Recovery of neutron-irradiation-induced defects of Al2O3, Y2O3, and yttrium-aluminum garnet

SiC fiber-reinforced SiC matrix composites (SiC_f/SiC) are considered as one of the candidates for blanket materials in future fusion reactors and as an advanced fuel cladding material for next-generation fission reactors. Generally, the densification of SiC needs sintering additives and oxides such as Al₂O₃, Y₂O₃, and yttrium-aluminum garnet (YAG, Y₃Al₅O₁₂), which are frequently added to SiC. However, the effects of neutron irradiation on sintering additives are still unclear. In this study, we performed the neutron irradiation of Al₂O₃, Y₂O₃, and YAG at fluences up to 2.0–2.5 × 10²⁴ n/m² (E > 0.1 MeV) at 60–90 °C. The isochronal recovery of the macroscopic volume of Al₂O₃ against annealing temperature showed smooth and continuous shrinkage at a temperature of up to 1200 °C, and the volume slightly increased above that temperature. In contrast, the volume of Y₂O₃ showed quick shrinkage at the low temperature range, and slower and smooth recovery was observed up to ～1100 °C. In the case of YAG, the recovery of volume occurred in a step-wise manner at 600–750 °C, and continuous shrinkage occurred at temperatures lower and higher than that temperature range. The activation energies for the macroscopic volume recoveries of three oxides were obtained from the Arrhenius plots of the rate coefficients. Two-stage recovery was observed for Al₂O₃, whereas more complicated recovery processes were suggested for Y₂O₃ and YAG.     

Thermal recovery of defects in neutron irradiated UO2

Thermal recovery of both lattice and volume expansions of UO₂ irradiated to a dose of less than 9.97 × 10¹⁷ fissions/cm³ was studied in a temperature range from 200 to 1000°C. Two or three steps were observed in the recovery of lattice expansion. Volume expansion was also recovered in two or three steps. Recovery behavior of volume expansion of the specimen irradiated to 9.97 × 10¹⁷ fissions/cm³ was different from those irradiated to lower doses, and an abrupt volume increase was observed in the temperature range from 500 to 700 °C. This behavior might be related to the bubble swelling due to fission product gases. From the results on the recovery of lattice and volume expansions, the behavior of lattice point defects and defect clusters was discussed.     

Volume change of Al2O3 and MgAl2O4 induced by 14-MeV neutron irradiation

Volume change of Al₂O₃ and MgAl₂O₄ induced by irradiation with 14-MeV neutrons at 50°C has been measured. It is shown that the volume change of A1₂O₃ is anisotropic and is larger than that of MgAl₂O₄ about a factor of five. The result for MgAl₂O₄ is compared with that of fission neutron irradiation.     

裂变快中子辐照在GaAs中产生缺陷的正电子湮没研究

采用自电子湮没寿命测量方法研究了注量为６．５×１０＾１５／ｃｍ＾２和１．４×１０＾１４／ｃｍ＾２，Ｅｎ≥１ＭｅＶ的裂变中子辐照在掺Ｓｉ，Ｎ型单晶ＧａＡｓ产物的缺陷，此辐照在ＧａＡｓ中产生单空位和双空位缺限，缺陷浓度于比于辐照注量，高温退火产生三空位缺陷及小空位团，单空位，双空位和三空位缺陷的退火温度分别为２５０，４５０，６５０℃。     

Positron annihilation study of defects in GaAs irradiated by fission neutron

ＰｏｓｉｔｒｏｎａｎｎｉｈｉｌａｔｉｏｎｓｔｕｄｙｏｆｄｅｆｅｃｔｓｉｎＧａＡｓｉｒｒａｄｉａｔｅｄｂｙｆｉｓｉｏｎｎｅｕｔｒｏｎＺｈｕＳｈｅｎｇＹｕｎ，ＬｉＡｎＬｉ，ＬｕｏＱｉ，ＦａｎＺｈｉＧｕｏ，ＺｈｅｎｇＳｈｅｎｇＮａｎａｎｄＧｏｕＺｈ...     

