Fabrication and Properties of Si3N4 with Rare Earth Apatite Grain Boundary Phases

1992 ◽  
Vol 287 ◽  
Author(s):  
Terry N. Tiegs ◽  
Stephen D. Nunn ◽  
Kristin L. Ploetz ◽  
Paul A. Menchoffer ◽  
Claudia A. Walls
Keyword(s):  
Rare Earth ◽  
Silicon Nitride ◽  
Grain Boundary ◽  
Ambient Temperature ◽  
Rare Earth Oxide ◽  
High Toughness ◽  
The Rare Earth

ABSTRACTThe rare earth-oxide and nitride apatites were examined as grain boundary phases in silicon nitride to assess their potential for developing high toughness materials using gas-pressuresintering. Densification was dependent on the quantity of additives used with high densities achieved at equivalent oxygen contents of ∼8%. Fracture toughnesses (KIc) up to 8-10 MPa√m were obtained for some compositions. Ambient temperature flexural strengths were in the range of 400-720 MPa; however, the strengths atelevated temperatures (1200ºC) were reduced from these values.

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.

ChemInform Abstract: Hot Pressing of Silicon Nitride with Mixed Rare-Earth Oxide Additives

ChemInform ◽  
1988 ◽  
Vol 19 (33) ◽  
Author(s):  
E. RAPOPORT ◽  
C. BRODHAG ◽  
F. THEVENOT
Keyword(s):  
Rare Earth ◽  
Silicon Nitride ◽  
Hot Pressing ◽  
Rare Earth Oxide

Thermal Evolution and Electrical Properties of Rare-Earth Oxide Doped Zirconia

1988 ◽  
Vol 121 ◽  
Author(s):  
B. S. Chiou ◽  
M. Y. Lee ◽  
J. G. Duh
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Ionic Radius ◽  
Thermal Evolution ◽  
Rare Earth Oxide ◽  
Zirconia Ceramics ◽  
Wet Chemical ◽  
Ir Analysis ◽  
Lower Temperature ◽  
The Rare Earth

ABSTRACTSynthesized zirconia ceramics are prepared through the coprecipita-tion process. Application of the wet chemical approach is aimed at the achievement of highly sintered ceramics at lower temperature. The thermal evolution of the synthesized CeO2-ZrO2 powder is investigated with the aid of DTA and TGA measurement. The exothermic peaks on the DTA thermogram are futher identified by the IR analysis. The effect of CeO on the occurrence of the peaks is probed. For other rare-earth oxiae doped ceramics, such as Nd2O3. and Dy2O3. containing zirconia, the bulk and grain boundary resistances are evaluated by the impedance spectroscopy. The dependence of the associated activation energy in the rare-earth oxide doped zirconia is discussed with respect to the variation of the ionic radius of the rare earth constituent.

The effect of rare-earth oxide addition on the hot-pressing of magnesium silicon nitride

2002 ◽  
Vol 22 (5) ◽  
pp. 777-783 ◽  
Author(s):  
Shukiko Tanaka ◽  
Kiyoshi Itatani ◽  
Hiroshi Uchida ◽  
Mamoru Aizawa ◽  
Ian J Davies ◽  
...  
Keyword(s):  
Rare Earth ◽  
Silicon Nitride ◽  
Hot Pressing ◽  
Rare Earth Oxide ◽  
Oxide Addition

Nano Crystallite ZrO2, La2O3 and CeO2: Synthesis, Characterization and their Properties

2013 ◽  
Vol 209 ◽  
pp. 212-215
Author(s):  
A.K. Patel ◽  
A.R. Umatt ◽  
B.S. Chakrabarty
Keyword(s):  
Rare Earth ◽  
Surface Area ◽  
Gas Adsorption ◽  
Chemical Properties ◽  
Rare Earth Oxide ◽  
Combustion Method ◽  
Rare Earth Oxides ◽  
Precipitation Method ◽  
Reaction Conditions ◽  
The Rare Earth

It is well known that a minor addition of rare earth oxides can provide a beneficial effect towards various catalytic reactions. Use of rare earth oxide in different applications could improve commercial productivity in an affordable way. Among the rare earth oxides, ZrO2, La2O3 and CeO2 are very interesting due to their various characteristics showing a large range of applications in organic reactions. The changes in the molecular properties of materials at the nano scale level greatly enhance their physical properties as well as chemical properties and activity. Due to the extremely small size of the particles, an increased surface area is provided to the reactant enabling more molecules to react at the same time, thereby speeding up the process. In this work, the enhancement in the catalytic activity of these nano structured rare earth oxides has been studied under different reaction conditions. Nano crystalline ZrO2, La2O3 and CeO2 samples were synthesized using precipitation method and optimum reaction conditions have been established; whereas the corresponding bulk samples were synthesized by combustion method. The identification of phase and crystalline size of synthesized oxides have been done by X-ray diffraction, the band gape of these three oxides in both the forms has been analyzed by UV absorbance and surface area has been determined by gas adsorption analysis (BET). Moreover their different properties and the activity of nano crystallite oxides have also been compared with their bulk counterparts. Even the activity of ZrO2 is also compared with the rare earth oxides La2O3 and CeO2.

Pressure Dependence of the Resistivity of the Rare Earth Oxide Nitrides Eu1−x2+Lnx3+NxO1−x (Ln = Nd, Eu)

1979 ◽  
Vol 93 (1) ◽  
pp. K63-K66 ◽  
Author(s):  
B. Chevalier ◽  
G. Demazeau ◽  
J. Etourneau ◽  
P. Hagenmuller
Keyword(s):  
Rare Earth ◽  
Pressure Dependence ◽  
Rare Earth Oxide ◽  
The Rare Earth
Sign in / Sign up

Export Citation Format

Share Document