超声波处理高序石墨合成碳纳米结构

用超声波处理水溶液中的高序石墨固体,借助于高分辨透射电子显微镜和电子衍射,不但看到了与电弧放电和激光烧蚀产物相似的碳纳米多面体和纳米管,而且还发现了一种罕见的实心碳纳米球.对这种由扰动石墨晶格组成物的形成过程给出一种可能的模型解释 关键词： 高序石墨 超声波处理 碳纳米结构     

激光干涉结晶技术制备二维有序分布纳米硅阵列

利用结合移相光栅掩模 (PSGM) 的激光结晶技术在超薄a-SiN_x/a-Si:H/ a-SiN _x三明治结构样品中制备出二维有序分布的纳米硅阵列.原始样品是用等离子体 增强化学气相淀积法生长.a-Si:H层厚为10nm，a-SiN_x 为50nm，衬底材料为SiO ₂/Si或 熔凝石英.原子力显微镜、剖面透射电子显微镜、高分辨透射电子显微镜对样品表面形貌和 微结构的观测结果表明，采用该方法可以在原始淀积的a-Si:H层中得到位置可控的晶化区域 ：每个晶化区域直径约250nm，具有同PSGM一致的2μm周期；晶化区域内形成的纳米硅 颗粒尺寸接近原始淀积的a-Si:H层厚，且晶粒的择优取向为<111>. 关键词： 纳米硅 激光结晶 定域晶化 移相光栅     

SiC纳米棒的紫外发光研究

采用聚硅氮烷前驱体在高温常压下热裂解的方法制备了3C-SiC纳米棒,在室温下观察到来自纳米棒的378 nm（33?eV） 强紫外发射. 利用扫描电子显微镜、透射电子显微镜、高分辨透射电子显微镜和X射线衍射对样品的形貌和结构进行表征,观察到在该结构中存在类似6H-SiC结构的三层堆垛层错. 利用室温荧光光谱和室温荧光衰减曲线研究了强紫外发射的产生机理,紫外发射来源于3C-SiC纳米棒中的三层堆垛层错的发光. 关键词： 碳化硅 纳米棒 光致发光     

一种制备巴基葱的新方法纳米碳化硅高温真空热分解法

实验发现，通过真空热处理碳化硅纳米粉末可以获得巴基葱.透射电子显微镜和高分辨电子显微镜观测表明，当碳化硅完全分解时，形成空心准球状颗粒和葱状石墨颗粒；当碳化硅分解不完全时，形成碳包裹碳化硅结构，该包裹层由准同心石墨壳层构成.由实验结果知，认为平面结构是石墨的最稳定形式的传统观点是值得讨论的. 关键词：     

磁控溅射法合成纳米β-FeSi2/a-Si多层结构

β-FeSi₂作为一种环境友好的半导体材料，颗粒化及非晶化正在成为提高其应用性能和改善薄膜质量、膜基界面失配度的有效途径.利用射频磁控溅射法在单晶Si基体上沉积Fe/Si多层膜，合成纳米β-FeSi₂/Si多层结构.通过透射电子显微镜、高分辨电子显微术等分析手段，研究了多层结构和制备工艺之间的相互关系.研究结果表明，采用磁控溅射Fe/Si多层膜的方法，不需要退火就可以直接沉积得到β-FeSi₂相小颗粒.β-FeSi₂相 关键词： 2')" href="#">β-FeSi₂ 磁控溅射 透射电子显微镜 半导体薄膜     

AlN/Si3N4纳米多层膜的外延生长与力学性能

采用射频磁控溅射方法制备单层AlN, Si₃N₄薄膜和不同调制周期的AlN/Si₃N₄纳米多层膜.采用X射线衍射仪、高分辨透射电子显微镜和纳米压痕仪对薄膜进行表征.结果发现,多层膜中Si₃N₄层的晶体结构和多层膜的硬度依赖于Si₃N₄层的厚度.当AlN层厚度为4.0nm、 Si₃N₄层厚度 关键词： 3N₄纳米多层膜')" href="#">AlN/Si₃N₄纳米多层膜 外延生长 应力场 超硬效应     

