DSC-TG-MS study of hydroxyapatite nanopowders

Hydroxyapatite nanopowders have been widely studied for biomedical application due to excellent biocompatibility. It attaches chemically to bone tissue providing fixation of artificial implant materials. Main research objectives during last few decades is to obtain hydroxyapatite based material which can withstand mechanical loadings generated in physiological conditions. One of the possible pathway is fabrication of dense nanostructured hydroxyapatite through approprate sintering process, which is strongly correlated with thermal behaviour of starting nanopowders. In this study, extensive analyses of thermal behaviour of three hydroxyapatite nanopowders prepared with different methods will be presented. Differential Scanning Calorimetry (DSC), Thermo-Gravimetry (TG) with simultaneous Mass Spectrometry (MS) studies have been performed. The obtained results are discussed in the sense of energy-related events, mass loss and water and carbon dioxide molecules evolution to give better understanding of their thermal\ud behaviour

Theoretical and Experimental Study of (Ba,Sr)TiO 3 Perovskite Solid Solutions and BaTiO 3 /SrTiO 3 Heterostructures

This study was supported by the ERA-NET HarvEnPiez project. The authors would like to thank their national funding agencies (Latvian State Education Development Agency, Slovenian Ministry of Higher Education, Science and Technology, Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III – M-ERA NET Program).The results of experimental and theoretical ab initio study of structural and piezoelectric properties of (Ba,Sr)TiO3 perovskite solid solutions are discussed and compared. Experimentally, plate-like (Ba,Sr)TiO3 particles were synthesized by the topochemical conversion in the molten salt from Bi4Ti3O12 template plates. All dimensions (side length ≈ 1 µm, thickness ≈ 200–400 nm) were well above the critical size necessary for observation of piezo- and ferroelectricity. The first-principles computations of the structural and electromechanical properties of solid solutions were performed with CRYSTAL14 computer code within the linear combination of atomic orbitals (LCAO) approximation, using three advanced hybrid functionals of the density-functional-theory (DFT). Different chemical compositions are considered for the ferroelectric and paraelectric phases. Calculated structural properties of solid solutions in tetragonal and cubic phases are in a very good agreement with experimental data. Experimentally obtained and calculated band gaps are compared for cubic SrTiO3 and tetragonal BaTiO3. BaTiO3/SrTiO3 heterostructures were considered theoretically for different chemical compositions. The calculated piezoelectric properties of solid solutions and heterostructures in ferroelectric phase are compared. It is predicted that both solid solutions and heterostructures improve the piezoelectric properties of the bulk BaTiO3, but solid solutions are more preferable for equal Sr concentrations.ERA-NET HarvEnPiez project; Latvian State Education Development Agency, Slovenian Ministry of Higher Education, Science and Technology, Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III – M-ERA NET Program; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

The influence of heteroatoms on physicochemical properties of cobalt ferrite nanoparticles

In the last two decades, cobalt ferrite (CoFe2O4, CFO) has attracted extensive attention due to its applicability in data storage, catalysis, energy, environment, and in particular, biomedicine. To further extend applicability and improve understanding of fundamental processes, the present work investigates the influence of heteroatoms on physicochemical properties of CFO. Solvothermal method was used for designing a non-agglomerated particles with uniform morpho-structural properties. The physicochemical properties of Zn2+ and Ga3+ substituted CFO nanoparticles were examined (Co(1-x)ZnxFe2O4 and CoGaxFe(2-x)O4; x=0, 0.1, 0.3 and 0.5). The X-ray diffraction (XRD) measurements confirmed the presence of pure cubic spinel phase in all samples, while the transmission electron microscopy (TEM) showed sphere-like nanoparticles with a mean diameter of 6±1 nm. The amount of adsorbed oleic acid on the surface of the nanoparticles, determined by thermogravimetric (TG) analysis indicates the formation of a complete monolayer of surfactant. The FT-IR analysis substantiated the presence of oleic acid on the surface of the nanoparticles and discovered its covalent bonding to the metal atoms. Substitution of host-atoms was also confirmed by Raman spectroscopy. Magnetic measurements revealed the influence of heteroatoms on saturation magnetization and magnetic anisotropy, showing for all the samples superparamagnetic behaviour at room temperature. The substitution of Co2+ and Fe3+ ions with Zn2+ and Ga3+, respectively, leads to the change in chemical composition and cationic distribution of CFO and consequently to variation of its magnetic properties.Twenty-second Annual Conference YUCOMAT : August 30 - September 3, Herceg Novi, 202

