Substitution Of Na2O Research Articles

Structural and optical modifications in sodium zinc-based phosphate glass upon substitution of Na2O with Fe2O3

Structural and optical modifications in sodium zinc-based phosphate glass upon substitution of Na2O with Fe2O3

Tailored Bioactive Glass Coating: Navigating Devitrification Toward a Superior Implant Performance.

The development of well-adherent, amorphous, and bioactive glass coatings for metallic implants remains a critical challenge in biomedical engineering. Traditional bioactive glasses are susceptible to crystallization and exhibit a thermal expansion mismatch with implant materials. This study introduces a novel approach to overcome these limitations by employing systematic Na2O substitution with CaO in borosilicate glasses. In-depth structural analysis (MD simulations, Raman spectroscopy, and NMR) reveals a denser network with smaller silicate rings, enhancing thermal stability, reducing thermal expansion, and influencing dissolution kinetics. This tailored composition exhibited optimal bioactivity (in vitro formation of bone-like apatite within 3 days) and a coefficient of thermal expansion closely matching Ti-6Al-4V, a widely used implant material. Furthermore, a consolidation process, meticulously designed with insights from crystallization kinetics and the viscosity-temperature relationship, yielded a crack-free, amorphous coating on Ti-6Al-4V substrates. This novel coating demonstrates excellent cytocompatibility and strong antibacterial action, suggesting superior clinical potential compared with existing technologies.

Effect of Sodium Oxide on Structure of Lanthanum Aluminosilicate Glass

Rare earth (RE) aluminosilicate glasses exhibit several favorable chemical, mechanical and thermal properties. As such, they are considered to be model systems for long-half-life actinides and are candidate containment materials for long-term immobilization of radioactive wastes. The aim of the present study was to investigate the effect of the substitution of sodium oxide on the glass transition temperature and structure of lanthanum aluminosilicate glasses. The primary objective was to elucidate the relationship between the substitution of Na2O for La2O3 on the Tg reduction and structural characteristics of lanthanum aluminosilicate glass, including identifying changes in the main Qn species and local environments of Si and Al. The structure of SiO2–Al2O3–La2O3–Na2O glasses has not been studied previously, and, thus, this investigation is the first to assess the structural changes occurring when La2O3 is substituted by Na2O. Three glasses were prepared with general composition (mol.%): 55SiO2–25Al2O3–20M2On (M = La or Na; n = 3 or 1). Glass G1 contains 20 mol.% La2O3; in G2, 15 mol.% of La2O3 was substituted by 15 mol.% Na2O; and Glass G3 contains 20 mol.% Na2O. The glasses were characterized by DSC to determine glass transition temperatures. As expected, as Na is substituted for La, Tg decreases substantially. Structural studies were carried out by FTIR spectroscopy, 29Si, and 27Al MAS NMR. As Na is substituted for La in these aluminosilicate glasses, the main goals that were achieved were the identification of Qn species and also changes in the local environments of Si and Al: {QnSi(mAl)} and {QnAl(mSi)}.

Effect of the iron content on the thermal and dielectric relaxation process of sodium zinc-phosphate quaternary glassy systems

To explore the consequence of Na2O substitution by Fe2O3 on the physical, thermal and dielectric properties of zinc-phosphate-based glassy systems, a series of samples with chemical compositions of 25ZnO-40P2O5-(35-x)Na2O-xFe2O3 where, (x = 0.10, 0.15, 0.20, 0.25) have been prepared by melt quenching technique. The well-known Archimedes principle is deployed to measure the value of densities of the materials. DSC thermographs specify that the glass transition temperature (Tg) declines with the incorporation of Fe2O3 content. While thermal stability increases upon adding the Fe2O3 content. The dielectric constant (ε/) and dielectric loss (ε//) rise with an increase in temperature and fall as frequency rises sharply. The obtained relaxation time exhibits Arrhenius behaviour, and the dynamic conductivity relaxation process is not of the Debye type because the Kohlrausch stretching exponent (β) value is not equal to unity. According to the scaled electric modulus (complex) spectra, composition instead of temperature affects the dynamic conductivity relaxation mechanism.

