Hyperion 2000

The infrared absorption spectra of the biofilm samples were surveyed using the infrared microspectroscopy (IRM) beamline (Australian synchrotron, Victoria, Australia) and the infrared spectroscopy beamline, Pohang Accelerator Laboratory (Pohang, Korea). To perform IR microspectroscopy, an IR spectrometer Bruker Vertex 80 v was used coupled to a FTIR microscope Hyperion 2000. Detection was performed with a liquid-nitrogen-cooled narrow-band mercury–cadmium–telluride MCT detector (Bruker Optik GmbH, Ettlingen, Germany). High-sensitivity spectral analysis was performed at the IMBUIA beamline of the fourth-generation storage ring Sirius, at the Brazilian Synchrotron Light Laboratory (Campinas, Brazil), using an Agilent Cary 660 FTIR microscope operating with a thermal source. All the synchrotron FTIR spectra were surveyed in the spectral range of 2000–700 cm⁻¹, with spectral resolution not lower than 4 cm⁻¹.

The mineralogy of precipitates was determined by powder X-ray diffraction (XRD) using a Rigaku D/max2550VB3+/PC diffractometer. The morphology of the precipitates was studied by scanning electron microscopy (SEM) using a Hitachi S-2360N. The composition of medium before and after precipitation was dried at 80°C and then analyzed by Fourier transform infrared spectroscopy (FT-IR) using a Bruker Hyperion 2000.

Three main analytical methods are employed for the estimation of the firing degree: XRD focusing on the specific peaks of clay minerals, FT-IR transmittance and reflectance measurements, micromorphological changes observed in BSE images from SEM.
FT-IR measurements were performed with Paragon 1000 PC by Perkin Elmer in transmission mode. For the sample preparation, powder from 116 ceramics selected from 158 samples were mixed with KBr and pelletized. The mid-IR curve is taken with 128 scans and a spectral resolution of 2 cm⁻¹ for wavenumbers between 450 and 4000 cm⁻¹. For this purpose, no smoothing filter was necessary. In order to focus more on the clay matrix within the heterogeneous mixed state of ceramic pastes, an IR-microscope (Bruker Hyperion 2000) attached to a Vertex 80 v FTIR-spectrometer and a MCT detector was employed to perform reflectance point analysis on the polished cross thin section of the 52 samples without carbon coating. Our main goal was the observation of Si-O stretching mode located between 900 and 1200 cm⁻¹. The IR aperture size was fixed to 70 × 70 µm², as this size was found to minimize the IR signal of the sand and silt grains and to maximize the signal of clay minerals. We performed 1024 scans with a spectral resolution of 2 cm^-1. A silver mirror was used as reference for the IR reflectance experiments.

The non-treated, demineralized, and remineralized dental specimens were studied with the infrared microscope Hyperion 2000, Bruker Optik, Ettlingen, Germany in a spectral range of 600–4000 cm⁻¹ with a 20× Schwarzschild objective in reflectance mode after accumulating 264 scans. Micro-infrared spectra were collected from five different areas, with mean size of 100 µm² for each sample.