Rice University – Flexible insulator offers high strength and superior thermal conduction – Applications for Flexible Electronics and Energy Storage


 

flexible insulator offers high strength and superior thermal conduction
Rice University research scientist M.M. Rahman holds a flexible dielectric made of a polymer nanofiber layer and boron nitride. The new material stands up to high temperatures and could be ideal for flexible electronics, energy storage and electric devices where heat is a factor. Credit: Jeff Fitlow/Rice University

A nanocomposite invented at Rice University’s Brown School of Engineering promises to be a superior high-temperature dielectric material for flexible electronics, energy storage and electric devices.

The nanocomposite combines one-dimensional  nanofibers and two-dimensional  nanosheets. The nanofibers reinforce the self-assembling material while the “white graphene” nanosheets provide a thermally conductive network that allows it to withstand the heat that breaks down common dielectrics, the polarized insulators in batteries and other devices that separate positive and negative electrodes.

The discovery by the lab of Rice  scientist Pulickel Ajayan is detailed in Advanced Functional Materials.

Research scientist M.M. Rahman and postdoctoral researcher Anand Puthirath of the Ajayan lab led the study to meet the challenge posed by next-generation electronics: Dielectrics must be thin, tough, flexible and able to withstand .

“Ceramic is a very good dielectric, but it is mechanically brittle,” Rahman said of the common material. “On the other hand, polymer is a good dielectric with good mechanical properties, but its thermal tolerance is very low.”

Boron  is an electrical insulator, but happily disperses heat, he said. “When we combined the polymer nanofiber with boron nitride, we got a material that’s mechanically exceptional, and thermally and chemically very stable,” Rahman said.

A lab video shows how quickly heat disperses from a composite of a polymer nanoscale fiber layer and boron nitride nanosheets. When exposed to light, both materials heat up, but the plain polymer nanofiber layer on the left retains the heat far longer than the composite at right. Credit: Ajayan Research Group/Rice University

The 12-to-15-micron-thick material acts as an effective heat sink up to 250 degrees Celsius (482 degrees Fahrenheit), according to the researchers. Tests showed the polymer nanofibers-boron nitride combination dispersed heat four times better than the polymer alone.

In its simplest form, a single layer of polyaramid nanofibers binds via van der Waals forces to a sprinkling of boron nitride flakes, 10% by weight of the final product. The flakes are just dense enough to form a heat-dissipating network that still allows the composite to retain its flexibility, and even foldability, while maintaining its robustness. Layering polyaramid and boron nitride can make the material thicker while still retaining flexibility, according to the researchers.

“The 1D polyaramid  has many interesting properties except thermal conductivity,” Rahman said. “And  nitride is a very interesting 2-D material right now. They both have different independent properties, but when they are together, they make something very unique.”

Rahman said the material is scalable and should be easy to incorporate into manufacturing.


Explore further

New material to pave the way for more efficient electronic devices


More information: Muhammad M. Rahman et al. Fiber Reinforced Layered Dielectric Nanocomposite, Advanced Functional Materials (2019). DOI: 10.1002/adfm.201900056

Journal information: Advanced Functional Materials
Provided by Rice University
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Rice University: NEWT (Nano Enabled Water Treatment) Reusable water-treatment particles effectively eliminate BPA


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Rice University researchers have enhanced micron-sized titanium dioxide particles to trap and destroy BPA, a water contaminant with health implications. Cyclodextrin molecules on the surface trap BPA, which is then degraded by reactive …more

Rice University scientists have developed something akin to the Venus’ flytrap of particles for water remediation.

The research is detailed in the American Chemical Society journal Environmental Science & Technology.

BPA is commonly used to coat the insides of food cans, bottle tops and  supply lines, and was once a component of baby bottles. While BPA that seeps into food and drink is considered safe in low doses, prolonged exposure is suspected of affecting the health of children and contributing to high blood pressure.

The good news is that reactive oxygen species (ROS) – in this case, hydroxyl radicals – are bad news for BPA. Inexpensive titanium dioxide releases ROS when triggered by ultraviolet light. But because oxi-dating molecules fade quickly, BPA has to be close enough to attack.

That’s where the trap comes in.

Close up, the spheres reveal themselves as flower-like collections of titanium dioxide petals. The supple petals provide plenty of surface area for the Rice researchers to anchor cyclodextrin molecules.

