强流脉冲离子束辐照对钛合金表面相结构的影响

利用X射线衍射(XRD)和能量色散的特征X射线谱(XEDS)扫描,对强脉冲离子束辐照钛合金的表面结构特征和成分分布进行了测试与分析。结果表明,试样钛合金为(α+β)型两相钛合金。当以低能流密度离子束辐照时,材料表面粗糙度的增加导致结构发生明显变化;随着离子束能流密度的增加,材料表面层出现微小非晶相;表面元素呈明显的层状均匀分布;多次脉冲离子束辐照下,表面形成Al2O3等氧化物,从而利于被辐照表面抗氧化性的提高。进一步提高离子束能流密度,多次脉冲辐照,材料表面形成了新相Al6MoTi和AlMoTi2。     

强流脉冲离子束辐照对钛合金显微组织的影响

为研究强流辐照过程中钛合金微观组织结构和化学成分的变化,利用束流成分70%H+和30%C+的混合强脉冲离子束对钛合金进行了表面轰击,对离子束诱发的显微组织形貌和化学成分在扫描电子显微镜(SEM)上进行分析。结果表明,钛合金内部组织由α和β两相构成,为α+β型两相钛合金。试样不同区域组织类型存在明显差异,大部分区域组织类型一致,局部区域属于典型的魏氏组织。强流辐照钛合金表层组织和微观结构发生一定的变化,边缘β相结构遭到一定程度的破坏。显微组织结构的变化是由于表层温度梯度引起的热应力及其在靶材体内的传播造成的。     

强流脉冲电子束轰击对单晶Si表面形貌的影响

用强流脉冲电子束技术对两种取向的单晶Si片进行了表面轰击,对电子束诱发的表面形貌进行了分析.实验结果表明,当能量密度～3 J/cm2时,轰击表面开始形成大量的熔坑.能量密度～4 J/cm2时,表面开始出现微裂纹,微裂纹的形态与单晶Si的晶体取向密切相关;强流脉冲电子束轰击能够诱发表层强烈的塑性变形,[111]取向单晶Si表面出现剪切带结构,而[001]取向单晶Si表面变形结构则以微条带为主;此外,变形区域内还出现大量<100 nm的微孔洞形貌,这些微孔洞的形成为制备表面多孔材料提供了可能.     

SKDll模具钢的强流脉冲电子束辐照改性

本文介绍强流脉冲电子束(HCPEB)材料表面改性原理,采用模具钢SKDll进行辐照处理实验.对处理样品表面进行形貌观察,发现熔坑面密度及粗糙度随脉冲处理次数的增加而减小.X射线衍射分析证实,多脉冲处理条件下表面改性层中碳化物发生溶解,形成高奥氏体含量的重熔组织,而过多的能量注入会使奥氏体发生再度分解.磨损性能测试表明,在低电压(19.8 kV)处理情况下,耐磨损性能得到改善,脉冲次数为8次时处理样品的耐磨性达到最佳,这与表面改性层中碳化物及奥氏体的相对含量变化密切相关.     

SKD11模具钢的强流脉冲电子束辐照改性

本文介绍强流脉冲电子束（HCPEB）材料表面改性原理,采用模具钢SKD11进行辐照处理实验。对处理样品表面进行形貌观察,发现熔坑面密度及粗糙度随脉冲处理次数的增加而减小。X射线衍射分析证实,多脉冲处理条件下表面改性层中碳化物发生溶解,形成高奥氏体含量的重熔组织,而过多的能量注入会使奥氏体发生再度分解。磨损性能测试表明,在低电压（19．8kV）处理情况下,耐磨损性能得到改善,脉冲次数为8次时处理样品的耐磨性达到最佳,这与表面改性层中碳化物及奥氏体的相对含量变化密切相关。     

强脉冲离子束辐照混合的RBS研究

采用卢瑟福背散射(Rutherford backscattering spectroscopy,RBS)方法对强脉冲离子束辐照Ti/Al、Al/Ti和Ni/Ti三组薄膜/衬底体系所形成的混合层进行了研究.在Ni/Ti组合中形成了厚度比离子射程大得多的、混合度较高的梯度混合层.发现熔融态混合的程度不仅取决于两材料在熔融态的表面张力的差别,而且取决于它们熔点的差异.这两个参量较接近的混合程度较好.     

