铀-钍混合燃料反应堆的可行性分析

分析了以铀为燃料的核电系统的弊端、钍燃料反应堆的理论技术依据和世界范围内钍燃料反应堆的研究状况。提出在我国开发利用钍资源,建立铀．钍混合燃料反应堆具有的独特优势,建议应加大钍资源开发人力物力投入,改变我国核电利用水平落后和钍资源流失之现状。Nuclear energy is a preferred option for electric power generation. The disadvantages of the current uranium-dioxide （UO2 ） fuel in nuclear power were presented and the reactor using the mixed thorium dioxide and uranium dioxide fuel （ ThO2-UO2 ） in the near future was foretold. A proposal to strengthen the research cooperation on the use of the thorium mineral resources in china was put forward.     

Electronic Structure Analysis of USiO4

Uranium is a member of Actinides and plays important role in nuclear science and technology. Electronic and structural investigations of actinide compounds attract major interest in science. The electronic structure and chemical bonding of coffinite USiO4 are investigated by X-ray Absorption Fine Structure spectroscopy （XAFS）. U L3- edge absorption spectrum in USiO4 is compared with U L3-edge spectra in UO2 and UTe due to their different electronic and chemical structures. The study presents XANES （x-ray Absorption Near-Edge Structure） and Extended XAFS （EXAFS） calculations of USiO4 thin films. The full multiple scattering approach has been applied to the calculation of U L3 edge XANES spectra of USiO4, UO2 and UTe, based on different choices of one electron potentials according to Uranium coordinations by using the real space multiple scattering method FEFF 8.2 code.     

电子束辐照改性铀吸附材料中官能团的性能研究

探讨了带有肟胺基官能团材料的制备、 吸附铀的机理及其对盐湖卤水中铀的吸附效果。 利用电子束辐照法制备肟胺化无纺布, 红外光谱显示材料中含有肟胺基存在, 表明肟胺基成功的接枝在无纺布基体上。 研究了铀溶液的初始pH、 吸附时间和固液比等因素对铀吸附效果的影响, 吸附过程中络合反应为控速步骤。 肟胺化纤维和肟胺化无纺布对盐湖卤水样品具有较高的吸附效率, 可以作为盐湖提铀的备选材料。 Amidoximed fiber and fabric were synthesized with the purpose of adsorbing U in salt lake and the adsorption mechanism was discussed. IR indicated that amidoxime was graft to the fabric which was irradiated by electron beam. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time on uranium sorption efficiency. The sorption of uranium on amidoxime was dependent on the pH value of the solution, and the optimal pH was 4.0. Uranyl was taken out from solution in the form of complex with amidoxime. Uranium recovery efficiency from salt lake was more than 50% with amidoximed fiber and fabric which can be used as uranium extraction material.     

Direct observation of the f–c hybridization in the ordered uranium films on W(110)

A key issue in metallic uranium and its related actinide compounds is the character of the f electrons, whether it is localized or itinerant.Here we grew well ordered uranium films on a W(110) substrate.The surface topography was investigated by scanning tunneling microscopy.The Fermi surface and band structure of the grown films were studied by angle-resolved photoemission spectroscopy.Large spectral weight can be observed around the Fermi level, which mainly comes from the f states.Additionally, we provided direct evidence that the f bands hybridize with the conduction bands in the uranium ordered films, which is different from previously reported mechanism of the direct f–f interaction.We propose that the above two mechanisms both exist in this system by manifesting themselves in different momentum spaces.Our results give a comprehensive study of the ordered uranium films and may throw new light on the study of the 5 f-electron character and physical properties of metallic uranium and other related actinide materials.     

Photoluminescence of amorphous carbon films fabricated by layer—by—layer hydrogen plasma chemical annealing method

A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layer method) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemical vapour deposition system.It was found that the hydrogen plasma treatment could decrease the hydrogen concentration in the films and change the sp^2/sp^3 ratio to some extent by chemical etching.Blue photoluminescence was observed at room temperature,as a result of the reduction of sp^2 clusters in the films.     

