Structural change of carbon nanotubes produced by Si ion beam irradiation

Multi-walled carbon nanotubes (MWCNTs) were irradiated by 40 keV Si ion beam with different doses. The structural change of the MWCNTs was revealed by transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The structural characterization after irradiation shows that the formation of amorphous carbon nanowires proceeds through two periods, carbon nanotube – semi-solid amorphous carbon nanowire with hollow structure – solid amorphous carbon nanowire. Based on the interaction between energetic particles and carbon nanotubes, the structural transformation process and corresponding mechanisms are discussed. A model is presented to illustrate the structural change of carbon nanotubes with increased irradiation dose.     

AFM and STM investigation of carbon nanotubes produced by high energy ion irradiation of graphite

Carbon nanotubes (CNT) were produced by high energy, heavy ion irradiation (215 MeV Ne, 246 MeV Kr, 156 MeV Xe) of graphite. On samples irradiated with Kr and Xe ions large craters were found by atomic force microscopy, these are attributed to sputtering. Frequently one or several CNTs emerge from the craters. Some of the observed CNTs showed a regular vibration pattern. No other carbon based materials, like amorphous carbon or fullerenes were evidenced. Focused ion beam cuts were used to compare CNTs with surface folds on graphite.     

离子辐照钨基上碳薄膜微结构的分析

对钨基材料表面上射频磁控溅射沉积的碳膜进行了氩离子和氮离子的辐照,并作了ＸＲＤ及ＸＰＳ的分析。分析结果表明,不同离子辐照引起碳膜微结构的变化亦不同,。氮离子辐照不仅使碳膜元素与基体元素发生混合,而且导致碳膜发生相变,生成碳－化合物,如α－Ｗ２Ｃ、ＷＣｘ,同时氮离子本身与反应生成氮－钨化合物,如ａ－ＷＮ。     

A molecular dynamics study of the clustering of implanted potassium in multiwalled carbon nanotubes

We have studied the low energy irradiation of carbon nanotubes (CNT) with K ions using classical molecular dynamics simulations with analytical potentials. The studied CNTs had diameters of about 0.5–1.2 nm and single or multiple walls. The average penetration depth and probabilities to introduce an impurity atom into CNT were studied with simulations on irradiating the CNT with single K ion. The number of potassium clusters, their average sizes and the damage produced into the CNT due to the irradiation were studied using multiple K ion irradiations. We found that the K ions are mobile in CNTs right after the implantation event and that they cluster together. For CNTs with 1–3 coaxial tubes, the highest ratio of K atoms in clusters per total number of K ions was obtained by using an irradiation energy of about 100 eV. Also the least damage per K ion was found to be produced into the CNT with this energy when those energies high enough for the ion to penetrate the outermost wall of the CNT were considered.     

碳家族一些成员在太赫兹波段的特性

利用近年新发展起来的太赫兹时域光谱技术(THz-TDS)研究了碳家族一些成员包括无定形碳、C60、石墨粉、单壁与多壁碳纳米管等的THz时域光谱特性,经过分析计算得到了样品的吸收系数及折射率的曲线.实验结果显示石墨、碳纳米管样品对THz波的吸收远大于无定形碳和C60,本文通过对石墨、碳纳米管和C60集体振动模式的分析,对实验结果进行了定性解释.     

Electron spin resonance investigations on ion beam irradiated single-wall carbon nanotubes

ESR investigations on single-wall carbon nanotubes irradiated with accelerated protons, helium ions, and neon ions are reported. All spectra were accurately simulated assuming that the resonance line is a convolution of up to 4 lines originating from catalyst residues, amorphous carbon, and electrons delocalized over the conducting domains of nanotubes. The faint line observed in irradiated nanotubes at g > 2.25 was assigned to magnetic impurities. However, there are no sufficient data to confirm that this line is connected to radiation-induced magnetism in carbon nanotubes. The generation of paramagnetic defects due to the bombardment of single-wall carbon nanotubes by accelerated ions is reported. These data correlate with previous Raman and thermal investigations on the same single-wall carbon nanotubes and reveals their sensitivity to ionizing radiation. The temperature dependence of ESR spectra in the range 25-250 K was used to identify the components of the ESR spectra.     

