Void formation in solution-treated aisi 316 and 321 stainless steels under 46.5 mev ni6+ irradiation

The swelling and radiation damage structure developed in solution-treated 316 and 321 stainless steels bombarded by 46.5 MeV Ni⁶⁺ ions in the Variable Energy Cyclotron (VEC) have been determined. Foils were pre-injected with 10^?5 a/a He at room temperature and subsequently bombarded by Ni⁶⁺ ions in the temperature range 450–750°C at a damage rate of 1–3 × 10^?3 dpa per second to doses up to 300 dpa and specimens from the foils were examined by transmission electron microscopy. The data obtained were compared with data from other experiments aimed at simulating the fast-neutron irradiation of 316 and 321 steels, in particular previous work with 20 MeV C²⁺ ions and with data on fast-reactor bombarded material. The swelling rates in Ni-ion bombarded specimens were about a factor two less than those in C-ion bombarded specimens and in good agreement with swelling rates in 5 MeV Ni⁺- and neutron-bombarded material. The peak swelling temperature after a dose of 40 dpa was 650°C in 316 steel and 625°C in 321 steel where the swelling was about 5.8% and 4.6% respectively.     

The effect of damage rate on void growth in metals

The rate theory formulation of void growth was utilized to analyze the effects of damage rate on metal swelling. In particular, the swelling behavior of 316 SS was modeled as a function of temperature, over a range of displacement damage rates between 10^?6dpa/s and 10^?3dpa/s. Detailed analysis of the rate processes for point defect annihilation, migration, and loss to sinks indicated that small vacancy loops limit void growth at high damage rates. The reduction of void growth rates by vacancy emission from voids was found to be shifted towards higher temperature at higher displacement rates. In effect, the peak swelling temperature as well as the upper cutoff temperature for swelling are increased as the displacement rate is increased. The influence of constant or rate dependent nucleation conditions on the final swelling was investigated and it was shown that the initial microstructure before the growth stage essentially determines the peak swelling temperature. When appropriate empirical expressions for void and loop densities were used, the final peak swelling temperature shift agrees reasonably well with experimental data.     

Mechanisms and kinetics of precipitate restructuring during irradiation

Irradiations were performed at temperatures from 400 to 700°C using 3.0-MeV ⁵⁸Ni⁺ ions in order to investigate γ'-precipitate restructuring in two model alloys: Ni-12.8 at% Al and Ni-12.7 at% Si. The precipitates coarsened, with the third power of the average diameter proportional to the damage dose. The temperature dependence of the rate constants for irradiated specimens is described in terms of a modified Lifschitz-Slyozov-Wagner coarsening model that includes radiation-enhanced diffusion. Redistribution of precipitate by enhanced precipitation (Ni-Si) or precipitate dissolution (Ni-Al) at point-defect sinks caused maxima in γ' size with dose. Precipitate redistribution at the free surfaces of irradiated thin foils and at γ/γ' particle interfaces is described.     

The disordering of Zr3Al by 1 MeV electron irradiation

The effect of 1 MeV electron radiation on the L1₂ ordered intermetallic compound, Zr₃Al, has been studied over the temperature range 130–775 K, using a high voltage electron microscope. At temperatures in the range 130–375 K, complete disorder was produced by irradiation to a dose of approximately one displacement per atom (dpa), independent of damage rate over the range 5 × 10^?4 to 5 × 10^?3 dpa/s. After irradiation to a few dpa at higher temperatures, 575–775 K, a steady-state was established which was characterized in part by an intermediate degree of long-range order which increased with irradiation temperature. By comparison with published results from ion irradiation experiments, it appears that the number of atomic displacements to cause complete disordering at low temperatures is independent of the nature of the damage events. At the higher temperatures, neither dislocation loops, dislocation networks nor voids were observed. Generally, the crystalline perfection was markedly reduced at all temperatures by irradiation to doses exceeding a few dpa.     

The influence of temperature on the blister behavior of vanadium and binary V Ti-alloys during 200- and 2000-keV helium irradiation

The formation and growth of gas bubbles is one of the major problems for the integrity of the first wall in a fusion reactor. The helium-induced surface damage as well as the helium-induced bulk damage beneath the surface has been investigated by scanning and transmission electron microscopy techniques. Samples of vanadium, V-3 wt.%-Ti and V-20 wt.%-Ti were implanted with 200-keV and 2000-keV helium ions at temperatures between 450 and 700° C to fluences above the threshold dose for blistering (2 × 10¹⁷He⁺/cm²). The dependence of surface damage phenomena of blistering, exfoliation and perforation on dose, temperature, ion energy and yield strength is discussed. The results can be explained by the helium behavior in the bulk. This behavior is found to be characterized by the formation of large gas bubbles grown by a coalescence process and by the formation of small helium clusters at high dose implantation.     

