R. S. Yadav

Publications

1 Properties of Cement Pastes with Different Particle Size Fractions of Metakaolin

Authors: M. Boháč, R. Novotný, F. Frajkorová, R. S. Yadav, T. Opravil, M. Palou

Abstract:

Properties of Portland cement mixtures with various fractions of metakaolin were studied. 10% of Portland cement CEM I 42.5 R was replaced by different fractions of high reactivity metakaolin with defined chemical and mineralogical properties. Various fractions of metakaolin were prepared by jet mill classifying system. There is a clear trend between fineness of metakaolin and hydration heat development. Due to metakaolin presence in mixtures the compressive strength development of mortars is rather slower for coarser fractions but 28-day flexural strengths are improved for all fractions of metakaoline used in mixtures compared to reference sample of pure Portland cement. Yield point, plastic viscosity and adhesion of fresh pastes are considerably influenced by fineness of metakaolin used in cement pastes.

Keywords: Rheology, cement, Calorimetry, Strength, metakaolin fineness

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Abstracts

5 Structural and Magnetic Properties of NiFe2O4 Spinel Ferrite Nanoparticles Synthesized by Starch-Assisted Sol-Gel Auto-Combustion Method

Authors: R. S. Yadav, I. Kuritka, J. Havlica, Z. Kozakova, J. Masilko, M. Hajdúchová, V. Enev, J. Wasserbauer, L. Kalina

Abstract:

Nickel spinel ferrite NiFe2O4 nanoparticles with different particle size at different annealing temperature were synthesized using the starch-assisted sol-gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction (XRD) spectroscopy, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Field-Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Vibrating Sample Magnetometer. The XRD patterns confirmed the formation of NiFe2O4 spinel ferrite nanoparticles. Field-Emission Scanning Electron Microscopy revealed that particles are of spherical morphology with particle size 5-20 nm at lower annealing temperature. An infrared spectroscopy study showed the presence of two principal absorption bands in the frequency range around 525 cm-1 (ν1) and around 340 cm-1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site related Raman modes in nickel ferrite nanoparticles with change of particle size. This change in magnetic behavior with change of particle size of NiFe2O4 nanoparticles was observed.

Keywords: Nanoparticles, magnetic property, nickel ferrite, NiFe2O4

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4 Structural and Magnetic Properties of CoFe2-xNdxO4 Spinel Ferrite Nanoparticles

Authors: R. S. Yadav, I. Kuritka, J. Havlica, Z. Kozakova, J. Masilko, M. Hajdúchová, V. Enev, J. Wasserbauer

Abstract:

In this present work, CoFe2-xNdxO4 (0.0 ≤ x ≥0.1) spinel ferrite nanoparticles were synthesized by starch-assisted sol-gel auto-combustion method. Powder X-ray diffraction patterns were revealed the formation of cubic spinel ferrite with the signature of NdFeO3 phase at higher Nd3+ concentration. The field emission scanning electron microscopy study demonstrated the spherical nanoparticle in the size range between 5-15 nm. Raman and Fourier Transform Infrared spectra supported the formation of the spinel ferrite structure in the nanocrystalline form. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Co2+ and Fe3+ at octahedral as well as a tetrahedral site in CoFe2-xNdxO4 nanoparticles. The change in magnetic properties with a variation of concentration of Nd3+ ions in cobalt ferrite nanoparticles was observed.

Keywords: Nanoparticles, spinel ferrites, sol-gel auto-combustion method, CoFe2-xNdxO4

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3 Properties of Cement Pastes with Different Particle Size Fractions of Metakaolin

Authors: M. Boháč, R. Novotný, F. Frajkorová, R. S. Yadav, T. Opravil, M. Palou

Abstract:

Properties of Portland cement mixtures with various fractions of metakaolin were studied. 10 % of Portland cement CEM I 42.5 R was replaced by different fractions of high reactivity metakaolin with defined chemical and mineralogical properties. Various fractions of metakaolin were prepared by jet mill classifying system. There is a clear trend between fineness of metakaolin and hydration heat development. Due to metakaolin presence in mixtures the compressive strength development of mortars is rather slower for coarser fractions but 28-day flexural strengths are improved for all fractions of metakaoline used in mixtures compared to reference sample of pure Portland cement. Yield point, plastic viscosity and adhesion of fresh pastes are considerably influenced by fineness of metakaolin used in cement pastes.

Keywords: Rheology, cement, Calorimetry, Strength, metakaolin fineness

Procedia PDF Downloads 244
2 Particle Size Dependent Magnetic Properties of CuFe2O4 Spinel Ferrite Nanoparticles Synthesized by Starch-Assisted Sol-Gel Auto-Combustion Method

Authors: R. S. Yadav, I. Kuritka, J. Havlica, Z. Kozakova, J. Masilko, M. Hajdúchová, V. Enev, J. Wasserbauer, L. Kalina

Abstract:

In this work, copper ferrite CuFe2O4 spinel ferrite nanoparticles with different particle size at different annealing temperature were synthesized using the starch-assisted sol-gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction (XRD) spectroscopy, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Field-Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, and Vibrating Sample Magnetometer. The XRD patterns confirmed the formation of CuFe2O4 spinel ferrite nanoparticles. Field-Emission Scanning Electron Microscopy revealed that particles are of spherical morphology with particle size 5-20 nm at lower annealing temperature. An infrared spectroscopy study showed the presence of two principal absorption bands in the frequency range around 530 cm-1 (ν1) and around 360 cm-1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site related Raman modes in copper ferrite nanoparticles with change of particle size. This change in magnetic behavior with change of particle size of CuFe2O4 nanoparticles was also observed. The change in magnetic properties with change of particle size is due to cation redistribution, which was confirmed by X-Ray photoelectron study.

Keywords: Nanoparticles, copper ferrite, magnetic property, CuFe2O4

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1 Size Dependent Magnetic Properties of CoFe2-xGdxO4 (x = 0.1) Spinel Ferrite Nanoparticles Synthesized by Starch-Assisted Sol-Gel Auto-Combustion Method

Authors: R. S. Yadav, I. Kuritka, J. Havlica, Z. Kozakova, J. Masilko, M. Hajdúchová, V. Enev, J. Wasserbauer

Abstract:

In this work, the effect of particle size on the structural and magnetic properties of CoFe2-xGdxO4 (x =0.1) spinel ferrite nanoparticles synthesized by starch-assisted sol-gel auto combustion method was investigated. The different sized CoFe2-xGdxO4 (x =0.1) spinel ferrite nanoparticles were achieved after annealing at different temperature 500, 700 and 900 oC. The structural phases, crystallite size and lattice parameter of synthesized ferrite nanoparticles were estimated from X-ray diffraction studies. The field emission scanning electron microscopy study demonstrated increase in particle size with increase of annealing temperature. Raman spectroscopy study indicated the change in octahedral and tetrahedral site related Raman modes in Gd3+ ions doped cobalt ferrite nanoparticles. An infrared spectroscopy study showed the presence of two absorption bands in the frequency range around 580 cm-1 (ν1) and around 340 cm-1 (ν2); which indicated the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Vibrating Sample magnetometer study showed that the saturation magnetization and coercivity changes with particle size of CoFe2-xGdxO4 (x =0.1) spinel ferrite.

Keywords: Nanoparticles, Magnetic Properties, Sol-Gel Synthesis, spinel ferrite

Procedia PDF Downloads 334