Sintering Behavior of Simulating Core FCM Fuel via Hot Oscillatory Pressing
Fully ceramic micro-encapsulated(FCM)fuel has become the focus of nuclear energy research because of its good inherent safety.In order to overcome the difficulty of SiC matrix densification,this study focused on the sintering behavior of simulating core FCM fuel via hot oscillatory pressing(HOP),taking the advantages of HOP to accelerate mass transfer and reduce sintering temperature.The influence of oscillatory sintering temperature,oscillatory time and oscillatory pressure on the matrix densification behavior was studied,and the results were compared with those of hot pressing(HP).The results indicate that the oscillatory sintering temperature,holding time,and median pressure have important effects on matrix densification,while the amplitude of oscillatory pressure has little effect.Compared with HP,the density of the samples is increased by HOP,and the density of sample sintered at 1850 ℃ via HOP is 99.99％.The grain size of the samples via HOP is smaller,and the grain size of the sample sintered via HOP at 1850 ℃ is(284±4)nm,which is～27％less than that of the sample sintered via HP at the same temperature.The hardness of the samples sintered via HOP is higher,and the hardness of the sample sintered via HOP at 1850 ℃ is(26.7±0.4)GPa.When the density of sample is 90％,the stress exponent n=1 and activation energyQ=430 kJ/mol are obtained by using the modified constitutive equation of HP.The dominant mechanism of densification is grain boundary sliding,which is accommodated by the grain boundary diffusion.
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