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.     

圆环形截面碳化硅纤维管的辐射化学法合成

为制备碳化硅(Silicon carbide,SiC)纤维管,本研究利用10MeV电子直线加速器产生的高能电子束在空气中辐照聚碳硅烷(Polycarbosilane,PCS)先驱丝。研究了辐照工艺、热处理温度、吸收剂量对制备SiC纤维管的影响,并运用红外光谱分析对SiC纤维管的辐射制备机理作了初步探讨。结果表明,合适的辐照工艺为每次定点辐照20s,停车冷却5min;最佳热处理温度为350℃;红外光谱分析表明,空气中的氧通过与PCS中的Si-H、Si-CH3反应而被引入到辐照产物中,形成了Si-OH和C=O结构;在经热处理的先驱丝中有Si-O-Si,Si-C-Si等桥联结构生成;吸收剂量介于2.0-3.5MGy之间的PCS先驱丝均能制得SiC纤维管,且管壁厚度随着吸收剂量的增加而逐渐增加。     

预处理温度对聚碳硅烷粒子炉内成球性的影响

本文以聚碳硅烷(PCS)为原料,采用炉内成球技术制备直径200~400μm、壁厚3~5μm的SiC空心微球,探讨微球制备的最佳条件,并在此基础上研究不同预处理温度对PCS成球产率及品质的影响。结果表明,炉内载气温度为500℃、He与Ar比例为3∶1时PCS的成球产率较高,且微球的球形度、同心度、表面光洁度均最好。此外,由于预处理过程去除了PCS中的低分子量聚碳硅烷和其他小分子,同时使其聚合度升高,提高了PCS的热稳定性和陶瓷化产率。因此,在最佳炉内成球条件下,PCS的成球率随预处理温度的升高而升高,所得微球的表面粗糙度却随之降低。经350℃预处理后的PCS粒子成球率最高,且微球的球形度和表面质量最佳。     

锆合金包壳水侧SiC涂层研究

研究了聚碳硅烷（PCS）粉末的高温裂解特性及PCS粉末与锆粉间的化学反应机理,并在900 ℃制备了SiC涂层。研究发现,900 ℃开始,PCS裂解产物由无定形态SiC向结晶态转变。不同温度下,PCS粉末与锆粉的混合物发生一系列化学反应,产物为ZrC、Zr₂Si、Si₃Zr₅,通过调节反应温度,可控制该化学反应的程度,进而实现对涂层成分的调节。采用先驱体转化法（PIP）在锆合金包壳表面制备了SiC涂层,经PCS溶液浸涂-裂解3次循环可得到SiC陶瓷层,厚度为4 μm,涂层成分为SiC,ZrC为过渡层。划痕法测试得到涂层附着力等级为1～2级。     

Determination of stoichiometry in silicon carbide materials using elastic backscattering spectrometry

Elastic backscattering spectrometry (EBS) was performed on SiC materials, using ⁴He particles at energies ranging from 2 to 4 MeV, in order to establish the energy values that lead to an accurate measurement of the Si/C ratio. Analysis of the random yield of “bulk” SiC single crystals indicates that energy values of 3.25 and 3.75 MeV are the most suitable for chemical composition determination; backscattering yield of carbon is enhanced compared to the yield measured at 2 MeV, while the excitation of strong resonances above 3.75 MeV are suppressed. Random backscattering yield measurements were then carried out at an energy of 3.25 MeV on unhydrogenated SiC thin films grown on Si(1 0 0), by pulsed laser deposition, at different substrate temperatures. The Si and C atomic concentrations in the films were determined with an uncertainty of 1% and little interference from the underlying substrate. The films were found to be stoichiometric with a Si/C ratio of 1.03 ± 0.05, independent of deposition temperature, which indicates that the films were grown under congruent ablation conditions. The analysis proved to be applicable to both amorphous and crystalline SiC layers, as confirmed by the results obtained for films deposited at 400 and 950 °C, respectively.     

