Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

Home > Press > Pore-free Ceramics Shine New Light on Lasers, Electronics and Biomedical Implants

Researchers developed a new class of ceramics that are so pure and perfectly transparent that they can be used as a substitute for crystals in solid-state lasers.

Credit: Dr. Elizabeth Kupp, Adam Stevenson, and Prof. Gary L. Messing, Department of Materials Science and Engineering, The Pennsylvania State University
Researchers developed a new class of ceramics that are so pure and perfectly transparent that they can be used as a substitute for crystals in solid-state lasers.

Credit: Dr. Elizabeth Kupp, Adam Stevenson, and Prof. Gary L. Messing, Department of Materials Science and Engineering, The Pennsylvania State University

Abstract:
To most people, the word "ceramics," refers to opaque clay flower pots or translucent porcelain tea cups. But not all ceramics block or scatter light.

Gary L. Messing, distinguished professor of ceramic science and engineering, and his group at Pennsylvania State University, are developing a brand new class of ceramics that are so pure and perfectly transparent, they can be used as a substitute for crystals in solid-state lasers.

Pore-free Ceramics Shine New Light on Lasers, Electronics and Biomedical Implants

Arlington, VA | Posted on January 31st, 2009

Unlike traditional ceramics-such as your favorite coffee mug-materials scientists like Messing focus on what's called advanced ceramics. These have unique mechanical, electrical, optical or thermal properties that make them useful in all sorts of applications.

Advanced ceramics are already used in catalytic converters in cars, protective tiles covering the space shuttle, and electronic components in a desktop computer. In medical applications, advanced ceramics are used as the ball in hip replacements.

There are endless possibilities for taking advantage of the unique qualities of advanced ceramics. Many applications are limited, however, by tiny holes, called pores, which scatter light and make them opaque or translucent. Pores can also make the ceramic too brittle and ruin the flow of electrons and /or heat through the material.

"As a result of advances in ceramic processing science, we can now produce extremely high purity ceramics with almost no defects or pores," Messing said.

How "perfect" are the new ceramics? Messing and co-author Adam J. Stevenson reported a new method of making ceramic crystals that are over 99.999 percent free of pores, in their recent article, "Toward Pore-Free Ceramics," published in the Oct. 17, 2008, edition of Science.

At this level of density, there are usually only a few hundred tiny pores left in the researchers' samples after processing. And those pores that remain are generally only 10 to a few hundred nanometers in diameter-about five times smaller than the width of a human hair.

To make such dense ceramics, the scientists use synthetic powders, because they are much purer than clays and other materials mined from the earth. "We start with a very fine powder, form that powder into a desired shape, and then heat the formed powder to create a solid, dense body," said Messing.

This heating process, called sintering, happens at temperatures below the material's melting point. So without liquefying the material, sintering allows atoms in the powder to move around and fill in the spaces between the individual grains.

Soap-bubble Ceramics

"As we sinter a ceramic, the average size of the grains increases, because the larger grains slowly consume the smaller grains," said Messing. "You can visualize this process at home by making soap bubbles in the sink. If you watch carefully, the larger bubbles in the foam will absorb the smaller bubbles."

According to Messing, soap bubble observations like these actually helped materials scientists figure out some aspects of creating ceramics decades ago. "The physics behind 'grain growth' in both soap bubbles and ceramics are identical," he said. "It just happens on a much smaller scale and at higher temperatures in ceramics."

Some scientists predict that different properties of advanced ceramics may be enhanced by reducing grains to nanometer size. "Unfortunately, it can be difficult to make materials this small," said Messing. "If we understand the processes that lead to grain growth better, we can refine the grain size to the nanoscale and maximize mechanical, electrical and optical properties of the ceramic material."

Ceramic Lasers

To test their new method, Messing and his group made neodymium-doped yttrium aluminum garnet (Nd:YAG) laser ceramics, because they are important in industrial and military applications. The Nd:YAG crystal structure also works well with ceramic processing.

"Most high power, solid-state lasers use single crystals made by melt-growth methods," said Stevenson. "These require high temperatures of greater than 1950 degrees Celsius, and weeks or months to grow a single crystal boule [block] of Nd:YAG."

According to Stevenson, switching to ceramic processing could reduce the temperatures needed to make an Nd:YAG laser ceramic by at least 250 degrees Celsius and reduce the time it takes down to just days.

To make the ceramics, the group started with powders and mixed them with liquids and polymers to make a material similar in consistency to paint. "We used a process called tape casting to make long thin sheets of the material," Messing explained. "Next, we cut the sheets into squares and stacked them to form thicker squares about 1 centimeter x 5 cm x 5 cm."

After applying heat to sinter the squares, the ceramics became transparent. But the material still contained enough pores to degrade a laser's performance.

"We did a final step, called hot isostatic pressing (HIP), where we heated the ceramics to over 1600 degrees Celsius and applied high pressures with argon gas," Messing said. "By combining heat with pressure, we eliminated the few remaining pores."

Future Ceramics

After sintering and HIP, a ceramic material looks like a mosaic of tiny crystals, almost like a puzzle, when viewed under a scanning electron microscope.

"The presence of grain boundaries, or junctions, between individual crystals is the single most important difference between melt-grown single crystals and perfect ceramics," Messing said. "But we believe that the grain boundaries are so small that they have virtually no effect on the light traveling through the material."

