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Topic Name: New super paper with excellent mechanical properties and chemical tunability

Category: Advanced Materials

Research persons: Rodney Ruoff, SonBinh Nguyen, Sasha Stankovich, Dmitriy Dikin

Location: Northwestern university,Technology Transfer Program
1800 Sherman Avenue - Suite 504,Evanston, IL 60201,
Phone: (847)491-3005,Fax: (847)491-3625, United States

Details

Researchers have developed a remarkably simple way to convert ordinary graphite particles into very thin but superstrong sheets that are tougher than steel and as flexible as carbon fiber but can be made much more cheaply. The discovery could spawn entirely new types of materials for applications as diverse as protective coatings, electronic components, batteries, and fuel cells.
For tensile strength and stiffness, carbon is king. So it's no surprise that scientists have been working for years to develop ways to add Element 6 to composite materials for aircraft fuselages, military vehicles, and even racing bicycles and tennis rackets. Even bigger payoffs are possible by constructing carbon materials at microscopic scales, yielding the strongest materials of all. Researchers have made some progress building structures called carbon nanotubes--whose single-layer atomic structure is tightly bound and therefore super rigid--but the tubes are expensive to manufacture and so far can only be used in tiny amounts
Now, a research team from Northwestern University in Evanston, Illinois, has assembled particles of graphene oxide, a form of graphite and a cousin of diamonds, into very thin sheets that are even stronger than those made of the nanotubes. The process works like this: the team disperses graphene oxide particles in specially treated water and then draws the mixture through a filter membrane. The water somehow causes the particles to bind into a paperlike layer on the filter's surface, the researcher reports in tomorrow's Nature. "We actually don't know all of the details of how the layering takes place," says physical chemist and co-author Rod Ruoff. Laboratory tests showed that the grapheme paper was as strong as that made from carbon nanotubes, yet unlike nanotubes, the material can be fabricated to any size. That makes graphene paper a prime candidate for a new generation of superstrong composite materials, Ruoff says.
The super paper does have its kryptonite, however. The sheets remain stable when exposed to air, says Ruoff, but immersing them in water slowly loosens the bonds. Also, says materials scientist Boris Yakobson of Rice University in Houston, Texas, because water is so common as either liquid as rain or vapor as humidity, it will likely affect graphene sheets exposed to the environment in the long run if the material can't be protected from water's effects. So, the next task is to find other molecules that can replace water in the fabrication process. That research challenge and others probably puts commercialization of the technology at least 5 or 10 years away, Ruoff says
ADVANTAGE: Inexpensive paper-like material with superior physical properties compared to similar vermiculite, graphite foil and carbon nanotube materials.
SUMMARY: Inorganic “paper-like” materials based on exfoliated vermiculite or mica are employed as protective coatings, binders, dielectric barriers and gas-impermeable membranes. Graphite foils, composed of stacked expanded graphite platelets find use in packing and gasketing applications. Recently carbon nanotube bucky paper exhibiting mechanical and electrical properties suitable for fuel cell and composite applications have been reported. Herein a novel free standing membrane material prepared from graphene oxide (GO) with properties superior to the above materials is described. Membrane filtration of colloidal graphene oxide sheet dispersions and drying affords graphene oxide paper 1-30 µm thick. SEM and XRD analysis reveal well packed layers sandwiched between less densely packed 100-200 nm thick layers, with ~ 1 molecular water layer between sheets . Stress-strain curves of the material are similar to paper or foil like materials, however GO paper is very stiff as evidenced by clean fracture and 0.6% tensile strain (Fig. 2), comparable to flexible graphite (0.5%) and significantly lower than vermiculite (2.5%) and bucky paper (3-5.6%). The work of extension to fracture (350 kJ/m3) is comparable to bucky paper and 10 fold greater than flexible graphite. Tensile modulus of GO paper (32 GPa) is also significantly larger than reported for the other materials (Fig. 3). Cyclic loading measurements exhibit increased modulus of elasticity per cycle leading to better alignment of the plates and increased stiffness. Bending performance of graphene oxide paper show it to be a highly pliable macroscopic substance composed of stiff (in-plane) but compliant (out-of –plane) graphene oxide layers that are tightly interlocked providing high resiliency Graphene oxide paper offers a material with enhanced properties compared with traditional carbon- and clay-based papers. Inexpensive graphene oxide promises a cost effective material for fabrication of large area sheets useful for membrane, anisotropic ionic conductors, supercapacitors and storage materials. GO paper may also serve as a carrier for polymers, ceramics and metals. The chemical functionality of the GO surface provides opportunities for chemical modification such as addition of crosslinkers to enhance interlayer attraction.
STATUS: A patent application has been filed.
About The Researchers:

Rodney Ruoff
Director, NU BIMat Center
John Evans Professor of Nanoengineering
Dept. of Mechanical Engineering
Northwestern University
2145 Sheridan Road, Rm. L288
Evanston, IL 60208-3111, USA
TEL: 847-467-6596
FAX: 847-491-3915
r-ruoff@northwestern.edu

SonBinh T. Nguyen, Ph.D.
2015 Nanofabrication Building
Northwestern University, Dept. of Chemistry
Evanston, IL 60208-3113
Phone: (847)467-3347
Email: stn@northwestern.edu


Dr. Sasha Stankovich
Hometown: Leskovac, Serbia
Department of Mechanical Engineering
Northwestern University
2145 Sheridan Road, Rm. L288
Evanston, IL 60208-3111, USA
stakovich@northwestern.edu
Dmitriy A. Dikin

d-dikin@northwestern.edu

Funded & About Technology Transfer Program
The Technology Transfer Program (TTP), which is part of the Office of the President, is responsible for implementing the Patent and Invention Policy for Northwestern University, and fostering the transfer of novel technologies from the University to industry. TTP policies and procedures for technology transfer reflect the University's practice of preserving traditional rights to disseminate research results, while at the same time providing a basis for protecting creative ideas for commercialization opportunities to introduce new products in the market for public benefit. Transfer of innovative ideas from the laboratory to the marketplace is a complex endeavor that depends on the close cooperation of individuals and institutions. Companies capable of developing, producing, and marketing innovative products or processes usually require that ideas are protected by patents or other means before risking the often substantial investment required to support development, manufacturing, marketing and sales costs. However, without intellectual property protection of one kind or another there would be little incentive for industry to commercialize important innovations. When an invention is commercialized under license to a company, a number of benefits may flow to the inventor, the laboratory, and the institution. These can include royalty income, research support, recruiting of students, and consulting arrangements, not to mention unique opportunities for collaboration.
In The Images-
1.Comparison tensile strength, ( red) and modulus (E blue) for bucky paper, flexible graphite and vermiculite.
2.Stress strain curve 5.2 μm thick sample (red) and reloaded fragment sample (blue).
3.SEM images of two GO paper samples of same thickness a) ~ 70 μm radius of curvature, b) ~ 20 μm radius.
4.SEM side view images of 10 μm thick graphene oxide paper
5.Dumping graphene oxide particles in water (top) causes them to begin binding together spontaneously into superstrong sheets. Credit: Rod Ruoff