Figure 7. Aluminum flakes Figure 8. TiO 2 /Ag Nanowires
One of the approaches used by Professor Goia is to design and develop novel milling processes capable of converting highly dispersed uniform metallic particles, which are routinely produced in his laboratory by chemical means, into high aspect ratio platelets/flakes. This preparative route was successfully used during the past two years to obtain copper and silver flakes that possess the features desired by the Army. More recently, Dr. Goia's group has developed a novel wet milling process that can 'flatten' micron size aluminum spheres in a controllable manner to yield high aspect ratio thin (~30 nm) aluminum flakes (Figure 5).
Another research direction pursued by the same group involves the formation of uniform metallic platelets in homogeneous solutions by controlling the nucleation and the growth of the metallic phase. Following this approach, Professor Goia's group has recently developed an efficient aqueous precipitation process, which generates highly dispersed Ag nanoplatelets (Figure 6).
The novel anisotropic conductive metallic particles developed can be used effectively not only in military (obscurant smokes) but in non-military applications (EMI shielding of electronic devices, decorative and/or conductive coatings, conductive thin electrodes) as well. In particular, the silver nanoflakes could represent a very promising material for the emerging inkjet printable flexible electronics applications.
Senior University Professor Partch and his group are successfully preparing materials with obscurant properties. The highest level of infrared obscuration of metallic flakes from any source so far measured by U.S. Army Aberdeen scientists have been produced in Professor Partch’s chemistry laboratory. Their extinction is over seven times (7X) the current Army standard. The processing of commercial aluminum flakes from Sigma Technologies Co. in Arizona, as well as from other companies such as Silberline and Ciba, involves chemical surface treatment followed by freeze drying. This technique yields unagglomerated dry flakes that readily disperse in air. See Figure 7. Partch’s team includes Scott Goodrich, who interned in November-December, 2005 at Sigma to facilitate flake manufacture, and Justen Schaefer who, with CAMP Chemical Engineering Professor Don Rasmussen directing, carried out the freeze drying operation. In related work, David Eno has successfully prepared nanoneedles of titanium dioxide coated with silver. See Figure 8. These will be evaluated for obscurant properties.
CAMP Professor Richard Partch Continues Work Involving Overdosed Chemical Therapeutics and Toxins
Senior University Professor Richard Partch, and recent MS recipients Adrienne Benson and Jinjin Feng from his group, continue to expand the organic chemical principle of pi-pi complexation between donor and acceptor aromatic rings for use in binding and deactivating overdosed therapeutics and biotoxins. Benson’s results using AFM, in collaboration with CAMP Physics Professor Igor Sokolov, show that the pi-pi interaction previously shown to occur in bulk solutions, including blood, can be measured on the molecular level. See Figure 9. This includes binding to pi-donor amino acid tyrosine which is located in the opening of the binding site of the highly toxic Ricin biotoxin. See Figure 10. Feng has started synthesis of pi-acceptor derivatives designed to inhibit Ricin toxicity.
Figure 9. AFM Analysis
Figure 10. Ricin Binding Site