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  • richardmitnick 11:33 am on March 11, 2019 Permalink | Reply
    Tags: "Electrically-heated silicate glass appears to defy Joule's first law", , , Joule heating also known as Ohmic heating and resistive heating is the process by which the passage of an electric current through a conductor produces heat., Lehigh University,   

    From Lehigh University: “Electrically-heated silicate glass appears to defy Joule’s first law” 

    From Lehigh University

    February 27, 2019
    Lori Friedman

    Experiments show electric field can modify silicate glass, causing parts to melt while remaining solid elsewhere; discovery suggests heat in glass could be produced on a very fine scale, could point to performance challenges for devices that use glass.

    1
    Charles T. McLaren (left), with Himanshu Jain, says applying a direct current field across glass also reduces its melting temperature and makes it possible to shape glass with greater precision than can be done using heat alone. (Courtesy of Lehigh University)

    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 in Nature Scientific Reports that details their discovery that electrically-heated common, homogeneous silicate glasses appear to defy Joule’s first law.

    ________________________________________________
    Joule heating, also known as Ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor produces heat.

    Joule’s first law, also known as the Joule–Lenz law, states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current:

    P ∝ I 2 R {\displaystyle P\propto I^{2}R} {\displaystyle P\propto I^{2}R}

    Joule heating affects the whole electric conductor, unlike the Peltier effect which transfers heat from one electrical junction to another.

    2
    A coiled heating element from an electric toaster, showing red to yellow incandescence

    ________________________________________________

    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.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Lehigh University is an American private research university in Bethlehem, Pennsylvania. It was established in 1865 by businessman Asa Packer. Its undergraduate programs have been coeducational since the 1971–72 academic year. As of 2014, the university had 4,904 undergraduate students and 2,165 graduate students. Lehigh is considered one of the twenty-four Hidden Ivies in the Northeastern United States.

    Lehigh has four colleges: the P.C. Rossin College of Engineering and Applied Science, the College of Arts and Sciences, the College of Business and Economics, and the College of Education. The College of Arts and Sciences is the largest, which roughly consists of 40% of the university’s students.The university offers a variety of degrees, including Bachelor of Arts, Bachelor of Science, Master of Arts, Master of Science, Master of Business Administration, Master of Engineering, Master of Education, and Doctor of Philosophy.

    Lehigh has produced Pulitzer Prize winners, Fulbright Fellows, members of the American Academy of Arts & Sciences and of the National Academy of Sciences, and National Medal of Science winners.

     
  • richardmitnick 1:31 pm on January 30, 2019 Permalink | Reply
    Tags: , , BNL Relativistic Heavy Ion Collider (RHIC), , Brookhaven STAR collaboration, Lehigh University, , ,   

    From Lehigh University: “Big Bang Query” 

    From Lehigh University

    Mapping how a mysterious liquid became all matter

    The leading theory about how the universe began is the Big Bang, which says that 14 billion years ago the universe existed as a singularity, a one-dimensional point, with a vast array of fundamental particles contained within it. Extremely high heat and energy caused it to inflate and then expand into the cosmos as we know it?and, the expansion continues to this day.

    The initial result of the Big Bang was an intensely hot and energetic liquid that existed for mere microseconds that was around 10 billion degrees Fahrenheit (5.5 billion Celsius). This liquid contained nothing less than the building blocks of all matter. As the universe cooled, the particles decayed or combined giving rise to…well, everything.

    Quark-gluon plasma (QGP) is the name for this mysterious substance so called because it was made up of quarks — the fundamental particles — and gluons, which physicist Rosi J. Reed describes as “what quarks use to talk to each other.”

    Quark gluon plasma. Duke University

    Scientists like Reed, an assistant professor in Lehigh University’s Department of Physics whose research includes experimental high-energy physics, cannot go back in time to study how the Universe began. So they re-create the circumstances, by colliding heavy ions, such as Gold, at nearly the speed of light, generating an environment that is 100,000 times hotter than the interior of the sun. The collision mimics how quark-gluon plasma became matter after the Big Bang, but in reverse: the heat melts the ions’ protons and neutrons, releasing the quarks and gluons hidden inside them.

