Silicon Nitride Ceramics with Sodium Ion Conductive Grain Boundary Phase

2003 ◽  
Vol 18 (12) ◽  
pp. 2752-2755 ◽  
Author(s):  
Hirokazu Kawaoka ◽  
Tohru Sekino ◽  
Takafumi Kusunose ◽  
Koichi Niihara
Keyword(s):  
Electrical Conductivity ◽  
Silicon Nitride ◽  
Ionic Conductivity ◽  
Grain Boundary ◽  
Sodium Ion ◽  
Boundary Phase ◽  
Structural Ceramics ◽  
Silicon Nitride Ceramic ◽  
Nitride Ceramics ◽  
Conductive Particles

Sodium ion-conductive silicon nitride ceramic with Na2O–Al2O3–SiO2 glass as the grain boundary phase was fabricated by adding Na2CO3, Al2O3, and SiO2 as sintering additives. The electrical conductivity was two and four orders of magnitude higher than that of Si3N4 ceramic with Y2O3 and Al2O3 additives at 100 and 1000°C, respectively. This result clearly indicates that ionic conductivity can be provided to insulating structural ceramics by modification of the grain boundary phase without dispersion of conductive particles.

Microstructure and microanalysis of silicon nitride ceramics in the Y-Si-Al-O-N and Y-Si-O-N systems

1990 ◽  
Vol 48 (4) ◽  
pp. 1072-1073
Author(s):  
Michael K. Cinibulk
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Liquid Phase Sintering ◽  
Boundary Phase ◽  
Full Density ◽  
High Temperature Strength ◽  
Transmission Electron ◽  
Structural Applications ◽  
Nitride Ceramics

Silicon nitride ceramics are among the leading candidate materials for use in structural applications at high temperatures. Due to the highly covalent nature of the Si-N bond and therefore low self-diffusivity, processing Si3N4 to full density requires the use of additives to provide a medium for liquid-phase sintering. When exposed to temperatures above ∼1000°C the resulting amorphous grain-boundary phases soften, leading to grain-boundary sliding and the eventual failure of the ceramic. The objectives of this work were to modify the grain-boundary phase composition and then attempt to devitrify the resulting intergranular phase to a refractory crystalline phase, producing a sintered Si3N4 with improved high-temperature strength and oxidation resistance. Transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDS) were used to characterize these materials. This paper describes these results.

Fabrication of Silicon Nitride Ceramics with Electrical Conductivity

2005 ◽  
Vol 486-487 ◽  
pp. 501-505 ◽  
Author(s):  
Yoon Ho Kim ◽  
Tohru Sekino ◽  
Hirokazu Kawaoka ◽  
Takafumi Kusunose ◽  
Tadachika Nakayama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Phase ◽  
Si3n4 Ceramic ◽  
Nitride Ceramics ◽  
Infinite Network ◽  
Fine Microstructure ◽  
Si3n4 Ceramics

The electrical conductivity was provided to structural ceramics by controlling the grain boundary phase. We focused on the grain boundary phase of Si3N4 ceramics, which can be considered as an infinite network for conducting paths. In this study, we investigated the correlationship of the microstructure, mechanical properties, and electrical conductivity of Si3N4 ceramics with V2O5 based glasses. The Si3N4 ceramic with V2O5 based glasses were successfully fabricated by controlling the composition of grain boundary phase. Fabricated materials by a PECS method indicated a very fine microstructure. The mechanical properties of Si3N4 ceramics with V2O5 based glasses were not good compared to those of conventional Si3N4. However, the values for the SNVB and the SNVBA were four or six orders of magnitude higher at room temperature and had excellent mechanical properties compared to pure V2O5 based glasses.

The Influence of Corrosion in an Aqueous Solution of NaCl on Fracture and Strength of Various Structural Ceramics

2009 ◽  
Vol 409 ◽  
pp. 260-266 ◽  
Author(s):  
Dagmar Galusková ◽  
Monika Kašiarová ◽  
Miroslav Hnatko ◽  
Dušan Galusek ◽  
Pavol Šajgalík ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Sodium Chloride ◽  
Liquid Phase ◽  
Grain Boundary ◽  
Fracture Strength ◽  
Amorphous Film ◽  
Boundary Phase ◽  
Distilled Water ◽  
Structural Ceramics ◽  
Polycrystalline Alumina

