Gas-Phase Conversion of Uranium Mononitride in a Nitrating Atmosphere

Radiochemistry - Gas-phase conversion of UN to water-soluble compounds in NOx-air, NOx-H2O (vapor)-air, or HNO3 (vapor)-air atmosphere (hereinafter, nitrating atmosphere) at temperatures from 298...     

Gas-Phase Conversion of Uranium Monocarbide in a Nitrating Atmosphere

Radiochemistry - Gas-phase conversion of UC in NOx-air, NOx-H20 (vapor)-air, and HN03 (vapor)-air atmospheres in the temperature interval from 298 to 673 K was studied. In the course of the...     

金属铀的氧化腐蚀及防护

铀的氧化腐蚀和防护研究是核材料研究领域的一个重要组成部分。综述了铀在U＋O2体系、U＋H2O(v)体系和U＋H2O（v)＋O2体系中的氧化行为与防护进展，包括氧化腐蚀机理、腐蚀形态、防护措施、防护机理以及防护的发展方向。     

Gas-Phase Conversion of Oxide Phases of Lanthanides and Uranium to Water-Soluble Compounds

Radiochemistry - Gas-phase conversion to water-soluble compounds of individual rare-earth element (REE) (La, Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm, Lu) oxides and oxide systems (U,Ce)Ox and (U,Nd)Ox...     

XPS研究金属铀氧化反应动力学

X射线光电子能谱技术被广泛用于研究材料表面研究。XPS谱图能够准确及时反映10¹ nm深度内材料表面元素组成与结构信息。利用激发电子的穿透特性,XPS能够作为半定量的研究手段。本文利用XPS测厚技术研究了金属铀在5×10^-6 Pa氧气压力、温度低于413 K条件下的氧化反应动力学行为,在该研究条件下金属铀初始氧化遵循抛物线规律,反应活化能为23.9 kJ/mol。     

Oxidation of Uranium Dioxide with Manganates and Permanganates in Carbonate Solutions

Oxidation, dissolution of uranium dioxide with some alkali, alkaline-earth metal man-ganates and permanganates in carbonate solution was studied. The kinetics of decomposition of potassiummanganate and permanganate in solutions of some carbonates were studied spectrophotometrically in the range of pH from 7.8 to 13.0. It was found that the stability of MnO₄ ^- and MnO₄ ^2- ions and the pathways of their decomposition are governed by both pH and the nature of salts. The results of similar measurements in the presence of uranium dioxide showed that throughout the studied range of pH to the higher rate of conversion of KMnO₄ to K₂MnO₄ corresponds the higher rate of oxidation and dissolution of UO₂ in carbonate solution.     

铀及铀合金防护镀层的研究进展

铀是一种非常重要的战略核材料,纯铀又是化学活性极强的材料,在大气中放置很短的时间就会在其表面产生氧化和腐蚀.因此,对铀材必须实行涂层保护或表面合金化才能增强其抗腐蚀效果.从离子注入、离子镀以及表面合金化处理3方面综述了铀及铀合金的防腐涂层方法的研究.     

Gas-Phase Infrared Band Contour Simulations for C70

Theoretical ro-vibrational band-contour simulations are reported for the fullerene C_7o in the gas-phase. For a prolate symmetric top there are A-type and B-type bands possible, these are simulated in the temperature range 10 -100 K. The results are expected to be useful for cold (molecular-beam) optical spectroscopy of C₇₀ as well as in astronomical searches for this fullerene and its ionized forms.     

