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RESEARCH PROF. SOCIETIES,
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Coating: Aluminum oxide (Al2O3) Description: Deposited with the Al2O3 MOCVD system, this coating was annealed for 20 hours at 1100 degrees Centigrade. During transformation from amorphous (non-crystaline "structure") to the stable alpha phase, the coating underwent a volume reduction of about 10 percent. This stress plus CTE mis-match stresses upon cooling created very large forces which caused the coating to spall (spring off), creating the diffrent patterns observed.
Coating: Aluminum oxide (Al2O3) Description: The same coating and system were used as in the optical micrograph above, but this time the coating survived the annealing at 1100 degrees centigrade. The cracking and volume shrinkage due to phase transformation are very clear here. The coating remained attached becase the CTEs of Al2O3 and CSZ are quite close, and the CSZ is porous, making it able to absorb any remnant stresses.
Coating: Aluminum oxide (Al2O3) Description:
Coating: none Description:
Coating: Aluminum oxide (Al2O3) Description: A continuous aluminum oxide coating about 100nm thick was deposited on the substrate morphology. After annealing at 1100 degrees Centigrade for 20 hours, the coating exhibited a "ridged" surface. I ti most likely that the coating has rearranged itself into smaller "pockets" in order to reduce the overall surface/interface energy.
Coating: Aluminum oxide (Al2O3) Description: The aluminum oxide coating on this substate is about
150nm thick. After annealing at 1100 degrees Centigrade for 20 hours,
the coating exhibited a worm-like morphology. Occasional "mounds"
are also observed, as at the top of the picture. This structure most likely
evolved from the thermodynamic forces associated with reduction of the
overal surface/interfacial energies.
Coating: Aluminum oxide (Al2O3) Description: Several cracks may also be observed running roughly
North-South and East-West. These are a result of the phase transformation
and volume reduction stresses created during annealing.
Coating: Aluminum oxide (Al2O3) Description: After annealing at 1100 degrees Centigrade for 20
hours, the coating transformed from amorphous to the crystalline alpha
structure, as may be observed around the edges of the picture. The main
feature appears to be a fully transformed region of the coating which
has either retracted due to volume shrinkage or spalled a portion of the
coating.
Coating: none Description: The same
Coating: Aluminum oxide (Al2O3) Description: An aluminume oxide coating was deposited on this
substrate by CVD. After ___________ at xxx degrees Centigrade for ___
minutes, a dual-phase structure developed. The two phases of aluminum
oxide present are alpha (the most stable) as the large rock-like grains,
and gamma as the platelet/cicular areas.
Coating: none Description:
Coating: none Description:
Coating: none Description: The fiber shown above is about one third the diameter
of a human hair. The ridge in the center is from making two passes with
a razor to cut the fiber. The curled "eye lashes" at the top
of the fiber indicate that even the second pass with the razor was not
enoubh, and the fiber had to be pulled apart.
Coating: none Description: This is a close-up of the cut surface shown in the
picture above. Note the sub-micron size cracks and the larger striations
created when the fiber was cleaved.
Coating: Tantalum (Ta) Description: For this sample, metallic Tantalum was deposited
on a foam substrate. As the metal was deposited, the foam "scaffolding"
was burned off, leaving behing a metallic foam-like structure. This open
structure will be used to coat skeletal implants, providing the regenerating
bone a structure with which it may bond mechanically.
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This page was last updated on 30Dec04. |
