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- 2017 (3) (entfernen)
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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.
Implementation of Ba0.6Sr0.4TiO3-ZnO-B2O3 based tunable microwave phase shifters in LTCC technology
(2017)
Tunable dielectric Ba0.6Sr0.4TiO3-ZnO-B2O3 thick-films were analyzed regarding their integration potential into the LTCC technology. Therefore, tunable loaded line phase shifters based on metal-insulator-metal varactors with single- and double- printed BST thick-films were fabricated and co-sintered inside a four layer LTCC module. Microstructural and chemical investigations showed a sufficient compatibility and adhesion between the silver, BST composite and LTCC layers and a resulting morphology depending on the processing route. The microwave characterization of the LTCC-embedded phase shifters revealed comparable results to phase shifters with the same design on alumina substrates.
THz applications for NDT
(2017)
Electromagnetic waves in the frequency range between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials, to operate contactless and to be non-ionizing as well as be-ing insensitive to ambient temperatures makes THz technologies for NDT applications attractive especially where other techniques are not available or less suitable. Today T-rays are applied in non-destructive testing for quality control and condition monitoring issues. The operation is based on the combination of both transmission and/or reflection measurements and specially developed reconstruction procedures. Firstly, THz-TDS measurements will be presented to demonstrate the opportunities for spectroscopy and imaging of polymer materials. A SAFT algorithm and an Optical Layer-Model will be presented and discussed in more detail to demonstrate the opportunities of image reconstruction for visualization of the inner structures of op-tically and far infra-red opaque polymer composites.