Simona Rada - Academia.edu (original) (raw)
Papers by Simona Rada
This paper proposes the recycling of plates from spent car batteries by the melt quenching method... more This paper proposes the recycling of plates from spent car batteries by the melt quenching method and the incorporation of NiO or Co3O4 contents in order to improve the electrochemical performance of new materials for applications as electrodes on batteries. The analysis of X - ray diffractograms indicates the gradual decrease of the sulfated crystalline phases, respectively 4PbO•PbSO4 and PbO•PbSO4 phases until their disappearance for higher dopant concentrations. IR data show a decreasing trend in the intensity of the bands assigned to sulfate ions and a conversion of [PbO3] pyramidal units into [PbO4] tetrahedral units by doping with high dopant levels yielding to the formation of the PbO2 crystalline phase. The EPR data indicate three resonance lines centered on the gyromagnetic factor, g ~ 2, 2.2 and 8, which are dependent on the NiO level. The first two resonance lines are assigned to nickel ions in higher oxidation states and the last signal centered at g ~ 8 corresponds to nickel metal nanoparticles. This compositional evolution can be explained by considering a process of drastic reduction of nickel ions in oxidation states superior to metallic nickel. The linewidth and the intensity of resonance lines situated at about g ~ 2, 2.17, 4.22 and 7.8 corresponding to the Co+2 ions from EPR spectra depend very strongly on the Co3O4 concentration. The best reversibility of the cyclic voltammograms was highlighted for the samples with x = 8 mol% NiO and 10 mol% Co3O4, which are recommended as suitable in applications as electrode for renewable batteries.
Journal of biological regulators and homeostatic agents, 2021
The research is aiming to obtain at room temperature a new ceramic material containing partially ... more The research is aiming to obtain at room temperature a new ceramic material containing partially stabilized zirconia with different oxides after sintering used for dental and other technological purposes. Our research proposes a new method based on the use of stabilized zirconia with other oxides to obtain optimized dental material with a lower cost price and / or improved properties to allow wider use of these products to an increased number of patients in dental offices. X-ray diffraction, SEM analysis. FTIR spectroscopy, UVVis and density measurements were accomplished for the three ceramic systems. The correlation between the microstructure and the spectroscopic properties of zirconium stabilized by FTIR spectroscopy, UV-Vis helps understanding the mechanisms associated with the formation of high (tetragonal and / or cubic) temperature zirconia. Along with the simple, less costly preparation method and high purity of the ceramic products our study offers a highly desirable produ...
Radiation Physics and Chemistry, 2020
In this study, the structural and spectroscopic properties of a serie samarium doped lead oxide-b... more In this study, the structural and spectroscopic properties of a serie samarium doped lead oxide-borate glasses and vitroceramics in the xSm 2 O 3 •(100-x)[4B 2 O 3 •PbO] composition where x = 0, 10, 20, 40 mol % Sm 2 O 3 were reported. The samples were prepared by the conventional melt-quenching method and were characterized by the analysis of X-Ray diffraction and the investigations of Raman, FTIR, UV-Vis, PL, EPR and XAS spectroscopies. The XRD patterns reveal amorphous nature of the samples with lower Sm 2 O 3 content up to x = 20 mol%. For the sample with x = 40 mol% Sm 2 O 3 , the analysis of XRD data indicates the presence of two Sm(BO 2) 3 crystalline phases with monoclinic structure and PbO crystalline phase with orthorhombic and tetragonal structure. FTIR and Raman spectra indicate that the evolution of [BO 3 ] and [BO 4 ] structural units were modified by increasing of Sm 2 O 3 content up to 40 mol % in the host matrix. UV-Vis data show: i) the stronger transitions due to the presence of Pb]O bonds from [PbO 3 ] structural units, for samples with lower Sm 2 O 3 content; ii) the conversion of the [PbO 3 ] structural units in [PbO 4 ] structural units for the sample with higher Sm 2 O 3 content (x = 40 mol %). The optical band gap values are between 4.03 and 4.32 eV for the direct transitions and between 3.94 and 4.15 eV for the indirect transitions. PL data show the emission bands corresponding to the f-f electronic transitions of Sm 3+ ions. The intensity of the emission increases as the concentration of the Sm +3 ions increases up to 10 mol% and after this it decreases. This decrease in PL intensity is due to the energy transfer from excited Sm +3 ions into non-excited Sm +3 ions or cross relaxations because the distance between samarium ions were decreased by the doping after 10 mol % Sm 2 O 3 and the exchange and inter-ionic interactions were also enhanced. The analysis of EPR data shows two broad signals centered at g~9.7 and g~2.11, which can be due to the isolated Sm 3+ ions and Sm 3+-Sm 3+ pair centers. A detailed study of XANEX and EXAFS data was used to evaluate the environment of the lead atoms, coordination number and interatomic Pb-O distance in the studied glasses and vitroceramics. In the glasses can be estimated the presence a greater number of longer Pb-O distances while in vitroceramic exists smaller Pb-O distances and a better packing arrangement.