紫外脉冲荧光法测定微量铀的研究

紫外脉冲荧光法是一种通过液体激光来直接测定微量铀的方法。在采用紫外脉冲荧光法分析面包酵母吸附放射性核素铀后溶液剩余铀浓度之前,研究了荧光增强剂、pH 值、以及温度对微量铀浓度工作曲线的影响。结果表明:当pH > 3时,400 μL 荧光增强剂可以充分缓冲溶液,不同pH 值下测得的荧光计数基本保持恒定,即待测溶液pH值不会影响铀浓度的测量;随着温度的升高,荧光计数近似线性下降,并在室温23.6℃时得到了铀质量浓度范围为0:120 μg/L 的工作曲线。在此基础上研究了酵母菌对放射性核素铀的吸附作用,为使吸附剂达到最高效利用,对溶液pH 值、吸附速率进行了批次实验,并通过紫外脉冲荧光分析法进行测量, 发现达到吸附平衡所需的最短时间为180 min,吸附的最佳溶液pH 值为5.8 左右。The method of pulse ultraviolet fluorescence was employed to analyze the concentration of radioactive nuclide uranium after adsorbed by baker’s yeast. Influences of fluorescent enhance reagent, pH value, and temperature on measurement of the concentration of trace uranium were investigated. The results showed that 400 μL fluorescent enhance reagent was greatly enough to buffer the solution when pH > 3 and the counts of fluorescence kept constant with the variation of pH, which indicates that the pH of solutions doesn’t affect the determination of uranium concentration, moreover, the counts of fluorescence declined linearly as the increase of the temperature. In addition, the working curve of the determination of uranium concentration within 0.1 20 μg/L was obtained when the temperature was 23.6 ℃. On this basis, the adsorption of uranium by baker’s yeast was studied. For the adsorption of radioactive nuclides of uranium by baker’s yeast to achieve the best use, the batch experiments were carried out on the rate of adsorption and pH of solutions. The method of pulse ultraviolet fluorescence was used to measure and found that the minimum time required to reach adsorption equilibrium was 180 min and the optimum pH value of solutions was about 5.8.     

Growth and Optical Properties of Double Heterostructure GaN／InGaN／GaN Films with Large Composition

The double heterostructure GaN/InGaN/GaN films with different thicknesses of the InGaN layer were grown at 780℃ or 800℃ by metal-organic chemical vapour deposition.The samples were investigated using x-ray diffraction (XRD),room-temperature photoluminescence (PL) and Raman scattering.The dependences of the samples on both the growth temperature and the thickness of the InGaN layer were studied.The composition of InGaN was determined by the results of XRD,and the bowing parameter of InGaN was calculated in terms of the PL spectra.When the thickness of the InGaN layer was reduced,the phase separation of InGaN was found in some samples.The raman frequency of the A1(LO) and E2(low) modes in all the samples shifted and did not agree with Vegard‘s law.     

Transparent conductive reduced graphene oxide thin films produced by spray coating

Reduced graphene oxide thin films were fabricated on quartz by spray coating method using a stable dispersion of reduced graphene oxide in N,N-Dimethylformamide.The dispersion was produced by chemical reduction of graphene oxide,and the film thickness was controlled with the amount of spray volume.AFM measurements revealed that the thin films have near-atomically flat surface.The chemical and structural parameters of the samples were analyzed by Raman and XPS studies.It was found that the thin films show electrical conductivity with good optical transparency in the visible to near infrared region.The sheet resistance of the films can be significantly reduced by annealing in vacuum and reach 58 k?with a light transmittance of 68.69%at 550 nm.The conductive transparent properties of the reduced graphene oxide thin films would be useful to develop flexible electronics.     

THE ANNEALING EFFECT OF CRYSTAL 4H-SiC FILMS PREPARED BY PULSED LASER DEPOSITION

SiC films were prepared by pulsed XeCl laser ablation of ceramic SiC target on Si(100) substrate at temperature 850℃ and post-deposition high temperature annealing above 1100℃ (1100℃-7 Pa). The surface morphology, crystal structure, composition and chemical state of the element in the films before and after annealing were studied by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Auger electron Spectrum, X-ray photoelectron spectrum and photoluminescence methods. It was found that the films were consisted of polycrystal 4H-SiC structure before annealing and were turned into singlecrystal epitaxial 4H-SiC after annealing. The surfaces of the films were smooth and the adhesion of films with the substrate was good. The films were transparent. Excited by the laser with wavelength 290 nm at room temperature, the films emitted two luminescence bands with the peaks at 377 nm and 560 nm. The emission at 377 nm was attributed to the combination of the transmission among the valence and conductor bands, while the one at 560 nm was possibly to be from exciton emission.     

