Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Measurements Show Silicon Nanospheres Rank Among Hardest Known Materials

21.03.2003


University of Minnesota researchers have made the first-ever hardness measurements on individual silicon nanospheres and shown that the nanospheres’ hardness falls between the conventional hardness of sapphire and diamond, which are among the hardest known materials. Being able to measure such nanoparticle properties may eventually help scientists design low-cost superhard materials from these nanoscale building blocks.

Up to four times harder than typical silicon-a principal ingredient of computer chips, glass and sand-the nanospheres demonstrate that other materials at the nanoscale, including sapphire, may also have vastly improved mechanical properties. The researchers’ results were published online March 18 by the Journal of the Mechanics and Physics of Solids and will appear in June 2003 issue. The work is supported by the National Science Foundation (NSF), the independent federal agency that supports basic research in all fields of science and engineering.

"These results give us two reasons to be excited," said William Gerberich, chemical engineering and materials science professor at Minnesota and lead author on the paper along with his graduate student William Mook. "We can now look at the properties of these building blocks, and from there, we can begin to design superhard materials. In addition, we’ve now achieved a way to conduct experiments on a nanoscale particle and perform atom-by atom supercomputer simulations on a similarly sized particle."



Such nanospheres might find early applications in rugged components of micro-electromechanical systems (MEMS), according to Gerberich. To produce a small gear, for example, the shape could be etched into a silicon wafer and filled with a composite including silicon carbide or silicon nitride nanospheres. The surrounding silicon could then be selectively etched away.

To make the measurements, the research team first devised a method for producing defect-free silicon nanospheres in which the silicon spheres condensed out of a stream of silicon tetrachloride vapor onto a sapphire surface. (Defects in the spheres reduce the hardness by acting as sites for flow or fracture.) The hardness was measured by squeezing individual particles between a diamond-tipped probe and the sapphire.

The smaller the sphere, the harder it was. The spheres tested ranged in size from 100 nanometers to 40 nanometers in diameter, and the corresponding hardness ranged from 20 gigapascals up to 50 gigapascals for the smallest nanospheres. For comparison, stainless steel has a hardness of 1 gigapascal, sapphire of about 40 gigapascals, and diamond of around 90 gigapascals. Bulk silicon averages about 12 gigapascals.

"People have never had these perfect, defect-free spheres to test before," Gerberich said. "You can compare the silicon nanospheres to materials such as nitrides and carbides, which typically have hardness values in the range of 30 to 40 gigapascals." The research team will study silicon carbide nanospheres next, but they’ll need two diamond surfaces for the experiments, since squeezing a silicon carbide nanosphere would likely drill a hole into sapphire.

"This is the first time that a measurement of mechanical, rather than electromagnetic, properties of nanoparticles has been made, which we can now compare to the results of simulations," Gerberich said. "Mechanical properties of materials at this scale are much more difficult to simulate than electromagnetic properties."

A silicon sphere with a 40-nanometer diameter has approximately 40 million atoms. The spheres examined by the Minnesota researchers were composed of 5 million to 600 million atoms. Because materials science algorithms can simulate this number of atoms on supercomputers, the Minnesota team worked with Michael Baskes of Los Alamos National Laboratory to conduct some preliminary simulations, which corresponded well with the experimental findings.

"Better designs for these sorts of nanocomposites will be based on a better understanding of what goes into them," Gerberich said. "These measurements make it possible to pursue a bottom-up approach to materials design from a mechanical perspective."

David Hart | NSF
Further information:
http://www.sciencedirect.com/science/journal/00225096

More articles from Materials Sciences:

nachricht Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University

nachricht Hidden talents: Converting heat into electricity with pencil and paper
20.02.2018 | Helmholtz-Zentrum Berlin für Materialien und Energie

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Stiffness matters

22.02.2018 | Life Sciences

Magnetic field traces gas and dust swirling around supermassive black hole

22.02.2018 | Physics and Astronomy

First evidence of surprising ocean warming around Galápagos corals

22.02.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>