Studying the effects of grain boundaries on transparent ceramics is just one area the researchers will pursue in the future. "Ceramics can eliminate most of the inherent defects of melt-grown crystals," Messing believes. "That means we may be able to make ceramics with superior optical properties."

For example, by controlling the positions of the ions inside the ceramic, scientists may be able to create new designs for high power lasers. And ceramic processing could allow complex shaped parts, using extrusion or slip casting, for novel laser designs-something they could never achieve with melt-grown crystals.

"Our goals are to make perfect materials and to lay out the science of transparent ceramics in such a way that it can easily be applied to other systems in the future," Stevenson said.

"Although we have made a number of innovations, and we use a number of novel processes, what we do is basic ceramic processing," he said. "The key to achieving transparency is reaching a level of perfection at each stage of the process, which most applications do not require."

"Theory and computational modeling are needed to understand how to shrink pores and limit grain growth," said NSF program director Lynnette Madsen. "And we are in desperate need for tools to monitor nanometer-size pores and grains during the final stage of the sintering process."

According to Madsen, advances such as these will lead to the development of better techniques for making bulk, nanostructured ceramics. "Not only will this research have a positive impact on many essential applications, it will alter how materials science is taught to students," she said.

Investigators
Gary Messing
Adam Stevenson
Venkatraman Gopalan

Related Institutions/Organizations
Pennsylvania State Univ University Park

####

About National Science Foundation
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of $5.92 billion. NSF funds reach all 50 states through grants to over 1,700 universities and institutions. Each year, NSF receives about 42,000 competitive requests for funding, and makes over 10,000 new funding awards. The NSF also awards over $400 million in professional and service contracts yearly.

For more information, please click here

Contacts:
Holly Martin
National Science Foundation

Copyright © National Science Foundation

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

New theory could lead to new generation of energy friendly optoelectronics: Researchers at Queen's University Belfast and ETH Zurich, Switzerland, have created a new theoretical framework which could help physicists and device engineers design better optoelectronics August 23rd, 2016

New flexible material can make any window 'smart' August 23rd, 2016

University of Puerto Rico and NASA back in the news XEI reports August 23rd, 2016

Nanoparticles that speed blood clotting may someday save lives August 23rd, 2016

Chip Technology

New theory could lead to new generation of energy friendly optoelectronics: Researchers at Queen's University Belfast and ETH Zurich, Switzerland, have created a new theoretical framework which could help physicists and device engineers design better optoelectronics August 23rd, 2016

Down to the wire: ONR researchers and new bacteria August 18th, 2016

Hexagonal boron nitride semiconductors enable cost-effective detection of neutron signals: Texas Tech University researchers demonstrate hexagonal boron nitride semiconductors as a cost-effective alternative for inspecting overseas cargo containers entering US ports August 17th, 2016

Enhanced electron doping on iron superconductors discovered: IBS Centre for Correlated Electron Systems revises existing theories by raising the temperature for superconductivity August 17th, 2016

Nanomedicine

Nanoparticles that speed blood clotting may someday save lives August 23rd, 2016

A new way to display the 3-D structure of molecules: Metal-organic frameworks provide a new platform for solving the structure of hard-to-study samples August 21st, 2016

Curbing the life-long effects of traumatic brain injury August 19th, 2016

Lab team spins ginger into nanoparticles to heal inflammatory bowel disease August 19th, 2016

Discoveries

New theory could lead to new generation of energy friendly optoelectronics: Researchers at Queen's University Belfast and ETH Zurich, Switzerland, have created a new theoretical framework which could help physicists and device engineers design better optoelectronics August 23rd, 2016

New flexible material can make any window 'smart' August 23rd, 2016

Nanoparticles that speed blood clotting may someday save lives August 23rd, 2016

Researchers reduce expensive noble metals for fuel cell reactions August 22nd, 2016

Materials/Metamaterials

New flexible material can make any window 'smart' August 23rd, 2016

Researchers reduce expensive noble metals for fuel cell reactions August 22nd, 2016

Industrial Nanotech, Inc. Provides Shareholder Update August 22nd, 2016

Carbodeon Ltd Oy Closes EUR 1.5 million Funding Round From Straightforward Capital: Carbodeon will accelerate its nanodiamonds business and expand manufacturing capacity August 21st, 2016

Announcements

New theory could lead to new generation of energy friendly optoelectronics: Researchers at Queen's University Belfast and ETH Zurich, Switzerland, have created a new theoretical framework which could help physicists and device engineers design better optoelectronics August 23rd, 2016

New flexible material can make any window 'smart' August 23rd, 2016

University of Puerto Rico and NASA back in the news XEI reports August 23rd, 2016

Nanoparticles that speed blood clotting may someday save lives August 23rd, 2016

Photonics/Optics/Lasers

New theory could lead to new generation of energy friendly optoelectronics: Researchers at Queen's University Belfast and ETH Zurich, Switzerland, have created a new theoretical framework which could help physicists and device engineers design better optoelectronics August 23rd, 2016

Hexagonal boron nitride semiconductors enable cost-effective detection of neutron signals: Texas Tech University researchers demonstrate hexagonal boron nitride semiconductors as a cost-effective alternative for inspecting overseas cargo containers entering US ports August 17th, 2016

Prototype chip could help make quantum computing practical: Built-in optics could enable chips that use trapped ions as quantum bits August 9th, 2016

Scientists discover light could exist in a previously unknown form August 6th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic