Design & Simulation / Heat Exchangers / Reaction & Synthesis / Heat transfer fluids

Nanoparticles Remain Big Attraction

Myriad potential applications are emerging but safety testing remains a concern

By Seán Ottewell, Editor at Large

Nanotechnology is driving important innovations at companies such as Dow, BASF and Solvay. Academia also is coming up with industrially relevant nanoparticle-based advances — for instance, heat transfer fluids with significantly enhanced thermal conductivity.

Dow Chemical Benelux, Terneuzen, the Netherlands, has been working with Utrecht University, Utrecht, the Netherlands, for two years now to develop a process to produce ethylene and propylene from fast-growing trees and grasses.

The process relies on new kinds of iron catalysts that consist of tiny nanoparticles separated from each other on carbon nanofibers. In laboratory tests, the catalysts have proven highly effective at converting a biomass-derived synthesis gas into ethylene and propylene without producing a large amount of unwanted methane, which can be a byproduct of iron-based catalysis processes, notes the company.

“Dow Chemical Benelux continues to collaborate in the development of catalysts with the University of Utrecht to produce lower olefins that can be used for polymer manufacturing from syngas. This is a large program of national importance for the Netherlands and involves industry, academic and government partners. The nature of the newly developed catalysts consists of promoted nanoparticles dispersed on weakly interactive supports. Special interest is now focused on the physical properties of the iron nanoparticles and how they impact the performance of the catalyst,” says Wiltrud Treffenfeldt, vice president of R&D for Europe, the Middle East and Asia.


Meanwhile, Dow also is halfway through a six-year, $10-million strategic partnership with the University of Queensland, Brisbane, Australia.

“We currently have multiple ongoing collaborations with the university. These reach many areas of relevancy to Dow including the development of bio routes to monomers, the development of new materials with applications within the electronic material business and also exploration programs on new routes to low-cost carbon fiber,” notes Treffenfeldt.

Three key focuses here are high-performance cathode materials for lithium-ion batteries, circuitry for lithium-ion batteries, and the use of genetics to reprogram bacteria to manufacture important chemicals.

“Dow has many ongoing collaborations with partners where the performance of the materials or the transformation is governed at the nano scale. Some examples are new materials being developed with the University of Illinois [Champaign, Ill.] with potential application in the electronic materials industry and new systems with potential application in controlled release of actives. Other examples include studies of materials that self-assemble at the nano scale — with relevancy to water purification applications,” adds Treffenfeldt.

CLEAR SUCCESS
BASF, Ludwigshafen, Germany, also has a wide variety of initiaves involving nanomaterials. For instance, the firm has spent more than five years developing its iGloss clearcoat automobile gloss coating. Traditionally such coatings are polymers but iGloss combines two different materials in a nanostructured hybrid.

Between 90 and 95% of the hybrid material, depending on the area of application, consists of organic material that forms the paint matrix. This makes the finish flexible and elastic and ensures a high level of weathering resistance. The remainder consists of inorganic silicate nanoclusters that are embedded in the organic matrix. These are distributed uniformly and densely throughout the coating and are particularly hard and scratch resistant.

The organic and inorganic components are covalently bonded and very elastic. This allows the clearcoat to immediately spring back to around 90% after, for example, abrasion. Conventional clearcoats typically achieve 70% elastic recovery in the same situation. Also, with iGloss, microscratches that occur are significantly flatter and, therefore, less visible.

Automakers worldwide now are in the process of implementing the technology.

BASF also is pressing ahead with its long-standing work on organic light emitting diodes (OLEDs). Displays made from OLEDs render colors more vividly than the liquid crystal displays used today, and can be more energy efficient as well as thin and flexible.

The company also is exploring the diodes for lighting applications. OLEDs consume only half as much electricity as conventional energy-saving lamps and reportedly are more energy-efficient than inorganic LEDs. Moreover, they offer new design options in lighting technology.

The Smart Forvision concept automobile (Figure 1), developed in collaboration with Daimler Benz, showcases the potential application of OLEDs for lighting. The car also features other nanotechnologies, including infrared reflective films for better heat management, high-performance foams for improved insulation, high-performance composites for lighter-weight construction, and transparent solar cells for power generation.

The company also remains committed to its work with metal organic framework (MOF) materials. These crystalline nanostructures allow storage of natural gas and other gases such as hydrogen. They also can be used in other applications including gas separation and purification and in catalysis.

