辐射法制备Fricke凝胶剂量计

辐射剂量验证技术是肿瘤放射治疗过程中的关键技术,Fricke凝胶剂量计因其制备简单、组织等效性好正逐步成为研究的热点。本研究采用辐射交联"一步法"制备Fricke凝胶剂量计,利用傅里叶红外光谱仪(Fourier transform infrared spectrometer,FTIR)、X线衍射仪(X-ray diffractometer,XRD)与热重分析仪(Thermo-gravimetric analyser,TGA)等仪器对凝胶样品的化学结构和成分进行了分析,利用分子动力学模拟研究了亚铁离子在凝胶剂量计中的扩散行为,并在医用加速器下对凝胶进行辐照,利用多功能酶标仪测定凝胶的辐射剂量响应。结果表明,辐射法制备的Fricke凝胶剂量计中,聚丙烯酸链可以抑制亚铁离子在凝胶样品中的扩散行为,添加二甲酚橙(Xylenol orange,XO)可以改善Fricke凝胶剂量计的剂量敏感性。     

伽玛射线辐照种子溶胀聚合制备话梅型和核桃型聚合物微球

制备了微米级的磺化交联聚苯乙烯(SCPS)微球,并作为种子微球,将其分散在水/苯乙烯二元混合体系中,经过单体溶胀后,再利用60Co?-射线引发聚合,得到具有粗糙表面的聚合物微球。研究了SCPS种子微球中交联剂(二乙烯基苯)含量和磺化度对最终微球形貌的影响。结果表明,SCPS种子微球的磺化度和交联度较小时,形成类似核桃型微球,随着这两者的增加,将转变成类似话梅型微球,并且微球形貌在一定范围内与剂量率无关(44-108 Gy·min-1)。本工作为可控制备具有粗糙表面和比表面积的聚合物微球提供了一种高效简便的方法。     

离子辐照聚合物薄膜引起的降解和能量传输过程

用１２０ｋｅＶＮ＾＋，Ａｒ＾＋，Ｆｅ＾＋辐照聚酰亚胺薄膜，辐照剂量为５×１０＾１４－１×１０＾１７ｉｏｎｓ／ｃｍ＾２，对辐照样品做了表面电阻和光学吸收数量，结果表明：辐照后样品的表面电阻有明显变化，且随辐照剂量变化呈现阈值，在高剂理下达到饱和值。     

硫代苯甲酸存在下辐射引发活性自由基聚合

在二硫代苯甲酸(PhCSSH)存在下，用^60Coγ射线辐射引发苯乙烯(St)、甲基丙烯酸丁酯(BMA)聚合，采用核磁共振氢谱(^1HNMR)和凝胶渗透色谱(GPC)对聚合物结构和聚合物的分子量及其分子量分布进行表征。结果表明，在PhCSSH存在下，由辐射引发St、BMA聚合具有活性聚合特征：聚合物具有较窄的分子量分布，分子量随转化率线性增加，聚合物分子链中含有活性端基。并对聚合机理进行了探讨。     

γ射线引发甲基丙烯酸十二酯乳液聚合及其吸油性能的研究

讨论了以OP-10、十二烷基苯磺酸钠为乳化剂,γ射线引发甲基丙烯酸十二酯与少量N-羟甲基丙烯酰胺和丙烯酸乳液聚合制备高吸油性树脂。分别采用红外,SEM和TG表征了聚合物的成分、结构和热性能。SEM显示乳液胶束粒子尺寸均一,粒径约为170nm。聚合物在300℃以下时热稳定性良好。研究了反应条件如吸收剂量、剂量率、固含量、N-羟甲基丙烯酰胺和丙烯酸用量等对聚合物的吸煤油性能的影响。聚合物对煤油、氯仿、二甲苯的最大饱和吸油率（g儋）分别为18．1、19．5和15．3。     

