Michael P. O'Horo

FeBO3 solid solutions: Synthesis, crystal chemistry, and magnetic properties☆

Abstract Solid solutions of the type Fe1−xMxBO3 have been prepared where M = Mn, Cr, Al, Ga, or In. For M = In, Ga, or Cr, x can vary from 0 to 1.0, but the solid solution range is more restricted for M = Al (O ≤ x ≤ 0.32) and Mn (O ≤ x ≤ 0.10). The present investigation of these materials includes their crystal chemistry, thermal stability, and magnetic properties. The calcite-type unit-cell parameters follow closely Vegards Law. DTA results indicate that the thermal stability increases with increasing M content for M = Cr, Al, or In. Room-temperature magnetic measurements show that the Fe1−xMxBO3 phases remain canted antiferromagnets up to the 20 to 30% substitution level, with monotonic decrease in the magnetization and Curie temperature as a function of the concentration of M (dilution effect). Low-temperature magnetic studies of the systems Fe1−xCrxBO3 and Fe1−xInxBO3 show anomalous magnetic behavior at the higher Cr and In concentrations.

Effect of TIJ heater surface topology on vapor bubble nucleation

We show a correlation between the surface roughness of tantalum heaters in water with the temperature at which nucleation occurs at a set of fixed sites on the heater surface. The smoothest heater displayed the highest nucleation and vapor sheet formation temperatures. Experiments using degassed water indicate that some of the specific surface sites are due to air entrapped in small crevices in the tantalum. The high temperature (> 272 degree(s)C) for the nucleation indicate that the air entrapment sites are on the order of 1 - 4 nm in diameter.

Initial stages of vapor-bubble nucleation in thermal ink-jet processes

We have taken advantage of the improved time resolution (< 50 ns) of a newly developed laser stroboscopic system to study the early stages of vapor bubble nucleation in a thermal ink jet printhead. A transparent channel printhead provides optical access to vapor bubble formation and drop generation processes. Vapor bubble nucleation was found to proceed from the initial formation of localized microbubbles (< 50 ns) that spread with time until a uniform sheet of vapor covers the entire heater surface. The time duration for this process was 400 to 600 ns, depending on the heater voltage. The critical role of the heater surface is demonstrated clearly by the fact that preferential vapor microbubble nucleation sites are observed to persist over long time periods. The region of the heater surface subjected to vapor bubble collapse exhibits different microbubble properties than the rest of the heater surface.

High-speed stroboscopic system for visualization of thermal ink-jet processes

The nucleation and growth of a vapor bubble from superheated water is the triggering event for the eventual ejection of an ink drop in the thermal ink jet (TIJ) printing process. A high speed stroboscopic system capable of time resolving the kinetics of the nucleation process has been developed. The core of the system is a semiconductor laser and a high speed electronic driver that is used to replace the more conventional flashlamp strobe. The time resolution of the new laser strobe is < 50 ns, which is 20-40 times higher resolution than the 1-2 microsecond(s) duration of the typical flashlamp strobe. We observe site specific formation of small vapor bubbles on the surface of a TIJ heater that are stable for up to 0.5 microsecond(s) . These site-specific bubbles also play a role in the growth of the continuous vapor bubble, the expansion of which imparts the force to eject an ink drop. A model is proposed that explains these observations.

Print element for Xerox thermal ink-jet print cartridge

Xerox thermal ink jet print cartridges utilize a print element fabricated via VLSI technology. This fabrication process enables high productivity and precise dimensional control as well as the required electronic functionality. However, modifications to the device geometry involve a complex cycle of mask generation, VLSI fabrication, and assembly. The development of the print element is assisted by the use of experimental wafers which contain TIJ devices with variations in many important geometrical parameters. Analysis of data from measurements on these experimental geometries leads to designs.