Calcium Sodium Phosphate Research Articles

Biomimetic Approach for Enhanced Mechanical Properties and Stability of Self-Mineralized Calcium Phosphate Dibasic–Sodium Alginate–Gelatine Hydrogel as Bone Replacement and Structural Building Material

Mineralized materials are gaining increased interest recently in a number of fields, especially in bone tissue engineering as bone replacement materials as well as in the architecture-built environment as structural building materials. Until the moment, there has not been a unified sustainable approach that addresses this multi-scale application objective by developing a self-mineralized material with minimum consumption of materials and processes. Thus, in the current study, a hydrogel developed from sodium alginate, gelatine, and calcium phosphate dibasic (CPDB) was optimized in terms of rheological properties and mineralization capacity through the formation of hydroxyapatite crystals. The hydrogel composition process adopted a three-stage, thermally induced chemical cross-linking to achieve a stable and enhanced hydrogel. The 6% CPDB-modified SA–gelatine hydrogel achieved the best rheological properties in terms of elasticity and hardness. Different concentrations of epigallocatechin gallate were tested as well as a rheological enhancer to optimize the hydrogel and to boost its anti-microbial properties. However, the results from the addition of EPGCG were not considered significant; thus, the 6% CPDB-modified SA–gelatine hydrogel was further tested for mineralization by incubation in various media, without and with cells, for 7 and 14 days, respectively, using scanning electron microscopy. The results revealed significantly enhanced mineralization of the hydrogel by forming hydroxyapatite platelets of the air-incubated hydrogel (without cells) in non-sterile conditions, exhibiting antimicrobial properties as well. Similarly, the air-incubated bioink with osteosarcoma SaOs-2 cells exhibited dense mineralized topology with hydroxyapatite crystals in the form of faceted spheres. Finally, the FBS-incubated hydrogel and FBS-incubated bioink, incubated for 7 and 14 days, respectively, exhibited less densely mineralized topology and less distribution of the hydroxyapatite crystals. The degradation rate of the hydrogel and bioink incubated in FBS after 14 days was determined by the increase in dimensions of the 3D-printed samples, which was between 5 to 20%, with increase in the bioink samples dimensions in comparison to their dimensions post cross-linking. Meanwhile, after 14 days, the hydrogel and bioink samples incubated in air exhibited shrinkage: a 2% decrease in the dimensions of the 3D-printed samples in comparison to their dimensions post cross-linking. The results prove the capacity of the developed hydrogel in achieving mineralized material with anti-microbial properties and a slow-to-moderate degradation rate for application in bone tissue engineering as well as in the built environment as a structural material using a sustainable approach.

Immobilization Strategies for L-Asparaginase from Ganoderma australe GPC191: Impact on Enzyme Activity, Stability, and Reusability

L-asparaginase has garnered significant attention for its potential therapeutic applications in cancer treatment, as well as its role in mitigating acrylamide in the food industry. However, the widespread implementation of free L-asparaginase in industrial processes has faced substantial obstacles, primarily attributed to issues such as reduced stability, high production costs, and limited recyclability. In order to address these challenges and fully unleash the capabilities of L-asparaginase, the current investigation was centered on the exploration of L-asparaginase immobilization derived from Ganoderma australe GPC191. The various immobilization matrices were assessed, including gelatin, agarose, agar, and combinations thereof with sodium alginate, carboxymethyl cellulose, and calcium phosphate. These matrices were evaluated based on critical parameters such as enzyme activity after immobilization, loading efficiency, recyclability, and storage stability. Among the diverse matrices considered, the alginate-gelatin-calcium phosphate capsules emerged as the best, exhibiting remarkable characteristics such as an enzyme activity of immobilized L-asparaginase at 60.43 U/mL, an impressive loading efficiency of 94.82%, sustained recyclability with 51% stability even after 16 cycles, and a storage efficiency only reducing to 27% at six months. These outstanding attributes position them as a promising choice for industrial applications. The encouraging outcomes of this investigation could be further refined through research into the effects of altering the concentrations of matrix components, shedding light on how these adjustments influence enzyme properties and their interactions with the external environment.

