Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Particle size matters for porous building blocks

19.12.2017

Rice University scientists find porous nanoparticles get tougher under pressure, but not when assembled

Porous particles of calcium and silicate show potential as building blocks for a host of applications like self-healing materials, bone-tissue engineering, drug delivery, insulation, ceramics and construction materials, according to Rice University engineers who decided to see how well they perform at the nanoscale.


Thin (left) and thick films made of porous nanoparticles of calcium and silicate reacted differently under pressure as tested in a Rice University lab. Particles in the thin films moved out of the way for a nanoindenter and allowed the film to stay intact, while thick films cracked.

Credit: Multiscale Materials Laboratory/Rice University

Following previous work on self-healing materials using porous building blocks, Rice materials scientist Rouzbeh Shahsavari and graduate student Sung Hoon Hwang made a wide range of porous particles between 150 and 550 nanometers in diameter -- thousands of times smaller than the thickness of a sheet of paper -- with pores about the width of a strand of DNA.

They then assembled the particles into micron-sized sheets and pellets to see how well the arrays held up under pressure from a nanoindenter, which tests the hardness of a material.

The results of more than 900 tests, reported this month in the American Chemical Society's ACS Applied Materials and Interfaces, showed that bigger individual nanoparticles were 120 percent tougher than smaller ones.

This, Shahsavari said, was clear evidence of an intrinsic size effect where particles between 300 and 500 nanometers went from brittle to ductile, or pliable, even though they all had the same small pores that were 2 to 4 nanometers. But they were surprised to find that when the same big particles were stacked, the size effect didn't carry over entirely to the larger structures.

The principles revealed should be important to scientists and engineers studying nanoparticles as building blocks in all kinds of bottom-up fabrication.

"With porous building blocks, controlling the link between porosity, particle size and mechanical properties is essential to the integrity of the system for any application," Shahsavari said. "In this work, we found there is a brittle-to-ductile transition when increasing the particle size while keeping the pore size constant.

"This means that larger submicron calcium-silicate particles are tougher and more flexible compared with smaller ones, making them more damage-tolerant," he said.

The lab tested self-assembled arrays of the tiny spheres as well as arrays compacted under the equivalent of 5 tons inside a cylindrical press.

Four sizes of spheres were allowed to self-assemble into films. When these were subject to nanoindentation, the researchers found the intrinsic size effect largely disappeared as the films showed variable stiffness. Where it was thin, the weakly bonded particles simply made way for the indenter to sink through to the glass substrate. Where it was thick, the film cracked.

"We observed that the stiffness increases as a function of applied indentation forces because as the maximum force is increased, it leads to a greater densification of the particles under load," Shahsavari said. "By the time the peak load is reached, the particles are quite densely packed and start behaving collectively as a single film."

Pellets made of compacted nanospheres of various diameters deformed under pressure from the nanoindenter but showed no evidence of getting tougher under pressure, they reported.

"As a next step, we're interested in fabricating self-assembled superstructures with tunable particle size that better enable their intended functionalities, like loading and unloading with stimuli-sensitive sealants, while offering the best mechanical integrity," Shahsavari said.

###

The National Science Foundation supported the research.

Read the abstract at http://pubs.acs.org/doi/abs/10.1021/acsami.7b15803

This news release can be found online at http://news.rice.edu/2017/12/18/particle-size-matters-for-porous-building-blocks/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Biomimetic, strong, tough and self-healing composites using universal sealant-loaded, porous building blocks: http://pubs.acs.org/doi/abs/10.1021/acsami.7b12532

Multiscale Materials Laboratory (Shahsavari Lab): http://rouzbeh.rice.edu/

George R. Brown School of Engineering: http://engineering.rice.edu

Rice Department of Civil and Environmental Engineering: http://www.ceve.rice.edu

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu

Images for download:

http://news.rice.edu/files/2017/12/1218_SILICATE-1-WEB-1phjcjl.jpg
Thin (left) and thick films made of porous nanoparticles of calcium and silicate reacted differently under pressure as tested in a Rice University lab. Particles in the thin films moved out of the way for a nanoindenter and allowed the film to stay intact, while thick films cracked. (Credit: Multiscale Materials Laboratory/Rice University)

http://news.rice.edu/files/2017/12/1218_SILICATE-2-WEB-24wc2h7.jpg
Rice University materials scientists tested structures made of calcium-silicate nanoparticles and found that particles go from brittle to ductile as they increase in size. The compressed single particle at left deformed under the pressure of a nanoindenter. At center and right, large particles did not crack under pressure. (Credit: Multiscale Materials Laboratory/Rice University)

http://news.rice.edu/files/2017/12/1218_SILICATE-3-WEB-2170eec.jpg
Rice University materials scientists synthesized spherical, porous nanoparticles of calcium and silicate, formed films and pellets and tested their toughness under pressure from a nanoindenter. They found films made of larger particles approaching 500 nanometers were much tougher and the films and pellets less prone to cracking under pressure. At right, small particles are deformed after nanoindentation. (Credit: Multiscale Materials Laboratory/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,879 undergraduates and 2,861 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for quality of life and for lots of race/class interaction and No. 2 for happiest students by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Editor's note: Links to high-resolution images for download appear at the end of this release.

David Ruth
713-348-6327
david@rice.edu

Mike Williams
713-348-6728
mikewilliams@rice.edu

http://news.rice.edu

David Ruth | EurekAlert!

Further reports about: Nanoparticles building blocks nanometers self-healing

More articles from Materials Sciences:

nachricht Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University

nachricht Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>