Liming Dai, Ph.D.

Rajib Paul, senior research associate in the Department of Mechanical and Aerospace Engineering, and Liming Dai, the Kent Hale Smith Professor in the Department of Macromolecular Science and Engineering, authored a paper titled “Interfacial aspects of carbon composites.” It was recently published in Composite Interfaces.

About the paper
Carbon-based composites bring great promise for various practical applications ranging from aviation industry, electro-chemistry to advanced miniaturized biomedical sensors. This article gives an overview of the various advanced processing of carbon materials to manipulate their interface properties for functional applications.

Read the paper.

CLEVELAND—Wearable power sources for wearable electronics are limited by the size of garments.
With that in mind, researchers at Case Western Reserve University have developed flexible wire-shaped microsupercapacitors that can be woven into a jacket, shirt or dress.
By their design or by connecting the capacitors in series or parallel, the devices can be tailored to match the charge storage and delivery needs of electronics donned.
While there’s been progress in development of those electronics—body cameras, smart glasses, sensors that monitor health, activity trackers and more—one challenge remaining is providing less obtrusive and cumbersome power sources.
“The area of clothing is fixed, so to generate the power density needed in a small area, we grew radially-aligned titanium oxide nanotubes on a titanium wire used as the main electrode,” said Liming Dai, the Kent Hale Smith Professor of Macromolecular Science and Engineering. “By increasing the surface area of the electrode, you increase the capacitance.”

An international team of scientists has developed what may be the first one-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in three dimensions.

The research holds potential for increased energy storage in high efficiency batteries and supercapacitors, increasing the efficiency of energy conversion in solar cells, for lightweight thermal coatings and more. The study was published in the online journal Science Advances.

In early testing, a three-dimensional (3D) fiber-like supercapacitor made with the uninterrupted fibers of carbon nanotubes and graphene matched or bettered—by a factor of four—the reported record-high capacities for this type of device.

Used as a counter electrode in a dye-sensitized solar cell, the material enabled the cell to convert power with up to 6.8 percent efficiency and more than doubled the performance of an identical cell that instead used an expensive platinum wire counter electrode.

Carbon nanotubes could be highly conductive along the 1D nanotube length and two-dimensional graphene sheets in the 2D plane. But the materials fall short in a three-dimensional world due to the poor interlayer conductivity, as do two-step processes melding nanotubes and graphene into three dimensions.

“Two-step processes our lab and others developed earlier lack a seamless interface and, therefore, lack the conductance sought,” said Liming Dai, the Kent Hale Smith Professor of Macromolecular Science and Engineering at Case Western Reserve University and a leader of the research.

“In our one-step process, the interface is made with carbon-to-carbon bonding so it looks as if it’s one single graphene sheet,” Dai said. “That makes it an excellent thermal and electrical conductor in all planes.”

Dai has worked for nearly four years with Georgia Institute of Technology’s Zhong Lin Wang, the Hightower Chair in Materials Science and Engineering, and Yong Ding, a senior research scientist; Zhenhai Xia, professor of materials science and engineering at the University of North Texas; Ajit Roy, principal materials research engineer in the Materials and Manufacturing Directorate at the Air Force Research Laboratory in Dayton; and others on a U.S. Department of Defense-Multidisciplinary University Research Initiative (MURI) program (Joycelyn Harrison, program manager). Close collaboration also was made with Yuhua Xue, a research associate at CWRU and visiting scholar from the Institute of Advanced Materials for Nano-Bio Applications, School of Ophthalmology & Optometry, Wenzhou Medical University, along with Jia Qu and Hao Chen, professors in the Wenzhou Medical University.

Consumers aren’t embracing electric cars and trucks, partly due to the dearth of charging stations required to keep them moving. Even the conservation-minded are hesitant to go electric in some states because, studies show, if fossil fuels generate the electricity, the car is no greener than one powered with an efficient gasoline.

Charging cars by solar cell would appear to be the answer. But most cells fail to meet the power requirements needed to directly charge lithium-ion batteries used in today’s all-electric and plug-in hybrid electric vehicles.

