Synthesis and characterization of spinel–forsterite nanocomposites

Although micron size forsterite is biocompatible, the degradation rate of this ceramic is extremely low, and the apatite formation ability is poor as well. In this study, the influence of nanostructure and the degree of crystallinity on the apatite formation ability and degradation rate were investigated. Forsterite was synthesized by 5 h of milling of talc and magnesium carbonate and subsequent annealing at 1000 °C in the presence of chloride ion. To investigate the in vitro bioactivity and degradability, the prepared forsterite powder was pressed in the form of tablets and then immersed in simulated body fluid (SBF) and Ringer's solution, respectively. The results showed that nanostructure forsterite powder with crystallite size of about 20 nm was bioactive and released magnesium ions in the SBF solution. With increasing crystallinity degree of nanostructure forsterite, the apatite formation ability and degradation rate decreased.     

Development of macroporous nanocomposite scaffolds of gelatin/bioactive glass prepared through layer solvent casting combined with lamination technique for bone tissue engineering

In this study, macroporous bioactive nanocomposite scaffolds were developed using cross-linked gelatin and bioactive glass (BaG) nanoparticles. First, BaG nanoparticles were synthesized via sol–gel method and characterized. Then, macroporous nanocomposites were prepared through layer solvent casting combined with freeze-drying and lamination techniques. This research has developed a new composition to produce a new bioactive nanocomposite which is porous with three-dimensional (3D) inter-connected microstructure, pore sizes are 200–500 μm, porosity are 72–86% and BaG nanoparticles are dispersed evenly among cross-linked gelatin matrices. It is mentionable that in this study, we have reported the formation of chemical bonds between BaG nanoparticles and gelatin for the first time. Finally, the in vitro cytocompatibility of the nanocomposite scaffolds was tested using SaOS-2 cell line.     

A modified method to synthesize single-phase forsterite nanoparticles at low temperature

In this paper forsterite (Mg₂SiO₄) nanopowder with particle size in the range of 33 and 112 nm was synthesized by a combination of sol–gel and ball milling methods. Magnesium nitrate and silica were used as the sources of magnesium and silicon in the forsterite nanopowder. Thermogravimetry (TG) analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and dynamic light scattering (DLS) techniques were utilized to characterize the synthesized powders. Single-phase nanocrystalline forsterite powder with mean crystallite size of about 16 nm was obtained from sol–gel method with subsequent ball milling for 5 h and heat treatment at 750 °C for 1 h. A combination of sol–gel and mechanical activation led to the formation of more homogeneous powder and subsequently lower sintering temperature to produce forsterite powder. In vitro biological studies were performed by immersing the forsterite samples in simulated body fluid (SBF). The results showed that nanostructure forsterite is bioactive and possessed apatite formation ability.     

Influence of annealing temperature on the structural and anti-corrosion characteristics of sol–gel derived,spin-coated thin films

Recently, an aqueous particulate sol–gel process using metallic chloride precursors was introduced to synthesize zirconium titanate. In this paper, the effect of annealing temperature on the structural and corrosion protection characteristics of spin-coated thin films obtained from this sol–gel system was investigated. Based on scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and spectroscopic reflectometry studies, it was found that the flatness and thickness of the thin films were decreased by increasing the annealing temperature. Also, the corrosion protection of stainless steel AISI 316L provided by the prepared coatings, as analyzed by electrochemical potentiodynamic polarization experiments in a simulated body fluid, was improved in this order: 500 °C-annealed sample<900 °C-annealed sample<700 °C-annealed sample, attributed to a compromise between the defect density and the adhesion of the films to the substrate.     

Synthesis and characterization of spray pyrolyzed mesoporous bioactive glass

Mesoporous bioactive glasses (MBGs) have recently been applied as important bone implant materials due to their high reactive surface areas and superior bioactivities. Various processes have been developed to fabricate MBGs. Among them, the sol–gel process is one of most popular. However, sol–gel has the drawbacks of discontinuous processing and long processing time, making it unsuitable for mass production. This study demonstrates a successful synthesis of MBGs using a spray pyrolysis (SP) method to overcome these problems. The bioactivities of the SP synthesized MBGs are correlated with the main SP processing parameter of calcination temperatures and their structures. Comparisons of the surface areas and bioactivities for the MBG particles prepared from the sol–gel and the SP process are included. Finally, the MBG formation mechanism using SP is proposed.     

Structural, optical and bioactive properties of calcium borosilicate glasses

Glass of composition 40SiO₂–20B₂O₃–30CaO–10M₂O₃ (M = Al, Cr, Y and La) were prepared by the splat quenching technique to investigate the effect of M₂O₃ on their bioactivity, structural and optical properties. Y₂O₃ and Cr₂O₃ containing glasses formed a crystalline hydroxyapatite (HA) layer after dipping in simulating body fluid (SBF) for 25 days. On the other hand, HA layer could not form in Al₂O₃ and La₂O₃ glasses. However, during soaking in SBF solution, these glasses exhibit higher dissolution rate, lower density and increased optical band gap as compared to unsoaked glasses. Their oxygen molar volume was also higher than for Y₂O₃ and Cr₂O₃ glasses. The change in composition affects the cross-link formation in the glass matrix and finally its durability and bioactivity in SBF. The results show that M₂O₃ plays an important role in controlling chemical durability and bioactivity of the glasses.     

Bioactive glass nanoparticles with negative zeta potential

The purpose of this work was to produce and characterize SiO₂–CaO–P₂O₅ bioactive glass nanoparticles with negative zeta potential for possible use in biomedical applications. 63S bioactive glass was obtained using the sol–gel method. X-ray fluorescence (XRF) spectroscopy and dispersive X-ray analysis (EDX) confirmed the preparation of the 63S bioactive glass with 62.17% SiO₂, 28.47% CaO and 9.25% P₂O₅ (in molar percentage). The in vitro apatite forming ability of prepared bioactive glass was evaluated by Fourier transform infrared spectroscopy (FTIR) after immersion in simulated body fluid (SBF). The result showed that high crystalline hydroxyapatite can form on glass particles. By the gas adsorption (BET method), particle specific surface area and theoretical particle size were 223.6 ± 0.5 m²/g and ∼24 nm, respectively. Laser dynamic light scattering (DLS) indicated particles were mostly agglomerated and had an average diameter between 100 and 500 nm. Finally, using laser Doppler electrophoresis (LDE) the zeta potential of bioactive glass nanoparticles suspended in physiological saline was determined. The zeta potential was negative for acidic, neutral and basic pH values and was −16.18 ± 1.8 mV at pH 7.4. In summary, the sol–gel derived nanoparticles revealed in vitro bioactivity in SBF and had a negative zeta potential in physiological saline solution. This negative surface charge is due to the amount and kind of the ions in glass structure and according to the literature, promotes cell attachment and facilitates osteogenesis. The nanometric particle size, bioactivity and negative zeta potential make this material a possible candidate for bone tissue engineering.     

Preparation,characterization and in vitro biological response of simultaneous co-substitution of Zr+4/Sr+2 58S bioactive glass powder

In the present study, structure of zirconium-containing bioactive glass (58S-BG (Zr-BG)) with optimal fixed Zr content (5 mol.%) was modified by incorporation of strontium (Sr). These Zr and Sr-containing BGs (ZS-BGs) were synthesized by sol-gel method and substitution of Ca with modifier ions (Sr content = 0, 3, 6, 9, and 12 mol.%). The results obtained from characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDS) techniques from surface of all the ZS-BGs revealed formation of hydroxyapatite (HA) after 7 days of immersion in the simulated body fluid (SBF) solution. Evaluation of changes in the SBF solution, by monitoring pH variations and ions? concentration, was in agreement with the results of morphological and structural investigations. The in-vitro biological function of synthesized BGs was studied through (MTT) assay and alkaline phosphatase (ALP) activity analysis. The results showed that all the specimens significantly stimulated proliferation and viability of MC3T3 osteoblast-like cells. Furthermore, antibacterial studies confirmed less resistance of methicillin-resistant Staphylococcus aureus (MRSA) bacteria against ZS-BGs. Eventually, the results of in-vitro bio-analysis were clarified and confirmed by two cell staining techniques of Live/Dead and Dapi/Actin. This confirmation was achieved by observing the increased quantity of live cells and their nuclei as well as the decreased number of dead cells after co-culturing with all ZS-BGs.     

Fabrication and characterization of bioactive glass/hydroxyapatite nanocomposite foam by gelcasting method

Bioceramic foams have been applied for drug releasing agents, cell loading, and widely for hard tissue scaffold. The aim of this study was fabrication and characterization of nanostructure bioceramic composite foam (BCF) consisting of hydroxyapatite (HA) and bioactive glass (BG) via gelcasting method for applications in tissue engineering. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis techniques were utilized in order to evaluate respectively, phase composition, dimension, morphology, and interconnectivity of pores, and particle size of synthesized HA, BG, and BCF. The results showed that fabrication of the BCF with a particle size in the range 20-42 nm and pore size in the range 100-250 μm was successfully performed. The maximum values of compressive strength and elastic modulus of the BCF were found to be about 1.95 MPa and 204 MPa, respectively, related to a sample sintered at 900 °C for 4 h. The mean values of the true (total) and apparent (interconnected) porosity were calculated in the range 86-91% and 60-71%, respectively. It seems that the measured properties make the BCF a good candidate for tissue engineering applications, preferentially in drug delivery, cell loading, and other nonloading applications.     

Synthesis of LiMn2O4 from a gelled ovalbumin matrix

A simple and inexpensive route for the preparation of LiMn₂O₄ using ovalbumin (egg white) as a gelating agent is described. Gelation of freshly extracted ovalbumin was effected by changes in ionic strength brought about by the addition of nitrate precursors to an aqueous solution of ovalbumin and subsequent warming. This resulted in tiny pockets of precursor materials getting trapped in the matrix of the gelled ovalbumin. Heat treatment of the gelled mass yielded submicron-sized LiMn₂O₄ crystals at temperatures as low as 400 °C.     

Combustion assisted synthesis of hardystonite nanopowder

In this study, single-phase hardystonite (Ca₂ZnSi₂O₆) nanopowder was synthesized by combustion synthesis method from aqueous solution of Calcium nitrate, Zinc nitrate and Tetraethyl orthosilicate. In order to characterize the obtained powders, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used. The effect of sucrose concentration on the purity and morphology of the obtained hardystonite powder, and its initial annealing temperature was investigated. The optimum sucrose to metal ratio was found to be 2:1. The average particle size and the maximum crystallite size of the produced hardystonite nanopowder were 220 and 40 nm, respectively.     

Synthesis,sintering and characterisation of TaON materials

Theoretical investigations predict that TaON is likely to possess a relatively high hardness, thus making it a candidate for application as an abrasive or cutting tool material [J.E. Lowther, Theoretical study of potential high pressure phases of TaON and quaternary ZrTaO₃N, in press]. TaON powder was produced by nitridation of amorphousTa₂O₅ powder in flowing ammonia in the 700–900 °C temperature range and an ammonia flow rate range of 40–50 cm³/min. The resulting powders were characterised in oxidation resistance by thermo-gravimetric analysis (TGA), phase purity by X-ray diffraction (XRD) and surface area by the BET method. The materials were densified under pressure using a belt type high pressure apparatus at 3–5.5 GPa in the temperature range of 920–1200 °C. The sintered samples were characterised in phase purity, Vickers macro-hardness and fracture toughness.     

Synthesis and structure of PMN–PT ceramic nanopowder free from pyrochlore phase

Single-phase perovskite 0.65PMN–0.35PT nanopowders were synthesized at low temperature by the auto-combustion method. PMN–PT powder with 1 mol% of excess Pb(NO₃)₂ was prepared from the constituent nitrates and alkoxide materials. Perovskite PMN–PT powders without any pyrochlore phase were obtained after heat treatment at 850 °C. The average particles diameter is estimated to be around 25 nm. The formation of perovskite phase and the optical constants of powders have been estimated using Fourier transform infrared (FTIR) spectroscopy.     

Synthesis and characterization of calcium silicate insulating material using avian eggshell waste

This work focuses on the synthesis of calcium silicate insulating material via solid state reaction using avian eggshell waste as alternative calcium source. The calcium silicate formulations were mixed in a molar ratio SiO₂:CaO (1:1) and fired at 1100 °C for 24 h. The calcium silicate formulations were characterized by XRD, TG-DTA, dilatometry, SEM/EDS, and thermophysical properties (thermal diffusivity, heat capacity per unit volume, and thermal conductivity). The synthesized calcium silicate materials are composed mainly of wollastonite with minor amounts of larnite and rankinite. It was found that a processing of the avian eggshell waste (raw eggshell waste and calcined eggshell waste) had an influence on the thermophysical properties. Calcium silicate pieces were prepared by uniaxial pressing at 82 MPa, curing, and then testing to determine their use as thermal insulating material. The microstructure was evaluated by SEM. The results showed that both raw and calcined avian eggshell wastes could be used as an alternative calcium source in the calcium silicate formulation. It was found that the calcium silicate pieces reached low thermal conductivity values (0.252–0.293 W/mK). Thus, the developed calcium silicate materials using avian eggshell waste act as a good thermal insulation ceramic material.     

Characterization,in vitro bioactivity and biological studies of sol-gel synthesized SrO substituted 58S bioactive glass

Bioactive glasses (BGs) are considered as a high potential candidate in bone repair and replacement. In the present study, sol–gel derived BGs based on 60% SiO₂-(36%-x) CaO-4%P₂O₅-x SrO (where x = 0, 5 and 10 mol%) quaternary system were synthesized and characterized. The effect of Sr substitutions on bioactivity, proliferation, alkaline phosphatase activity of osteoblast cell line MC3T3-E1 and antibacterial activity were investigated. Dried gels were stabilized at 700 °C to eliminate the nitrates and prevent the crystallization of bioactive glasses. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy results confirmed the formation of hydroxycarbonate apatite on the BG surfaces. The 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphate activity results showed that 5% SrO increased both differentiation and proliferation of MC3T3-E1 cells, while 10% SrO resulted in a decrease in bioactivity. Live/Dead and DAPI/Actin staining exhibited viable cell and the morphology of actin fibers and nuclei of MC3T3 cells treated with BG-0 and BG-5. The result of antibacterial test showed that strontium substituted 58S BG exhibited antibacterial effect against methicillin-resistant Staphylococcus aureus bacteria. Taken together, results suggest that 58S BG with 5 mol% SrO is a good candidate for bone tissue engineering with maximum cell proliferation and ALP activity, good bioactivity and high antibacterial efficiency.     

Synthesis, characterization and in vitro bioactivity of magnesium-doped sol-gel glass and glass-ceramics

Bioactive glass and glass-ceramics in the system CaO-MgO-SiO₂-P₂O₅ have been prepared by the sol-gel and high temperature sintering techniques. The obtained samples were characterized by thermogravimetric and differential thermal analysis (TG/DTA), N₂-adsorption measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In vitro bioactivity tests were also conducted in simulated body fluid (SBF). The studies of crystallization kinetics under non-isothermal conditions showed the activation energy for crystallization to be 381 kJ/mol and the crystallization mechanism gradually changed from three-dimension growth to two-dimension crystallization with the increase of heating rate. Sintering temperature had great influence on the samples texture and structure. In addition, the apatite-formation on glass and glass-ceramics was confirmed by in vitro tests, and crystallization decreased the samples bioactivity.     

