new carbon nanotubes may boost battery life a - sme - · pdf file · 2015-02-24new...

March 2015 | AdvancedManufacturing.org 37

ttech frontTHE LATEST RESEARCH AND DEVELOPMENT NEWS IN MANUFACTURING AND TECHNOLOGY

New Carbon Nanotubes May Boost Battery Life

A team of researchers at the University of Wisconsin

(Madison, WI) have discovered high-performing

carbon nanotubes that may lead to the development

of improved battery life for flexible electronics and also for

military and industrial applications.

The research team, led by materials science Associate

Professor Michael Arnold and Professor Padma Gopalan,

recently released their results in a paper published in the jour-

nal ACS Nano. According to the UW-Madison scientists, the

carbon nanotube transistors are the highest-performing ever

discovered, with an on-off ratio that is 1000 times better and

conductance that is 100 times better than any other carbon

nanotube transistors.

“Carbon nanotubes are very strong and very flexible, so they

could also be used to make flexible displays and electronics

that can stretch and bend, allowing you to integrate electron-

ics into new places like clothing,” said Arnold. “The advance

enables new types of electronics that aren’t possible with the

more brittle materials manufacturers are currently using.”

Consisting of single atomic sheets of carbon rolled into

a tube, carbon nanotubes are among the best conductors

of electricity. The carbon nanotubes are considered to be

among the most promising material to use as a next-gener-

ation transistor. The UW-Madison researchers drew on tech-

nologies that use polymers to selectively sort the semicon-

ducting nanotubes, achieving a solution of ultra-high-purity

semiconducting carbon nanotubes.

Previous techniques to align the nanotubes resulted in

less-than-desirable packing density, or how close the nano-

tubes are to one another when they are assembled in a film.

But the researchers developed a new technique, called float-

ing evaporative self-assembly, or FESA, which they described

earlier in 2014 in the ACS journal Langmuir. In that tech-

nique, researchers exploited a self-assembly phenomenon

triggered by rapidly evaporating a carbon nanotube solution.

The team’s most recent development also brings the field

closer to realizing carbon nanotube transistors as a feasible

replacement for silicon transistors in computer chips and in

high-frequency communication devices, which are rapidly

approaching their physical scaling and performance limits.

The UW-Madison researchers have patented their technol-

ogy through the Wisconsin Alumni Research Foundation

Schematic (top of image) of a polymer-wrapped carbon nanotube. Scanning microsopy image (bottom) of carbon nanotubes that

were aligned via FESA and incorporated as the active channel of a field-effect transistor device.

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and have begun to work with companies to accelerate the

technology transfer to industry.

“This is not an incremental improvement in performance,”

Arnold says. “With these results, we’ve really made a leap in

carbon nanotube transistors. Our car-

bon nanotube transistors are an order

of magnitude better in conductance

than the best thin-film transistor tech-

nologies currently being used commer-

cially while still switching on and off like

a transistor is supposed to function.”

The work was funded by a grant

from the National Science Foundation,

as well as grants from the UW-Madison

Center of Excellence for Materials

Research and Innovation, the US Army

Research Office, the National Sci-

ence Foundation Graduate Research

Fellowship Program, and the Wis-

consin Alumni Research Foundation.

Additional authors on the ACS Nano

paper include UW-Madison materi-

als science and engineering graduate

students Gerald Brady, Yongho Joo

and Matthew Shea, and electrical and

computer engineering graduate student

Meng-Yin Wu.

An abstract of the paper is avail-

able at http://pubs.acs.org/doi/

abs/10.1021/nn5048734.

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Several overview papers provide a tutorial on fluids

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(TP91PUB455), “The Why of Metal Working Fluids” (TP-

65PUB52), “Cutting Fluids–Third Dimension in Metalworking”

(TP66PUB218), “Practical Fluid Management” (TP89PUB237)

and “Fluid Management” (TP93PUB140).

The 46-page “Primer” highlights the wide range of avail-

able fluids “as a tool of production and applied to: (1) provide

an adequate cooling action, (2) provide a tolerate tool and die

life, (3) produce a satisfactory surface texture for the product

and (4) maximize economical production parallel to an estab-

lished quality standard.”

Additionally covered are metal removing and metalwork-

ing dynamics and cutting and grinding mechanics, as well as

a discussion of the parameters in formulating metalworking

fluids and the classes of metalworking lubricants.

