含氦纳米晶钛膜的PBS和XRD研究

为研究不同晶粒尺寸纳米钛膜的储氦行为,在He-Ar混合气体下,用磁控溅射方法沉积纳米晶钛膜,利用PBS(proton backscattering)、XRD(X-ray diffraction)对膜的氦含量和微观结构及晶粒大小进行了研究.结果表明:在其它实验参数不变的情况下,当沉积温度从60℃升至350℃时得到均匀分布的含氦量(指原子百分比)从38.6%逐渐降至9.2%的钛膜,其平均晶粒由13.1 nm增加到44.2 nm;当He/Ar分压比分别为6、10、15、19时得到均匀分布的含氦量分别为17.6%、47.2%、48.3%和38.6%的钛膜.He的引入引起(002)晶面衍射峰向小角度移动,但(100)晶面衍射峰不变,即晶胞参数c增加,a不变化;随膜中He含量的增加,衍射峰展宽,晶粒变小,显示出氦的掺入有抑制纳米晶粒长大的趋势.     

纳米晶粒钛膜中氦注入的剂量保持和释放规律

在室温～400℃范围内,用卢瑟福质子背散射技术测量了100keV、注入剂量2 2×1018cm-2的纳米晶粒钛膜中氦的浓度分布、不同温度下的剂量保持及其浓度释放。室温下经210d后,氦在该纳米晶粒钛膜中的剂量保持达68%,其He Ti原子比为52 6%;100℃下氦的保持剂量为室温下的89 6%,此时的He Ti原子比为44%;400℃下的保持剂量为室温下的32 6%,He Ti原子比为17 1%。同时观察到了氦的释放随温度上升呈现波浪式的变化特点。从能量稳定性观点初步探讨了纳米晶粒钛膜有效保持氦的可能机制。     

氚化钛膜中氦的热解吸行为初步研究

对He、Ti原子比n(He)/n(Ti)为0.004～0.300的7块氚化钛膜样品在1300K以下进行热解吸分析,以获得它们的热解吸谱。在低于1300K范围内,氚化钛膜共有4种氦的热释放峰,分别对应于贯穿至表面的氦泡、近表面的氦、体相中的氦泡和氦的小团簇。对这4种类型的氦释放峰的解吸温度和解吸量随膜中总氦量的变化分别进行分析,研究观测膜中各种状态存在的氦量随n(He)/n(Ti)增加的变化趋势。实验观测到,升温将导致氚化钛膜可容纳的氦量大幅降低。     

磁控溅射法制备含氦钛膜及膜中氦的热解吸研究

采用He/Ar复合气氛下磁控溅射方法,在Ti、TiZrYAl 和TiMoYAl等3种薄膜中引入浓度(氦-金属比)高达0.19的氦.引入的氦在膜层内沿深度均匀分布,并主要存在于直径为2～5 nm的高压He泡内.热解吸实验表明,在相同He含量下,TiHe膜中He的解吸峰温度与氚化钛中衰变产生的3He的解吸峰温度基本一致.与纯钛相比,合金膜中氦的热解吸谱宽化明显,表明He在合金膜内的捕获形式更为复杂.     

常温氦离子注入纳米钛膜的微结构分析

在常温下,用200、100 keV He离子按He-Ti原子浓度比0.1、0.3和0.2的剂量注入纳米钛膜,采用现代表面分析技术对试样进行形貌观察与微观分析.测试分析结果表明注入前,沉积膜的原子力显微镜(AFM)形貌像呈现从几十至200 nm以上极不均匀的晶粒尺度;注入后,3个试样的晶粒均有所长大,且随着注入剂量的增加,其长大趋势更为明显.这些长大的晶粒中同时存在大量的亚结构,表明在高剂量氦离子注入下,导致出现表层晶粒细化现象;He离子注入后的试样在衍射角15°～40°之间出现可辨的衍射峰,其膜层内的平均晶粒尺寸约136 nm,说明经离子注入后,膜层内纳米粒子的结晶度得到进一步提高,晶粒度比注入前长大.此结果证实了AFM B微米级视场的观察.     