Reusable water-treatment particles effectively eliminate BPA
“Petals” of a titanium dioxide sphere enhanced with cyclodextrin as seen under a scanning electron microscope. When triggered by ultraviolet light, the spheres created at Rice University are effective at removing bisphenol A contaminants from water. Credit: Alvarez Lab

Cyclodextrin is a benign sugar-based molecule often used in food and drugs. It has a two-faced structure, with a hydrophobic (water-avoiding) cavity and a hydrophilic (water-attracting) outer surface. BPA is also hydrophobic and naturally attracted to the cavity. Once trapped, ROS produced by the spheres degrades BPA into harmless chemicals.

In the lab, the researchers determined that 200 milligrams of the spheres per liter of contaminated water degraded 90 percent of BPA in an hour, a process that would take more than twice as long with unenhanced titanium dioxide.

0629_NEWT-log-lg-310x310The work fits into technologies developed by the Rice-based and National Science Foundation-supported Center for Nanotechnology-Enabled Water Treatment because the spheres self-assemble from titanium dioxide nanosheets.

“Most of the processes reported in the literature involve nanoparticles,” said Rice graduate student and lead author Danning Zhang. “The size of the particles is less than 100 nanometers. Because of their very small size, they’re very difficult to recover from suspension in water.”

The Rice particles are much larger. Where a 100-nanometer particle is 1,000 times smaller than a human hair, the enhanced  is between 3 and 5 microns, only about 20 times smaller than the same hair. “That means we can use low-pressure microfiltration with a membrane to get these particles back for reuse,” Zhang said. “It saves a lot of energy.”
Reusable water-treatment particles effectively eliminate BPA
Rice graduate student Danning Zhang, who led the development of a particle that attracts and degrades contaminants in water, checks a sample in a Rice environmental lab. Credit: Jeff Fitlow

Because ROS also wears down cyclodextrin, the spheres begin to lose their trapping ability after about 400 hours of continued ultraviolet exposure, Zhang said. But once recovered, they can be easily recharged.

“This new material helps overcome two significant technological barriers for photocatalytic water treatment,” Alvarez said. “First, it enhances treatment efficiency by minimizing scavenging of ROS by non-target constituents in water. Here, the ROS are mainly used to destroy BPA.

“Second, it enables low-cost separation and reuse of the catalyst, contributing to lower treatment cost,” he said. “This is an example of how advanced materials can help convert academic hypes into feasible processes that enhance water security.”

 Explore further: Mat baits, hooks and destroys pollutants in water

More information: Danning Zhang et al. Easily-recoverable, micron-sized TiO2 hierarchical spheres decorated with cyclodextrin for enhanced photocatalytic degradation of organic micropollutants, Environmental Science & Technology (2018). DOI: 10.1021/acs.est.8b04301

 

Win-Win Collaborations – Derisking Advanced Technology Commercialization: YouTube Video from David Lazovsky, Founder of Intermolecular


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David Lazovsky, Founder of Intermolecular, addresses the audience of the Advanced Materials Commercialization Summit 2017, speaking on Win-Win Collaborations: De-risking Advanced Technology Commercialization. Read More About Intermolecular

” … We sought to establish collaborative development programs with the Companies that were the end Producers.” – David Lazovsky, Founder of Intermolecular

 

GNT US Tenka Energy“In the end you cannot “commercialize” technology (only) … you can only commercialize a Product  (technology+application) that can be produced and scaled economically into the Marketplace. You must find a way to build a bridge to span the gap between ‘Discovery, Proof of Concept, Prototype and Scaling to Funding (Finance), Market Integration and Acceptance.”

– Bruce W. Hoy, CEO of Genesis Nanotechnology, Inc.

Researchers Develop Novel Two-Step CO2 Conversion Technology – Could aid in the production of valuable chemicals and fuels


CO2 Help U Delaware 181490_webUD Professor Feng Jiao’s team constructed an electrolyser, pictured here, to conduct their novel two-step conversion process.

 

A team of researchers at the University of Delaware’s Center for Catalytic Science and Technology (CCST) has discovered a novel two-step process to increase the efficiency of carbon dioxide (CO2) electrolysis, a chemical reaction driven by electrical currents that can aid in the production of valuable chemicals and fuels.