中性粒子对强流脉冲离子二极管工作过程的影响

研究了强流脉冲离子二极管中阳极等离子体中的冷中性粒子与束离子的电荷交换条件以及电荷交换作用对空间电荷限制电流密度的影响，电荷交换作用产生的热中性粒子快速充满二极管间隙，并被电离，可引起二极管间隙短路。     

强脉冲离子束材料表面改性研究进展

强脉冲离子束材料表面改性技术是正在发展中的新的材料表面改性技术。近四、五年来 ,我们围绕发展强脉冲离子束材料表面改性技术对其主要机制 (强脉冲能量效应 )、离子辐照诱发的热力学过程、表面熔坑现象及大面积均匀离子束技术开展了比较全面的基础性研究。研究表明 ,强脉冲离子束改性除了离子注入的元素掺杂效应外 ,其更可利用强脉冲能量沉积诱发的热力学效应 ,有望突破离子射程对改性层厚度的限制 ,并高效利用离子剂量和能量 ,成为新一代低成本、高效率、高生产率、实用化的离子束材料改性与合成工艺。本文对于上述研究的主要进展和相关问题进行了总结和评论     

箍缩反射离子二极管产生的强流脉冲离子束特性

通过对离子束流密度分布的测量和对被离子束轰击的铜箔不同半径处表面微观形貌的分析,研究了200kV箍缩反射离子二极管产生的离子束特性。结果表明：轴线上离子束流密度最大。     

强脉冲离子束材料表面改性研究进展

强脉冲离子束材料表面改性技术是正在发展中的新的材料表面改性技术。近四、五年来,我们围绕发展强脉冲离子束材料表面改性技术对其主要机制(强脉冲能量效应)、离子辐照诱发的热力学过程、表面熔坑现象及大面积均匀离子束技术开展了比较全面的基础性研究。研究表明,强脉冲离子束改性除了离子注入的元素掺杂效应外,其更可利用强脉冲能量沉积诱发的热力学效应,有望突破离子射程对改性层厚度的限制,并高效利用离子剂量和能量,成为新一代低成本、高效率、高生产率、实用化的离子束材料改性与合成工艺。本文对于上述研究的主要进展和相关问题进行了总结和评论。     

A Numerical Study of Cracks Appearance on Tungsten Surface After High Intense Pulsed Ion Beam Irradiation

Due to the outstanding physical properties, Tungsten has been proposed for use in the divertor of future fusion devices. However, tungsten shall face strong particle bombardment from the plasma, which causes severe damage to the material. The purpose of this work is to build such an accurate analytical model which can predict the damages in target material like crack production and propagation after high intense pulsed ion beam irradiation. Hence, a two-dimensional finite element method is used to study the effect of high intense pulsed ion beam on tungsten surface numerically. To judge temperature and stress distribution in material, thermal conduction model is combined with non-linear fracture mechanics model and J-Integral parameter is used as a criterion to judge the crack propagation. Simulation results reveal that different crack heights and sizes can affect the results and there is a critical depth for crack propagation. The model gives good results to real experimental observations and has potential applications for different intense pulsed electron/plasma beams and different target materials as well.     

Surface Etching and DNA Damage Induced by Low-Energy Ion Irradiation in Yeast

Bio-effects of survival and etching damage on cell surface and DNA strand breaks were investigated in the yeast saccharomyces cerevisiae after exposure by nitrogen ion with an en- ergy below 40 keV. The result showed that 16% of trehalose provided definite protection for cells against vacuum stress compared with glycerol. In contrast to vacuum control, significant morpho- logical damage and DNA strand breaks were observed, in yeast cells bombarded with low-energy nitrogen, by scanning electron microscopy (SEM) and terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling (TUNEL) immunofluorescence assays. Moreover, PI (propidium iodide)fluorescent staining indicated that cell integrity could be destroyed by ion irradiation. Cell damage eventually affected cell viability and free radicals were involved in cell damage as shown by DMSO (dimethyl sulfoxide) rescue experiment. Our primary experiments demonstrated that yeast cells can be used as an optional experimental model to study the biological effects of low energy ions and be applied to further investigate the mechanism(s) underlying the bio-effectsof eukaryotic cells.     

Fracture of Silicon and Germanium Induced by Pulsed Electron Irradiation

This paper presents certain preliminary results on the fracture of silicon, germanium and indium antimonide resulting from pulsed electron irradiation. Experimental results show that the rapid absorption of energy can produce brittle fracture in the semiconducting materials silicon, germanium and indium antimonide. Samples were irradiated using the external electron beam from a flash X-ray generator having a peak electron energy of 2.2 Mev and a pulse width of approximately 40 nsec. All irradiations were done at room temperature with the total exposure controlled by an appropriate choice of separation distance between sample and source. Samples of various sizes and geometry were prepared from single crystals of n-type germanium and silicon. Sample orientation was obtained through X-ray diffraction. Surface treatments were varied and included a finish polish and etch. Experimental results on germanium, silicon and indium antimonide have established the fracture threshold for polished and etched bulk material to be approximately 34 cal/g for silicon, about 8.5 cal/g for germanium and 4 cal/ g in indium antimonide. Surface treatment played an important role in the observed fracture level. No dimensional dependence of the fracture threshold was observed using polished and etched bars 1 × 1 mm2 in cross section and having lengths between 1 and 25 mm. The fracture planes in both silicon and germanium were found to be the (111) crystal planes and the (110) planes in indium antimonide.     

