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
Today X-ray tomography and Ultrasound Synthetic Aperture Focusing Techniques are representative examples for defect imaging in the field of nondestructive testing. THz time domain spectroscopy (TDS) operates with short electromagnetic pulses. The sensitivity of the pulses to optical material property changes makes THz-TDS attractive for the detection of flaws in dielectric materials. Unfortunately, the X-ray computed tomography (CT) model holds only for THz-TDS reconstruction if minor refraction index differences between the inhomogeneities and the surrounding material matrix exist. A Time Domain SAFT algorithm has been developed to overcome the restrictions. THz time domain measurement on representative sample sets with inherent artefacts were performed to use them for the Image reconstructions. The results will be presented and compared with optical surface images of the used test objects to evaluate the SAFT algorithm in relation to the econstruction quality.
New developments in spectroscopic techniques for process control are, in general, driven by shortcomings of existing technology, for example, when sensitivity, selectivity, robustness, and so forth do not meet the demands. The perfect process analytical method would be based on a robust and easy to handle customized technique operating in real time, come without any need for calibration, that is, be an absolute method, have a professional support, and be compliant to increasing regulatory requirements. However, there are at least trends toward such an all-in-one device suitable for every purpose.
Small, low-field NMR systems equipped with permanent magnet technology have been developed and allow for quantitative analysis as on-line instruments in a production environment. Quantitative high-resolution on-line NMR spectroscopy contributes to process understanding in pilot plant and research environments.
Laser spectroscopy is a promising field in process analysis owing to its sensitivity and selectivity. Laser-induced breakdown spectroscopy LIBS is a promising field for direct in situ analysis and remote sensing. Applications of quantum-cascade lasers for process analytical applications are a promising technique. Techniques such as cavity ring-down spectroscopy (CRDS), tunable diode laser absorption spectroscopy (TDLAS), and photothermal techniques are briefly introduced.
Recent developments of new detectors have improved X-ray fluorescence analysis (XRF) for qualitative and quantitative on-line evaluation of the elementary composition of liquid or solid samples, regardless of whether compact or bulk material.
The chapter also introduces miscellaneous techniques such as ion mobility spectroscopy (IMS), microwave and dielectric spectroscopy, terahertz spectroscopy, ultrasonic acoustic spectroscopy, and other methods.