<p>Bio-inorganic structures have
been found to exhibit impressive optical and mechanical properties, such as control
of light and/or high fracture strength. Certain species of diatoms
(single-celled algae) form siliceous microshells (frustules) with organized structures
that affect the transmission of light or fracture strengths. It has been found
that <i>Coscinodiscus wailesii</i> diatoms
have frustules with a quasi-regular hexagonal pattern of pores, which act as
micro-lenses. In terms of mechanical strength, <i>Fragilariopsis kerguelensis</i> diatom SiO<sub>2</sub> frustules have
been observed to exhibit impressive compressive and tensile fracture stress
values. In this study, shape-preserving chemical conversion (using gas/solid
reactions) is used to transform biogenic structures (diatom frustules) into
high IR refractive index or ultrahigh specific strength materials. High-fidelity
MgO/Si, Mg<sub>2</sub>Si, Ca<sub>2</sub>Si, MgO/Ti, and Ti replicas are successfully
synthesized and characterized
by SEM, EDX, XRD, and TEM. Focal point imaging experiments are used to show that
focusing behavior of MgO/Si and Mg<sub>2</sub>Si replicas can be enhanced in
the IR range upon conversion into higher index replicas. Mechanical properties
of SiO<sub>2</sub> frustules, MgO/Ti replicas, and Ti replicas have been
measured by using in-situ and ex-situ indentation, which revealed that the
mechanical properties can be enhanced by the shape-preserved chemical
conversion of Bio-inorganic structures.</p><p><br></p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12811646 |
| Date | 12 October 2021 |
| Creators | Sunghwan Hwang (9243854) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY-NC-SA 4.0 |
| Relation | https://figshare.com/articles/thesis/SHAPE-PRESERVING_TRANSFORMATIONS_OF_BIO-ENABLED_SILICA_STRUCTURES_FOR_OPTICAL_AND_MECHANICAL_APPLICATIONS/12811646 |
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