用正电子湮没方法研究氦离子等离子体辅助分子束外延InP(InGaAsP)/InP结构

用氦离子等离子体辅助分子束外延方法生长了ＩｎＰ（ＩｎＧａＡｓＰ）／ＩｎＰ结构。结果发现,ＰＡＢＭＥ外延层具有很高的电阻率和很快的光反应特征。用慢正电子湮没方法研究了这一外延层。测量结果说明这些特性与等离子体造成的缺陷及缺陷随温度变化有直接关系。     

Structure and defects evolution at temperature and activation treatments of the TiCr2 intermetallic compound of Laves phase C36-type

In this work, microstructure and defect evolution at a temperature and activation treatment of the TiCr₂ intermetallic compound of Laves phase C36-type synthesized in the abnormal glow discharge plasma were investigated. The crystalline structure of the C36TiCr₂ powder crushed by hydrogenation-dehydrogenation (HD) method is characterized by the following lattice parameters: a = 4.932 Å and c = 16.059 Å. The dilatation of the crystal lattice under the hydrogenation at the HD crushing process leads to the formation of partial dislocations. For the first time ever the experimental value of the positron lifetime of the synthesized compound of the C36TiCr₂ Laves phase, this amounted to (141 ± 2) ps, established by the positron spectroscopy. The optimal activation parameters of the HD-crushing C36TiCr₂ powder were established: the temperature should be in the range from 450 to 500 °C, the exposure time in a hydrogen atmosphere at a pressure of (1–8) atm. must be at least 10 min.     

氢氧化铝含量对硅橡胶结构及憎水恢复性的影响

氢氧化铝(ATH)作为阻燃剂是复合绝缘子硅橡胶的基本原料。为研究ATH含量对硅橡胶结构和憎水恢复性的影响,炼制ATH质量分数分别为40%、45%、50%和55%的硅橡胶试样,对试样进行正电子寿命谱、邵氏硬度测试,及5 min Ar等离子体老化实验。结果表明:ATH质量分数从40%增加到55%时,次长寿命强度I3从7.8%下降到6.1%,而最长寿命强度I4从24.8%锐减至18.6%。随ATH质量分数增加,硅橡胶中2种自由体积的尺寸基本不变;但ATH颗粒容易发生团聚,这些颗粒占据了分子链运动空间,限制了大分子链的运动,使得大尺寸自由体积数量减少,特别是使大尺寸孔洞的数量锐减。邵氏硬度随ATH质量分数增大而变大,说明样品由弹性体朝无机体转变。经相同等离子体处理时间后,硅橡胶憎水恢复速度随ATH质量分数增加而减慢,结合正电子湮没寿命结果可知,ATH的加入限制了体系内硅橡胶分子链的运动,自由体积数量减少,使得小分子输送通道变少。     

肿瘤PET药物的现状和展望

随着正电子发射计算机断层显像技术(PET)的研发,PET药物在肿瘤科学研究及临床应用中具有越来越重要的作用。本文在肿瘤代谢显像、肿瘤细胞凋亡显像、反义显像、受体显像及基因表达监测等方面集中介绍肿瘤PET药物的进展情况及其发展前景。     

用正电子湮没技术研究新锆合金包壳的离子辐照效应

国产Zr-Sn-Nb系新锆合金SZA-4和SZA-6是CAP1400大型先进压水堆包壳材料的主要候选材料,对其辐照性能的研究可为制备工艺改进提供科学依据。在中国原子能科学研究院HI-13串列加速器辐照终端,在300 ℃温度下,用100 MeV的Fe束流对两种新锆合金包壳管材进行5 dpa剂量辐照。辐照前后的正电子湮没寿命测量表明：两种样品辐照前湮没寿命为Zr中单空位寿命,表明管材制备过程中最后的退火温度和时间尚未完全消除加工引入的缺陷;两种样品辐照后的正电子湮没寿命减小,分析表明这是由于辐照导致Fe在锆合金中重新分布,主要分布在bcc结构的β-Nb沉淀相颗粒与hcp结构的α-Zr基体之间具有开空间的相界,正电子被相界捕获,与周围Fe原子电子湮没,造成湮没寿命减小。     

Positron annihilation and nano-indentation analysis of irradiation effects on the microstructure and hardening of A508-3 steels used in Chinese HTGR

The irradiation and annealing behavior of Chinese A508-3 reactor pressure vessel (RPV) steel (0.04 wt% Cu) after 3 MeV Fe-ion irradiation ranging from 0.1 to 20 dpa at room temperature (called RTRPV) and high temperature (250?°C, called HTRPV) was studied by positron annihilation Doppler broadening (PADB) spectroscopy and nano-indentation hardness. PADB showed that the density of vacancy-type defects was higher for low-temperature irradiations. The higher hardness was found after high-temperature irradiation because of the formation of solute clusters during irradiation. Positron annihilation measurements revealed the interaction and clustering of vacancies with solute clusters which were introduced by Fe-ion irradiation. For both RTRPVs and HTRPVs, the positron defect parameter and positron diffusion length showed the recovery of the irradiation-induced defects. Total recovery was observed after annealing at 450 °C.     

国产改进型316L不锈钢的微结构研究

采用正电子湮没寿命方法研究了国产改进型316L不锈钢的微结构及其温度变化。该不锈钢含有单空位、双空位、位错和小空位团等缺陷。经400℃,600℃,800℃退火后,单空位、双空位和位错缺陷分别消失。小空位团是四空位和五空位构成的空位团,低于200℃退火,缺陷复合五空位团成分随退火温度升高而增大,高于400℃时空位团分裂,五空位团成分减少,800℃退火还存在较低浓度的四空位团。     

GH903合金的离子注入表面改性研究

用离子注入、氧化和慢正电子束分析研究了ＧＨ９０３合金的氧化性能的改善与微观作用机理。注入的Ｃｒ＋．Ｙ＋的能量均为６０ｋｅＶ，注入的剂量分别由１ｘ１０１７．ｃｍ－２（Ｃｒ＋）、１ｘ１０１５Ｃｍ－２（Ｙ＋）和［１ｘ１０１５．ｃｍ－２（Ｙ＋）＋１ｘ１０１７·ｃｍ－２（Ｃｒ＋）］。结束显示，注入样品与未样品相比。氧化增重分别减少４．８％（注Ｃｒ＋）、２４．２％（注Ｙ＋）和３２．３％（注Ｙ＋＋Ｃｒ＋）。这表明合金氧化性能改善的作用机理主要是注入离子对样品浅表层内缺陷的填充与退火。同时，注入元素的化学性能和使样品表面更致密也起了重要作用。     

Damage Characteristics of TiD2 Films Irradiated by a Mixed Pulsed Beam of Titanium and Hydrogen Ions

Titanium deuteride is an important nuclear material used in the field of nuclear technology, and further research is needed into TiD_2 films irradiated by pulsed ion beams of the vacuum arc discharge with hydrogen. In the current study, these irradiated TiD_2 films have been investigated using scanning electronic microscopy and slow positron annihilation techniques. Both the thermal effect and irradiation defects of TiD_2 films were studied, following their irradiation with mixed pulsed ion beams of titanium and hydrogen ions. It is found that the thermal effect is trivial on the irradiated surfaces, and the dominant effect is irradiation defects which can be enhanced by repetitive shots and is characterized by the inner diffusion of irradiation defects.