M Iijima1, H Kamemizu, N Wakamatsu
1Asahi University School of Denistry, Dental Materials and Technology, Gifu, Japan.
This study examined how the apatite in Lingula shells changes when heated. The researchers compared two species of Lingula and analyzed their apatite structure against human tooth enamel. They found that the structural water in Lingula apatite is loosely bound and is lost at lower temperatures than in tooth enamel. The apatite also transforms into beta-tricalcium phosphate when heated to 700 degrees C. The study used thermal analysis and spectroscopy to track these changes. The findings suggest that Lingula apatite has a unique thermal decomposition pathway. These results could help understand how biogenic apatites behave under heat and inform studies on fossilization processes.
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Area of Science:
Background:
Prior research has shown that biogenic apatites, such as those in tooth enamel, exhibit distinct thermal behaviors. These materials contain structural water and carbonate ions that influence their stability under heat. However, no prior work had resolved the thermal decomposition of apatite in Lingula shells. This gap motivated a detailed comparison between Lingula apatite and human tooth enamel. The study aimed to clarify how structural parameters like lattice dimensions and crystallinity change during heating. The researchers also sought to determine the role of carbonate and hydroxyl groups in thermal stability. They examined the transformation to beta-tricalcium phosphate as a key indicator of decomposition. The study's novelty lies in its focus on a specific marine organism's shell composition. Understanding these thermal behaviors could help interpret fossilization processes and material degradation in natural settings.
Purpose Of The Study:
The study found that structural H2O in Lingula apatite is lost at lower temperatures than in human tooth enamel.
The transformation was measured using weight percent analysis at specific temperature intervals.
The loss of H2O at 200 degrees C indicates a drastic contraction of lattice parameters and reduced crystallinity.
It tracks OH stretching bands to assess the presence of hydroxyl groups in apatite samples.
The researchers aimed to investigate the thermal behavior of apatite in Lingula shells. They compared two species, Lu and Ls, and analyzed their apatite structure against human tooth enamel. The goal was to determine how structural parameters change with heat. They focused on lattice parameters, transformation to beta-TCP, and the loss of CO3, OH, and H2O. The study also aimed to assess the role of carbonate and halide ions in apatite stability. The researchers wanted to understand why H2O loss occurs at lower temperatures in Lingula apatite. They hypothesized that the structural water in Lingula apatite is loosely bound. This investigation could provide insights into biogenic apatite decomposition mechanisms.
Main Methods:
The study used thermal analysis techniques to observe apatite changes at high temperatures. The researchers heated samples of Lu and Ls apatite in air and N2 environments. They monitored lattice parameter changes using X-ray diffraction. Fourier-transform infrared spectroscopy tracked OH stretching bands. The transformation to beta-TCP was measured using weight percent analysis. The loss of H2O was quantified at various temperature intervals. The crystallinity of the apatite was assessed through diffraction patterns. The study compared the thermal responses of Lingula apatite with human tooth enamel.
Main Results:
The OH stretching band was absent in unheated and N2-heated apatites. Lu and Ls apatite produced 26 and 17 wt% of beta-TCP at 700 degrees C, respectively. Fifty to 60% of H2O was lost at 200 degrees C, leading to a drastic contraction of the a- and c-axes. This loss was accompanied by a significant decrease in crystallinity. The lattice parameters changed significantly during heating. The structural H2O in Lingula apatite was lost at lower temperatures than in tooth enamel. The apatite contained CO3 and F + Cl- ions, indicating a complex composition. These findings suggest that Lingula apatite decomposes differently from tooth enamel.
Conclusions:
The study shows that Lu and Ls shell apatite is CO3-containing F + Cl-apatite. The structural H2O in Lingula apatite is loosely bound and lost at lower temperatures than in tooth enamel. These findings suggest a unique thermal decomposition pathway for Lingula apatite. The transformation to beta-TCP occurs at 700 degrees C, with Lu producing more beta-TCP than Ls. The drastic contraction of lattice parameters at 200 degrees C indicates significant structural changes. The absence of OH stretching bands in dried N2-heated samples supports the hypothesis of loosely bound H2O. The study confirms that Lingula apatite differs from tooth enamel in thermal behavior. These results may inform future studies on biogenic apatite decomposition and fossilization processes.
It suggests that structural H2O is lost in dried N2 environments, supporting the hypothesis of loosely bound water.
Lingula apatite loses structural H2O at lower temperatures than tooth enamel.