纳米孔径重离子微孔膜的制备

应用中国原子能科学研究院HI 13串列加速器产生的重离子32S和79Br轰击聚对苯二甲酸乙二醇酯（PET）薄膜,再对薄膜进行化学蚀刻处理使由重离子辐照损伤产生的潜径迹形成微孔,制备出孔径为100～900nm的重离子微孔膜。为增加径迹蚀刻速率与体蚀刻速率之比,化学蚀刻前采用紫外光辐照薄膜。蚀刻过程中采用电导蚀刻法监测膜孔径生长过程。对32S和79Br辐照制备的重离子微孔膜进行了比较,79Br离子辐照制备的微孔膜与32S离子辐照制备的微孔膜相比,孔型圆整,锥角更小;在制备纳米微孔膜方面79Br离子优于32S离子。     

PET薄膜中32S离子径迹的热退火效应

采用径迹蚀刻的方法研究了热处理对聚对苯二甲酸乙二醇酯（PET）薄膜中重离子径迹的热退火效应。使用113.7 MeV的³²S离子在PET薄膜中产生垂直于表面且贯穿薄膜的离子径迹。对薄膜进行局部热处理，加热温度为70～240 ℃，时间为1～300 s。薄膜经过化学蚀刻成核孔膜后使用显微镜观测。结果表明：在相同的热处理时间下，随着热处理温度的升高，PET薄膜中离子径迹的热退火效应愈加明显；在热处理温度不变的情况下，随着热处理时间的增加，退火效应亦愈加明显。     

利用中国实验快堆生产放射性同位素的可行性研究

中国实验快堆（CEFR）不仅能进行各种燃料、材料辐照实验,也是放射性同位素生产的优良平台。本文对CEFR的辐照性能进行了描述,并利用计算程序对适宜在CEFR上生产的同位素³²P、³³P、³⁵S、⁸⁹Sr、¹⁴C、⁶⁰Co进行理论计算,得到了产量和比活度等参数。计算结果表明,在CEFR堆芯辐照可得到纯度极高的³²P、³³P、³⁵S,利用快中子的（n,p）反应可得到无载体的⁸⁹Sr,在CEFR反射层布置慢化材料可得到比活度较高的¹⁴C、⁶⁰Co。以上结果表明,在CEFR上生产同位素是可行的。     

高温He离子辐照引起的Hastelloy N合金微结构变化研究

本文采用30 keV的He离子辐照Hastelloy N合金,辐照温度为500C,剂量分别为:1×10¹⁵、×10¹⁵、1×10¹⁶He⁺/cm²。利用扫描电子显微镜（SEM）研究了辐照后块体样品的表面形貌。结果表明,辐照后的块体样品均观察到了表面起泡现象。利用透射电子显微镜（TEM）研究了辐照后TEM样品微结构的变化。结果表明,低剂量(1×10¹⁵ He⁺/cm²)辐照的样品中出现了黑斑缺陷;随着辐照剂量的增加,开始出现位错环及纳米级的氦泡,同时黑斑密度减少;当剂量增至1×10¹⁶He⁺/cm²,位错环以及氦泡的尺寸和密度明显增大,晶界处氦泡更加密集。     

绝缘材料抗金属污染性能

使用HI-13串列加速器产生的32S离子对不同厚度的聚酯膜进行不同密度的辐照,并在不同温度、不同碱度和不同蚀刻时间条件下,针对蚀刻对孔形状、孔径以及膜表面损耗的影响等进行了研究.在蚀刻后的样品表面镀金属膜,对镀膜后样品的抗金属污染的绝缘性能进行了研究.结果显示,核孔的存在使材料抗金属污染的绝缘性能得到了大幅提高.     

PET核孔膜蚀刻速率影响因素的研究

核孔膜是通过重离子照射薄膜后进行化学蚀刻所得到的高性能过滤材料,蚀刻速率是影响高质量核孔膜制备的重要因素。本文探讨了不同蚀刻液浓度、温度以及重离子辐照能量对蚀刻速率的影响。利用140 MeV的32S离子在室温和真空条件下对4层堆叠的PET(polyethylene terephthalate)薄膜进行了辐照。在对辐照样品进行化学蚀刻期间采用电导法确定了径迹蚀刻速率Vt。结果表明:蚀刻速率与蚀刻温度呈指数相关,随蚀刻液浓度增加而线性增大;径迹蚀刻速率随能量损失率(离子能损)增大。研究确定,在入射32S能量为1.6 MeV·u-1时,NaOH浓度为1mol·L-1、蚀刻温度为85°C时最有利于形成圆柱形微孔。     