PVDF粉体预辐照接枝甲基丙烯酸缩水甘油酯制备锂离子二次电池隔膜研究

以聚偏氟乙烯（PVDF）粉体为基材,采用预辐照接枝方法,在PVDF粉体上用乳液聚合接枝甲基丙烯酸缩水甘油酯（GMA）,并采用溶液铸膜的方法制备了PVDF-g-PGMA膜。利用红外光谱（FTIR）,扫描电子显微镜（SEM）,压汞仪,电导率测试等分析表征手段对制备的PVDF—g-PGMA膜进行了表征。在氩气手套箱中组装成扣式电池,在电池测试系统上测试扣式电池的充放电循环性能。测试结果表明,在相同制备条件下,以PVDF-g-PGMA作为隔膜的锂离子电池性能优于以PVDF作为隔膜的锂离子电池性能。     

Production of polymer-plaster composite by gamma irradiation

The estimated amount of plaster wastes in the construction industry is 45%. The reduction of these wastes is of concern, as the cost of lost material and the waste management can affect the competitiveness of the industry. The blend of plaster with a particular resin generates a composite, which gives the pre-molded obtained from this mixture, special properties. In this case, the plasticity of the plaster generates pre-molded products with wealth of details. Additionally, the use of nuclear techniques for initiation of the polymerization reaction to obtain this type of composite can eliminate the need for a heat source, which is the conventional way to obtain polymerization, considerably reducing the costs of the process. As a function of the availability of styrene monomer, in the initial phase of the research test samples were prepared from plaster composites with this type of material. The test samples, composed of plaster and styrene, were irradiated with a Cs-137 (662 keV) gamma source for a period of time of two days in an air pressurized chamber (total dose of 43.2 kGy). Tests of resistance to compression, tensile strength in bending and water absorption, were based on a type of experimental design, CCRD (Central Composite Rotatable Design). The percent average weight of polymer by weight of the test sample was 14%. The presence of a polymerized resin gives the sample qualities such as being highly impervious to water and having high mechanical strength, allowing its use in the manufacture of different types of materials.     

Investigation of optimal scanning protocol for X-ray computed tomography polymer gel dosimetry

X-ray computed tomography is one of the potential tool used to evaluate the polymer gel dosimeters in three dimensions. The purpose of this study is to investigate the factors which affect the image noise for X-ray CT polymer gel dosimetry. A cylindrical water filled phantom was imaged with single slice Siemens Somatom Emotion CT scanner. The imaging parameters like tube voltage, tube current, slice scan time, slice thickness and reconstruction algorithm were varied independently to study the dependence of noise on each other. Reductions of noise with number of images to be averaged and spatial uniformity of the image were also investigated. Normoxic polymer gel PAGAT was manufactured and irradiated using Siemens Primus linear accelerator. The radiation induced change in CT number was evaluated using X-ray CT scanner. From this study it is clear that image noise is reduced with increase in tube voltage, tube current, slice scan time, slice thickness and also reduced with increasing the number of images averaged. However to reduce the tube load and total scan time, it was concluded that tube voltage of 130 kV, tube current of 200 mA, scan time of 1.5 s, slice thickness of 3 mm for high dose gradient and 5 mm for low dose gradient were optimal scanning protocols for this scanner. Optimum number of images to be averaged was concluded to be 25 for X-ray CT polymer gel dosimetry. Choice of reconstruction algorithm was also critical. From the study it is also clear that CT number increase with imaging tube voltage and shows the energy dependency of polymer gel dosimeter. Hence for evaluation of polymer gel dosimeters with X-ray CT scanner needs the optimization of scanning protocols to reduce the image noise.     

Synthesis of polytetrafluoroethylene based olefinic copolymer by gamma radiation grafting

High speed extrusion of linear low density polyethylene (LLDPE) is limited by processes shortcoming known as ‘melt fracture’ and ‘sharkskin’, which are surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and with poor surface properties. The fluoropolymer processing additives are used to eliminate the surface defect by coating the die wall and inducing slip at the coated fluoropolymer surface/LLDPE interface. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer grafted with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by grafting an olefinic monomer the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to allow recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. The olefinic monomer used was 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). The obtained copolymer (0.2-2.0 wt%) was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the developed process rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect ‘melt fracture’.     

