SiO2 CaO P2O5 Research Articles

Composite Ceramics in the Na2O–CaO–SiO2–P2O5 System Obtained from Pastes including Hydroxyapatite and an Aqueous Solution of Sodium Silicate

The new approach to obtaining ceramic materials in the Na2O–CaO–SiO2–P2O5 system based on the binder—an aqueous solution of sodium silicate and filler—hydroxyapatite was shown in current research. After heat treatment at 500 °C and 700 °C, the ceramic samples included non-reacted hydroxyapatite Ca10(PO4)6(OH)2, β-rhenanite β-NaCaPO4 and sodium calcium silicophosphate Na2Ca4(PO4)2SiO4. An increase in temperature to 900 °C and 1100 °C allowed to obtain ceramic materials with the following phases: devitrite Na2Ca3Si6O16, β-rhenanite β-NaCaPO4, β-wollastonite β-CaSiO3, and silicon dioxide SiO2. The strength of ceramic samples rose with increasing temperature from ≈7.0 MPa (bending) and ≈7.2 MPa (compression) at 500 °C to ≈9.5 MPa (bending) and ≈31.6 MPa (compression) at 1100 °C. At the same time, the apparent density decreased from 1.71 g/cm3 to 1.15 g/cm3. The top of the compressive strength equal to 31.6 MPa was observed when the apparent density was 1.15 g/cm3. Obtained ceramics consisted of biocompatible phases, widely studied in the literature; thus, it confirms the possibility of using an aqueous solution of sodium silicate in medical materials science.

In vitro evaluation of bioactivity of SiO2–CaO and SiO2–CaO–P2O5 glass nanoparticles activated with Tm3+/Yb3+ ions

In this study, the SiO2–CaO (SC) and SiO2–CaO–P2O5 (SCP) glass powders doped with 0.3 mol% of Tm3+ and 4 mol% of Yb3+ ions were prepared by the sol–gel method. The samples were immersed for four weeks in a simulated physiological environment (Dulbecco's phosphate-buffered saline, DPBS) to investigate the bioactivity of the glasses. Their structure, morphology, and spectroscopic properties were investigated in the function of immersion time. X-ray diffractograms and infrared spectra showed that after incubation in DPBS, the hydroxyapatite starts to build up after 1–3 days. The energy dispersive X-ray spectroscopy analysis indicated the dynamics of ion exchange resulting from the biomineralization process in the glasses. Moreover, the upconversion emission spectra of Tm3+ were measured for all samples under 980 nm excitation wavelength in resonance with the 2F7/2 → 2F5/2 absorption of Yb3+. It was observed that the upconversion luminescence continuously decreased and the decay times shorten slightly after the immersion in the buffer. In vitro cytotoxicity assays revealed that the SC glass was biocompatible for all tested cell lines (human chondrocytes, osteoblasts, and fibrosarcoma). However, the SCP powder showed an inhibitory effect on human chondrocyte and fibrosarcoma cells in small concentrations and fibrosarcoma cells in high concentrations.

Structure, Morphology and Bioactivity of Bioactive Glasses SiO2–CaO–P2O5 Doped with ZnO Synthesized by Green Synthesis

Structure, Morphology and Bioactivity of Bioactive Glasses SiO2–CaO–P2O5 Doped with ZnO Synthesized by Green Synthesis

Analysis of phase transformations of modified silicate xerogels during heat treatment

The ways of obtaining glass for dental cements with low synthesis temperature were analyzed. The xerogels of the SiO2–CaO–P2O5 systems were synthesized by sol-gel technology from affordable raw materials. The physicochemical processes, temperature regions of phase transformations and intensity of their course, which occur during heat treatment of xerogels of two series of the system at the SiO2 content of 50 wt.% and 60 wt.% were investigated by the method of differential thermal analysis. Analysis of the obtained results allowed us to affirm that all regions of phase transformations in the xerogel powders with 50 wt.% SiO2 content shifted to the lower temperature range. It was established that an increase in the temperature during heat treatment of the xerogel powders with different compositions led to the phase transformations: from a loose powdered state through a sintered state to the formation of a glassy state. It was determined that all samples are X-ray amorphous up to the temperature of 6500C. It was shown that increasing the CaO content in the composition of xerogels up to 30 wt.%, and accordingly increasing the ratio CaO:P2O5 from 1 to 6, leads to the absence of glass phase. The optimal ratio CaO:P2O5 is 2. The influence of Li2O and BaO on a decrease in the glass formation temperature was substantiated and experimentally confirmed by thermal analysis.