Researchers at Case Western Reserve University, however, have wired four perovskite solar cells in series to enhance the voltage and directly photo-charged lithium batteries with 7.8 percent efficiency—the most efficient reported to date, the researchers believe.

The research, published in the Aug. 27 issue of Nature Communications, holds promise for cleaner transportation, home power sources and more.
“We found the right match between the solar cell and battery,” said Liming Dai, the Kent Hale Smith Professor of macromolecular science and engineering and leader of the research. “Others have used polymer solar cells to charge lithium batteries, but not with this efficiency.”

In fact, the researchers say their overall photoelectric conversion and storage outperformed all other reported couplings of a photo-charging component with lithium-ion batteries, flow batteries or super-capacitors.

Researchers claim to have hit on the right combination of solar cell type and battery to charge an electric vehicle battery with higher efficiency than ever before. The team behind the research says the system could soon make it possible to attach small cells to a car that will charge the vehicle while being driven – on a sunny day, at least.

The researchers from Case Western Reserve University wired four perovskite solar cells in series to directly photo-charge lithium batteries with 7.8 percent efficiency, which they believe to be the most efficient configuration reported to date.

“We found the right match between the solar cell and battery… Others have used polymer solar cells to charge lithium batteries, but not with this efficiency,” said Liming Dai, the leader of the research team, adding that the coupling appears to have outperformed all other reported pairings of photo-charging components and compatible batteries or super-capacitors.

Perovskite has been one of the most promising solar cell technologies to emerge of late, thanks to its ability to convert a broader spectrum of sunlight to electricity when compared to silicon-based cells. The crystalline material has a structure identical to the mineral of the same name, and its potential for highly efficient power conversion and a quick payback in terms of energy savings over traditional power sources have made it one of the fastest growing sectors in the solar power field. As a sort of added bonus, it has even been found to emit light at night, functioning similar to an LED.

CLEVELAND—Researchers from Case Western Reserve University and the University of North Texas have made what they believe is the first metal-free bifunctional electrocatalyst that performs as well or better than most metal and metal oxide electrodes in zinc-air batteries.
Zinc-air batteries are expected to be safer, lighter, cheaper and more powerful and durable than lithium-ion batteries common in mobile phones and laptops and increasingly used in hybrid and electric cars.
This carbon-based catalyst works efficiently in both the oxygen reduction reaction and oxygen evolution reaction, making the battery rechargeable. The catalyst is also inexpensive, easy to make and more ecological than most of the alternative materials.
The research is in the online edition of Nature Nanotechnology.
“With batteries, cost is always an issue and metal-free catalysts can reduce cost while improving performance,” said Liming Dai, professor of macromolecular science and engineering at Case Western Reserve University and senior author of the study. “These batteries could be used in computers, data stations, for lighting— anyplace batteries are used now.”

CLEVELAND—For nearly half a century, scientists have been trying to replace precious metal catalysts in fuel cells. Now, for the first time, researchers at Case Western Reserve University have shown that an inexpensive metal-free catalyst performs as well as costly metal catalysts at speeding the oxygen reduction reaction in an acidic fuel cell.
The carbon-based catalyst also corrodes less than metal-based materials and has proved more durable.
The findings are major steps toward making low-cost catalysts commercially available, which could, in turn, reduce the cost to generate clean energy from PEM fuel cells—the most common cell being tested and used in cars and stationary power plants. The study is published online in the journal Science Advances.
“This definitely should move the field forward,” said Liming Dai, the Kent Hale Smith Professor of macromolecular science and engineering at Case Western Reserve and senior author of the research. “It’s a major breakthrough for commercialization.”

Mixing a little dry ice and a simple industrial process cheaply mass-produces high-quality graphene nanosheets, researchers in South Korea and Case Western Reserve University report.

Graphene, which is made from graphite, the same stuff as “lead” in pencils, has been hailed as the most important synthetic material in a century. Sheets conduct electricity better than copper, heat better than any material known, are harder than diamonds yet stretch.

Scientists worldwide speculate graphene will revolutionize computing, electronics and medicine but the inability to mass-produce sheets has blocked widespread use.

