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Researchers in many fields including materials
science, geology, physical chemistry and biochemistry will now be able
to tailor material properties that are sensitive to microstructure.
According to senior author Ainissa G. Ramirez,
assistant professor of mechanical engineering, the Yale team monitored
real-time images taken at two-second intervals while they heated
crystallizing samples of nickel-titanium within a transmission
electron microscope.
They directly determined the rate of crystal
assembly (nucleation), and the rate that the crystals grew, by
measuring the number of crystals and their change in size with time.
Their results agree with the conventional
Johnson-Mehl-Avrami-Kolmogorov method which only gives an overall
crystallization rate, with the nucleation and growth rates coupled.
The novel contribution of this work is that the
nucleation and growth rates are measured independently during
crystallization and can be used to infer the grain size after
crystallization is complete.
"We used the mathematics of crystallization in a
new way," said Ramirez. "We found that our measured grain sizes and
the mathematical predictions agreed over a broad range of temperatures.
This method allows researchers to now explore the connection between
structure and properties of different materials." |
