within the graphitic layers or it could be due to electron-phonon coupling effects.     

氮掺杂碳片的模板诱导制备及其在超级电容器中的应用

兼具有优良的导电能力,高的比表面积和极佳的化学/机械稳定性,具有二维形貌的纳米碳材料近年来逐渐成为超级电容器电极材料的研究热点. 我们在此首次报道一种模板诱导方法以制备具有规整片状形貌的氮掺杂碳材料. 我们将作为硬模板的片状镁铝双金属氢氧化物与熔融的邻苯二胺混合后加入三氯化铁催化剂,进而通过加热使邻苯二胺聚合并碳化,随后刻蚀除去其中的氧化物成分即可以得到具有规整六边形片状氮掺杂碳材料. 通过改变碳化时的温度,可以有效的调节利用该方法所得到的氮掺杂碳片的形貌、结构、石墨化程度、氮含量以及比表面积. 更重要的是这些氮掺杂碳片在用作超级电容器电极材料时体现出优异的电化学性能,在0.5 A·g^-1的电流密度下其比容量可以达到290.0 F·g^-1的. 在1 A·g^-1的电流密度下经过10000周循环测试后,其容量仍然可以达到初始值83%.     

介孔氮化碳材料合成的研究进展

石墨相氮化碳(g-C₃N₄)是一种新型的无金属材料,因其具有众多特殊的理化性质,在多相催化、光催化、燃料电池和气体储存等领域显示出了潜在的应用前景。与直接热聚合法制得的块状g-C₃N₄相比,介孔g-C₃N₄拥有高比表面和丰富的介孔孔道,能暴露更多的表面活性位,继而提升其在催化反应等应用方面的性能。热聚合法是合成g-C₃N₄的最为便利的方法。其中,热聚合法合成介孔g-C₃N₄的工艺分为硬模板法、软模板法和无模板法。本文对近十年来国内外这三种合成工艺的研究进展进行了综述。特别是针对硬模板法,从前驱体合成机理、产品理化性质等多角度评述了硬模板法合成介孔g-C₃N₄的关键问题。此外,针对新型的软模板法和无模板法进行了介绍,并与硬模板法进行了细致的对比和讨论。最后,对介孔g-C₃N₄合成工艺的未来发展趋势进行了展望。     

Multi-solitons of Thermophoretic Motion Equation Depicting the Wrinkle Propagation in Substrate-Supported Graphene Sheets

The paper addresses the thermophoretic motion (TM) equation, which is serviced to describe soliton-like thermophoresis of wrinkles in graphene sheet based on Korteweg-de Vries (KdV) equation. The generalized unified method is capitalized to construct wrinkle-like multiple soliton solutions. Graphical analysis of one, two, and three-soliton solutions is carried out to depict certain properties like width, amplitude, shape, and open direction are adjustable through various parameters.     

1-辛基-3-甲基咪唑功能化石墨片负载氧化亚铜催化二氧化碳电还原制乙烯

电催化还原二氧化碳制备乙烯是备受关注的热点问题,高效催化剂的制备是决定乙烯产率的关键因素。本文在1-辛基-3-甲基咪唑氯的水溶液(OmimCl : H₂O = 1 : 5,体积比)中通过电剥离石墨棒制备了1-辛基-3-甲基咪唑功能化石墨片(ILGS),在水溶液中负载氧化亚铜后得到氧化亚铜/1-辛基-3-甲基咪唑功能化石墨片复合材料(Cu₂O/ILGS),通过透射电镜、X射线光电子能谱、拉曼光谱和X射线衍射对其组成和结构进行了系统研究,发现ILGS由多层石墨烯组成,表面富含缺陷。这些缺陷被1-辛基-3-甲基咪唑通过共价键修饰,形成类似鸟巢状的微结构,平均直径5 nm的Cu₂O纳米颗粒在石墨片表面均匀分散。在0.1 mol∙L⁻¹碳酸氢钾水溶液中,研究了Cu₂O/ILGS在不同电压下催化CO₂电还原的性能。结果表明,Cu₂O是主要活性中心并在CO₂还原过程中被逐渐还原成铜,导致产物的法拉第效率随着反应时间而变,在−1.3 V (vs RHE)电压下,乙烯的法拉第效率最高达到14.8%,其性能归因于Cu₂O/ILGS复合材料中的鸟巢状微结构对Cu₂O纳米颗粒的稳定作用。