Na2O B2O3 SiO2 Research Articles

Development and characterization of low temperature metallic glazes in Na2O-B2O3-SiO2 (NBS) system

This paper presents the results of an investigation into crystal formation in NBS system for glaze with metallic appearance experimentally produced by embedding metallic substances as AgNO3, BaCl2, CuSO4 and CuCO3 and their characterizations. Composition of NBS was calculated by using Seger Method. According to the quantity of components, crystal phases were marked on Na2O-B2O3-SiO2 ternary diagrams. The amount of AgNO3 (2 wt%) was kept constant that other metallic substances (BaCl2, CuSO4 and CuCO3) were added in an amount of 5 wt% as had an impact on the mechanism of crystalline phase growth. These glaze compositions were applied over the surface of the commercial bodies and fired at 1040 °C, cooled to 750 °C and then reduced in the reductive atmosphere in order to obtain metallic layer on glaze surfaces for 20 min. These glaze layers characterized under mineralogical, microstructural and chemical points of view by means of X-Ray Diffraction (XRD), optical microscopy (OM), Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) and Ulltraviolet Visible Spectroscopy (UV–Vis) techniques. The results showed that silver and copper particles/crystals developed near/on the glaze surfaces creating multicolored metallic shine. Diffusion of metallic particles/crystals shown on the glazed layers as Ag and Cu followed by nucleation and growth in a reductive atmosphere.

Phase separated and porous glasses in the Na2O–B2O3–SiO2–Fe2O3 glass forming system

Phase separated and porous glasses in the Na2O–B2O3–SiO2–Fe2O3 glass forming system

Thermal conductivity of Na2O–B2O3–SiO2 melts

ABSTRACT Borosilicate glasses are candidate materials for the immobilization of high-level radioactive waste. The values of thermal conductivity of different borosilicate melts are thus indispensable information when optimizing the temperature distribution in a glass melting furnace. In this study, the thermal effusivity of Na2O–B2O3–SiO2 melts was measured using a front heating–front detection laser-flash method. The thermal conductivity, which can be obtained by combining the measured thermal effusivity with the specific heat capacity and density, was calculated using the least-squares method; the values for the Na2O–B2O3–SiO2 melts either slightly decreased linearly with increasing temperature or remained almost constant over the investigated temperature range. The values of thermal conductivity of the Na2O–B2O3–SiO2 melts were higher than those of B2O3–SiO2 melts and lower than those of CaO–B2O3–SiO2 melts. Furthermore, the thermal conductivity of the Na2O–B2O3–SiO2 melts was compared with those of the B2O3–SiO2 and CaO–B2O3–SiO2 samples.

The Influence of Glass Composition on Iodine Solubility

AbstractTwo glass series in the ternary systems K2O-B2O3-SiO2 (KBS) and Na2O-B2O3-SiO2 (NBS) were studied in order to identify the main factors influencing the solubility of iodine. We established that iodine incorporation is strongly linked to the bulk chemistry, i.e. the SiO2/(B2O3+SiO2) molar ratio, and to the physical properties of the glasses, and we assessed three different solubility limits. Iodine in Si-rich glasses has a low solubility (≤1 mol% I) regardless of the alkali ion present. On the contrary, in B-rich glasses, the solubility is five times higher than in Si-rich glasses for Na-glasses, and more than six times higher for K-glasses. The strong dependence of iodine solubility on the bulk chemistry is related to the adaptability of the glass network. Furthermore, our data suggest that iodine is stable with different redox states in the glasses here analyzed.

Effect of the relative volume of the conducting phase on the electroconductivity of glasses in the Na2O–B2O3–SiO2 system

The effect of the relative volume of the conducting phase on the electroconductivity of phase-separated glasses in the ternary system Na2O–B2O3–SiO2, whose compositions are on the same glass transition isotherm at 550°C, is investigated. It is demonstrated that the electroconductivity of phase-separated sodium borosilicate glasses does not depend on the relative volume of the conducting phase (within the limits from 0.3 to 0.9) under the condition that its composition invariable.

Structural study of Na2O-B2O3-SiO2 glasses from molecular simulations using a polarizable force field.

Sodium borosilicate glasses Na2O-B2O3-SiO2 (NBS) are complex systems from a structural point of view. Three main building units are present: tetrahedral SiO4 and BO4 (BIV) and triangular BO3 (BIII). One of the salient features of these compounds is the change of the BIII/BIV ratio with the alkali concentration, which is very difficult to capture in force fields-based molecular dynamics simulations. In this work, we develop a polarizable force field that is able to reproduce the boron coordination and more generally the structure of several NBS systems in the glass and in the melt. The parameters of the potential are fitted from density functional theory calculations only, in contrast with the existing empirical potentials for NBS systems. This ensures a strong improvement on the transferability of the parameters from one composition to another. Using this new force field, the structure of NBS systems is validated against neutron diffraction and nuclear magnetic resonance experiments. A special focus is given to the distribution of BIII/BIV with respect to the composition and the temperature.