TP66PUB218’s author, R.L. Quanstrom of Cincinnati Milling

& Grinding Machines, points out that not just any fluid can

bring expensive machine setups to peak efficiency. “The fluid

must be engineered to do the job, taking into account all of

the conditions surrounding the metal removal process it is to

facilitate.” Additionally, proper installation of the system and

maintenance of the coolant are essential. And “do not surprise

the system with special additives” unless compatibility with the

coolant is checked, to avoid aggravating a problem.

Aerosol Issues

Cutting fluid aerosol generation poses air quality prob-

lems during machining operations. Authors at several North

American Manufacturing Research Conferences (NAMRC)

have presented research work on this issue. In TP00PUB98,

SME Fellows Steven Y. Liang and David A. Stephenson and

colleagues develop a set of quantitative models to predict the

generation rate of shop-floor aerosol resulting from cutting

fluid in the turning process. Study of the relative importance

of spinoff vs. splash mechanisms through the model calcula-

tion indicated that spinoff is the dominating mechanism at

high rotational speeds and high flow rates.

Another paper (TP02PUB67) by Liang (Georgia Institute

of Technology; Atlanta), with Hitomi Yamaguchi (University of

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Florida; Gainesville) and Zhong Chen, examines

analytical models that describe the aerosol con-

centration and particle size distribution as func-

tions of grinding condition and fluid application

parameters. The predictive models can estimate

the resulting air quality based on given grinding

process parameters.

Atomized cutting fluids can be effective for

increasing tool life in micromilling, as opposed to

flood, high-pressure and liquid-nitrogen-based

systems used in macromachining. Three genera-

tions of a cutting fluid application system based

on ultrasonic atomization are described in TP10PUB25 by M.

Rukosuyev, C.S. Goo and M.B.G. Jun of the University of Vic-

toria (British Columbia, Canada) and S.S. Park of the University

of Calgary (Alberta, Canada). The effects of various system

input parameters, such as mist and spray velocities on spray

focusing, were evaluated in each iteration of the atomization

system. The final version is capable of focusing the spray less

than 1.0 mm in focus height in a compact system that can be

integrated in microscale machine tools.

Microbial Matters

Increasing the life of metalworking fluids requires knowl-

edge of the mechanisms and organisms of spoilage and

monitoring of microbial contamination. Microbial matter has


















mattered as a topic over the decades, with papers from the

1970s and ’80s to now.

“If one considers the cost of the concentrates, changing

the coolants, cleaning the machines, loss of tool life, reduced

production and increased disposal problems, it becomes obvi-

ous that coolant rancidity is a very expensive problem for the

metalworking industry,” states the author of TP73PUB233, a

biology professor. The author’s findings in regard to biological

stability are that preservatives are most effectively added to

the diluted coolant rather than to the concentrate. The same

author writes in 1985 on public attitudes, chemical identities

and animal studies involving the safety of water-based cutting

fluids for human workers (TP85PUB195).

Another microbiologist author, Frederick Passman in TP-

84PUB238 and TP89PUB236, describes methods for estimat-

ing and monitoring microbial loads, including direct counts,

viability counts, metabolic activity determinations and cell

constituent concentration testing. “Regardless of the method

selected to control microbial loads in metalworking fluids, a

means of measuring its effectiveness must be identified and

used…generally with at least one microbial parameter and one

or more physical-chemical parameters measured routinely.”

In the very bio-technical TP84PUB238, Passman de-

scribes a rapid catalase (enzyme) test to assist shop-floor

personnel in estimating catalase-positive microorganisms so

that a change in levels can be addressed with increased mi-

crobial control measures. System monitoring plans, covered

in TP89PUB236, aid the timely assessment of coolant condi-

tion and determine the effectiveness of corrective measures.

A monitoring plan (“a realistic action plan,” not “a wasteful

paperwork exercise”) should be developed based on system

size, number of coolant systems in the plant, availability of

personnel, nature of metalworking operation and coolant

performance requirements.

Another NAMRC paper, by Steven Skerlos and colleagues

from the University of Michigan (Ann Arbor), investigated how

to identify and quantify specific hazardous mycobacteria

in metalworking fluids using epi-fluorescence microscopy

or flow cytometry. Previous testing methods had a long lag

time, limiting the ability to control infection of workers or cor-

rect fluid contamination.

TechFront is edited by Senior Editors Patrick Waurzyniak,

[email protected], and Ellen Kehoe, [email protected].

tech front

SME Technical Papers (coded as TP…PUB…) and search options for the collection are available at http://tinyurl.com/SearchTPs.

new carbon nanotubes may boost battery life a - sme - · pdf file · 2015-02-24new...

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