Alkaline-Activation Technique to Produce Low-Temperature Sintering Activated-HAp Ceramic

The fabrication of hydroxyapatite (HAp) ceramics prepared by existing conventional sintering requires high-temperature sintering of 1250 °C to 1300 °C. In this paper, the activated metakaolin (MK)/HAp specimens were prepared from varied mix design inputs, which were varied solid mixtures (different amounts of MK loading in HAp) and liquid-to-solid (L/S) ratios, before being pressed and sintered at 900 °C. Phase analysis, thermal analysis, surface morphology, and tensile strength of the specimens were investigated to study the influences of the Al, Si, Fe, Na, and K composition on the formation of the hydroxyapatite phase and its tensile strength. XRD analysis results show the formation of different phases was obtained from the different mix design inputs HAp (hexagonal and monoclinic), calcium phosphate, sodium calcium phosphate silicate and calcium hydrogen phosphate hydrate. Interestingly, the specimen with the addition of 30 g MK prepared at a 1.25 L/S ratio showed the formation of a monoclinic hydroxyapatite phase, resulting in the highest diametrical tensile strength of 12.52 MPa. Moreover, the increment in the MK amount in the specimens promotes better densification when sintered at 900 °C, which was highlighted in the microstructure study. This may be attributed to the Fe2O3, Na2O, and K2O contents in the MK and alkaline activator, which acted as a self-fluxing agent and contributed to the lower sintering temperature. Therefore, the research revealed that the addition of MK in the activated-HAp system could achieve a stable hydroxyapatite phase and better tensile strength at a low sintering temperature.

A new iron recovery and dephosphorization approach from high‑phosphorus oolitic iron ore via oxidation roasting-gas-based reduction and magnetic separation process

Deep dephosphorization of high‑phosphorus oolitic iron ore (HPOIO) is extremely difficult because of its refractory characteristics. A new approach for simultaneous iron recovery and dephosphorization from HPOIO by oxidation roasting–gas-based reduction (ORGR) and magnetic separation process was developed. The underlying mechanism was investigated using thermodynamic calculations, X-ray diffraction (XRD), and scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS). The results showed that the powdery reduced iron produced contained 91.37% iron and 0.14% phosphorus, and the iron recovery was 92.81%, which is an ideal for steelmaking. The addition of Na2CO3 formed nepheline, which promoted the formation and coarsening of hematite during oxidation. Concurrently, Na2CO3 reacted with the phosphorus in the iron minerals and fluorapatite to form sodium calcium phosphate, which was embedded in hematite with a simple relationship. Hematite was subsequently converted into metallic iron, sodium calcium phosphate was not reduced, and metallic iron and phosphorus were separated efficiently.

One step to stabilize calcium sodium phosphate crystals acting as photocatalysts embedded in a glass matrix

Unstable calcium sodium phosphate (CaNaPO4) in aqueous solution can be stabilized and shows photocatalytic activity in a glass matrix. This research utilizes one-step melt quenching to prepare glass ceramics with stable CaNaPO4 crystals in a glass material. The photocatalytic activity of the CaNaPO4 glass ceramic was investigated by monitoring methyl orange degradation with the addition of H2O2. Notably, the CaNaPO4 glass ceramic demonstrates the high-efficiency photocatalytic degradation of methyl orange (MO) under UV irradiation. The CaNaPO4 glass ceramic could be reused several times. After 8 cycles, the catalyst was still stable and effective in decomposing 100% of methyl orange within 5 h/cycle. In addition, the solid phase photocatalytic activity of the CaNaPO4 glass ceramic was examined by bleaching adsorbed MB under UV light for 25 h. It could also inhibit the growth of E. coli bacteria after UV irradiation for 20 min. Therefore, CaNaPO4 embedded glass ceramic might be an alternative photocatalytic material for wastewater treatment.

Composite Ceramics Based on Pastes Including Tricalcium Phosphate and an Aqueous Solution of Sodium Silicate

Preceramic samples were prepared from pastes based on the aqueous solution of sodium silicate and tricalcium phosphate with a given molar ratio of (Na2O · 2,87SiO2)aq/Ca3(PO4)2 = 1:3 after drying at 24 °C and then 60 °C for 24 h. It established the dependence of the plastic strength of these pastes on both time and temperature and the possibility of using them for extrusion 3D printing. The phase composition of ceramic was represented by unreacted β-TCP (β-Ca3(PO4)2) and β-rhenanite (β-NaCaPO4) after heat treatment at 500 °C. Further, an increase in temperature up to 700 °C led to the appearing phase of silicon dioxide (SiO2) and up to 900 °C, of sodium calcium phosphate (Na3Ca6(PO4)5). After heat-treatment at 1100 °C, ceramic samples consisted of the β-TCP (β-Ca3(PO4)2), sodium calcium phosphate (Na3Ca6(PO4)5), silicon dioxide (SiO2) and β-wollastonite (β-CaSiO3). The bending and compressive strength of the ceramics rose with increasing temperature from ≈6.8 MPa and ≈31.1 MPa at 500 °C to ≈10.6 MPa and ≈43.5 MPa at 1100 °C. The obtained composite ceramics consisted of biocompatible phases that are widely studied in the literature and may be used as a biomaterial for the treatment of bone tissue defects.