Materials
To date, the scientific research in the field of recycling of construction and demolition wastes ... more To date, the scientific research in the field of recycling of construction and demolition wastes was focused on the production of concrete, cements, and bricks. The attainment of these products was limited to the addition of suitable binder contents, such as lime or cement, compaction, and possibly heat treatment, without a concrete recycling method. In this paper, new cement materials consisting of 2.5 weight% composite and originating from construction and demolition waste powder, were prepared and investigated in view of applications in the construction industry as a substituent of cement. The materials with recycled powder from construction and demolition wastes were characterized by X-ray diffraction (XRD), infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The XRD data indicate vitroceramic structures with varied crystalline phases. The NMR relaxometry data show four reservoirs of water associated with bounded water and with three types of pores in the composite ...
Journal of The Electrochemical Society, 2019
Ceramics International, 2014
New xSb 2 O 3 •(100 Àx)[4PbO 2 •Pb] antimony-lead oxide glasses and vitroceramics with x ¼ 0-20 m... more New xSb 2 O 3 •(100 Àx)[4PbO 2 •Pb] antimony-lead oxide glasses and vitroceramics with x ¼ 0-20 mol% Sb 2 O 3 were prepared by meltquenching method. Structural and behavioral investigation of samples was performed by XRD, FTIR and UV-vis spectroscopies and cyclic voltammetry measurements. Effects induced by increasing the Sb 2 O 3 content of samples on their structure, optical and electrochemical properties are discussed. XRD data reveal that for samples with x Z 15 mol% Sb 2 O 3 vitroceramics were obtained. The crystalline phase was identified as the β-Sb 2 O 4 built up of [Sb V O 6 ] and [Sb III O 4 E] structural units. In agreement with the XRD data, FTIR spectroscopy investigation shows that increasing the Sb 2 O 3 content of the antimony-lead glasses produces structural modifications of the host matrix. UV-vis data show that the Sb 2 O 3 content of the samples and the valence state of antimony plays a significant role in improving the gap energy. Thus, the incorporation of Sb 2 O 3 up to 15 mol% decreases abruptly the gap energy due to the tendency of Sb þ 3 ions to be oxidized to Sb þ 5 ions. This process increases the amount of carriers in the host network. Cyclic voltammograms of antimony-lead glasses exhibit a good reversibility and show an improved electrochemical performance in comparison with that of lead glasses. The antimony-lead glasses are potential candidates as electrodes for rechargeable batteries.
Journal of Non-Crystalline Solids, 2016
Lithium-lead-germanate glasses in the xLi 2 O•(100-x)[7GeO 2 •3PbO] system, where 0 ≤ x ≤ 40 mol%... more Lithium-lead-germanate glasses in the xLi 2 O•(100-x)[7GeO 2 •3PbO] system, where 0 ≤ x ≤ 40 mol% Li 2 CO 3 exhibit a "germanate anomaly", which is a maximum in their density profiles with the addition of Li 2 CO 3 up to 20 mol%. The structural characterization of the samples was performed by investigations of Raman spectroscopy and X-ray scattering analysis. An EXAFS analysis of the spectra collected at the germanium K-edge for series of lithium-lead-germanate glasses is also presented. With the EXAFS-extracted structural parameters were reconstructed to the local neighborhood of Ge atoms and were verified current opinions on the germanate anomaly in the considered glasses. The formation of higher-coordinated Ge species in the glassy network can be correlated with the density anomaly. Several structural mechanisms can be summarized by increasing of lithium carbonate in the lead-germanate glassy: i) depolymerization of germanate network; ii) conversion of 3-to 4-membered [GeO 4 ] rings; iii) transformation of connected [GeO 6 ] structural units into isolated [GeO 6 ] structural units and a conversion part of higher to lower coordination number of germanium atoms.