动态离子束混合技术制备氧化铬薄膜的X射线光电子能谱与俄歇电子能谱研究

本文介绍的动态离子束混合技术制备氧化铬薄膜系在不锈钢基体上进行1keV氩离子束溅射沉积铬(同时通入一定量的O),并用100 keV的氩离子束或氧离子束轰击该样品.对两种离子束轰击形成的氧化铬薄膜进行了X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)和俄歇电子能谱(Auger electron spectroscopy,AES)的分析研究.发现Ar 离子束制备的氧化铬薄膜主要是Cr2O3化合物,而O 离子束制备的氧化铬薄膜含有其它价态的铬氧化物.Ar 离子束制备氧化铬薄膜的污染碳少于O 离子束制备.与O 离子束制备相比较,相同能量的Ar 离子束轰击更有利于提高沉积的Cr原子与周围O2的反应性;Ar 离子束制备的氧化铬薄膜过渡层的厚1/3左右,较厚的过渡层显示了制备的薄膜具有较好的附着力.     

Behavior of carbon readsorbed on tungsten during low energy Ar ion irradiation at elevated temperatures

A study of the behavior of carbon sputtered and readsorbed after scattering collisions with particles of surrounding gas on the tungsten surface affected by Ar ion irradiation with the flux equal to 2 × 10¹⁶ cm⁻² s⁻¹ extracted from plasma under 300 V negative bias voltage in the temperature range 370-870 K was performed. The dependence of the W sample weight change on the working gas pressure in the range 0.1-10 Pa was registered and the information was deduced about prevailing sputtering-redeposition processes. The depth profiles of carbon at the tungsten surface were measured. We found that carbon distribution profiles in tungsten depend on the C redeposition rate for fixed ion irradiation parameters. Three regimes have been distinguished: (i) at working gas pressure equal to 5 Pa and more, the C redeposition rate prevails the sample surface erosion rate and the W surface is covered by continuous amorphous carbon film (the C film growth regime), (ii) at working gas pressure equal to about 1 Pa, the C redepostion rate is approximately equal to the erosion rate and the W surface is partially covered by redeposited carbon, and (iii) at working gas pressure less than 0.2 Pa, the erosion rate prevails the C redeposition rate (the W surface erosion regime). In the regime of balanced redeposition and erosion deep C penetration depth into nanocrystalline W was registered.It is suggested that under simultaneous C adsorption and ion irradiation at elevated temperature C adatoms are driven from the W surface into grain boundaries and into the bulk by the difference in chemical potentials between the activated W surface and grain boundaries. As the W surface is covered by amorphous C film, the grain boundaries are blocked and the efficiency of carbon transport decreases.     

Soft X-ray fluorescence measurements of irradiated polymer films

Fluorescent soft X-ray carbon Kα emission spectra (XES) have been used to characterize the bonding of carbon atoms in polyimide (PI) and polycarbosilane (PCS) films. The PI films have been irradiated with 40 keV nitrogen or argon ions, at fluences ranging from 1 × 10¹⁴ to 1 × 10¹⁶ cm⁻². The PCS films have been irradiated with 5 × 10¹⁵ carbon ions cm⁻² of 500 keV and/or annealed at 1000°C. We find that the fine structure of the carbon XES of the PI films changes with implanted ion fluence above 1 × 10¹⁴ cm⁻² which we believe is due to the degradation of the PI into amorphous C:N:O. The width of the forbidden band as determined from the high-energy cut-off of the C Kα X-ray excitation decreases with the ion fluence. The bonding configuration of free carbon precipitates embedded in amorphous SiC which are formed in PCS after irradiation with C ions or combined treatments (irradiation and subsequent annealing) is close to either to that in diamond-like films or in silicidated graphite, respectively.     

质子束轰击下MWCNTs无定形结构的转变

在室温下用70keV质子束多壁碳纳米管(MWCNTs),研究了多壁碳纳米管从石墨结构向无定形结构的转变过程。轰击后,MWCNTs外围的石墨结构变成均匀的无定形结构包覆着内部的石墨结构。增大照射量,这种无定形化的过程继续向MWCNTs内层推进,直至形成一个中空的无定形纳米线结构。质子束轰击引入的MWCNTs的结构转变,是从外层向内层逐步推进的石墨结构向无定形结构的转变过程。本文对这种结构演化的机理进行了讨论。     