Atomic mixing at metal–oxide interfaces by high energy heavy ions

We study the atomic mixing at metal (Bi or Au)/oxide (SiO₂ or Al₂O₃) interfaces under 150–200 MeV heavy ion irradiation. Irradiation-induced interface mixing state is examined by means of Rutherford backscattering spectrometry (RBS). For Bi/Al₂O₃ interfaces, the heavy ion irradiations induce a strong atomic mixing and the amount of the mixing increases with increasing the electronic stopping power for heavy ions. By comparing the results with that for 3 MeV Si ion irradiation, we conclude that the strong atomic mixing observed at Bi/Al₂O₃ interfaces is attributed to the high-density electronic excitation. On the other hand, for other interfaces (Bi/SiO₂, Au/Al₂O₃ and Au/SiO₂), atomic mixing is rarely observed after the irradiation. The dependence of atomic mixing on combinations of irradiating ions and interface-forming materials is discussed.     

Xenon-ion-beam modifications of a-SiO2 and Ni/a-SiO2 layers

Modifications of a-SiO₂ films and Ni/a-SiO₂ bilayers by irradiations with 90–350 keV Xe ions have been investigated. The effects of subsequent thermal annealings in vacuum at 298–1173 K have also been studied. The analyses were performed by means of Rutherford Backscattering Spectrometry and surface profilometry. We here report on the results of ion-beam induced surface roughening and sputtering and of the noble-gas collection curves. As to the athermal ion-beam mixing at the Ni/a-SiO₂ interface, a low mixing rate in agreement with the ballistic model was observed. Only little Xe precipitation, which would indicate the presence of end-of-range spikes, occurs at the interface. Most effects were found to strongly depend on the implanted ion fluence.     

C60薄膜在快重离子辐照下的结构稳定性研究

用傅立叶变换红外光谱、X射线衍射谱、X射线光电子谱和拉曼散射技术分析了能量为GeV量级的S、Fe、Xe、和U离子,以及120keV的H离子在室温下辐照多层堆积C60薄膜的结构稳定性,即快重离子在C60薄膜中由高密度电子激发引起的效应,主要包括C60分子的聚合、分子结构的损伤、新的高温-高压相的形成和晶态向非晶态的转变.     

基于单一气源的PECVD方法制备SiC薄膜及其微观结构研究

为制备出满足惯性约束聚变（ICF）实验要求的SiC薄膜,本文采用等离子体增强化学气相沉积（PECVD）法,以四甲基硅（TMS）作为唯一反应气源,在不同工作压强下制备SiC薄膜。利用扫描电子显微镜、表面轮廓仪、原子力显微镜、精密电子天平、X射线光电子能谱、傅里叶变换红外光谱对薄膜进行表征与分析。结果表明：SiC薄膜的成分与工作压强密切相关,随着工作压强的增加,薄膜中Si含量整体呈下降趋势;随着工作压强的增加,薄膜沉积速率先增大后减少,密度先减小后增大;与其他制备工艺相比,采用单一气源制备SiC薄膜,其表面粗糙度极低（1.25～1.85 nm）,薄膜粗糙度随工作压强的增加呈先增大后减小的趋势。     

Structure dependent electronic sputtering of a-C:H films by swift heavy ions

Electronic sputtering of a-C:H films by elastic recoil detection analysis technique is studied under 80 MeV Ni⁸⁺ and 150 MeV Ag¹³⁺ ion irradiations. These studies show that electronic sputtering yield of C and H from the films varies with film structure quite significantly. The structure of the films is analyzed from the characteristic graphitic (G) and disordered (D) modes of Raman vibration. Atomic force microscopy was performed on two films for grain size determination. The difference in electronic sputtering yields is discussed on the basis of structural influence of the films on swift heavy ion and solid interaction.     

Structural changes in anatase TiO2 thin films irradiated with high-energy heavy ions

In order to investigate possible structural changes due to high-density electronic excitation, anatase TiO₂ thin film specimens were irradiated with 230 MeV ¹³⁶Xe¹⁵⁺ ions and 200 MeV ¹⁹⁷Au¹³⁺ ions. X-ray diffraction (XRD) patterns were measured before and after irradiation. The intensity of the XRD peak assigned to the (0 0 4) planes of anatase TiO₂ decreases in an exponential manner as a function of ion-fluence. This result can be explained by the formation of the cylindrical damaged regions (i.e. ion tracks) with diameters of 9.6 and 16.3 nm for 230 MeV Xe and for 200 MeV Au ion irradiations, respectively. The difference in the track diameter between Xe ion irradiation and Au ion irradiation can be attributed to the difference in the electronic stopping power (and to the ion-velocity effect, if any). For 200 MeV Au ion irradiation, splitting of the (0 0 4) peak is observed. The original (0 0 4) TiO₂ peak remains in the same position, but the new peak shifts to higher angles as fluence increases.     

