Physics & Astronomy Colloquium
April 18 @ 3:30 pm - 5:00 pm
Speaker: Robert D. Shull (NIST)
Title: The Magnetocaloric Effect
Abstract: One of the largest uses of energy in the world is the heating and cooling of spaces. Unfortunately, the existing technology based on the expansion and compression of a gas is only partially efficient, and utilizes environmentally harmful materials. As a consequence, the scientific community has been looking for an alternative technology. One such option is magnetic refrigeration wherein a material is subjected to a magnetic field (H) which cycles between zero and H0. Because it employs a reversible cycle, it has potential Carnot efficiencies. The technology is based on the magnetocaloric effect of a material, the topic of this presentation. Here the basis for this effect will be described along with how it’s magnitude varies with the type of material being considered, including in nanocomposites. Also to be discussed will be how the effect is measured, how it varies with temperature, and the proper way of using it to compare different materials.
Robert D. Shull received a S.B. in Materials Science from MIT in 1968, and a M.S. and Ph.D. in the same field from the University of Illinois at Urbana-Champaign in 1973 and 1976 respectively. His PhD thesis work, in which he discovered the “reversed Curie temperature” phenomenon in Fe70Al30, was instrumental in his recent discovery of “Spin Density Waves” (a phenomenon which had been predicted 40 years ago to exist, but never found) in the same alloy system. After being awarded a postdoctoral fellowship from CALTECH between 1976-1979, he joined the National Bureau of Standards where he initially set up the rapid solidification facility that led to the discovery of “quasicrystals” in 1980. Dr. Shull was also part of the collaboration that prepared the first thin films of a high TC superconductor by the laser ablation process (awarded “Best Paper of the Year” at the Applied Physics Laboratory of JHU), and his field ion microscopy observation of the high TC materials (first ever) was even featured on the cover of Science magazine (Jan. 8, 1988). He was the first to explain the novel “attractable levitation” found in some high TC materials, and he discovered the enhanced magnetocaloric effect in nanocomposites.
Dr. Shull has authored and co-authored over 200 publications and presented over 300 invited talks. He was the Chair of the International Committee on Nanostructured Materials (ICNM) from 1999-2001. He was also a founding member of the OSTP subcommittee on Nanoscale Science, Engineering and Technology (NSET), the group which drafted the original National Nanotechnology Initiative (NNI) in 2001. Dr. Shull has been awarded several NIST Director’s Innovation and Competence Awards, two NIST EEO/Diversity Awards, and the Outstanding Service Award by the NIST Chapter of Sigma Xi. He is a Fellow of IEEE, a Fellow of TMS (The Minerals, Metals, and Materials Society), and an Honorary Member of the Indian Institute of Metals. He has also helped lead a 6-month long pre-high school science program for 250 children each year, called 4H Adventure In Science, for the past 31 years. He is presently a NIST Fellow (previously the Group Leader of the Magnetic Materials Group) in the Material Measurement Laboratory (MML) at NIST. Dr. Shull is also the son of Dr. Clifford G. Shull, the 1994 recipient of the NOBEL PRIZE in Physics.