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1.
Because of the high neutron capture cross section for five consecutive europium isotopes, Eu2O3 is of interest as a control material for nuclear reactors. A tendency toward excessive grain growth degrades its mechanical properties. Small amounts of HfO2 and Ta2O5 were added to the Eu2O3 in attempts to suppress this grain growth. Three at % substitution of Hf for 相似文献
2.
Yo Tokunaga Masahiko Osaka Shuhei Miwa Hiroyuki Chudo Yoshinobu Shiokawa 《Journal of Nuclear Materials》2010,396(1):107-111
In order to investigate the magnetic properties of Am4+ ions in the cubic fluorite structure, we have performed 17O NMR measurements on (Pu0.91Am0.09)O2. We have observed a temperature-dependent 17O NMR line broadening induced by classical dipolar hyperfine fields from the Am 5f moments. From NMR line simulations, the effective moment of the Am moments has been estimated to be μeff=1.38μB/Am. This value is comparable with μeff=1.32 or 1.53μB/Am reported for AmO2. We have also carried out nuclear relaxation measurements for 17O nuclei. The magnetization recovery has been found to exhibit a nonexponential time dependence with an exponent β∼0.5. This result is well understood in terms of the nuclear relaxation mechanism induced by the Am 5f moment fluctuations via dipolar hyperfine fields. 相似文献
3.
M. Ali 《Journal of Nuclear Materials》2007,360(2):99-103
Enthalpy increment measurements on La2Te3O9(s) and La2Te4O11(s) were carried out using a Calvet micro-calorimeter. The enthalpy values were analyzed using the non-linear curve fitting method. The dependence of enthalpy increments with temperature was given as: H°(T) − H°(298.15 K) (J mol−1) = 360.70T + 0.00409T2 + 133.568 × 105/T − 149 923 (373 ? T (K) ? 936) for La2Te3O9 and H°(T) − H°(298.15 K) (J mol−1) = 331.927T + 0.0549T2 + 29.3623 × 105/T − 114 587 (373 ? T (K) ? 936) for La2Te4O11. 相似文献
4.
A laser process is presented that has been specially developed for joining oxide ceramics such as zirconium oxide (ZrO2) and aluminium oxide (Al2O3). It details, by way of example, the design of the laser process applied for to producing both Al2O3-Al2O3 and ZrO2-ZrO2 joints using siliceous glasses as fillers.The heat source used was a continuous wave diode laser with a wavelength range of 808-1010 nm. Glasses of the SiO2-Al2O3-B2O3-MeO system were developed as high-temperature resistant brazing fillers whose expansion coefficients, in particular, were optimally adapted to those of the ceramics to be joined. Specially designed measuring devices help to determine both the temperature-dependent emission coefficients and the synchronously determined proportions of reflection and transmission.The glass-ceramic joints produced are free from gas inclusions and macroscopic defects and exhibit a homogenous structure. The average strength values achieved were 158 MPa for the Al2O3 system and 190 MPa for the ZrO2 system, respectively. 相似文献
5.
Monika Arora S. Baccaro D. Singh D.P. Singh 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(5):817-820
The infrared absorption spectra of PbO-Al2O3-B2O3-SiO2 glasses have been measured in the spectral range 600-4000 cm−1 before and after absorbed dose of 50 Gy, 4 kGy and 50 kGy to investigate the structural change due to irradiation. The structural change due to composition has also been discussed. The experimental results clearly indicate that after irradiation, a significant change in structure of lead alumino borosilicate glass network is observed. It was shown that BO4 groups decreases and BO3 groups increases with the increase of Al2O3. 相似文献
6.
The incorporation of gadolinium directly into nuclear fuel is important regarding reactivity compensation, which enables longer fuel cycles. The incorporation of Gd2O3 powder directly into the UO2 powder by dry mechanical blending is the most attractive process, because of its simplicity. Nevertheless, processing by this method leads to difficulties while obtaining sintered pellets with the minimum required density. This is due to the bad sintering behavior of the UO2-Gd2O3 mixed fuel, which shows a blockage in the sintering process that hinder the densification process. Minimal information exists regarding the possible mechanisms for this blockage and this is restricted to the hypothesis based on the formation of a low diffusivity Gd rich (U,Gd)O2 phase. The objective of this investigation was to study the phase formation in this system, thus contributing to clarifying the causes of the blockage. Experimental evidence indicated the existence of phases in the (U,Gd)O2 system that revealed structures different from the fluorite-type UO2 structure. These phases appear to be isostructural to the phases observed in the rare earth-oxygen system. 相似文献
7.
