Molecular dynamics study of interactions between edge dislocation and irradiation-induced defects in Fe–10Ni–20Cr alloy

Irradiation-induced defects frequently impede the slip of dislocations, resulting in a sharp decline in the performance of nuclear reactor structural materials, particularly core structural materials. In the present work, molecular dynamics method is used to investigate the interactions between edge dislocations and three typical irradiation-induced defects(void,Frank loop, and stacking fault tetrahedron) with the sizes of 3 nm, 5 nm, and 7 nm at different temperatures in Fe–10Ni–20Cr alloy. The critical resolved shear stresses(CRSSs) are compared among different defect types after interacting with edge dislocations. The results show that the CRSS decreases with temperature increasing and defect size decreasing for each defect type during the interaction with edge dislocations, except for the case of 3-nm Frank loops at 900 K. According to a comparison, the CRSS in Frank loop is significantly higher than that of others of the same size, which is due to the occurrence of unfaulting and formation of superjog or stacking-fault complex during the interaction. The atomic evolution of irradiation-induced defects after interacting with dislocations can provide a novel insight into the design of new structural materials.

H-ion Irradiation-induced Annealing in He-ion Implanted 4H-SiC

Radiation-induced defect annealing in He+ ion-implanted 4H-SiC via H+ ion irradiation is investigated by Raman spectroscopy. There are 4H-SiC wafers irradiated with 230 keV He+ ions with fluences ranging from cm−2 to cm−2 at room temperature. The post-implantation samples are irradiated by 260 keV H+ ions at a fluence of cm−2 at room temperature. The intensities of Raman lines decrease after He implantation, while they increase after H irradiation. The experimental results present that the magnitude of Raman line increment is related to the concentration of pre-existing defects formed by He implantation. A strong new peak located near 966 cm−1, which is assigned to 3C-SiC LO () phonon, is found in the He-implanted sample with a fluence of cm−2 followed by H irradiation. However, for the He-implanted sample with a fluence of cm−2 followed by H irradiation, no 3C-SiC phonon vibrations are found. The detailed reason for H irradiation-induced phase transformation in the He-implanted 4H-SiC is discussed.

Temperature-Dependent Photoluminescence Analysis of 1.0 MeV Electron Irradiation-Induced Nonradiative Recombination Centers in n＋-p GaAs Middle Cell of GaInP/GaAs/Ge Triple-Junction Solar Cells

The effects of irradiation of 1.0 MeV electrons on the n＋-p GaAs middle cell of GalnP/GaAs/Ge triple-junction solar cells are investigated by temperature-dependent photoluminescence （PL） measurements in the 10-300K temperature range. The appearance of thermal quenching of the PL intensity with increasing temperature confirms the presence of a nonradiative recombination center in the cell after the electron irradiation, and the thermal activation energy of the center is determined using the Arrhenius plot of the PL intensity. Furthermore, by comparing the thermal activation and the ionization energies of the defects, the nonradiative recombination center in the n＋ p GaAs middle cell acting as a primary defect is identified as the E5 electron trap located at Ec - 0.96 eV.

Copper Ion Beam Irradiation-Induced Effects on Structural,Morphological and Optical Properties of Tin Dioxide Nanowires

The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three different doses 5 × 10^12 ions/cm2, 1 ×10^13 ions/cm2 and 5 × 10^13 ions/em2 at room temperature. The XRD analysis shows that the tetragonal phase of Sn02 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine Sn02 NWs exhibit the chemical composition of SnO2 while the Cn-O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveMs that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.

Photoluminescence Analysis of Injection-Enhanced Annealing of Electron Irradiation-Induced Defects in GaAs Middle Cells for Triple-Junction Solar Cells

Photolumineseenee measurements are carried out to investigate the injection-enhanced annealing behavior of electron radiation-induced defects in a GaAs middle cell for GaInP/GaAs/Ge triple-junction solar cells which are irradiated by 1.8 MeV with a fluence of i ~ 1015 cm-2. Minority-carrier injection under forward bias is observed to enhance the defect annealing in the GaAs middle cell, and the removal rate of the defect is determined with photoluminescenee radiative efficiency recovery. Furthermore, the injection-enhanced defect removal rates obey a simple Arrhenius law. Therefore, the annealing activation energy is acquired and is equal to 0.58eV. Finally, in comparison of the annealing activation energies, the E5 defect is identified as a primary non-radiative recombination center.