The results of the team’s study were published Monday, Aug. 20 in Nature Catalysis.

The research team, consisting of Feng Jiao, associate professor of chemical and biomolecular engineering, and graduate students Matthew Jouny and Wesley Luc, obtained their results by constructing a specialized three-chambered device called an electrolyser, which uses electricity to reduce CO2 into smaller molecules.

Compared to fossil fuels, electricity is a much more affordable and environmentally-friendly method for driving chemical processes to produce commercial chemicals and fuels. These can include ethylene, which is used in the production of plastics, and ethanol, a valuable fuel additive.

“This novel electrolysis technology provides a new route to achieve higher selectivities at incredible reaction rates, which is a major step towards commercial applications,” said Jiao, who also serves as associate director of CCST.

Whereas direct CO2 electrolysis is the standard method for reducing carbon dioxide, Jiao’s team broke the electrolysis process into two steps, reducing CO2 into carbon monoxide (CO) and then reducing the CO further into multi-carbon (C2+) products. This two-part approach, said Jiao, presents multiple advantages over the standard method.

“By breaking the process into two steps, we’ve obtained a much higher selectivity towards multi-carbon products than in direct electrolysis,” Jiao said. “The sequential reaction strategy could open up new ways to design more efficient processes for CO2 utilization.”

Electrolysis is also driving Jiao’s research with colleague Bingjun Xu, assistant professor of chemical and biomolecular engineering. In collaboration with researchers at Tianjin University in China, Jiao and Xu are designing a system that could reduce greenhouse gas emissions by using carbon-neutral solar electricity.

“We hope this work will bring more attention to this promising technology for further research and development,” Jiao said. “There are many technical challenges still be solved, but we are working on them!”

All-in-one light-driven water splitting with a novel nanocatalyst (photocatalytic splitting of H2O molecules)


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Solar-powered water splitting is a promising means of generating clean and storable energy. A novel catalyst based on semiconductor nanoparticles has now been shown to facilitate all the reactions needed for “artificial photosynthesis”.

In the light of global climate change, there is an urgent need to develop efficient ways of obtaining and storing power from renewable energy sources. The photocatalytic splitting of water into hydrogen fuel and oxygen provides a particularly attractive approach in this context. However, efficient implementation of this process, which mimics biological photosynthesis, is technically very challenging, since it involves a combination of processes that can interfere with each other.
Now, LMU physicists led by Dr. Jacek Stolarczyk and Professor Jochen Feldmann, in collaboration with chemists at the University of Würzburg led by Professor Frank Würthner, have succeeded in demonstrating the complete splitting of water with the help of an all-in-one catalytic system for the first time.
Their new study appears in the journal Nature Energy (“All-in-one visible-light-driven water splitting by combining nanoparticulate and molecular co-catalysts on CdS nanorods”).
solar-powered-water-splitting-device-incorporating-two-separateTechnical methods for the photocatalytic splitting of water molecules use synthetic components to mimic the complex processes that take place during natural photosynthesis.
In such systems, semiconductor nanoparticles that absorb light quanta (photons) can, in principle, serve as the photocatalysts. Absorption of a photon generates a negatively charged particle (an electron) and a positively charged species known as a ‘hole’, and the two must be spatially separated so that a water molecule can be reduced to hydrogen by the electron and oxidized by the hole to form oxygen.
“If one only wants to generate hydrogen gas from water, the holes are usually removed rapidly by adding sacrificial chemical reagents,” says Stolarczyk. “But to achieve complete water splitting, the holes must be retained in the system to drive the slow process of water oxidation.”
The problem lies in enabling the two half-reactions to take place simultaneously on a single particle – while ensuring that the oppositely charged species do not recombine. In addition, many semiconductors can be oxidized themselves, and thereby destroyed, by the positively charged holes.

