Lucian Diamandescu | National Institute of Materials Physics (original) (raw)

Papers by Lucian Diamandescu

Ceramics International, 2016

Abstract The influence of the CoFe 2 O 4 nanoparticles concentration in silica matrix on the stru... more Abstract The influence of the CoFe 2 O 4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe 2 O 4 /(100−x)SiO 2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe 2 O 4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe 2 O 4 nanoparticles have spherical shapes and size in the 6–35 nm range. The Mossbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe 2 O 4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.

Topics in Catalysis, 2009

TiO2 nanopowders, doped with Fe3+ and Eu3+ were obtained by high-energy ball milling and their ph... more TiO2 nanopowders, doped with Fe3+ and Eu3+ were obtained by high-energy ball milling and their physical properties were investigated as a function of the doping content and ball milling time. A noticeable red shift and high photoactivity in the degradation and catalytic oxidation reactions of styrene and phenol were found for all doped specimens.

Magnetochemistry

Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization met... more Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy and magnetic measurements. The XRD results revealed that the average crystallite size is 5.77 nm for CoFe1.8Tb0.2O4 and 6.42 nm for CoFe1.8Er0.2O4. Distribution of metal cations in the spinel structure estimated from X-ray diffraction data showed that the Tb3+ and Er3+ ions occupy the octahedral sites. TEM images indicated the presence of polyhedral particles with average size 5.91 nm for CoFe1.8Tb0.2O4 and 6.80 nm for CoFe1.8Er0.2O4. Room temperature Mössbauer spectra exhibit typical nanoscaled cobalt ferrite spectra in good agreement with XRD and TEM data. The saturation magnetization value (Ms) is 60 emu/g for CoFe1.8Tb0.2O4 and 80 emu/g for CoFe1.8Er0.2O4. CoFe1.8...

Journal of Magnetism and Magnetic Materials, 2002

The low-temperature behavior of the Co-doped magnetite is studied. The Fe 3Àx Co x O 4 powders (x... more The low-temperature behavior of the Co-doped magnetite is studied. The Fe 3Àx Co x O 4 powders (x ¼ 0:0121) have been prepared by the hydrothermal method. In order to investigate the cobalt influence on the structure of magnetite, transmission M. ossbauer spectroscopy measurements were performed at temperatures close and below the Verwey transition temperature characteristic for pure magnetite (122 and 77 K, respectively). All spectra were fitted with five components and related to nonequivalent Fe 2+ and Fe 3+ sites. The hyperfine parameters of these sites as well as their relative fractions in the powder samples were determined.

TiO2‐Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 ... more TiO2‐Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 nm) were successfully synthesized using a sol‐gel procedure, and were tested for salicylic acid photodegradation under UV irradiation. The structure and morphology of the obtained materials were investigated using X‐ray diffraction, transmission electron microscopy, and N2 adsorption‐ desorption measurements. UV‐Vis spectroscopy was used to study the optical properties. The effects of the gold nanoparticles on the TiO2 crystallization process were twofold, as follows: (i) the number of crystallized zones was strongly related to the concentration of the gold nanoparticles, and (ii) the smaller gold particles increased the time taken for the crystallization of the samples. It was found that the noble metal‐doped samples exhibited higher degradation rates compared with bare titania. It was found that the most active photocatalyst in each studied system was the sample with the highest concen...

Nanomaterials

Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precu... more Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precursor xerogel was characterized by thermal analysis. Bi1−xEuxFeO3 (x = 0–0.20) powders obtained after thermal treatment of the xerogel at 600 °C for 30 min were investigated by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Mössbauer spectroscopy. Magnetic behavior at room temperature was tested using vibrating sample magnetometry. The comparative results showed that europium has a beneficial effect on the stabilization of the perovskite structure and induced a weak ferromagnetism. The particle size decreases after the introduction of Eu3+ from 167 nm for x = 0 to 51 nm for x = 0.20. Photoluminescence spectroscopy showed the enhancement of the characteristic emission peaks intensity with the increase of Eu3+ concentration.

International Journal of Molecular Sciences

The advancement of nanotechnology in the last decade has developed an abundance of novel and intr... more The advancement of nanotechnology in the last decade has developed an abundance of novel and intriguing TiO2-based nanomaterials that are widely used in many sectors, including industry (as a food additive and colorant in cosmetics, paints, plastics, and toothpaste) and biomedicine (photoelectrochemical biosensing, implant coatings, drug delivery, and new emerging antimicrobial agents). Therefore, the increased use of engineered nanomaterials in the industry has raised serious concern about human exposure and their unexpected cytotoxic effects. Since inhalation is considered the most relevant way of absorbing nanomaterials, different cell death mechanisms induced in MRC-5 lung fibroblasts, following the exposure to functionalized TiO2 NPs, were investigated. Long-term exposure to TiO2 nanoparticles co-doped with 1% of iron and nitrogen led to the alteration of p53 protein activity and the gene expression controlled by this suppressor (NF-kB and mdm2), DNA damage, cell cycle disrupti...

