Search

In this study, microstructural variation of hydroxyapatite (HAp) ceramics upon thermal treatment in air at different temperatures was investigated by x-ray diffraction patterns, Raman and x-ray photoelectron spectroscopies. The results revealed a significant dependence of the microstructure of nonstoichiometric HAp on temperature, because of the competition between hydroxylation and different kinds of dehydroxylation at different temperatures, and a gradual increase in material hardness with annealing temperature because of structural reconstruction. In summary, a suitable thermal treatment can effectively tailor microstructure and defect contents, as well as chemical composition and mechanical hardness of HAp ceramics. [ABSTRACT FROM AUTHOR]

The effect of yttria content on structural and thermal stability of zirconia in yttria-stabilized zirconia (YSZ) polycrystalline ceramics was systematically investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. Taking advantage of an experimentally retrieved linear dependence of Raman bandwidth on yttria content, Raman imaging was applied as an effective tool in examining the local yttrium distribution in YSZ ceramics and its relationship with environmentally driven polymorphic transformation. A significant variation of monoclinic fraction with yttria content and temperature was found and interpreted according to a newly proposed model, which takes into account the change in lattice hydroxyl and oxygen vacancies and the possible formation of stable defect complexes. [ABSTRACT FROM AUTHOR]

Structural variations and phase stability in 3 mol% yttria stabilized tetragonal zirconia (3Y-TZP) subjected to long-term aging at room temperature and thermal treatments in air were investigated by Raman and X-ray photoelectron spectroscopies, and compared with previous cases obtained by hydrothermal treatments. The results revealed a significant difference in the kinetics of zirconia polymorphic transformation in different environments due to the critical roles played by surface and lattice hydroxyl defects. Thermal treatments in air of long-term stored 3Y-TZP revealed a gradual recovery to tetragonal phase due to the ocurrence of dehydroxylation, while thermal treatments of pristine 3Y-TZP caused tetragonal-to-monoclinic polymorphic transformation at low temperature, but then an inverse transformation at higher tempertures due to a competition of hydroxylation and dehydroxylation. Treatments of 3Y-TZP in different environments were found to lead to distinct paths of off-stoichiometric chemistry, including hydroxylation, hydroxyl migration, surface reconstruction, and dehydroxylation during the treatments. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films represent promising surface treatments for biomedical implants. In this paper, using Raman and X-ray photoelectron spectroscopies, we analyzed the effects of secondary phases present in ZrO 2 substrates on the structure of DLC films fabricated by plasma-based ion implantation and deposition method, and the structural stability of the films in response to applied indentation prints. The results revealed oxygen incorporation in DLC films from the oxide substrates during deposition, and a clear dependence of sp3 carbon content on the oxygen fraction of the substrate and on gas pressure. Moreover, a pronounced structural distortion of the DLC films at the film/substrate interface was observed, which resulted from polymorphic transformation on the zirconia surface during deposition, while a pronounced change in Raman spectral morphology of carbon induced by structural alterations could also be observed around the indentation prints. The findings clearly pointed at the need to take into considerations the structural alterations of the DLC film structure at the interface associated with interfacial defects and film adhesion, especially for biomedical applications that involve surface loading. [Display omitted] • Effects of secondary phases in ZrO 2 substrates on the DLC structure were clarified. • Structural stability of the films in response to applied loads was investigated. • Oxygen incorporation in DLC films depended on both substrate and gas pressure. • Phase transformation of zirconia contributed to structural distortion of DLC films. • Structural alterations were induced around the indentation prints on the DLC films. [ABSTRACT FROM AUTHOR]

In the current study, high-temperature stability was investigated in two types of zirconia ceramics stabilized with two different additives, namely, calcia and yttria. The evolutions of structure and oxygen-vacancy-related defects upon annealing in air were investigated as a function of temperature by combining X-ray diffractometry with Raman, X-ray photoelectron and cathodoluminescence spectroscopies. We systematically characterized variations in the concentration of oxygen vacancies and hydroxyl groups during thermal treatments and linked them to structural alterations and polymorphic transformation. With this approach, we clarified how the combined effects of different dopants and temperature impacted on structural development and on the thermal stability of the oxygen-vacancy-related defect complex. [ABSTRACT FROM AUTHOR]