Novel CaO-SiO2-P2O5 Nanobioglass Activated with Hafnium Phthalocyanine.

Bioactive glasses are materials which can be used in medicine for regeneration of hard and soft tissues. Their functionalization with active molecules or addition to composites broaden significantly the possible range of glass applications. Hereby, we describe photoactive nanoparticles of CaO–SiO2–P2O5 glass modified with dichlorohafnium (IV) phthalocyanine. The low-temperature, sol–gel based reverse micelle method was proposed for the synthesis, which allowed introduction of metal organic molecules into the glass composition. The morphology, structure, and composition of the material was described showing that spherical but agglomerated glass nanoparticles (size below 100 nm) were obtained in the ternary system. It was also shown that optical properties of the phthalocyanine complex were maintained after immobilization of the dye in the glass. The photoluminescence and generation of singlet oxygen molecules were observed under the light irradiation of the glass.

Synthesis of bioactive glass using cellulose nano fibre template

This study introduces a templating approach using a cellulosic suspension to create a porous SiO2–CaO–P2O5–Na2O bioactive glass material. Sol-gel approach was used as the synthesis method. Carbon nanofibers in suspension form was used as the templating material. The amount of CNF used in the experiment ranged from 5% to 25% by volume. The morphology, porosity, crystallinity of the combeite phase, mechanical and chemical properties of the BG samples were examined. The findings show that the templating method had no effect on the formation of the required functional elements, such as Si, Ca, Na and P. The porosity of the BG materials improves by 15% after templating compared to the neat sample. The formed pores were assumed to be homogenous based on the uniform adsorption and desorption BET profiles. The crystallization mechanisms during the sintering process were affected by the templating approach, indicating the need for a specific amount of template to be used in the preparation step. Both the sintering temperatures and the CNF content affected the formation of the combeite phase. The BG samples had excellent mechanical properties and are suitable for use in cancellous bone applications. As a result, this study shows a novel method for synthesizing porous bioactive glass materials via the sol-gel method and a CNF suspension as a template.

Processing of highly porous bioglass monoliths by hydrothermal hot pressing

Porous bioglass monoliths have been processed by hydrothermal hot pressing (HyHP) from sol-gel and melt-derived bioglass powders of composition (in mol %): SiO2–CaO–P2O5 (55.0-40.0-5.0) and SiO2–CaO–Na2O–P2O5 (47.2-26.4-23.8-2.6), respectively. An open porosity of >70% ever reached in 3D structures is reported for monoliths issued from sol-gel powders. Dissolution studies were performed in simulated body fluid (SBF) for 1–30 days. The monoliths were analysed using X-Ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) to observe the formation of an apatite-like layer and elemental concentration of SBF was evaluated using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). A higher kinetics in the development of apatite layer was observed for sol-gel derived monoliths. This result is explained by the high surface areas of the nanosized sol-gel powders and the possibility of HyHP to create large porosity (mesoporous monoliths) and retain large surface areas. HyHP is also effective in processing 3D-bioglass structures with porosity gradient by co-sintering powders of different size.

Foam-Replicated Diopside/Fluorapatite/Wollastonite-Based Glass–Ceramic Scaffolds

Implantation of three-dimensional (3D) bioactive glass-derived porous scaffolds is an effective strategy for promoting bone repair and regeneration in large osseous defect sites. The present study intends to expand the potential of a SiO2–P2O5–CaO–MgO–Na2O–CaF2 glass composition, which has already proven to be successful in regenerating bone in both animals and human patients. Specifically, this research work reports the fabrication of macroporous glass–ceramic scaffolds by the foam replica method, using the abovementioned bioactive glass powders as a parent material. The sinter-crystallization of the glass powder was investigated by hot-stage microscopy, differential thermal analysis, and X-ray diffraction. Scanning electron microscopy was used to investigate the pore–strut architecture of the resultant glass–ceramic scaffolds in which diopside, fluorapatite, and wollastonite crystallized during thermal treatment. Immersion studies in simulated body fluids revealed that the scaffolds have bioactive behavior in vitro; the mechanical properties were also potentially suitable to suggest use in load-bearing bone applications.