Industria Textila

The objective of this study is to investigate the methods to create durable self-cleaning textile... more The objective of this study is to investigate the methods to create durable self-cleaning textiles by coating fabrics with TiO2-(1%)Fe-N-graphene (2%). To improve the adherence of the nanoparticles, the polyester/cotton woven fabrics were pre-treated with polyacrylic acid (PA), carboxymethylcellulose (CMC) and polyethylene polyamine resin (EZF). The pre-treated materials were immersed in a doped TiO2 for 30 minutes at 40oC and dried at 125oC. The finished fabrics were stained with methylene blue dye and exposed to visible light. The SEM images show the presence of particles on polymers layers firmly attached on the material surface. The treatments determine the decrease of the exothermic peak (452.48oC), characteristic of the cellulose decomposition, demonstrating an increase of the thermal conductivity of the materials. The doped TiO2-graphene induces a double degradation of methylene blue in comparison with untreated material and the materials treated with CMC, polyacrylic acid an...

Journal of Physics and Chemistry of Solids

MRS Proceedings

Nanostructured magnetite/T multilayers, with T = Ni, Co, Cr, have been prepared by pulsed laser d... more Nanostructured magnetite/T multilayers, with T = Ni, Co, Cr, have been prepared by pulsed laser deposition. The thickness of individual magnetite and metal layers takes values in the range of 5 - 40 nm with a total multilayer thickness of 100 -120 nm. X-ray diffraction has been used to study the phase characteristics as a function of thermal treatment up to 550 °C. Small amounts of maghemite and hematite were identified together with prevailing magnetite phase after treatments at different temperatures. The mean grain size of magnetite phase increases with temperature from 12 nm at room temperature to 54 nm at 550 °C. The thermal behavior of magnetite in multilayers in comparison with powder magnetite is discussed.

Journal of Alloys and Compounds

Journal of Minerals and Materials Characterization and Engineering

xMoO 2-(1-x)α-Fe 2 O 3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successf... more xMoO 2-(1-x)α-Fe 2 O 3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successfully synthesized by mechanochemical activation of MoO 2 and α-Fe 2 O 3 mixtures for 0-12 hours of ball milling time. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of the molybdenum dioxide-hematite nanoparticle system under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the crystallite size and lattice parameters as function of milling times and indicated the presence of Mo-substituted hematite and Fe-doped molybdenum dioxide at long milling times. The Mössbauer studies yielded the magnetic hyperfine fields and the relative abundance of a quadrupole-split doublet as function of the milling time for all molar concentrations involved. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in a magnetic field of 200 Oe.

Physical chemistry chemical physics : PCCP, Jan 17, 2018

The formation of separate phases in crystalline materials is promoted by doping with elements wit... more The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O3 (x = 0.00, 0.03, 0.04, 0.05) by means of a combination of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy. We found that Fe ions are substituted as Fe3+ at Ti sites and preferentially exhibit pentahedral coordination, whereas Ti ions have coexisting valences of Ti4+/Ti3+. Fe3+ ions are preferentially ordered in clusters, and there exists a transition temperature TC1, below which phase separation occurs between a tetragonal phase T1 free of magnetic clusters and a cubic phase, an...

Superlattices and Microstructures, 2017

Ceramics International, 2016

Materials Research Bulletin, 2017

Materials Characterization, 2010

Rutile-doped hematite xTiO2(1−x)α-Fe2O3 (x=0.0–1.0) nanostructures were synthesized using mechano... more Rutile-doped hematite xTiO2(1−x)α-Fe2O3 (x=0.0–1.0) nanostructures were synthesized using mechanochemical activation by ball milling. Their complex structural, magnetic and thermal properties were characterized by X-ray diffraction, Mössbauer spectroscopy and simultaneous DSC–TGA. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. For the molar concentrations x=0.1 and 0.3, the Mössbauer spectra were fitted

Physica B Condensed Matter, Oct 1, 2008

Cerium-doped hematite particles of the type xCeO2-(1−x)α-Fe2O3 (x=0.1, 0.5) were synthesized usin... more Cerium-doped hematite particles of the type xCeO2-(1−x)α-Fe2O3 (x=0.1, 0.5) were synthesized using mechanochemical activation and characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). XRD patterns yielded the dependence of lattice parameters and particle size as a function of ball milling time for each value of the molar concentration x. For x=0.1, the Mössbauer spectra were fitted

Ceramics International, 2016

Abstract The influence of the CoFe 2 O 4 nanoparticles concentration in silica matrix on the stru... more Abstract The influence of the CoFe 2 O 4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe 2 O 4 /(100−x)SiO 2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe 2 O 4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe 2 O 4 nanoparticles have spherical shapes and size in the 6–35 nm range. The Mossbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe 2 O 4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.

