Tech Front - New Carbon Nanotubes Outperform Copper as Electrical Conductors
Carbon nanotube-based fibers created at Rice University (Houston) show that on a pound-per-pound basis, the nanotube fibers have more capacity to conduct electrical current than copper. Although individual nanotubes can transmit nearly 1000 times more current than copper, the same tubes coalesced into a fiber using other technologies fail long before reaching that capacity.
In Rice’s research, tests show that wet-spun carbon nanotube fibers still easily beat copper, carrying up to four times as much current as a copper wire of the same mass. The research shows that nanotube cables are ideally suited for lightweight power transmission applications where weight is a factor, particularly for aerospace use.
This analysis led by Rice professors Junichiro Kono and Matteo Pasquali appeared online in the journal Advanced Functional Materials. A year ago, the journal Science reported that Pasquali’s lab, in collaboration with scientists at the Dutch firm Teijin Aramid, created a very strong conductive fiber out of carbon nanotubes.
Current copper or aluminum transmission cables are heavy because their low tensile strength requires steel-core reinforcement. Researchers studying nanoscale materials have thought there may be better ways to move electricity, and certain types of carbon nanotubes can carry far more electricity than copper. The ideal cable would be made of long metallic "armchair" nanotubes that would transmit current over great distances with little loss, but such a cable is not feasible because it’s not yet possible to manufacture pure armchairs in bulk, Pasquali said.
The Pasquali lab has created a method to spin fiber from a mix of nanotube types that still outperforms copper. The cable developed by Pasquali and Teijin Aramid is strong and flexible even though at 20 microns wide, it’s thinner than a human hair.
Pasquali turned to Kono and his colleagues, including lead author Xuan Wang, a postdoctoral researcher at Rice, to quantify the fiber’s capabilities. Pasquali said there has been a disconnect between electrical engineers who study the current carrying capacity of conductors and materials scientists working on carbon nanotubes. "That has generated some confusion in the literature over the right comparisons to make," Pasquali said.
The researchers analyzed the fiber’s "current carrying capacity" (CCC), or ampacity, with a custom rig that allowed them to test it alongside metal cables of the same diameter. The cables were tested while they were suspended in the open air, in a vacuum and in nitrogen or argon environments. "The outcome is that these fibers have the highest CCC ever reported for any carbon-based fibers," Kono said. "Copper still has better resistivity by an order of magnitude, but we have the advantage that carbon fiber is light. So if you divide the CCC by the mass, we win."
Kono plans to further investigate and explore the fiber’s multifunctional aspects, including flexible optoelectronic device applications. Pasquali suggested the thread-like fibers are light enough to deliver power to aerial vehicles.
The paper’s co-authors are Rice alumnus Natnael Behabtu and graduate students Colin Young and Dmitri Tsentalovich. Kono is a professor of electrical and computer engineering, of physics and astronomy, and of materials science and nanoengineering. Pasquali is a professor of chemical and biomolecular engineering, chemistry, and materials science and nanoengineering. Tsentalovich, Kono and Pasquali are members of Rice’s Richard E. Smalley Institute for Nanoscale Science and Technology.
The research was supported by the Department of Energy, the National Science Foundation, the Robert A. Welch Foundation, Teijin Aramid BV, the Air Force Office of Scientific Research and the Department of Defense National Defense Science and Engineering Graduate Fellowship. ME
Tools for Parting and Grooving
Cutting tool developer Sandvik Coromant (Fair Lawn, NJ) has created new solutions for parting and grooving with deep grooves and long overhangs aimed at shops doing turning operations with bar-fed stock. The CoroCut QD line of tooling helps shops maximize stainless and other bar-fed materials for turned parts to help control materials costs.
Predictable and consistent tool life is important to ensure reproducible component quality, particularly when parting-off. In recent years, the demands of parting and grooving in modern machining operations have grown into a specialized area of turning. Parting-off is the process used to create deep grooves that ultimately remove a complete or partly-complete component from its parent stock. The concept demands productive, repeatable, high-quality performance with maximum tool life and minimum material waste.
Grooving is similar to parting, except the grooves are cut to a specific depth instead of severing a component from the bar stock. Grooving can be performed on internal and external surfaces, as well as on part faces. The attributes required for grooving are the same as for parting-off, with the added requirement of dimensional precision.
Sandvik Coromant’s development of the CoroCut QD focused on new and upgraded parting geometries. The CoroCut QD offers several design innovations, such as insert indexing that is achieved via a smart yet user-friendly clamping mechanism. The insert seat is tilted 20° and incorporates a backstop to withstand high cutting forces. For insert widths of 2 mm and wider, the insert interface also has a rail to increase stability even further.