单细胞凝胶电泳法检测研究同步辐射软X射线辐照引起的DNA损伤

本实验采用单细胞凝胶电泳方法定量检测了不同辐照剂量的同步辐射软X射线对小麦根尖细胞造成的DNA单链损伤.通过测定核DNA的迁移效应表明,在剂量为0-288 J·cm-2范围内的软X射线辐照下,有20%-92%的小麦根尖细胞产生了DNA单链的损伤效应,同时DNA的损伤程度也与辐照剂量呈显著正相关.     

Relaxation of surface tracks on polycarbonate thin films induced by MeV heavy-ion impacts

In the present work, the relaxation behavior of nanometer-sized deformations produced by single ion impacts on the surface of monodisperse (M_w = 60,000 u) polycarbonate thin films was investigated at temperatures close to and below the glass transition. The relaxation functions for the length, height and width of the deformations were well described by a stretched exponential law, with characteristic relaxation times τ strongly dependent on temperature. For T > 100 °C, the temperature dependence of τ obeys a Vogel-Fulcher law, but for lower temperatures it becomes less steep and tends to an Arrhenius-type behavior.     

丙烯酰胺固态辐射聚合的NMR研究

用＾１３ＣＣＰＭＡＳ方法监测了丙烯酰胺的辐射聚合过程，确定了丙烯酰胺固态临界辐射聚合剂量在１．１－５．５ｋＧｙ。研究了辐射聚合产物结构及其大分子逻运动的有关信息。     

Removal of zirconium from spent fuel solution by alginate gel polymer

The uptake behaviour of zirconium (Zr) in alginate gel polymer and removal of Zr from spent fuel solution have been studied by the batch and column methods. As a first step, alginate gel polymer was synthesized and conditioned. The uptakes of Zr were examined in several concentrations of HNO₃ solution (from 0.01 M to 9 M HNO₃) by a batch method. Stronger affinity of Zr was shown than strontium (Sr), cobalt (Co), uranium (U) and iron (Fe) in 1 M HNO₃. It has been reported that cation binding was stronger with ions of higher charge in the alginate gel polymer. In contrast, the free aqueous ion, Zr⁴⁺, is the dominant form of the Zr species in very acidic solution. Therefore, the strong affinity of Zr is explained. The uptake rate of Zr was also evaluated in 2.6 M HNO₃ solution, which was close to the HNO₃ concentration in actual HLLW from fuel reprocessing. The uptake of Zr reached equilibrium within 2 h. For the column experiment, fission products (FPs) solution containing rare earth elements (REEs), platinum group metals, alkaline metals, alkaline earth metals and the other elements was prepared from actual spent fuel and the concentration of HNO₃ was adjusted to 2.6 M. In the column experiment, the alginate gel polymer was packed into a column, and then a chromatographic experiment was performed using the FPs solution prepared from actual spent fuel. As a result, over 95% of the Zr was removed from the FPs solution. Molybdenum (Mo), technetium (Tc), yttrium (Y), palladium (Pd), tellurium (Te), cesium (Cs) and REEs were eluted by the successive use of H₂O, and 1 M and 3 M HNO₃.     

辐射法合成超高分子量聚苯乙烯及其表征

采用60Coγ射线引发苯乙烯(Styrene,St)乳液聚合制备超高分子量聚苯乙烯(Ultra-high molecular weight polystyrene,UHMWPS).研究了不同反应条件对单体转化率和分子量的影响,并采用傅立叶变换红外光谱、核磁共振氢谱、差示扫描量热法和凝胶渗透色谱对其进行了表征.结果表明,当剂量率为0.6Gy·min-1时,得到聚合物的重均分子量为1.63×106,分子量分布指数为2.88,玻璃化转变温度为78.     