3 MV加速器质谱测量36Cl

在端电压为3 MV的AMS装置上实现³⁶Cl及其他中重核素的高灵敏测量是AMS技术发展的重要方向之一。为进一步提高充气飞行时间探测方法中³⁶S的压低能力,本文研究了³⁶S和³⁶Cl在P10、异丁烷和丙烷气体中的能量歧离和角度歧离。在32 MeV的入射能量下测量了几个地下水样品中³⁶Cl的[JP2]含量,测量结果与72 MeV能量下的测量结果相符。测量结果表明,采用充气飞行时间探测方法在3 MV的串列加速器上测量³⁶Cl时,探测限为³⁶Cl/Cl≈10^-14,当样品中³⁶Cl/Cl≈10^-13时测量不确定度为30%。     

电导法研究紫外光预辐照对核孔膜径迹蚀刻的影响

利用紫外光辐照聚碳酸酯（PC）离子径迹膜,研究光辐照对于核孔膜蚀刻过程的影响。实验结果显示,紫外光照射对核孔膜的蚀刻有着重要的作用,它可以有效地增加径迹的蚀刻速率,并且径迹蚀刻速率随紫外光照时间的增加呈线性增长关系,此现象是由于光降解作用引起的。本文还介绍了用于监测核孔膜蚀刻过程的电导测量方法,利用此方法可以得出核孔膜径迹蚀刻速率、孔径随蚀刻时间变化等关系。     

固体核径迹对绝缘材料抗反射性能的影响

用HI-13串列加速器提供的³²S离子对聚碳酸酯和CR-39进行了不同密度的辐照，经紫外灯敏化和氢氧化钠蚀刻，样品表面的潜径迹形成具有一定孔径和深度的纳米和微米孔。利用真空蒸发在样品表面镀上金属银和光学材料氟化镁，在可见光波段测量样品镀膜前后的反射率、透过率等光学参数。测量结果表明，固体核径迹技术和镀膜技术可使材料的反射率降低至未处理前的1%以下。     

溶解硫酸盐硫同位素测试预处理方法优化

为分析水体中硫酸盐硫同位素组成,常将SO^2-₄转化为固体BaSO₄,进行预处理,但是该方法对体积少且低浓度硫酸盐样品（0～20 mg·L^-1）存在耗时长、回收率低等问题,对硫同位素测试结果的影响仍不明确。本文通过对不同Ba²⁺添加量、反应温度、pH和沉淀时间等条件对SO^2-₄回收率及δ³⁴S BaSO₄测试影响进行研究,优化由SO^2-₄转化BaSO₄的方法,并选取四种不同类型水体（雨水、湖水、污水、海水）进行验证。结果表明：1） SO^2-₄的回收率受沉淀生成速率和反应时间控制,在相同反应时间内,沉淀生成速率与过饱和度比、温度成正比,与H⁺浓度成反比,并且搅拌可以加速BaSO₄晶体的生长;2） 改进的预处理流程为：在水样中添加适量盐酸和氯化钡（pH=2.6,过饱和度比≥55）,用玻璃棒匀速搅拌1 min,90 ℃水浴加热1 h,冷却至室温后用滤膜收集BaSO₄;3） 优化后的预处理方法测试天然样品时,SO^2-₄可以在1 h内完全转化为BaSO₄固体,并且不发生硫同位素分馏,低SO^2-₄浓度（3.24 mg·L^-1）的雨水样品,其转化率从0提高至98.7%,δ³⁴S约为15.7‰±0.1‰;中等SO^2-₄浓度（30.34 mg·L^-1）的湖水样品,其转化率从26%提高至100%,δ³⁴S为5.8‰±0.2‰;高SO^2-₄浓度（140.4～2 516.4 mg·L^-1）的污水和海水样品,硫酸盐的回收率和δ³⁴S与传统方法得到的结果相近。改进的预处理方法有效提高了低浓度水溶硫酸盐样品的回收率,避免转化过程中的同位素分馏。该方法对于中高浓度的样品同样适用。     

