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- Bremsbelag (2)
- 9-12% Cr-steels (1)
- Corrosion gases (1)
- Diffusion (1)
- Electron microscopy (1)
- FC solder bonding (1)
- FIB (1)
- High temperature corrosion (1)
- Hydrogen transport (1)
- Intermetallic phases (1)
The resistance of structural steels against corrosion in CO2-H2O and CO2-H2O-O2
atmospheres at temperatures above 550°C was observed with high magnification methods.
The test atmosphere is the basic composition of an oxyfuel coal combustion atmosphere. The
analytical information base was applied to develop reaction schemes for the oxidation of
steels. It was demonstrated that the formation of phases and the kinetics of oxidation reactions
in this atmospheres is affected by the formation of intermediate iron hydroxide and a high
carbon activity. In the temperature regime above 550°C the thermal equilibrium between H2O,
CO2 and Fe reacted and formed CO. CO triggers the formation of FeO and carbides and
increases the reaction kinetics. Porosity at the interface is established by gaseous phases
such as Fe(OH)2 or H2O. H2 formation is not limited to the steel - oxide interface but can occur
in the whole oxide scale. Examples of the experimental results were compared with a
thermodynamic approach. The objective of the work was to derive qualitative rules of the basic
corrosion reactions.
Platinum does not form any adherent oxides and can be easily wetted by tin-based solders. Platinum is also an available metallization in semiconductor laboratories. Therefore we investigated the diffusion of platinum thin-film metallizations into eutectic tin–lead solder by using a high-resolution secondary ion mass spectroscopy (SIMS) profiling from the back side. It is shown that an intermetallic phase (PtSn4) is formed during soldering, which controls the consumption of platinum during soldering and in operation. The consumption of platinum follows the well-known parabolic diffusion law. The activation energy of this process is 0.63 eV. Even at extended heating cycles of 2 min at 250°C, 190 nm from the original 300 nm of the platinum film remain undissolved. This high stability makes platinum a very attractive thin-film metallization for flip-chip (FC) bonding of new microsystems.
Transmission electron microscopy study of rapid thermally annealed Pd/Ge contacts on In0.53Ga0.47As
(1996)
Phase formation in rapid thermally annealed Pd/Ge contacts on In0.53Ga0.47As has been investigated by means of cross-sectional transmission electron microscopy, convergent-beam electron diffraction, and energy-dispersive x-ray analysis. Solid-phase regrowth is observed to occur similarly as in Pd/Ge contacts on GaAs or InP. The reaction starts at low temperatures with the formation of an amorphous Pd–In–Ga–As layer, which crystallizes at elevated temperatures yielding hexagonal Pd4In0.53Ga0.47As being first described in this work. At temperatures .250 °C, this phase decomposes due to epitaxial solid-phase regrowth of In0.53Ga0.47As and formation of Pd–Ge phases. The stable composition is reached at temperatures .350 °C with excess Ge diffused through top Pd–Ge to the contact interface and growing epitaxially on the semiconductor.