多组元烧绿石陶瓷固化体的制备及其抗浸出性能

烧绿石具有优异的理化稳定性和耐辐照稳定性,被认为是理想的放射性核素固化基材。然而,人造烧绿石在烧结过程中对核素的选择性高,从而限制了其固化核素的种类和数量。针对上述问题,本工作以镧系元素铕（Eu）、钐（Sm）、钕（Nd）模拟放射性的锕系核素,成功制备得到了2、3、4组元的烧绿石结构陶瓷固化体。结果表明,目标核素均匀地固溶在烧绿石的晶格结构中形成了单相均一的多组元烧绿石陶瓷固化体。化学浸出实验表明,多组元烧绿石结构具有优异的抗浸出性能,是一种具有应用前景的高放废物陶瓷固化体候选材料。     

DGA树脂辅助的循环淋洗技术制备无载体镥［177Lu］

为实现核医学广泛关注的新型医用放射性同位素¹⁷⁷Lu的国产规模化,利用中国绵阳反应堆（CMRR）进行无载体（n.c.a.）¹⁷⁷Lu的制备工艺研究。在常规的镧系树脂分离纯化¹⁷⁷Lu的流程中加入可以吸附洗脱液中金属离子的DGA树脂柱,并通过特殊的流路连接方式,实现淋洗镧系树脂柱洗脱液的“在线”循环。示踪实验和三次生产流程验证表明,第一级分离的废液量降低>86%。质检分析表明,循环淋洗技术制备的无载体¹⁷⁷Lu产品符合质量要求。研究表明,该技术显著降低了镧系树脂分离无载体¹⁷⁷Lu中的放射性酸废液总量,可用于规模化生产工艺。     

Electrodeposition of composite films consisting of polypyrrole and mesoporous silica

Electrochemical formation of composite films consisting of polypyrrole (PPy) and MCM particles has been presented, in which pyrrole is electrochemically oxidized in an aqueous solution with suspension of purely siliceous or aluminum-containing MCM-41. The composite films were characterized by scanning electron microscopy, X-ray diffraction and infrared reflection spectroscopy, and the electrochemical response of the PPy/MCM-deposited electrode to Fe(CN)₆³⁻ investigated. From IR spectra, it is indicated that the polymerization of pyrrole takes place on the internal wall of MCM particles where the cationic PPy is charge-balanced by the negatively charged MCM. A PPy/SiMCM composite electrode prepared in the presence of higher concentration of pyrrole (≧0.5 M) shows a reproducible electrochemical response for Fe(CN)₆³⁻. The CV curve on this electrode is comparable to that on pure PPy-modified electrode, and it is suggested that the negative charge on the mesopore surface is almost completely neutralized by the positive charge of PPy.     

Development of a variable temperature mechanical loading device for in situ neutron scattering measurements

Understanding the phase transformation and failure mechanism of NiTi shape memory alloys under variable environments of high and low temperatures is critical to the establishment of constitutive properties and to the realization of controllable design. Information regarding the correlation between the phase transformation and deformation can be obtained by in situ neutron scattering measurements. Therefore, a variable temperature mechanical loading device is designed, which can be used for mechanical loading and in situ neutron scattering measurements in a variable temperature environment. Specifically, the device can achieve precise temperature control with a temperature change from −55 °C to 200 °C in a protective atmosphere. The rated load in the axial direction is 6 kN, and the maximum displacement of the unilateral grip is larger than 30 mm. In situ neutron scattering measurements can be performed through neutron windows, and the strain can be measured by digital image correlation technology. Moreover, the force sensor is calibrated to improve test precision. Through an evaluation of temperature uncertainty, the temperature measurement performance is estimated. Tensile tests of the NiTi alloy at variable temperatures are carried out, and preliminary results are given. The four deformation stages of the NiTi alloy can be seen from the stressstrain curve, which corresponds to the existing results. This demonstrates that the designed variable temperature mechanical loading device can supply the testing demands. The device provides a new way to study the relationship between the phase transformation and mechanical properties of NiTi shape memory alloys at variable temperatures.

     

Catalytic activity of oxides and halides on hydrogen storage of MgH2

Hydrogen sorption kinetics of ball milled MgH₂ with and without chemical additives were studied. We observed kinetics and capacity improvement with increasing the number of sorption cycles that contributed to the micro/nano cracking of MgH₂ particles, shown by XRD and SEM studies. In addition, to investigate the proposed specific role of O²⁻-based additives on the sorption kinetics of MgH₂, we have undertaken a comparative study evaluating the performances of MgH₂ containing the NbCl₅, CaF₂ or Nb₂O₅ additives. At 300 °C, addition of NbCl₅ and CaF₂ improved the sorption capacity to 5.2 and 5.6 wt% within 50 min, respectively, in comparison to the required 80 min in the case of Nb₂O₅. This suggests the importance of the chemical nature of the catalyst for hydrogen sorption in MgH₂. In addition, the catalyst specific surface area was shown to be very critical. High surface area Nb₂O₅ (200 m² g⁻¹), prepared by novel precipitation method, exhibits an excellent catalytic activity and helped to desorb 4.5 wt% of hydrogen from MgH₂ within 80 min at a temperature as low as 200 °C.     