    There are currently only two operational accelerators in the world capable of colliding heavy ions — and only one in the U.S.: Brookhaven National Lab’s Relativistic Heavy Ion Collider (RHIC). It is about a three-hour drive from Lehigh, in Long Island, New York.


    BNL RHIC Campus



    BNL/RHIC

    Reed is part of the STAR Collaboration , an international group of scientists and engineers running experiments on the Solenoidal Tracker at RHIC (STAR). The STAR detector is massive and is actually made up of many detectors. It is as large as a house and weighs 1,200 tons. STAR’s specialty is tracking the thousands of particles produced by each ion collision at RHIC in search of the signatures of quark-gluon plasma.

    BNL/RHIC Star Detector

    “When running experiments there are two ‘knobs’ we can change: the species — such as gold on gold or proton on proton — and the collision energy,” says Reed. “We can accelerate the ions differently to achieve different energy-to-mass ratio.”

    Using the various STAR detectors, the team collides ions at different collision energies. The goal is to map quark-gluon plasma’s phase diagram, or the different points of transition as the material changes under varying pressure and temperature conditions. Mapping quark-gluon plasma’s phase diagram is also mapping the nuclear strong force, otherwise known as Quantum Chromodynamics (QCD), which is the force that holds positively charged protons together.

    “There are a bunch of protons and neutrons in the center of an ion,” explains Reed. “These are positively charged and should repel, but there’s a ‘strong force’ that keeps them together? strong enough to overcome their tendency to come apart.”

    Understanding quark-gluon plasma’s phase diagram, and the location and existence of the phase transition between the plasma and normal matter is of fundamental importance, says Reed.

    “It’s a unique opportunity to learn how one of the four fundamental forces of nature operates at temperature and energy densities similar to those that existed only microseconds after the Big Bang,” says Reed.

    Upgrading the RHIC detectors to better map the “strong force”

    The STAR team uses a Beam Energy Scan (BES) to do the phase transition mapping. During the first part of the project, known as BES-I, the team collected observable evidence with “intriguing results.” Reed presented these results at the 5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan in Hawaii in October 2018 in a talk titled: “Testing the quark-gluon plasma limits with energy and species scans at RHIC.”

    However, limited statistics, acceptance, and poor event plane resolution did not allow firm conclusions for a discovery. The second phase of the project, known as BES-II, is going forward and includes an improvement that Reed is working on with STAR team members: an upgrade of the Event Plan Detector. Collaborators include scientists at Brookhaven as well as at Ohio State University.

    The STAR team plans to continue to run experiments and collect data in 2019 and 2020, using the new Event Plan Detector. According to Reed, the new detector is designed to precisely locate where the collision happens and will help characterize the collision, specifically how “head on” it is.

    “It will also help improve the measurement capabilities of all the other detectors,” says Reed.

    The STAR collaboration expects to run their next experiments at RHIC in March 2019.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Lehigh University is an American private research university in Bethlehem, Pennsylvania. It was established in 1865 by businessman Asa Packer. Its undergraduate programs have been coeducational since the 1971–72 academic year. As of 2014, the university had 4,904 undergraduate students and 2,165 graduate students. Lehigh is considered one of the twenty-four Hidden Ivies in the Northeastern United States.

    Lehigh has four colleges: the P.C. Rossin College of Engineering and Applied Science, the College of Arts and Sciences, the College of Business and Economics, and the College of Education. The College of Arts and Sciences is the largest, which roughly consists of 40% of the university’s students.The university offers a variety of degrees, including Bachelor of Arts, Bachelor of Science, Master of Arts, Master of Science, Master of Business Administration, Master of Engineering, Master of Education, and Doctor of Philosophy.

    Lehigh has produced Pulitzer Prize winners, Fulbright Fellows, members of the American Academy of Arts & Sciences and of the National Academy of Sciences, and National Medal of Science winners.

     
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