Hazelnut shell activated carbon materials (HSACs) are promising electrode materials used for supercapacitors, due to their superior natural performance. In this research, characterizations of surface features and electrochemical performance on a series of HSACs prepared with changing calcination temperature and mass ratio of activators showed that HSACs with larger specific surface area experienced lower specific capacitance. Further structural and compositional evaluations of the HSACs by Raman and X-ray photoelectron spectroscopy revealed that upon increasing calcination temperature or activator content, the specific surface area increased, but the carbon sp2/sp3 ratio and the concentration of acidic surface oxide groups decreased, and the population of basic surface oxide groups increased. These latter trends might be responsible for the decrease of specific capacitance of HSACs. The more Zn(NO 3) 2 activator was suppressed, the more basic surface oxide groups generated. In conclusion, this study clarified that the capacitance performance of HSACs was affected by the combined effect of micropore features and structural characteristics of HSACs, including electrical conductivity of sp2 C˭C bonds, various functional groups content, and groups inducing changes in adsorption property. [Display omitted] • Hazelnut shell activated carbons were synthesized through synergistic effect of Zn(NO 3) 2 and KOH activators. • HSACs with larger specific surface area experienced lower specific capacitance. • Structural alterations of HSACs upon fabrication under different conditions were clarified. • Effects of surface functional group on the specific capacitance of HSACs were investigated. • Combined effect of micropore features and structural characteristics determined the capacitance performance of HSACs. [ABSTRACT FROM AUTHOR]

The surface chemistry of silicon nitride plays an important role in stimulating osteoblasts to proliferate and produce bone tissue with improved efficiency. This property, which is advantageous in spinal fusion surgery has a chemical origin and is a direct consequence of the cleavage of covalent S N bonds in an aqueous environment. Building upon a wealth of published research on the stimulation of osteoblastic activity by silicon, the aim of this paper is to explore the role of nitrogen and, more specifically, the N/Si atomic ratio on the osteogenic response of Si 3 N 4. The surface stoichiometry of Si 3 N 4 was gradually altered toward a silicon-rich composition by systematically treating the Si 3 N 4 surface with a high-power pulsed laser in an Ar gas atmosphere (i.e., operated at different pulse times, spot sizes, and voltages). Different analytical probes were used to characterize the surface including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and energy dispersive X-ray spectroscopy (EDS). Osteoconductivity was tested in vitro using SaOS-2 osteosarcoma cells, and samples with different surface stoichiometry were compared for their osteogenic response. These experiments clearly indicated a fundamental role for nitrogen off-stoichiometry in osteogenesis, and showed that both cell proliferation and growth of bone tissue diminished with decreasing nitrogen content. Unlabelled Image • Silicon nitride surfaces were successfully treated using a ND:YAG pulsed laser. • The pulsed laser treatment resulted in a Si-enriched material. • Metallic silicon domains are formed on the surface of silicon nitride after treatment. • Si-rich areas showed poorer osteogenic capabilities. [ABSTRACT FROM AUTHOR]

The availability of osteoinductive biomaterials has encouraged new therapies in bone regeneration and has potentially triggered paradigmatic shifts in the development of new implants in orthopedics and dentistry. Among several available synthetic biomaterials, bioceramics have gained attention for their ability to induce mesenchymal cell differentiation and successive bone formation when implanted in the human body. However, there is currently a lack of understanding regarding the fundamental biochemical mechanisms by which these materials can induce bone formation. Phenomenological studies of retrievals have clarified the final effect of bone formation, but have left the chemical interactions at the cell–material interface uncharted. Accordingly, the knowledge of the intrinsic material properties relevant for osteoblastogenesis and osteoinduction remains incomplete. Here, we systematically monitored in vitro the chemistry of mesenchymal cell metabolism and the ionic exchanges during osteoblastogenesis on selected substrates through conventional biological assays as well as via in situ and ex situ spectroscopic techniques. Accordingly, the chemical behavior of different bioceramic substrates during their interactions with mesenchymal cells could be unfolded and compared with that of biomedical titanium alloy. Our goal was to clarify the cascade of chemical equations behind the biological processes that govern osteoblastogenic effects on different biomaterial substrates. [ABSTRACT FROM AUTHOR]

A chemically-treated titanium alloy (Ti6Al4V) surface, able to induce hydroxyapatite precipitation from body fluids (inorganic mineralization activity), was functionalized with a polyphenolic extract from green tea (tea polyphenols, TPH). Considering that green tea polyphenols have stimulating effects on bone forming cells (biological mineralization), the aim was to test their osteoinductive behavior due to co-operation of inorganic and biological mineralization on mesenchymal stem cells KUSA A1. The functionalized surfaces were characterized by using the Folin–Ciocalteu method and X-ray photoelectron spectroscopy to confirm the successful outcome of the functionalization process. Two cell cultures of mesenchymal stem cells, KUSA A1 were performed, with or without osteoinductive factors. The cells and surfaces were characterized for monitoring cell viability and hydroxyapatite production: Fourier Transform Infrared Spectroscopy and Raman spectroscopy analyses showed deposition of hydroxyapatite and collagen due to the cell activity, highlighting differentiation of KUSA A1 into osteoblasts. A higher production of extracellular matrix was highlighted on the functionalized samples by laser microscope and the fluorescence images showed higher viability of cells and greater presence of osteocalcin in these samples. These results highlight the ability of polyphenols to improve cell differentiation and to stimulate biological mineralization, showing that surface functionalization of metal implants could be a promising way to improve osteointegrability. [ABSTRACT FROM AUTHOR]