含氦Ti膜的透射电镜研究

在氦气和氩气混合气氛中用磁控溅射法制备含氦Ti膜。应用透射电镜观察不同氦气和氩气流量比对Ti膜微观结构及氦泡形貌和分布的影响,并研究退火温度对氦泡聚集和长大行为的影响。研究观测到,Ti膜中氦泡的尺寸随氦流量的增加而增大,氦泡的密度随氦流量改变出现一最大值;温度低于0.5 Tm时,He泡以泡迁移和合并机制(MC)长大;温度高于0.5 Tm时,He从小泡离解,被大泡吸收,以OR机制长大,氦泡尺寸明显增加。     

纯铝中氦泡分布特点的研究

将工业纯铝抛光后进行He离子注入,注入剂量为3×10²⁰ m^-2,注入能量为500 keV。利用SRIM软件模拟预测得离子注入后He原子在距表面1.8 μm处浓度最高。将He离子注入样品,在190 ℃时效192 h,促进氦泡的形成和长大,用透射电子显微镜观测样品深度方向上氦泡的分布。结果显示,距表面约1.8 μm处氦泡密度最大,说明 He原子浓度最高,与SRIM软件模拟预测结果一致。同时发现,晶界处氦泡的尺寸较晶粒内的大,说明晶界有利于氦泡的形成和长大;晶界两侧不同晶粒内氦泡尺寸有较大差异,可能是因为晶粒取向不同造成晶粒中氦泡的形核长大过程不同,说明晶粒取向对氦泡的合并长大行为可能有显著影响。     

直流磁控溅射法制备含氦铝膜

采用氦氩混合气氛下直流磁控溅射沉积方法制备含有氦原子的金属铝膜。经碳原子弹性前冲散射分析（C-ERDA），薄膜中氦原子浓度可达约7％，且分布均匀。实验研究了薄膜中的氦含量与溅射真空室气氛中氦的相对含量、基底偏压及沉积温度间的关系。薄膜的X射线衍射分析结果显示：膜中的氦含量变化并未引起明显的峰位移，只是随氦含量增加谱峰宽化。热释放实验证实，氦在薄膜中稳定存在，约500℃以上时方出现氦的释放。     

基体温度对钛膜表面形貌和力学性能的影响研究

应用电阻蒸发镀膜方法在钼基体表面沉积钛膜。采用X射线衍射仪（X-ray Diffraction,XRD）对钛膜的物相进行表征，获得钛膜的择优取向；采用扫描电镜（Scanning Electron Microscope,SEM）和原子力显微镜（Atomic Force Microscope,AFM）对钛膜的表面形貌进行表征，获得钛膜的晶粒尺寸分布情况及表面粗糙度；采用AFM纳米压痕技术对钛膜的力学性能进行表征，获得钛膜的弹性模量。结果表明：基体温度对钛膜的微观结构及力学性能有重要影响，在600～750℃范围内，随着基体温度的升高，钛膜晶粒取向的主要影响因素由应变能变为表面能，钛膜的择优取向由（101）变为（002）；基体温度的升高增强了基体表面钛原子的扩散能力，钛膜的平均晶粒尺寸、粗糙度及弹性模量均随基体温度的升高而增大。     

氦在钛靶及Al2O3中的行为研究

报道了利用质子增强背散射和扫描电镜等方法，研究不同工艺制作的钛膜靶和不同纯度的Ａｌ２Ｏ３中注入的＾４Ｈｅ在室温下的行为。研究结果表明，离子束增强淀积新工艺制备的钛膜与基体的结合强度优于原来热蒸发镀制的钛靶；氦在Ａｌ２Ｏ３与在钛靶中具有不同的释放机制；钛靶的起泡注入剂量在４×１０＾１７－７×１０＾１７Ｈｅ／ｃｍ＾２之间，而且起泡剂量与泡破裂剂量相差不大；较之新工艺制备的钛靶，氦在Ａｌ２Ｏ３中更不易形     

贮氚非晶态锆钒合金膜中的氦释放行为

用热解吸和静态贮存方法对贮氚非晶态ZrV₂合金膜中³He的释放行为进行了系统分析。结果显示：³He原子存在597.3、725.8和1 146.6 K等3个解吸峰,其中第3解吸峰的解吸量最大,是由非晶态基体中的³He释放形成;在长达2 423 d的静态贮存期间,非晶膜中³He原子的释放系数始终在10^-5量级范围内波动并呈线性上升趋势,但仍未加速释放;贮存温度变化会引起释放系数剧烈波动;与贮氚晶态ZrV₂合金膜相比,非晶膜的固氦能力显著增强。上述结果初步证实了非晶合金具有良好的固氦性能,这有助于人们从全新视角认识材料中的氦行为。     

Interface enabled defects reduction in helium ion irradiated Cu/V nanolayers

Sputter-deposited Cu/V nanolayer films with individual layer thickness, h, varying from 1 to 200 nm were subjected to helium (He) ion irradiation at room temperature. At a peak dose level of 6 displacements per atom (dpa), the average helium bubble density and lattice expansion decrease significantly with decreasing h. The magnitude of radiation hardening decreases with decreasing individual layer thickness, and becomes negligible when h is 2.5 nm or less. This study indicates that nearly immiscible Cu/V interfaces spaced a few nm apart can effectively reduce the concentration of radiation induced point defects. Consequently, Cu/V nanolayers possess enhanced radiation tolerance, i.e., reduction of swelling and suppression of radiation hardening, compared to monolithic Cu or V.     