薄膜型90Sr放射源制备工艺研究

目的为了获取与~(90)Sr同位素电池匹配的放射源,研发一种在指定非金属衬底材料上制作薄膜型~(90)Sr放射源的工艺。方法双环己烷-18-冠醚-6是一种既可配位锶离子,又具有良好抗辐照性能的分子,采用配位法将硝酸锶负载在该冠醚分子上,并溶解于高分子成膜剂中,在衬底材料上滴加后,自然晾干制备成含锶膜层。对制备结果进行了IR、TG、DSC、EDS、元素分析表征,考察了膜与衬底材料之间在经过116 k Gy剂量的γ辐照前后的结合力。结果该工艺实现了锶加载率大于93%,辐照后薄膜振荡掉粉率的增加小于1.3%。示踪实验表明,薄膜中表征锶分布不均匀性的相对标准偏差在7%左右。结论该工艺能够在衬底材料上获取~(90)Sr放射性薄膜,膜与衬底之间结合牢固,锶分布均匀性满足相关行业标准。     

Node trust evaluation in mobile ad hoc networks based on multi-dimensional fuzzy and Markov SCGM(1, 1) model

Due to the nature of distribution and self-organization, mobile ad hoc networks rely on cooperation between nodes to transfer information. One of the key factors to ensure high communication quality is an efficient assessment scheme for risks and trust of choosing next potential cooperative nodes. Trust model, an abstract psychological cognitive process, is one of the most complex concepts in social relationships, involving factors such as assumptions, expectations and behaviors. All of the above make it difficult to quantify and forecast trust accurately. In this paper, based on the theories of fuzzy recognition with feedback, SCGM(1, 1) model and Markov chain, we present a pattern of prediction making. The analysis and experimental computation show that this scheme is efficient in trust prediction for ad hoc networks.     

基于BIXS方法的气体中高浓度氚在线测量技术

工艺气体中高浓度氚的在线测量要求探测器具有体积小、密封性好、稳定性高等特点。针对该需求,本工作基于氚β射线诱发X射线谱测量方法（BIXS）建立了高浓度氚在线测量实验系统,采用PENELOPE程序建立了理论计算模型,对系统中5个关键参数进行了设计优化,搭建了1.77 mL小体积BIXS实验系统,使用含氚的氢氩混合气体对实验系统进行了响应能谱测量,并对获得的BIXS能谱谱形进行了初步分析。实验结果表明,对于含氚的氢氩混合气体,BIXS系统重复测量结果显示全谱计数率偏差＜0.8%,Ar的K_α峰计数率偏差＜1.3%,Au的M_α峰偏差＜3.8%,整体稳定性较好;不同压强下BIXS实验系统测量结果显示,BIXS能谱总计数率、Ar的K_α峰强度以及轫致辐射谱强度随压强增加呈线性上升趋势,但Au的M_α峰强度在该气氛下几乎不随氚的分压改变。     

TiC陶瓷中H原子扩散行为第一性原理计算研究

采用第一性原理计算方法研究了H原子在立方TiC 晶格中的结构稳定性及扩散行为。结果表明：H原子在TiC晶格中的最稳定位点位于Ti/C六面体中靠近C原子的C-H（C-HS）位置,H被C原子捕获而形成C—H键,键长1.15 Å（1 Å=0.1 nm）,零点修正（ZPE）后形成能为1.58 eV;其次是Ti/C六面体中心位置（CS）,H 原子主要与Ti原子成键,ZPE修正后的形成能为1.75 eV。采用CI-NEB方法计算预测了TiC晶格中H间隙原子的最优扩散路径,即先在Ti/C六面体内沿(110)晶面进行“跳跃”扩散,扩散势垒为0.47 eV;然后以C原子为中心,沿(100)晶面进行两次“旋转”扩散穿越Ti/C原子面,扩散势垒为0.28 eV。     

低温循环色谱法分离H_2/HD

低温循环色谱法(CCC)是一种有效的氢同位素分离方式。在升级改造后的低温色谱分离装置上开展了H2/HD体系的分离研究。结果表明:原始氘丰度为1.4×10-4的高纯氢经过CCC 4个流程后,氘丰度达到1.173×10-3;为获得最佳色谱柱柱效,CCC的进样量控制在组分峰的容量因子下降10%时较为合适;CCC的双柱间可互相充当解吸柱与接收柱的角色,在柱结构与程序升温条件相同的前提下,双柱间分离效果的差异可能是进样点的选择和进样压力的不同造成的,与进样时间无关。