Effect of systematic substitution of Na2O for SiO2 on devitrification and bioactivity of sol-gel derived 69.5SiO2-24.5CaO-6P2O5 ceramics

Addition of Na2O to SiO2–CaO–P2O5 glass-ceramics significantly impacts in-vivo dissolution and structural network modifications. However, achieving a vitreous state in sol-gel derived quaternary oxide powders, like the 45S5 bioglass containing high amounts of Na2O, is challenging. Synthesis of (69.5-x)SiO2-24..5CaO-6P2O5-xNa2O (x = 0, 2, 4, 8, 12, 16, 20, and 24.5 wt.%) ceramic powders has been carried out followed by heat-treatment between 500 °C and 700 °C. Structural characterization revealed that the vitreous state could be stabilized for Na2O content up-to 12wt.%. For higher Na2O content, the network transformed to a glass-ceramic state with the crystallization of combeite phase. In-vitro tests exhibited hydroxyapatite layer formation (Ca/P = 1.67) on all samples in simulated body fluid, regardless of structure. Samples were non-toxic to MG-63 osteoblast cells. The devitrification, bioactivity and associate properties of the quaternary system as a function of Na2O content is discussed with respect to envisaged biomedical applications.

Design, synthesis and structural properties of borate glasses: Towards an alkali-free bioactive glass

Glasses in the system (14-x) Na2O-(54+x) B2O3–22CaO-8MgO-2P2O5 with 0 ≤ x ≤ 14 mol%, have been prepared by the classic method, fast quenching of high-temperature melts. Multiples techniques were used to investigate their physical and structural properties such as X-ray diffraction, Density measurements, Differential scanning calorimetry, Infrared spectroscopy, Raman spectroscopy, and Isothermal heat treatment. The results found by Raman and Infrared spectroscopy show that the addition of boron oxide in different proportion and the progressive reduction of sodium oxide affect clearly the glass structure, wherewith the total elimination of Na2O the glass network exhibit the formation of an interconnected large cluster (pentaborate) at the detriment of the isolated unit containing non-bridging oxygen, thus promoting groups with four coordinated boron. The physical parameters and thermal analysis confirm the structural results found revealing an increase in the oxygen packing density and glass transition temperature from 510 °C to 640 °C indicating compactly packed structure and a reinforcement of the glass network. The isothermal treatment confirms the role of boron by maintaining the vitreous aspect until (800 °C) for the alkali-free glass, in addition to a much higher thermal stability. The bioactivity test was achieved by immersion glass samples in simulated body fluids solution (SBF) at 37 °C, these latter within a few days reveals the growth of the hydroxyapatite phase confirmed by X-ray diffraction, FT-IR, and scanning electron microscope. Also, the conversion process was proved with the increase in pH and the weight loss values as well as the consumption of Ca and P concentration in simulated body fluids solution. However, the kinetics of the reaction decreases with the substitution of Na2O with B2O3 in the glass system which is quite related to the creation of more interconnected bonds and less non-bridging oxygens. Thus the properties found of the alkali-free glass in correlation with the formation of hydroxyapatite layer indicate a potential glass for tissue engineering application.

Volatilization of fluorine in a CaO–SiO2–CaF2‐based system with the substitution of Na2O with K2O

AbstractCuspidine‐based systems are used to control the crystallization in mold fluxes, which is enabled by CaF2 additions. However, excess CaF2 increases the corrosion of casting machines. Therefore, Na2O and K2O are added to the mold flux system to ensure an optimized crystallization and lubrication ability of the flux with the CaF2 content. This study investigated the effect of substituting Na2O with K2O on the volatilization of fluorine in a CaO–SiO2–CaF2‐based slag system at high temperatures. The substitution of Na2O with K2O was performed at 5 mol% intervals. The volatilization was observed by thermogravimetric analysis under several isothermal conditions. The mass loss was measured at a heating rate of 5, 10, and 20 K/min. As the temperature increased, the volatilization of the mixed samples increased. The activation energy was calculated using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. A kinetic analysis of the volatilization of fluorine was conducted using the calculated parameters and several known kinetic models. Consequently, the volatilization of the Na‐rich sample was controlled by chemical reactions and that of the K‐rich sample was identified to be controlled by a phase‐boundary‐controlled reaction. These results suggest that the addition of mixed alkali oxide promote the volatilization during the early stages of the reaction. From the post‐experimental composition analyses, the remaining Na and K in the samples suggested a different mechanism for the Na and K volatilization. The volatilization of Na increased with time, whereas K volatilized easily during the beginning of the reaction.

Influence of K and Mg substitutions on the synthesis and the properties of CaO-MgO-SiO2/Na2O, P2O5, CaF2 bioactive glasses

Novel glasses in CaO-MgO-SiO2 system with Na2O, P2O5, and CaF2 additives were produced by melting/quenching technique. The influence of K2O and MgO on glass structure, the thermal properties (of major importance for evaluating the crystallization mechanism), and properties related to their potential in biomedicine (bioactivity, machinability), was investigated. According to Raman spectra, K2O for Na2O substitution favors the formation of Q0 and Q1 silicate units at the expense of Q2 and Q3 ones, whereas substitution of MgO for CaO increases the Q2 and Q3 units at the expense of Q1 ones. The presence of K2O caused the increase of Tg and of the crystallization temperature as well as of the Ea of crystallization. A weaker influence on the above magnitudes was recorded in glasses with MgO substitution. The produced glasses are generally prone to 3-dimensional crystallization, display bioactivity in SBF testing, and manifest positive value of the machinability parameter n.