Nanorods with spatially separated reaction sites

“We solved the problem by using nanorods made of the semiconducting material cadmium sulfate, and spatially separated the areas on which the oxidation and reduction reactions occurred on these nanocrystals,” Stolarczyk explains.
The researchers decorated the tips of the nanorods with tiny particles of platinum, which act as acceptors for the electrons excited by the light absorption. As the LMU group had previously shown, this configuration provides an efficient photocatalyst for the reduction of water to hydrogen. The oxidation reaction, on the other hand, takes place on the sides of the nanorod.
To this end, the LMU researchers attached to the lateral surfaces a ruthenium-based oxidation catalyst developed by Würthner‘s team. The compound was equipped with functional groups that anchored it to the nanorod.
“These groups provide for extremely fast transport of holes to the catalyst, which facilitates the efficient generation of oxygen and minimizes damage to the nanorods,” says Dr. Peter Frischmann, one of the initiators of the project in Würzburg.
The study was carried out as part of the interdisciplinary project “Solar Technologies Go Hybrid” (SolTech), which is funded by the State of Bavaria.
“SolTech’s mission is to explore innovative concepts for the conversion of solar energy into non-fossil fuels,” says Professor Jochen Feldmann, holder of the Chair of Photonics and Optoelectronics at LMU.

 

“The development of the new photocatalytic system is a good example of how SolTech brings together the expertise available in diverse disciplines and at different locations. The project could not have succeeded without the interdisciplinary cooperation between chemists and physicists at two institutions,” adds Würthner, who, together with Feldmann, initiated SolTech in 2012.

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Source: CeNS Center for NanoScience

3 Questions for Innovating the Clean Energy Economy (MIT Energy Initiative)


daniel-kammen-mit-energy-initiative-mitei-2018_0Daniel Kammen, professor of energy at the University of California at Berkeley, spoke on clean energy innovation and implementation in a talk at MIT. Photo: Francesca McCaffrey/MIT Energy Initiative

Daniel Kammen of the University of California at Berkeley discusses current efforts in clean energy innovation and implementation, and what’s coming next.

Daniel Kammen is a professor of energy at the University of California at Berkeley, with parallel appointments in the Energy and Resources Group (which he chairs), the Goldman School of Public Policy, and the Department of Nuclear Science and Engineering.

Recently, he gave a talk at MIT examining the current state of clean energy innovation and implementation, both in the U.S. and internationally. Using a combination of analytical and empirical approaches, he discussed the strengths and weaknesses of clean energy efforts on the household, city, and regional levels. The MIT Energy Initiative (MITEI) followed up with him on these topics.

Q: Your team has built energy transition models for several countries, including Chile, Nicaragua, China, and India. Can you describe how these models work and how they can inform global climate negotiations like the Paris Accords?

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A: My laboratory has worked with three governments to build open-source models of the current state of their energy systems and possible opportunities for improvement. This model, SWITCH , is an exceptionally high-resolution platform for examining the costs, reliability, and carbon emissions of energy systems as small as Nicaragua’s and as large as China’s. The exciting recent developments in the cost and performance improvements of solar, wind, energy storage, and electric vehicles permit the planning of dramatically decarbonized systems that have a wide range of ancillary benefits: increased reliability, improved air quality, and monetizing energy efficiency, to name just a few. With the Paris Climate Accords placing 80 percent or greater decarbonization targets on all nations’ agendas (sadly, except for the U.S. federal government), the need for an “honest broker” for the costs and operational issues around power systems is key.

Q: At the end of your talk, you mentioned a carbon footprint calculator that you helped create. How much do individual behaviors matter in addressing climate change?

A: The carbon footprint, or CoolClimate project, is a visualization and behavioral economics tool that can be used to highlight the impacts of individual decisions at the household, school, and city level. We have used it to support city-city competitions for “California’s coolest city,” to explore the relative impacts of lifetime choices (buying an electric vehicle versus or along with changes of diet), and more.

Q: You touched on the topic of the “high ambition coalition,” a 2015 United Nations Climate Change Conference goal of keeping warming under 1.5 degrees Celsius. Can you expand on this movement and the carbon negative strategies it would require?

A: As we look at paths to a sustainable global energy system, efforts to limit warming to 1.5 degrees Celsius will require not only zeroing out industrial and agricultural emissions, but also removing carbon from the atmosphere. This demands increasing natural carbon sinks by preserving or expanding forests, sustaining ocean systems, and making agriculture climate- and water-smart. One pathway, biomass energy with carbon capture and sequestration, has both supporters and detractors. It involves growing biomass, using it for energy, and then sequestering the emissions.

This talk was one in a series of MITEI seminars supported by IHS Markit.