Vanderbilt University Chemical and Biomolecular Engineering

Education

B.S., University of Pittsburgh, 1961

M.S., University of Denver, Physical Metallurgy, 1963

Ph.D., Vanderbilt University, Materials Science, 1969

Contact Information

Dept. of Chemical and Biomolecular Engineering
Vanderbilt University
VU Station B, Box 351604
Nashville, TN 37235-1604

Phone: (615) 322-7047
FAX: (615) 343-7951

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Research

Research activities are in the general area of materials science. For the past several years there has been a specific focus on the fundamentals of solidification. Studies of nucleation of solids from metastable liquids and the growth of solids under such metastable conditions have been of primary concern. There has been a particular emphasis on the structure and properties of alloys resulting from deep undercooling through containerless processing. Accompanying this has been a great interest in materials processing under microgravity conditions. In this regard, experiments in low earth orbit have been conducted on three separate flights of space shuttle Columbia. Research studies currently being conducted include:

• The effect of solutes on the nucleation of solids from metallic melts. The objective of the research is to understand the role of oxygen and nitrogen in nucleation in metals. Experiments are being conducted on dilute solutions of oxygen and dilute solutions of nitrogen in zirconium. The work is framed in terms of two basic hypotheses. The first is that there is a significant and quantitatively definable effect of the solutes on the nucleation behavior of solids in zirconium. The second is that the results will correlate with classical nucleation theory. Experiments involve the determination of nucleation frequency as a function of undercooling and the determination of prefactors and exponential factors in the nucleation rate equation.

• The effect of nucleation temperature and alloy composition on the speed of solidification. Present theories relating the solidification velocity to the degree of undercooling and alloy composition do not agree well with present theories. In fact, there is great discrepancy in the data amongst various investigators. Most of the investigations have used indirect methods for the measurement of solidification velocity. This work utilizes direct observation of the solidification front by ultra high-speed imaging. Frame rates up to 1,000,000 frames per second are used to monitor the progression of the solidification front across the surface of a levitated specimen to directly obtain the speed of solidification. Measurements in pure nickel, pure titanium and pure silicon are being used as a benchmark against which solidification in alloys are being compared. Alloys being studied are nickel-tin, nickel-silicon, nickel-titanium, and nickel-carbon, as well as several titanium base systems.
  

Selected Publications

Nagashio, K., W.H. Hofmeister, D.E. Gustafson, A. Altgilbers, R.J. Bayuzick, and K. Kuribayashi, "Formation of NdBa₂Ba₂Cu₃O_7-d Amorphous Phase by Combining Aero-acoustic Levitation and Splat Quenching," J. Mater. Res.,16, no. 1 (January 2001).

Rosner-Kuhn, M., W.H. Hofmeister, G. Kuppermann, R.J. Bayuzick, and M.G. Frohberg, "Investigations to the Influence of Oxygen on the Surface Tension of Zirconium by Oscillating Drop Techniques," Surface Science, 443, no. 3, (December 1999): 159-164.

Hofmeister, W.H., R.J. Bayuzick, R. Hyers, and G. Trapaga, "Cavitation-induced Nucleation of Zirconium in Low Earth Orbit," Applied Physics Letter 3, 74, no. 18 (May 1999): 2711-2713.

Morton, C. W., W. H. Hofmeister, R. J. Bayuzick, A. J. Rulison, and J. L. Watkins, "The Kinetics of Solid Nucleation in Zirconium, "Acta Mater 46, no. 17 (1998): 6033-6039.

Hofmeister, W. H., C. W. Morton, and R. J. Bayuzick, "Monte Carlo Testing of the Statistical Analysis of Nucleation Data," Acta Mater 46, no. 6 (1998).

Hofmeister, W. H., R. J. Bayuzick, G. Trapaga, D. M. Matson, and M. C. Flemings, "Observation of Thermal Profiles During Impact and Solidification of Nickel Drops," Solidification 1998, edited by S. Marsh, et al. Warrendale, Penn.: TMS, 1998.

Sanchez Sarmiento, G., A. E. Blangino, E. G. Sancho, W. H. Hofmeister, B. T. Bassler, and R. J. Bayuzick, "Parameter Optimization in Steady State Growth of Cell Arrays," Computational Mechanics, New Trends and Applications, edited by E. Onate and S.R. Idlesohn, Barcelona, Spain: CIMNE, 1998.

Bassler, B.T., W. H. Hofmeister, and R. J. Bayuzick, "Ultra High Speed Imaging System for the Measurement of Solidification Velocity via Direct Observation of Rapid Solidification," Rev. Sci. Instr. 68, no. 4 (April 1997).

Rulison, A.J., W. K. Rhim, W. H. Hofmeister, C. M. Morton, and R. J. Bayuzick, "Containerless Liquid to Solid Nucleation Pathways in Two Representative Grades of Commercially Available Zirconium," Acta Mater 45, no.3 (1997).

Hofmeister, W.H., S. Shankar, and R. J. Bayuzick, "Optical Pyrometry on TEMPUS: A Critical Assessment of Noncontact Temperature Measurement in Low Earth Orbit," Space Processing of Materials, Proc. SPIE 2809, edited by N. Ramachandran (July1996).