Nav: Home

Electrically-heated silicate glass appears to defy Joule's first law

February 26, 2019

Characterizing and predicting how electrically-heated silicate glass behaves is important because it is used in a variety of devices that drive technical innovations. Silicate glass is used in display screens. Glass fibers power the internet. Nanoscale glass devices are being deployed to provide breakthrough medical treatments such as targeted drug-delivery and re-growing tissue.

The discovery that under certain conditions electrically-heated silicate glass defies a long-accepted law of physics known as Joule's first law should be of interest to a broad spectrum of scientists, engineers, even the general public, according to Himanshu Jain, Diamond Distinguished Chair of the Department of Materials Science and Engineering at Lehigh University.

The foundation of electrical heating was laid by James Prescott Joule, an English physicist and mathematician, in 1840. Joule demonstrated that heat is generated when electrical current is passed through a resistor. His conclusion, known as Joule's first law, simply states that heat is produced in proportion to the square of an electrical current that passes through a material.

"It has been verified over and over on homogeneous metals and semiconductors which heat up uniformly, like an incandescent light bulb does," says Jain.

He and his colleagues?which includes Nicholas J. Smith and Craig Kopatz, both of Corning Incorporated, as well as Charles T. McLaren, a former Ph.D. student of Jain's, now a researcher at Corning?have authored a paper published today in Scientific Reports that details their discovery that electrically-heated common, homogeneous silicate glasses appear to defy Joule's first law.

In the paper, titled "Development of highly inhomogeneous temperature profile within electrically heated alkali silicate glasses," the authors write: "Unlike electronically conducting metals and semiconductors, with time the heating of ionically conducting glass becomes extremely inhomogeneous with the formation of a nanoscale alkali-depletion region, such that the glass melts near the anode, even evaporates, while remaining solid elsewhere. In situ infrared imaging shows and finite element analysis confirms localized temperatures more than thousand degrees above the remaining sample depending on whether the field is DC or AC."

"In our experiments, the glass became more than a thousand degrees Celsius hotter near the positive side than in the rest of the glass, which was very surprising considering that the glass was totally homogeneous to begin with," says Jain. "The cause of this result is shown to be in the change in the structure and chemistry of glass on nanoscale by the electric field itself, which then heats up this nano-region much more strongly."

Jain says that the application of classical Joule's law of physics needs to be reconsidered carefully and adapted to accommodate these findings.

These observations unravel the origin of a recently discovered electric field induced softening of glass. In a previous paper, Jain and his colleagues reported the phenomenon of Electric Field Induced Softening. They demonstrated that the softening temperature of glass heated in a furnace can be reduced by as much as a couple of hundred degrees Celsius simply by applying 100 Volt across an inch thick sample.

"The calculations did not add up to explain what we were seeing as simply standard Joule heating," says Jain. "Even under very moderate conditions, we observed fumes of glass that would require thousands of degrees higher temperature than Joule's law could predict!"

The team then undertook a systematic study to monitor the temperature of glass. They used high-resolution infrared pyrometers to map out the temperature profile of the whole sample. New data together with their previous observations showed that electric field modified the glass dramatically and that they had to modify how Joule's law can be applied.

The researchers believe that this work shows it is possible to produce heat in a glass on a much finer scale than by the methods used so far, possibly down to the nanoscale. It would then allow making new optical and other complex structures and devices on glass surface more precisely than before.

"Besides demonstrating the need to qualify Joule's law, the results are critical to developing new technology for the fabrication and manufacturing of glass and ceramic materials," says Jain.
-end-


Lehigh University

Related Nanoscale Articles:

Information storage with a nanoscale twist
Discovery of a novel rotational force inside magnetic vortices makes it easier to design ultrahigh capacity disk drives.
Researchers use acoustic waves to move fluids at the nanoscale
A team of mechanical engineers at the University of California San Diego has successfully used acoustic waves to move fluids through small channels at the nanoscale.
Core technology springs from nanoscale rods
Rice University scientists have demonstrated a method for reversibly changing the light emitted from metallic nanorods by moving atoms from one place to another inside the particles.
Tooth decay -- drilling down to the nanoscale
With one in two Australian children reported to have tooth decay in their permanent teeth by age 12, researchers from the University of Sydney believe they have identified some nanoscale elements that govern the behavior of our teeth.
Beating the heat a challenge at the nanoscale
A little heat from a laser can disrupt measurements of materials at the nanoscale, according to Rice University scientists.
New nanoscale technologies could revolutionize microscopes, study of disease
Research completed through a collaboration with University of Missouri engineers, biologists, and chemists could transform how scientists study molecules and cells at sub-microscopic (nanoscale) levels.
New tool allows scientists to visualize 'nanoscale' processes
Chemists at UC San Diego have developed a new tool that allows scientists for the first time to see, at the scale of five billionths of a meter, 'nanoscale' mixing processes occurring in liquids.
Heat and light get larger at the nanoscale
In a new study recently published in Nature Nanotechnology, researchers from Columbia Engineering, Cornell, and Stanford have demonstrated heat transfer can be made 100 times stronger than has been predicted, simply by bringing two objects extremely close -- at nanoscale distances -- without touching.
Revealing the ion transport at nanoscale
EPFL researchers have shown that a law of physics having to do with electron transport at nanoscale can also be analogously applied to the ion transport.
Systems analysis -- from the nanoscale to the global
Two major research grants were announced today by the Engineering and Physical Sciences Research Council.

Related Nanoscale Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...