Influence of purity of HfO_2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO_2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO_2 was the main impurity in the two kinds of HfO_2 either in the original HfO_2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO_2 single layer films was much larger than that of the other impurities such as Ti and Fe,which showed that it was just ZrO_2 that made the difference between the optical performance of the film products including the two kinds of HfO_2.With these two kinds of HfO_2 and the same kind of SiO_2,we deposited HfO_2/SiO_2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively, which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

激波管壁AlO自由基B~2∑~+-X~2∑~+和C~2∏_r-X~2∑~+带系辐射光谱的研究

爆轰驱动过程中产生的高温高压气流对铝质膜片、激波管壁产生烧蚀和冲刷作用,以致激波管壁、端盖上附有氧化铝等杂质,而高温下AlO自由基在气体分子的高速碰撞下被激发并产生强烈的辐射,从而干扰了高温气体辐射光谱的分析.用爆轰驱动加热技术将空气加热到4 000～7 000 K,利用多通道光学分析仪对AlO自由基辐射光谱进行分析,实验发现在460～530 nm波长范围内有多支辐射非常强烈的AlO自由基B~2∑~+-X~2∑~+(T_(00)=20 689 cm~(-1))带系辐射谱带,且每支谱带都由多个带头组成,带头间隔约为2 mn,带头处于高频位置并向低频方向伸延.通过实验与理论计算相结合,重点分析了AlO自由基B~2∑~+-X~2∑~+带系辐射光谱的结构特征.AlO自由基C~2∏_r-X~2∑~+(T_(00)=33 047 cm~(-1))带系辐射光谱处于270～335 nm波长范围内,其辐射强度相对于B~2∑~+-X~2∑~+带系较弱,并且与OH基A~2∑~+-X~2∏(T_(00)=32 682 cm~(-1))带系辐射光谱互相干扰而难以分辨,对该波段高温空气的辐射光谱分析产生不利的影响.     

赝势平面波计算铀及铀化合物结构研究

构建了铀的“Vanderbilt”型USPP,能够以相对较小的计算量完成铀金属结构全优化.计算验证表明,超软赝势平面波方法对于金属铀的计算结果与全电子计算结果接近,能正确反映对铀的低温下低对称结构特点.对简单的NaCl以及CaF2结构的铀氧化物、碳化物以及氮化物晶体参数的计算结果与实验值相差不到3%.对非整数计量比UO2+x(0相似文献   

Sensitivity Enhancement in Uranium Determination by UV-Visible Spectroscopy Using Ion Imprinted Polymer

There is need to determination of uranium concentration at ppb level in environmental matrices. Due to low sensitivity of FAAS, UV-Visible Spectroscopy is generally used as measurement technique. In this study, ion-imprinted polymers (IIP) were prepared for uranyl ion (imprint ion) by formation of ternary (salicylaldoxime and 4-vinylpyridine) complex in 2-methoxy ethanol (porogen) following copolymerization with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer using 2,2-azobisisobutyronitrile as initiator. The synthesized polymers were characterized by FT-IR and TGA analysis. Arsenazo Ⅲ in 3 M HClO₄ was used as complexing agent in the measurement step. The optimal pH for preconcentration was found to be between 3.5～6.5 values. The developed method was applied to uranium (Ⅵ) determination in natural water samples.     

硅基片上微米厚度SiO2膜的斜入射红外反射透过谱分析

介绍了硅基片上具有微米厚度的SiO2膜在斜入射情况下的红外反射透过谱测量结果,发现在900~1250cm-1波段内的结果有别于一般的透射谱,出现了峰位基本不变的1100cm-1反射峰。随厚度增大,1100cm-1峰和1200cm-1凹谷的降低逐渐变为迟缓。当厚度达到2μm以上后,1075~1250cm-1谱线的变化已不再明显。通过分析表明,结果中包含了SiO2膜的表面反射谱和SiO2膜层的吸收谱。当膜厚达到微米量级而引起较大吸收时,表面反射谱的贡献相当明显。此时,对该段谱线的分析不能仅考虑膜层的吸收。     

A novel method for improving the adhesion strength of the electrodeposited Ni films in MEMS

Adhesion performance of MEMS materials is increasingly important with the widely use of miniaturized devices. This paper proposed a novel method for improving adhesion performance between electrodeposited Ni multi-layers. The new method is to treat the Ni substrate in nickel chloride plating solution by pulse reverse current technique before electrodeposition. The dense oxide film of Ni substrate can be removed effectively by this electrochemical method, meanwhile, the proper roughness of Ni substrate is in favor of epitaxial growth during electrodeposition. Moreover, the Ni film is electrodeposited by the new method with low stress and coarse crystal grain. Consequently, the adhesion performance of Ni films is improved dramatically. The experimental results show that the adhesion performance of Ni film electrodeposited by the new method is about 3 times that of by traditional method.     