Dose rate and temperature effects on blistering phenomena in helium bombarded niobium

Blistering of niobium under bombardment with 5 to 15 keV He ions has been investigated. At these energies there is only one generation of blisters, which are sputtered and give way to a microrelief. A high dose rate of 3–5 mA/cm² has been used to find the energy and temperature dependance of the blistering cut-off effect. At 20° C this cut-off dose increases from about 1 to 3 C/cm² when the energy is increased from 5 to 15 keV. The temperature effect has been investigated with 10 keV ions. The cut-off dose decreased to about 0.2 C/cm² at 700° C. Since in a fusion device, the dose rate may be much smaller than the one used above, the dose rate effect has been investigated. With a dose rate reduced to 0.05 mA/cm² the critical dose for blistering and the cut-off dose have not been found to vary by any large amount.     

Dose rate effect on micro-structure and hardness of Hastelloy-N irradiated by Xe ions

Hastelloy-N alloys were irradiated by Xe⁺ with energies of 7 and 2 MeV at room temperature in order to investigate the effects of dose and dose rate on the change of micro-structure and nanohardness. Hardness was measured by nanoindentation, and micro-structure evolution and irradiation defects were identified by transmission electron microscopy (TEM) and positron annihilation coincidence Doppler broadening (CDB), respectively. The nanoindentation results showed that the hardness of alloys increased after irradiation, especially at a lower dose rate. At higher dose rate, TEM results indicated that irradiation defects were observed at first in this experiment, and the size of the defects increased, while their number density decreased as the dose increased. However, for a same total dose, the defects formed at a lower dose rate were larger, and their number density was also higher than that at a higher dose rate. Meanwhile, CDB analysis verified the growth of vacancy-type defects with increasing dose.     

Void swelling in a 9Cr ferritic/martensitic steel irradiated with energetic Ne-ions at elevated temperatures

In this work the void swelling behavior of a 9Cr ferritic/martensitic steel irradiated with energetic Ne-ions is studied. Specimens of Grade 92 steel (a 9%Cr ferritic/martensitic steel) were subjected to an irradiation of ²⁰Ne-ions (with 122 MeV) to successively increasing damage levels of 1, 5 and 10 dpa at a damage peak at 440 and 570 °C, respectively. And another specimen was irradiated at a temperature ramp condition (high flux condition) with the temperature increasing from 440 up to 630 °C during the irradiation. Cross-sectional microstructures were investigated with a transmission electron microscopy (TEM). A high concentration of cavities was observed in the peak damage region in the Grade 92 steel irradiated to 5 dpa, and higher doses. The concentration and mean size of the cavities showed a strong dependence on the dose and irradiation temperature. Enhanced growth of the cavities at the grain boundaries, especially at the grain boundary junctions, was observed. The void swelling behavior in similar 9Cr steels irradiated at different conditions are discussed by using a classic void formation theory.     

JFET输入运算放大器的增强辐射损伤方法研究

本文对结型场效应管JFET输入运算放大器的增强辐射损伤方法进行了研究.结果表明,采用循环辐照一退火的方法可以使JFET输入运算放大器的辐射损伤增强,并且通过调整辐照剂量率、退火温度及时间等参数,可以评测出器件的低剂量率辐射损伤情况.文章还对这种辐射损伤方法的机理进行了分析.     

Swelling or erosion on the surface of patterned GaN damaged by heavy ion implantation

Wurtzite undoped GaN epilayers (0 0 0 1) was implanted with 500 keV Au⁺ ions at room temperature under different doses, respectively. Ion implantation was performed through photoresist masks on GaN to produce alternating strips. The experimental results showed that the step height of swelling and decomposition in implanted GaN depended on ion dose and annealing temperature, i.e., damage level and its evolution. This damage evolution is contributed to implantation-induced defect production, and defect migration/accumulation occurred at different levels of displacement per atom. The results suggest that the swelling is due to the formation of porous structures in the amorphous region of implanted GaN. The decomposition of implanted area can be attributed to the disorder saturation and the diffusion of surface amorphous layer.     

