Cold Sintering of Na2WO4 Ceramics using a Na2WO4-2H2O Chemistry

Hao, Jianyu; Guo, Jing; Ma, Chuansheng; Yao, Fang‐Zhou; Yao, Bin; Si, Mingming; Zhao, Enda; Wang, Hong

doi:10.1016/j.jeurceramsoc.2021.05.019

Cited by 7 publications

(12 citation statements)

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“…As the sintering temperature goes up to 100–120°C, the amount of large grains is gradually reduced, and some needle or flake grains appear especially at 120°C, which is caused by the decomposition of Na 2 WO 4 ·2H 2 O into Na 2 WO 4 and water. For the sintering temperature at 140–180°C, small quasi‐polygonal grains are manifested, which belong to the Na 2 WO 4 phase and are similar to the microstructures of cold‐sintered Na 2 WO 4 samples using water as the mediated liquid phase in the previous work 28 . It is also seen that with higher sintering temperatures, small acicular grains appear at the grain boundaries, especially at 180°C.…”

Section: Resultssupporting

confidence: 80%

“…A certain sintering temperature is essentially required to drive the liquid phase to diffuse and volatilize in CSP. Our previous work has demonstrated that 120°C is needed in the cold sintering of Na 2 WO 4 ceramics using deionized water as the mediate liquid phase 28 . As for the cold sintering of Na 2 WO 4 ceramics using Na 2 WO 4 ·2H 2 O dry powders, the densification process at different sintering temperatures is shown in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

“…Liquid phase is the fundamental factor in controlling the CSP of Na 2 WO 4 ceramics, which has been studied in the previous work 28 . Here, the raw material of Na 2 WO 4 ·2H 2 O hydrate is used to cold sinter Na 2 WO 4 ceramics without adding liquid phase, which has the advantage of dispersing water evenly for CSP, as shown in Figure 10A.…”

Section: Resultsmentioning

confidence: 99%

“…Na 2 WO 4 , an excellent microwave dielectric ceramic, that has been obtained by CSP in our previous work using Na 2 WO 4 powders and deionized water 27,28 . Its sintering mechanism mainly depends on the “dissolution–precipitation” process that is slightly different from the traditional “dissolution–precipitation” process, which is accompanied by the crystallization and dehydration of Na 2 WO 4 with water, as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Na 2 WO 4 , an excellent microwave dielectric ceramic, that has been obtained by CSP in our previous work using Na 2 WO 4 powders and deionized water. 27,28 Its sintering mechanism mainly depends on the "dissolutionprecipitation" process that is slightly different from the traditional "dissolution-precipitation" process, which is accompanied by the crystallization and dehydration of Na 2 WO 4 with water, as shown in Figure 1. It is seen that Na 2 WO 4 ⋅2H 2 O hydrate plays a critical role in the densification of Na 2 WO 4 ceramics, which inspires us to cold sinter Na 2 WO 4 ceramics using only Na 2 WO 4 ⋅2H 2 O dry powders without any added liquid water.…”

Section: Introductionmentioning

confidence: 99%

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The effects of cold sintering parameters on the densification of Na₂WO₄ ceramics using Na₂WO₄·2H₂O dry powders

Hao

Guo

et al. 2022

J Am Ceram Soc.

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Cold sintering process (CSP) combines transient liquid phase and/or external pressure to assist the densification of ceramics, the sintering mechanism of which is typically dominated by the “dissolution–precipitation” process. In this work, Na2WO4·2H2O dry powders without liquid water have been used as the “liquid phase” to realize the densification of Na2WO4 ceramics. The effects of sintering parameters on the CSP of Na2WO4 ceramics using Na2WO4·2H2O dry powders are systematically studied, including sintering temperature, external pressure, sintering process time and the amount of Na2WO4·2H2O phase. It is found that the “liquid phase,” that is, Na2WO4·2H2O is the key factor for controlling the CSP of Na2WO4 ceramics, and Na2WO4·2H2O hydrate shows an advantage of homogeneous dispersion of liquid water. The sintering temperature affects the densification mechanism involved with plastic deformation and the “dissolution–precipitation,” external pressure accelerates the densification process, and enough sintering process time ensures the completion of CSP. Finally, the optimum cold sintering parameters of Na2WO4 ceramics by Na2WO4·2H2O powders are obtained at 150°C and 240 MPa for 60 min with a pretreatment at 150°C for 30 min.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations