Self-propagating chemical furnace synthesis of nanograin Gd2Zr2O7 ceramic and its aqueous durability

He, Zongsheng; Zhang, Kuibao; Xue, Jiali; Zhao, Wenwen; Zhang, Haibin

doi:10.1016/j.jnucmat.2018.10.035

Cited by 26 publications

(7 citation statements)

References 35 publications

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“…Anyhow, the leaching rates of Ca, Cu, and Hf are lower than or comparable to borosilicate glass (about 10 -2 g·m -2 ·d -1 , 90 ℃) [40,41]. Compared with zirconolite and pyrochlore based waste forms prepared by CS, hot pressing (HP), and hot isostatic pressing (HIP) [22,[42][43][44][45], the leaching rates of Ca and Cu in this research are much higher. Nevertheless, the Hf-bearing zirconolite-rich composite waste form is a durable waste form and the combustion synthesis is a rapid route for nuclear waste disposal.…”

Section: Chemical Stability Of the Cu-hf-06 Samplementioning

confidence: 67%

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Zhang

Yin

et al. 2019

J Adv Ceram

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Zirconolite is recognized as one of the most durable waste matrices for the disposal of high-level radioactive wastes (HLWs). In this study, HfO 2 was employed as the surrogate of tetravalent actinides. Hf-bearing zirconolite-based composite waste forms (CaZr 1-x Hf x Ti 2 O 7 ) were rapidly prepared by combustion synthesis (CS) using CuO as the oxidant, where quick pressing (QP) was introduced to obtain densified samples. Similar as solid state reaction process, the Zr site of zirconolite can be totally occupied by Hf (x = 1.0) under the CS reaction. The original 2M zirconolite structure was maintained and a small amount of perovskite impurity phase was generated in the final products. The aqueous durability of representative sample (Cu-Hf-0.6) was tested, where the 42-day normalized leaching rates (LR i ) of Ca, Cu, and Hf are 0.25, 3.10×10 -2 , and 1.11×10 -8 g·m -2 ·d -1 .glasses is generally recognized as the first generation waste management method. In recent decades, highly durable ceramic materials have been proposed as an alternative medium for HLW immobilization [4][5][6]. The naturally existed zirconolite and pyrochlore are important actinide-bearing ceramic materials, which exhibit excellent chemical and physical durability over geological time scales [7][8][9][10][11][12]. Zirconolite (ideally CaZrTi 2 O 7 ) was also developed as a crystalline phase to sequester Pu from surplus nuclear weapons, which makes it receive great attention as a potential waste form [13].Zirconolite is formed by the stacking layers of edge shared Ti-O polyhedra (TiO 5 and TiO 6 ) and layers of Ca 2+ and Zr 4+ cations [14]. Due to that the Ti 4+ and Zr 4+ ions can be mutually occupied, the zirconolite J Adv Ceram 2019, 8(3): 448-455 449 www.springer.com/journal/40145

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Section: Chemical Stability Of the Cu-hf-06 Samplementioning

confidence: 67%

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Zhang

Yin

et al. 2019

J Adv Ceram

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“…In general, the fabricated (Gd,A) 2 (Zr,B) 2 O 7 waste form showed a considerable chemical durability as compared with reported results (Table 5). 22,25‐27 …”

Section: Resultsmentioning

confidence: 99%

“…12 Among these ceramics, pyrochlore is commonly employed to immobilize nuclear waste due to its high thermal stability, 13,14 high thermodynamic stability, 15,16 high chemical durability, 17,18 and physical stability. 15,[19][20][21] In recent years, a series of treatment methods have been developed for incorporating TRPO waste using pyrochlore, including solid reaction method with simple operation, 22,23 self-propagating high-temperature synthesis plus quick pressing method with fast reaction, 24,25 microwave sintering with fast heating rate and low energy consumption, 26 flash sintering with extremely short sintering time, 27 and spark plasma sintering (SPS). [28][29][30][31] SPS has the advantages of fast heating rate and short holding time, which makes it widely used to solidify radionuclides.…”