Corrosion behavior of aluminum alloy in simulated nuclear accident environments regarding the chemical effects in GSI-191

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

Sodium doped hydroxyapatite: Synthesis, characterization and zeta potential studies

Sodium-doped Hydroxyapatite (HA) powders were successfully synthesized by a facile mechano-synthetic route. The effect of Na addition on the properties of HA was studied. XRD results confirmed that the major phase that is formed in all the doped powders is of apatite whereas a new phase of calcium sodium phosphate was formed at higher sodium (Na) concentrations. The crystallite size of the Na doped HA powders showed an increase from 27.7 nm (Pure HA) to 38.4 nm (NaHA4). FTIR results confirmed the presence of phosphate groups in the synthesized powders which became prominent at higher Na concentrations. Zeta potential studies revealed a negative potential for all the powders. FESEM micrographs ddepicted a change in the particle shape from spherical to oblong at higher Na concentrations.

Influence of Reinforcement Oxides on Structural and Mechanical Properties of Glass-Ceramics: A Review Article

This review studied the mechanical behaviors of Glass ceramics (GC) based on the Al2O3/SiO2 system. Glass ceramics are great interest due to their wide variety of applications, which have the ability to fulfil the recent demands of advanced mechanical, optical and biomedical applications. Glass-ceramics are typically heat-stable and have greater mechanical features than glasses. In addition, mechanical properties can be customized to provide variable volume fractions of crystalline phases by regulating nucleation and growth of the crystalline phases. The distribution of these crystalline phases in the glass matrix increases the consistency of the material and, in comparison, effectively limits the growth of cracks. The crystallization process resulted in substantial improvements in micro-hardness and density values such as sodium calcium phosphate (Na4Ca(PO3)6 and calcium pyrophosphate (β-Ca2P2O7) had sufficient properties for bone grafts and dental applications. This article outlines recent developments in the field of doping Oxides as reinforced with SiO2-Al2O3-based Glass- ceramics, to enhance the mechanical properties of Glass-ceramics combination. The research focused on the mechanical and the tribological behaviour of Biomedical, Electronics applications and selection of fabrication methods.

Microalgae biofilm cultured in nutrient-rich water as a tool for the phycoremediation of petroleum-contaminated water

This study aimed at studying the phycoremediation of petroleum-contaminated water using microalgae biofilm cultured in nutrient-rich water. Microalgae biofilm was grown in a photobioreactor containing water rich in calcium nitrate, manganese chloride, sodium potassium tartrate, calcium phosphate, and ammonium sulfate. Petroleum contaminated water was poured into a photobioreactor, and the substrate containing microalgae biofilm was inserted into the photobioreactor and allowed for eight weeks for biofilm formation. Physicochemical parameters (pH, turbidity, conductivity, sulfate, alkalinity, chloride, TDS, TSS, nitrate, salinity, iron, potassium, phosphate, chlorine, chromium, magnesium, zinc, COD, BOD, and total petroleum hydrocarbon (TPH) of the petroleum contaminated water before and after treatment were determined. The microalgae biofilm used for the treatment was characterized before and after treatment using a Scanning Electron Microscope, X-Ray Fluorescence, and Fourier-transform infrared spectroscopy. The phytochemical constituent of the microalgae biofilm was also determined before and after treatment of the petroleum-contaminated water. The result obtained shows highest removal efficiency of physicochemical parameters (turbidity (81%), conductivity (51.2), sulfate (17.5%), alkalinity 28.4%), chloride (14.6%), TDS (7.9), TSS (26%), nitrate (33%), salinity (23.4), iron (16%), potassium (22%), phosphate (28.2%), chlorine (14%), chromium (13.6%), magnesium (30.3%), zinc (40.5%), COD (8%), BOD (16.7%) and total petroleum hydrocarbon (15%)). The microalgae's characterization shows microalgae biofilm's ability to adsorb pollutants in petroleum-contaminated water due to the presence of microspores and larger surface area of the cells of the microalgae forming the biofilm or due to the absorption efficiency of the extracellular polymeric substances (EPS). The analysis of the microalgae biofilm's phytochemical parameters shows the involvement of the chemicals components in pollutants degradation and antioxidant response of the microalgae to counteract the oxidative effect resulting from the exposure of the microalgae to the contaminated water. NOVELTY STATEMENT This is the first study that attempts the phycoremediation of petroleum contaminated water using microalgae biofilm. The reduction efficiency of the parameters treated in this study is very low compared to that reported in the literature but increases with the retention day. This low reduction efficiency is attributed to the slow assimilation of organic and inorganic pollutants due to the initial growth condition. This study is the first to re-affirm that microalgae biofilm can phycoremediate petroleum-contaminated water by adsorption and assimilation due to the presence of microspores and a larger surface area the cells of the microalgae forming the biofilm or the extracellular polymetric surface covering the biofilm. Several studies have reported that phytochemicals present in microalgae play an antioxidant response role to prevent the microalgae from oxidative damage resulting from water pollution. However, this study is the first to strongly link phytochemicals to the enhancement of pollutants degradation and adsorption by microalgae biofilm.