U和UO2状态方程研究进展

铀和二氧化铀都是核科学与核工程中的重要材料,长期以来都不缺乏对它们的状态方程的研究.它们生产、存储和使用的环境复杂,涵盖宽温、宽压、强辐照、表面辐射、氦泡演化等极端条件,需要从实验和理论出发获取不同温度和压力下的材料物性,如晶体结构、相变行为、压缩性质、弹性性质与输运性质.此外,它们都属于强关联电子体系,拥有丰富的相图与奇特的物理性质,因此在实验与理论上研究它们的状态方程等物性具有极大的挑战性,该项研究一直属于前沿研究的热点.数十年来,人们采取各种实验手段,对铀和二氧化铀的热力学物性进行了测量;但由于铀及其化合物的特殊性质,相关实验研究工作仍存在一定程度上的困难.而另一方面,自1990年代以来,随着第一性原理方法的发展,使用密度泛函理论(DFT)方法对铀和二氧化铀物理性质展开计算的工作也不断涌现,不仅与实验工作相互验证,而且填补了实验条件无法企及的极端条件下的参数空白.随着计算机软硬件和数值算法的发展,相关DFT方法已经获得了较大突破,对铀和二氧化铀状态方程的描述也更为准确.其中,修正电子多体关联效应的动力学平均场方法(DMFT)以及修正声子振动能的平均场势方法(MFP)等算法是值得研究者进一步关注的.本文就20世纪以来对金属铀和二氧化铀实验和理论状态方程的研究进展进行了梳理,先后针对实验测量和理论计算两方面的晶体结构和相变行为、准静态压缩与冲击绝热压缩曲线、弹性力学、输运性质进行了概括总结,并探讨了二氧化铀晶体缺陷行为的相关研究工作.此外,本文还利用第一性原理方法对铀和二氧化铀的状态方程做了简要的计算,验证了已有公开文献中的结果,这将有助于后续研究.     

Uranium Superconductivity Redux

Since the discovery of heavy-fermion superconductivity in uranium compounds in the early 1980s, other uranium compounds have been discovered that are fully as interesting to study. However, as we look forward in the year 2000, we now have higher-purity, single crystals of the element itself. Preliminary resistivity and ac susceptibility measurements show the improved quality of the samples and thus hold the promise of understanding many aspects of its superconductivity, which have remained untouched for almost 25 years.     

Nano-Phase W and W-Ti Composite via Gas-Phase Combustion Synthesis

Nano-particulates of W and W-Ti have been synthesized by a gas-phase combustion process employing exchange reactions between sodium and metal chlorides. Gaseous reactants were introduced in a coflow diffusion-flame burner. To minimize agglomeration and protect the particles from contamination during subsequent exposure to atmosphere, the NaCl by product was condensed onto the particles within the flame. Resulting particles were unagglomerated, cubic or hexagonal in shape with an average size of ca. 30 nm. The nano-crystalline W and W-Ti particulates were consolidated by hot pressing at temperatures of 1000 to 1200°C in argon atmosphere. The consolidates were found to be greater than 96% dense with grain sizes of 30 to 40 nm.     

铀及其合金表面防护技术的概况及展望

铀作为核能材料,应用很广泛.但铀的化学性质非常活泼,极易腐蚀,研究者们对其表面防护技术进行了许多研究,总结了铀及其合金各种表面防护技术的发展及应用,并对未来的发展趋势进行了展望.     

Deposition of Coatings Based on Boron Carbide by the Gas-Phase Method

Materials Science - We present the results of investigation of the production of boron carbide by the method of hydrogen reduction of boron trichloride BCl3 in a vapor of toluene C7H8. The...     

The Effect of the Developing Solution Volume on the Oxidation of Solution Components in Various Type Developing Machines

Available theoretical data on continuous developing processes of conventional processors cannot be applied to the specific developing conditions in the chambers of jet spray machines. For such conditions of development, other equations have been deduced revealing the substantial influence of processing solution volume on solution oxidation by oxygen from the air drawn-in into the operating chambers due to their insufficient air-tightness and carried over with the film to be treated.     

Formation of Carbide Coatings on Nicalon Fiber by Gas-Phase Transport Reactions

Problems concerning the formation of coatings composed of the carbides of metals of the IV–V groups on Nicalon fiber under conditions of chemical transport through the gas phase are considered. Chemical reactions are considered which proceed in the zone of metal and fiber disposition. Scanning electron microscopy study shows that the formed carbide coatings are uniform and possess a high adhesion to the fiber.     

Preparation of Powdered Uranium Oxides by Denitration of Nitric Acid Uranium Solutions Using UHF Radiation

Radiochemistry - Denitration of nitric acid uranium solutions under the action of UHF radiation in ambient and reducing atmosphere in the presence of organic reductants containing amino groups...