Initial stage of etching through pores in PET films irradiated by Ar ions

Changes in the diameters and depths of pores were studied in the process of etching polyethyleneterephthalate (PET) films irradiated by Ar ions having an energy of 1 MeV/n. Information about the pore diameters and lengths was obtained with JSM-840 and TEM-125 electron microscopes. The solutions of NaOH (0.5 mol/dm³ and 2 mol/dm³) were used as etchants. Etching was performed at 55 °C and 70 °C. Two methods of sensitization were used: the first one by UV illumination and treatment in dimethylformamide (DMF), the second method just by UV illumination. It was found that the diameters and the depths of pores are larger in films treated according to the first sensitization method. Etching duration (breakthrough time), which leads to through-going pores of the minimal radius, was established. After sensitization according to the first method the track etch rate grows quicker than the transverse etch rate. This gives a possibility to obtain through pores with diameters ranging from 50 nm to several micrometers.     

Investigation of initial stage of chemical etching of ion tracks in polycarbonate

Chemical track etching and the growth of nanochannels in ion-irradiated polycarbonate foils were investigated by loss of weight measurements and IR-spectroscopy. The data provided by both methods are in good agreement and allow us to shed light on the early stage of pore formation including times where the breakthrough of the pores has not yet occurred. Clear evidence is shown that the pore growth as a function of etching time depends on the irradiation fluence. For fixed etching parameters, foils containing 7 × 10⁹ tracks/cm² exhibit much smaller pores than samples with 2 × 10⁸ tracks/cm². This effect is independent of the etching temperature and appears for irradiations with Pb ions as well as for Ca-ion tracks sensitized by UV exposure. Model calculations for different etching times and fluences show that the data for low track densities can be fitted quite well by describing the radial etching rate by the track etch rate changing into the bulk etch rate with a Gaussian-shaped transition.     

Neutron Dosimetry with Boron-Doped CR-39 Plastic

As a highly sensitive, simple and non-radioactive neutron dosimeter, CR-39 plastic plates doped with a boron compound: ortho-carborane were prepared. After thermal neutron irradiation, the plates were etched in an aqueous solution of 30%KOH, at 60°C for 2 to 16 h. The etch-pits generated by ¹⁰B(n, α)⁷Li reactions were then counted using an optical microscope or an automatic track counting system. The density of the etch-pits on an irradiated plate increases with the etching time. When the etching time is kept constant, the etch-pit density is proportional to the irradiated thermal neutron fluence. The proportional constant is termed “sensitivity”, which is 4.2 x 10^?4 for a plate containing ortho-carborane at a concentration of 0.5% by weight and for etching time of 16 h. By considering background counts, a thermal neutron dose of 0.025 mSv can be measured with this plate. The plates are insensitive to visible-, UV-, X-, β- and γ-rays and are easy to handle because the detector and converter are incorporated. There is no possibility of underestimating the dose equivalent due to fading. Furthermore, the isotopes of boron are not radioactive and thus are radio- logically safe.     

Measurement of (n, n′) reaction cross-sections of 79Br, 90Zr, 197Au and 207Pb with pulsed d-D neutrons

Activation cross-sections for the (n, n′) reaction were measured by means of the activation method at neutron energies of 3.1 and 2.54 MeV using a pulsed neutron beam. The target nuclei were ⁷⁹Br, ⁹⁰Zr, ¹⁹⁷Au, and ²⁰⁷Pb whose half-lives were between 0.8 and 8 s. The value of the ⁹⁰Zr(n, n′) ^90mZr reaction was obtained for the first time. In order to confirm the pulsed neutron beam measuring method, the cross-section data of ⁷⁹Br and ¹⁹⁷Au were compared with previous data obtained using a pneumatic sample transport system. The results of this comparison were in agreement within the range of experimental error. The d-D neutrons were generated by bombarding a deuterated titanium target with a 350-keV d⁺-beam at the 80° beam line of the Fusion Neutronics Source (FNS) at the Japan Atomic Energy Research Institute. In order to obtain reliable activation cross-sections, careful attention was paid to correct the efficiency for a volume source, and the self-absorption of gamma rays in irradiated samples. The systematics of the (n, n′) reaction at a neutron energy of 3.0 MeV, which can predict cross-section of (n, n′) reaction with an accuracy of 50%, was proposed for the first time on the basis of our data.     