Fabrication of bioactive novel scaffold by solid‐state reaction sintering for bone regeneration

In this work we present a new type of scaffold obtained by solid-state reaction, simultaneous sintering of a mixture of precursor oxides, carbonates, and organic substances, the latter used for pore generation. Having variable local composition, exhibits excellent overall physicochemical and bioactivity response. Open porosity is about 50%-60% and its permeability 10-11 m2 . X-ray diffraction exhibits the presence of a sodium-calcium silicate and sodium-calcium phosphate crystalline phases. Additionally, by mechanical compression tests the range of failure stress obtained for the scaffolds was 0.3-1.1MPa. The bioactivity and dissolution rate of the scaffolds were evaluated by in vitro tests. After 1week soaking in simulated body fluid, the formation of a continuous hydroxyapatite layer, which does not differentiate local compositions, was observed. Our results from cell culture tests clearly indicate that during hydroxyapatite layer formation, scaffolds do not liberate any cytotoxic substances. Moreover, cells seeded in the hydroxyapatite-covered scaffolds grew better than the control.

Non-linear dissolution mechanisms of sodium calcium phosphate glasses as a function of pH in various aqueous media

Phosphate glasses for bioresorbable implants display dissolution rates that vary significantly with composition, however currently their mechanisms of dissolution are not well understood. Based on this systematic study we present new insights into these mechanisms. Two-stage dissolution was observed, with time dependence initially parabolic and later linear, and a two-stage model was developed to describe this behaviour. Dissolution was accelerated by lower Ca concentration in the glass, and lower pH in the dissolution medium. A new dissolution mechanism is proposed, involving an initial stage where diffusion-controlled formation of a conversion layer occurs. Once the conversion layer is stabilised, layer dissolution reactions become rate-limiting. Under this mechanism the transition time is sensitive to the nature of the conversion layer and solution conditions. These results reveal the dependence of P2O5–CaO–Na2O glass dissolution on solution pH, and provide new insight into the dissolution mechanisms, particularly regarding the transition between the two dissolution stages.

Cerium-doped calcium phosphates precipitated on bacterial cellulose platform by mineralization

Bacterial cellulose (BC) membranes biosynthesized by Komagataeibacter rhaeticus AF1 strain were used as a platform for precipitating cerium-doped calcium phosphates (Ce:CaP), which were synthetized by successive soaking of BC membranes in solutions containing Ca2+, PO43− and Ce3+ precursor ions. After obtaining the as-prepared composites, BC-Ce:CaP was submitted to a thermal treatment at 600 °C for 3 h, and Ce:CaP was characterized by scanning electronic microscopy (SEM), energy dispersive X-ray spectrometry (EDX), thermogravimetric analysis (TG), derivative thermogravimetric analysis (DTG) and X-ray diffraction (XRD). Ce:CaP presented hydroxyapatite, chlorapatite and buchwaldite (sodium calcium phosphate) phases and revealed a trabecular structure composed per nanowires with interconnected pores. Furthermore, BC-Ce:CaP and Ce:CaP show cell viability and has been suggested for use as a mineral scaffold.

