Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Study may expand applied benefits of super-hard ceramics

Abstract:
Using atomic-scale simulations, the team observed for the first time how atoms moved and interacted as a super-hard ceramic deformed under stress

Study may expand applied benefits of super-hard ceramics

Atlanta, GA | August 04, 2005

A discovery reported in the August 5 issue of Science could speed the design of materials that approach the hardness of diamond yet remain supple enough to be worked like metal.

In a massive computer simulation involving 128 computer processors and nearly 19 million atoms, materials scientist Izabela Szlufarska of the University of Wisconsin-Madison and colleagues at University of Southern California demonstrated the precise atomic mechanisms that explain why "nanostructured" ceramic materials-some of the hardest substances known-also exhibit unusual pliability.

Unlike other exceptionally hard materials, these advanced ceramics tend to bend rather than break, meaning they could be shaped into extremely long-lasting yet lightweight parts for everything from automobile engines and high-speed machining tools to medical implants in the body.

But they are also notoriously difficult to engineer, because as their name implies they possess a grain structure that falls into the nano-size range of molecules and atoms.

"How to optimize their design is an open question," says Szlufarska, who is also a professor of engineering physics. "People have used a trial and error approach to make these materials harder. But there is still much to be understood as to why they are harder."

Simulations can help to answer this by providing a level of detail unavailable to experiments. Using atomic-scale simulations, the team observed for the first time how atoms moved and interacted as a super-hard ceramic deformed under stress. The advance has not only provided unprecedented insight into the properties of these materials, but also a tool that researchers can use to systematically nano-engineer them.

"This study is just the first step," says Szlufarska. "The goal is to design the strongest material possible."

The particular nanostructured ceramic Szlufarska focuses on, called nanocrystalline silicon carbide, is also exceptionally resistant to high temperature and radiation, which has NASA eyeing it as a coating for the space shuttle. Another important application is micro-electro mechanical systems (MEMS), tiny machines that are currently made of silicon.

"Today's MEMS can't have two surfaces rubbing against one another because the silicon is brittle and tends to break," says Szlufarska. "If we could instead make MEMS out of silicon carbide, the sky would be the limit in terms of applications."

Normal ceramics, like clays, become brittle when fired. But when ceramic is made from particles spanning mere atoms in diameter, the material exhibits dramatically improved ductility after bonding at high temperature and pressure.

This unusual combination of strength and suppleness is derived from the material's two-phase nature. In nanocrystalline silicon carbide, says Szlufarska, highly ordered, crystalline grains are surrounded by a more disordered, or amorphous, matrix of grain boundaries-much like tiny stones cemented by a semi-fluid mortar. And the volume of grain boundaries exceeds that in other nanostructured materials such as metals.

To understand, at the atomic scale, how nanocrystalline silicon carbide deforms under force, the team performed a simulation in which they pressed a tiny, virtual probe, called an indenter, into the material's surface and watched how the atoms moved in response. Initially, the grains deformed and then sprang back as a unit, an illustration of the material's hardness.

"At this point, the grains all moved together because the grain boundaries held them together like glue," says Szlufarska.

But as the probe pressed deeper and exerted greater pressure, the researchers witnessed a surprising shift in the material's response. At a specific indentation depth, the grain boundaries began to yield, allowing individual grains to rotate and glide independently under the probe's force.

"Because the grain boundaries are flowing, the material is more ductile than normal ceramic would be," says Szlufarska. "And the grain boundaries initially take part of the deformation, so in essence they protect the grains from breaking."

In contrast, nano-structured metals go through no such phase; instead their grains take the brunt of the force, immediately developing defects, like tiny cracks, when the material begins to yield.

"Once defects occur in the system, the system is just weaker and it's going to break," says Szlufarska.

This crossover in response-from cooperative grain movement and hardness, to individual movement and ductility-is unique to nano-structured ceramics, she says. The researchers next want to learn how to control the crossover point so as to engineer greater hardness into nano-crystalline silicon carbide without compromising pliability. For example, they could vary the volume of the grain boundaries or the size of the grains. Impurities, or dopants, might also be added to the grain boundaries to make the material stronger.

