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- Ye, Mingliang, et al.
(författare)
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Preparation and characterization of SiC-ZAC composite material for immobilizing the simulated radioactive graphite
- 2022
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Ingår i: Progress in nuclear energy (New series). - : Elsevier. - 0149-1970 .- 1878-4224. ; 143
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Tidskriftsartikel (refereegranskat)abstract
- For the safe treatment and disposal of radioactive graphite, SiC-ZAC (ZAC: ZnO-Al2O3-CaO glass-ceramic) composite materials were designed, in which ZAC is used as a sintering additive. The performance of ZAC was firstly studied by ASTM C1285 leaching test to obtain a formula composition with high chemical stability. Then, using the optimized formula of ZAC, the SiC-ZAC composites were prepared by vacuum calcination at 1350 degrees C-1410 degrees C for the immobilizing of simulated radioactive graphite, and the structure and compositions of SiC-ZAC composites were studied by XRD, SEM, EDS. The material Gibbs free energy function method was used to calculate the thermodynamics of SiC-ZAC composites to investigate the reaction ways among Si, C and ZAC. The results show the Z30 (30 wt% ZnO, 44.91 wt% Al2O3, 25.09 wt% CaO) glass-ceramic is the applicable formula composition due to its high chemical stability, in which the normalized elemental mass loss of Zn, Al, Ca are 10(-)(6) g/m(2)-10(-)(5) g/m(2), 10(-1) g/m(2), 10(-1) g/m(2) respectively. Calcined at 1350 degrees C for 2 h, the B-Z30(0)-1(70.05 wt% Si, 29.95 wt% C) sample can be obtained with the phase compositions of beta-SiC, alpha-SiC and a small amount of residual graphite. Moreover, the formations of Ca2Al2SiO7 and CaAl4O7 crystalline phase had a negative effect on the immobilization of simulated radioactive graphite in SiC-ZAC composites.
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| 2. |
- Ye, Mingliang, et al.
(författare)
-
Preparation and properties of situ-sintered SiC ceramics aided by ZnO-Al2O3-CaO
- 2022
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 890
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Tidskriftsartikel (refereegranskat)abstract
- The safe treatment and disposal of radioactive graphite waste is becoming an important issue worldwide. The objective of this paper is to prepare the SiC-ZAC (ZAC: ZnO-Al2O3-CaO) composite ceramic for immobilizing radioactive graphite, where ZAC is as sintering additives. The effects of the sintering system and ZAC content on the phase compositions, microstructure, and properties of SiC-ZAC composite ceramic are studied by XRD, SEM-EDS, TEM-EDS, linear shrinkage, Vickers hardness, and thermal conductivity. By vacuum hot pressing sintering at 1600 degrees C for 1 h, the results show that the S-35-160 0 (65 wt% SiC, 10.5 wt% ZnO, 15.72 wt% Al2O3, 8.78 wt% CaO) sample is the potentially applicable formula composition due to its better performance, in which the Vickers hardness and the thermal conductivity are 165.2 HV10, 14.6 W m(-1) k(-1) respectively, and the normalized elemental mass loss of Si, Al and Ca are 0.0064-0.0108 g/m(2), 21.4784-24.7837 g/m(2), 56.9108-67.5637 g/m(2) after 42 days at pH = 5/7/9 solution, respectively. Importantly, ZAC sintering additives can form the bond phases of CaAl4O7, CaAl2O4, Ca3Al2(OH)(12), and Ca2Al2SiO7 under relatively low temperatures to reduce the sintering temperature for SiC ceramics. Meanwhile, the existing form of the Zn element is revealed: one part of the Zn forms glass phase, and the other part volatilized by carbothermic reduction.
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