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.

Si3N4-BN-SiO2 Based Microwave-Transparent Materials

2008 ◽  
Vol 368-372 ◽  
pp. 913-916 ◽  
Author(s):  
Wei Ru Zhang ◽  
Chong Hai Wang ◽  
Ling Li ◽  
Jian Liu ◽  
Wen Chen
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Technological Parameter ◽  
Bending Strength ◽  
Raw Materials ◽  
Gas Pressure ◽  
Loss Angle ◽  
Transparent Materials ◽  
Gas Pressure Sintering ◽  
N Wave

The Si-B-O-N microwave-transparent materials were prepared by gas pressure sintering (GPS).The effect of BN and nano-SiO2 contents on the mechanical and dielectric properties of the composites was studied. The microstructural characteristic and reinforced mechanism of the composites were also investigated. The results showed that a series of Si-B-O-N wave-transparent materials could be obtained by controlling the contents of raw materials and technological parameter. The bending strength of composites is from 74.7MPa to 174.83MPa, the dielectric constant is from 3.5 to 4.2 and the tangent of loss angle is from 0.5×10-3 to 4.5×10-3.

Microstructure and Properties of 8YSZ with High Component BAS

2014 ◽  
Vol 541-542 ◽  
pp. 25-29
Author(s):  
Jin Qin ◽  
Gang Chen ◽  
Zhi Ming Du ◽  
Jia Hong Niu
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Sintering Temperature ◽  
Sintering Process ◽  
Sintering Aids ◽  
Sintering Time ◽  
Material Component ◽  
Time Density ◽  
Very High

The sintering temperature of 8YSZ (8mol% yttrium stabilized zirconia) is very high, usually above 1500°C. BAS (BaO-Al2O3-SiO2) microcrystalline glass can be used as sintering aids to reduce the sintering temperature of 8YSZ. In this research, large proportion (30-50wt%) BAS was added in 8YSZ to observe the influence of the sintering aids. The change rules of mechanical properties such as density test, bending strength and toughness in different material component and sintering process were researched. The results show that physical and mechanical performance improvement with the increase of sintering temperature and sintering time, density and bending strength decreases with the increase of BAS mass fraction. The optimal mechanical properties are obtained by sintering temperature 1300°C, sintering time 0.5h and 30wt% BAS.

Defects Analysis of Large Size Silicon Nitride Balls Sintered by Gas Pressure Sintering

2010 ◽  
Vol 434-435 ◽  
pp. 61-63
Author(s):  
Feng Sun ◽  
Wei Ru Zhang ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Temperature Gradient ◽  
Raw Materials ◽  
Gas Pressure ◽  
Sintering Process ◽  
The Core ◽  
Large Size ◽  
Defects Analysis ◽  
Gas Pressure Sintering

The sections of Φ55mm silicon nitride balls, sintered by gas pressure sintering were analyzed. The results show that temperature gradient during of the sintering process from the surface to the core of large size silicon nitride balls occurred because of the lower thermal conductivity of Si3N4. With the diameter increasing, the temperature gradient was more visible. The impurity of raw materials, such as free Si, free C and other metal oxides, like the SiO2 could produce gas, such as SiO, CO and so on, during the sintering process through the thermodynamic analysis. The producing gas exhausted more difficultly with the diameter of silicon nitride balls increasing. These factors were the most important to the defects of large size silicon nitride balls during the sintering process and made cracks and crescent on the surface of balls.

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.

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.

Sinterability of Silicon Nitride Powder Produced by the CRN Process

2009 ◽  
Vol 147-149 ◽  
pp. 896-901
Author(s):  
Ahmet Atasoy ◽  
M. Tümer
Keyword(s):  
Liquid Phase ◽  
Laboratory Experiments ◽  
Graphite Crucible ◽  
Nitride Powder ◽  
Sintering Process ◽  
Sintering Aids ◽  
X Ray ◽  
Liquid Phases ◽  
Linear Relationships ◽  
Silicon Nitride Powder

In the present work, laboratory experiments were carried out on the sintering of silicone nitride powder without any sintering additives. Silicone nitride powder was produced at own laboratory conditions by carbothermal reduction-nitriding of silica of which was presented elsewhere. It consists of mainly -Si3N4 (83%) and -Si3N4 (17%) phases with a small amount of minor constituents. Before compaction procedure, the powder was ball milled for 2 h and then 2 gr. of the sample was compacted uniaxially at a pressure of 25 MPa. The green compact was placed into furnace in a graphite crucible. The sintering process was carried out in a programmable muffle furnace at 1700 °C and held for 1 h. with a 20 °C/min. heating rate. The sintered compacts were analyzed using X-ray, SEM, SEM-EDS techniques. The results showed that the formation of liquid phase can accelerate the densification of the compact. The densification of the pure SIALON can be increased by adding of sintering aids that accelerates the formation of liquid phases in the sample. The densified sialons give better hardness and thermal properties of the sample. It was well demonstrated that for the densification of sialons large amount of liquid phase forming oxides are needed to add to initial composition. It is also suggested that there is linear relationships between densification and amount of liquid phase formed in the compact.

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