Numerical Study on the Two-Dimensional Temperature Fields of Titanium/Aluminum Double-Layer Target Irradiated by High-Intensity Pulsed Ion Beam

Interaction between high-intensity pulsed ion beam (HIPIB) and a double-layer target with titanium film on top of aluminum substrate was simulated. The two-dimensional nonlinear thermal conduction equations, with the deposited energy in the target taken as source term, were derived and solved by finite differential method. As a result, the two-dimensional spatial and temporal evolution profiles of temperature were obtained for a titanium/aluminum double-layer target irradiated by a pulse of HIPIB. The effects of ion beam current density on the phase state of the target materials near the film and substrate interface were analyzed. Both titanium and aluminum were melted near the interface after a shot when the ion beam current density fell in the range of 100A/cm2 to 200A/cm2.     

离子辐照样品的表面处理方法研究

离子辐照实验已广泛应用于评价反应堆压力容器钢的辐照损伤效应,这对样品表面状态提出了苛刻的要求。分别采用机械抛光、振动抛光、电化学抛光与真空退火的方法对RPV钢样品表面进行了处理,采用慢束正电子湮没-多普勒展宽谱实验表征了样品表面的损伤层状态,采用纳米压痕测试表征了样品表面的应力状态。实验结果表明:对于RPV钢离子辐照样品,建议优先采用机械抛光+真空退火处理的方法处理样品表面,其次可采用电化学抛光处理方法。同时指出了该结论也适用于材料化学成分、强度与韧性等力学性能及热处理状态等相近的其他低合金钢离子辐照样品的表面处理。     

Study on DNA Damage Induced by Neon Beam Irradiation in Saccharomyces Cerevisiae

Yeast strain Saccharomyces cerevisiae was irradiated with different doses of 85 MeV/u 20Ne10+ to investigate DNA damage induced by heavy ion beam in eukaryotic microorganism. The survival rate, DNA double strand breaks (DSBs) and DNA polymorphic were tested after irradiation. The results showed that there were substantial differences in DNA between the control and irradiated samples. At the dose of 40 Gy, the yeast cell survival rate approached 50%, DNA double-strand breaks were barely detectable, and significant DNA polymorphism was observed. The alcohol dehydrogenase II gene was amplified and sequenced. It was observed that base changes in the mutant were mainly transversions of T→G and T→C. It can be concluded that heavy ion beam irradiation can lead to change in single gene and may be an effective way to induce mutation.     

Role of Ion Beam Irradiation and Annealing Effect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple （5, 10, 15, 20 and 25） focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×10^19 m^- 3 to 1.3×10^19 m ^-3, respectively. Moreover, the effect of continuous annealing （473 K and 523 K） on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray diffraction （XRD） patterns with increasing focus shots are： （i） variation in the crystallinity of AlN along （111）, （200） and （311） planes, （ii） increasing average crystallite size of AlN （111） plane, and （iii） stress relaxation observed in AlN （111） and （200） planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened diffraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. Raman and Fourier transform infrared spectroscopy （FTIR） analysis confirm the presence of AlN and Al203 for the surface layer annealed at 473 K temperature. Raman analysis shows that the overlapping of AlN and Al2Oa results in the development of residual stresses. Scanning electron microscope （SEM） results demonstrate that the formation of rounded grains （range from 20 nm to 200 nm） and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.     

表面自纳米化对钛合金与不锈钢的扩散焊接的影响

用恒温恒压扩散焊接法实现了表面纳米化后的TA17近α型钛合金与OCr18Ni9Ti不锈钢的连接.焊接材料用气动喷丸方式进行表面自纳米化.利用液压万能试验机测试了接头拉伸强度,并对焊接接头及断口形貌和组织进行了扫描电镜观察及能谱分析.结果表明:接头界而附近出现了不同的层,在不同温度下的焊接接头组织及分布大致相同;与未对材料进行表面自纳米化处理相比,材料经表而自纳米化处理后,加快了被焊偶件的接触进程,提高了原子的扩散速率和焊接接头的强度,并缩短了焊接时间.