Morphology Control of PbZrxTi1-xO3 Crystallites under Alkaline Hydrothermal Conditions

Outstanding ferroelectric and piezoelectric properties of PbZrxTi1-xO3 (PZT) make nano and sub-micrometer particles of this material interesting for future nanotechnological applications as well as for fundamental studies of ferroelectricity at the nanoscale. In the present work, the prospects of a new hydrothermal approach were explored to control the particle size, aggregation stage, and composition of the PZT with the target composition of Zr/Ti = 60/40 (x = 0.6). Starting with water-soluble Zr-, Ti-, and Pb-precursors, the PZT formation was examined in the broad base (KOH) concentration range. The PZT particle size and composition were governed by the ratio of KOH with respect to Pb and not by the absolute KOH concentration (cKOH). The incorporation of Zr into the PZT perovskite phase began to decline at KOH:Pb ≤ 1.7 and at KOH:Pb > 20. In the concentration range of 20 ≥ KOH:Pb > 1.5, the PZT particles adopted a cube-like shape, the size of which decreased with a decrease in the KOH:Pb ratio. The smallest (<200 nm) and well-separated PZT particles were obtained at KOH:Pb = 1.7. The prevailing PZT crystal structure at a Zr/Ti composition of around 60/40 was rhombohedral; the tetragonal phase also began to appear in Ti-richer PZT compositions (Zr/Ti ≤ 50/50). The developed understanding established the basis for further tailoring of PZT particle morphologies for application-oriented or fundamental research

Morphology Control of PbZr_xTi_1-xO₃ Crystallites under Alkaline Hydrothermal Conditions

Outstanding ferroelectric and piezoelectric properties of PbZrxTi1-xO3 (PZT) make nano and sub-micrometer particles of this material interesting for future nanotechnological applications as well as for fundamental studies of ferroelectricity at the nanoscale. In the present work, the prospects of a new hydrothermal approach were explored to control the particle size, aggregation stage, and composition of the PZT with the target composition of Zr/Ti = 60/40 (x = 0.6). Starting with water-soluble Zr-, Ti-, and Pb-precursors, the PZT formation was examined in the broad base (KOH) concentration range. The PZT particle size and composition were governed by the ratio of KOH with respect to Pb and not by the absolute KOH concentration (cKOH). The incorporation of Zr into the PZT perovskite phase began to decline at KOH:Pb ≤ 1.7 and at KOH:Pb > 20. In the concentration range of 20 ≥ KOH:Pb > 1.5, the PZT particles adopted a cube-like shape, the size of which decreased with a decrease in the KOH:Pb ratio. The smallest (<200 nm) and well-separated PZT particles were obtained at KOH:Pb = 1.7. The prevailing PZT crystal structure at a Zr/Ti composition of around 60/40 was rhombohedral; the tetragonal phase also began to appear in Ti-richer PZT compositions (Zr/Ti ≤ 50/50). The developed understanding established the basis for further tailoring of PZT particle morphologies for application-oriented or fundamental research

Nanogallium-poly(L-lactide) Composites with Contact Antibacterial Action

In diverse biomedical and other applications of polylactide (PLA), its bacterial contamination and colonization are unwanted. For this reason, this biodegradable polymer is often combined with antibacterial agents or fillers. Here, we present a new solution of this kind. Through the process of simple solvent casting, we developed homogeneous composite films from 28 ± 5 nm oleic-acid-capped gallium nanoparticles (Ga NPs) and poly(L-lactide) and characterized their detailed morphology, crystallinity, aqueous wettability, optical and thermal properties. The addition of Ga NPs decreased the ultraviolet transparency of the films, increased their hydrophobicity, and enhanced the PLA structural ordering during solvent casting. Albeit, above the glass transition, there is an interplay of heterogeneous nucleation and retarded chain mobility through interfacial interactions. The gallium content varied from 0.08 to 2.4 weight %, and films with at least 0.8% Ga inhibited the growth of Pseudomonas aeruginosa PAO1 in contact, while 2.4% Ga enhanced the effect of the films to be bactericidal. This contact action was a result of unwrapping the top film layer under biological conditions and the consequent bacterial contact with the exposed Ga NPs on the surface. All the tested films showed good cytocompatibility with human HaCaT keratinocytes and enabled the adhesion and growth of these skin cells on their surfaces when coated with poly(L-lysine). These properties make the nanogallium-polyl(L-lactide) composite a promising new polymer-based material worthy of further investigation and development for biomedical and pharmaceutical applications