Glass Ceramic Composite Protective Technological Coatings for Thermomechanical Processing of Intermetallic Alloys

Glass ceramic composite protective technological coatings were developed in the systems Na2O–B2O3–SiO2 and BaO–Al2O3–SiO2 for deformation of intermetallic alloys in the systems Ti–Al–Nb and Ni–Al–Co under isothermal conditions in air. The physical-chemical and technological properties of the coatings were investigated and the coatings were shown to be effective in application.

Synthesis, electrical and magnetic properties of sodium borosilicate glasses containing Co-ferrites nanoparticles

Co-ferrites nanoparticles that have been prepared by the co-precipitation method were added to sodium borosilicate (Na2O–B2O3–SiO2) glass matrix by the solid solution method and they were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and magnetization measurements. (XRD) revealed the formation of the Co-ferrite magnetic crystalline phase embedded in an amorphous matrix in all the samples. The investigated samples by (TEM) showed the formation of the cobalt ferrite nanoparticles with a spherical shape and highly monodispersed with an average size about 13nm. IR data revealed that the BO3 and BO4 are the main structural units of these samples network. IR spectra of the investigated samples showed the characteristic vibration bands of Co-ferrite. Composition and frequency dependent dielectric properties of the prepared samples were measured at room temperature in the frequency range 100–100kHz. The conductivity was found to increase with increasing cobalt ferrite content. The variations of conductivity and dielectric properties with frequency and composition were discussed. Magnetic hysteresis loops were traced at room temperature using VSM and values of saturation magnetization MS and coercive field HC were determined. The obtained results revealed that a ferrimagnetic behavior were observed and as Co-ferrite concentration increases the values of MS and HC increase from 2.84 to 8.79(emu/g) and from 88.4 to 736.3Oe, respectively.

The Effect of Aluminum Oxide Additives on the Phase Equilibrium in Borosilicate Systems and Crystallization of Borosilicate Melts

The effect of aluminum oxide additives on the phase relations in borosilicate glass based on the system Na2O–B2O3–SiO2 was investigated by means of the thermodynamic modeling. The phase equilibrium realized in this system was obtained using software package "FactSage" (version 6.4). The effect of aluminum oxide additives on the composition of the crystalline phases and residual melt formed during the cooling of borosilicate melts has been studied. The analysis of the diagrams has allowed establishing the regions of partial and complete melting of the substance depending on the chemical composition. The analysis allows determining the temperature of the melting process of a glassy matrix material. The combination of stable borate, silicate, mixed borosilicate, aluminosilicate and boroaluminate phases were determined for a wide range of compositions and temperatures. Boundaries of the regions formation of these phases depending on the composition and the temperature were determined. It allows assessing the prospects for absorption of elements in radioactive waste immobilization. The modeling of the crystallization melts formed in the studied systems was performed.

Effects of Nd Content on Structure and Chemical Durability of Zirconolite–Barium Borosilicate Glass‐Ceramics

The effects of Nd2O3 content (0–12 wt %) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass‐ceramics belonging to SiO2–B2O3–Na2O–BaO–CaO–TiO2–ZrO2–Nd2O3 system were studied. The results show that the glass‐ceramics with 2–6 wt% of Nd2O3 possess mainly zirconolite and titanite phases along with a small amount baddeleyite phase in the bulk. Calcium titanate appears when the Nd2O3 content increases to 8 wt%, and the amount of quadrate calcium titanate crystals increases with further increasing content of Nd2O3. For the glass‐ceramics with 6 wt% Nd2O3 (Nd‐6), Nd elements homogeneously distribute in zirconolite, titanite, and residual glass phases. There is a strong enrichment of Nd in calcium titanate crystals for the sample with 10 wt% Nd2O3. The viscosity of Nd‐6 glass is about 49 dPa·s at 1150°C. Moreover, Nd‐6 glass‐ceramics show the lower normalized leaching rates of B (LRB), Ca (LRCa), and Nd (LRNd) when compared to that of the sample with 8 wt% Nd2O3. After 42 days, LRB, LRCa, and LRNd of the Nd‐6 glass‐ceramics are about 6.8 × 10−3, 1.6 × 10−3, and 4.4 × 10−6 g·m−2·d−1, respectively.

