Pascal Bellon

My research program is mainly focused on alloys or mixtures submitted to a sustained external forcing: such conditions are often met during either the processing of materials (e.g. by ball-milling or during thin film growth) or during the use of these materials (e.g. during frictional wear or under irradiation). Alloys in such environments have been termed "driven alloys." When the intensity of the forcing is high enough, non-equilibrium phases or microstructures can develop. From a practical point of view, these driving forces can have deleterious effects on the properties of materials: for instance precipitates can be dissolved,leading to a loss of mechanical strength. On the other hand, non-equilibrium processing can provide new routes to synthesizing novel materials: e.g., extended solid solutions or functional nanocomposites can be obtained by processing powders with high-energy ball milling or by processing thin films with energetic ion beams.

The related facet of our research is on the kinetic evolution of alloys during heat treatments. We are taking advantage of the kinetic models developed for driven alloys to study diffusion phenomena and diffusion-controlled reactions such as nucleation, growth and coarsening in complex alloys.

We are performing experiments, atomic computer simulations (kinetic Monte Carlo and molecular dynamics) and analytical modeling of these nonequilibrium alloys. The experiments carried out in our laboratory include ball-milling, wear testing, ion and laser irradiation (in collaboration with Prof. Averback). Materials are characterized by using the facilities available at the National User Facility at the Materials Research Laboratory. These include SEM, TEM, HRTEM, DSC and X-ray diffraction. Computer simulations are run on our cluster of LINUX workstations, and at computation centers on campus (MRL-MCC, MRL-CFC).

R. A. Enrique and P. Bellon, "Nonequilibrium fluctuations, effective temperature, and effective interactions driven by irradiation of alloys," Phys. Rev. B 70 (2004): 224106.

K. Sastry, D. D. Johnson, D. E. Goldberg, and P. Bellon, "Genetic programming for multiscale modeling," Inter. J. Multiscale Comp. Eng. 2 (2004): 239-256.

Jia Ye and P. Bellon, "Nanoscale patterning of chemical order induced by displacement cascades in irradiated alloys. I. A kinetic Monte Carlo study," Phys. Rev. B 70 (2004): 094104.

Jia Ye and P. Bellon, "Nanoscale patterning of chemical order induced by displacement cascades in irradiated alloys. II. Analytical modeling," Phys. Rev. B 70 (2004): 094105.

J. D. Hahn, Fang Wu, P. Bellon, "Cr-Mo solid solutions forced by high-energy ball milling," Metallurgical and Materials Transactions 35A (2004): 1105-1111.

P. Bhattacharya, P. Bellon, R. S. Averback, S. J. Hales, "Nanocrystalline TiAl powders synthesized by high-energy ball milling: effects of milling parameters on yield and contamination," J. Alloys and Compounds 368 (2004): 187-196.

R. Enrique, K. Nordlund, R. S. Averback, P. Bellon, "Simulations of dynamical stabilization of Ag-Cu nanocomposites by ion-beam processing," J. Appl. Phys. 93 (2003): 2917.

J. Ye, Ji-wen Liu, R. Enrique, P. Bellon, "Compositional and order patterning in driven alloys: the role of external-forcing characteristic lengths," Scripta Mat. 49 (2003): 969.

P. Bellon, R. S. Averback, "Preface to viewpoint set on: materials under driving forces," Scripta Mat. 49 (2003): 921.

R. Enrique, F. Wu, P. Bellon, "A new approach for the direct synthesis of nanocomposite thin films by ion-beam processing," Surface Coatings and Technology 150 (2002): 1.

J.-M. Roussel, P. Bellon, "Self-diffusion and solute diffusion in alloys under irradiation: Influence of ballistic jumps," Phys. Rev. B 65 (2002): 144107 (2002).

J. Liu, P. Bellon, "Patterning and ordering in driven alloys with coupled conserved and nonconserved order parameters," Phys. Rev. B 66 (2002): 020303(R).

S. Zghal, M. J. Hÿtch, J.-P. Chevalier, R. Twesten, F. Wu, P. Bellon, "Electron microscopy nanoscale characterization of ball-milled Cu-Ag powders. Part I: Solid solution synthesized by cryo-milling," Acta Mater. 50 (2002): 4695.

S. Zghal, R. Twesten, F. Wu, P. Bellon, "Electron microscopy nanoscale characterization of ball-milled Cu-Ag powders. Part II: nanocomposites synthesized by elevated temperature milling or annealing," Acta Mater. 50 (2002): 4711.

P. Bellon, G. Martin, "Coupled relaxation of concentration and order fields in the linear regime," Phys. Rev. B 66 (2002): 184208.

Fang Wu, P. Bellon, T. Lusby, A. Melmed, "Forced mixing and nanoscale d ecomposition in ball-milled Cu-Ag characterized by APFIM," Acta Mater. 49 (2001): 453.

R. Enrique, P. Bellon, "Compositional patterning in immiscible alloys driven by irradiation," Phys. Rev. B 63 (2001): 134111.

J.-M. Roussel, P. Bellon, "Vacancy-assisted phase separation with asymmetric atomic mobility: coarsening rates, precipitate composition and morphology," Phys. Rev. B 63 (2001): 184114.

R. Enrique and P. Bellon, "Self-organized Cu-Ag nanocomposites synthesized by intermediate temperature ion-beam mixing," Appl. Phys. Lett. 78 (2001): 4178.

M. Athenes, P. Bellon and G. Martin, "Effects of atomic mobilities on phase separation kinetics: a Monte-Carlo study," Acta Materialia 48 (2000): 2675.

R. Enrique, P. Bellon, "Compositional patterning in systems driven by competing dynamics with different lengthscale," Phys. Rev. Lett. 84 (2000): 2885.

D. Le Floc'h, P. Bellon, M. Athènes, "Slow coarsening of B2-ordered domains at low temperatures: a kinetic Monte-Carlo study," Physical Review B 62 (2000): 3142.

• NSF CAREER Award (1998)
• GE Scholar, Academy for Excellence in Engineering Education (1998)
• GE Fellow, Academy for Excellence in Engineering Education (1999)
• Collins Fellow, Academy for Excellence in Engineering Education (2000)
• Donald Burnett Teacher of the Year Award (2000)
• Accenture Engineering Council Award for Excellence in Advising (2007)
• Stanley Pierce Award (2009)