Mixing of Cr and Si atoms induced by noble gas ions irradiation of Cr/Si bilayers

Cr/Si bilayers were irradiated at room temperature with 120 keV Ar, 140 keV Kr and 350 keV Xe ions to fluences ranging from 10¹⁵ to 2 × 10¹⁶ ions/cm². The thickness of Cr layer evaporated on Si substrate was about 400 Å. Rutherford backscattering spectrometry (RBS) was used to investigate the atomic mixing induced at the Cr-Si interface as function of the incident ion mass and fluence. We observed that for the samples irradiated with Ar ions, RBS yields from both Cr layer and Si substrate are the same as before the irradiation. There is no mixing of Cr and Si atoms, even at the fluence of 2 × 10¹⁶ ions/cm². For the samples irradiated with Kr ions, a slight broadening of the Cr and Si interfacial edges was produced from the fluence of 5 × 10¹⁵ ions/cm². The broadening of the Cr and Si interfacial edges is more pronounced with Xe ions particularly to the fluence of 10¹⁶ ions/cm². The interface broadening was found to depend linearly on the ion fluence and suggests that the mixing is like a diffusion controlled process. The experimental mixing rates were determined and compared with values predicted by ballistic and thermal spike models. Our experimental data were well reproduced by the thermal spikes model.     

中能氮离子束辐照小麦种子产生自由基的研究

用ＥＳＲ波谱术研究了室温下中能氮离子辐照小麦种子产生的自由基，发现氮离子贯穿和注入小麦种子产生的自由基浓度随剂量的变化具有不同的特征。对氮离子贯穿小麦种子产生的自由基浓度随剂量率的变化规律也进行了研究。     

Degradation of polyimide induced by nitrogen laser irradiation

The degradation behavior of polyimide (PMDA-ODA) induced by nitrogen laser irradiation was studied. The changes in the surface morphology and the composition of the irradiated polyimide films were examined by scanning electron microscopy, X-ray photoelectron spectroscopy and FT-IR spectroscopy. The initial reaction was achieved by photochemical degradation of polyimide in the highly electronic excited state by the absorption of a second 337 nm photon. Atmospheric oxygen sequentially reacted with the produced radicals to form a highly oxidized layer. The formation of carbonyl group was enhanced by the heat remaining on the irradiated polyimide film surfaces.     

Effect of oxygen on gamma irradiation of polypropylenes studied by positron annihilation spectroscopy

The aim of this paper is to study the effect of oxygen on the microstructure of PP irradiated by gamma ray. The released gases from the sample in irradiation process were measured by gas chromatography. The results showed that the hydrogen release from the irradiated PP is independent on the irradiation atmosphere. It is only dependent on the irradiation dose that could be interpreted by a simple model. The microstructure of PP samples irradiated under different atmospheres is studied by positron annihilation spectroscopy. It is found that there are two sub-peaks in free volume distribution of PP irradiated under helium, while only one peak in the distribution of PP irradiated under air. It is the direct evidence to the argument that the new voids are formed in the irradiation process under inert gas and the oxygen may induce the voids to merge together. The influence of oxygen on the crystalline of PP irradiated by gamma is also discussed.     

Superabsorbentmaterials from grafting of acrylic acid onto Thai agricultural residues by gamma irradiation

Superabsorbent polymers based on ubiquitous agricultural residues: sugarcane, water hyacinth, rice straw, coconut shell and palm fruit bunch substrates, were successfully synthesized. Gamma radiation from Co-60 was employed to graft acrylic acid (AA) onto the substrates. Rice straw exhibited the highest equilibrium swelling ratio of 78.90 g/g at 6 kGy of absorbed gamma ray dose and 14%v/v AA concentration. The rate of water absorption was rapid at the beginning and became reduced with increasing immersion time. After about 3.5 hours, the absorption reached approximately 90% of the saturation value. Temperature plays a critical role on the rate of water evaporation from the superabsorbent. As for the one experiencing 35 °C–40 °C temperature, the weight of the saturated superabsorbent reduced to approximately 50% of the original value in 13 hours. However, for the one experiencing room temperature (24.2 °C–27.7 °C), approximately 58 hours were needed to reduce the weight by half. The superabsorbent polymer was able to absorb about 203% of the polymer's dry weight and did not release urea when eluded by water. Moreover, the polymer was able to hold water very well for at least 3 weeks and did not degrade until at least 6 weeks, ensuring biodegradability.