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。     

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。     

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。     

磁控溅射沉积含He纳米晶钛膜制备

采用直流磁控溅射方法，通过分别改变衬底温度及He分压来制备不同氦含量的钛膜。利用PBS、XRD、TEM及AFM分别对钛膜中的He含量、平均晶粒尺寸及膜的表面形貌进行分析。结果表明：在不同温度范围内，温度变化对所制备钛膜中He含量的影响明显不同；He含量与晶粒尺寸直接相关，氦原子进入钛膜后，抑制了晶粒的长大；随着钛膜中He与Ti的原子个数比由1.0%增加到11.9%，TEM测得的平均晶粒尺寸由约35nm减小到约4nm；选择合适的He分压，能够制备出He含量较高的氦钛膜。     

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.     

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。     

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。     

金属氚化物中3He的热解吸方法

在自行设计的全金属高真空热解吸系统上,以ELITE SPE-50型四极质谱计(QMS)为分析器,建立了金属氚化物中3He的热解吸和数据处理方法.解吸过程中,金属系统处于真空密闭状态,薄膜压力计直接测量解吸出的气体压力,质谱计则通过微量渗漏阀在线取样测量,所采集的数据均为积分形式.研究结果表明四极质谱计标定解吸系统内4He的分压＜350 Pa时,其相关系数R＞0.99,且记忆效应的贡献极弱;离子态氚T+对m/e=3组分分压的贡献可按IT+≈0.01 IT2+确定,不干扰3He的测定;将气体解吸所得的积分数据经平滑并微分处理后可准确得到气体释放速率与退火温度的关系,即热解吸谱.     

Ti—Mo合金氘化物热解吸过程研究

采用非零初压热解吸法研究了不同钼含量的钛钼合金TiMo_x(x=0.03、0.13、0.25、0.50、1.00,Mo与Ti原子数之比)氘化物的热解吸动力学,测试了氘解吸量与解吸时间的关系,应用反应速率分析方法得到了其热解吸速率常数k_d和热解吸表观活化能E_d;并与氕化物的热解吸动力学行为进行了比较。结果显示,x=0.03时,合金氕化物E_d小于氘合金化物E_d,与钛放氢动力学同位素效应一致;x=0.13、0.25时,氕化物E_d大于氘化物E_d;x=0.50、1.00时,氕化物与氘化物的E_d差别不大。通过初始解吸时合金中氕、氘含量的比较,结合室温下合金吸氕、氘量及物相结构,对合金放氢动力学同位素效应的本质进行了探讨。     

Erosion of tungsten surfaces in He and Ar/He plasma

Irradiation tests of tungsten surface were performed with He and He/Ar plasma generated by microwave electron cyclotron resonance. Thickness loss was used as the erosion rate of tungsten surface under the plasma irradiation. The results revealed that the thickness loss increased linearly with negative bias. SEM images proved that the addition of Ar apparently increased the plasma erosion. The thickness loss increased sharply with the Ar fraction of Ar/He mixture when it was \20 %,where the increasing slope of thickness loss lowered down gradually.     

The He/He heat exchanger — Design and semitechnical testing

This is a report on the development of the He/He heat exchanger which is used for high-temperature reactors (HTR) combined with the steam gasification of coal. A concept has been agreed on the basis of the requirements resulting from the application of the HTR. Subsequently those steps, which are required for the development of this component up to construction maturity are described. Simultaneously, questions dealing with material, construction, design, manufacture and related experimental development are taken into consideration.     

Metastable He deexcitation at semiconductor interfaces

A review is given of the application of metastable deexcitation spectroscopy (MDS) to the study of the interface formation between semiconductors and different materials. In particular we present an overview of the results obtained on nanostructured interfaces, where strain and reaction between the substrate and the overlayer atoms drive the growth mode and the morphology of the system. As prototypical examples we discuss the growth of CaF₂ on silicon and rare earths (Yb, Er) on silicon and gallium arsenide. The mechanisms and chemical reactions which bring to interface formation are examined on the basis of MDS results and their comparison with photoemission.     

小型高分辨率^3He／^4He质谱计的离子光学

一、前言地球上氦同位素组成有三个层次:地幔氦、地壳氦和大气氦。地幔氦是地球生成时保留下来的原生氦,~3He含量高,~3He/~4He比值约10~(-5);地壳氦是地壳中铀、钍等放射性元素蜕变过程中生成的,~3He/~4He比值约10~(-7)～10~(-8);大气氦是在地幔氦与地壳氦不断地向     

Double-Differential Cross Section of 5He Emission

The probability of ^5He particle emission has been affirmed theoretically. In order to describe the ^5He emission, the theoretical formula of the double-differential cross section of emitted ^5He is established. Based on the pick-up mechanism, used for calculating the formula of d, t, ^3He and a emissions, the theoretical formula of double-differential cross section of ^5He is obtained, which is expressed in the form of Legendre coefficients. In the case of low incident energies, the configuration is the dominant part in the reaction processes.     

Temperature dependence of He trapping in niobium

The total amount and the depth distributions of 9 and 15 keV implanted ³He ions trapped in polycrystalline niobium have been studied using the ³He(d,p)⁴He reaction. The implantation target temperature was varied from 20 to 1000° C and subsequent anneal studies were carried out for temperatures up to 1600° C. For implantation temperatures below 400° C all ²He particles coming to rest in the target are trapped. Between 500°C and 1000°C the trapping probability decreases gradually with increasing temperature to a few percent. A greater amount of helium is always retained upon annealing of a lower temperature implant to a particular temperature than is retained for implantation at that temperature.     

双束(He+/e-)辐照下氦对12Cr-ODS铁素体钢组织损伤影响研究

利用氦离子(He+)束和电子(e-)束双束同时辐照化学溶胶法制备的新型12Cr-ODS铁素体钢.实验结果表明,辐照初期,随着辐照剂量增加,点缺陷团(黑斑)在基体内形成,密度不断增大,尺寸长大缓慢,辐照剂量为0.8dpa时形成问隙型位错环.不同试验温度下,辐照均产生小尺寸高密度的空洞,随着辐照剂量增加,空洞尺寸长大缓慢,...     

Resolution enhancement of the 3He(d,p)4He resonance for profiling helium in solids

The use of nuclear resonances techniques for characterizing the distribution and lattice location of implanted atoms in metals is a direct and, in principle, simple method for studying helium and hydrogen gas in CTR first wall materials. However, the reaction ³He(d,p)⁴He, has a broad (350 keV) half-width in the resonance yield curve. When using a deuteron beam, under normal probing conditions, to measure helium distributions in metals, a rather low stopping power results in limited resolution of about 3 μm. In many cases resolution of a few thousand angstroms or better is necessary. We have experimentally examined two resolution enhancement methods and reported the results in a previous article. The present paper will review those results and examine limitations of resolution enhancement that are obtainable through geometrical and mathematical techniques.