Bivalve
mollusks shells are of interest to leading experts in many areas of human
activity, such as ecology, biology, paleontology, but also materials
engineering. In recent years, much attention has been paid to studying the
preferred orientation of biological tissues such as mollusks shells [1-4].
These polycrystalline materials are characterized by anisotropy of physical and
mechanical properties, which are closely related to the preferred orientation
(texture) of their grains. The above biological objects can serve as a
bioinspiration for material scientists, because nature itself can create
entities that are characterized by incredible mechanical properties using
relatively small amounts of material. Therefore, the characterization of
texture and its correlation with the above-mentioned properties is a
cornerstone for understanding the properties of biological polycrystalline
materials.
Preferred orientation and exact phase composition of two samples of
freshwater shells of the species Sinanodonta woodiana collected from Czech
freshwater steams were measured – (i) an adult shell and (ii) a young
individual.
Pole figures were measured for planes (111), (021), (002), (211), (220) and
(221). Texture data processing was done by MTEX (Matlab) [5]. All diffraction
experiments were performed on the SmartLab Rigaku X-ray diffractometer (Cu Kα). Complete
pole figures were calculated for planes (100), (010), (001), (101) and (110).
From the phase analysis it is clear
that the Sinanodonta woodiana shells consist only of the aragonite phase.
The c-axis of aragonite is perpendicular to the inner surface of the shell and crystallographic
texture in all studied shells is strongly uniaxial. The sharpness of the
texture is higher for young shells.
The authors expresses gratitude for the support provided by Project NPU
I – LO1603 of the Ministry of Education of the Czech Republic to the Institute
of Physics of the Academy of Sciences of the Czech Republic.