Xe~+离子辐照诱导国产T91及316Ti钢微结构变化研究

对国产T91及316Ti钢进行室温下200keV的Xe~+离子辐照,使用X射线衍射(XRD)、透射电镜(TEM)等检测方法研究不同损伤剂量下辐照对材料相的稳定性和微观结构变化的影响。研究结果表明:T91钢辐照后未发生明显相变,而316Ti发生了γ(FCC)→α(BCC)的马氏体相变,且随辐照损伤剂量的增加,α相含量增加,相变的主要驱动力为辐照离子在辐照层的聚集从而产生的剪切应力;T91钢中的M_(23)C_6颗粒随辐照损伤剂量的增加,非晶化越来越明显,主要是由于辐照粒子的轰击削弱了M_(23)C_6颗粒晶格的稳定性,晶格塌陷成为非晶状态;316Ti钢在较低辐照损伤剂量(4.6dpa)下出现黑斑结构,而在高辐照损伤剂量(37.1dpa)下黑斑结构进一步聚集形成位错环。     

Phase changes of the ZrO2—12wt%Y2O3 film with Ar^＋ irradiation

1IntroductionYttrisistabilizedzirconiawithahighresistivityandalargerelativedielectricconstant.isaveryattractiveelectricalinsulator.11]Itcanbeusedforthefabricationofsilicon-oninsulator(SOI)structuresorasthebufferlayerinhighToceramicsuperconductorsonSttoavoidthereactionbetweenStandthesuperconductorfilm.[2]Thepolymorphicbehaviourofzirconiabasedceramicscontaininglessthan20wt%Yaosstillaffectsitsthermalshock-resistancewhenitisusedoveralargetemperaturerange.Ithasbeenfoundthatthereseemsacorrelesnon…     

硅中注入BF^＋2辐射损伤的反常行为

借助离子束背散射和沟道技术结合透射电子显微镜分析，研究了在３００Ｋ和７７Ｋ下硅中注入ＢＦ＾＋２辐射损的反常行国。结果发现ＢＦ＾＋２注入在硅中产生的损伤层或无定形层情况区别于其它较重离子注入。在３００Ｋ下注入时，硅中引入的两个损伤峰，其中一个位于离子入射的平均投影射程附近，另一个则在近表面，在７７Ｋ下注入时，硅中引入的损伤层或无定形层首先出现在表面，随注入剂量的增加，地锭形层向硅体内延伸。     

Radiation effects of pyrochlore-rich synroc by heavy-ion irradiation

Heavy-ion irradiation is commonly used to study radiation damage of high level radioactive waste (HLW) forms, but S ion was never used before. In this investigation, 100 MeV ^32S ions produced by tandem accelerator was used to study radiation effects on pyrochlore-rich synroc which contained simulated actinides. The amorphization and amorphous doses were determined by X-ray diffractometer (XRD) and transmission electron microscopy/select area electron diffraction (TEM/SAED). The vacancy defects induced by heavy-ion irradiation were characterized by using positron annihilation technique (PAT). The experimental results show that the amorphous dose is 0.5 dpa, the defects produced by heavy-ion irradiation are mainly voids, and irradiation could continue to intensify the vacancy defects even after the amorphous dose was reached.     

47MeV／u的C^6^＋在CaVSn：YIG中辐照效应的研究

用兰州重离子研究装置（ＨＩＲＦＬ）首次进行了４７ＭｅＶ／ｕ的Ｃ＾６＾＋离子辐照ＣａＶＳｎ：ＹＩＧ的实验。通过穆斯堡尔效应和正电子寿命测量对４７ＭｅＶ／ｕ的Ｃ＾６＾＋离子在ＣａＶＳｎ：ＹＩＧ中的辐照效应进行了初步研究。发现辐照导致内磁场方向趋于各向同性分布，由穆斯堡尔谱未观察到非晶化现象。缺陷的数量随Ｃ＾６＾＋离子在样品中电子能量损失的增加而增加。     

Production of Multiply-Charged Ions of Ne, Ar, Kr and Xe by the Electron-Bonbarded Hot Cathode IoN Source of IPCR

Production of multiply-charged ions of Ne, Ar, Kr and Xe has been studied by use of an electron-bombarded hot cathode type ion source of the IPCR 160cm cyclotron, which is similar to Morozov's source. These multiply-charged ions were accelerated by a 3rd harmonics acceleration mode in the cyclotron and detected with a beam probe fixed at the radius of 55cm. Observed multiply-charged ions are Ne2+, Ne3+, Ne4+, Ne5+, Ar3+, Ar4+ Ar5+, Ar6+, Ar7+, Ar8+, Kr6+, Kr7+, Kr8+, Kr9+, Xe9+, Xe10+ and Xe11+. Relative abundance of each charge state of four elements were measured. In case of Kr and Xe , the intensity of observed multiply-charged ions decreased to 1/3 or 1/4 when the charge number is increased by one. Intensities of Ar4+, Ar6+, Ar8+, Kr6+ and Kr8+ were measured as a function of the operation conditions of the ion source, such as arc voltage, arc power and gas flow rate. It was found that a smaller gas flow and a higher arc power brought about a higher yield in all the measured ions. Obtained current intensities of ion source output are 40?A Ar8+, 600?A Kr6+, 40?A Kr9+, 150?A Xe9+ and 10?A Xe11+ respectively.     