Section: Introductionmentioning

confidence: 99%

Effect of improved trialkyl phosphine oxides waste content on phase composition and density of spark plasma sintered Gd ₂ Zr ₂ O ₇ ceramics

Wei

Wen³

et al. 2021

Int J Energy Res

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As a rapid sintering method, spark plasma sintering (SPS) process has been widely applied to immobilize nuclear waste. In this work, trialkyl phosphine oxides (TRPO) were immobilized by the mixture of Gd 2 O 3 and ZrO 2 with SPS proceedings at 1650 C in 3 minutes. X-ray diffraction results present that the solid solubility is 10 to 20 wt% and all the sintered samples show a fluorite structure. Raman spectroscopy results show that the order degree of structure decreases as waste content increases. The lattice parameters decrease with the increasing doped waste content indicating the success of waste immobilization. Densities decrease for the sample with higher waste content which mainly caused by the existence of pores. Scanning electron microscope-energy dispersive X-ray spectroscopy and backscattered electron results perform the microstructure of the sintered sample. Furthermore, the leaching test shows that the sample has a considerable chemical stability. This study confirmed the possibility of rapid consolidation of Gd 2 Zr 2 O 7 bulk, dense ceramic with up to 10~20 wt% of immobilized TRPO waste. Highlights• Multi-nuclides waste was rapidly immobilized by Gd 2 Zr 2 O 7 via SPS process.• Phase transition happened with enhanced doping content.• Density results decreased with the higher waste content.• The order degree of structure decreased as waste content increased.• The sintered matrix represented considerable chemical stability. K E Y W O R D S ceramic, Gd 2 Zr 2 O 7 , immobilization, SPS, TRPO waste Ningning He and Guilin Wei contributed equally to this work.

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“…Because of its special advantages [35], SHS technique has been considered as a candidate approach for environment protection, such as stabilization of radioactive and toxic wastes. In recent years, we have explored the rapid synthesis of zirconolite and pyrochlore based waste forms using SHS [36,37,38,39,40,41]. Quick pressing (QP) was also introduced to obtain highly densified samples.…”

Section: Introductionmentioning

confidence: 99%

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms

Zhang

Yin

et al. 2019

Materials

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Synroc is recognized as the second-generation waste matrice for nuclear waste disposal. Zirconolite is one of the most durable Synroc minerals. In this study, Gd and Hf were selected as the surrogates of trivalent and tetravalent actinide nuclides. Gd-bearing Hf-zirconolite (Ca1−xHf1−xGd2xTi2O7) ceramic waste forms were rapidly synthesized from a self-propagating technique using CuO as the oxidant. The results indicate that Gd can concurrently replace the Ca and Hf sites. However, Gd2O3 could not completely be incorporated into the lattice structure of zirconolite when the x value is higher than 0.8. The aqueous durability of selected Gd-Hf codoped sample (Hf-Gd-0.6) was tested, where the 42 days normalized leaching rates (LRi) of Ca, Cu, Gd and Hf are measured to be 1.57, 0.13, 4.72 × 10−7 and 1.59 × 10−8 g·m−2·d−1.

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Self-propagating chemical furnace synthesis of nanograin Gd2Zr2O7 ceramic and its aqueous durability

Cited by 26 publications

References 35 publications

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Effect of improved trialkyl phosphine oxides waste content on phase composition and density of spark plasma sintered Gd ₂ Zr ₂ O ₇ ceramics

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms

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Self-propagating chemical furnace synthesis of nanograin Gd2Zr2O7 ceramic and its aqueous durability

Cited by 26 publications

References 35 publications

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Effect of improved trialkyl phosphine oxides waste content on phase composition and density of spark plasma sintered Gd 2 Zr 2 O 7 ceramics

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms

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Effect of improved trialkyl phosphine oxides waste content on phase composition and density of spark plasma sintered Gd ₂ Zr ₂ O ₇ ceramics