Nano-powders for NEMS

II-5: Nano-Powders for NEMS
PI: Christopher Shearwood
Collaborator: S. Moochhala (DSO)

Abstract
Nano-powders have many unique advantages including lower sintering temperatures, high surface area for catalyst activity, enhanced mechanical properties due retention of nano-grain size, possibility of PIM (Powder Injection Molding) to generate micro- and nano-structures. Preliminary work has already been made on a number of systems including Pt (chosen for its bio compatibility), W (chosen for its excellent mechanical properties and wide commercial interest), and NiTi (choose for its SMA). Funding is now sought to develop the use of these materials in NEMS, particularly in the area of novel sensors and actuators and micro- and nano-needles for drug deliver. The support of a dedicated research fellow and three post-graduate students will be requested. It is anticipated that this unique area of research will generate extensive IP. The following slides give a brief taste of our preliminary work.

Nano-NiTi Powder
TiNi nano-powder prepared by the Electro-Explosion of Wire (EEW) method has:
  • Mean particle size of 50 nm.
  • Single crystal & complex metastable structure.
  • Activation energy of 113±10% KJ/mol for sintering
  • Shape memory effect.
Sintering of Nano-NiTi
Spark plasma sintering of TiNi nano-powders gave specimens with:
  • Bulk density at 1000 °C.
  • Optimal SMA at 800 ° C.
  • Ductile mechanical properties.
Nano-Pt
Characterisation of Nano-Pt has revealed many important findings:
  • Self sintering at room temperature.
  • Start of sintering temperature less than 200 ° C.
  • 100% hardness enhancement due to nano-grain size of sintered Pt specimens.
  • Activation energy of 77.9±10% KJ/mol.
Investigation into nano-W has revealed a lower sintering temperature. In addition, sintering of nano-W with a high oxide content results in near oxide free metallic W specimens. A new mechanism has been identified and reported.

References
  1. Yongqing Fu and Christopher Shearwood, Scripta Materialia, vol.50/3 (2003) pp. 319-323.
  2. C. Shearwood, Y.Q. Fu, L. Yu, K. A. Khor, ACCEPTED, Scripta Materialia (2004).
  3. Christopher Shearwood and Yongqing Fu, SUBMITTED to Acta Materialia (2004).
  4. C. Shearwood, A.L. Teo, Y.Q. Fu, L. Yu, K. A. Khor, S. Moochhala, SUBMITTED to Scripta Materialia (2004).
  5. C. Shearwood, Y.Q. Fu, L. Yu, K. A. Khor, SUBMITTED to Material Science Letters (2004).