Physical and chemical sputtering of graphite and SiC by hydrogen and helium in the energy range of 600 to 7500 eV

The erosion of pyrolytic graphite and silicon carbide due to the bombardment with monoenergetic hydrogen ions with energies of 600 to 7500 eV has been investigated in the temperature range of near room temperature to 750°C. The erosion yield of SiC is about 10^?2 and shows no pronounced temperature dependence. In contrast to SiC the erosion yield of pyrolytic graphite shows a maximum at a temperature of about 600°C. The ratio of the maximum erosion yield to that at room temperature depends on the energy of the hydrogen ions and increases from about 11 at 3000 eV to 32 at 670 eV. The production of CH₄ during the bombardment of the graphite has been found proportional to the erosion yield. When graphite was bombarded with He ions no hydrocarbon production and no temperature dependence of the erosion yield could be observed. The results are compared with values for the erosion yields of carbon by thermal atomic hydrogen taken from literature.     

HTR fuel coating separate effect test PYCASSO

The “analytical” PYCASSO (PYrocarbon irradiation for Creep and Swelling/Shrinkage of Objects) irradiations focus on determining the effects of neutron irradiation in the temperature range of 900-1100 °C, excluding effects due to the presence of fuel, such as pressurization or chemical attack by fission products. These irradiations can therefore be considered separate effect tests, where only the influence of neutron fluence and temperature on coatings and coating combinations is investigated.For this purpose dedicated particles have been manufactured consisting of surrogate kernels (ZrO₂ and Al₂O₃) with different types of PyC/SiC/ZrC coatings and coating combinations. All specimens delivered have been extensively characterized, such that even potentially small changes due to the irradiation in dimensions, microstructure and density can be determined accurately after irradiation.Partners involved in this irradiation are CEA (France), JAEA (Japan) and KAERI (South Korea). The PYCASSO irradiations take place in the High Flux Reactor (HFR) in Petten, and are coordinated by NRG (The Netherlands). The partnership for PYCASSO was initiated by the RAPHAEL (V)HTR European 6th Framework Program and is integrated in the Generation IV International Forum VHTR Fuel and Fuel Cycle project.     

γ射线辐照改性聚碳硅烷提高热解陶瓷产率

在N2气中用γ射线对聚碳硅烷(Polycarbosilane,PCS)进行辐照,利用傅里叶红外光谱分析、凝胶渗透色谱分析和热重分析等手段研究了不同吸收剂量下PCS的化学结构、分子量和热分解特性。结果显示,经γ射线辐照处理后的PCS轻微失重,分子量和软化点随着吸收剂量的增加而增加,说明PCS经辐照后发生了分子间的交联反应。红外分析表明,PCS的交联主要是通过Si-H键和C-H键的断裂产生新的Si-C-Si结构实现的。热重分析表明,PCS热解为碳化硅的陶瓷产率随吸收剂量的增加显著升高,剂量达到1.5 MGy后PCS样品的陶瓷产率基本提高到稳定值,此时,陶瓷产率从改性前的61.9%提高到80.0%。     

Effects of MeV Si ions bombardment on the thermoelectric generator from SiO2/SiO2 + Cu and SiO2/SiO2 + Au nanolayered multilayer films

The defects and disorder in the thin films caused by MeV ions bombardment and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of an inelastic interaction and phonon annihilation. We prepared the thermoelectric generator devices from 100 alternating layers of SiO₂/SiO₂ + Cu multi-nano layered superlattice films at the total thickness of 382 nm and 50 alternating layers of SiO₂/SiO₂ + Au multi-nano layered superlattice films at the total thickness of 147 nm using the physical vapor deposition (PVD). Rutherford Backscattering Spectrometry (RBS) and RUMP simulation have been used to determine the stoichiometry of the elements of SiO₂, Cu and Au in the multilayer films and the thickness of the grown multi-layer films. The 5 MeV Si ions bombardments have been performed using the AAMU-Center for Irradiation of Materials (CIM) Pelletron ion beam accelerator to make quantum (nano) dots and/or quantum (quantum) clusters in the multilayered superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after Si ion bombardments we have measured Seebeck coefficient, cross-plane electrical conductivity, and thermal conductivity in the cross-plane geometry for different fluences.     