“Based on our current activities, the benefits specific to natural gas storage are potentially increased vehicle range and the ability to operate vehicle fuel storage tanks at lower pressures. Currently, we are testing a range of light- and heavy-duty vehicles in the U.S.A. and Europe that are equipped with MOF materials-based fuel systems,” says a spokesperson.

Another innovation has come in the form of Master X-Seed nanocrystals, which accelerate the hardening process of concrete and reduce carbon emissions. The calcium silicate hydrate crystals, each with a diameter of only a few nanometers, mix very uniformly into the concrete; as the concrete hardens, other molecules from the concrete mixture attach to them. The resulting crystals grow more densely and finally interlock to form the compact cement stone.

A BUSINESS DEVELOPMENT PLATFORM
For Solvay, Brussels, Belgium, nanotechnologies make up one of four new-business-development platforms that together account for more than 20% of the company’s annual R&D budget. The three primary areas of focus are: electronics and information technology, manufacturing and materials, and healthcare and life sciences.

Solvay can point to its Zeosil range of highly dispersible silica as one notable nano-related success. Its primary use is in tires, where its ability to reduce rolling resistance decreases fuel consumption by 5–7%. The line, which also is used in various industrial applications, plus personal care and nutrition products, generated net sales of €416 million ($518 million) last year.

The company now has launched a new generation known as Zeosil Premium, which can further improve tire efficiency and performance.

Solvay also is active in the field of OLEDs. It particularly is interested in using them to deliver high-quality diffuse light from thin and flexible tiles that one day could be integrated into ceilings, walls, windows and other locations.

It is working in collaboration with the Holst Centre, an independent R&D organization based in Eindhoven, the Netherlands, to develop large area OLEDs. One breakthrough has been the ability to deposit OLED layers by solution processing rather than conventional vacuum deposition — a move that brings the use of printing technologies to manufacture OLEDs a step closer.

The two now are developing a second generation of demonstrators, which they hope will lead to low-cost solution-processed OLED lighting tiles on flexible plastic foils.

SAETY IS NO SMALL MATTER
Nanotechnology was the theme of BASF’s annual research conference in May. One of the speakers was Robert Landsiedel, Ludwigshafen-based head of short-term toxicology. His talk “Safety Research for a Responsible Use of Nanomaterials” focused on the questions posed by nanoparticles, e.g.: Does larger surface area lead to higher reactivity? Does their small size enable nanoparticles to defeat barriers, for example the skin? What is the best way to deal with the genuinely unique properties observed in some nanoparticles?

Landsiedel pointed out that BASF began its first research project into the safety of nanoparticles in 2004 and since then has conducted more than 150 studies on nanomaterial toxicity. The company has been involved with more than 25 research projects with organizations as diverse as the European Commission’s Joint Research Center, the Finnish Institute of Occupational Health, the U.S. Environmental Protection Agency, Bayer MaterialScience and the Italian National Agency for New Technology, he noted.

Testing methods cited in current guidelines from the Organization for Economic Cooperation and Development generally are suitable for nanomaterials, Landsiedel concluded. However, safety assessments should consider the lifecycle of the material (use, release) as well as the biological pathway (uptake, biopersistence and biological effect), and that the long-term effects still need further investigation, he cautioned.

This last point is highlighted in a recent article by toxicologist Harald F. Krug, a professor at the Swiss Federal Laboratories for Materials Science and Technology (EMPA), Zurich, in Angewandte Chemie International Edition. It casts doubts on the findings of thousands of studies on the risks associated with nanoparticles. His article is based on a re-evaluation of these studies, many of which he found to be poorly executed and practically useless for risk assessments.

In an effort to overcome these issues, EMPA is collaborating with groups such as the Powder Technology Laboratory of the Institute of Materials at Ecole Polytechnique Fédérale de Lausanne, Switzerland, the U.S. National Institute of Standards and Technology, the European Commission’s Joint Research Center, the Korean Institute of Standards and Science, and industrial partners in a new NanoScreen program. It is expected to yield a set of prevalidated methods for laboratory experiments over the next few years (Figure 2).
     
“Thanks to these methods and test substances, international labs will be able to compare, verify and, if need be, improve their experiments,” notes Peter Wick, head of EMPA’s laboratory for materials-biology interactions.


ottewell.jpgSeán Ottewell is Chemical Processing's Editor at Large. You can email him at sottewell@putman.net.