Hierarchical Structure of Porous Silicon Nitride Ceramics with Aligned Pore Channels Prepared by Ice-Templating and Nitridation of Silicon Powder

This paper presents the microwave dielectric property of porous silicon nitride ceramics at a frequency of 9360 MHz, which were fabricated by the nitridation of silicon powder. The porous ceramics with different volume fraction of porosity from 18.6% to 56.2% were produced by adding different amount of the pore-forming agent into the initial silicon powder. Microstructural analysis revealed a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing in it. The results showed that the dielectric constant of the ceramics reduces with the porosity increases. With the addition of α-Si3N4 powder in the raw silicon powder, the nitridation rate is raised, and the dielectric constant and the dielectric loss of the ceramics decrease notablely.

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Characterization of porous silicon nitride ceramics using bentonite as binder and sintering additive

Materials Characterization ◽

10.1016/j.matchar.2008.11.016 ◽

2009 ◽

Vol 60 (5) ◽

pp. 456-460 ◽

Cited By ~ 7

Author(s):

Guang-Peng Jiang ◽

Jian-Feng Yang ◽

Ji-Qiang Gao ◽

Koichi Niihara

Keyword(s):

Silicon Nitride ◽

Porous Silicon ◽

Sintering Additive ◽

Nitride Ceramics

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Effects of Sintering Additives on the Microstructure and Mechanical Properties of Silicon Nitride Ceramics by GPS

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.105-106.27 ◽

2010 ◽

Vol 105-106 ◽

pp. 27-30 ◽

Cited By ~ 2

Author(s):

Wei Ru Zhang ◽

Feng Sun ◽

Ting Yan Tian ◽

Xiang Hong Teng ◽

Min Chao Ru ◽

...

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Phase Transformation ◽

Silicon Nitride ◽

Porous Silicon ◽

Flexural Strength ◽

Relative Density ◽

Sintering Additives ◽

Microstructure And Mechanical Properties ◽

Nitride Ceramics

Silicon nitride ceramics were prepared by gas pressure sintering (GPS) with different sintering additives, including La2O3, Sm2O3 and Al2O3. Effect of sintering additives on the phase-transformation, microstructure and mechanical properties of porous silicon nitride ceramics was investigated. The results show that the reaction of sintering additives each other and with SiO2 had key effects on the phase-transformation, grain growing and grain boundaries. With 9MPa N2 atmosphere pressure, holding 1h at 1850°C, adding 10wt% one of the La2O3, Sm2O3, Al2O3, porous silicon nitride was prepared and the relative density was 78%, 72%, 85% respectively. The flexural strength was less than 500MPa, and the fracture toughness was less than 4.8MPam1/2. Dropping compounds sintering additives, such as La2O3+Al2O3, Sm2O3+Al2O3 effectively improves the sintering and mechanical properties. The relative density was 99.2% and 98.7% with 10wt% compounds sintering additives. The grain ratio of length to diameter was up to 1:8. The flexural strength was more than 900MPa, and the fracture toughness was more than 8.9MPam1/2.

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