The high-temperature specific heat of solid UO2, ThO2, and Al2O3 can be represented by an equation of the form , (1) where ?D is the Debye temperature, F(?D/T) is the Debye function, represents contributions of the anharmonic vibrations within the lattice, and denotes the number of atoms per molecule. In the liquid the corresponding equation is , (2) where h is the anharmonic term. It is shown that for Al2O3 and UO2, where experimental data for the liquid phase are also available, has the same value, Indicating that both materials behave identically. If we compare the thermodynamic relationship , (3) where V is the volume, the volume expansion coefficient, and the bulk modulus, with equation (1), It follows that d must be equal to ; the value of is calculated in the temperature region where d was obtained; within experimental error they are equal. 相似文献
8.
The composition of oxides formed on steel surfaces within power reactors may influence heat transfer efficiency. Previous studies have indicated that carbon is deposited on spinal-type oxides containing manganese, iron, cobalt, nickel and chromium. In this investigation, characterised manganese oxides have been subjected to γ-irradiation under conditions similar to those experienced in reactors in an effort to understand the catalytic processes involved in deposit initiation and growth. Mn3O4 and Mn2O3, under the conditions present in the γ-cell, were reduced to MnO during the time of exposure. Relative carbon deposition rates were observed to follow the trend MnO>Mn3O4≈Mn2O3. 相似文献
9.
The crystal structures of Pu2T3Si5 with T Fe, Tc, Re synthesized from the elements by argon arc melting have been characterized from X-ray powder diffraction data. All compounds crystallize with the Sc2Fe3Si5 type. The distribution of the various structure types An(RE)2T3Si5 was plotted for An U, Np, Pu and T Mn to Pt. The crystallographic relationships among these structure types is discussed. 相似文献
10.
The crystal structures of Pu2T3Si5 with T = Fe, Tc, Re synthesized from the elements by argon arc melting have been characterized from X-ray powder diffraction data. All compounds crystallize with the Sc2Fe3Si5 type. The distribution of the various structure types An(RE)2T3Si5 was plotted for An = U, Np, Pu and T = Mn to Pt. The crystallographic relationships among these structure types is discussed. 相似文献
11.
12.
NHO3氧化去除Np—Pu反萃液中的H2C2O4 总被引:3,自引:1,他引:2
研究了用NHO3氧化去除TRPO流程反萃Np-Pu的H2C2O4反萃液中H2C2O4的条件。7.5mol.L^-1HNO3-0.3mol.L^-1H2C2O4混合液于90℃下蒸发130h和100℃下蒸馏回流6h,H2C2O4可完全分解去除;混合液中添加适量催化剂MnCO3,于100℃下蒸发或蒸馏回流,H2C2O4分解加速,1-1.5h内H2C2O4完全分解。蒸发或蒸馏回流过程中产生的HNO2把Np 相似文献
13.
14.
Masaru Nagura Akihiro Suzuki Takeo Muroga Takayuki Terai 《Fusion Engineering and Design》2009,84(7-11):1384-1387
Er2O3 is candidate material for insulating coating to prevent the magnetohydrodynamic (MHD) pressure drop in the self-cooled liquid Li blanket system. Although Er2O3 is stable material, detailed chemical behavior in liquid Li is not clear. Corrosion behavior of bulk Er2O3 in Li is investigated in static and flowing condition in the present study. After these tests, good compatibility of Er2O3 was confirmed and slight formation of LiErO2 was detected by XRD analysis. This chemical behavior did not change in a static and flowing tests, however some of the corrosion product of LiErO2 was removed easily by the Li flow. Intensity of LiErO2 peaks in XRD spectrum suggests that the temperature gradient may affect the reaction rate in the natural convection loop. Since corrosion rate of Er2O3 is very small, slight change in state will be important information to evaluate lifetime of coating. 相似文献
15.