TiN/Al2O3纳米多层膜的共格外延生长及超硬效应

采用多靶磁控溅射法制备了一系列具有不同Al₂O₃调制层厚度的TiN/Al₂O₃纳米多层膜. 利用X射线能量色散谱、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和微力学探针表征了多层膜的成分、微结构和力学性能. 研究结果表明，在TiN/Al₂O₃纳米多层膜中，单层膜时以非晶态存在的Al₂O₃层在厚度小于1.5 nm时因TiN晶体层的模板效应而晶化，并与TiN层形成共格外延生长，相应地，多层膜产生硬度明显升高的超硬效应，最高硬度可达37.9 GPa. 进一步增加多层膜中Al₂O₃调制层的层厚度，Al₂O₃层逐渐形成非晶结构并破坏了多层膜的共格外延生长，使得多层膜的硬度逐步降低. 关键词： 2O₃纳米多层膜')" href="#">TiN/Al₂O₃纳米多层膜 外延生长 非晶晶化 超硬效应     

40Ar+诱导无定形碳到金刚石纳米晶相变的研究

通过60 keV的⁴⁰Ar⁺辐照无定形碳靶合成了大量尺寸不同的金刚石纳米颗粒.高分辨透射电子显微镜配合能量色散X射线谱和电子衍射以及Raman谱分析的结果表明，这些嵌于具有扰动石墨结构薄膜中的纳米金刚石颗粒，其成核率很高(约为10¹³/cm²)，而且可以生长到较大的尺寸，有的甚至可以达到微米量级.对其相转变过程也进行了初步探讨. 关键词： 离子束 金刚石纳米晶 相变 透射电子显微镜     

Ar+离子束轰击在石墨表面形成六方金刚石纳米晶的研究

在0.6keV Ar⁺高剂量(～10²²/cm²)辐照石墨表面,借助于高分辨透射电子显微镜(HRTEM),发现有六方金刚石纳米晶产生.它们的平均直径介于1—50nm之间,而且晶粒个数约随其直径的增大而直线减少.有趣的是,晶粒具有两种结构模式：直径小于10nm的晶粒为单晶结构,而直径大于10nm的为多晶结构.基于受离子轰击过程特点制约的六方金刚石晶粒成核和成长观点,讨论了这种双重结构的形成性质. 关键词： 离子轰击 六方金刚石纳米晶     

SiO2的赝晶化及AlN/SiO2纳米多层膜的超硬效应

采用反应磁控溅射法制备了一系列不同SiO₂层厚度的AlN/SiO₂纳米多层膜，利用X射线衍射仪、高分辨透射电子显微镜和微力学探针表征了多层膜的微结构和力学性能，研究了SiO₂层在多层膜中的晶化现象及其对多层膜生长方式及力学性能的影响. 结果表明，由于受AlN六方晶体结构的模板作用，溅射条件下以非晶态存在的SiO₂层在其厚度小于0.6 nm时被强制晶化为与AlN相同的六方结构赝晶体并与AlN形成共格外延生长. 由于不同模量的两调制层存在晶格错配度，多层膜中产生了拉、压交变的应力场，使得多层膜产生硬度升高的超硬效应. SiO₂随层厚的进一步增加又转变为以非晶态生长，多层膜的外延生长结构受到破坏，其硬度也随之降低. 关键词： 2纳米多层膜')" href="#">AlN/SiO₂纳米多层膜 赝晶化 应力场 超硬效应     

Fabrication of graphene nanostructures by probe nanoablation

We present the results of the study of graphene nanoablation under mechanical stress of an ultrasharp (the rounding radius is ～2 nm) tip of a scanning probe microscope (SPM)). It was found that the SPM probe contact with graphene results in average removal of 7 · 10^?3?5 · 10^?2 nm of film per scan, i.e., only a few carbon atoms or clusters, in the impact area. The capability of this precision nanoablation process was shown in developing graphene nanoislands and nanoribbons ～1 µm long and ～10 nm wide.     

