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Segmented radial seals are modern technologies used in aeronautic engines and space turbopumps. They consist of several circumferential segments assembled as an annular ring freely mounted on the rotor. A circumferential (garter) spring tightens the segments around the shaft. The segments can move radially relative to each other, sliding against a casing and following the dynamic displacements of the rotor. Two similar segmented seals made of different materials were tested. The results showed different leakage flow rates and different correlations between leakage and wear rate. For example, the leakage rate decreases with wear for one seal and increases for the other. For explaining these results, wear was correlated with the microstructure of the materials of the two seals. Profilometric analyses were made for the two seals, highlighting that wear was not localised in the same areas. Raman spectra maps were taken on the pads of the segment in contact with the rotor and microstructural changes caused by friction were enlightened. The evolution of residual stresses was measured for new and worn segments. These findings strengthen the results obtained from profilometric wear analyses. They also allow a more precise understanding of tribological degradation scenarios depending on the operating conditions and the properties of the material.

In the current study, a green and facile route for the synthesis of iron nanoparticles (FeNPs) was adopted. The FeNPs were fabricated via a single step green route using aqueous leaves extract of Plumeria obtusa (P. obtusa) as a capping/reducing and stabilizing agents. The FeNPs were characterized by UV/Vis (Ultraviolet/Visible), FTIR (Fourier Transform Infra-Red spectroscopy), TEM (Transmission Electron Microscopy), SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) techniques. The FeNPs were of spheroidal shape with average size of 50 nm. The biosynthesized FeNPs were further evaluated for their biological activities like antimicrobial, antioxidant and biocompatibility. The FeNPs displayed auspicious antimicrobial activity against bacterial (E. coli, B. subtilis) and fungal strains (A. niger) and S. commune. The test performed against red blood cells (RBCs) lysis (1.22 ± 0.02%) and macrophage (31 ± 0.09%) showed biocompatible nature of FeNPs. In vitro cytotoxicity against AU565 (82.03 ± 0.08–23.65 ± 0.065%) and HeLa (88.61 ± 0.06–33.34 ± 0.06%) cell lines showed cell viability loss in dose dependent manner (FeNPs 25–100 μg/mL). The antioxidant activities values were determined through DPPH, TRPA, NO and H2O2 assays with values 70.23 ± 0.02%, 76.65 ± 0.02 μg AAE/mg, 74.43 ± 0.04% and 67.34 ± 0.03%, respectively. Based on the bioactivities, the green synthesized FeNPs have potential for therapeutic applications.

In the present work, Zinc Oxide (ZnO) nanoparticles (NPs) were synthesized by the chemical co-precipitation method using Zinc Chloride as the initial chemical, while Nickel and Cobalt chloride as dopants. Phase identification of metal (Ni, Co) doped Zinc Oxide nanoparticles (NPs) was observed using x-ray diffraction (XRD). The small lattice distortion or phase changes appeared due to shifting of diffraction angles peaks towards larger angle in ZnO are corresponded to metal (Ni, Co) dopant. The average crystallite size appears to decrement in NP size from 7.67 nm to 6.52 nm and 5.35 nm to 5.17 nm with increasing 5 % to 80 % of metal (Ni, Co) dopant respectively. The optical characteristics, including the absorption spectra of the prepared sample were observed through UV–Vis spectroscopy, Meanwhile SEM confirmed the observation of composition change in specimen with metal (Ni, Co) dopant concentration. The bandgap value was also found decrement 5.23 eV to 5.05 eV with increment of metal (Ni, Co) dopant concentration. The functional groups were measured by Fourier transformation infrared spectroscopy (FTIR). FTIR peaks found the metal (Ni, Co) doped ZnO with the vibration mode of (Zn2+ –O2−) ions due to the increment of dopant concentrations. Furthermore, electrical results show the ohmic behavior of prepared samples. These findings indicate the possibility of tuning optical, structural and electrical properties of metal (Ni, Co) doped ZnO with various dopant concentrations of Nickel and will have great potential to find application in optoelectronic devices.