The irradiation variation of amorphous alloy FeSiB using for fusion devices induced by 2 MeV He ions

Because of its unique long range disordered structure and numerous free volume, amorphous alloy is considered to be able to accommodate the damage caused by ion bombardment and has good irradiation resistance. 2 MeV He~+ions were selected to irradiate amorphous alloy Fe80 Si7 B13, and it was found that the arrangement of atoms in the amorphous alloy became uneven. In the bubble layer located near the He ion range which was about 3.5 μm from the surface, the local atoms had a tendency of ordered arrangement. Under the irradiation, no obvious damage could be observed on the surface of the amorphous alloy, while the surface roughness increased, which reduced the surface relative reflectivity of the amorphous alloy. After the irradiation, the Fe-based amorphous alloy maintained the soft magnetic performance. The variation of atomic arrangement in the amorphous alloy enhanced its saturation magnetic induction intensity.     

高能Ar离子辐照PET膜引起的表面改性研究

采用傅立叶转换的红外光吸收技术在反射方式下分析研究了35MeV/u Ar离子辐照半晶质PET膜引起的表面改性及其对吸收剂量的依赖性。结果表明，辐照导致PET膜中与晶态区域相关的吸收带强度随吸收剂量增加普遍减弱，而与非晶区域相关的吸收带强度随吸收剂量增加逐渐增加，表明辐照使PET膜发生了非晶化转变。化学键断裂主要发生在苯环的对位和酯的C－O键上，而苯环的基本结构在整个辐照过程中变化较小。非晶化效应和化学键断裂同时依赖于离子的照射剂量和样品表面的电子能量沉积。此外，在约5．0MGy以上的吸收剂量，辐照还引起了炔端基团的形成，炔端基团浓度随吸收剂量的增加显著增加。对实验结果进行了定性解释。     

Ion beam induced amorphization and recrystallization of Si/SiC/Si layer systems

Epitaxial, buried silicon carbide (SiC) layers have been fabricated in (100) and (111) silicon by ion beam synthesis (IBS). In order to study the ion beam induced epitaxial crystallization (IBIEC) of buried SiC layers, the resulting Si/SiC/Si layer systems were amorphized using 2 MeV Si²⁺ ion irradiation at 300 K. An unexpected high critical dose for the amorphization of the buried layers is observed. Buried, amorphous SiC layers were irradiated with 800 keV Si⁺ ions at 320 and 600°C, respectively, in order to achieve ion beam induced epitaxial crystallisation. It is demonstrated that IBIEC works well on buried layers and results in epitaxial recrystallization at considerably lower target temperatures than necessary for thermal annealing. The IBIEC process starts from both SiC/Si interfaces and may be accompanied by heterogenous nucleation of poly-SiC as well as interfacial layer-by-layer amorphization, depending on irradiation conditions. The structure of the recrystallized regions in dependence of dose, dose rate, temperature and crystal orientation is presented by means of TEM investigations.     

Effect of p53 on lung carcinoma cells irradiated by carbon ions or X-rays

The study is to investigate the feasibility and advantages of heavy ion beams on radiotherapy. The cellular cycle and apoptosis, cell reproductive death and p53 expression evaluated with flow cytometry, clonogenic survival assays and Western blot analysis were examined in lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. The results showed that the number colonyforming assay of A549 was higher than that of H1299 cells in two radiation groups; A549 cellular cycle was arrested in G2/M in 12 h and the per-centage of apoptosis ascended at each time point of carbon ion radiation with doses, the expression of p53 upregulated with doses exposed to X-ray or carbon ion. The cell number in G2/M of H1299 and apoptosis were increasing at all time points with doses in 12C6+ ion irradiation group. The results suggested that the effects of carbon ions or X rays ir-radiation on lung carcinoma cells were different, 12C6+ ion irradiation could have more effect on upregulating the ex-pression of p53 than X-ray, and the upregulated expression of p53 might produce the cellular cycle G2/M arrested, apoptosis increasing; and p53 gene might affect the lung cancer cells radiosensitivity.