物理化学学报 >> 2015, Vol. 31 >> Issue (9): 1810-1814.doi: 10.3866/PKU.WHXB201507203

材料物理化学 上一篇    下一篇

Pu在Gd2Zr2O7基质中的模拟固化: (Gd1-xCex)2Zr2O7+x的热物理性能研究

夏祥来1,2,李林艳2(),郭放1(),苏伟3,刘艳3,陈晓谋3,潘社奇3   

  1. 1 辽宁大学化学院,沈阳110036
    2 清华大学核能与新能源技术研究院,北京100084
    3 中国工程物理研究院,四川绵阳621900
  • 收稿日期:2015-03-26 发布日期:2015-09-06
  • 基金资助:
    国家自然科学基金委员会和中国工程物理研究院联合基金(11176014);国家自然科学基金(21471088)

Simulation of the Immobilization of Pu in the Gd2Zr2O7 Matrix by Investigating the Thermophysical Properties of (Gd1-xCex)2Zr2O7+x

Xiang-Lai. XIA1,2,Lin-Yan. LI2(),Fang. GUO1(),Wei. SU3,Yan. LIU3,Xiao-Mou. CHEN3,She-Qi. PAN3   

  1. 1 College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
    2 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, P. R. China
    3 China Academy of Engineering Physics, Mianyang 621900, Sichuan Province, P. R. China
  • Received:2015-03-26 Published:2015-09-06
  • Supported by:
    NSAF(11176014);National Natural Science Foundation of China(21471088)

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摘要：

采用高温固相反应,以NaF作助熔剂,在1000 ℃的温度下合成了锕系元素Pu的模拟固化体(Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7).研究了模拟固化体的物相、热膨胀系数(TEC)、热导率(TC)随温度及组成的变化规律.粉末X射线衍射(XRD)测试结果表明: Gd2Zr2O7基质本身呈弱有序烧绿石结构,而用Ce4+取代Gd3+的模拟固化体都呈缺陷萤石结构. (Gd1-xCex)2Zr2O7+x的Ce(3d) X射线光电子能谱(XPS)有六个峰,结合能分别位于881.7, 888.1, 897.8, 900.4, 907.1, 916.1 eV处,与CeO2的XPS图谱非常相似,说明Ce为四价.随着温度的升高,所有样品的热膨胀系数总体上呈增大趋势.在室温至750 ℃附近,大部分样品的热导率随温度的升高而降低,之后热导率又呈小幅上升.在相同温度下,固化体(Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7)的热膨胀系数及热导率随组成变化呈相同趋势:在0 ≤ x ≤ 0.1范围内随x的增大而增大,随后在x = 0.1-0.7时逐渐减小.

关键词: 核废料固化, 烧绿石结构, 萤石结构, 热膨胀系数, 热导率

Abstract:

Polycrystalline samples of (Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7) were synthesized by solid-state reaction using NaF as a flux at 1000 ℃ to simulate Pu-immobilization in the Gd2Zr2O7 matrix. Phase transformation and variation of the thermal expansion coefficients (TECs) and thermal conductivities (TCs) of the samples with temperature and composition were investigated. Powder X-ray diffraction (XRD) patterns show that pure Gd2Zr2O7 has a weakly ordered pyrochlore structure, whereas Ce-containing samples (i.e., the Pu-simulated solidified samples) exhibit a defect fluorite structure even if x is as low as 0.1. When x reaches 0.7, the XRD peaks of these samples widen. In the Ce 3d X-ray photoelectron spectrum (XPS) of (Gd1-xCex)2Zr2O7+x there are six peaks located at binding energies of 881.7, 888.1, 897.8, 900.4, 907.1, and 916.1 eV, which are almost the same as the peaks of CeO2. The Ce 3d XPS reveals that the Ce species in (Gd1-xCex)2Zr2O7+x are tetravalent. The TECs of (Gd1-xCex)2Zr2O7+x (0 ≤ x ≤ 0.7) generally increase with increasing temperature. At the same temperature, the TECs and TCs exhibit the same variation trend with the composition of the simulated solidified forms: they decrease from x = 0 to 0.1 and then linearly increase from x = 0.1 to 0.7.

Key words: Immobilization of nuclear waste, Pyrochlore structure, Defect fluorite structure, Thermal expansion coefficient, Thermal conductivity