Navigation Links
Scientists create tough ceramic that mimics mother of pearl
Date:12/5/2008

Biomimicry technological innovation inspired by nature is one of the hottest ideas in science but has yet to yield many practical advances. Time for a change. Scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have mimicked the structure of mother of pearl to create what may well be the toughest ceramic ever produced.

Through the controlled freezing of suspensions in water of an aluminum oxide (alumina) and the addition of a well known polymer, polymethylmethacrylate (PMMA), a team of researchers has produced ceramics that are 300 times tougher than their constituent components. The team was led by Robert Ritchie, who holds joint appointments with Berkeley Lab's Materials Sciences Division and the Materials Science and Engineering Department at the University of California, Berkeley.

"We have emulated nature's toughening mechanisms to make ice-templated alumina hybrids that are comparable in specific strength and toughness to aluminum alloys," says Ritchie. "We believe these model materials can be used to identify key microstructural features that should guide the future synthesis of bio-inspired, yet non-biological, light-weight structural materials with unique strength and toughness."

The results of this research were reported in the December 5, 2008 issue of the journal Science, in a paper entitled: "Tough, bio-inspired hybrid materials." Co-authoring the paper with Ritchie were Etienne Munch, Max Launey, Daan Hein Alsem, Eduardo Saiz and Antoni Tomsia.

Mother of pearl, or nacre, the inner lining of the shells of abalone, mussels and certain other mollusks, is renowned for both its iridescent beauty and its amazing toughness. Nacre is 95-percent aragonite, a hard but brittle calcium carbonate mineral, with the rest of it made up of soft organic molecules. Yet nacre can be 3,000 times (in energy terms) more resistant to fracture than aragonite. No human-synthesized composite outperforms its constituent materials by such a wide margin. The problem has been that nacre's remarkable strength is derived from a structural architecture that varies over lengths of scale ranging from nanometers to micrometers. Human engineering has not been able to replicate these length scale variances.

Two years ago, however, Berkeley Lab researchers Tomsia and Saiz found a way to improve the strength of bone substitutes through a processing technique that involved the freezing of seawater. This process yielded a ceramic that was four times stronger than artificial bone. When seawater freezes, ice crystals form a scaffolding of thin layers. These layers are pure ice because during their formation impurities, such as salt and microorganisms, are expelled and entrapped in the space between the layers. The resulting architecture roughly resembles that of nacre.

"Since seawater can freeze like a layered material, we allowed nature to guide the process by which we were able to freeze-cast ceramics that mimicked nacre," said Tomsia when this research was reported.

In this latest research, Ritchie, working with Tomsia and Saiz, refined the freeze-casting technique and applied it to alumina/PMMA hybrid materials to create large porous ceramic scaffolds that much more closely mirrored the complex hierarchical microstructure of nacre. To do this, they first employed directional freezing to promote the formation of thin layers (lamellae) of ice that served as templates for the creation of the layered alumina scaffolds. After the ice was removed, spaces between the alumina lamellae were filled with polymer.

"The key to material toughness is the ability to dissipate strain energy," says Ritchie. "Infiltrating the spaces between the alumina layers with polymer allows the hard alumina layers to slide (by a small amount) over one another when load is applied, thereby dissipating strain energy. The polymer acts as a lubricant, like the oil in an automobile engine."

In addition to making the lamellar scaffolds, the team was also able to fabricate nacre-like "brick-and-mortar" structures with very high alumina content. They did this by collapsing the scaffolds in a perpendicular direction to the layers then sintering the resulting alumina "bricks" to promote brick densification and the formation of ceramic bridges between individual bricks.

Says Saiz, "Using such techniques, we have made complex hierarchical architectures where we can refine the lamellae thickness, control their macroscopic orientation, manipulate the chemistry and roughness of the inter-lamellae interfaces, and generate a given density of inorganic bridges, all over a range of size-scales."

For ceramic materials that are even tougher in the future, Ritchie says he and his colleagues need to improve the proportion of ceramic to polymer in their composites. The alumina/PMMA hybrid was only 85-percent alumina. They want to boost ceramic content and thin the layers even further. They also want to replace the PMMA with a better polymer and eventually replace the polymer content altogether with metal.

Says Ritchie, "The polymer is only capable of allowing things to slide past one another, not bear any load. Infiltrating the ceramic layers with metals would give us a lubricant that can also bear some of the load. This would improve strength as well as toughness of the composite."

Such future composite materials would be lightweight and strong as well as tough, he says, and could find important applications in energy and transportation.


'/>"/>

Contact: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
Source:Eurekalert  

Related biology news :

1. Scientists film inner workings of the immune system
2. Rooted plants move mysteriously down greenways, scientists say
3. Caltech scientists show function of helical band in heart
4. Argonne scientists discover possible mechanism for creating handedness in biological molecules
5. Scientists developing food allergy treatment
6. Wistar scientists find key to keeping killer T cells in prime shape for fighting infection, cancer
7. CSHL scientists discover a new way in which epigenetic information is inherited
8. Caltech scientists develop barcode chip for cheap, fast blood tests
9. UNC scientists teach enzyme to make synthetic heparin in more varieties
10. Childrens Hospital scientists achieve repair of injured heart muscle in lab tests of stem cells
11. Scientists shed light on evolution of gene regulation
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Scientists create tough ceramic that mimics mother of pearl
(Date:6/21/2016)... , June 21, 2016 NuData Security announced ... new role of principal product architect and that ... director of customer development. Both will report directly ... officer. The moves reflect NuData,s strategic growth in ... to high customer demand and customer focus values. ...
(Date:6/9/2016)... , June 9, 2016  Perkotek an innovation leader in attendance control systems is ... log work hours, for employers to make sure the right employees are actually signing ... http://photos.prnewswire.com/prnh/20160609/377486LOGO ... ... ...
(Date:6/2/2016)... The Department of Transport Management (DOTM) of ... Dollar project, for the , Supply and Delivery ... IT Infrastructure , to Decatur ... Identity Management Solutions. Numerous renowned international vendors participated in the ... was selected for the most compliant and innovative solution. The ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... 2016  Blueprint Bio, a company dedicated to identifying, ... community, has closed its Series A funding round, according ... "We have received a commitment from Forentis Fund ... to meet our current goals," stated Matthew Nunez ... to complete validation on the current projects in our ...
(Date:6/23/2016)... (PRWEB) , ... June 23, 2016 , ... ... is exhibiting at the Pennsylvania Convention Center and will showcase its product’s latest ... ClinCapture will also be presenting a scientific poster on Disrupting Clinical Trials in ...
(Date:6/23/2016)... June 22, 2016  Amgen (NASDAQ: AMGN ... QB3@953 life sciences incubator to accelerate the ... shared laboratory space at QB3@953 was created to help ... obstacle for many early stage organizations - access to ... sponsorship, Amgen launched two "Amgen Golden Ticket" awards, providing ...
(Date:6/22/2016)... , June 22, 2016 Research and Markets ... Markets" report to their offering. ... in 2014 from $29.3 billion in 2013. The market is expected ... 13.8% from 2015 to 2020, increasing from $50.6 billion in 2015 ... product forecasts during the forecast period (2015 to 2020) are discussed. ...
Breaking Biology Technology: