Si_3N_4反応焼結体の熱伝導率

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To investigate the effect of α- and β-Si_3N_4 content on the thermal conductivity of silicon nitride ceramics, six samples containing various quantities of α-Si_3N_4 were prepared by the reaction bonding process and the thermal conductivity of the reaction bonded Si_3N_4 (RBSN) was measured by the transient hot wire method at various temperatures from room temperature to 1000℃. The RBSN samples containing 1, 25, 33, 45, 55 and 66% α-Si_3N_4 were produced by intruding the compacts of pure silicon powder in a nitrogen atmosphere at 1480℃ for prescribed periods. Bulk density, true density and total porosity of samples were 2.51±0.02g/cm^3,3.08±0.03g/cm^3 and 18.6±1.0%, respectively. regardless of the α-content. No significant change in microstructure of RBSN samples was observed by scanning electron microscopy. With an increase in the content of α-Si_3Na_4 the thermal conductivity (λ) of BRSN samples decreased from λ=17.4 Wm^<-1> K^<-1> for the sample with α-Si_3N_4 of 1% (viz. consisted mainly of β-Si_3N_4) to λ=9.3 Wm^<-1> K^<-1> for that of 66%. It was considered that the α-Si_3N_4 solid solutions by which the thermoplastic wave carrying the heat energy in the non-electro-conductive solid materials such as Si_3N_4 ceramics is scattered, might be formed with the impurities included in silicon powder as a starting material. The thermal conductivity of all RBSN samples decreased simply with increasing temperature due to the increase of the mutual scattering of the thermo-elastic wave, and the decreasing rate of thermal conductivity for the RBSN with lower α-contents was found to be larger than that for those with higher α-contents.
社団法人日本セラミックス協会の論文
1986-06-01

Si_3N_4反応焼結体の熱伝導率

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