Effect of the Grain Boundary Thermal Expansion Coefficient on the Fracture Toughness in Silicon Nitride

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65261/1/j.1151-2916.1995.tb08667.x.pd

Subsolidus Phase Relations in Part of the System Si,Al,Y/N,O

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65882/1/j.1151-2916.1979.tb12762.x.pd

Phase Stability and Physical Properties of Cubic and Tetragonal ZrO 2 in the System ZrO 2 –Y 2 O 3 –Ta 2 O 5

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65531/1/j.1151-2916.1991.tb04302.x.pd

Solubility Limits of Α'-SiAION Solid Solutions in the System Si,Al,Y/N,O

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66438/1/j.1151-2916.1991.tb06797.x.pd

The System Si 3 N 4 -SiO 2 -Y 2 O 3

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65627/1/j.1151-2916.1980.tb10644.x.pd

Reply to “Comment on ‘Morphology of Silicon Nitride Grown from a Liquid Phase’”

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65586/1/j.1151-2916.2000.tb01257.x.pd

Effect of Crystallization of the Grain-Boundary Phase on the Thermal Diffusivity of a Sialon Ceramic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65865/1/j.1151-2916.1984.tb19519.x.pd

Small-polaron mobility in nonstoichiometric cerium dioxide

The high temperature drift mobility ([mu]d) of charge carriers in nonstoichiometric cerium dioxide (CeO2-x) has been calculated by combining the electrical conductivity and nonstoichiometry data on the basis of the oxygen vacancy model with correct ionization state. The electrical conductivity was measured by a four-probe d.c. technique and the nonstoichiometry by thermogravimetric analysis. The dilute solution model of the point defects is valid up to x = 0.03. From the magnitude of [mu]d and its temperature dependence, the charge carriers in CeO2-x, are proposed to be small-polarons formed by localization of electrons at cerium sites and the charge transport process is proposed to occur by a hopping mechanism. The observed temperature dependence of [mu]d is in accord with that derived by Holstein and Friedman for small-polaron transport by the hopping mechanism. The activation energy of mobility is found to increase with increasing x as expected for the hopping model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22734/1/0000289.pd

Effect of AlN and Al2O3 additions on the phase relationships and morphology of SiC Part I Compositions and properties

X-ray diffraction was utilized to follow the transformation from β-SiC (3C) to the various α-SiC polytypes in the presence of AlN and Al 2 O 3 additives after hot pressing from 1700 to 2100°C. The 2H- and 6H-polytypes of α-SiC were the predominate polytypes with additions of only AlN or Al 2 O 3 , respectively. The amount of 2H- and 6H-polytypes, and subsequently the microstructural morphology of the SiC materials, were found to be controlled by varying the amount of AlN and Al 2 O 3 . Improvements in fracture toughness to ∼9 MPa-√m were achieved with flexural strengths ranging from 600 to 900 MPa. These results suggest that accurate control of the polytypic make-up of SiC-based materials, along with their mechanical properties, can be achieved through AlN and Al 2 O 3 additions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44757/1/10853_2004_Article_244049.pd

Effect of AlN and Al2O3 additions on the phase relationships and morphology of SiC Part II: Microstructural observations

Additions of AlN and Al 2 O 3 to β-SiC hot pressed at 2100°C strongly effect the β- to α-SiC phase transformation and the resultant α-SiC polytypes which are formed. Scanning and transmission electron microscopy were utilized to investigate the microstructural changes occurring in SiC due to these additions and to correlate these observations to their mechanical properties. The results suggest that Al 2 O 3 additions stabilize the formation of the 6H-polytype of α-SiC which grows rapidly into an elongated plate-like morphology, while AlN additions stabilize the 2H-polytype of α-SiC resulting in fine equiaxed 2H-SiC: AlN solid solution grains. It is speculated that the elongated growth of 6H-SiC with Al 2 O 3 additions can be controlled through the simultaneous addition of AlN. The formation of 2H-SiC : AlN solid solution grains inhibits the growth of the 6H-SiC grains since AlN(2H) will not go into solid solution in the SiC(6H) structure, effectively pinning the growth of the 6H-SiC grains.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44759/1/10853_2004_Article_244050.pd