Structure – Properties study of Na2O–CaO–PbO–P2O5 metaphosphate glasses

Sodium-calcium-lead phosphate glasses having a mol.% composition (25-z/2)Na2O-(25-z/2)CaO-zPbO-50P2O5 (0 ≤ z ≤ 50) were prepared by using the melt-quench technique. Some physical properties have been measured and their structure has been studied by IR and Raman spectroscopies. Density of the glass increases linearly with the substitution of Na2O and CaO by PbO. Glass molar volume vary slightly with the substitution, and a non-linear increase of PbO molar volume and a non-linear decrease of P2O5, Na2O and CaO ones is observed. Glass transition temperature increases non-linearly with PbO substitution. FTIR and Raman spectra reveal the formation of P–O–Pb bonds, which replace P–O–Na and P–O–Ca bonds, and no modification of the network polymerization is observed with substitution by PbO. However, Raman spectra exhibit shoulder's peak due to (PO3)2- terminal groups, which seemingly results from disproportionation of species in the glass melts. PbO is assumed to play a network modifier role like Na2O and CaO, but it reticulates the phosphate network, which causes an increase of Tg and a slight effect on molar volume.

DC and AC Conductivity, Biosolubility and Thermal Properties of Mg-Doped Na2O-CaO-P2O5 Glasses.

Bioactive glasses have recently been extensively used to replace, regenerate, and repair hard tissues in the human body because of their ability to bond with living tissue. In this work, the effects of replacing Na2O with MgO on the electrical, biosolubility, and thermal properties of the target glass 10Na2O–60P2O5–30CaO (in mol%) were investigated. The electrical properties of the glasses were studied with the impedance spectroscopy technique. At 473 K, DC conductivity values decreased from 4.21 × 10−11 to 4.21 × 10−12 S cm−1 after complete substitution of MgO for Na2O. All samples had a similar activation energy of the DC conduction process ~1.27 eV. Conduction mechanisms were found to be due to hop of ions: Na+, Mg2+, and probable H+. FTIR analysis showed that, as the Mg content increased, the Q2 unit (PO2−) shifted towards higher wavenumbers. The proportion of Q3 unit (P2O5) decreased in the glass structure. This confirmed that the replacement of Na+ by Mg2+ was accompanied by concurrent polymerization of the calcium–phosphate glass network. The biosolubility test in the phosphate-buffered saline solution showed that the magnesium addition enhanced the biosolubility properties of Na2O–CaO–P2O5 glasses by increasing their dissolution rate and supporting forming CaP-rich layers on the surface. The glass transition temperature increased, and thermal stability decreased substantially upon substitution of Na2O by MgO.

Effect of Na2O/PbO substitution on physical and optical properties of Er3+-doped tellurite glasses

Er3+-doped tellurite glasses with chemical compositions (in mol%): 55TeO2-35ZnO-(5+x)PbO-2Bi2O3-(2-x)Na2O-Er2O3 with x = 0; 0.5; 1.0; 1.5 and 2.0) were synthesized and explored their physical and optical properties. Density and refractive index were measured at room temperature and other physical properties such as ionic packing ratio, field strength, polaron radius, internuclear distance and molar refraction were derived. It was found that Na2O substitution by PbO causes both refractive index and glass density increase.

A comprehensive investigation on the role of PbO in the structural and radiation shielding attribute of P2O5–CaO–Na2O–K2O–PbO glass system

This study presents the synthesis, physical, structural and gamma-ray shielding characteristics of 40P2O5–20CaO–(30−x)Na2O−10K2O–xPbO (x = 0, 5, 10, 15, 20 mol%) glasses. The glass samples coded as PbCKNP1, PbCKNP2, PbCKNP3, PbCKNP4, and PbCKNP5 were prepared using the melt quench method. Na2O substitution by PbO influenced the molar volume and mass density of the glasses. Structural analysis of the glasses using the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed amorphous structure. The photon shielding parameters of the glasses examined via the Monte Carlo simulation code (MCNP-5) revealed that the glasses' shielding ability improved as PbO content increased. The highest simulated linear attenuation coefficient (LAC) achieved at 0.015 MeV increased from 21.46 to 159.07 cm−1 as the PbO concentration increased from 0 and 20 mol%. The LAC for all fabricated glass samples showed an exponential reduction trend with gamma photon energy. Based on the simulated LAC values, calculated mass attenuation coefficient (MAC), half-value layer (HVL), transmission factor (TF), and radiation shielding capacity (RSC), PbCKNP5 possessed the best gamma-ray protection ability among the investigated glasses. Furthermore, the calculated shielding parameters of the PbCKNP glasses showed that they possess a good potential for radiation shielding applications.

