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 Tiny quantum sensors watch materials transform under pressure
13.12.2019 | DOE/Lawrence Berkeley National Laboratory

nachricht Light, strong, and tough: Researchers at the University of Bayreuth discover unique polymer fibres
13.12.2019 | Universität Bayreuth

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Uranium chemistry and geological disposal of radioactive waste

New insights using the diamond light

A new paper to be published on 16 December provides a significant new insight into our understanding of uranium biogeochemistry and could help with the UK's...

Im Focus: Virus multiplication in 3D

Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.

For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Uranium chemistry and geological disposal of radioactive waste

16.12.2019 | Earth Sciences

New CRISPR-based system targets amplified antibiotic-resistant genes

16.12.2019 | Life Sciences

Supporting structures of wind turbines contribute to wind farm blockage effect

13.12.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>