Sensitivities of two free vibration torsion pendulums

In this article, for the necessity of measuring the damping of new materials, a detailed comparison was made between two important free vibration torsion pendulums, that is, the inverted torsion pendulum and the Collette pendulum. Special attention was paid to the strong effect of the torsionally weak suspension in both pendulums on the difference between measured damping of the overall system and the real damping exclusively contributed by the investigated specimen. This difference was successfully quantitatively characterized by a parameter: the sensitivity of the pendulum only via which the accurate damping for the specimen can be determined for each case. The comparison showed that the sensitivities of the two systems obviously behave differently. Although it produces smaller performing strain amplitude on the specimen and has a narrower preset vibration frequency range, the sensitivity of the Collette pendulum is always lower than that of the inverted torsion pendulum. (C) 1996 American Institute of Physics

Kinetics of solid phase epitaxy of amorphous Si induced by self-ion implantation into Si with nanocavities

The solid phase epitaxial regrowth of structurally modified amorphous silicon created by self-ion implantation into nanovoided crystalline silicon is investigated. It is demonstrated that although the modified amorphous silicon is fully reconstructed into single crystal during the epitaxial regrowth, both activation energy and atom attempt frequency for the regrowth are much higher than those of the typical amorphous Si induced by self-ion implantation into Si wafer without nanovoids. The novel regrowth kinetics indicates that the modified amorphous silicon would contain a very high concentration of dangling bonds, which are believed to result from dissociation of the nanovoids originally metastablized in crystalline silicon. The unparalleled sensitivity of SPEG provides an effective and simple way to detect and characterize the subtle structural changes at nanometer scale in amorphous Si

电子束辐照下两种不同构型非晶SiO_x纳米线的不稳定性比较

室温下利用高分辨透射电子显微镜对比观察了两端固定和一端固定、另一端自由的非晶SiO_x纳米线在电子束辐照下的结构不稳定性。实验发现,在相同辐照条件下,两端固定的非晶SiO_x纳米线径向持续均匀收缩;一端固定、另一端自由的非晶SiO_x纳米线轴向长度持续快速收缩,而径向无明显变化。利用我们最近提出的非晶SiO_x纳米线表面纳米曲率效应和电子束诱导非热激活效应基础上发展的原子'融蒸'和'扩散'机制,对上述电子束辐照下非晶SiO_x纳米线结构不稳定现象进行了全新、合理的解释

Related Experiments and Their Analysis for Synthesizing of Several Representative Composite Nanowires

近年来,复合纳米线的制备成为低维纳米结构研究的一个热点。综述了几种典型复合纳米线的生长方法,分析了它们的生长机制,以及影响它们生长的各种因素。希望通过这几个制备复合纳米线的实验的分析与研究能对相关实验研究工作提供一些参考。In recent years, synthesis of composite nanowires has been a hot topic in field of low dimension nanostructure.Considerable efforts have been devoted to the synthesis of composite nanowires via different methods.There is,however,few found to systematially and critically review on the growth of composite nanowires.In this paper, it presents a systematical and critical review on growth methods,corresponding growth mechanism and the parameters that affects the nanowires,with an aim of providing some critical referenes for the related future experiment research.国家自然科学基金专项研究课题(90406024);; 国家自然科学基金(90401022);; 教育部科学技术研究重点项目(105099);; 厦门大学启动经费(XK0016);; 福建省科技计划项目(2005HZ1019

In situ observation of the instability of double-walled carbon nanotubes under electron beam irradiation

室温下利用高分辨透射电子显微镜原位观察了两端固定和一端固定、另一端自由的双壁碳纳米管在电子束辐照下的结构不稳定性.实验发现,在相同辐照条件下,两端固定的双壁碳纳米管首先径向持续均匀收缩,然后局部颈缩,最后在颈缩处断裂;一端固定、另一端自由的双壁碳纳米管轴向长度持续快速缩小,而径向收缩相对缓慢.我们利用最近提出的表面纳米曲率效应和能量束诱导非热激活效应基础上新发展的碳原子“融蒸“和“扩散“机制,对上述电子束辐照下双壁碳纳米管结构不稳定现象进行了全新、合理的解释.The structural instabilities of double-walled carbon nanotubes in two typical environments were investigated in situ by transmission electron microscopy at room temperature.The double-walled carbon nanotube with two fixed ends shrank uniformly in the radial direction,bent locally and finally broke.The double-walled carbon nanotube with one free capped end and the other fixed to a rope of nanotubes shrank quickly and continually in the axial direction and slowly in the radial direction.All experimental phenomena could be well accounted for by the vaporization and diffusion of carbon atoms driven by the surface nanocurvature effect and electron beam-induced athermal activation,which have been underestimated or neglected in existing theoretical descriptions and simulations.国家自然科学基金(11074207);国家重点基础研究发展计划(2007CB936603);教育部高等学校博士学科点专项科研基金(20100121110023);国家科技计划国际科技合作与交流专项(2008DFA51230)资

Nanocavity shrinkage and preferential amorphization during irradiation in silicon

We model the recent experimental results and demonstrate that the internal shrinkage of nanocavities in silicon is intrinsically associated with preferential amorphization as induced by self-ion irradiation. The results reveal novel thermodynamic nonequilibrium properties of such an open-volume nanostructure in condensed matter and also of covalently bound amorphous materials both at nanosize scale and during ultrafast interaction with energetic beam