Characterization of low-temperature solution-processed indium–zinc oxide semiconductor thin films by KrF excimer laser annealing

We have employed KrF excimer laser annealing (ELA) treatment on sol–gel derived indium–zinc oxide (IZO) precursor films to develop a method of low thermal-budget processing. As-coated IZO sol–gel film was dried at 150 °C and then annealed using KrF excimer laser irradiation under ambient air. The laser irradiation energy density was adjusted to 150, 250, 350, and 450 mJ/cm² to investigate the effects of laser irradiation energy density on the microstructure, surface morphology, optical transmittance, and electrical properties of laser annealed IZO thin films. Results of GIXRD and TEM-SAED indicated that the ELA IZO thin films had an amorphous phase structure. The surface characteristics and electrical properties of laser annealed IZO thin films were significantly affected by the laser irradiation energy density. It was found that the dried IZO sol–gel films irradiated with a laser energy density of 350 mJ/cm² exhibited the flattest surface, the highest average optical transmittance in the visible region, and the best electrical properties among all ELA samples.     

In vitro degradation and apatite-formation of ZnO–CaO–SiO2–P2O5 glass–ceramics by substitution of zinc for calcium

A series of CaSiO₃–Ca₂ZnSi₂O₇-based glass–ceramics of the type ZnO–CaO–SiO₂–P₂O₅ were successfully obtained by the partial substitution of calcium with zinc. The effect of zinc addition on structure, dissolution behavior and apatite-forming ability of the resultant glass–ceramics was comprehensively investigated by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG/DSC), and scanning electron microscopy coupled to an energy dispersive X-Ray spectrometer (EDS). The data revealed that the zinc addition favored the generation of Ca₂ZnSi₂O₇ and induced the formation of ZnSiO₄ and SiO₂ phases. In addition, the excessive content of these compounds led to the attendant loss in the dissolution rate and apatite-forming ability, indicating that the incorporation of zinc into CaSiO₃ is a promising route to regulate the dissolution and apatite formation of CaSiO₃–Ca₂ZnSi₂O₇- based bioceramics.     

Synthesis and characterization of chlorinated hydroxyapatite as novel synthetic bone substitute with negative zeta potential

In the present work, chlorine doped hydroxyapatite (ClHA), with varying degrees of ion replacement was successfully synthesized by a simple ball milling technique. The resulting powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy and particle size analyzer. The zeta potential of the powders was performed in physiological saline (0.154 M). The results confirmed the formation of apatite as the main phase in all chlorine substituted powders except for some incremental changes in the lattice parameter ‘a’ and unit cell volumes of the resultant powders. However, the crystallinity of the powders declined from 96% to 83%. Fourier transform infrared spectroscopy results confirmed the incorporation of Cl ions in the apatite lattice by the appearance of new bands at 677 cm^-1. FESEM results revealed that the crystallites have grown into grains with no major agglomeration. Vicker hardness test results revealed a hardness value of 2.65 ± 0.258 GPa for ClHA4 dense bodies at a load of 200g. Zeta potential analysis of the powders suggested that ClHA nanopowders can prove to be a potential bone implant material.     

Fabrication and characterization of sol–gel derived hydroxyapatite/zirconia composite nanopowders with various yttria contents

Homogeneous composite nanopowders of hydroxyapatite/30 wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8 mol% Y₂O₃ (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared nanopowders. Analyses of HA–YSZ composite nanopowders showed the successful formation of desirable phases. HA unit cell volume in the composites increased as a result of ion exchange of calcium and zirconium between HA and zirconia. Results revealed the formation of HA particles with irregular morphology (40–80 nm) and spherical yttria-stabilized zirconia particles (20–30 nm). Segregation of yttrium ions at the grain boundaries of ZrO₂ particles retarded the grain growth of zirconia particles and the presence of ZrO₂ nanoparticles among the hydroxyapatite particles resulted in grain growth inhibition of HA particles. This process can be used to synthesize HA–YSZ composite nanopowders with improved properties, which are much needed for hard tissue repair and biomedical applications.