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Polychlorotrifluoroethylene is used as a coating material over metallic seals in low-temperature applications to arrest fluid leakage from the impeller side in turbopumps. Typically, polychlorotrifluoroethylene coating is applied on V-type seals, with a thickness ranging from 80 to 130 μm by spraying an emulsion over the substrate followed by heat treatment. An attempt has been made to measure the polychlorotrifluoroethylene coating thickness over V-type seals using terahertz time-domain spectroscopy in reflection geometry, a noncontact, non-invasive NDT method. When the terahertz pulse from a transmitter photo-conductive antenna is incident on the V-type seal, it penetrates through the polychlorotrifluoroethylene coating. It gets reflected from the coating/base coat interface. Here, the reflected echoes from the air-to-polychlorotrifluoroethylene coating interface and polychlorotrifluoroethylene coating to the basecoat interface get overlapped in the time domain as the polychlorotrifluoroethylene coating layer is very thin. The sparse deconvolution technique separates the individual reflected signals and obtains the time delay signals from various interfaces. From the estimation of time delay values, the thickness of the coating has been computed using the refractive index value extracted using terahertz time-domain spectroscopy in transmission mode before the reflection measurements. The obtained thickness values are in close agreement with the coating thickness measured using optical microscopy. [ABSTRACT FROM AUTHOR]

We adopt co-evaporation method for the deposition of copper tin sulfide (Cu2SnS3) thin films at a constant substrate temperature of 250 0C. The film thickness was varied in the range of 285-910 nm. The physical properties of Cu2SnS3 films were studied using appropriate characterization techniques. The XRD analysis reveals the tetragonal crystal structure of Cu2SnS3 films. The SEM images show the granular shaped crystallites distributed entire surface of the films. The energy band gap of the films are in the range of 1.73 -1.10 eV. Significant improvements in electrical properties are observed for the ptype conducting CTS films with thickness. The reduction in band gap to near optimum value along with the improved electrical properties enhances the prospects of Cu2SnS3 as a prospective absorber layer for solar cells. Photodetectors have been fabricated using the sample of thickness 496 nm. The photoresponse parameters such as photoconductivity (s), sensitivity(s), specific detectivity (D), External Quantum Efficiency (EQE) and responsivity (R) were calculated for the device of glass/CTS/Ag from the I-V measurement under the illumination of 100 mW/cm² white light source. [ABSTRACT FROM AUTHOR]

ZnO nanostructures consisting of nanowires and nanorods have been grown by aqueous chemical growth (ACG) process on the ZnO seed layers. ACG process has been carried out for 5 h and 15 h to obtain the one dimensional nanostructures. This ZnO nanostructure comprises mixture of vertically aligned nanorods and nanowires. Structural analysis reveals that the crystal orientation is along (002) plane exhibiting a hexagonal wurtzite structure. The crystallinity of ZnO nanostructures increases after aqueous chemical treatment with respect to the growth duration. Optical studies revealed that when the duration of aqueous chemical treatment is increased, the transmittance of the films decreases considerably. The as-deposited ZnO seed layers exhibit electron carrier concentration of 4.69 x 1014 cm-3 and the value increases to 9.44 x 1015 cm-3 after 5 h and 1.53 x 1016 cm-3 after 15 h of aqueous chemical treatment. It has been observed that ZnO nanostructures exhibit enhanced luminescence properties in visible region which covers the entire visible region of the spectrum. [ABSTRACT FROM AUTHOR]