Using sonochemistry for the fabrication of hollow ZnO microspheres

Hollow ZnO microspheres assembled by nanoparticles have been prepared by a sonochemical synthesis at room temperature using carbon spheres as template. The growth process of the precursor was investigated. The prepared hollow spheres were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM). The diameter of the obtained hollow spheres is about 500 nm, and the walls are composed of numerous ZnO aggregate nanocrystallines with diameters of 90 nm. A possible growth mechanism for the formation of ZnO microspheres has been proposed, in which carbon spheres play a crucial role in the formation of the wurtzite hollow ZnO microspheres. The specific structure of the hollow spheres may find applications in nanoelectronics, nanophotonics and nanomedicine.     

Luminescence and structure of nanosized inclusions formed in SiO2 layers under double implantation of silicon and carbon ions

Luminescent and structural characteristics of SiO₂ layers exposed to double implantation by Si⁺ and C⁺ ions in order to synthesize nanosized silicon carbide inclusions have been investigated by the photoluminescence, electron spin resonance, transmission electron microscopy, and electron spectroscopy methods. It is shown that the irradiation of SiO₂ layers containing preliminary synthesized silicon nanocrystals by carbon ions is accompanied by quenching the nanocrystal-related photoluminescence at 700–750 nm and by the enhancement of light emission from oxygen-deficient centers in oxide in the range of 350–700 nm. Subsequent annealing at 1000 or 1100°C results in the healing of defects and, correspondingly, in the weakening of the related photoluminescence peaks and also recovers in part the photoluminescence of silicon nanocrystals if the carbon dose is less than the silicon dose and results in the intensive white luminescence if the carbon and silicon doses are equal. This luminescence is characterized by three bands at ～400, ～500, and ～625 nm, which are related to the SiC, C, and Si phase inclusions, respectively. The presence of these phases has been confirmed by electron spectroscopy, the carbon precipitates have the sp ³ bond hybridization. The nanosized amorphous inclusions in the Si⁺ + C⁺ implanted and annealed SiO₂ layer have been revealed by high-resolution transmission electron microscopy.     

Crystallographic aspects related to the high pressure–high temperature phase transformation of boron nitride

Crystallographic relations between different forms of boron nitride (BN) appearing at the high pressure–high temperature structural phase transformation have been revealed by high-resolution transmission electron microscopy (HRTEM). As starting materials, crystalline hexagonal BN (hBN) with different degrees of crystallinity, or with defects intentionally introduced, were used. Cubic BN (cBN) is formed only as a minor component, the rest consisting of different forms of sp ² bonded BN: hBN, compressed, monoclinic deformed hBN, or turbostratic BN (tBN). The small cBN crystallites (300–400?nm) contain many defects such as twins, stacking faults and nanoinclusions of other BN forms: tBN, rhombohedral BN (rBN) and wurtzite BN (wBN). The cBN phase grows epitaxially on the basal plane of hBN. The nucleation sites for cBN are revealed by HRTEM. They consist of nanoarches (sp ³ hybridized, highly curved nanostructures), frequently observed at the edges of the hBN crystallites in the starting materials. Based on HRTEM observations of specimens not fully transformed, a nucleation and growth model for cBN is proposed which is consistent with existing theoretical and experimental models.     

Carbon nanowire made of a long linear carbon chain inserted inside a multiwalled carbon nanotube

A new type of one-dimensional (1D) carbon structure, carbon nanowires (CNWs), was discovered in the cathode deposits prepared by hydrogen arc discharge evaporation of carbon rods. Observation of high-resolution transmission electron microscopy (HRTEM) indicates that a CNW consists of a multiwalled carbon nanotube (MWNT) with a long 1D linear carbon chain (C chain) inserted into its innermost tube of 0.7 nm in diameter. The characteristic Raman peaks of CNWs appeared at around 1850 cm(-1). Raman scattering and HRTEM studies show the formation of a long linear C chain involving more than 100 carbon atoms inside a MWNT. This novel 1D carbon allotrope has potential applications in nanoelectronics, nanomechanics, and nanomaterials.     