Enhanced mechanical and biocompatible properties of strontium ions doped mesoporous bioactive glass

Very low (≤0.2%) strontium (Sr) ion doped mesoporous (45S5) bioactive glasses (BG) were synthesized by sol-gel technique and calcination without using polymers (porogens), mould or other additives. The phases and their functional groups were confirmed by the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) and FT-Raman spectroscopy respectively. Sodium calcium phosphate silicate [(Na0.11Ca0.89) (P0.11Si0.89O3)] which is essential for assisting the self-repair process of enamel was formed along with sodium calcium silicate (Na2Ca2Si3O9) phase. Doping of Sr ions (0.2 wt %) enhances the pore volume (96%) and surface area (108%) compared to pristine. Further, interconnected network structures are created exhibiting controlled and sustained drug release (58% in 720 h). The mechanical strength of the Sr doped BG samples increased significantly. The compressive strength of sample (Sr = 0.2 and 0.5 wt %) were 8.1 ± 0.5 and 11.2 ± 0.5 MPa with respective percentage increase of 440 and 647% compared to BG. The thermal stability and zeta potential of the Sr doped BG samples increase with considerable variation in the particle size when compared to the pristine. The cell viability and proliferation were also significantly enhanced by the doping of Sr ions which tailor the surface properties as well. The overall results robustly demonstrate for the first time that the very low doping of Sr ions (≤0.2%) in BG, play a major role in engineering the properties viz., mechanical, surface, drug release and cell proliferation making them suitable for multifunctional biomedical applications.

Characterization and Investigation of Antibacterial Activity of Injectable Hydroxyapatite-Alginate Hydrogel

Introduction: Bone replacement materials used for void filling and healing the bone injuries with antibacterial characteristics is of interest to many researchers. The main inorganic material in human and animal bones makes calcium phosphate suitable to interact with neighboring bones and enhances the healing process. A few drawbacks of using neat Ca/P powder such as low solubility and its brittle nature makes it difficult to manipulate. Therefore, the composition of these bio-ceramics with biopolymers makes an ideal injectable mixture with proper mechanical properties. In this study a hybrid composite of sodium alginate (SA) and calcium phosphate was prepared and its antibacterial characteristics were investigated. Materials and Methods: In this study, hydrogel composites of SA/brushite and SA/hydroxyapatite (HA) were fabricated with different fabrication methods as well as the final compositions. The filler properties of these hybrid composites were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Also, to determine the antibacterial effects, the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were assessed on two strands of microorganisms including Escherichia coli and Streptococcus agalactiae which are known as causative agents for biofilm formation on implant surfaces. Results: Findings reveal that calcium phosphate in the form of brushite in combination with alginate and carboxy-methyl-cellulose (CMC) has intrinsic antibacterial efficiency in concentrations lower than 250 μg/mL. Conclusions: The composition of SA/brushite with CMC carrier is a promising injectable filler with antibacterial properties which could be used to treat bone injuries and orthopedic applications.

Stereolithographic 3D Printing of Bioceramic Scaffolds of a Given Shape and Architecture for Bone Tissue Regeneration

Abstract—A standard series of ceramic scaffolds for bone tissue regeneration with Kelvin architecture was developed, providing matrix water permeability not less than 900 Darcy and relative rigidity of matrices of not more than 0.2. The possibility of producing bioceramic scaffolds is shown using stereolithographic 3D printing of light-cured slurries containing a mixed calcium sodium phosphate Ca2.5Na(PO4)2 composition. A production technology of bioceramic scaffolds is developed and tested, including the development of photocurable slurries; 3D printing modes are also worked out, as well as conditions of heat treatment of printed models and sintering. The proposed methods of stereolithography formation followed by heat treatment of printed models make it possible to produce ceramic scaffolds with lateral resolution no worse than 50 μm and 50 μm layering. The dimensions of the bioceramic scaffold differ from the reference dimensions of the initial model by no more than 10%; the degree of macroporosity is not less than 70% and the pore size is 500 μm. It is shown that the obtained bioceramic scaffolds are compatible with the human fibroblast cell culture, are not cytotoxic, do not contain components inhibiting fibroblast adhesion, spreading, and proliferation, and can be used in tissue engineering.

