Enginuity 2009

Expanding Potential: Nanocomposites

Nanocomposites labNanotechnology is versatile science. The field is recognized as one of the most promising avenues of technology development for the 21st century. In the materials industry, the development of ceramic and polymer nanocomposites is a rapidly expanding, multidisciplinary research activity.

Polymer nanocomposites are the center of focus for researcher Zhanhu “John” Guo, assistant professor of chemical engineering, because of their unique properties, multifunctionalities and wide potential for application in many fields.

Guo earned his Ph.D. degree in chemical engineering from Louisiana State University in 2005 and finished his postdoctoral work on polymer nanocomposites in the Department of Mechanical and Aerospace Engineering at the University of California, Los Angeles, 2005-2008.

Nanocomposites can be defined as multiphase solid materials in which at least one of the phases has a dimension of less than 100 nanometers. A nanometer is equal to one billionth of a meter.

Because nanocomposites can have unique physicochemical properties—such as mechanical, magnetic, electrical, electronic, optical, thermoelectric, electrochemical and catalytic—different from those of the component materials, their development opens up exciting areas of opportunity.

High-particle loading is required for certain industrial applications, such as electromagnetic wave absorbers, photovoltaic cells (solar cells), photo detectors and smart structures. Nanoparticle cores with a polymer make possible many industrial applications such as nanofluids and magnetic resonance imaging.

Unique challenges that face researchers of polymer nanocomposites, especially for applications with high-particle loading, are particle dispersion and the interaction strength between the polymer matrix and the nanofillers, Guo said. The agglomerated nanofillers and the poorly linked polymernanoparticle will serve as defects and can result in undesirable effects such as low mechanical properties.

To solve these challenges in the creation of unique polymer nanocomposites, Guo built Lamar’s Integrated Composites Laboratory (ICL). His research interests include advanced materials preparation, characterization and applications. Guo has developed numerous unique methods to prepare polymer nanocomposites reinforced with various nanoparticles encompassing ceramics, semiconductors, and magnetic metals. The scientific results have been published in leading scientific journals and have resulted in two patents and a field technical disclosure.

Guo’s investigations include the mechanical, electrical, optical, magnetic, electronic, electrocatalytic, photochromic, electrochromic and electron transport phenomena in the nanoscale materials. Through introducing the strong interfacial interaction between the nanoparticles and the polymer matrix and achieving uniform particle dispersion with coupling agent/surfactant, he has achieved a series of strengthened polymer nanocomposites with the matrix encompassing thermoplastics, rubbers and thermosetting.

Guo also has extensive experience in the wet chemical synthesis of metallic nanoparticles, air-sensitive nanoparticle handling, nanoparticle surface-treatment with either coupling agent, surfactant or monomer (also called particle functionalization), in-situ polymeric stabilization of metallic nanoparticles, nanoparticle dispersion in solvents and liquid polymer solutions for integrated composites fabrication, and electron transport and magnetic property testing. All these processes not only improved the nanoparticle dispersion quality but also enhanced the interaction between the nanoparticles and the polymer matrix, having a significant effect on the physicochemical properties of the polymer nanocomposites including enhanced mechanical properties, microwave absorption, electron transport, optical properties and larger coercivities.

By varying the nanoparticle spacer materials and interparticle distance, Guo and his team have shown the ability to tailor the magnetic properties and to manipulate the conductivity of the nanocomposites for microwave absorber and giant magnetoresistance (GMR) sensor applications. The microwave absorption of the magnetic nanocomposites has been evaluated exhibiting a significant weight reduction with a comparable performance. The GMR has been observed in this system, and it is the largest signal of these systems. Guo’s team is now fabricating a sensor.

Other than using commercially available ceramic and magnetic metallic nanoparticles, Guo has also developed an in-situ composite fabrication method through a wet chemical reduction method in the polymer solution. In addition, his team has built different shells surrounding the magnetic core that could have a significant effect on the biomedical, data information, national defense and energy areas.