In the search for environmentally friendly materials with a wide range of properties, polymer com... more In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe3O4, and a mixture of BaTiO3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films’ structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe3O4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness,... more Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl2O4 was produced by solid-state reaction between MgO and a-Al2O3 powders. Mechanical activation was used to increase the reactivity of powders and decrease the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 30, 60, 90, and 120 minutes. The resulting powders were characterized to determine the effect of activation on surface area, particle size, and crystallinity. Mechanical activation decreased particle size, increased surface area, and increased the width of peaks in x-ray diffraction. Dilatometry was used to monitor densification behavior up to 1500 oC. For non-activated powders, sintering started at approximately 1400 oC, while for activated powders, the onset temperature decreased to about 1340 oC. Mechanical activation is an efficient method to im...
This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized mu... more This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized multi-walled carbon nanotubes (o-MWCNTs). One method included the presence of activating agents to promote covalent bonding and the other the adsorption on o-MWCNTs to elucidate if non-specific bonding on the o-MWCNTs surface exists. The influence of the immobilization time and initial enzyme concentration on protein loading and the expressed lypolitic activity of the immobilized preparation were investigated. The results showed that the enzyme adsorbs on o-MWCNTs in a maximal amount of 37 mg mg À1 CNTs, while the attached amount was more than 2-times higher under covalent promoting conditions (80 mg mg À1 CNTs). Furthermore, similar trends were observed for the lypolitic activity, whereby preparations obtained under covalent promoting conditions had almost 3-times higher activity (560 IU g À1 of immobilized enzyme). In addition, immobilization of the enzyme was confirmed by Fourier transformation infrared spectroscopy and thermogravimetric analysis.
Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic aci... more Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni2(en)2(H2O)6(pyr)]·4H2O, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser–Suzuki function. The obtained individual steps were described by Johnson–Mehl–Avrami A2 model and Šesták–Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products.
Recently, it has been discovered that dilithium terephthalate (Li2tpht) shows enhanced thermal st... more Recently, it has been discovered that dilithium terephthalate (Li2tpht) shows enhanced thermal stability over conventional anode materials for Li-ion batteries [1]. This investigation compares two ways of synthesis of the mentioned compound. The first one was described by Kaduk [2] and the other approach presents a new procedure. According to Kaduk, Li2tpht is obtained by precipitation from an aqueous suspension containing Li2O and terephthalic acid (H2tpht) in a molar ratio 1:1. The new method is based on a simple grinding of Li2CO3 and H2tpht in an agate mortar. Both samples were characterized by FTIR spectroscopy, TG/DSC and XRD analysis. The obtained results are compared and discussed.
Acta Crystallographica Section C Crystal Structure Communications, 2002
The title complexes, catena-poly [[aqua(1,10- , take the form of zigzag chains, with the 1,4-benz... more The title complexes, catena-poly [[aqua(1,10- , take the form of zigzag chains, with the 1,4-benzenedicarboxylate ion acting as an amphimonodentate ligand in (I) and a bis-bidentate ligand in (II). The Co II ion in (I) is ®vecoordinate and has a distorted trigonal±bipyramidal geometry. The Cu II ion in (II) is in a very distorted octahedral 4+2 environment, with the octahedron elongated along the trans OÐCuÐO bonds and with a trans OÐCuÐO angle of only 137.22 (8) .
Epoxy/clay nanocomposites (NC) have become a very interesting topic among researchers in the past... more Epoxy/clay nanocomposites (NC) have become a very interesting topic among researchers in the past two decades because nanoclays have a positive effect on the mechanical, thermal and especially barrier and anticorrosive performances of the polymers. In this study epoxy NCs and NC-based epoxy coatings were prepared by the solution intercalation method using Cloisite 30B as nanoclay. WAXD and SEM analyses revealed that a mainly exfoliated structure was obtained in epoxy NC with 1 wt% clay content, while higher clay loadings reduced the number of exfoliated clay nanolayers and produced a mainly intercalated structure. EIS, TGA and DMA analyses showed that epoxy NCs with clay content below 5 wt% exhibited increased corrosion stability, thermal stability, glass transition temperature (T g ) and storage modulus (G ), in both glassy and rubbery states due to the nanoscale dispersion of Cloisite 30B and the barrier effect of individual nanolayers. Enhanced mechanical properties were also noticed at higher clay loadings, but the rate of improvement was lower. The highest extent of exfoliation and the most homogeneous macromolecular network was found for NC with 1 wt% of clay, leading to the highest improvement of thermal and anticorrosive properties. The salt spray test results showed that anticorrosive properties of epoxy coatings in the presence of 3 wt% and especially 1 wt% of Cloisite 30B were significantly better, thus indicating that nanoclay efficiently modifies the commercial epoxy coatings.
ABSTRACT The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was inves... more ABSTRACT The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn 2+ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transi-tion from dendritic and spongy to smooth, bright, and amor-phous structure of Zn–Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hy-droxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to de-crease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.
ABSTRACT In this work, a combined experimental and theoretical study on the structures of methoxy... more ABSTRACT In this work, a combined experimental and theoretical study on the structures of methoxy substituted 5-phenylazo-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones has been reported. The dyes under the investigation have been thoroughly characterized. X-ray single-crystal analysis shows that 5-(4-methoxyphenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridone crystallizes in the hydrazone form. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of the investigated dyes have been performed using density functional theory. The optimized geometrical parameters obtained by density functional theory calculations are in good conformity with the single-crystal data. The fundamental vibrational wavenumbers, as well as their intensities have been calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Vibrational, nuclear magnetic resonance and natural bond orbital analysis confirm that the prepared dyes exist in the hydrazone tautomeric form in the solid state and dimethyl sulfoxide solution.