A description of the new research will be published the week of March 26 in the online Early Edition of the Proceedings of the National Academy of Sciences. The story is embargoed until Monday, March 26, 2012 at 3 p.m. U.S. Eastern time.

Jong-Beom Baek, professor and director of the Interdisciplinary School of Green Energy/Advanced Materials & Devices, Ulsan National Institute of Science and Technology, Ulsan, South Korea, led the effort.
“We have developed a low-cost, easier way to mass produce better graphene sheets than the current, widely-used method of acid oxidation, which requires the tedious application of toxic chemicals,” said Liming Dai, a Kent Hale Smith professor of macromolecular science and engineering at Case Western Reserve and a co-author of the paper.

A national team of experts, led by a Case Western Reserve University researcher, has received a multi-million-dollar grant to bring unrivaled qualities found in one- and two-dimensional nanomaterials into three dimensions. The scientists’ goal is to produce new materials for a host of uses, ranging from high-efficiency batteries, ultracapacitors, fuel cells and hydrogen storage devices to lightweight thermal coatings for hypersonic jets, multifunctional materials for aerospace, and more.

The team, from five universities, two government research institutes and a private company, has been awarded a Department of Defense Multidisciplinary University Research Initiative grant totaling more than $7 million over five years.The grant comes through the Air Force Office of Scientific Research.  There, Joycelyn Harrison is the program manager, Ajit Roy from the Air Force Research Laboratory leads the technical advisory board.

Recent theoretical studies and computer modeling, carried out by Roy and co-workers at Wright-Patterson Air Force Base and others elsewhere, have predicted great promise for three-dimensional (3D) pillared carbon nanomaterials, but so far, no one has been able to make them with controlled and repeatable junction properties of this 3-D nanomaterials, said Liming Dai, the Kent Hale Smith professor of macromolecular science and engineering at Case Western Reserve. Dai is also director of the Center of Advanced Science and Engineering for Carbon (CASE4Carbon), and principal investigator on the grant.

“This requires a multi-university effort,” he said

Catalysts made of carbon nanotubes dipped in a polymer solution equal the energy output and otherwise outperform platinum catalysts in fuel cells, a team of Case Western Reserve University engineers has found.
The researchers are certain that they’ll be able to boost the power output and maintain the other advantages by matching the best nanotube layout and type of polymer.

But already they’ve proved the simple technique can knock down one of the major roadblocks to fuel cell use: cost.
Platinum, which represents at least a quarter of the cost of fuel cells, currently sells for about $65,000 per kilogram. These researchers say their activated carbon nanotubes cost about $100 per kilogram.

Their work is published in the online edition of Journal of the American Chemical Society at http://pubs.acs.org/doi/full/10.1021/ja1112904.

“This is a breakthrough,” said Liming Dai, a professor of chemical engineering and the research team leader.

The efficiency of catalyzing the oxygen reduction reaction (ORR) – the process that breaks the bonds of oxygen molecules – to a large degree determines the electrochemical performance of fuel cells. Platinum and platinum-based composites have long been considered as the most efficient ORR catalysts. Platinum’s drawback, besides its high cost, has been its lack of stability once it is becomes active inside a fuel cell.

In their search for practically viable non-precious metal ORR catalysts, researchers have also been investigating vertically-aligned nitrogen-containing carbon nanotubes (VA-NCNTs). We reported on this research back in 2009 (“Nitrogen-doped carbon nanotube catalyst systems for low-cost fuel cells”). In this earlier work, the research group of Liming Dai (at that time at the University of Dayton, now Kent Hale Smith Professor in the Department of Chemical Engineering at Case Western Reserve University), showed that these metal-free VA-NCNTs catalyze a four-electron ORR process with a much higher electrocatalytic activity, more resistant to CO-poisoning, and better long-term operation stability even than that of commercially available or similar platinum-based electrodes in alkaline electrolytes.

“The substantially improved catalytic performance for the VA-NCNT catalyst was attributed to the electron-accepting ability of the chemically-bonded nitrogen atoms, which creates net positive charge on adjacent conjugated carbon atoms to facilitate the chemical adsorption of oxygen and to readily attract electrons from the anode for facilitating the ORR,” Dai explains to Nanowerk.