April 2014 - Bnc-grads-list

NSAC Elections and Committee sign-ups (updated links)
by NSAC 23 Apr '14

23 Apr '14

*Information about the officer positions and their duties *is available at the sign-up form https://docs.google.com/forms/d/1jzX_Cp3_vKoS0_LU_NP30yXOI7yj3Am4qbL92ktULu… . *Information about the committees* is available at the sign-up form https://docs.google.com/forms/d/1b0t5NmmzaI8xYumywIshF1b89dUAFMtGDrbtHLjjhQ… .

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FW: Graduation Party
by Anthrop, Heather L 21 Apr '14

21 Apr '14

Just a reminder, as I know there are more than 2 people who are graduating :) Thank you, Heather L Anthrop From: Anthrop, Heather L Sent: Wednesday, April 16, 2014 12:04 PM To: Bnc-grads-list(a)ecn.purdue.edu Subject: Graduation Party Birck will be having a graduation party to celebrate all of our Spring 2014 graduates. If you are a graduate please let me know by April 23rd. Thank you, Heather L Anthrop Purdue University Birck Nanotechnology Center 1205 West State Street West Lafayette, IN 47907 (765) 494-7053

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Graduation Party
by Anthrop, Heather L 16 Apr '14

16 Apr '14

Birck will be having a graduation party to celebrate all of our Spring 2014 graduates. If you are a graduate please let me know by April 23rd. Thank you, Heather L Anthrop Purdue University Birck Nanotechnology Center 1205 West State Street West Lafayette, IN 47907 (765) 494-7053

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Visit to Northwestern University - Saturday, April 19th (RSVP by 4/16)
by NSAC 13 Apr '14

13 Apr '14

Dear BRK grad students, NSAC's Research Awareness Committee would like to invite you to a day trip to visit Northwestern University (Evanston, IL) on *Saturday April 19th, 2014*. Northwestern University is one of the country's leading private research universities, with an annual budget of $2 billion and sponsored research in excess of $500 million. Located on two lakeshore campuses - one in Chicago and one in Evanston, the first suburb north of Chicago - Northwestern enrolls about 17,000 students and has some 2,500 full-time faculty. It has a long history of leadership in interdisciplinary research programs and centers. More than 90 school-based centers and 26 University centers support interdisciplinary research that spans a wide spectrum of areas, including neuroscience, nanotechnology, biotechnology, and drug discovery. [ http://www.research.northwestern.edu/] The agenda for the day is as follows: 8am Leave Birck 9am Breakfast 11am - 1pm Northwestern University (Lab Tours I) 1pm Lunch 2am - 3:30pm Northwestern University (Lab Tours II) 4pm - ? Downtown Chicago (Dinner?) (agree on a departure time with your driver) If you are interested in going, please* reply to this email by April 16th*; availability is on a first-come, first-served basis (*limit 15 people*). We'll have 3-4 drivers; further information regarding transportation will be sent later. Email nsac(a)purdue.eduif you have any questions/comments. See you then! NSAC

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Y. Wang PhD Final April 10, 2014 Notice
by Anthrop, Heather L 09 Apr '14

09 Apr '14

Note: Seminar and Exam location in DLR 143A MATERIALS SCIENCE AND ENGINEERING SEMINAR MSE PhD Final Examination Branched Nanowire Arrays as Bulk-like Thermoelectric Materials by: Yuefeng Wang Advisor: Prof. T. Sands ABSTRACT Thermoelectric generators (TEG) and coolers (TEC) consist of a plurality of n-type and p-type semiconductor TE leg elements, which can be utilized to convert heat into electricity, or conversely, create temperature gradients. The efficiency of a TE device is directly related to the material’s dimensionless thermoelectric figure of merit, ZT = S2σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity. Bulk-alloy bismuth telluride (Bi2Te3) as the most widely used TE material has a room temperature ZT around unity. Recent research progress in nanostructured materials and composite materials enlightened the path to enhance the ZT above 1. Nanowire array topologies offer promise for engineering the electrical conductivity and phonon scattering effects, both of which have been studied extensively since the 1990s. Conventional porous anodic alumina (PAA) was used for successful fabrication of Bi2Te3 nanowire arrays, but with array thicknesses limited to tens of μm, too thin for high performance TE devices. The parallel nanowire arrays also suffer from mechanical fragility, low Bi2Te3 volume fraction, limited thermal conductivity suppression, vulnerability to shear load and slow template fabrication. In this work, I investigated the Bi2Te3 branched nanowire array (BNA) topology that features nanostructure-to-bulk-like materials integration and radially modified nanowire compositions, allowing for thermal conductivity (κ) reduction, multiscale nanostructure creation, preservation of power factor (S2σ), strain relaxation and shear compliance. Branched Bi2Te3 nanowire arrays were fabricated from the bottom up by electrochemically depositing Bi2Te3 into 300-500 μm thick branched porous anodic alumina (BPAA) templates followed by vapor annealing. The annealing process homogenizes the native point defects and can be used to introduce Se as an axially-graded dopant, which also forms nanocrystalline Bi2SeTe2 phonon scatterers. The thic kness of the nanowire array device can be fabricated up to 350 μm (wire aspect ratio > 1000:1), which is approaching commercialized bulk-form TE elements. Various characterization techniques including XRD, FESEM, HRTEM, EDS, AFM, etc. were employed to analyze the morphologic, structural and stoichiometric properties of the material. At room temperature, characterization of electrical, thermal and Seebeck properties were performed to demonstrate the device-level fabrication viability. At 300K, thermal conductivity was measured to be 0.5W/m-K. Electrical conductivity was measured at ~1.43x104 S/m. An effective bulk ZT of 0.31 was measured and the microscopic corrected value was 0.39. To demonstrate the p-type TE counterpart, pulsed laser assisted electrodeposition was used to fabricate Bi0.5Sb1.5Te3 nanowires. In addition, in order to calculate the optimum thermoelectric element leg length under different heat transfer conditions, a numerical model of thermoelectric device for both n- and p-type legs was developed in Matlab and powered by Rappture on nanoHUB.org. The demonstration of Bi2Te3 branched nanowire array structures enables a nano-to-bulk, composition-modulated and potentially scalable method to fabricate thermoelectric materials. The BNA structure maintains the nanowire electrical conduction continuity by electrochemical deposition, and offers extensive control over the wire radial composition and nanostructure. Moreover, the BNA’s phonon scattering effect is attributed to nanowire array branching, high surface to volume ratios, grain boundaries, Bi2SeTe2 nanocrystals and atomic alloying, covering length scales ranging from tens of μm down to less than 1 nm. Overall, the branched Bi2Te3 nanowire array as a bulk-like thermoelectric material is a promising structure for enhancing the figure of merit, ZT, and has promise to lead to the development of superior engineered nanomaterials as a substitute for bulk Bi2Te3 alloy materials. This work was partially supported by Office of Naval Research. Date: Thursday, April 10, 2014 Time: 10:30 A.M. Place: DLR 143A

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FW: Nanodays Volunteers
by Shakouri, Ali 03 Apr '14

03 Apr '14

Dear All, NanoDays 2014 will be held next Thursday and Friday, April 10th and 11th from 9am to 1pm. It will help us a lot if you could volunteer a few hours of your time for this program. You just need to sit at pre-made activity tables and help the students go over some simple hands on activities and explain the nano concepts behind the activity. If you could help, please see Jaime in BRK 1027 or email her at jjturner(a)purdue.edu<mailto:jjturner@purdue.edu> to sign up for a time. Thanks a lot. Best regards, Ali

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