Irradiation damage in proton irradiated palladium-iron solid solutions

Transmission electron microscopy was used to investigate the irradiation damage, in particular irradiation induced precipitation (IIP), in Pd-base alloys containing 2, 8, 12 and 18 at % Fe. The specimens were irradiated mainly using 400 keV protons at a current density of 0.16 μA/mm² over the temperature range 110 to 750°C. A few samples containing 2 and 8% Fe were also irradiated using 3 MeV NiP⁺ ions. The irradiation microstructure of the proton irradiated alloys consists of dislocation loops over the temperature range 110 to 550°C and voids up to 650°C in all the alloys. IIP of Pd₃Fe was observed only in the Pd-18% Fe alloy between 110 and 500°C, irradiated to a dose of 0.9 dpa. Pd₃Fe was associated with dislocation loops, voids and grain boundaries. IIP was not observed in the Pd-2,8 and 12% Fe alloys proton irradiated to the same dose, nor to a higher dose of 1.5 dpa. It was also not observed in the 2 and 8% Fe alloys irradiated at 600 and 700°C by 3 MeV Ni⁺ ions.The absence of IIP in the more dilute alloys is attributed to the fast back diffusion of Fe atoms, which is due to the high mobility of vacancies in these alloys. This causes the Fe concentration at the sinks to remain below the solubility limit. Therefore, even though Fe is an undersized solute, the size effect alone is not sufficient for the production of IIP at point defect sinks in most Pd-Fe alloys. It is proposed that IIP can occur only when the alloy concentration is high enough to minimize the rate of back diffusion, which depends not only on the vacancy mobility but also on the concentration gradient near point defect sinks.     

Ion irradiation damage effects in δ-phase Y6W1O12

Polycrystalline Y₆W₁O₁₂ samples were irradiated with 280 keV Kr²⁺ ions to fluences up to 2 × 10²⁰ ions/m² at cryogenic temperature (100 K). Ion irradiation damage effects in these samples were examined using grazing incidence X-ray diffraction (GIXRD) and cross-sectional transmission electron microscopy (TEM). The pristine Y₆W₁O₁₂ possesses rhombohedral symmetry (structure known as the δ-phase), which is closely related to cubic fluorite structure. GIXRD and TEM observations revealed that the irradiated Y₆W₁O₁₂ experiences an ordered rhombohedral to disordered cubic fluorite transformation by a displacement damage dose of ∼12 displacements per atom (dpa). At the highest experimental dose of ∼50 dpa, the uppermost irradiated region was found to be partially amorphous while the buried damage region was found to contain the same fluorite structure as observed at lower dose.     

The effect of neutron irradiation on mechanical properties of YAG laser weldments using previously irradiated material

The objective of this study is to make clear the effect of neutron irradiation on mechanical properties of laser weldments using irradiated material. This estimation is necessary for the application to joining coolant piping of the ITER blanket. Irradiation testing was performed at Japan Material Testing Reactor (JMTR). On the irradiation condition for weldments using irradiated material, fast neutron fluence was 1.4 × 10²⁴ n/m², which corresponds to a displacement damage rate of 0.26 displacement per atom (dpa) and irradiation temperature 200 °C. The results of this study show that tensile properties of all weldments changed into that of base material by the effect of neutron irradiation. The results of hardness tests show that irradiation hardening at an irradiation damage dose of 0.3 dpa is almost same as that at irradiation damage 0.6 dpa. It is concluded that irradiated weldments using irradiated material were moved toward irradiated base material on tensile and hardness properties up to 0.6 dpa. On the other hand, tensile properties of base material were changed by the effect of neutron irradiation up to about 0.3 dpa, and with much less change from 0.3 dpa to 0.6 dpa. It is inferred that the effect of neutron irradiation of SS316LN-IG almost saturated up to 0.3 dpa.     

Helium irradiation of Ni-(Zr or Nb) metallic glasses: Blistering,flaking and bubble formation

NiZr and NiNb are potential metallic glasses for nuclear applications. We have studied blistering, flaking and bubble formation in Ni₆₄Zr₃₆, Ni₃₃Zr₆₇ and Ni₆₀Nb₄₀ glasses under helium ion bombardment at room temperature. The effect of projectile energy (50–150 keV), total dose (0.01–10 × 10¹⁸ ions/cm²), dose rate (10–100 μA/cm²) and thermal crystallization on critical dose for blistering and/or flaking, average blister diameter and development of surface topography was examined. The surface damage effects in metallic glasses were in general similar to those for crystalline materials with the notable exception that the critical dose values are higher by about 50–100% for metallic glasses. TEM investigations revealed irradiation induced partial crystallization of Ni₃₃Zr₆₇ glass. Metallic glasses Ni₆₄Zr₃₆ and Ni₆₀Nb₄₀ were stable under helium irradiation and have also shown very high resistance against blistering and/or flaking. The possible mechanisms of helium trapping in metallic glasses are also discussed.     