均匀电子束辐照诱导多壁碳纳米管非晶化

室温下利用已经发展成熟的透射电镜原位观察技术,在均匀电子束辐照下对多壁碳纳米管(MWCNT)的非晶化过程进行研究。实验结果表明,在均匀电子束辐照下MWCNT内、外壁完整的石墨结构开始出现断裂或塌陷,即内层和外层优先开始非晶化,但是内层非晶化的速度明显更快。随着辐照时间的延长,非晶化逐渐由内、外表面向中间推进。同时,内壁断裂或塌陷形成的无定形碳开始向管的内部中空部分填充,而外壁非晶化的碳原子部分被融蒸到真空中。最终,无定形碳填满整个管的内部空间,导致MWCNT完全非晶化。另外,在整个过程中由于非晶化体积膨胀补偿,MWCNT的外径基本保持不变。利用在碳纳米管纳米曲率效应和能量束诱导非热激活效应基础上新发展的碳原子"融蒸"机制,对上述MWCNT的非晶化过程进行了全新、合理的解释。国家自然科学基金(11574255)福建省科技厅科技计划(合作)重点项目(2014I0016)国家重点基础科学研究计划(973计划)(2007CB936603)~

均匀电子束辐照诱导多壁碳纳米管非晶化

在室温下利用已经发展成熟的透射电镜原位观察技术,在均匀电子束辐照下对多壁碳纳米管(MWCNT)的非晶化过程进行了研究。实验结果表明,在均匀电子束辐照下MWCNT内、外壁完整的石墨结构开始出现断裂或塌陷,即内层和外层优先开始非晶化,但是内层非晶化的速度明显更快。随着辐照时间的增加,非晶化逐渐由内、外表面向中间推进。同时,内壁断裂或塌陷形成的无定形碳开始向管的内部中空部分填充,而外壁非晶化的碳原子部分被融蒸到真空中。最终,无定形碳填满整个管的内部空间,导致MWCNT完全非晶化。另外,我们发现在整个过程中因为非晶化体积膨胀补偿MWCNT的外径基本保持不变。我们利用在碳纳米管纳米曲率效应和能量束诱导非热激活效应基础上新发展的碳原子“融蒸”机制对上述MWCNT的非晶化过程进行了全新、合理的解释。国家自然科学基金(11574255);;福建省科技厅科技计划(合作)重点项目(2014I0016);;国家重点基础科学研究计划(973计划)(2007CB936603

Self-assembly of patterned copper films by small incident angle deposition

利用新发展的小入射角沉积(SIAd)技术在玻璃衬底上自组装制备了图案化金属铜膜.利用金相显微镜(MM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)/选区电子衍射(SAEd)/能量弥散X射线光谱仪(EdX)以及X射线衍射仪(Xrd)等技术对所制备的图案化金属铜膜进行了表征.通过分析对比SIAd和垂直入射沉积(nId)铜沉积物的形貌和结构差异,揭示了图案化金属铜膜的形成机理.In this paper, the small incident angle deposition (SIAD) technique to fabricate patterned copper films is developed.The fabricated patterned copper films are characterized by metallurgical microscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction.Analysis of morphological and structural differences between copper deposits formed by SIAD and normal incidence deposition reveals the formation mechanisms of the patterned copper films.常州大学自然科学基金(ZMF02020042); 国家科技计划国际科技合作与交流专项(2008DFA51230)资

Controllable surface modification of nanowires by focused-electron-beam-induced deposition of carbon

作为一种典型的准一维纳米材料,纳米线具有纳米材料所特有的小尺寸效应或纳米曲率效应,经表面修饰的纳米线一般具有不同于普通纳米线的特殊性质.利用实验室发展成熟的透射电子显微镜原位辐照技术,以透射电子显微镜中残留的有机气体分子为前驱体,成功地在纳米线表面可控沉积了非晶碳纳米颗粒和碳纳米棒,以及局域凸起的非晶碳膜并形成局域肿大的同轴结构.实验结果表明,该方法能够方便地通过控制聚焦电子束的束斑尺寸、辐照方式、辐照时间以及辐照位置等参数,在纳米线表面精确可控地沉积各种非晶碳纳米结构,从而实现纳米线的表面可控修饰.对聚焦电子束辐照下基于纳米线的各种碳纳米结构的可能沉积机理作了进一步地探索,并针对透射电子显微镜中如何减少因电子束辐照诱导非晶碳沉积造成的样品污染提出了几点建议.Surface-modified nanowires generally own some additional properties,and thus in this paper,the authors particularly studied the surface modification of nanowires via irradiation of focused electron beam in a Tecnai F-30 field emission transmission electron microscope (TEM).It was observed that controllable deposition of all kinds of amorphous carbon nanostructures,such as carbon particles,carbon rods and carbon films with local bulging,could be got on the surface of nanowires after intentional irradiation.In details,the controllable deposition of carbon nanostructures could be easily and precisely controlled by changing of some irradiation parameters such as beam spot diameter,irradiation manner,irradiation time and irradiation position.The possible deposition mechanisms of carbon nanostructures on the wire surface as induced by irradiation of focused electron beam in TEM were further discussed.In addition,some suggestions were also proposed on reducing of specimen pollution caused by undesired deposition of amorphous carbon materials during the irradiation.国家科技计划国际科技合作与交流专项(编号:2008DFA51230);国家重点基础研究发展计划(编号:2007CB936603);国家自然科学基金(批准号:90401022;60776007);中澳科技合作特别基金(编号:20050222);教育部科技研究重点项目(编号:105099)资