Neutron detection by measuring capture gammas in a calorimetric approach

The neutron capture detector (NCD) is introduced as a novel detection scheme for thermal and epithermal neutrons that could provide large-area neutron counters by using common detector materials and proven technologies. The NCD is based on the fact that neutron captures are usually followed by prompt gamma cascades, where the sum energy of the gammas equals to the total excitation energy of typically 6-9 MeV. This large sum energy is measured in a calorimetric approach and taken as the signature of a neutron capture event. An NCD consists of a neutron converter, comprising of constituents with large elemental neutron capture cross-section like cadmium or gadolinium, which is embedded in common scintillator material. The scintillator must be large and dense enough to absorb with reasonable probability a portion of the sum energy that exceeds the energy of gammas emitted by common (natural, medical, industrial) radiation sources. An energy window, advantageously complemented with a multiplicity filter, then discriminates neutron capture signals against background. The paper presents experimental results obtained at the cold-neutron beam of the BER II research reactor, Helmholtz-Zentrum Berlin, and at other neutron sources with a prototype NCD, consisting of four BGO crystals with embedded cadmium sheets, and with a benchmark configuration consisting of two separate NaI(Tl) detectors. The detector responses are in excellent agreement with predictions of a simulation model developed for optimizing NCD configurations. NCDs could be deployed as neutron detectors in radiation portal monitors (RPMs). Advanced modular scintillation detector systems could even combine neutron and gamma sensitivity with excellent background suppression at minimum overall expense.     

Preparation and Properties of Smart Thermal Control and Radiation Protection Materials for Multi-functional Structure of Small Spacecraft

Considering the unique properties of small spacecraft,such as light weight,low power-consumption and high heat flux density,a new kind of lightweight boron carbide(B 4 C) radiation-protection coating material was proposed.New techniques for preparing LSMO thermal control coating and B 4 C radiation-protection coating were developed.The sample piece of multi-functional structure was manufactured by using the proposed materials,and a series of performance tests,such as thermal control and radiation-protection behaviors were evaluated.Test results show that:the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K.The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material.The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.     

乙醇-水-l,3-二甲基咪唑磷酸二甲酯盐三组分物系的汽液平衡测定及关联

在101.32 kPa下,用CE-2型Othmer汽液平衡釜测定了乙醇-水-1,3-二甲基咪唑磷酸二甲酯盐([mmim]DMP)物系的等压汽液平衡数据;采用UNIFAC方程对实验数据进行了关联。实验结果表明,UNIFAC方程可用于含离子液体物系的汽液平衡的计算;加入离子液体[mmim]DMP使乙醇-水二组分物系的汽液平衡线发生偏离,[mmim]DMP含量越高,汽液平衡线偏离程度越大;[mmim]DMP具有明显的盐析效应,能消除乙醇-水二组分物系的共沸点;[mmim]DMP可作为乙醇-水物系萃取精馏的溶剂。     

原料中非芳烃的分析及其对甲苯歧化与芳烃烷基转移反应的影响

采用气相色谱-质谱联用和气相色谱相结合的方法对中国石化上海石油化工股份有限公司甲苯歧化单元原料中的非芳烃进行了定性、定量分析;并考察了原料中的非芳烃对甲苯歧化与芳烃烷基转移反应的影响。定性分析结果表明,该原料中的非芳烃组分非常复杂,包括C_(3～5)的低碳烷烃、以五元环和六元环为主的C_(7～10)环烷烃以及少量的C_(10)和C_(11)链烷烃;定量分析结果表明,非芳烃的质量分数(相对于原料)达到2.90%。甲苯歧化与芳烃烷基转移反应实验结果表明,在反应温度400℃、液态空速2.5 h-、氢烃摩尔比3.0、反应压力3.0 MPa、反应时间72 h的条件下,该原料的转化率明显低于常规原料,要维持相同转化率,反应温度大约需提高20℃;该原料因含有较多的重质非芳烃,在较大程度上影响了催化剂的使用寿命。     

