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Organic-inorganic interfaces and spiral growth in nacre.

Yao N, Epstein AK, Liu WW, Sauer F, Yang N - J R Soc Interface (2008)

Bottom Line: Yet, the precise structural features governing its extraordinary strength and its growth mechanism remain elusive.In particular, we describe unique lateral nano-growths and paired screw dislocations in the aragonite layers, and demonstrate that the organic material sandwiched between aragonite platelets consists of multiple organic layers of varying nano-mechanical resilience.These new findings may aid in creating novel organic-inorganic micro/nano composites through synthetic or biomineralization pathways.

View Article: PubMed Central - PubMed

Affiliation: Princeton Institute for the Science and Technology of Materials, Princeton University, 70 Prospect Avenue, Princeton, NJ 08544, USA. nyao@princeton.edu

ABSTRACT
Nacre, the crown jewel of natural materials, has been extensively studied owing to its remarkable physical properties for over 160 years. Yet, the precise structural features governing its extraordinary strength and its growth mechanism remain elusive. In this paper, we present a series of observations pertaining to the red abalone (Haliotis rufescens) shell's organic-inorganic interface, organic interlayer morphology and properties, large-area crystal domain orientations and nacre growth. In particular, we describe unique lateral nano-growths and paired screw dislocations in the aragonite layers, and demonstrate that the organic material sandwiched between aragonite platelets consists of multiple organic layers of varying nano-mechanical resilience. Based on these novel observations and analysis, we propose a spiral growth model that accounts for both [001] vertical propagation via helices that surround numerous screw dislocation cores and simultaneous 010 lateral growth of aragonite sheet structure. These new findings may aid in creating novel organic-inorganic micro/nano composites through synthetic or biomineralization pathways.

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Related in: MedlinePlus

A schematic of the crystallographic directions of an aragonite platelet without surrounding organic layers at a screw dislocation core and the corresponding nano-structures. Asperities, previously interpreted as mineral bridges in lower resolution images, are squat structures found on the [001] faces, while the newly observed [010] or [110] nano-growths are in the vertical plane and have a larger aspect ratio. Note the crystallographic alignment of the asperities, which indicates the platelet crystal orientation. The dislocation slip plane and Burgers vector are labelled.
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fig3: A schematic of the crystallographic directions of an aragonite platelet without surrounding organic layers at a screw dislocation core and the corresponding nano-structures. Asperities, previously interpreted as mineral bridges in lower resolution images, are squat structures found on the [001] faces, while the newly observed [010] or [110] nano-growths are in the vertical plane and have a larger aspect ratio. Note the crystallographic alignment of the asperities, which indicates the platelet crystal orientation. The dislocation slip plane and Burgers vector are labelled.

Mentions: These domains of identically oriented platelets within lamellae imply that the crystal direction has been transmitted laterally, in the 〈010〉 or 〈110〉 directions. Most previous growth models have proposed the dominant growth to be in the [001] direction, as this is the direction in which the nacre growth front propagates, and they have suggested no physical connection or certain relationship in crystal orientation between platelets in the lateral direction. A notable exception was the early hypothesis of Wada (1966) that ‘nacre grows by the advance of growth fronts of mineral terraces which begin from deformed, misfitting or boundary portions on the nacreous surface’; however, the study could not explore the mechanisms of any such growth since evidence from high-resolution imaging was not available. The spiral growth model we propose here accounts for both lateral growth of the aragonite lamellae and [001] propagation via helices that surround numerous screw dislocation cores, which systemically pervade abalone nacre. The relationship between crystallographic directions and corresponding surface structures on a core platelet are shown in figure 3.


Organic-inorganic interfaces and spiral growth in nacre.

Yao N, Epstein AK, Liu WW, Sauer F, Yang N - J R Soc Interface (2008)

A schematic of the crystallographic directions of an aragonite platelet without surrounding organic layers at a screw dislocation core and the corresponding nano-structures. Asperities, previously interpreted as mineral bridges in lower resolution images, are squat structures found on the [001] faces, while the newly observed [010] or [110] nano-growths are in the vertical plane and have a larger aspect ratio. Note the crystallographic alignment of the asperities, which indicates the platelet crystal orientation. The dislocation slip plane and Burgers vector are labelled.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2572677&req=5

fig3: A schematic of the crystallographic directions of an aragonite platelet without surrounding organic layers at a screw dislocation core and the corresponding nano-structures. Asperities, previously interpreted as mineral bridges in lower resolution images, are squat structures found on the [001] faces, while the newly observed [010] or [110] nano-growths are in the vertical plane and have a larger aspect ratio. Note the crystallographic alignment of the asperities, which indicates the platelet crystal orientation. The dislocation slip plane and Burgers vector are labelled.
Mentions: These domains of identically oriented platelets within lamellae imply that the crystal direction has been transmitted laterally, in the 〈010〉 or 〈110〉 directions. Most previous growth models have proposed the dominant growth to be in the [001] direction, as this is the direction in which the nacre growth front propagates, and they have suggested no physical connection or certain relationship in crystal orientation between platelets in the lateral direction. A notable exception was the early hypothesis of Wada (1966) that ‘nacre grows by the advance of growth fronts of mineral terraces which begin from deformed, misfitting or boundary portions on the nacreous surface’; however, the study could not explore the mechanisms of any such growth since evidence from high-resolution imaging was not available. The spiral growth model we propose here accounts for both lateral growth of the aragonite lamellae and [001] propagation via helices that surround numerous screw dislocation cores, which systemically pervade abalone nacre. The relationship between crystallographic directions and corresponding surface structures on a core platelet are shown in figure 3.

Bottom Line: Yet, the precise structural features governing its extraordinary strength and its growth mechanism remain elusive.In particular, we describe unique lateral nano-growths and paired screw dislocations in the aragonite layers, and demonstrate that the organic material sandwiched between aragonite platelets consists of multiple organic layers of varying nano-mechanical resilience.These new findings may aid in creating novel organic-inorganic micro/nano composites through synthetic or biomineralization pathways.

View Article: PubMed Central - PubMed

Affiliation: Princeton Institute for the Science and Technology of Materials, Princeton University, 70 Prospect Avenue, Princeton, NJ 08544, USA. nyao@princeton.edu

ABSTRACT
Nacre, the crown jewel of natural materials, has been extensively studied owing to its remarkable physical properties for over 160 years. Yet, the precise structural features governing its extraordinary strength and its growth mechanism remain elusive. In this paper, we present a series of observations pertaining to the red abalone (Haliotis rufescens) shell's organic-inorganic interface, organic interlayer morphology and properties, large-area crystal domain orientations and nacre growth. In particular, we describe unique lateral nano-growths and paired screw dislocations in the aragonite layers, and demonstrate that the organic material sandwiched between aragonite platelets consists of multiple organic layers of varying nano-mechanical resilience. Based on these novel observations and analysis, we propose a spiral growth model that accounts for both [001] vertical propagation via helices that surround numerous screw dislocation cores and simultaneous 010 lateral growth of aragonite sheet structure. These new findings may aid in creating novel organic-inorganic micro/nano composites through synthetic or biomineralization pathways.

Show MeSH
Related in: MedlinePlus