Journal of Synchrotron Radiation, 2020
Zirconate systems having the composition 3HfO2·15SiO2·xY2O3·(82 − x)ZrO2, where x = 2, 7 and 12 m... more Zirconate systems having the composition 3HfO2·15SiO2·xY2O3·(82 − x)ZrO2, where x = 2, 7 and 12 mol% Y2O3, were synthesized by a sol-gel method. The analysis of X-ray diffraction data showed the presence of the t-ZrO2, m-ZrO2, m-HfO2, Y2SiO5 and Y2Si2O7 crystalline phases in a ceramic nanomixture. Spectroscopic data show that the increase of the Y2O3 content of samples determines the increase of the t-ZrO2, m-HfO2 and silicate crystalline phases. Gap energy values decrease almost linearly with increasing Y2O3 content of samples. A detailed study of XANES data does not show a significant difference with increasing Y2O3 content of the samples suggesting an appreciable stability of the hafnium ions +4 oxidation state and their microvicinity. EXAFS results show that the local structure around the Hf cation is similar to that from the monoclinic crystalline HfO2 where the Hf–O coordination number tends to 7. The bond lengths of Hf–O shells show small deviations from ∼2.12 Å and the Hf–me...
Journal of Materials Science, 2009
Abstract The structural properties of some tellurite glasses were investigated by FT-IR spectrosc... more Abstract The structural properties of some tellurite glasses were investigated by FT-IR spectroscopy, density measurements, and quantum chemical calculations. Main results reveal that the ratio TeO 4/TeO 3 is found to decrease in the order V 2 O 5> B 2 O 3> P 2 O ...
Solid State Ionics, Aug 26, 2010
Materials Research Bulletin, 2010
This paper describes photosensitive properties and spectroscopic studies on the xPbO(100−x)[6TeO2... more This paper describes photosensitive properties and spectroscopic studies on the xPbO(100−x)[6TeO2·4V2O5] (where x=0–100mol%) glass system. Our FTIR, UV–vis spectroscopic data and density measurements exhibit compositional dependent trends and the existence of characteristic vanadate (orthovanadate, pyrovanadate) structural units in these glasses. By laser exposures of the samples, variations observed in the FTIR and UV–vis spectra show that the existence a redox
Journal of Non-Crystalline Solids, 2011
Journal of Materials Science, 2008
... 1. Gaman VI, Peznikov VA, Fedyainova NI, Vyssh UZV (1972) Zaved Fiz 2:57 2. Sidkey MA, El Mal... more ... 1. Gaman VI, Peznikov VA, Fedyainova NI, Vyssh UZV (1972) Zaved Fiz 2:57 2. Sidkey MA, El Mallawany R, Nakhla RI, Abd El-Moneim A (1997) J Non-Cryst Solids 215:75 3. Chowdari BVR, Tan KL, Ling F (2000 ... Khattak GD, Tabet N, Wenger LE (2005) Phys Rev B 72:104203. ...
Journal of Materials Science, 2008
Journal of Materials Science, 2008
ABSTRACT FTIR spectroscopy measurements were performed on the xGd2O 3-(100-x)[2Bi2O3·B2O 3] syste... more ABSTRACT FTIR spectroscopy measurements were performed on the xGd2O 3-(100-x)[2Bi2O3·B2O 3] system with 0 ≤. × ≤. 25 mol% in order to point out the effect of Gd2O3 addition in the bismuth-borate glass matrix on the local order of this system. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses. These data show that the glass structure consists on the BiO6, BO 3 and BO4 structural units, and the conversion among these units mainly depends on the Gd2O3 content.
Journal of Molecular Modeling, 2010
This paper proposes the recycling of plates from spent car batteries by the melt quenching method... more This paper proposes the recycling of plates from spent car batteries by the melt quenching method and the incorporation of NiO or Co3O4 contents in order to improve the electrochemical performance of new materials for applications as electrodes on batteries. The analysis of X - ray diffractograms indicates the gradual decrease of the sulfated crystalline phases, respectively 4PbO•PbSO4 and PbO•PbSO4 phases until their disappearance for higher dopant concentrations. IR data show a decreasing trend in the intensity of the bands assigned to sulfate ions and a conversion of [PbO3] pyramidal units into [PbO4] tetrahedral units by doping with high dopant levels yielding to the formation of the PbO2 crystalline phase. The EPR data indicate three resonance lines centered on the gyromagnetic factor, g ~ 2, 2.2 and 8, which are dependent on the NiO level. The first two resonance lines are assigned to nickel ions in higher oxidation states and the last signal centered at g ~ 8 corresponds to nickel metal nanoparticles. This compositional evolution can be explained by considering a process of drastic reduction of nickel ions in oxidation states superior to metallic nickel. The linewidth and the intensity of resonance lines situated at about g ~ 2, 2.17, 4.22 and 7.8 corresponding to the Co+2 ions from EPR spectra depend very strongly on the Co3O4 concentration. The best reversibility of the cyclic voltammograms was highlighted for the samples with x = 8 mol% NiO and 10 mol% Co3O4, which are recommended as suitable in applications as electrode for renewable batteries.
Journal of biological regulators and homeostatic agents, 2021
The research is aiming to obtain at room temperature a new ceramic material containing partially ... more The research is aiming to obtain at room temperature a new ceramic material containing partially stabilized zirconia with different oxides after sintering used for dental and other technological purposes. Our research proposes a new method based on the use of stabilized zirconia with other oxides to obtain optimized dental material with a lower cost price and / or improved properties to allow wider use of these products to an increased number of patients in dental offices. X-ray diffraction, SEM analysis. FTIR spectroscopy, UVVis and density measurements were accomplished for the three ceramic systems. The correlation between the microstructure and the spectroscopic properties of zirconium stabilized by FTIR spectroscopy, UV-Vis helps understanding the mechanisms associated with the formation of high (tetragonal and / or cubic) temperature zirconia. Along with the simple, less costly preparation method and high purity of the ceramic products our study offers a highly desirable produ...
Radiation Physics and Chemistry, 2020
In this study, the structural and spectroscopic properties of a serie samarium doped lead oxide-b... more In this study, the structural and spectroscopic properties of a serie samarium doped lead oxide-borate glasses and vitroceramics in the xSm 2 O 3 •(100-x)[4B 2 O 3 •PbO] composition where x = 0, 10, 20, 40 mol % Sm 2 O 3 were reported. The samples were prepared by the conventional melt-quenching method and were characterized by the analysis of X-Ray diffraction and the investigations of Raman, FTIR, UV-Vis, PL, EPR and XAS spectroscopies. The XRD patterns reveal amorphous nature of the samples with lower Sm 2 O 3 content up to x = 20 mol%. For the sample with x = 40 mol% Sm 2 O 3 , the analysis of XRD data indicates the presence of two Sm(BO 2) 3 crystalline phases with monoclinic structure and PbO crystalline phase with orthorhombic and tetragonal structure. FTIR and Raman spectra indicate that the evolution of [BO 3 ] and [BO 4 ] structural units were modified by increasing of Sm 2 O 3 content up to 40 mol % in the host matrix. UV-Vis data show: i) the stronger transitions due to the presence of Pb]O bonds from [PbO 3 ] structural units, for samples with lower Sm 2 O 3 content; ii) the conversion of the [PbO 3 ] structural units in [PbO 4 ] structural units for the sample with higher Sm 2 O 3 content (x = 40 mol %). The optical band gap values are between 4.03 and 4.32 eV for the direct transitions and between 3.94 and 4.15 eV for the indirect transitions. PL data show the emission bands corresponding to the f-f electronic transitions of Sm 3+ ions. The intensity of the emission increases as the concentration of the Sm +3 ions increases up to 10 mol% and after this it decreases. This decrease in PL intensity is due to the energy transfer from excited Sm +3 ions into non-excited Sm +3 ions or cross relaxations because the distance between samarium ions were decreased by the doping after 10 mol % Sm 2 O 3 and the exchange and inter-ionic interactions were also enhanced. The analysis of EPR data shows two broad signals centered at g~9.7 and g~2.11, which can be due to the isolated Sm 3+ ions and Sm 3+-Sm 3+ pair centers. A detailed study of XANEX and EXAFS data was used to evaluate the environment of the lead atoms, coordination number and interatomic Pb-O distance in the studied glasses and vitroceramics. In the glasses can be estimated the presence a greater number of longer Pb-O distances while in vitroceramic exists smaller Pb-O distances and a better packing arrangement.