Polarity determination by electron energy-loss spectroscopy: application to ultra-small III-nitride semiconductor nanocolumns

Channeling-enhanced electron energy-loss spectroscopy is applied to determine the polarity of ultra-small nitride semiconductor nanocolumns in transmission electron microscopy. The technique demonstrates some practical advantages in the nanostructure analysis, especially for feature sizes of less than 50 nm. We have studied GaN and (Al, Ga)N nanocolumns grown in a self-assembled way by molecular beam epitaxy directly on bare Si(111) substrates and on AlN buffer layers, respectively. The GaN nanocolumns on Si show an N polarity, while the (Al, Ga)N nanocolumns on an AlN buffer exhibit a Ga polarity. The different polarities of nanocolumns grown in a similar procedure are interpreted in terms of the specific interface bonding configurations. Our investigation contributes to the understanding of polarity control in III-nitride nanocolumn growth.     

阻燃剂微胶囊制备及在聚合物中的应用研究进展

聚合物常用阻燃剂,如卤素阻燃剂、磷类阻燃剂、磷氮类阻燃剂、金属氢氧化物阻燃剂等通常都存在一些缺陷或不足,因此需要对阻燃剂进行一些表面改性。微胶囊化是一种常用的表面改性方法。阻燃剂经过微胶囊化改性之后,可以改善其稳定性、阻燃性、分散性、与树脂基体之间的相容性等。文中主要介绍采用聚合物为囊材的不同类型阻燃剂微胶囊化的制备技...     

羰基铁粉表面改性及其热稳定性研究

采用硅烷偶联剂对羰基铁颗粒进行表面改性,研究改性羰基铁粉的热稳定性,利用扫描电镜、红外光谱、差热分析等分析手段,对羰基铁粉表面改性效果和机理进行系统分析。结果表明:经过硅烷偶联剂改性之后的羰基铁粉红外图谱出现了Si—O—Si和Si—O—Fe的特征峰,说明硅烷偶联剂与羰基铁颗粒表面发生化学键合作用;改性后的羰基铁粉与未改性羰基铁粉相比,其分散性和抗氧化能力得到了明显提高。     

沼气发电机组的开发利用

沼气机组发电符合当今发展循环经济,节约能源的时代要求,也会对缓解国内区域性能源紧张发挥重要作用.本文介绍了当前我国沼气生产、利用的现状,阐明了沼气的组成及其燃烧特性,论述了沼气发电机组的结构原理及其创新技术.     

Ni/YSZ and Ni–CeO2/YSZ anodes prepared by impregnation for solid oxide fuel cells

In this paper, Ni/YSZ and Ni–CeO₂/YSZ anodes for a solid oxide fuel cell (SOFC) were prepared by tape casting and vacuum impregnation. By this method, the Ni content in the anode could be reduced compared to the traditional tape casting method. It was found that adding CeO₂ into the Ni/YSZ anode by a Ni(NO₃)₂ and Ce(NO₃)₃ mixed impregnation could further enhance cell performance. This was investigated in H₂ at 1073 K. XRD patterns indicated that CeO₂ and Ni were separate phases, and the CeO₂ addition could enhance the Ni dispersion on the YSZ framework surface which was observed by SEM images. It was shown that adding CeO₂ into the Ni anodes could decrease the cell polarization resistance. The maximum power density for cells with 25 wt.% Ni, 5 wt.% CeO₂–25 wt.% Ni/YSZ, or 10 wt.% CeO₂–25 wt.% Ni/YSZ anode was 230 mW cm⁻², 420 mW cm⁻² and 530 mW cm⁻², respectively, in H₂ at 1073 K. The OCV for these cells was 1.05–1.09 V, indicating that a dense electrolyte film was obtained by co-firing porous YSZ layer and dense YSZ layer.