Electron beam irradiation effects on the mechanical, thermal and surface properties of a fluoroelastomer

Fluoroelastomer can be used as a sealing material for different purposes. The aim of this work is the evaluation of the effects of the ionizing radiation of an electron beam (EB) on the mechanical, thermal and surface properties of a commercial fluoroelastomer containing carbon black and inorganic fillers. The material was irradiated with overall doses between 10 and 250 kGy. Tensile strength (stress and strain at break), hardness (Shore A) and compression set were evaluated. Thermal behavior was evaluated by thermogravimetric analysis and differential scanning calorimetry. Surface modifications were inspected using scanning electron microscopy (SEM) and optical microscopy. The experiments have shown that EB irradiation promotes beneficial changes in the fluoroelastomer tensile strength behavior while compression set remain constant and the glass transition temperature increases. The SEM micrographs have shown compactness in the irradiated samples, although optical observations showed no surface morphology changes.     

Tensile Properties of llCr-0.5Mo-2W,V, Nb Stainless Steel in LMFBR Environment

The tensile strength of ferritic-martensitic HCr-0.5Mo-2W, Nb, V stainless steel (PNC-FMS), which had been developed for core component applications in LMFBR by Japan Nuclear Cycle Development Institute, was evaluated for the effects of thermal aging, sodium exposure, and neutron irradiation. The tensile strength of thermal aged specimens (~1,023K, ~12,000h) decreased at aging conditions above the initial tempering parameter, and the aging effect was considerably enhanced for the wrapper tubes tempered at lower temperatures. The tensile strength of sodium exposed specimens (~973K, ~10,000h) decreased more than aged specimens due to decarburization, and the effect of decarburization was greater in thin wall cladding tubes. Evaluation of the contribution of both thermal aging and decarburization effects on the tensile strength of cladding tubes irradiated in JOYO (~1,013K, ~6,030h, ~29dpa) suggested that the radiation showed smaller effect on tensile properties than thermal aging and decarburization. By using the derived correlations for thermal aging and decarburization effects, the tensile strength decrease for PNC-FMS after long period (30,000 h) in LMFBR environment was quantitatively calculated.     

Experimental investigations on mechanical and radiation shielding properties of hybrid lead-steel fiber reinforced concrete

This paper summarizes the results from the investigations carried out on fiber reinforced concrete with steel fibers, lead fibers and a combination of the two (hybrid fibers). The intent of this research was to investigate the effect of the two types of fibers on mechanical and radiation shielding properties of concrete. Compressive strength, split tensile strength and flexural toughness were among the mechanical properties investigated and radiation shielding to gamma rays was investigated by comparing the attenuation provided by different types of concrete against each other and against blank readings without attenuation. The results clearly showed that the hybrid fibers showed a significant enhancement in both mechanical and radiation shielding properties.     

Overall mechanical properties of fiber-reinforced metal matrix composites for fusion applications

The high-temperature strength and creep properties are among the crucial criteria for the structural materials of plasma facing components (PFC) of fusion reactors, as they will be subjected to severe thermal stresses. The fiber-reinforced metal matrix composites are a potential heat sink material for the PFC application, since the combination of different material properties can lead to versatile performances. In this article, the overall mechanical properties of two model composites based on theoretical predictions are presented. The matrix materials considered were a precipitation hardened CuCrZr alloy and reduced activation martensitic steel `Eurofer'. Continuous SiC fibers were used for the reinforcement. The results demonstrate that yield stress, ultimate tensile strength, work hardening rate and creep resistance could be extensively improved by the fiber reinforcement up to fiber content of 40 vol.%. The influence of the residual stresses on the plastic behavior of the composites is also discussed.     

EB预辐照对制备PANACF表面形貌的影响

提出了利用电子束（electron beam, EB）预辐照聚丙烯腈基纤维（polyacrylonitrile-based fiber, PANF）后再进行炭化活化制备聚丙烯腈基活性炭纤维（polyacrylonitrile-based activated carbon fiber, PANACF）的方法。吸收剂量为160 kGy并用w=10%KOH溶液浸渍30 min的PANF在450 ℃下模拟炭化活化30 min后,SEM分析显示其表面出现了与未辐照PANF不同的密集的蜂巢状结构,其BET法比表面积（specific surface area, SSA）约为未辐照样品的9倍,BJH法计算结果显示其为孔径分布集中在2～10 nm的介孔材料。该结果表明,EB预辐照对制备PANACF的表面形貌具有调控作用。     

