Silicon Nitride Containing Rare Earth Silicate Intergranular Phases

1992 ◽  
Vol 287 ◽  
Author(s):  
Stephen D. Nunn ◽  
Terry N. Tiegs ◽  
Kristin L. Ploetz ◽  
Claudia A. Walls ◽  
Nelson Bell
Keyword(s):  
Rare Earth ◽  
Ternary Phase ◽  
Gas Pressure ◽  
Trivalent Cation ◽  
Processing Conditions ◽  
Microstructure Development ◽  
Sintering Aids ◽  
Conventional Sintering ◽  
Compositional Variations ◽  
Gas Pressure Sintering

ABSTRACTSi3N4 ceramics prepared with refractory grain boundary phases to improve high temperature properties are difficult to densify by conventional sintering methods. Gas-pressure sintering may be used to promote densification and development of acicular grains for improved fracture toughness. The current study examined rare earth silicate sintering aids with the composition M2Si2O7, where M is a trivalent cation (Y, La, Nd). M2O3 and Si02 additions were varied to develop a number of compositions in the Si3N4—Si2N2O—M2Si2O7 ternary phase field. Pressureless sintering and gas-pressure sintering were used to densify the samples. Densification, microstructure development, oxidation resistance, and mechanical properties were evaluated and compared with respect to compositional variations and processing conditions.

Effect of B4C Content on Densification Behavior of SiC-B4C Ceramics

2014 ◽  
Vol 997 ◽  
pp. 454-456
Author(s):  
Yun Long Zhang ◽  
Yu Min Zhang ◽  
Ming Hu ◽  
Xiao Gang Song
Keyword(s):  
Rare Earth ◽  
Rare Earth Oxide ◽  
Gas Pressure ◽  
Volume Shrinkage ◽  
Densification Behavior ◽  
Sintering Aids ◽  
Phase Constitution ◽  
Sintering Additives ◽  
Multi Phase ◽  
Gas Pressure Sintering

The SiC-B4C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al2O3combined with Er2O3/SiO2was served as sintering aids. The results were shown that the combination of Al2O3/Er2O3/SiO2sintering additives were effective for densification of SiC-B4C multi-phase ceramics. The influence of B4C content on the phase constitution, microstructure and densification behavior of the SiC-B4C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B4C multi-phase ceramics had similar evolvement trend when B4C content increased. Keywords: Gas-Pressure Sintering, SiC-B4C multi-phase ceramics, densification behavior.

Effect of Powder Characteristics on Gas-Pressure Sintering of Si3N4 With Rare Earth Additives

1994 ◽  
pp. 871-874
Author(s):  
T.N. Tiegs ◽  
S.D. Nunn ◽  
C.A. Walls ◽  
D. Barker ◽  
C. Davisson ◽  
...  
Keyword(s):  
Rare Earth ◽  
Gas Pressure ◽  
Powder Characteristics ◽  
Gas Pressure Sintering

scholarly journals Sintering of Hydroxyapatite/Yttria Stabilized Zirconia Nanocomposites under Nitrogen Gas for Dental Materials

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
C. H. Leong ◽  
A. Muchtar ◽  
C. Y. Tan ◽  
M. Razali ◽  
Noor Faeizah Amat
Keyword(s):  
Relative Density ◽  
Phase Stability ◽  
Dental Materials ◽  
Gas Pressure ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Nitrogen Gas ◽  
Conventional Sintering ◽  
Gas Pressure Sintering ◽  
The Relationship

This study aims to determine the effect of adding 3 mol% yttria stabilized zirconia (3YSZ) in hydroxyapatite (HA) and sintering HA/3YSZ nanocomposites under nitrogen gas on HA decomposition. This paper presents the relationship between microstructure and mechanical properties of HA/3YSZ nanocomposites. Gas pressure and conventional sintering were performed on HA/3YSZ nanocomposites containing different amounts of 3YSZ (i.e., 0, 0.5, 1, and 7 wt%) at 1250°C. The phase stability, morphology, relative density, and microhardness of the HA/3YSZ nanocomposites were investigated. The phase stability of the HA/3YSZ nanocomposites was affected by adding different amounts of 3YSZ. Overall, gas pressure sintering leads to the formation of greater grain size compared with the conventional sintering method. The severe HA decomposition and the presence of the porosity in HA/7 wt% 3YSZ have led to deterioration in relative density and microhardness. In this study, HA/0.5 wt% 3YSZ with gas pressure sintering exhibited the optimum microstructure with the highest relative density (97%) and microhardness (3.93 GPa).

Influence of YAG-Based Composite Sintering Aids on Gas Pressure Sintered BNw/Si3N4 Composites

2015 ◽  
Vol 655 ◽  
pp. 53-57
Author(s):  
Xian Li Wang ◽  
Hong Yu Gong ◽  
Yu Jun Zhang ◽  
Song Wei Che
Keyword(s):  
Dielectric Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Gas Pressure ◽  
Apparent Porosity ◽  
Sintering Process ◽  
Sintering Aids ◽  
Liquid Phases ◽  
Gas Pressure Sintering

BNw/Si3N4composites were fabricated by gas pressure sintering process using α-Si3N4powder and self-made BN whisker as principal raw materials. The effects of different sintering additives such as YAG, MgO+YAG and RE2O3+YAG(RE=La, Sm, Dy) on the apparent porosity, microstructure, phase composition, mechanical performance and dielectric properties of the composites were analysed. The results revealed that composite sintering aids at certain ratio (MgO/RE2O3:YAG=1:5) was more conducive to ceramic densification than single YAG additive. The BNw/Si3N4sintered with La2O3+YAG acquired the highest density and the maximum bending strength (272.46 MPa) and fracture toughness(4.9 MPa·m1/2). It was speculated that ceramic densification process was related to formation of different eutectic liquid phases with different viscosity. Additionally, when the apparent porosity of BNw/Si3N4composites was 20% or less, dielectric properties of the material were mainly influenced by the porosity and the value of the permittivity and dielectric loss decreased with the increase of ceramic porosity.

Development of α-β SiAlON Ceramics from Different Si3N4 Starting Powders

2008 ◽  
Vol 403 ◽  
pp. 107-108 ◽  
Author(s):  
Nurcan Calis Acikbas ◽  
Ferhat Kara ◽  
Hasan Mandal
Keyword(s):  
Fracture Toughness ◽  
Process Parameters ◽  
Gas Pressure ◽  
Economic Viability ◽  
Si3n4 Powder ◽  
Gas Pressure Sintering

- SiAlON ceramics were produced from different starting Si3N4 powders including β-Si3N4 and α-Si3N4 powders and mixtures of these powders. Gas pressure sintering was used for sintering. After sintering, resultant fracture toughness values were correlated with microstructure and starting powders. By optimizing chemistry and process parameters; - SiAlON ceramics with reasonable fracture toughness can be produced from rather coarse β-Si3N4 powder. This could improve the economic viability of SiAlON ceramics since -Si3N4 powders are less costly.

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