The present work studies the corrosion of three most widely used types of structural ceramics – silicon nitride, solid state sintered alumina and liquid phase sintered alumina – in 3 % aqueous solutions of sodium chloride at temperatures up to 290 °C and pressures up to 7 MPa. The corrosion of silicon nitride was controlled by attack of Si3N4 matrix grains, while yttrium oxynitride amorphous grain boundary phase was corrosion resistant. Corrosion of Si3N4 in reference media -distilled water - at 290 °C was characteristic by formation of passivation layer, which hindered further dissolution of silicon nitride matrix. The presence of sodium chloride resulted in formation of discontinuous layer of corrosion products, resulting in more severe corrosion than in distilled water. The corrosion of liquid phase sintered alumina was mainly attributed to congruent dissolution of SiO2 and CaO from grain-boundary amorphous film, which was accelerated at higher temperature, and accompanied by precipitation of siliceous phases from oversaturated solution at 200 °C. Pure polycrystalline alumina corroded by loss of alumina grains, which did not dissolve in the corrosion media. The corrosion impaired significantly the fracture strength of silicon nitride, creating new, corrosion related defects at the surface, while the influence of corrosion on fracture strength of polycrystalline aluminas was negligible.

Effect of Grain Boundary Phase on Contact Damage Resistance of Silicon Nitride Ceramics

2005 ◽  
Vol 287 ◽  
pp. 421-426 ◽  
Author(s):  
Chul Seung Lee ◽  
Kee Sung Lee ◽  
Shi Woo Lee ◽  
Do Kyung Kim
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Grain Morphology ◽  
Boundary Phase ◽  
Contact Damage ◽  
Damage Resistance ◽  
Intergranular Phase ◽  
Nitride Ceramics ◽  
Damage Response ◽  
Different Types

Contact damage resistances of silicon nitride ceramics with various grain boundary phases are investigated in this study. The grain boundary phases are controlled by the addition of different types of sintering additives, or the crystallization of intergranular phase in a silicon nitride. We control the microstructures of materials to have similar grain sizes and the same phases to each other. Contact testing with spherical indenters is used to characterize the damage response. The implication is that the grain boundary phase can be another controllable factor against contact damage and strength degradation even though it is not critical relative to the effect of grain morphology.

Effect of Oxynitride Grain Boundary Phase on Toughening of Silicon Nitride Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 649-652 ◽  
Author(s):  
Takafumi Kusunose ◽  
Tohru Sekino ◽  
P.E.D. Mogan ◽  
Koichi Niihara
Keyword(s):  
Fracture Toughness ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Propagation ◽  
Hot Pressing ◽  
Boundary Phase ◽  
Toughening Mechanism ◽  
Nitride Ceramics

The Si3N4/YSiO2N composite in which crystalline YSiO2N was formed as grain boundary phase was fabricated by hot-pressing the mixture of SiO2, Si3N4 and Y2O3. The fracture toughness of this composite was significantly improved, compared to the Si3N4 composites containing Y5Si3O12N or Y2Si3O3N4 as a grain boundary phases. To clarify the toughening mechanism, the microstructure and the crack propagation profiles were observed.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Effect of rare-earth species on the wear properties of α sialon and β silicon nitride ceramics under tribochemical type conditions

2004 ◽  
Vol 19 (9) ◽  
pp. 2750-2758 ◽  
Author(s):  
Mark I. Jones ◽  
Kiyoshi Hirao ◽  
Hideki Hyuga ◽  
Yukihiko Yamauchi
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Wear Behavior ◽  
Rare Earth Oxide ◽  
Lower Amount ◽  
Boundary Phase ◽  
Wear Properties ◽  
Sintering Additives ◽  
Nitride Ceramics ◽  
Worn Surfaces

The wear properties under low loads of β Si3N4 and α sialon materials sintered with different rare-earth oxide sintering additives have been studied under dry sliding conditions using block-on-ring wear tests. All the worn surfaces showed an absence of fracture and smooth surfaces with the presence of an oxygen-rich filmlike debris indicating tribochemically induced oxidation of the surfaces. Extensive grain boundary removal was observed on the worn surfaces thought to be due to adhesion between this silicate phase and the tribochemically oxidized surfaces. The resistance to such oxidation and the properties of the residual grain boundary phase are thought to be important parameters affecting the wear behavior under the present testing conditions. For both the β Si3N4 and α sialon materials, there was an increase in wear resistance with decreasing cationic radius of the rare earth, thought to be due to improved oxidation resistance, and this was more remarkable in the case of the sialon materials where the incorporation of the sintering additives into the Si3N4 structure results in a lower amount of residual boundary phase.

Sign in / Sign up

Export Citation Format

Share Document