Swift heavy ion induced magnetic phase transition of Fe–Rh alloy

We report the effects of swift heavy ion irradiation on structure and magnetic properties of Fe–50at.%Rh alloys. The alloys are irradiated with 120–200 MeV heavy ions (Ni, Kr or Xe) at room temperature. Before and after the irradiations, the magnetization and the lattice parameter are measured by using superconducting quantum interference device (SQUID) and X-ray diffractometer (XRD), respectively. The lattice parameter at room temperature increases by about 0.3% and antiferromagnetic–ferromagnetic transition temperature decreases below 5 K by the irradiations. Effects of electronic excitation due to swift heavy ions on the change in magnetic properties and lattice structure are discussed.     

Irradiation of Polystyrene and Polypropylene to study NIH 3T3 fibroblasts adhesion

When polymers are irradiated with heavy ions new chemical groups are created in a few microns of the material. The irradiation changed the polarity and wettability on the surface so that could enhance the biocompatibility of the modified polymer. The study of chemistry and nanoscale topography of the biomaterial is important in determining its potential applications in medicine and biotechnology, because their strong influence on cell function, adhesion and proliferation. In this study, thin films of Polystyrene and Polypropylene samples were modified by irradiation with low energy ion beams (30-150 keV) and swift heavy ions both with various fluences and energies. The changes were evaluated with different methods. Adhesion of NIH 3T3 fibroblasts onto unirradiated and irradiated surfaces has been studied by in vitro techniques. The correlations between physicochemical properties as a function of different irradiations parameters were compared with cell adhesion on the modified polymer surface.     

RBS studies of the lattice damage caused by 1 Me V Si implantation into Al0.3Ga0.7As/GaAs superlattices at elevated temperature

The lattice damage accumulation in GaAs and Al_0.3Ga_0.7As/GaAs superlattices by 1 MeV Si⁺irradiation at room temperature and 350°C has been studied. For irradiations at 350°C, at lower doses the samples were almost defect-free after irradiation, while a large density of accumulated defects was induced at a higher dose. The critical dose above which the damage accumulation is more efficient is estimated to be 2 × 10¹⁵ + Si/cm² for GaAs, and is 5 × 10¹⁵ Si/cm² for Al_0.8Ga_0.7As/GaAs superlattice for implantation with 1.0 MeV Si ions at 350°C. The damage accumulation rate for 1 MeV Si ion implantation in Al_0.3Ga_0.7As/GaAs superlattice is less than that in GaAs.     

Effects of electronic and nuclear interactions in SiC

In this study, we performed irradiation experiments on nanostructured 3C-SiC samples, with 95 MeV Xe ions at room temperature. This energy permits the observation of the combined electronic and nuclear interactions with matter. The grazing incidence X-ray diffraction results do not reveal a complete amorphization, despite value of displacement per atom overcoming the total amorphization threshold. This may be attributed to competing effects between nuclear and electronic energy loss in this material since a total amorphization induced by nuclear interactions was found after low energy ion irradiation (4 MeV Au). Moreover, electronic interactions created by high energy ion irradiations induce no disorder in single crystalline 6H-SiC. But in samples previously disordered by low energy ion implantation (700 keV I), the electronic interactions generate a strong defects recovery.     

Binomial distribution function for intuitive understanding of fluence dependence of non-amorphized ion-track area

We propose the binomial distribution function is a useful function to describe the fluence dependence of overlapped and non-overlapped area of ion-tracks created by high-energy heavy ions. The validity of the function has been proven by simple computer simulation assuming that ion-tracks are introduced at random positions of two-dimentional grid. In order to test the applicability of the function for describing accumulation behavior of non-amorphized ion-tracks, asymmetric X-ray diffraction peak observed for CeO₂ irradiated with 200-MeV ¹⁹⁷Au ions has been analyzed. The asymmetric peak observed after the irradiations can be explained by the sum of the original peak attributed to the matrix and the new peak partly attributed to non-overlapped area of ion-tracks. It has been found that the binomial distribution function is useful for explaining the fluence dependence of the non-overlapped area of ion-tracks.