September 2014

Self Aligned Nanotube Liquid Crystal Elastomers: Opportunities for flexible energy harvesting systems (WPI Only)
Wednesday, 9/17/2014 12:00 PM-1:00 PM
Washburn Shops & Stoddard Laboratories, WB 229 - Free
Presentation by: Professor Balaji (Baloo) Panchapakesan, Mechanical Engineering

Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using a simple vacuum filtration technique of fabricating nanotube LC films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LC arrangement is preserved, here we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. On excitation by NIR photons, with application of small or large pre-strains, significant expansion or contraction of the sample occurs, respectively, that is continuously reversible and three orders of magnitude larger than in pristine polymer. Schlieren textures were noted in these LC composites confirming long range macroscopic nematic order of nanotubes within the composites. Order parameters of LC films ranged from Soptical = 0.51-0.58 from dichroic ratios. Film concentrations, elastic modulus and photomechanical stress were all seen to be related to the nematic order parameter. For the same nanotube concentration, the photomechanical stress was almost three times larger for the self-assembled LC nanotube actuator compared to actuator based on randomly oriented carbon nanotubes. Investigation into the kinetics of photomechanical actuation showed variation in stretching exponent  with pre-strains, concentration and orientation of nanotubes. The combination of properties, namely, optical anisotropy, reversible mechanical response to NIR excitation and flexible energy conversion all in one system accompanied with low cost makes nanotube LC elastomers important for soft photochromic actuation, energy conversion and photo-origami applications.
Sponsored by: Materials Science & Engineering
For more information, e-mail mtereq@wpi.edu or call 508-831-5633.

October 2014

High Temperature Materials for Harsh Environments from Aerospace Thermal Protection Systems to Advanced Industrial and Energy Applications (WPI Only)
Wednesday, 10/8/2014 12:00 PM-1:00 PM
Washburn Shops & Stoddard Laboratories, WB 229 - Free
Presentation by: Dr. Jorge Barcena, Tecnalia Research & Innovation, Industry and Transport Division

Applications on extreme conditions demand the use of high temperature materials, where the performance of other class of material is not enough to withstand the high requirements and constraints. The most driving application for such materials comes from the Aerospace sector, where a vehicle or capsule that enter into a planetary atmosphere (e.g. the Earth) require the use of a thermal protection system (TPS) to shield them from aerodynamic heating. Otherwise the substructure or payloads of the vehicles would be damaged during the return from outer space or during cruise at hypersonic speed. This lecture gives an overview of the past and novel state-of-the-art materials for these extreme conditions (advanced alloys, ceramic matrix composites, ultrahigh temperature ceramics) and their envisaged aerospace applications (vehicles, mission, projects, roadmaps). Current and future uses on non-space applications will be depicted such as on automotive, nuclear and solar energy.
Sponsored by: Materials Science & Engineering
For more information, e-mail mtereq@wpi.edu or call 508-831-5633.

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