Structures of fluoride containing aluminosilicate low activity nuclear waste glasses: A molecular dynamics simulations study

Fluorine and other halides commonly exist in nuclear waste forms, and due to their volatile nature, halide retention poses an issue affecting waste loading during vitrification. The compositional effect on fluorine incorporation in aluminosilicate glasses is investigated through molecular dynamics simulations. Oxygen and fluorine coordination numbers around glass former and modifier cations, bond angle distributions, and medium range structure features such as Qn distributions, ring size distributions and neutron diffraction structure factors were calculated. It was found that fluorine has higher preference to bond to Ca2+ than to Na+, both in the melt and the glass, and there is no Si-F bond formation in the glass but they do exist in the melt. Consequently, CaO for Na2O substitution can be an effective way to help fluorine retention without significantly changing the glass chemistry. These results thus provide insights on fluorine incorporation in the aluminosilicate nuclear waste glasses and the strategy on how to improve fluorine retention both in the glass and the melt.

Physical properties and conductivity relaxation processes in sodium sulfo-borophosphate glasses

Many physical properties of a sodium-borophosphate glass system (BPSx) having the starting composition (30H3BO3 + xNa2SO4 + (60 − 2x) NaH2PO4 + 10ZnO) were detremined. It was found that the glass density ρ, the transition temperature Tg, and the optical gap energy decrease whereas the molar volume and Urbach ▵E energy increases with the substitution of Na2O by Na2SO4.The analysis of the evolution of the complex dielectric permittivity ε* and the complex electric modulus M* with temperature and composition of the glass indicates that the dielectric loss is dominated by ionic conduction, and the relaxation processes are non-Debye type. The evolution of the Kohlrausch–Williams–Watts (KWW) exponent β, estimated from the imaginary part of the electric modulus indicates that the investigated glass behaves as an intermediate elastic system as compared to flexible and stressed rigid phase. The obtained values of the decoupling index are of the same order of magnitude as observed for fast-ion conducting glasses.From the analysis of the experimental data, we may suggest that the glass sample BPS4 is the more thermally stable and has the highest ionic conductivity since it has the highest dielectric constant favorable for the dissociation of sodium salt.

Barium polyphosphate glasses, from structure to thermochemistry

In order to understand the effects of BaO addition on the structure and thermochemistry of polyphosphate glasses, a series of vitreous compositions having the formula (100-x)NaPO3-xBaO was investigated with x ranging from 0 to 25 mol%. The glasses were synthesized using the melt quenching technique and reveal a limit of vitrification of 25 mol% of BaO. Fourier Transform Infrared Spectroscopy and 31P Magic Angle Spinning Nuclear Magnetic Resonance show the depolymerization of the metaphosphate chains, leading to Q1 and Q2 phosphate groups as main structural units together with a smaller average chain length. The substitution of Na2O and P2O5 by BaO increases the density, glass transition and crystallization temperatures indicating the shrinking and reticulation of the polyphosphate network. The enhancement of the chemical durability was related to the strengthening of the glasses towards water attack and the low mobility of the Ba2+ cations. Finally, the microcalorimetric investigations, pursued in 4.5 wt% H3PO4 solution, show a decrease of the dissolution enthalpy. This trend was correlated with the structural modification within the vitreous network and the reduction of the chemical degradability of the glasses.

Substitutional effect of Na2O with K2O on the viscosity and structure of CaO‐SiO2‐CaF2‐based mold flux systems

AbstractThe effect of the substitution of Na2O with K2O on the viscosity and structure of molten CaO‐SiO2‐CaF2‐based mold fluxes containing alkali‐oxides at high temperatures has been studied. The CaO/SiO2 mass ratio (C/S) and CaF2 were fixed at 0.8 and 10 mass pct., respectively. The total alkali‐oxide was fixed at 20 mass pct. By systematically substituting the Na2O with K2O, the K2O/(Na2O + K2O) mass ratio was modified between 0.0 and 1.0. Using the rotating spindle method to measure the viscosity at high temperatures, the viscosity was found to increase with higher K2O/(Na2O + K2O). From the slope of the temperature dependence of the viscosity, an apparent activation energy was calculated and increased with higher K2O/(Na2O + K2O), from 96 to 154 kJ/mol, due to the cation size effect on the resistance to shearing. Using Raman spectroscopy of as‐quenched fluxes, the mole fraction of Q3 was found to increase, while the mole fractions of Q2 and Q0 decreased with higher K2O/(Na2O + K2O). The nonbridged oxygen per silicon cation (NBO/Si) decreased from 1.97 to 1.58 with increasing K2O/(Na2O + K2O), suggesting greater complexity of the flux structure with higher K2O/(Na2O + K2O), resulting in a higher viscosity.