Effect of gamma-ray irradiation on the deoxygenation of salt-containing water using hydrazine

In spent fuel pools at the Fukushima Daiichi nuclear power plant, hydrazine was added to salt-containing water in order to reduce dissolved oxygen. Hydrazine is known to reduce dissolved oxygen in high-temperature pure water, but its deoxygenation behavior in salt-containing water at ambient temperature in the presence of radiation is unknown. Deoxygenation using hydrazine in salt-containing water was thus investigated using a ⁶⁰Co gamma-ray source and artificial seawater at room temperature. Water samples containing a small amount of hydrazine were irradiated at dose rates of 100–10,000 Gy/h. The concentration of dissolved oxygen in the water samples was measured before and after irradiation. Notably, a decrease in the dissolved oxygen was only observed after irradiation, and the dissolved oxygen concentration decreased with increasing dose rate and irradiation time. The rate of decrease in the amount of dissolved oxygen using hydrazine was slow in the presence of salts. Kinetic considerations suggested that the deoxygenation of the salt-containing water exposed to gamma-ray irradiation using hydrazine was suppressed by chloride ions.     

变温辐照加速评估方法在不同工艺的NPN双极晶体管上的应用

对6种不同工艺的NPN双极晶体管进行了高、低剂量率及变温辐照的~(60)Coγ辐照实验。结果显示,6种工艺的NPN双极晶体管均有显著的低剂量率辐照损伤增强效应。而变温辐照损伤不仅明显高于室温高剂量率的辐照损伤,且能很好地模拟并保守地评估不同工艺的NPN双极晶体管低剂量率的辐照损伤。对实验现象的机理进行了分析。     

The range distribution and annealing behavior of Er ions implanted in silicon-on-insulator

The range distribution for energetic 400 keV Er ions implanted in silicon-on-insulator (SOI) at room temperature were measured by means of Rutherford backscattering followed by spectrum analysis. The damage distribution and annealing behavior of implanted Er ions in SOI at the energy of 400 keV with dose of 5 × 10¹⁵ cm⁻² were obtained by Rutherford backscattering technique. It has been found that the damage around the SOI surface had been almost removed after annealed in nitrogen atmosphere at 900 °C, and a lot of Er atoms segregate to the surface of sample with the recrystallization of surface Si of SOI sample after annealing at 900 °C.     

Dwell-time dependence of the defect accumulation in focused ion beam synthesis of CoSi2

Cobalt disilicide microstructures were formed by 70 keV Co²⁺ focused ion beam implantation into Si(1 1 1) at substrate temperatures of about 400°C and a subsequent two step annealing (600°C, 60 min and 1000°C, 30 min in N₂). It was found that the CoSi₂ layer quality strongly depends on the pixel dwell time and the implantation temperature. Only for properly chosen parameters continuous CoSi₂ layers could be obtained. Scanning electron microscopy and Rutherford backscattering/channelling investigations were carried out combined with a special preparation technique for structures which are smaller than the analysing beam. The quality of the CoSi₂ layers which is correlated to the damage was investigated as a function of dwell-time (1–250 μs) and target temperature (355–415°C). The results show that the irradiation damage increases with the dwell-time. The Si top layer was amorphized for longer dwell-times although the substrate temperature was always above the critical temperature for amorphization of about 270°C according to the model of Morehead and Crowder. For the high current density of a focused ion beam (1–10 A/cm²) the damage creation rate is higher than the rate of dynamic annealing.     

RBS studies of the lattice damage caused by 1 Me V Si implantation into Al0.3Ga0.7As/GaAs superlattices at elevated temperature

The lattice damage accumulation in GaAs and Al_0.3Ga_0.7As/GaAs superlattices by 1 MeV Si⁺irradiation at room temperature and 350°C has been studied. For irradiations at 350°C, at lower doses the samples were almost defect-free after irradiation, while a large density of accumulated defects was induced at a higher dose. The critical dose above which the damage accumulation is more efficient is estimated to be 2 × 10¹⁵ + Si/cm² for GaAs, and is 5 × 10¹⁵ Si/cm² for Al_0.8Ga_0.7As/GaAs superlattice for implantation with 1.0 MeV Si ions at 350°C. The damage accumulation rate for 1 MeV Si ion implantation in Al_0.3Ga_0.7As/GaAs superlattice is less than that in GaAs.     

双极线性集成电路低剂量率辐射的增强损伤

综合介绍了双极线性集成电路在低剂量率辐射下产徨的异常损伤,既在低剂量率下辐射时,这些器件在很低的总剂量水平下即告失效,失效阈较高剂量率辐射要低得多,它是因为构成线性电路的双极器件发射极一基极结上覆盖了厚氧化物,低剂量率电离辐射在氧化物内产生电荷的传输时间有时要达到数百秒,氧化物内存在的过量电荷使器件产生增强损伤。