Sustainable glasses in the SiO2–P2O5–CaO–K2O system from waste and concentrated solar power

Sustainable glasses were prepared by green technology including the use of different wastes as raw materials and concentrated solar power (CSP) as renewable energy. The raw materials used to formulate the glasses were animal bone flour ash, which presents high contents of CaO, P2O5 and alkaline oxides; glassy sand from the waste of packaging glass submitted to a primary treatment, composed principally of SiO2; and potassium carbonate of reagent grade. Different exposure times to solar radiation were tested. For comparison, the same composition of glass was melted into a conventional electric furnace. The use of CSP to produce glasses reduces the melting time by approximately 90%, with consequent energy savings. The increased CSP processing time results in more amorphous and thermally stable glasses. The results showed the viability of producing ecofriendly glasses in the SiO2–P2O5–CaO–K2O system, which could be used as matrix-based fertilizers.

Modification of mesoporous structure of silver-doped bioactive glass with antibacterial properties for bone tissue applications

Silver-containing mesoporous bioglasses powders with SiO2–CaO–P2O5–Ag2O composition have been successfully synthesized by sol-gel and evaporation-induced self-assembly (EISA) methods in presence of various amounts of surfactant (Pluronic-F127). The morphology and crystal structure of the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD). Also, the textural properties of samples have been evaluated by adsorption-desorption, Langmuir and BET methods. Accordingly, powders had a smooth surface morphology with cubic mesoporous structure and a desired surface area and pore volume. The in vitro bioactivity was assessed by SEM, XRD and Fourier transform infrared spectroscopy (FTIR) analyses. All samples enhance the formation of HA after soaking the material in simulated body fluid (SBF) solution. The antibacterial property of samples was evaluated to investigate the effect of silver content in chemical composition. The results showed an adequate antibacterial activity of the samples against Escherichia coli, Salmonella and Listeria monocytogenes.

Distinct Methodologies to Produce Capped Mesoporous Silica with Hydroxyapatite and the Influence in Intracellular Signaling as Cytotoxicity on Human Umbilical Vein Endothelial Cells.

Mesoporous silica has unique properties such as controllable mesoporous structure and size, good biocompatibility, high specific surface area, and large pore volume. For that reason, this material has been broadly functionalized for biomedical applications, such as optical imaging, magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), ultrasound imaging, and widely employed as drug delivery systems. In this study, we synthesized fiber-type mesoporous silica capped with hydroxyapatite (ordered SiO2–CaO–P2O5 mesoporous silica). Its biological activity was evaluated through a cellular and molecular approach using HUVEC cell culture. Two distinct methodologies have produced the ordered SiO2–CaO–P2O5 mesoporous silica: (i) two-step Ca-doped silica matrix followed by hydroxyapatite crystallization inside the Ca-doped silica matrix and (ii) one-step Ca-doped silica matrix formed with the hydroxyapatite crystallization. Further analysis included: elemental analysis, transmission, scanning electron microscopy images, Small and Wide-Angle X-ray Diffraction analysis, Fourier Transform Infrared, and in vitro assays with HUVEC (cytotoxicity and immunoblotting). The hydroxyapatite capping methodology significantly affected the original mesoporous material structure. Furthermore, no cellular or molecular effect has been observed. The promising results presented here suggest that the one-step method to obtain hydroxyapatite capped mesoporous silica was effective, also demonstrating that this material has potential in biomedical applications.

Sol-Gel Preparation and Properties of Thin-Film Biomaterials for the SiO2–P2O5–CaO–ZnO System

Sol-Gel Preparation and Properties of Thin-Film Biomaterials for the SiO2–P2O5–CaO–ZnO System

Behavior of molybdenum lowly doped SiO2–CaO–P2O5 composite interfacing a simulated biologic medium with serum albumin

This study is focussed on the biocompatibility evaluation by probing the affinity of bovine serum albumin (BSA) towards the surface of a silica based material containing CaMoO4 and hydroxyapatite nanocrystals. The adsorption occurring upon BSA interaction with the sample surface was investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The elemental composition and evaluation of protein surface coverage based on information from the outermost few nanometres surface layer was achieved by XPS analysis. The ratio between carbon and nitrogen on the material surface after incubation in BSA solution was found to be reasonable close to the value obtained from the measurement of pure BSA, that proves the protein adsorption. The comparative analysis of FTIR spectra recorded from lyophilized protein and from biomaterial surface after protein adsorption was considered in order to obtain information about the secondary structure of the proteins. The protein surface coverage was also confirmed by SEM morphological characterization. The results obtained by in vitro test indicate that the nanostructured SiO2–CaO–P2O5−MoO3 system has a great potential for bone tissue engineering with respect to the ability to bind to serum protein.

Ce/Sm/Sr-Incorporating Ceramic Scaffolds Obtained via Sol-Gel Route.

Three different inorganic scaffolds were obtained starting from the oxide system SiO2‒P2O5‒CaO‒MgO, to which Ce4+/Sm3+/Sr2+ cations were added in order to propose novel materials with potential application in the field of hard tissue engineering. Knowing the beneficial effects of each element, improved features in terms of mechanical properties, antibacterial activity and cellular response are expected. The compositions were processed in the form of scaffolds by a common sol-gel method, followed by a thermal treatment at 1000 and 1200 °C. The obtained samples were characterized from thermal, compositional, morphological and mechanical point of view. It was shown that each supplementary component triggers the modification of the crystalline phase composition, as well as microstructural details. Moreover, the shrinkage behavior is well correlated with the attained compression strength values. Sm was proven to be the best choice, since in addition to a superior mechanical resistance, a clear beneficial influence on the viability of 3T3 fibroblast cell line was observed.

Reaction Characteristics and Existing Form of Phosphorus during Coal-Based Reduction of Oolitic Iron Ore

It is particularly significant to investigate the reduction behavior and existing form of phosphorus in metal and slag phase during coal-based reduction for the efficient development and utilization of high-phosphorus oolitic hematite. The reduction behavior of phosphorus minerals and their existing form in the metal and slag phase during the coal-based reduction of high phosphorus oolitic hematite were systematically investigated using HSC software simulation, thermodynamic calculation, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The results show that after Fe2O3 was reduced to metal iron, the reduction of apatite was promoted by providing the most inclined enrichment site of phosphorus (metallographic phase). Phosphorus existed mainly in two forms in the metal phase—one was in the form of Fe3P compound at the boundary of the metal phase, and the other was in the form of solid solution in the metal iron. There were two forms of phosphorus in the slag phase—one was incompletely reacted apatite, and the other was formed as CaO–SiO2–P2O5 solid solution. In the early stage of coal-based reduction, phosphorus in the slag phase mainly existed in the form of apatite, while in the later stage, it mainly existed in the form of CaO–SiO2–P2O5 solid solution.

Remineralising fluorine containing bioactive glass composites

ObjectivesThe objective was to investigate the mechanical properties, fluoride release and apatite formation of resin based dental composites based on a fluoride containing Bioactive Glass (BG) with and without a silylating agent. MethodsA SiO2–P2O5–CaO–SrO–Na2O–CaF2 BG was synthesized by the melt quench route. This glass and a commercially available inert glass (IG) were incorporated into a light cured BisGMA-TEGMA resin. The composite resins were then evaluated in terms of their ability to form apatite by Fourier Transform Infrared spectroscopy (FTIR) and by scanning electron microscopy (SEM) following immersion in artificial saliva at pH 4 (AS4) and pH 7 (AS7). The experiments were performed with and without silylation of the BG. The compressive strength and flexural strength were determined after 1, 28 and 84 days of immersion in the AS4 and AS7 immersion media. ResultsThe FTIR spectra of the BG composites exhibited split bands at approximately 560 and 600 cm−1 corresponding to a apatite formation in the surface or on the surface under all immersion conditions. SEM showed the presence of a reacted layer of glass particles in the composite surface and the presence of a surface layer of apatite in AS7.The compressive strength and flexural strength were significantly higher for the silylated BG composites. The strengths of both silylated and non silylated BG composites and IG composites decreased upon immersion. SignificanceBG composites exhibit reduced strengths upon immersion but still exhibit strengths comparable to existing composites after 84 days of immersion.

Highly improved biological and mechanical features of bioglass-ceramic/ gelatin composite scaffolds using a novel silica coverage

In the present study, mechanical and chemical properties of the bioglass-ceramic/gelatin composite scaffolds were investigated. The reinforcing particles were synthesized using the sol-gel method in SiO2–CaO–P2O5 systems. The composite scaffolds were also fabricated through solvent casting and freeze-drying routes. The effect of the chemical composition of the synthesized particles and temperature of the heat treatment process on the mechanical and chemical properties of the bioglass containing scaffolds were investigated in detail. Two different coverages, namely gelatin-glutaraldehyde and silica, were utilized for covering the composite scaffolds. According to the X-ray diffraction results, heat-treating the particles at 1100 °C caused the crystallization of the Ca3(PO4)2 phase. Based on the three-point flexural test results, the final mechanical strength of the gelatin-glutaraldehyde-covered scaffolds ranged between 2 and 4 MPa. Covering the composite scaffolds with the silica coverage remarkably increased the final strength values ranging between 12 and 18 MPa. The in vitro cell-based experiment results indicate the cytocompatibility of the scaffolds when they are incubated with dental pulp stem cells. Also, the presence of the silica coverage on the scaffolds increased the viability of the stem cells in comparison with the gelatin-glutaraldehyde-covered scaffolds. Furthermore, evaluation of the bioactivity behavior of the scaffolds showed that the Ca2SiO4 phase was formed on the surface of the samples from 7 to 21 days of immersion in simulated body fluid (SBF). The morphology of the mineralized phase on the surface of the scaffolds changed from Cauliflower to rod-like nodules by changing the type of scaffold coverage from gelatin-glutaraldehyde to silica after immersion in SBF media. Altogether, the bioglass-ceramic/gelatin composite scaffolds could have a promising role in bone tissue engineering application.