Topics in Catalysis, 2009

TiO2 nanopowders, doped with Fe3+ and Eu3+ were obtained by high-energy ball milling and their ph... more TiO2 nanopowders, doped with Fe3+ and Eu3+ were obtained by high-energy ball milling and their physical properties were investigated as a function of the doping content and ball milling time. A noticeable red shift and high photoactivity in the degradation and catalytic oxidation reactions of styrene and phenol were found for all doped specimens.

Magnetochemistry

Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization met... more Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy and magnetic measurements. The XRD results revealed that the average crystallite size is 5.77 nm for CoFe1.8Tb0.2O4 and 6.42 nm for CoFe1.8Er0.2O4. Distribution of metal cations in the spinel structure estimated from X-ray diffraction data showed that the Tb3+ and Er3+ ions occupy the octahedral sites. TEM images indicated the presence of polyhedral particles with average size 5.91 nm for CoFe1.8Tb0.2O4 and 6.80 nm for CoFe1.8Er0.2O4. Room temperature Mössbauer spectra exhibit typical nanoscaled cobalt ferrite spectra in good agreement with XRD and TEM data. The saturation magnetization value (Ms) is 60 emu/g for CoFe1.8Tb0.2O4 and 80 emu/g for CoFe1.8Er0.2O4. CoFe1.8...

Journal of Magnetism and Magnetic Materials, 2002

The low-temperature behavior of the Co-doped magnetite is studied. The Fe 3Àx Co x O 4 powders (x... more The low-temperature behavior of the Co-doped magnetite is studied. The Fe 3Àx Co x O 4 powders (x ¼ 0:0121) have been prepared by the hydrothermal method. In order to investigate the cobalt influence on the structure of magnetite, transmission M. ossbauer spectroscopy measurements were performed at temperatures close and below the Verwey transition temperature characteristic for pure magnetite (122 and 77 K, respectively). All spectra were fitted with five components and related to nonequivalent Fe 2+ and Fe 3+ sites. The hyperfine parameters of these sites as well as their relative fractions in the powder samples were determined.

TiO2‐Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 ... more TiO2‐Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 nm) were successfully synthesized using a sol‐gel procedure, and were tested for salicylic acid photodegradation under UV irradiation. The structure and morphology of the obtained materials were investigated using X‐ray diffraction, transmission electron microscopy, and N2 adsorption‐ desorption measurements. UV‐Vis spectroscopy was used to study the optical properties. The effects of the gold nanoparticles on the TiO2 crystallization process were twofold, as follows: (i) the number of crystallized zones was strongly related to the concentration of the gold nanoparticles, and (ii) the smaller gold particles increased the time taken for the crystallization of the samples. It was found that the noble metal‐doped samples exhibited higher degradation rates compared with bare titania. It was found that the most active photocatalyst in each studied system was the sample with the highest concen...

Nanomaterials

Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precu... more Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precursor xerogel was characterized by thermal analysis. Bi1−xEuxFeO3 (x = 0–0.20) powders obtained after thermal treatment of the xerogel at 600 °C for 30 min were investigated by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Mössbauer spectroscopy. Magnetic behavior at room temperature was tested using vibrating sample magnetometry. The comparative results showed that europium has a beneficial effect on the stabilization of the perovskite structure and induced a weak ferromagnetism. The particle size decreases after the introduction of Eu3+ from 167 nm for x = 0 to 51 nm for x = 0.20. Photoluminescence spectroscopy showed the enhancement of the characteristic emission peaks intensity with the increase of Eu3+ concentration.

International Journal of Molecular Sciences

The advancement of nanotechnology in the last decade has developed an abundance of novel and intr... more The advancement of nanotechnology in the last decade has developed an abundance of novel and intriguing TiO2-based nanomaterials that are widely used in many sectors, including industry (as a food additive and colorant in cosmetics, paints, plastics, and toothpaste) and biomedicine (photoelectrochemical biosensing, implant coatings, drug delivery, and new emerging antimicrobial agents). Therefore, the increased use of engineered nanomaterials in the industry has raised serious concern about human exposure and their unexpected cytotoxic effects. Since inhalation is considered the most relevant way of absorbing nanomaterials, different cell death mechanisms induced in MRC-5 lung fibroblasts, following the exposure to functionalized TiO2 NPs, were investigated. Long-term exposure to TiO2 nanoparticles co-doped with 1% of iron and nitrogen led to the alteration of p53 protein activity and the gene expression controlled by this suppressor (NF-kB and mdm2), DNA damage, cell cycle disrupti...

