Tag Archives: Texas Tech University

Having a blast with aluminum nanoparticles

A June 11, 2018 news item on Nanowerk announces ‘explosive’ research from the US Army Research Laboratory (ARL),

Army scientists proved a decades-old prediction that mixing TNT and novel aluminum nanoparticles can significantly enhance energetic performance. This explosive discovery is expected to extend the reach of U.S. Army firepower in battle.

Researchers from the U.S. Army Research Laboratory and Texas Tech University demonstrated up to 30-percent enhancement in the detonation velocity of the explosive TNT by adding novel aluminum nanoparticles in which the native alumina shell has been replaced with an oxidizing salt called AIH, or aluminum iodate hexahydrate.

A June 7, 2018 ARL news release (published on EurekAlert on June 11, 2018), which originated the news item, provides more detail,

The structure of the AIH-coated aluminum nanoparticles was revealed for the very first time through high resolution transmission electron (TEM) microscopy performed by ARL’s Dr. Chi-Chin Wu, a materials researcher who leads the plasma research for the lab’s Energetic Materials Science Branch in the Lethality Division [emphasis mine] of Weapons and Materials Research Directorate.

Wu said this revolutionary research offers the potential for the exploitation of aluminum and potentially other metallic nanoparticles in explosive formulations to extend the range and destructive power of Army weapons systems, a key objective of the Army’s “Long Range Precision Fires” modernization priority.

“We believe these results show tremendous promise for enhancing the detonation performance of conventional military explosives with aluminum nanoparticles for the first time,” said ARL’s Dr. Jennifer Gottfried, a physical chemist who collaborated on the research.

“It is very exciting to advance science to a point where we can harness more chemical energy from metal particles at faster timescales. This is an exciting time for transforming energy generation technology,” said Dr. Michelle L. Pantoya, the J. W. Wright Regents Chair in Mechanical Engineering and Professor at Texas Tech University.

The team found that the crystalline aluminum core was effectively protected against unwanted oxidation by the AIH shell, which appears as protruding nodules on the aluminum surface. The enhanced reactivity due to this unique morphological feature and novel core-shell structure was demonstrated by laser-induced air shock from energetic materials experiments, an innovative laboratory-scale energetic testing method developed by Gottfried. This technique involves impacting the sample with a high-energy, focused laser pulse to violently break apart the explosive molecules. The interaction of the laser with the material forms a laser-induced plasma and produces a shock wave that expands into the surrounding air. The energy released from an explosive sample can then be experimentally determined by measuring the laser-induced shock velocity with a high-speed camera.

It was predicted decades ago that aluminum nanoparticles have the potential to enhance the energetic performance of explosives and propellants because of their high energy content and potential for rapid burning. This is because they have exceptionally large surface areas compared to their total volume and a very large heat of reaction. However, the surface of the aluminum nanoparticles is naturally oxidized in air to form a thick alumina shell, typically 20% by weight, which not only lowers the energy content of the nanoparticles by reducing the amount of active aluminum, it also slows the rate of energy release because it acts as a barrier to the reaction of the aluminum with the explosive. Therefore, replacing the oxide shell, as successfully achieved by TTU, can significantly improve the explosive performance.

These preliminary joint efforts have also led to a formal research collaboration under an ARL Director’s Research Award, the fiscal 2018 External Collaboration Initiative between Wu and TTU.

After publishing two papers in high-impact scientific journals in the past year, the team is poised to pursue additional energetics research with aluminum nanoparticles by working with the U.S. Army Research, Development and Engineering Command at Picatinny Arsenal, New Jersey, and the Air Force Research Laboratory.

A ‘lethality division’, eh?

Here’s a link to and a citation for the paper,

Improving the Explosive Performance of Aluminum Nanoparticles with Aluminum Iodate Hexahydrate (AIH) by Jennifer L. Gottfried, Dylan K. Smith, Chi-Chin Wu, & Michelle L. Pantoya. Scientific Reports volume 8, Article number: 8036 (2018) DOI:10.1038/s41598-018-26390-9 Published online May 23, 2018

This paper is open access.

Using microwaves to test for carbon nanotube toxicity in soil

It’s been a while since I’ve mentioned soil or environmental testing for this this Oct. 19, 2012 news item by Karen Slyker on physorg.com, which highlights some research on environmental testing of carbon nanotubes, lets me redress the situation,

Industrial uses are growing, as are concerns that these novel nanomaterials may have negative or unintended effects on organisms and the environment. With this in mind, environmental toxicologists at Texas Tech are exploring the fate of CNTs in biological environments and their ability to accumulate in soil, plants or other organisms.

One recurring question has slowed these studies: How can anyone be certain the tiny CNTs are present in the given sample?

“It’s like a needle in a haystack,” Green said [Micah Green, assistant professor of chemical engineering]. “How can you prove the effects of the needle, if you’re not sure that it’s really in there?”

The impetus for the work initially began with a conversation between Green and Jaclyn Cañas, associate professor of environmental toxicology at The Institute for Environmental and Human Health at Texas Tech. Cañas described the problem of detecting CNTs in crop samples. Green suggested that exposing samples to microwaves could reveal the presence of even trace quantities of nanotubes.

The Texas Technical University Oct. 19, 2012 news release (which originated the news item) provides more detail about the approach,

CNTs have the unusual property of evolving extreme amounts of heat upon exposure to microwaves, much more so than typical materials. In fact, nanotube powder will quickly and spontaneously ignite if placed in a conventional kitchen microwave. Green’s idea was to expose the sample to low-power microwaves and measure the resulting increase in temperature.

Mohammad Saed, an associate professor in electrical and computer engineering, joined the team to contribute his expertise in the area of microwave physics.

Together, the three research groups successfully built a testing apparatus and proved the concepts that microwave-based heating can quantify CNT loading inside a plant sample.

The team has refined its testing protocols and extended the scope from soil testing only to including earthworms,

Continued development of the device led to a double-blind test, where a student was given samples of a specified CNT loading but was not told what the concentration was. Graduate student Fahmida Irin was principally responsible for applying the method. The double-blind test successfully duplicated the true values, and was then applied to studying the uptake of nanotubes into alfalfa plant roots grown in soil spiked with nanotubes.

“Since we started the method, we have started collaborating with other groups as well to look at the presence of nanotubes in organisms like earthworms,” Green said.

The method was recently published in a paper entitled “Detection of carbon nanotubes in biological samples through microwave-induced heating” by Irin et al. in the journal Carbon.

I’m not quite sure how to take this research. They do mention that nanotube powder will ignite in a kitchen microwave. Here’s hoping the researchers have designed an apparatus that cannot accidentally ignite carbon nanotubes in soil, plants, or earthworms.