Characterisation of ashes from waste biomass power plants and phosphorus recovery

Biowastes, such as meat and bone meal (MBM), and poultry litter (PL), are used as energy sources for industrial combustion in the UK. However, the biomass ashes remaining after combustion, which contain nutrients such as phosphorus, are landfilled rather than utilised. To promote their utilisation, biomass ashes from industries were characterised in terms of their elemental and mineral compositions, phosphorus extractability, and pH-dependent leachability. These ashes were highly alkaline (pH as high as 13), and rich in calcium and phosphorus. The P bio-availabilities in the ash evaluated by Olsen's extraction were low. Hydroxyapatite and potassium sodium calcium phosphate were identified by X-ray powder diffraction (XRD) as the major phases in the MBM and PL ashes, respectively. The leaching of P, Ca, and many other elements was pH dependent, with considerable increase in leaching below about pH 6. P recovery by acid dissolution (e.g., with H2SO4) seems feasible and promising; the optimized acid consumption for ~90% P recovery could be as low as 3.2–5.3 mol H+/mol P.

Network connectivity and dissolution properties of sodium calcium phosphate glasses

Glasses of xCaO∙(80-x)P2O5·20Na2O system (0 ≤ x ≤ 30% mol %) with constant Na2O content were studied in order to evidence both structural and dissolution properties determined by CaO addition. Transparent vitreous samples were obtained in the investigated composition range. Thermal analysis evidenced the increase of both crystallisation and melting temperatures with CaO content. The relative mass loss of samples in simulated body fluid progressively increased with the extent of P2O5 substitution by CaO. The dissolution properties could be explained in relation with the structural changes concerning the PO4 units connectivity as pointed out by DTA and FTIR analysis.

The effect of silica additive on the structural and luminescence properties of Eu3+/Tb3+ co-doped metaphosphate glasses

In this paper, we investigate the effect of silica additive on the structural and luminescence properties of Eu3+ and Eu3+/Tb3+co-doped sodium-calcium phosphate glasses. Eu3+ doped phosphate glasses have been prepared using melt-quenching technique and characterized through X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier Transform Infrared (FTIR), Raman spectroscopy, ultraviolet–visible (UV–Vis) and luminescence measurements at room temperature. The incorporation of SiO2 led to an increase of glass transition temperature (Tg), indicating an improvement of glass network rigidity. This result was correlated with FTIR and Raman investigations which revealed the occurrence of more hydration-resistant POSi bonds. An intense red luminescence has been observed due to 5D0 → 7F2 transition of Eu3+ ions in these glasses. The luminescence spectra for Eu3+/Tb3+ co-doped phosphate glasses were then recorded with various Eu3+:Tb3+ molar ratio. Dependence of luminescence lifetimes on the increase of Eu3+: Tb3+ molar ratio was investigated. It was observed that the energy transfer process occurs from Tb3+ to Eu3+ in the studied glasses. Our results show that a tuneable color is achieved when Eu3+: Tb3+ molar ratio changed. The variation of the excitation wavelength can also tune the luminescence spectra of the new phosphate glasses.

Synthesis, characterization and applications of low temperature melting glasses belonging to P2O5CaO Na2O system

Abstract This study details the relationship between the structure, chemical composition and thermal properties of a series of calcium sodium phosphate glasses belonging to xP2O5-yCaO-(100−x−y)Na2O system, which have been prepared by melt-quenching method. The glass compositions were limited by fixing the P2O5 content (x) to 40, 45, 50, 55 and 60 mol%, and varying the CaO mol% (y) at 10, 15, 20, 25, 30 mol%. Glass transition (Tg) and melting temperatures (Tm) show a clear relationship with composition. The polymerization of the glass structure increases the higher the content of P2O5 leading to an increase in Tg and Tm temperatures. Higher contents of calcium improve the phosphate network strength increasing Tg and Tm temperatures. Sodium ions, displaying lower charge-to-size ratio than calcium ions, decrease the phosphorous condensation reducing the Tg and Tm temperatures of glasses. The results obtained in this investigation show the feasibility to develop extremely low melting calcium sodium phosphate glasses with P2O5 content of 45 mol%. Those results laid the foundation of employing these calcium sodium phosphate glasses as amorphous low melting temperature materials for further applications involving: a) melting temperature adjustment, such as fire-retardant additive in polymer composites; b) nanoparticle binder, due to its low melting temperature, nanoparticles can be safely embedded into this glass avoiding thermal coalescence. Examples of such applications are described in this work.