铀元素的激光诱导击穿光谱测量分析

为促进LIBS技术在微量重金属元素检测以及核污染检测领域的应用,提高检测灵敏度和准确性,采用了激光双脉冲LIBS技术和光电双脉冲LIBS技术,分别对土壤和二氧化硅中的铀元素进行分析。首先,对激光脉冲能量、电压和采集延时等参数进行优化,提高铀元素特征谱线的强度和信噪比;然后在优化实验参数条件下,对含不同浓度铀元素的土壤样品和二氧化硅样品进行激发;选取UII 367.01 nm、 UII 454.36 nm两条铀元素的特征谱线作为分析线,通过铀元素浓度与特征谱线强度的线性关系,建立定标曲线。双脉冲激光激发条件为：激光脉冲1作为预脉冲,主要参数为1 064 nm, 90 mJ, 9.2 ns,激光脉冲2作为再加热脉冲,主要参数为355 nm, 50 mJ, 8 ns,两个脉冲的时间间隔800 ns,光谱采集相对第二个脉冲延时1μs,得到铀元素在土壤和二氧化硅两种样品中的浓度检测下限分别为572和110 mg·kg^-1,拟合优度值R²分别为0.958和0.999。在光电双脉冲激发条件下,激光脉冲作为预脉冲,主要参数为355 nm, 50 mJ, 8 ...     

Cs 39D态Rydberg原子Stark光谱的实验研究

本文从理论和实验上对Cs39D态Rydberg原子在弱电场作用下的Stark效应做了详细研究. 理论上利用数值方法计算了Cs原子39D态的Stark结构;实验上,采用两步激发超冷基态原子获得超冷Rydberg原子,通过场电离的方法获得了39D态的Stark光谱,测量获得α^5/2₂,α^5/2₀,α^3/2₂和α^3/2₀相应的极化率分别为：62(7),－146(13), 73(6) 和－106(20) MHz·V^-2cm²,实验结果与理论相符合. 关键词： Rydberg原子 Stark结构 场电离 极化率     

80keV N离子注入对ZnO薄膜结构的影响

室温下用80keVN离子注入ZnO薄膜样品,注量分别为5.01014,5.01015和5.01016ions/cm2,然后用X射线衍射和透射电镜技术对样品的结构特性进行了表征。实验结果表明,由高度(002)择优取向的致密柱状晶构成的薄膜中,注入5.0×1015ions/cm2时,观测到缺陷生成和局域无序化现象,但薄膜总体结构仍保持柱状晶和(002)择优取向;随着注量的增大,晶格常数c和压应力呈增大趋势。对注入N离子对ZnO薄膜结构特性的影响机理进行了简单的讨论。     

94MeV Xe离子辐照引起的薄膜硅光学带隙变化研究

室温下,用94MeV的Xe离子辐照纳米晶和非晶硅薄膜以及单晶硅样品,辐照量分别为1.0×1011,1.0×1012和1.0×1013ions/cm2。所有样品均在室温下用UV/VIS/NIR光谱仪进行检测分析。通过对比研究了纳米晶、非晶、单晶硅样品的光学带隙随Xe离子辐照量的变化。结果表明,不同结构的硅材料中Xe离子辐照引起的光学带隙变化规律差异显著:随着Xe离子辐照量的增加,单晶硅的光学带隙基本不变,非晶硅薄膜的光学带隙由初始的约1.78eV逐渐减小到约1.54eV,而纳米晶硅薄膜的光学带隙则由初始的约1.50eV快速增大至约1.81eV,然后再减小至约1.67eV。对硅材料结构影响辐照效应的机理进行了初步探讨。     

样品厚度对薄膜法X射线荧光光谱测量的影响研究

分别以富集有Cr,Pb和Cd三种元素的尼龙薄膜样品及玻璃纤维滤膜为研究对象,采用滤膜叠加的方式,通过XRF光谱仪测量不同样品厚度下薄膜样品的XRF光谱,根据测得的尼龙薄膜样品中Cr,Pb,Cd元素及玻璃纤维滤膜中Ca,As和Sr元素特征XRF性质的变化,研究样品厚度对薄膜法XRF光谱测量的影响。结果表明：薄膜样品厚度对不同能量区间上元素特征谱线荧光性质的影响并不相同。元素特征谱线能量越大,元素特征X射线荧光穿透滤膜到达探测器的过程中损失越少;但由薄膜样品厚度增加引起的基体效应却越强,相应特征谱线位置处的背景荧光强度就越大,因此样品厚度增加所引起的基体效应对薄膜法XRF光谱测量的灵敏度影响就越大。对于特征谱线能量较低(能量小于7 keV)的元素,以增加薄膜样品厚度的方式来增加待测组分的质量厚度浓度,并不能有效地提高薄膜法XRF光谱测量的灵敏度;对于特征谱线能量较高的元素(能量＞7 keV),可以通过适当增加样品厚度以增加被测组分的质量厚度浓度的方式来提高XRF光谱测量的灵敏度,薄膜样品厚度在0.96～2.24 mm内,更有利于XRF光谱的测量与分析。该研究为大气及水体重金属薄膜法XRF光谱分析中薄样制备及富集技术提供了重要的理论依据。