Preparation of Al thin films charged with helium by DC magnetron sputtering

Helium atoms, up to 6.9 at.%, were introduced into Al films by DC magnetron sputtering in a He/Ar mixed atmosphere and distributed evenly in it. The relation between the He/Ar flux ratio, bias voltage, substrate temperature and helium concentration is studied. The helium concentration can be easily controlled by change of the process parameters and it greatly affects the morphology of film. TEM analysis suggests that small helium bubbles with a diameter of 1 nm are formed in the grain.     

Investigation on Retention and Release Behaviors of Hydrogen and Helium in Vanadium Alloy

Vanadium alloy is proposed as an attractive candidate for first wall and blanket structural material of fusion reactors. The retention and release behaviors of hydrogen and helium in vanadium alloy may be an important issue. In the present work, 1.7 keV deuterium and 5 keV helium ions are respectively implanted into V-4Cr-4Ti and V-4Ti at room temperature. The retention and release of deuterium and helium are measured with thermal desorption spectroscopy (TDS). When the helium ion fluence is larger than 3 ×1017 He/cm2, the retained helium saturates with a value of approximately 2.5 ×1017 He/cm2. However, when the ion fluence is 1×1019 D/cm2, the hydrogen saturation in vanadium alloy does not take place. Experimental results indicates that hydrogen and helium retention in vanadium alloy may lead to serious problems and special attention should be paid when it is applied to fusion reactors.     

The Effect of Substrate Temperature on the Structure and Morphology of Titanium Nitride Compounds Grown by DC Magnetron Sputtering

The TiN thin films were deposited on p-type silicon (100) substrates using reactive planar DC magnetron sputtering system. The target was 99.99% pure Ti. The reactive sputter gas was a mixture of Ar (99.999%) and N₂ (99.999%) with the ratio Ar (97%) and N₂ (3%) by volume. Structural characterization of the coating was done using X-ray diffraction (XRD). The surface roughness of the coating was determined using an Atomic Force Microscope (AFM). The reflectivity of thin films was investigated by a spectrophotometer system. The X-ray diffraction measurements showed that by increasing the substrate temperature during the growth, change in crystalline structure will occur. The crystallite size of the films determined by Scherrer’s equation, and the crystallite size measured by AFM also increased by increasing the substrate growth temperature. The surface reflectivity measurements indicate that by increasing the substrate growth temperature, the optical properties of the films changes. The change in optical properties and crystalline structure of the films indicate that substrate growth temperature plays an important role in structure and morphology of the grown layers.     

冷却气体对黑腔系统温度场影响数值模拟

为了研究氦氢冷却气体对黑腔系统温度场的影响,采用CFD数值模拟方法,计算了氘氚靶丸外表面最大温差与填充区域的气体流场随气压、氦气含量变化的规律。通过对冷却壁面施加壁温扰动函数,监测了靶丸外表面平均温度、最大温差随时间的波动。研究结果表明：提高氦氢混合气体的填充压力或减小氦气含量,使得黑腔上下部分冷却气体自然对流强度差异增大,导致靶丸外表面温度场均匀性恶化;但降低冷却气体中氦气含量使气体导热系数减小,比热容增大,使得冷却壁温扰动对靶丸外表面温度场均匀性的影响减弱。     

Helium retention of vanadium alloy after energetic helium ion irradiation

Helium irradiation experiments of V–4Ti alloy were conducted in an ECR ion irradiation apparatus by using helium ions with energy of 5 keV. The ion fluence was in the range from 1 × 10¹⁷ He/cm² to 8 × 10¹⁷ He/cm². After the helium ion irradiation, the helium retention was examined by using a technique of thermal desorption spectroscopy (TDS). After the irradiation, the blisters with a size of about 0.1 μm were observed at the surface, and the blister density increased with the ion fluence. Two desorption peaks were observed at approximately 500 and 1200 K in the thermal desorption spectrum. When the ion fluence was low, the retained helium desorbed mainly at the higher temperature regime. As increase of the ion fluence, the desorption at the lower temperature peak increased and the retained amount of helium saturated. The saturated amount was approximately 2.5 × 10¹⁷ He/cm². This value was comparable with those of the other plasma facing materials such as graphite.