• L JOHN BERCHMANS

      Articles written in Bulletin of Materials Science

    • Gas sensing behaviour of cerium oxide and magnesium aluminate composites

      N NITHYAVATHY V RAJENDRAN L JOHN BERCHMANS M MAAZA S KRITHIKA S ARUNMETHA

      More Details Abstract Fulltext PDF

      Composites of cerium oxide (CeO$_2$) and magnesium aluminate (MgAl$_2$O$_4$) were prepared by the moltensalt synthesis (MSS) method at 1130 K. The composite samples were named as MA, MAC0.07 and MAC0.14 (at CeO$_2$:0, 0.07 and 0.14 g in MgAl$_2$O$_4$, respectively) and these were characterized by X-ray diffraction and energy-dispersiveX-ray analyses. It is seen that the microstructure of the composite samples are quite similar except for a small increasein particle size. The energy-dispersive X-ray analyses provide the presence of concentration of Ce, Mg, Al and O in thecomposite. Scanning electron microscope, coupled with energy-dispersive X-ray analysis (SEM-EDAX) was used to identifythe morphology, microstructure and elemental composition of the prepared samples. The decomposition and dissociationreactions of the precursors were determined using differential thermal and thermogravimetric analysis (TGA). A lone pairof the electron state was identified from the electro paramagnetic resonance spectrum. An optical energy band gap of 3.3 eV was calculated from the UV–Vis absorbance spectra. The gas response to changes in oxygen (O$_2$), carbon monoxide (CO) (at 0.5, 1.0 and 1.5 bar) and ethanol (at 50 and 100 ppm) was quantitatively analysed in all the samples at differentoperating temperatures (300-500 K). The magnitude of the temperature varied linearly regardless of the gas pressure insidethe chamber, by increasing the supply in the heating pad, mounted below the sensor sample. The composite samples indicatea good response to different gases with detection of the smallest change in gas pressure.

    • Investigations on oxidation, hot corrosion and thermal gradient performance of low k-La$_2$Mo$_2$O$_9$ thermal barrier coating

      N DHARUMAN M ARULMOZHI MUKIRI SOBAN BABU L JOHN BERCHMANS GOSIPATHALA SREEDHAR

      More Details Abstract Fulltext PDF

      In this work, La$_2$Mo$_2$O$_9$ (LMO) powder was synthesized via the molten salt procedure. The coatings of NiCrAlY/LMO, NiCrAlY/YSZ and NiCrAlY/YSZ/LMO were developed by the plasma-spray process. The NiCrAlY/LMO coating demonstrated higher oxidation and hot corrosion rates than those of NiCrAlY/YSZ and NiCrAlY/YSZ/LMO coatings. The higher oxidation and hot corrosion rates are attributed to higher ionic conductivity of LMO in the NiCrAlY/LMO coating. The NiCrAlY/YSZ/LMO coating demonstrated the lowest oxidation and hot corrosion rates, while NiCrAlY/YSZ coating exhibited an intermediate behaviour. Further, the coating also showed higher thermal gradientperformance. The high oxidation, hot corrosion resistance and thermal gradient performance achieved due to the suppression of ionic conductivity by YSZ buffer layer in the multi-layer coating. The present work paves new pathways for the development of plasma spray coatings with low thermal conductivity oxides for the rapid heating application of thermal barrier coatings.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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