Zinc oxide catalyzed growth of single-walled carbon nanotubes

We demonstrate that zinc oxide can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency by a chemical vapor deposition process. The zinc oxide nanocatalysts, prepared using a diblock copolymer templating method and characterized by atomic force microscopy (AFM), were uniformly spaced over a large deposition area with an average diameter of 1.7 nm and narrow size distribution. Dense and uniform SWNTs films with high quality were obtained by using a zinc oxide catalyst, as characterized by scanning electron microscopy (SEM), Raman spectroscopy, AFM, and high-resolution transmission electron microscopy (HRTEM).     

Microstructure and composition of catalytic layers formed by the ion-beam-assisted deposition of platinum onto carbon substrates

The results of investigating the microstructure and composition of layers formed by platinum deposition onto carbon carriers used as electrocatalysts—MG-1 graphite, SU-2000 glassy carbon, and AVCarb® P50 carbon fiber paper—are presented. The layers have been created via the ion-beam-assisted deposition of platinum, in which metal deposition and mixing between the deposited layer and substrate-surface atoms accelerated by ions of the same metal (U = 10 kV) occur, respectively, from a neutral vapor fraction and the vacuum-arc discharge plasma of a pulsed ion source. The layers are examined via scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction, Rutherford backscattering spectrometry, and X-ray photoelectron spectrometry. The formed layers (their thicknesses are ～100 nm and the platinum content is ～10¹⁶ atom cm^?2) are characterized by an amorphous atomic structure that repeats the surface microstructure of the carbon carrier.     

Synthesis of multi-wall carbon nanotubes by the pyrolysis of ethanol on Fe/MCM-41 mesoporous molecular sieves

Ordered hexagonal arrangement MCM-41 mesoporous molecular sieves were synthesized by the traditional hydrothermal method, and Fe-loaded MCM-41 mesoporous molecular sieves (Fe/MCM-41) were prepared by the wet impregnation method. Their mesoporous structures were testified by X-ray diffraction (XRD) and the N₂ physical adsorption technique. Carbon nanotubes (CNTs) were synthesized by the chemical vapor deposition (CVD) method via the pyrolysis of ethanol at atmospheric pressure using Fe/MCM-41 as a catalytic template. The effect of different reaction temperatures ranging from 600 to 800 ^°C on the formation of CNTs was investigated. The resulting carbon materials were characterized by various physicochemical techniques such as transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The results show that multi-wall carbon nanotubes (MWCNTs) with an internal diameter of ca. 7.7 nm and an external diameter of ca. 16.9 nm were successfully obtained by the pyrolysis of ethanol at 800 ^°C utilizing Fe/MCM-41 as a catalytic template.     

Hardening and thermal stability of nanocrystalline AlMg4.8 powder

Ball milled nanocrystalline AlMg4.8 powder was investigated in terms of hardening and thermal stability. The validity of the Hall–Petch relation was confirmed down to the minimum grain size of ～44 nm. Prolonged milling in the range of the minimum grain size still increased the hardness. This development is discussed in terms of contamination effects and the influence of full and partial dislocations. Concerning thermal stability, recovery processes occur in the range of 100–230°C, whereas substantial grain growth starts at a temperature of ～250°C. The enthalpy release for recovery was detected to be ～39 J mol^?1 and ～208 J mol^?1 for grain growth. Dynamic strain ageing was indicated by an activation energy for recovery of Q?～?120 kJ mol^?1. The activation energy of grain growth was calculated by means of the Kissinger theory (Q?=?200–210 kJ mol^?1) and using the results of static grain growth (Q?=?204 kJ mol^?1).