Materials
To date, the scientific research in the field of recycling of construction and demolition wastes ... more To date, the scientific research in the field of recycling of construction and demolition wastes was focused on the production of concrete, cements, and bricks. The attainment of these products was limited to the addition of suitable binder contents, such as lime or cement, compaction, and possibly heat treatment, without a concrete recycling method. In this paper, new cement materials consisting of 2.5 weight% composite and originating from construction and demolition waste powder, were prepared and investigated in view of applications in the construction industry as a substituent of cement. The materials with recycled powder from construction and demolition wastes were characterized by X-ray diffraction (XRD), infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The XRD data indicate vitroceramic structures with varied crystalline phases. The NMR relaxometry data show four reservoirs of water associated with bounded water and with three types of pores in the composite ...
Journal of The Electrochemical Society, 2019
Ceramics International, 2014
New xSb 2 O 3 •(100 Àx)[4PbO 2 •Pb] antimony-lead oxide glasses and vitroceramics with x ¼ 0-20 m... more New xSb 2 O 3 •(100 Àx)[4PbO 2 •Pb] antimony-lead oxide glasses and vitroceramics with x ¼ 0-20 mol% Sb 2 O 3 were prepared by meltquenching method. Structural and behavioral investigation of samples was performed by XRD, FTIR and UV-vis spectroscopies and cyclic voltammetry measurements. Effects induced by increasing the Sb 2 O 3 content of samples on their structure, optical and electrochemical properties are discussed. XRD data reveal that for samples with x Z 15 mol% Sb 2 O 3 vitroceramics were obtained. The crystalline phase was identified as the β-Sb 2 O 4 built up of [Sb V O 6 ] and [Sb III O 4 E] structural units. In agreement with the XRD data, FTIR spectroscopy investigation shows that increasing the Sb 2 O 3 content of the antimony-lead glasses produces structural modifications of the host matrix. UV-vis data show that the Sb 2 O 3 content of the samples and the valence state of antimony plays a significant role in improving the gap energy. Thus, the incorporation of Sb 2 O 3 up to 15 mol% decreases abruptly the gap energy due to the tendency of Sb þ 3 ions to be oxidized to Sb þ 5 ions. This process increases the amount of carriers in the host network. Cyclic voltammograms of antimony-lead glasses exhibit a good reversibility and show an improved electrochemical performance in comparison with that of lead glasses. The antimony-lead glasses are potential candidates as electrodes for rechargeable batteries.
Journal of Non-Crystalline Solids, 2016
Lithium-lead-germanate glasses in the xLi 2 O•(100-x)[7GeO 2 •3PbO] system, where 0 ≤ x ≤ 40 mol%... more Lithium-lead-germanate glasses in the xLi 2 O•(100-x)[7GeO 2 •3PbO] system, where 0 ≤ x ≤ 40 mol% Li 2 CO 3 exhibit a "germanate anomaly", which is a maximum in their density profiles with the addition of Li 2 CO 3 up to 20 mol%. The structural characterization of the samples was performed by investigations of Raman spectroscopy and X-ray scattering analysis. An EXAFS analysis of the spectra collected at the germanium K-edge for series of lithium-lead-germanate glasses is also presented. With the EXAFS-extracted structural parameters were reconstructed to the local neighborhood of Ge atoms and were verified current opinions on the germanate anomaly in the considered glasses. The formation of higher-coordinated Ge species in the glassy network can be correlated with the density anomaly. Several structural mechanisms can be summarized by increasing of lithium carbonate in the lead-germanate glassy: i) depolymerization of germanate network; ii) conversion of 3-to 4-membered [GeO 4 ] rings; iii) transformation of connected [GeO 6 ] structural units into isolated [GeO 6 ] structural units and a conversion part of higher to lower coordination number of germanium atoms.