Influence of helium on the evolution of irradiation-induced defects in tungsten:An object kinetic Monte Carlo simulation

Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation.Hereby,we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten(W)via using the object kinetic Monte Carlo(OKMC)method.Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects.On the one hand,the presence of He can facilitate the recombination of vacancies and self-interstitial atoms(SIAs)in W.This can be attributed to the formation of immobile He-SIA complexes,which increases the annihilation probability of vacancies and SIAs.On the other hand,due to the high stability and low mobility of He-vacancy complexes,the growth of large vacancy clusters in W is kinetically suppressed by He addition.Specially,in comparison with the injection of collision cascades and He in sequential way at 1223 K,the average sizes of surviving vacancy clusters in W via simultaneous way are smaller,which is in good agreement with previous experimental observations.These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials,and contributes to our understanding of W performance under irradiation.

Effects of grain boundaries on irradiation-induced defects in tungsten by molecular dynamics simulations

The effects of two different symmetric tilt grain boundaries （GBs）, ∑13[001]（230） GB and ∑17[001]（140） GB, on displacement cascade processes in tungsten were investigated using molecular dynamics simulations. By quantifying the number of interstitials and vacancies surviving after irradiation with the kinetic energy of primary knock-on atom energies of 1, 3 and 5 keV, respectively, in these simulations, it is found that the GBs have dual nature for radiation-induced defects： They absorb interstitials while leaving more vacancies to survive in the grains. The net effect is that the number of total surviving defects in the GB system is not always less than that in the single crystal. These defect behaviors are understood by quantitatively analyzing the recovery fraction of irradiation-induced defects, the time to reach steady state and the mobility of vacancies and interstitials. It is also found that the ∑17 GB is a more effective sink of radiation-induced point defects than the ∑13 GB. One of the main reasons is that the ∑17 GB has a higher GB energy.

Shenqi Fuzheng Injection Ameliorates Radiation-induced Brain Injury

Shenqi Fuzheng injection(SFI)has been confirmed to be able to alleviate brain injury in mice.This study examined the brain-protective effect of SFI on patients after cranial radiation.Lung cancer patients with brain metastasis were randomly assigned to two groups.The SFI group received cranial radiation in combination with SFI.The control group received cranial radiation alone.The changes in cognitive function were evaluated pre- and post-radiation against the Mini-Mental State Exam(MMSE),Montreal Cognitive Assessement(MoCA),Zung Self-Rating Depression Scale(SDS)and Zung Self-Rating Anxiety Scale(SAS).The changes in inflammatory factors,such as TGF-β1,TNF-α and IL-10,were also detected before,during and after radiation(15Gy/5F).The results showed that 6 months after cranial radiation,the total scores on the MMSE and MoCA scales of the patients decreased,especially memory ability.The control group experienced a more evident decline,the memory ability being the greatest.TGF-β1 and TNF-α increased shortly after radiation and decreased one month later,and the change was more conspicuous in SFI group than in control group.IL-10 increased after radiation and stayed at a high level one month later in both groups,the level being higher in the SFI group than in the control group.Our study indicated that cognitive functions,especially memory ability,were impaired after cranial radiation.SFI could alleviate radiation-induced brain injury by regulating inflammatory factors.

Influence of He ion irradiation on the microstructure and hardness of Ni-TiC_(NP)composites

In the present study,samples of a titanium carbide nanoparticle-reinforced nickel alloy(Ni-TiC_(NP)composite)were irradiated with 1 MeV He ions at 700°C.The evolution of He bubbles and nanohardness was characterized using transmission electron microscopy(TEM)and nanoindentation,respectively.TEM images showed that the size and number density of He bubbles in the grains were affected by the He ion fluence.The number density first increased significantly and then decreased with increasing ion dose,while the size exhibited an inverse trend.Moreover,the swelling induced by He bubbles continuously increased with increasing ion dose.He bubbles also formed in the grain boundaries,interior of the TiC nanoparticles,and interfaces between the TiC nanoparticles and Ni matrix.Nanoindentation measurements indicated a decrease in nanohardness after irradiation,which is attributed to the disappearance of intrinsic dislocation lines caused by He ion irradiation.

SOME INVESTIGATIONS ON THE NATURE OF REACTION PROCEEDING OF RADIATIONINDUCED GRAFTING IN THE POLYETHYLENE AND ACRYLIC ACID SYSTEM

Direct radiation grafting of acrylic acid (AA) and methacrylic acid (MAA) onto polyethylene (PE) films was studied. The investigation of the nature and characters of grafting proceeding was performed. The penetration of grafting onto the thin PE film was studied and the mechanism discussed. This involves an initial stage whereby the grafted surface layer deforms the PE allowing further monomer to penetrate. It was shown that the surface grafting was dynamic controlled and the penetration of monomer depended on the polarity of monomer.

耐瑞特:一种基于群体学习方法的新型硝酸盐制剂,可发挥更好的机体保护作用

硝酸盐是一种机体不可或缺的营养物质,已应用于多种疾病的预防和治疗研究.但由于半衰期短,硝酸盐的临床应用受限.为了提高硝酸盐可用性,突破传统的依赖大规模高通量生物实验的药物配伍研发瓶颈,本文报道了一种基于群体学习方法的药物配伍预测系统,该系统预测维生素C为与硝酸盐配伍的首选药物.通过采用微囊化技术,筛选并优化缓释制剂工艺,以维生素C、硝酸钠及壳聚糖3000为芯材,果胶与羧甲基纤维素钠为壁材制备硝酸盐纳米颗粒,命名为耐瑞特(Nanonitrator).耐瑞特的更长循环期显著提高了硝酸盐对放射性唾液腺损伤的疗效,同时维持了安全性.相同剂量的耐瑞特比硝酸盐(包含或不包含维生素C)可显著增强PI3K-Akt信号通路转导,更好地维持细胞内稳态,提示了其广泛的临床应用潜力.此外,本文还提供了一种将无机化合物加入缓释纳米颗粒的新方法.

EFFECT OF IRRADIATION WITH SLOW NEUTRONS OF LOW FLUENCE ON YBCO-SYSTEM SUPERCONDUCTORS

Ⅰ. INTRODUCTION Critical current density J_c varies with structural imperfections in non-ideal type-Ⅱ superconductors, and it is sensitive to the defect concentration. Neutron irradiation has been established as a useful tool to increase the defect concentration in superconducting materials. Many experiments have shown that neutron irradiation at a suitable fluence would

The Double Effects and Mechanism of Slow Neutron Irradiation on HTSC

1 Introduction It is very important for practical application of HTSC to increase the critical cur-rent density （Jc）by artificially introducing pinning centers to enhance flux pinning.Ex-periment results show that neutron radiation is 1000 times more effective than theelectron and proton radiation.So in recent years,the neutron radiation has becomepopular,theoretically and practically.After irradiation of fast neutrons in high flux,the magnetization ratio of polycrystal samples of Y and Bi Systems are Mirr/Munirr≈2.8—3.1.But Tc is descending with the neutron flux increasing and the decreasingratio is about（2.6—3.0 K）/(1018 n/cm2).

Investigation of Effect and Mechanisms of Slow Neutro Irradiation on High-T_c Superconductors

The irradiation effect of slow neutrons at low fluence on high-T_c super-conductors and its mechanism are presented.Based on an analysis and comparison of irra-diation effects by fast and slow neutrons from the viewpoint of nuclear physics,a novelmechanism in great contrast to that by fast neutron irradiation is proposed.It was bothexperimentally and theoretically shown that slow neutrons of low fluence and fast neutronsof high fluence have the similar irradiation effects on high-T_c superconductors.