In the search for environmentally friendly materials with a wide range of properties, polymer com... more In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe3O4, and a mixture of BaTiO3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films’ structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe3O4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness,... more Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl2O4 was produced by solid-state reaction between MgO and a-Al2O3 powders. Mechanical activation was used to increase the reactivity of powders and decrease the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 30, 60, 90, and 120 minutes. The resulting powders were characterized to determine the effect of activation on surface area, particle size, and crystallinity. Mechanical activation decreased particle size, increased surface area, and increased the width of peaks in x-ray diffraction. Dilatometry was used to monitor densification behavior up to 1500 oC. For non-activated powders, sintering started at approximately 1400 oC, while for activated powders, the onset temperature decreased to about 1340 oC. Mechanical activation is an efficient method to im...
This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized mu... more This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized multi-walled carbon nanotubes (o-MWCNTs). One method included the presence of activating agents to promote covalent bonding and the other the adsorption on o-MWCNTs to elucidate if non-specific bonding on the o-MWCNTs surface exists. The influence of the immobilization time and initial enzyme concentration on protein loading and the expressed lypolitic activity of the immobilized preparation were investigated. The results showed that the enzyme adsorbs on o-MWCNTs in a maximal amount of 37 mg mg À1 CNTs, while the attached amount was more than 2-times higher under covalent promoting conditions (80 mg mg À1 CNTs). Furthermore, similar trends were observed for the lypolitic activity, whereby preparations obtained under covalent promoting conditions had almost 3-times higher activity (560 IU g À1 of immobilized enzyme). In addition, immobilization of the enzyme was confirmed by Fourier transformation infrared spectroscopy and thermogravimetric analysis.
Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic aci... more Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni2(en)2(H2O)6(pyr)]·4H2O, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser–Suzuki function. The obtained individual steps were described by Johnson–Mehl–Avrami A2 model and Šesták–Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products.
Recently, it has been discovered that dilithium terephthalate (Li2tpht) shows enhanced thermal st... more Recently, it has been discovered that dilithium terephthalate (Li2tpht) shows enhanced thermal stability over conventional anode materials for Li-ion batteries [1]. This investigation compares two ways of synthesis of the mentioned compound. The first one was described by Kaduk [2] and the other approach presents a new procedure. According to Kaduk, Li2tpht is obtained by precipitation from an aqueous suspension containing Li2O and terephthalic acid (H2tpht) in a molar ratio 1:1. The new method is based on a simple grinding of Li2CO3 and H2tpht in an agate mortar. Both samples were characterized by FTIR spectroscopy, TG/DSC and XRD analysis. The obtained results are compared and discussed.
Acta Crystallographica Section C Crystal Structure Communications, 2002
The title complexes, catena-poly [[aqua(1,10- , take the form of zigzag chains, with the 1,4-benz... more The title complexes, catena-poly [[aqua(1,10- , take the form of zigzag chains, with the 1,4-benzenedicarboxylate ion acting as an amphimonodentate ligand in (I) and a bis-bidentate ligand in (II). The Co II ion in (I) is ®vecoordinate and has a distorted trigonal±bipyramidal geometry. The Cu II ion in (II) is in a very distorted octahedral 4+2 environment, with the octahedron elongated along the trans OÐCuÐO bonds and with a trans OÐCuÐO angle of only 137.22 (8) .
Epoxy/clay nanocomposites (NC) have become a very interesting topic among researchers in the past... more Epoxy/clay nanocomposites (NC) have become a very interesting topic among researchers in the past two decades because nanoclays have a positive effect on the mechanical, thermal and especially barrier and anticorrosive performances of the polymers. In this study epoxy NCs and NC-based epoxy coatings were prepared by the solution intercalation method using Cloisite 30B as nanoclay. WAXD and SEM analyses revealed that a mainly exfoliated structure was obtained in epoxy NC with 1 wt% clay content, while higher clay loadings reduced the number of exfoliated clay nanolayers and produced a mainly intercalated structure. EIS, TGA and DMA analyses showed that epoxy NCs with clay content below 5 wt% exhibited increased corrosion stability, thermal stability, glass transition temperature (T g ) and storage modulus (G ), in both glassy and rubbery states due to the nanoscale dispersion of Cloisite 30B and the barrier effect of individual nanolayers. Enhanced mechanical properties were also noticed at higher clay loadings, but the rate of improvement was lower. The highest extent of exfoliation and the most homogeneous macromolecular network was found for NC with 1 wt% of clay, leading to the highest improvement of thermal and anticorrosive properties. The salt spray test results showed that anticorrosive properties of epoxy coatings in the presence of 3 wt% and especially 1 wt% of Cloisite 30B were significantly better, thus indicating that nanoclay efficiently modifies the commercial epoxy coatings.
ABSTRACT The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was inves... more ABSTRACT The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn 2+ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transi-tion from dendritic and spongy to smooth, bright, and amor-phous structure of Zn–Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hy-droxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to de-crease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.
ABSTRACT In this work, a combined experimental and theoretical study on the structures of methoxy... more ABSTRACT In this work, a combined experimental and theoretical study on the structures of methoxy substituted 5-phenylazo-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones has been reported. The dyes under the investigation have been thoroughly characterized. X-ray single-crystal analysis shows that 5-(4-methoxyphenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridone crystallizes in the hydrazone form. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of the investigated dyes have been performed using density functional theory. The optimized geometrical parameters obtained by density functional theory calculations are in good conformity with the single-crystal data. The fundamental vibrational wavenumbers, as well as their intensities have been calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Vibrational, nuclear magnetic resonance and natural bond orbital analysis confirm that the prepared dyes exist in the hydrazone tautomeric form in the solid state and dimethyl sulfoxide solution.
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Papers by Jelena Rogan