Industria Textila

The objective of this study is to investigate the methods to create durable self-cleaning textile... more The objective of this study is to investigate the methods to create durable self-cleaning textiles by coating fabrics with TiO2-(1%)Fe-N-graphene (2%). To improve the adherence of the nanoparticles, the polyester/cotton woven fabrics were pre-treated with polyacrylic acid (PA), carboxymethylcellulose (CMC) and polyethylene polyamine resin (EZF). The pre-treated materials were immersed in a doped TiO2 for 30 minutes at 40oC and dried at 125oC. The finished fabrics were stained with methylene blue dye and exposed to visible light. The SEM images show the presence of particles on polymers layers firmly attached on the material surface. The treatments determine the decrease of the exothermic peak (452.48oC), characteristic of the cellulose decomposition, demonstrating an increase of the thermal conductivity of the materials. The doped TiO2-graphene induces a double degradation of methylene blue in comparison with untreated material and the materials treated with CMC, polyacrylic acid an...

Journal of Physics and Chemistry of Solids

MRS Proceedings

Nanostructured magnetite/T multilayers, with T = Ni, Co, Cr, have been prepared by pulsed laser d... more Nanostructured magnetite/T multilayers, with T = Ni, Co, Cr, have been prepared by pulsed laser deposition. The thickness of individual magnetite and metal layers takes values in the range of 5 - 40 nm with a total multilayer thickness of 100 -120 nm. X-ray diffraction has been used to study the phase characteristics as a function of thermal treatment up to 550 °C. Small amounts of maghemite and hematite were identified together with prevailing magnetite phase after treatments at different temperatures. The mean grain size of magnetite phase increases with temperature from 12 nm at room temperature to 54 nm at 550 °C. The thermal behavior of magnetite in multilayers in comparison with powder magnetite is discussed.

Journal of Alloys and Compounds

Journal of Minerals and Materials Characterization and Engineering

xMoO 2-(1-x)α-Fe 2 O 3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successf... more xMoO 2-(1-x)α-Fe 2 O 3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successfully synthesized by mechanochemical activation of MoO 2 and α-Fe 2 O 3 mixtures for 0-12 hours of ball milling time. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of the molybdenum dioxide-hematite nanoparticle system under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the crystallite size and lattice parameters as function of milling times and indicated the presence of Mo-substituted hematite and Fe-doped molybdenum dioxide at long milling times. The Mössbauer studies yielded the magnetic hyperfine fields and the relative abundance of a quadrupole-split doublet as function of the milling time for all molar concentrations involved. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in a magnetic field of 200 Oe.

Physical chemistry chemical physics : PCCP, Jan 17, 2018

The formation of separate phases in crystalline materials is promoted by doping with elements wit... more The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O3 (x = 0.00, 0.03, 0.04, 0.05) by means of a combination of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy. We found that Fe ions are substituted as Fe3+ at Ti sites and preferentially exhibit pentahedral coordination, whereas Ti ions have coexisting valences of Ti4+/Ti3+. Fe3+ ions are preferentially ordered in clusters, and there exists a transition temperature TC1, below which phase separation occurs between a tetragonal phase T1 free of magnetic clusters and a cubic phase, an...

Superlattices and Microstructures, 2017

Ceramics International, 2016

Materials Research Bulletin, 2017

Materials Characterization, 2010

Rutile-doped hematite xTiO2(1−x)α-Fe2O3 (x=0.0–1.0) nanostructures were synthesized using mechano... more Rutile-doped hematite xTiO2(1−x)α-Fe2O3 (x=0.0–1.0) nanostructures were synthesized using mechanochemical activation by ball milling. Their complex structural, magnetic and thermal properties were characterized by X-ray diffraction, Mössbauer spectroscopy and simultaneous DSC–TGA. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. For the molar concentrations x=0.1 and 0.3, the Mössbauer spectra were fitted

Physica B Condensed Matter, Oct 1, 2008

Cerium-doped hematite particles of the type xCeO2-(1−x)α-Fe2O3 (x=0.1, 0.5) were synthesized usin... more Cerium-doped hematite particles of the type xCeO2-(1−x)α-Fe2O3 (x=0.1, 0.5) were synthesized using mechanochemical activation and characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). XRD patterns yielded the dependence of lattice parameters and particle size as a function of ball milling time for each value of the molar concentration x. For x=0.1, the Mössbauer spectra were fitted