Key to it all is the enormous computing power that allows scientists to simulate the material's atomic details.

"The experiments and devices have become smaller and smaller, while the simulations have grown larger and larger," says Szlufarska. "This is a unique time when the leading edge of materials design is exactly at the same length scale where fully atomic simulations are possible."

####

Contact:
Izabela Szlufarska
608-234-2622
izabela@engr.wisc.edu

Madeline Fisher
(608) 265-8592
mmfisher@engr.wisc.edu

Copyright University of Wisconsin-Madison

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

Possible Futures

Smaller, faster, cheaper: A new type of modulator for the future of data transmission July 27th, 2015

Researchers predict material with record-setting melting point July 27th, 2015

Global Corrosion Resistant Nano Coatings Market To 2015: Acute Market Reports July 27th, 2015

Global Zinc oxide nanopowders Industry 2015: Acute Market Reports July 25th, 2015

MEMS

Iranian Scientists Create Best Conditions for Synthesis of Gold Nanolayers July 23rd, 2015

Robust new process forms 3-D shapes from flat sheets of graphene June 23rd, 2015

Slip sliding away: Graphene and diamonds prove a slippery combination June 10th, 2015

MEMS Industry Group Hosts Its First MEMS/Sensors Conference Session at Transducers 2015: MIG Speakers Will Explore Technology Transfer, Emerging MEMS/Sensors, Manufacturing Infrastructure and Process Technology, June 23 in Anchorage June 3rd, 2015

Discoveries

Non-Enzyme Sensor Determines Level of Blood Sugar July 29th, 2015

Flexible Future of Point-of-Care Disease Diagnostic July 29th, 2015

Meet the high-performance single-molecule diode: Major milestone in molecular electronics scored by Berkeley Lab and Columbia University team July 29th, 2015

Detecting small metallic contaminants in food via magnetization: A practical metallic-contaminant detecting system using three high-Tc RF superconducting quantum interference devices (SQUIDs) July 29th, 2015

Materials/Metamaterials

March 2016; 6th Int'l Conference on Nanostructures in Iran July 29th, 2015

Controlling phase changes in solids: Controlling phase changes in solids July 29th, 2015

Liquipel Debuts Eyesight-Saving ION-Glass Blue Light Protection for iPhones and Androids at RadioShack Stores Nationwide: Liquipel's Unique Protective Screen, Available at RadioShack, Cuts Harmful Blue Light Implicated in Macular Degeneration by 10x July 28th, 2015

Perfect Optical Properties in Production of Aluminum Oxide Colloid Nanoparticles July 28th, 2015

Announcements

Non-Enzyme Sensor Determines Level of Blood Sugar July 29th, 2015

Flexible Future of Point-of-Care Disease Diagnostic July 29th, 2015

Meet the high-performance single-molecule diode: Major milestone in molecular electronics scored by Berkeley Lab and Columbia University team July 29th, 2015

Detecting small metallic contaminants in food via magnetization: A practical metallic-contaminant detecting system using three high-Tc RF superconducting quantum interference devices (SQUIDs) July 29th, 2015

Tools

Publication on Atomic Force Microscopy based nanoscale IR Spectroscopy (AFM-IR) persists as a 2015 top downloaded paper July 29th, 2015

Nanometrics Announces Upcoming Investor Events July 28th, 2015

Reshaping the solar spectrum to turn light to electricity: UC Riverside researchers find a way to use the infrared region of the sun's spectrum to make solar cells more efficient July 27th, 2015

Superfast fluorescence sets new speed record: Plasmonic device has speed and efficiency to serve optical computers July 27th, 2015

Aerospace/Space

UT Dallas nanotechnology research leads to super-elastic conducting fibers July 24th, 2015

Global Aerospace Applications Nanocoatings Industry 2015: Acute Market Reports July 21st, 2015

NASA-Funded Study Reduces Cost of Human Missions to Moon and Mars by Factor of Ten July 20th, 2015

University of Puerto Rico and NASA in the news XEI reports July 16th, 2015

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