低能电子辐照对环氧树脂性能的影响

为了研究低能电子辐照对环氧树脂的体积电阻率、邵氏硬度、拉伸强度和官能团结构的影响,本文在电子辐照能量为30 keV,注量率1×10¹¹ cm^-2•s^-1,总注量为1.6×10¹⁴ cm^-2,真空度10^-6 Pa条件下,结合国家标准对辐照前、后环氧树脂材料的机械性能和结构进行表征。结果表明,辐照后环氧树脂材料的体积电阻率、邵氏硬度、拉伸强度等宏观物理性能均有下降。傅里叶红外光谱图显示环氧树脂主要官能团强度降低,产生的•H、•OH等自由基与聚合物分子上的羟基与氢结合。研究结果对环氧树脂材料在辐射环境中的使用具有重要意义。     

高能电子束辐射对碳纤维表面结构的影响

利用激光拉曼光谱（Raman Spectroscopy）、X射线光电子能谱（XPS）、原子力显微镜（AFM）和X射线衍射（XRD）对高能电子束辐射前后的表面结构进行分析，结果表明，随着剂量的增加，碳纤维表面石墨微晶尺寸增大。碳原子在高能电子束的作用下离位，使表面棱角超于圆滑，当剂量较大时，处于石墨片层边缘的活性碳原子重新增多。碳纤维表面极性官能团受辐射介质产生的活性种的影响，同时在高能电子束辐射下激活，发生自淬灭反应和解离反应，前者占优势时，高价态的C＝O增多，反之，C－O基团增多。在试验范围内，高能电子束对碳纤维的晶型结构无影响。     

电子束辐照对尼龙610性能的影响

在三烯丙基异氰酸酯多官能团辐照敏化剂存在下,采用电子束辐照尼龙６１０,测度尼龙６１０辐照前后的力学强度、耐温等级、吸水率和吸油率的变化。结果表明：经过电子束辐照７５ｋＧｙ后,提高了ＰＡ６１０的力学强度、耐化学溶剂性能的热变形温度。     

Effect of electron beam radiation on the polypropylene/polyethylene blends: Radiation stabilization of polypropylene

The effect of incorporation of polyethylene in the polypropylene matrix, on the radiation sensitivity of polypropylene, has been investigated. The changes in the properties such as tensile strength, elongation at break, Shore D hardness, density and melt flow index were monitored as function of polyethylene content and electron beam radiation dose. A correlation between the mechanical properties and morphology of the irradiated polymeric blends has been observed, which has been explained on the basis of Fourier-transform infrared spectroscopy, scanning electron microscope and X-ray diffraction studies. Improvement in the mechanical properties of the polypropylene, irradiated to an optimum electron beam dose, could be achieved by blending it with polyethylene >20%. The optimum radiation dose was found to be dependent on blend composition and morphology, however, an absorbed dose of 250 kGy found to be effective enough to ensure good mechanical properties of the polypropylene/polyethylene blends.     

Recent Progresses and Critical Issues of SiCf／SiC Composite Under Irradiation Environments

SiC with fiber-reinforced composites, which are presently considered as the primary structural materials in some fusion reactor conceptual designs, are more attractive and competitive for structural materials in a fusion energy system because of its excellent chemical and mechanical properties such as high fracture toughness, induced-low activation, afterheat under 14MeV neutron irradiation environment at elevated temperature, and good compatibility with coolant and breeder materials. Thus it is important to investigate the research progress of advanced SiC composite, including transmuted helium gas, radiation swelling, radiation effects on mechanical properties, irradiation-enhanced creep, fatigue, physical properties associated with fusion design and their critical issues. This report summarized these results and addressed the major critical issues under irradiation conditions.     

Strength and fracture toughness of heavy concrete with various iron aggregate inclusions

An extensive experimental study of the mechanical properties and fracture properties of heavy concrete used mostly in the construction of radiation shielding structures is presented. The mixtures considered herein are developed according to the one adapted in the Kuosheng nuclear power plant in Taiwan; tests of the basic mechanical characteristics properties conform to the ASTM and the fracture properties are determined by the method proposed by Karihaloo and Nallathambi [RILEM Report 5, Fracture Mechanics Test Methods for Concrete (1991) 1]. A crack analysis using pre-cracked specimens and a dye technique was also conducted to examine the crack fronts and the corresponding residual strengths of heavy concrete. Test results indicated that the elastic modulus of heavy concrete is higher than that of regular mortar and increase with iron ore content. The compressive strength of heavy concrete also increases with iron ore content, while the tensile strength declines. The concrete including 40% metallic aggregate content by volume performs higher compressive strength and fracture toughness in this study.     

基于微试样液压爆破法测试核压力容器用钢力学性能

微试样液压爆破法是一种可用于测试核压力容器辐照监督试样的微试样测试技术,该技术借鉴爆破片工作原理,对圆形薄片试样进行液压加压,使薄片鼓胀并爆破,在试验过程中记录载荷-圆薄片中心点位移曲线,通过曲线上的特征载荷以及试样变形关联材料常规拉伸性能。通过比较不同的近似解析法得到了适合于该型微试样试验技术的屈服强度、抗拉强度的计算方法,在上述研究的基础上对核电常用材料国产A508进行了液压爆破试验,得到了材料的强度特性,与常规单轴拉伸数据高度吻合。     

Radiation effects on epoxy/carbon-fiber composite

Carbon fiber-reinforced bisphenol-A epoxy matrix composite was evaluated for gamma radiation resistance. The composite was exposed to total gamma doses of 0.5, 1.0, and 2.0 MGy. Irradiated and baseline samples were tested for tensile strength, hardness and evaluated using Fourier transform infra-red spectroscopy and differential scanning calorimetry for structural changes. Scanning electron microscopy was used to evaluate microstructural behavior. Mechanical testing of the composite bars revealed no apparent change in modulus, strain to failure, or fracture strength after exposures. However, testing of only the epoxy matrix revealed changes in hardness, thermal properties, and spectroscopy results with increasing gamma irradiation. The results quantify the changes in the epoxy within the composite as a result of exposure to gamma radiation at doses relevant to service.     

Influence of MeV protons on mechanical properties of ITO/aluminum-coated Kapton designed for space missions

Cyclotron generated MeV protons were used to evaluate the mechanical behavior such as tensile strength and elongation of ITO/aluminum-coated Kapton that is known to be one of the most useful polymers for space missions. The mechanical properties (tensile strength and elongation) of specimens irradiated with high-energy protons were lower then those irradiated with low energy protons. A considerable increase in the mechanical properties was found at irradiation with lower fluencies that is explained by the unique characteristics of the molecular structure of Kapton. The ITO and aluminum coatings on Kapton, while contributing to the mechanical strength of the coated Kapton, were found to be affected by the proton irradiation.     

Mechanical properties and microstructure in neutron-irradiated nickel-based alloys and stainless steels for supercritical water-cooled-reactor fuel cladding

ABSTRACT

To investigate the irradiation behavior of mechanical properties and microstructural changes of commercial Ni-based alloys and improved stainless steels, a neutron-irradiation experiment was performed at the Joyo reactor, and post-irradiation examinations with tensile tests and TEM observations were carried out. The room-temperature tensile tests showed that all specimens that were irradiated at 485°C exhibited significant hardening and ductile behavior, especially in alloy 625. The irradiation hardening of all specimens irradiated at 668°C was less than that of specimens irradiated at 485°C. The fine-grained stainless steel, T3 and the Zr-added stainless steels, H1 and H2 showed good mechanical-property performance with keeping ductility after neutron irradiation. Most alloys and steels showed ductile behavior on the fracture surface except for alloy 625 specimen. The TEM observations showed that a high density of tangled dislocations and irradiation-induced defect clusters formed in the stainless steels and Ni-based alloys irradiated at 485°C. At 668°C, the material microstructures coarsened and their dislocation density decreased significantly. Long rod-like precipitates of Zr(Cr, Fe) compounds formed in the H1 and H2 steels that were modified with Zr. The yield stress drop of T3 steel in tensile stress was observed and is caused by grain-size coarsening at an irradiation of 668°C.     

Effects of Fast Reactor Irradiation Conditions on Tensile and Transient Burst Properties of Ferritic/Martensitic Steel Claddings

The effects of fast neutron irradiation conditions have been investigated by focusing on the mechanical properties of 11Cr-0.5Mo-2W, Nb, V ferritic/martensitic (F/M) stainless steel (PNC-FMS) and 10.5Cr-1.5Mo, Nb, V F/M stainless steel (HT9M) claddings, especially tensile and transient burst properties. These two F/M claddings were irradiated at temperatures from 693 to 833K to 42.5 dpa (displacement per atom) in the experimental fast reactor JOYO using the PFB090 fuel test subassembly. Post-irradiation tensile and temperature-transient-to-burst tests were carried out for defueled cladding specimens. The results of mechanical tests for the PNC-FMS cladding showed that there was no significant degradation in tensile and transient burst strengths even after fast neutron irradiation. On the other hand, the strength of the HT9M cladding tended to shift to lower values than those of as-received specimens. The differences in tensile and transient burst strengths between the two claddings were attributed to martensite structural stability which was related to the stable solid solution elements.     

