• K C Patil

      Articles written in Bulletin of Materials Science

    • Combustion synthesis and properties of fine particle fluorescent aluminous oxides

      J J Kingsley N Manickam K C Patil

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      Fine particle fluorescent aluminous oxide materials like Cr3+-doped α-Al2O3 (ruby), MgAl2O4, LaAlO3, Y3Al5O12 and Ce3+-doped Y3Al5O12, LaMgAl11O19, CaAl12O19 and CeMgAl11O19 have been prepared by the combustion of the corresponding metal nitrate-aluminium nitrate-urea/carbohydrazide mixtures at 500°C in less than 5 min. Formation of these Cr3+- and Ce3+-doped aluminous oxides has been confirmed by their characteristic XRD, colour, UV-visible and fluorescence spectra as well as decay time measurements. Ruby (Cr3+/α-Al2O3) powder showed characteristic excitation bands at 406 and 548 nm and emission band at 695 nm with the decay time of 3·6 ms.

    • Advanced ceramics: Combustion synthesis and properties

      K C Patil

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      Fine-particle ceramic powders such as chromites, manganites, ferrites, cobaltites, aluminas (α-Al2O3, Cr3+/Al2O3, zirconia-toughened alumina, mullite and cordierite), ceria, titania, zirconia (t, m, c and PSZ), dielectric oxides (MTiO3, PZT and PLZT) as well as highTc cuprates have been prepared by the combustion of redox compounds or mixtures. The combustion-derived oxide materials are of submicron size with a large surface area and are sinteractive.

    • Combustion synthesis of oxide materials for nuclear waste immobilization

      M Muthuraman N Arul Dhas K C Patil

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      Oxide materials like perovskite, zirconolite, hollandite, pyrochlore, NASICON and sphene which are used for nuclear waste immobilization have been prepared by a solution combustion process. The process involves the combustion of stoichiometric amount of corresponding metal nitrates and carbohydrazide/tetraformyl trisazine/diformyl hydrazide at 450°C. The combustion products have been characterized using powder X-ray diffraction, infrared spectroscopy, and29Si MAS-NMR. The fine particle nature of the combustion derived powders has been studied using density, particle size, BET surface area measurements and scanning electron microscopy. Sintering of combustion derived powder yields 85–95% dense ceramics in the temperature range 1000°–1300°C.

    • An electron spin resonance study of Mn2+ doped calcium hydrazine carboxylate monohydrate

      M M Abdel Gawad G V Mahesh K C Patil S V Bhat

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      Single crystals of calcium hydrazine carboxylate, monohydrate have been studied by ESR of Mn2+ doped in the calcium sites. X-band ESR indicated a large crystal field splitting necessitating experiments at Q band. The analysis shows two magnetically inequivalent (but chemically equivalent) sites withgxx = 2.0042±0.0038,gyy=2.0076 ±0.0029,gzz=2.0314±0.001,Azz=0.0099±0.0002 cm−1,Axx=0.0092±0.0002 cm−1,Ayy=0.0082±0.0002 cm−1,D=3/2Dzz=0.0558±0.0006 cm−1, andE=1/2 (DyyDyy)=0.0127±0.0002 cm−1.

      One of the principal components of the crystal field, (Dzz), is found to be along the Ca ↔ Ca direction in the structure and a second one, (Dxx), along the perpendicular to the plane of the triangle formed by three neighbouring calciums. TheA tensor is found to have an orientation different from that of theg andD tensors reflecting the low symmetry of the Ca2+ sites.

    • Synthesis and properties of rare earth doped lamp phosphors

      S Ekambaram K C Patil

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      Red, blue and green emitting lamp phosphors such as Eu3+ doped Y2O3 (red phosphor), Eu2+ doped Ba0·64Al12O18·64, BaMgAl10O17 and BaMg2Al16O27 (blue phosphors) and Ce0·67Tb0·33MgAl11O19 and Eu2+, Mn2+ doped BaMgAl10O17 (green phosphors) have been prepared by the combustion of the corresponding metal nitrates (oxidizer) and oxalyl dihydrazide/urea/carbohydrazide (fuel) mixtures at 400°–500°C within 5 min. The formation of these phosphors has been confirmed by their characteristic powder X-ray diffraction patterns and fluorescence spectra. The phosphors showed characteristic emission bands at 611 nm (red emission), 430–450 nm (blue emission) and 515–540 nm (green emission). The fine-particle nature of the combustion derived phosphors has been investigated using powder density, particle size and BET surface area measurements.

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