Differential scanning calorimetry and NMR study of water confined in a mesoporous bioactive glass

The emergence of a new generation of nanostructured materials opened a wide range of new potential applications for Bioglasses such as DNA vaccination, cellular treatment or drug delivery with a well-controlled loading and release of (bio)active molecules. In this study we compare structural, dynamic and thermal properties of water confined in two CaO–SiO2–P2O5 mesoporous bioactive glasses (MBGs). One of the MBGs is prepared by standard sol-gel methods and the other by microfluidic procedures, therefore both MBGs have the same molar compositions (92% SiO2, 6% CaO, and 2% P2O5) but different textural properties (surface areas, porous volume and grain architecture). These materials are intended to interact with body fluids which are essentially composed of water, it is therefore crucial to understand the water-MBG interaction. With this objective, we apply a complementary approach based on 1H field-cycling NMR relaxometry, 1H magic-angle spinning NMR spectroscopy and differential scanning calorimetry (DSC). With low-field relaxometry we observe that adsorbed water has the same behavior in the mesoporous channels of both systems, but that the escaping of water molecules towards the bulk is slightly faster in the microfluidic material. By combining 1H MAS NMR and DSC to study a series of MBG samples at variable temperature and water content, we observe that for low temperature and low water content, pooling of water molecules is less pronounced in the case of the microfluidic MBG. All our results therefore point towards a microcapsule organization of the microfluidic MBG that provides better water access to the full porous volume.

Structure and composition characterization of biocomposites filled with sol–gel bioglasses from the CaO–SiO2–P2O5–Ag2O systems

Lately silver has become extremely important among alloying additives used to produce glassy materials with specific tailored properties. The aim of the study is to characterize bioactive glasses belonging to the CaO–SiO2–P2O5–Ag2O system by SEM and EDX methods, as well as biocomposites based on natural rubber containing those fillers. The focus is on the influence that silver oxide and the mechanism of its effect have upon the properties of glasses and biocomposites. The results show that silver particles serve as crystallization centers for apatite formation in sol–gel glasses what leads to a serious change in the morphology and size of crystals and consequently in glass microstructure. Particles in the form of plates have been identified. This is an indication of silver-stimulated crystalline structure. A relation between the hydroxylapatite plaque and the concentration of silver particles has been found. The influence of silver oxide is expressed in noticeable changes in the adsorption texture properties of the glasses. In the composites, the aggregation of the filler particles has been observed and their size increases in the presence of silver oxide. The hydroxylapatite formed as a stand-alone phase in the sol–gel glass and acting as a filler has the most important role in tailoring the composite characteristics.

Alginate/Bioactive Glass Beads: Synthesis, Morphological and Compositional Changes Caused by SBF Immersion Method

Composites of biodegradable polymers/bioactive glasses (BG) are of particular interest in bone repair, where ceramic phase can improve osteogenic features. This work reports the development of organic–inorganic beads based on alginate prepared by incorporating at polymer suspension different contents (25, 50 and 75 wt% with respect to alginate) of BG present at precursor solution, whose system (SiO2–CaO–P2O5) was obtained by hydrolysis of both tetraethoxysilane (TEOS) and triethylphosphate (TEP) alkoxides, molar ratio TEOS:TEP of 1:0.1317, and which calcium source came from the same cold CaCl2 solution used to gelling the hybrids. Beads were synthesized by extruding mixtures, drop by drop, in CaCl2 solution. Were also investigated the behavior resulting upon soaking of hybrids into SBF. Samples were characterized by SEM, ATR-FTIR, TGA and XRD analysis. Results indicated decrease in spheres size with increase of glass and presence even pos-immersion, of Si, Ca and P associated to BG phase.