The role of paraffin wax on the properties and printability of ethylene vinyl acetate-based feedstocks for alumina fused filament fabrication

Fused filament fabrication (FFF) is a versatile and inexpensive additive manufacturing (AM) technique for fabrication of complex shaped ceramic structures. The composition of the binder phase in ceramic-filled feedstock is crucial in determining its rheological behaviour during processing as well as the ability to obtain a defect-free part following debinding and sintering. In this study, the effect of paraffin wax (PW) addition to alumina feedstock with ethylene vinyl acetate (EVA) binder, on feedstock preparation, printability, and debinding has been investigated. The PW incorporation resulted in successful fabrication of a flexible filament with a bending (fracture) strain of 4±1 %. The addition of PW however did not have a significant impact on the debinding of the developed alumina filaments. The printed parts could only be successfully debinded up to 2 mm wall thickness. The subsequent sintering of the debinded parts resulted in a relative density of 98 %

Solvothermal synthesis of zinc- and gallium-substituted cobalt ferrite nanoparticles

In the last two decades, cobalt ferrite (CoFe2O4, CFO) has attracted extensive attention due to its applicability in data storage, catalysis, energy, environment, and in particular, biomedicine. To further extend applicability and improve understanding of fundamental processes, the present work investigates the influence of heteroatoms on physicochemical properties of CFO. Solvothermal method was used for designing a non-agglomerated particles with uniform morpho-structural properties. The physicochemical properties of Zn2+ and Ga3+ substituted CFO nanoparticles were examined (Co(1-x)ZnxFe2O4 and CoGaxFe(2-x)O4; x=0, 0.1, 0.3 and 0.5). In order to isolate the contribution of heteroatoms, the synthesis condition were optimized to allow preparation of nonagglomerated particles with the narrow particle size and shape distribution, including the constant amount of capping agent. The X-ray diffraction (XRD) measurements confirmed the presence of pure cubic spinel phase in all samples, while the transmission electron microscopy (TEM) showed sphere-like nanoparticles with a mean diameter of 6±1 nm. The amount of adsorbed oleic acid on the surface of the nanoparticles, determined by thermogravimetric (TG) analysis, is 22-28 %, which indicates the formation of a complete monolayer of surfactant. The FT-IR analysis substantiated the presence of oleic acid on the surface of the nanoparticles and discovered its covalent bonding to the metal atoms. Substitution of host-atoms was also confirmed by Raman spectroscopy. Magnetic measurements revealed the influence of heteroatoms on saturation magnetization and magnetic anisotropy, showing for all the samples superparamagnetic behavior at room temperature. The substitution of Co2+ and Fe3+ ions with Zn2+ and Ga3+, respectively, leads to the change in chemical composition and cationic distribution of CFO and consequently to variation of its magnetic properties that can be tuned for different applications

Peculiarities in sintering behavior of Ca-deficient hydroxyapatite nanopowders

We report unusual sintering behavior of Ca-deficient hydroxyapatite processed with different heating rates; particularly, faster heating resulted in higher densification. We hypothesize that faster heating delays formation of β-tricalcium phosphate which yields to unobstructed densification in intermediate sintering stage, allowing further tailoring of both microstructure and phase composition (hydroxyapatite/tricalcium phosphate)

Dense fine-grained biphasic calcium phosphate (BCP) bioceramics designed by two-step sintering

In this study, dense, fine-grained biphasic calcium phosphate bioceramics were designed via the two-step sintering method. The starting powder was nanosized calcium-deficient hydroxyapatite, whose phase composition, average particle size and morphology were characterized by XRD, FTIR, Raman spectroscopy, laser diffraction and FE-SEM. The phase transformations of the initial powder during heating up to 1200 °C were examined using TG/DSC. At first, conventional sintering was performed and the recorded shrinkage/densification data were used to find out the appropriate experimental conditions for two-step sintering. The obtained results show that two-step sintering yields BCP ceramics, consisting of hydroxyapatite and β-TCP, with full dense, homogeneous structure with average grain size of 375 nm. Furthermore, BCP ceramics obtained by the two-step sintering method exhibit improved mechanical properties, compared to conventionally sintered BCP