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- Infrared spectroscopy (2)
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- THz spectroscopy (2)
Organisationseinheit der BAM
Novel Technique for On-Line Monitoring of the Curing Process of Fiber Reinforced Polymer Composites
(2021)
A specially developed experimental set up has been integrated into a commercially available FT IR Spectrometer to study the curing of Epoxy Systems. MIR and FIR spectra measured during the curing process at different temperatures of an epoxy system will be presented in dependency of the curing time. The experiments and the selected set up are discussed to demonstrate its potential for future monitoring and ageing control applications during a manufacturing process of polymer composites.
Removal of Etalon Features in the Far-Infrared–Terahertz Transmittance Spectra of Thin Polymer Films
(2020)
Etalon features in infrared spectra of stratified samples, their influence on the interpretation and methods to circumvent their presence in infrared spectra have been in discussion for decades. This paper focuses on the application of a method originally developed to remove interference fringes in the mid-infrared spectra for far-infrared Fourier transform spectroscopy on thin polymer films. We show that the total transmittance-reflectance technique, commonly used for mid-infrared, also works successfully in the far infrared spectral range where other approaches fail. Experimental spectra obtained by such technique are supported by model calculations and reveal the possibility and limits to obtain almost undisturbed far-infrared spectra which are suitable to determine low energy vibrations of ionomer salts under certain sample conditions.
Etalon effects in THz transmittance spectra, either taken in time-domain or frequency-domain, often hamper or even hinder the interpretation of film properties. In this paper we discuss the transferability and applicability of spectroscopic methods usually employed in the near and mid infrared spectral range and exemplarily present the application field.
Etalon effects in THz transmittance spectra, either taken in time- domain or frequency-domain, often hamper or even hinder the interpretation of film properties. In this paper we discuss the transferability and applicability of spectroscopic methods typically employed in the near and mid infrared spectral range to eliminate the fringes in the transmittance spectra in the THz spectral range.
Etalon features in transmittance spectra of films arise due to the coherent superposition of waves caused by reflections multiple times at the inner film boundaries. The fringe maxima occur at i𝜆 = 2nd cos 𝜑 with i - being an integer, 𝜆 - the wavelength, d - the film thickness, 𝜑 - the angle of incidence in respect to the film normal and n - the refractive index of the film. It is obvious that such features can hinder the interpretation of absorption bands when fringe amplitude and period are in the same range as the expected bands.
This poster discusses the suitability of two optical methods for the THz spectral range applied to Fourier Transform Spectroscopy.
The far infrared refractive indices and the extinction coefficients of liquids can be obtained by means of spectroscopic ellipsometry in attenuated total reflection configuration. Such optical constants will contribute to a spectroscopic data base in the far infrared and terahertz spectral regions. The experimental implementation and the calibration procedure of the method are described in detail. The temperature dependency of the optical constants for water over a broad spectral range is exemplarily presented.
Optical constants of harmful and highly energetic liquids for application to THz screening systems
(2016)
The far-infrared (IR) optical constants of a set of hazardous and flammable liquids have been obtained by means of spectroscopic ellipsometry in attenuated total reflection configuration over a broad spectral range. Such liquids recently became of considerable concern for transportation security measures worldwide. Their optical identification at check-in gates can only become possible if the characteristic spectra are already known. The refractive indices and the extinction coefficients reported here contribute to a spectroscopic data base in the far-IR and terahertz (THz) spectral regions and may support modeling the performance of THz screening systems on liquids for airports and other security sensitive areas. Examples of several container material/liquid systems are discussed. From the measured optical constants typical THz waveforms are calculated and discussed.
THz and Mid IR Fourier transform spectroscopy on polyethylene irradiated with Gamma- Co60 radiation
(2014)
THz and mid IR spectroscopy of high molecular PE (HMW) and ultra high molecular PE (UHMW) reveals modifications of the molecular structure induced by γ-Co60 radiation. UHMW-PE and HMW-PE can be distinguished. The integral absorption in the B1u THz-region can quantitatively describe the amorphization of crystallinity. The formation of trans vinylene unsaturations and the decay of vinyl can be followed by mid IR spectroscopy