氧化铝的热释光特性

陶瓷中常含有相当数量的氧化铝成分，研究氧化铝的热释光性特征对进一步提高古物测年的精确度至关重要。实验研究结果表明，氧化铝的热释光性质较为稳定，利用氧化铝的270℃峰测定年龄是切实可行的。     

Thermal annealing of disorder in Pb-ion irradiated SrTiO3

Attention was paid to thermal annealing of defects in the SrTiO₃ lattice preliminary irradiated by Pb²⁺ ions which were used to simulate the recoil-nuclei during α-decay events in actinide waste forms. Two different types of defect depending upon Pb²⁺ irradiation fluence and annealing temperature were characterized with their activation energy and a prefactor related to the fraction recovered per second. Such thermal annealing data are necessary to predict the matrix behaviour under the storage conditions. Additional informations were obtained on the defect structure using Rutherford backscattering spectrometry in channeling condition. The measurement of the de-channeling yield along different axes and planes in the crystal has permitted to analyse partially the isolated defect structure.     

MeV辐射场中Al2O3的剂量学特性

用EGSnrc/DOSRZnrc程序计算水体模中Al2O3剂量计的吸收剂量和剂量计所在处介质的实际吸收剂量,并计算吸收剂量换算因子。剂量计为φ4mm×1 mm的Al2O3薄片,计算深度0.5～8 cm,入射光子能量1～18MeV,入射电子能量1～25 MeV。结果表明：1）吸收剂量换算因子的大小与入射粒子的能量以及剂量计在体模中的深度有关;2）存在一个吸收剂量换算因子变化不敏感的区域,在此区域内吸收剂量换算因子受剂量计深度变化和入射粒子能量变化的影响都很小,可直接用平均值来表示区域内的吸收剂量换算因子。     

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor.The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis.The parameters influencing the thermal stress in the sputter process are analyzed,such as coating and substrate properties,temperature and Young's modulus.This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness,temperature and Young's modulus.However,this relationship is inversed with coating thickness.In addition,the rough substrate surface can increase the thermal stress in the process of coating deposition.The adhesive strength between the coating and the substrate is evaluated by the shear stress.Due to the higher compressive shear stress,the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating.Furthermore,the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.     

Formation and annealing behavior of defect clusters in electron or He-ion irradiated Ti-rich Ti–Al alloys

In order to clarify the effect of He atoms on the formation and annealing behavior of defect clusters in Ti–Al alloys, a Ti–47 at.% Al intermetallic compound has been irradiated with electrons and He-ions. Helium-ion irradiation enhances the nucleation of defect clusters, especially of interstitial loops, at temperatures from 623 to 773 K in both γ-TiAl and ₂-Ti₃Al grains of the sample. However, there is little difference between the annealing temperature ranges of defect clusters in TiAl grains formed by He-ion or electron irradiation at 623 K. The dot-shaped clusters and interstitial loops grow scarcely during annealing, but are annihilated by annealing up to 923 K. Cavities are formed after irradiation with He-ions below 10 dpa at 773 K, but no cavities are formed by electron irradiation up to 30 dpa. The cavities in γ-TiAl and ₂-Ti₃Al grains survive after annealing even at 1053 K for 1.8 ks, keeping their density and diameter to be nearly the same as those in the as-irradiated grains.     

Dependence of void nucleation on post－irradiation annealing temperature in αAl2O3

The evolution of void nucleation in -Al2O3 irradiated byEn 1 MeV neutronsof 3 1020 cm-2 and post-annealed from 100C to1050C is studied by a positronannihilation lifetime technique. The void nucleation starts at500C. The radius ofcreated voids is 0.31 nm and the number ofvoids increases with increasingannealing temperature from 550C to 750C.Afterwards, the radius of voids increasesrapidly and reaches 1.21nm at 1050C.     

离子束辅助沉积制备Al／Al2O3双层膜及其性质

利用离子束辅助沉积的方法在ＣＫ４５号钢和ＡｌＴｉ合金基体上制备了具有不同厚度Ａｌ层或Ａｌ２Ｏ３层的Ａｌ／Ａｌ２Ｏ３双层膜系统，Ａｌ与Ａｌ２Ｏ３层之间是厚度为１００ｎｍ的梯度界面层，利用电化学方法测量了样品在近中性水溶液中耐腐蚀性能，实验中还测量了样品的表面硬度和耐摩擦性能，研究了双层膜系统中Ａｌ或Ａｌ２Ｏ３层厚度变化对样品物理性质和化学性质的影响。