Effects of alkali metal oxides on crystallization behavior and acid corrosion resistance of cordierite-based glass-ceramics

MgO-Al2O3-SiO2-TiO2 glass-ceramics with 3mol% alkali metal oxides were prepared, and the 3mol% alkali metal oxides were induced by 3mol% Na2O only, 1.5mol% Na2O+1.5mol% Li2O, and 1.5mol% Na2O+1.5mol% K2O, respectively. Effects of alkali metal oxides on the crystallization behavior and acid corrosion resistance of the MgO-Al2O3-SiO2-TiO2 glass-ceramics were investigated. The results showed that μ-cordierite precipitated in the glass matrix firstly, and it changed into α-cordierite with the crystallization temperature increasing. Using K2O substitution of Na2O hindered the precipitation of cordierite, while the addition of Li2O promoted the precipitation of μ-cordierite at low temperatures. When the main crystalline phase was μ-cordierite, the acid resistance of the glass-ceramics was significantly improved compared with the base glass. With the main crystalline phase changing from μ-cordierite to α-cordierite, the acid resistance of the glass-ceramics became worse, which was related to the honeycomb structure of α-cordierite. When 1.5mol% Na2O was replaced by Li2O, the glass samples crystallized at 880°C showed the optimum acid resistance with the minimum weight loss ~0.096%.

Fine structure, mechanical characteristics and mid-range order in xZnO–yNa2O–(1-x-y)SiO2 glasses

The differentiation between the behavior of Zn2+ and Na+ cations in silicate network is shaded by the lack of characteristic infrared or Raman bands belonging to the modes involving the zinc- or sodium-oxygen bonds. It was shown in this study that the stepwise substitution of Na2O for ZnO in the xZnO–yNa2O–(1-x-y)SiO2 glasses with keeping approximately the same SiO2 content causes the high-frequency shift of the Raman-active boson peak (BP) that is the decrease of the correlation length in structural glass heterogeneities. Intercomparison of this trend with variations of the measured structural strength and microhardness of the glasses under consideration afforded ground to suggestion of a possible dual role of Zn2+ ion as either glass-modifier or glass former in specific compositions of zinc-alkali-silicate glasses.

Effect of Na<sub>2</sub>O and K<sub>2</sub>O on the Solubility and Chemical Properties of P<sub>2</sub>O<sub>5</sub>-CaO-Na<sub>2</sub>O-K<sub>2</sub>O-Al<sub>2</sub>O<sub>3</sub> Glass

The effect addition of Na2O on the solubility properties of phosphate glass of the composition, 45P2O5-18CaO-xNa2O-(34-x)K2O-6Al2O3, where x = 0,5,10,15 and 20 wt. %. has been studied. Glass transition temperature (Tg) of glass samples, weight loss and pH of the immersion solution were measured. The Tg value of the phosphate glass also decreased with the incorporation of Na2O up to 10 wt. % and increased with the incorporation of 15 and 20 wt. %. These results indicates that the solubility and Tg value of phosphate glass were highly influence by the glass composition. The substitution of Na2O to the phosphate glass system with the present of K2O has decrease the solubility of phosphate glass. The released of phosphate and calcium ion seem to decrease with the increasing of Na2O content in the glass composition.

The effect of K2O on the microstructure of Na2O-CaO-P2O5-SiO2 based ceramic system

In present study ceramic based material having composition (SiO2-Na2O-CaO-K2O-P2O5) was synthesized by solid state method. The influence of sintering temperature at 900°C and partial substitution of Na2O with K2O in SiO2-P2O5-Na2O–CaO system on thermal and structural properties of system was studied by TGA-DSC, ourier transform IR, X-Ray Diffraction and Scanning electron Microscopy respectively. In all the thermally treated ceramic samples, solid solution of sodium calcium silicate Na2Ca3Si6O16, Combeite Na2Ca2Si3O9, Wollastonite, were known as main crystalline phases identified. The result showed that addition of K2O stabilized the samples thermally, decreased the crystallization kinetics. The thermal stability for samples were observed in 800°C–1000°C region.