Characterization of rare-earth doped Si3N4/SiC micro/nanocomposites

Influence of various rare-earth oxide additives (La2O3, Nd2O3, Sm2O3, Y2O3, Yb2O3 and Lu2O3) on the mechanical properties of hot-pressed silicon nitride and silicon nitride/silicon carbide micro/nano-composites has been investigated. The bimodal character of microstructures was observed in all studied materials where elongated ?-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements. The fracture toughness of composites was always lower than that of monoliths due to their finer Si3N4/SiC microstructures. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements either in monoliths or composites. On the other hand, the positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element. Significantly improved creep resistance was observed in case either of composite materials or materials with smaller radius of RE3+. .

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Mechanical Properties of α- and β-SiAlON Composite Ceramics Using β-SiAlON Powder

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.403.111 ◽

2008 ◽

Vol 403 ◽

pp. 111-114 ◽

Cited By ~ 1

Author(s):

Kei Asakoshi ◽

Junichi Tatami ◽

Katsutoshi Komeya ◽

Takeshi Meguro ◽

Masahiro Yokouchi

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Rare Earth ◽

Chemical Composition ◽

Metal Oxides ◽

Bending Strength ◽

Rare Earth Oxide ◽

Composite Ceramics ◽

Oxide Powders ◽

Sialon Powder

β-SiAlON powder was used as a raw powder to fabricate α/β-SiAlON composite ceramics with different rare earth elements. The phases present in the sample fabricated from -SiAlON, α-Si3N4, AlN, and rare earth oxide powders were - and -SiAlONs. The composition was dependent on the chemical composition and firing profile. The sample obtained by adding Yb2O3 had a high -SiAlON content. The /-SiAlON composite ceramics had high densit. Their microstructures depended on the used metal oxides, namely, the addition of Nd2O3 and CaCO3 resulted in the elongation of the -SiAlON grains. The bending strength, fracture toughness, and hardness were influenced by the -SiAlON content, amount of elongated grains, and density of the sample.

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Fracture Toughness of Si3N4 Based Ceramics with Rare-Earth Oxide Sintering Additives

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.409.377 ◽

2009 ◽

Vol 409 ◽

pp. 377-381 ◽

Cited By ~ 3

Author(s):

Peter Tatarko ◽

Štefánia Lojanová ◽

Ján Dusza ◽

Pavol Šajgalík

Keyword(s):

Fracture Toughness ◽

Rare Earth ◽

Silicon Nitride ◽

Aspect Ratio ◽

Rare Earth Oxide ◽

Rare Earth Oxides ◽

Crack Deflection ◽

Indentation Fracture ◽

Toughening Mechanisms ◽

Sintering Additives

Fracture toughness of hot-pressed silicon nitride and Si3N4+SiC nanocomposites prepared with different rare-earth oxides (La2O3, Sm2O3, Y2O3, Yb2O3, Lu2O3) sintering additives have been investigated by Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques. The fracture toughness values of composites were lower due to the finer microstructures and the lack of toughening mechanisms. In the Si3N4 with higher aspect ratio (Lu or Yb additives) crack deflection occurred more frequently compared to the Si3N4 doped with La or Y, which was responsible for the higher fracture toughness.

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High-Resolution Interface Atomic Structure Analysis in Silicon Nitride Ceramics

MRS Proceedings ◽

10.1557/proc-839-p2.10 ◽

2004 ◽

Vol 839 ◽

Cited By ~ 1

Author(s):

A. Ziegler ◽

J. C. Idrobo ◽

M. K. Cinibulk ◽

C. Kisielowski ◽

N. D. Browning ◽

...

Keyword(s):

Fracture Toughness ◽

Electronic Structure ◽

Rare Earth ◽

Silicon Nitride ◽

High Resolution ◽

Rare Earth Elements ◽

Structure Analysis ◽

Atomic Structure ◽

Nitride Ceramics ◽

Ionic Size

ABSTRACTIn this study we examine the immediate interface between matrix grains and the amorphous intergranular film in a Si3N4 ceramic doped with rare-earth oxides La2O3, Sm2O3, Er2O3, Yb2O3 and Lu2O3, extracting unique structural and atomic bonding information. In particular, we relate the structure of the interface to the ionic size and electronic structure of the rare-earth elements and the presence of oxygen in the intergranular film. We relate these results to the measured fracture toughness.

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Determination of fracture toughness and elastic module in materials based silicon nitride

Ingeniería Investigación y Tecnología ◽

10.22201/fi.25940732e.2019.20n4.048 ◽

2019 ◽

Vol 20 (4) ◽

pp. 1-13

Author(s):

Edwuin Jesus Carrasquero Rodriguez ◽

Jaime Moises Minchala Marquino ◽

Byron Ramiro Romero Romero ◽

Luis Marcelo Lopez Lopez ◽

Jorge Isaac Fajardo Seminario

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Rare Earth ◽

Silicon Nitride ◽

High Strength ◽

Mechanical Resistance ◽

Elastic Module ◽

Structural Applications ◽

The Matrix ◽

Materials Used

The knowledge of the mechanical properties of any material subjected to loads is necessary for its use in structural applications. Silicon nitride (Si3N4) ceramics are well-known materials used in engineering applications due to their outstanding combination of high strength and fracture toughness. The most studied mechanical properties of Si3N4 are hardness, fracture toughness and mechanical resistance. Recent advances in the production processes that incorporate high purity rare earth elements as sintering additives have improved these mechanical properties. Using Vickers indentation method, the elastic module and fracture toughness of Si3N4 based materials modified with La2O3, Y2O3 and Al2O3 were determined as a function of the cracking system type that prevails under the effect of load. The results indicate that adding rare earth to the matrix increased the fracture toughness the Si3N4 base ceramic Samples containing La2O3+Y2O3 showed higher values of fracture toughness than the ones with Al2O3+La2O3, regardless of the equation used in the calculations. Meanwhile the elastic module decrease approximately 100 GPa for both types of nitrides by the effect of the temperature.

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Effects of Rare-Earth Oxides Doping on Microstructures and Properties of Al2O3/TiAl Composites

Materials Science Forum ◽

10.4028/www.scientific.net/msf.675-677.143 ◽

2011 ◽

Vol 675-677 ◽

pp. 143-146

Author(s):

Fen Wang ◽

Xiao Feng Wang ◽

Jian Feng Zhu ◽

Liu Yi Xiang

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Rare Earth ◽

Flexural Strength ◽

Rare Earth Oxide ◽

Rare Earth Oxides ◽

Oxide Content ◽

The Matrix ◽

Al2o3 Particles ◽

Positive Effect

Effects of rare-earth oxides addition (0.38~1.52 mol% of Sm2O3, Eu2O3 and Er2O3) on the property and microstructure of the hot-pressed (1300°C, 2h, 35 MPa) Al2O3 (12 wt %)/TiAl insitu composites have been investigated. The results show that the doping of rare-earth oxides has a positive effect on both mechanical properties and densities of Al2O3/TiAl composites. Densities enhanced with increasing of rare-earth oxides. The flexural strength and fracture toughness were higher than other samples when the rare-earth oxide content was 0.38 mol %. The matrix grains and Al2O3 particles were significantly refined, and Al2O3 particles evenly distributed in the matrix.

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Development of SiAlON - From Mechanical to Optical Applications

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.352.173 ◽

2007 ◽

Vol 352 ◽

pp. 173-178 ◽

Cited By ~ 12

Author(s):

Tetsuo Yamada ◽

Takeshi Yamao ◽

Shinichi Sakata

Keyword(s):

Rare Earth ◽

Ionic Radius ◽

Bending Strength ◽

Yttrium Aluminum Garnet ◽

Functional Materials ◽

Rare Earth Oxide ◽

Rare Earth Ions ◽

High Temperature Strength ◽

Diverse Range ◽

Rare Earth Doped

Various rare-earth-doped α-SiAlON powders with high purity were prepared to study mechanical and optical properties of SiAlON-based functional materials in connection with ionic radius and electronic structure of rare-earth elements. Single phase rare-earth-doped α-SiAlON powders were obtained at a temperature as low as 1873 K by heating powder mixtures of rare-earth oxide, AlN and highly active ultrafine amorphous Si3N4. Bending strength of highly dense rare-earth-doped α/β-SiAlON-based ceramics was increased with decreasing radii of rare-earth ions, i.e., Yb-SiAlON-based ceramics exhibited excellent high-temperature strength and oxidation resistance caused by the small ionic radius of ytterbium. As for optical application, α-SiAlON is an excellent host lattice with good thermal and chemical stability for doping rare-earth element which activates photoluminescence. Europium-doped Ca-α-SiAlON phosphor formulated as CaxEuy(Si,Al)12(O,N)16 (where 0<x+y<2) was prepared to obtain high quality phosphor with high brightness and desired emission characteristics. Photoluminescence spectra of the resultant Europium-doped Ca-α-SiAlON exhibited high emission intensity at peak wavelength of 580-600 nm giving the better yellow color tone than Cerium-doped yttrium aluminum garnet for applying white LED. It was demonstrated that nitrides or oxynitrides were the innovative materials for the diverse range of high performance specialty applications.

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