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M. Manhas,Vinay Kumar,Vivek K. Singh,J. Sharma,Ram Prakash,Vishal Sharma,A.K. Bedyal,H.C. Swart 한국물리학회 2017 Current Applied Physics Vol.17 No.11
The present paper reports on the structural and luminescent properties of un-doped and Sm3þ doped Ba2Ca(BO3)2 phosphors synthesized by the conventional solid state method. For structural characterizations, the X-ray diffraction, FTIR spectroscopy and Rietveld refinement method were used. The FTIR spectrum was composed of basic BO3 and BO4 structural units of borates. The Sm3þ doped phosphors under 402 nm (6H5/2/4L13/2) excitation, showed an orange red emission corresponding to the 601 nm (4G5/2 / 6H7/2) transition of the Sm3þ ion. An increase in the PL emission intensity was observed up to 2 mol % with the increase in Sm3þ ions concentration. The critical distance between the Sm3þ e Sm3þ ions were found to be 24.36 Å. Moreover, the phosphors decaytime and optical bandgap at different concentration of Sm3þ ion also have been discussed in details. All the results show that Ba2Ca(BO3)2:Sm3þ phosphor may be used with a near ultraviolet (n-UV) chip to fill the amber gap in light emitting diodes (LEDs).
V. Jothi,Akeem Yusuf Adesina,A. Madhan Kumar,J. S. Nirmal Ram 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.11
This study aims to evaluate the influence of dicarboxylic acids (oxalic, malonic and succinic acid) used in anodizationbath on the surface and corrosion resistant performance of anodized films on AA2024 aerospace grade alloys. The surfacemorphology, topography, composition and structure of anodized samples were examined by scanning electron microscopy,optical profilometer, X-ray diffraction and attenuated total reflectance-infrared techniques. Characterization results revealedthe effect of dicarboxylic acids addition on the anodized film’s surface with important changes. X-ray Photoelectron Spectroscopicanalysis confirmed the presence of carboxylic groups on the porous anodized layer processed in anodization bathcontaining succinic acid. The electrochemical corrosion tests specified a solid relationship between the corrosion resistanceand the surface microstructure of the anodized layer processed in different dicarboxylic acids.
The role of potassium tellurite as tellurium source in mercaptoacetic acid-capped CdTe nanoparticles
M.S. Abd El-sadek,J. Ram Kumar,S. Moorthy Babu 한국물리학회 2010 Current Applied Physics Vol.10 No.1
Water-soluble CdTe nanoparticles were synthesized in aqueous solution with the assistance of mercaptoacetic acid (MAA) molecules by wet chemical route and microwave-assisted method. A series of cadmium telluride (CdTe) nanoparticles capped with a bifunctional molecule, which contains both thiols and carboxylic acid groups were prepared using different pH values and using potassium tellurite as tellurium source. Thiol-capped nanocrystals of CdTe can be isolated as powders using 2-propanol. The synthesized thiol-capped CdTe were characterized with EDAX, TEM, Raman, FT–IR, UV–Visible absorption,fluorescence spectroscopy and X-ray diffraction (XRD) for the particle size determination and to understand their optical properties. The particles crystallize predominantly in cubic phase with narrow photoluminescence emission. Potassium tellurite as source of tellurium improves the photoluminescence efficiency and also avoids the cumbersome processes associated with H2Te or NaHTe sources.
P. Thakur,W. K. Choi,K. H. Chae,J.-Y. Kim,R. J. Choudhary,Shailja Tiwari,Ram Prakash,D. M. Phase,Ravi Kumar 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
We report on the growth and the characterization of magnetite thin films grown on Si(111) substrates by using pulsed laser deposition at different substrate temperatures (TS = 350, 450 and 550 ℃) by performing X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) experiments. The O K− and Fe L3,2−edge XAS spectra reveal that the couplings of the O 2p with Fe 3d orbitals highly rely on the growth processes. The XMCD data of well-characterized thin films exhibit characteristic contributions from Fe3+ A ions in tetrahedral sites and Fe2+ B and Fe3+ B ions in octahedral sites and have spectral features similar to those of the Fe3O4 single crystal. The temperature dependence of the XMCD line shape features remain unchanged below and above the Verwey transition. These investigations demonstrate the experimental conditions for controlled growth of Fe3O4 thin films on Si(111) substrates and suggest that the Fe3O4/Si(111) might a promising spintronic materials for future technology.