报道了用于加速器质谱计^26Al分析的Al2O3的制备流程及^26Al的测量过程。制备的空白样品^26Al/^27Al比值<10^-13,显示出同量异位素^26Mg干扰小。制备流程是成功的。 相似文献
16.
本文研究了Al2O3掺量对独居石玻璃陶瓷固化体结构和化学稳定性的影响。用傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)方法表征样品结构,用溶解速率法和全谱直读等离子体发射光谱(ICP-OES)分别测定样品在浸出液中浸泡后的失重速率及各元素的浸出浓度,以研究固化体的化学稳定性。研究结果表明:当Al2O3掺量为4%(摩尔分数)时,在980 ℃下保温3 h得到的独居石玻璃陶瓷固化体具有较高的化学稳定性,浸泡14 d时其质量浸出率最低,约为8.1 ng/(cm2•min),其中Ce、La元素在浸出液中均未检出;固化体的主晶相为独居石,结构中含有大量稳定的正磷酸基团[PO4]3-和少量的焦磷酸基团[P2O7]4-,不存在偏磷酸基团[PO3]-。 相似文献
17.
The kinetics of initial stage sintering of UO2 powder were reinvestigated, using Ar-10% H2 atmosphere. The effect of the addition of neodynium oxide was studied. The results revealed that surface and grain boundary diffusion mechanisms act simultaneously. The values of activation energies were found to be in the temperature range 870–942°C and in the temperature range of 942–1030°C for UO2, and in the temperature range 1030–1150°C for UO2 + Nd2O3. An important decrease in the calculated diffusion coefficient occurs by the addition of Nd2O3. 相似文献
18.
estmir Jech
Roger Kelly
《Journal of Nuclear Materials》1966,20(3):269-280Previous work on diffusion in inert-gas bombarded Al2O3 has revealed the presence of four diffusion processes, of which two take place well below the temperatures for self-diffussion, one agrees with self-diffusion, and one occurs at temperatures well above those for self-diffusion. The present work serves to explore in greater detail the two low-temperature processes. It is shown that the first, which is found in -Al2O3, Al(OH)3, and γ-Al2O3beginning at about 100° C, is consistent with a range of ΔH's of 28 to 50 kcal/mole. The mechanism of the process is hinted at by the fact that it overlaps the temperatures both for Al(OH)3decomposition and for point-defect motion in -Al2O3; the correlation with point defects is believed, however, to be the more significant. The second process, which is found only in -Al2O3 beginning at 500–650° C, implies an essentially single ΔH lying between 69 and 79 kcal/mole. It was suggested previously by Matzke and Whitton on the basis of electron diffraction that the process could be attributed to the amorphous-crystalline transition of -Al2O3. Further aspects of low-temperature diffusion in Al2O3 were revealed by comparing autoradiographs of specimens of -A2O3which were bombarded to various doses and then either heated to 850° C or immersed in unheated 12N NaOH. Thus regions exposed to a high dose and which would be expected to be amorphous, had an increased sticking factor, a greater tendency to lose gas during heating, and an enhanced chemical reactivity. 相似文献
19.
通过机械混合法制备了一种基于铌酸银(AgNbO_3)的耐高温放射性碘吸附剂(AgNbO_3/Al_2O_3)。和常规载银吸附剂(Ag/Al_2O_3)相比,AgNbO_3/Al_2O_3吸附剂的吸附性能更为稳定;特别是在650℃以上时,其对放射性碘的去污因子远高于常规载银吸附剂。表征测试结果表明,该吸附剂结构稳定性良好,可耐受较长时间的高温。热重测试和高温脱附试验等结果表明,碘化银在AgNbO_3/Al_2O_3吸附剂表面稳定性的提高是该吸附剂在高温时吸附性能更佳的主要原因,其将来有望用于核事故中的应急处置。 相似文献
20.
The previous work by our group showed experimental evidence that supports the idea that a diffusion barrier is formed around Gd2O3 agglomerates due to the formation of gadolinium-rich (U,Gd)O2 phases with low diffusivity. This would be the reason for the bad sintering behavior of the UO2-Gd2O3 fuel. The objective of this investigation was to confirm that hypothesis by direct experimental evidence. Analysis of the results showed that the diffusion barrier hypothesis is not applicable. 相似文献