Neutron irradiation studies on low density pan fiber based carbon/carbon composites

Carbon has been extensively used in nuclear reactors and there has been growing interest to develop carbon-based materials for high-temperature nuclear and fusion reactors. Carbon-carbon composite materials as against conventional graphite material are now being looked into as the promising materials for the high temperature reactor due their ability to have high thermal conductivity and high thermal resistance. Research on the development of such materials and their irradiation stability studies are scant. In the present investigations carbon-carbon composite has been developed using polyacrylonitrile (PAN) fiber. Two samples denoted as Sample-1 and Sample-2 have been prepared by impregnation using phenolic resin at pressure of 30 bar for time duration 10 h and 20 h respectively, and they have been irradiated by neutrons. The samples were irradiated in a flux of 10¹² n/cm²/s at temperature of 40 °C. The fluence was 2.52 × 10¹⁶ n/cm². These samples have been characterized by XRD and Raman spectroscopy before and after neutron irradiation. DSC studies have also been carried out to quantify the stored energy release behavior due to irradiation. The XRD analysis of the irradiated and unirradiated samples indicates that the irradiated samples show the tendency to get ordered structure, which was inferred from the Raman spectroscopy. The stored energy with respect to the fluence level was obtained from the DSC. The stored energy from these carbon composites is very less compared to irradiated graphite under ambient conditions.     

Optimization of nanopores obtained by chemical etching on swift-ion irradiated lithium niobate

The morphology of the nanopores obtained by chemical etching on ion-beam irradiated LiNbO₃ has been investigated for a variety of ions (F, Br, Kr, Cu, Pb), energies (up to 2300 MeV), and stopping powers (up to 35 keV/nm) in the electronic energy loss regime. The role of etching time and etching agent on the pore morphology, diameter, depth, and shape has also been studied. The transversal and depth profiles of the pore have been found to be quite sensitive to both irradiation and etching parameters. Moreover, two etching regimes with different morphologies and etching rates have been identified.     

Study on Transmission of Near-infrared Light Through Polyester Films Modified by Nuclear Pores

Polyester membranes were irradiated by energetic ^32S ion beams from the HI-13 tandem accelerator, and then etched by NaOH solutions with different concentration, temperature, and etching time. These nuclear pore-modified membranes were studied on pore size, pore shape, and the transmission properties for near infrared light. Preliminary results show that the membranes produced with optimized pore density and etching conditions have higher transmission rate.     

Evaluation of aged Incoloy 800 alloy sensitization to intergranular corrosion by means of double loop electrochemical methods and image analysis

In this paper, the sensitization of aged Incoloy 800 alloy to intergranular corrosion has been systemically investigated by double loop electrochemical potentiokinetic reactivation (DL-EPR) technique in combination with oxalic acid etching test and microstructure observation. The DL-EPR results show that the specimens aged at 650 °C and 700 °C for 4 h were intensely sensitized with I_r:I_a value greater than 30% while there was no sensitization phenomenon for the specimens aged at 800 °C for 4 h. It was also found that the degree of sensitization increased gradually with the aging time in the range of 0-10 h at 650 °C, and I_r:I_a value reached the maximum −46% after an aging time of 10 h. However, further increasing aging time decreased the sensitization due to the healing effect incurred by the diffusion of chromium from adjacent grains to chromium-depleted zones. Comparison between two evaluating techniques (the DL-EPR and oxalic acid etching test) has also been conducted.     

Effect of annealing in thermostimulated luminescence (TSL) on natural blue colour calcite crystals

The thermostimulated luminescence (TSL) glow curve characteristics of 10 blue coloured calcite crystals of Southern Tamilnadu are analysed. The natural thermoluminescence (NTL) measurements were carried out for all the samples and annealed in air at the temperatures ranging from 200 to 700 °C, at an interval of 50 °C, for 1 h duration. The glow curves of annealed and unannealed samples irradiated with a gamma dose of 500 Gy show three peaks at 145, 255 and 345 °C, respectively, when recorded with a linear heating rate of 10 °C/s. Annealing treatment above 400 °C increases the sensitivity of all TSL peaks except 345 °C. On the other hand, annealing at 700 °C caused a collapse in the TSL sensitivity. The enhancement in TSL sensitivity was found to depend on the annealing temperature and time. Annealing treatment at 600 °C for 5 h followed by quenching in air is the optimum conditions for TSL sensitization. The response to gamma irradiation is linear in the range from 1 to 10⁴ Gy. The emission spectra of all the samples show an emission at around 610 nm but with different intensities for each sample. With reference to earlier work, it may be assumed that the recombination site always involves Mn²⁺ ions.