Another key innovation is the CoroCut QD HP (high precision) coolant with parting blades and tool blocks/adapters that not only feature plug-and-play coolant for an easy connection, but strategically located coolant holes above and below the cutting edge. These holes are extremely beneficial when parting-off and producing deep grooves as they facilitate accurate coolant delivery. This not only aids the evacuation of swarf, thus increasing process stability, but also helps lower temperature in the cutting zone and increase tool life.
The plug-and-play coolant, available in March, is augmented by the addition of more CoroCut QD-compatible adapters to suit even more types of machines. For turning centers, Coromant Capto, HSK-T and VDI adapters will be available to suit the most common machine tool interfaces for connecting QS shanks and parting blades. A simple valve bolt enables the use of both external and internal coolant, or to switch between external and internal coolant. ME
For more information, see http://www.sandvik.coromant.com.
Research Sessions Part of
the Big Picture at The Big M
Three concurrent research conferences are part of the continuum of manufacturing solutions that unites at The Big M (http://bigmevent.com), coming to Detroit’s riverfront Cobo Center June 9–12. SME’s 42nd North American Manufacturing Research Conference (NAMRC 42), the American Society of Mechanical Engineers’ Manufacturing Science and Engineering Conference (MSEC 2014) and the International Conference on Materials and Processing (ICM&P 2014) of the Japan Society of Mechanical Engineers are coordinated by the University of Michigan (Ann Arbor). Rapid 2014 is also co-located with The Big M.
All sessions of the manufacturing research conferences will take place at Cobo Center, in proximity to The Big M’s exhibits, innovation experts and networking opportunities. Research attendees also can take provided transportation for industry tours and to Ann Arbor for U of M engineering lab tours and the conference awards banquet.
Parallel NAMRC, MSEC and ICM&P conference tracks will include keynote and technical presentations, ranging from materials, processing, micro and nanotechnologies to properties, applications, and systems and sustainable manufacturing; expert panels; student poster and design project presentations; an exhibition of industry partners and a forum for researchers in the early years of their careers.
Check the joint Web site for complete details and registration information: http://tinyurl.com/ngzk4tu. Recent past volumes of SME’s NAMRC conference publication are available at: http://tinyurl.com/NAMRCpub.
The States of STEM
ALABAMA—Auburn University’s 15-hour tribology and lubrication science minor, the first in the nation, debuted in fall 2013 and includes the multidisciplinary study of contact, friction, wear and lubrication of surfaces. Satisfactory tribological performance is critical in such applications as bearings, tires and engines in automobiles; human joint replacement; manufacturing; nanotechnology; oil product chemistry; power generation; hard-drive technology; and electrical contacts.
At the University of Alabama (Tuscaloosa), three researchers have collaborated on the first 3D print of a G-quadruplex DNA sequence and its molecular structure, allowing researchers a potentially valuable new tool in the fight against cancer.
ALASKA—A recent $150,000 NIST grant to the University of Alaska-Anchorage (UAA) will support efforts to assess the technical needs of small and mid-sized manufacturers in Alaska through a possible Manufacturing Extension Partnership. The Alaska Native Science & Engineering Program, started in 1995 with one student, has now graduated more than 300 students at UAA by offering STEM engagement programs as early as fifth grade.
ARIZONA—By demonstrating the natural connection between baseball, science and math, the University of Arizona (UA; Tucson) College of Engineering’s "Science of Baseball" program encourages academically at-risk middle-school students by tapping into their athletic strengths, capabilities and interests. Separately, UA’s Nano-Electronics and Advanced Materials Research Lab is studying heat transfer inside lithium-ion batteries, an issue that has taken priority with manufacturers over energy density and cost.
Arizona State University (Tempe) has renamed its innovative technology college as the Polytechnic School as part of blending its applied engineering programs and additional research facilities into ASU’s Ira A. Fulton Schools of Engineering. Several unique initiatives from the Polytechnic School include TechShop, a membership-based, do-it-yourself workshop and fabrication studio with locations nationwide, and iProjects, which connects ASU students with industry to solve real business problems.
ARKANSAS—At the University of Arkansas (Fayetteville), international research on graphene’s bonding effect on platinum nanoparticles may lead to lower costs in fuel cell production. ME
TechFront is edited by Senior Editors Patrick Waurzyniak, firstname.lastname@example.org, and Ellen Kehoe, email@example.com.
This article was first published in the April 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 4/1/2014