Processing, Design and Control for Nanotechnology Materials Systems

 

Nanoparticles are the precursors of nanostructured materials and devices with tailored properties.  Nanoparticle engineering involves the synthesis and processing of nanometer-sized particles with controlled properties for applications in advanced materials, such as ceramics, metals, optical structures, and semiconductors.  Metals and ceramics produced by consolidating nanoparticles with controlled microstructures have been shown to exhibit properties substantially different from materials with coarse microstructures.  New properties include greater hardness, higher yield strength, and ductility in ceramic materials.  In addition, the band gap of nanometer-scale semiconductor structures increases as the size of the microstructure decreases, raising expectations for many possible optical and photonic applications.  Initial observations also suggest that the carbon nanofibers can be used to produce conductive polymeric materials. 

 

Maybe the most significant development in nanomaterial technology has been that of nanotubes.  Nanotube materials have an impressive list of attributes.  They can behave like metals or semiconductors, can conduct electricity better than copper, can transmit heat better than diamond, and they rank among the strongest materials known.  The potential aerospace applications are enormous.  However, many technological hurdles need to be overcome before large-scale applications will occur.  Present techniques used to produce nanotubes are inappropriate for mass production and high-quality nanotubes can only be produced in very limited quantities.

 

UES personnel address the technical hurdles needed to develop nanotechnology materials systems for inclusion into electro-optical, tribological, and power devices/technologies.  They conduct and support research to develop advanced materials and process design and control technologies to enable more repeatable and affordable manufacturing capabilities. 

 

Some of the specific tasks being performed today are:

 

a. Formulation of a two-part conductive elastomer system with a primary conductive filler of multi-wall carbon nanotubes.  The Air Force has needs for conductive gap filler materials and conductive coatings.  Usually, the conductive materials are based upon the dispersion of metallic particles into resin matrices.  The most common metals in use are silver, copper and nickel.   While the conductivity levels attainable through the use of the metallic particles are generally quite high and adequate, products formulated with metallic particles sometimes lack all of the desired application characteristics and physical properties.  For example, cure rates, low temperature flexibility and shrinkage of a conductive material can ultimately impact the mission readiness of an Air Force vehicle.

 

b. Development of a process to produce in quantity single wall nanotubes with single, uniform diameter.  Effort includes technologies such as functionalization, cloning, solubalizing and modeling of single wall carbon nanotubes (SWNT).  SWNTs exist as metallic and semiconducting types (band gaps in the near infrared) Metallic SWNTs are known to exhibit extreme electrical properties along the axial direction and recent results at Rice have shown that semiconducting SWNTs readily emit Near-IR radiation at their respective band gaps. Both types possess extreme thermal conductivity and strength along the nanotube axis.  In addition to the possibilities for high strength materials, the sensitivity of the electrical and optical properties of SWNTs to their environment suggests that unique sensor applications at the nanoscale level can be developed as methods evolve for production of nanoscale arrays of SWNTs

 

c. Development of synthesis and assembly techniques for large quantities of nanoparticles.  Technical work includes new modeling and optimization techniques; process development and control with validation experiments; and characterization and new sensor development to accomplish same.  Investigations will include efforts to efficiently produce the nanotechnology material system as well as efforts to determine the applicability of the materials system in the functional device/technology (including application of interim or associated technologies needed to test concepts).