Journal of Synchrotron Radiation, 2020
Zirconate systems having the composition 3HfO2·15SiO2·xY2O3·(82 − x)ZrO2, where x = 2, 7 and 12 m... more Zirconate systems having the composition 3HfO2·15SiO2·xY2O3·(82 − x)ZrO2, where x = 2, 7 and 12 mol% Y2O3, were synthesized by a sol-gel method. The analysis of X-ray diffraction data showed the presence of the t-ZrO2, m-ZrO2, m-HfO2, Y2SiO5 and Y2Si2O7 crystalline phases in a ceramic nanomixture. Spectroscopic data show that the increase of the Y2O3 content of samples determines the increase of the t-ZrO2, m-HfO2 and silicate crystalline phases. Gap energy values decrease almost linearly with increasing Y2O3 content of samples. A detailed study of XANES data does not show a significant difference with increasing Y2O3 content of the samples suggesting an appreciable stability of the hafnium ions +4 oxidation state and their microvicinity. EXAFS results show that the local structure around the Hf cation is similar to that from the monoclinic crystalline HfO2 where the Hf–O coordination number tends to 7. The bond lengths of Hf–O shells show small deviations from ∼2.12 Å and the Hf–me...
Journal of Materials Science, 2009
Abstract The structural properties of some tellurite glasses were investigated by FT-IR spectrosc... more Abstract The structural properties of some tellurite glasses were investigated by FT-IR spectroscopy, density measurements, and quantum chemical calculations. Main results reveal that the ratio TeO 4/TeO 3 is found to decrease in the order V 2 O 5> B 2 O 3> P 2 O ...
Solid State Ionics, Aug 26, 2010
Materials Research Bulletin, 2010
This paper describes photosensitive properties and spectroscopic studies on the xPbO(100−x)[6TeO2... more This paper describes photosensitive properties and spectroscopic studies on the xPbO(100−x)[6TeO2·4V2O5] (where x=0–100mol%) glass system. Our FTIR, UV–vis spectroscopic data and density measurements exhibit compositional dependent trends and the existence of characteristic vanadate (orthovanadate, pyrovanadate) structural units in these glasses. By laser exposures of the samples, variations observed in the FTIR and UV–vis spectra show that the existence a redox
Journal of Non-Crystalline Solids, 2011
Journal of Materials Science, 2008
... 1. Gaman VI, Peznikov VA, Fedyainova NI, Vyssh UZV (1972) Zaved Fiz 2:57 2. Sidkey MA, El Mal... more ... 1. Gaman VI, Peznikov VA, Fedyainova NI, Vyssh UZV (1972) Zaved Fiz 2:57 2. Sidkey MA, El Mallawany R, Nakhla RI, Abd El-Moneim A (1997) J Non-Cryst Solids 215:75 3. Chowdari BVR, Tan KL, Ling F (2000 ... Khattak GD, Tabet N, Wenger LE (2005) Phys Rev B 72:104203. ...
Journal of Materials Science, 2008
Journal of Materials Science, 2008
ABSTRACT FTIR spectroscopy measurements were performed on the xGd2O 3-(100-x)[2Bi2O3·B2O 3] syste... more ABSTRACT FTIR spectroscopy measurements were performed on the xGd2O 3-(100-x)[2Bi2O3·B2O 3] system with 0 ≤. × ≤. 25 mol% in order to point out the effect of Gd2O3 addition in the bismuth-borate glass matrix on the local order of this system. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses. These data show that the glass structure consists on the BiO6, BO 3 and BO4 structural units, and the conversion among these units mainly depends on the Gd2O3 content.
Journal of Molecular Modeling, 2010