层状壳聚糖水凝胶的制备与性能

通过两步低温辐射和冷冻/解冻循环相结合的方法制备聚乙烯醇/聚氧乙烯(PVA/PEO)为基层,聚乙烯醇/壳聚糖(PVA/CS)为上层抗菌功能层的层状壳聚糖水凝胶。通过对吸收剂量、电子束流、聚合物溶液浓度等的研究确定最佳制备工艺,并通过溶胀性能、力学性能、抗菌性能及红外光谱和扫描电镜表征所得层状水凝胶的结构与性能。结果表明,该方法制备的层状壳聚糖水凝胶具有明显的层状结构,层间结合紧密,壳聚糖结构未改变;层状水凝胶的溶胀性能随着壳聚糖含量增大而逐渐增大,60%CS含量平衡溶胀度达到2 200%;层状水凝胶力学强度随着壳聚糖含量增加而先增大后减小,40%CS含量下层状水凝胶从PVA/PEO凝胶的0.35MPa提高到0.47 MPa;抗菌性能测试表明层状水凝胶对大肠杆菌和金黄色葡萄球菌均具有明显的抑菌效果,抑菌性能随着壳聚糖含量的提高而增大。     

辐射预硫化技术在EPDM发泡材料制备过程中的应用研究

以三元乙丙橡胶（EPDM）为基材，采用电子加速器辐照技术对其进行辐射预硫化处理，研究了敏化剂TMPTMA对硫化参数的影响及其敏化效果，并研究了不同吸收剂量下，发泡制品的外观、材料力学性能、吸水率和压缩永久变形的变化情况。结果表明：TMPTMA对三元乙丙橡胶有较好的敏化效果；在辐射吸收5～15kGy剂量范围内，发泡材料的闭孔性变好，力学性能也随之提高。     

The effect of neutron irradiation on the fiber/matrix interphase of silicon carbide composites

Given the good stability of mechanical properties of silicon carbide (SiC) under neutron irradiation, the ultimate irradiation tolerance of SiC composite materials may be limited by the fiber/matrix interphase, which is critically important to the performance of these composites. This study investigates the irradiation stability of pyrolytic carbon (PyC) monolayer and PyC/SiC multilayer interphases by tensile and single fiber push-out test techniques. Neutron irradiation was performed to doses of 0.7-7.7 dpa at temperatures from 380 to 1080 °C. Both interfacial debond shear strength and interfacial friction stress apparently decrease by irradiation, although this is not so dramatic when T_irr < 1000 °C. In contrast, the interfacial shear stresses are most affected by the higher temperature irradiation (>1000 °C). Noteworthy, these irradiation effects depend on the type of interphase material, i.e., for the pyrolytic carbon or multilayer SiC variants studied. In the range of irradiation temperature and dose, the degradation in interfacial shear properties, while measurable, is not of a magnitude to degrade the mechanical performance of the composites. This was observed for both interphase types studied. In particular, the proportional limit tensile stress decreases slightly by irradiation while the tensile fracture strength undergoes very minor change.     

Compatibility of ferritic-martensitic steel T91 welds with liquid lead-bismuth eutectic: Comparison between TIG and EB welds

The 9 wt.% chromium ferritic-martensitic steel T91 is being considered as candidate structural material for a future experimental accelerator driven system (XT-ADS). This material and its welded connections would need to be used in contact with liquid lead-bismuth eutectic (LBE), under high irradiation doses. Both unirradiated tungsten inert gas (TIG) and electron beam (EB) welds of T91 have been examined by means of metallography, scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), Vickers hardness measurements and tensile testing in both gas and liquid lead-bismuth environment. The TIG weld was commercially produced and post weld heat treated by a certified welding company while the post weld heat treatment of the experimental EB weld was optimized in terms of the Vickers hardness profile across the welded joint. The mechanical properties of the T91 TIG and EB welds in contact with LBE have been examined using slow strain rate tensile testing (SSRT) in LBE at 350 °C. All welds showed good mechanical behaviour in gas environment but total elongation was strongly reduced due to liquid metal embrittlement (LME) when tested in liquid lead-bismuth eutectic environment. The reduction in total elongation due to LME was larger for the commercially TIG welded joint than for the EB welded joint.