New NCC article

Terry Musho (now an Assistant Professor at West Virginia University) got a new article published in Micro-Nanoscale Thermophysical Engineering.  The article is titled "Quantum Simulation of Nanocrystalline Composite Thermoelectric Properties" and shows how nanocrystalline composites are advantageous to thermoelectric materials compared to superlattice materials structures.  The paper considers electronic effects using a Green's function quantum solution. Congratulations to Terry.

Zack Defends

Zack Coppens successfully defended his Master's thesis on November 29, 2012. He has been on loan from Sandia National Lab to conduct thermal studies on metamaterials. The title of his thesis is ``Probing and Controlling Photothermal Heat Generation in Plasmonic Nanostructures.'' His contribution included a demonstration of how a nanoantenna can be optimized for localized heat generation. He also pioneered a novel temperature measurement technique using thin layers (100 nm) thermographic phosphors (ruby to be exact). A link to his work will be provided as soon as we get the URL from the grad school. We wish him the best as he transitions back to Albuquerque.

Zack after his defense

AVS presentation

Bobby Harl (Chemical Engineering PhD candidate and LumRad group member) will be presenting a poster and will be giving a talk at the 2012 AVS 59th International Symposium and Exhibition in Tampa Florida that is taking place this week. The title of his work is "Synthesis and characterization of yttrium aluminum garnet and lanthanum zirconate particles" (Poster: SS-TuP5; Talk: SS+OX-WeM4). Congratulations to Bobby and his co-authors (S. L Gollub, D.G. Walker and B.R. Rogers).

Presentation at RADECS

Ph.D. student Stephanie Weeden-Wright (of the Radiation Effects and Reliability group at Vanderbilt) has been collaborating on a project to show how the luminescence of a heterogeneous substance can be used to indicate radiation damage through photoluminescence.  The article "Radiation Effects on the Photoluminescence of Rare-earth Doped Pyrochlore Powders" is part of our LumRad project (funded by DTRA).  She recently returned from France where she presented her work at RADECS.  Here is a pre-print of the conference proceedings.

Congratulations to Stephanie.

NCC publication (Musho)

Terry Musho (May 2012 Ph.D. graduate from the Thermal Engineering Lab, who is now an Assistant Professor at West Virginia University) had a new paper accepted in the Nanoscale/Microscale Thermophysical Engineering Journal.  The article describes a quantum model for studying the thermoelectric properties of nanocrystalline composites.  This builds on our substantial portfolio of modeling and simulation research on thermoelectric transport in nanophase materials using non-equilibrium Green's functions (NEGF).  The paper is being sent to the publishers; in the meantime, here is a preprint.   

Congratulations to Terry.

Gee-whiz photos

Ken Frampton made some really neat pictures of our phosphors.  The green one is YGG:Ce and red one is a europium doped organic phosphor.

Mystery phosphor

Ross Fontenot (University of Alabama A&M) and Andy Hollerman (University of Louisiana Lafayette) dropped by a couple of weeks ago to leave a triboluminescent phosphor for us to test.  It is an organic phosphor but behaves more like an inorganic phosphor.  It is doped with europium, which is good, because we know a good bit about that particular activator.  Although I don't feel right about naming the material and providing our spectral data (after all, Andy and Ross have not finished publishing on the material), I can say that the europium peaks are slightly different than those found in most ceramic oxide host lattices. In the picture you can see the characteristic europium glow under a UV flashlight.

under room light

under UV light

We are particularly excited about the material because it could hold significant promise in our LumRad project.  LumRad is the name of the DTRA funded program to identify candidate phosphors for remote radiation detection.  Our hypothesis is that radiation induced damage will change the photoluminescent properties of phosphor materials that can be queried at any time after irradiation (i.e. we are not using the material as a scintillator).

Core-shell decay measurements

The lab is working with a high-school student this semester from the Vanderbilt School for Science and Math. We'll call him BB. This is a program that brings in advanced students in the Metro Nashville public school systems to receive college-level training in science and math.  As part of their instruction, they are paired with a research lab where they spend 4 hours per week conducting research along side graduate students.  Thanks go to Sadie for helping direct him in his research activities.

Today, BB took decay measurements of a core-shell nanoparticle we received from Yuanbing Mao at University of Texas, Pan American.  The core is LZO:Eu and the shell is YBO.  The spectral response is typical of europium, but the relative intensity of the peaks is different than that of our own bulk samples of LZO:Eu.  The decay data (BB's measurements) shown in the figure have strong multi-exponential components.

single: rms = 0.0654149
        I = 0.974968(0.297568) tau = 4.53009e-06(1.40148e-11)
double: rms = 0.0557005
        I = 0.0764344(0.0151942) tau = 0.000148201(9.63947e-08)
        I = 0.985433(0.394193) tau = 3.21211e-06(1.1205e-11)
triple: rms = 0.0553772
        I = 0.072394(0.101939) tau = 5.12744e-05(2.12708e-07)
        I = 0.0316655(0.0936514) tau = 0.000307173(5.42085e-06)
        I = 0.970849(0.451075) tau = 2.97923e-06(1.54917e-11)

Introducing the TELab blog

The Thermal Engineering Lab at Vanderbilt is starting a blog.  Please visit the TElab website for details on who we are and the type of research we perform.