Basic network structure of SiO2–B2O3–Na2O glasses from diffraction and reverse Monte Carlo simulation

Neutron- and high-energy synchrotron x-ray diffraction experiments have been performed on the (75−x)SiO2–xB2O3–25Na2O x = 5, 10, 15 and 20 mol% glasses. The structure factor has been measured over a broad momentum transfer range, between 0.4 and 22 Å−1. For data analyses and modelling the Fourier transformation and the reverse Monte Carlo simulation techniques have been applied. The partial atomic pair correlation functions, the nearest neighbour distances, coordination number distributions and average coordination number values and three-particle bond angle distributions have been revealed. The Si–O network proved to be highly stable consisting of SiO4 tetrahedral units with characteristic distances at rSi–O = 1.60 Å and rSi–Si = 3.0(5) Å. The behaviour of network forming boron atoms proved to be more complex. The first neighbour B–O distances show two distinct values at 1.30 Å and a characteristic peak at 1.5(5) Å and, both trigonal BO3 and tetrahedral BO4 units are present. The relative abundance of BO4 and BO3 units depend on the boron content, and with increasing boron content the number of BO4 is decreasing, while BO3 is increasing.

Structural Investigation of Na2O–B2O3–SiO2 Glasses Doped with NdF3

Structural Investigation of Na2O–B2O3–SiO2 Glasses Doped with NdF3

Plasticity, crack initiation and defect resistance in alkali-borosilicate glasses: From normal to anomalous behavior

We provide a comprehensive description of the defect tolerance of sodium-borosilicate glasses upon sharp contact loading. This is motivated by the key role which is taken by this particular glass system in a wide variety of applications, ranging from electronic substrates, display covers and substrates for biomedical imaging and sensing to, e.g., radioactive waste vitrification. The present report covers the mechanical properties of glasses in the Na2O–B2O3–SiO2 ternary over the broad range of compositions from pure SiO2 to binary sodium-borates, and crossing the regions of various commercially relevant specialty borosilicate glasses, such as the multi-component Duran-, Pyrex- and BK7-type compositions and typical soda-lime silicate glasses, which are also included in this study. In terms of structure, the considered glasses may be separated into two groups, that is, one series which contains only bridging oxygen atoms, and another series which is designed with an increasing number of non-bridging oxygen ions. Elastic moduli, Poisson ratio, hardness as well as creep and crack resistance were evaluated, as well as the contribution of densification to the overall amount of indentation deformation. Correlations between the mechanical properties and structural characteristics of near- and mid-range order are discussed, from which we obtain a mechanistic view at the molecular reactions which govern the overall deformation reaction and, ultimately, contact cracking.

The effect of borate and silicate structure on thermal conductivity in the molten Na2O–B2O3–SiO2 system

Thermal conductivity of molten Na2O–B2O3–SiO2 system was measured at various temperatures and for different compositions using the hot-wire method. It was observed that thermal conductivity decreases at higher temperatures. The calculated one-dimensional Debye temperature implies that the change of the phonon mean free path dominantly affects the thermal conductivity in the present measurements. Using solid state 11B and 29Si MAS NMR, the structure of the oxide system was confirmed. A conflicting effect of the R ratio (Na2O/B2O3) on thermal conductivity was observed. For R below 0.5, owing to the increase in 4-coordinated boron, thermal conductivity increases with increasing R ratio. However, for R above 0.5, thermal conductivity decreases with increasing R ratio as a result of the depolymerization of silicate networks and the increase in non-bridging oxygen (NBO). Finally, the effect of the K ratio (SiO2/B2O3) on thermal conductivity was considered. A higher K ratio causes an increase in thermal conductivity as a result of the increase in the total amount of the silicate structure and a more effective mixing between silicon and 4-coordinated boron.

Efficacy of a solution-based approach for making sodalite waste forms for an oxide reduction salt utilized in the reprocessing of used uranium oxide fuel

This paper describes the various approaches evaluated for making solution-derived sodalite with a LiCl–Li2O oxide reduction salt selected to dissolve used uranium oxide fuel so the uranium can be recovered and recycled. The approaches include modified sol–gel and solution-based synthesis processes. As-made products were mixed with 5 and 10mass% of a Na2O–B2O3–SiO2 glass binder and these, along with product without a binder, were heated using either a cold-press-and-sinter method or hot uniaxial pressing. The results demonstrate the limitation of sodalite yield due to the fast intermediate reactions between Na+ and Cl− to form halite in solution and Li2O and SiO2 to form lithium silicates (e.g., Li2SiO3 or Li2Si2O5) in the calcined and sintered pellets. The results show that pellets can be made with high sodalite fractions in the crystalline product (∼92mass%) and low porosities using a solution-based approach and this LiCl–Li2O salt but that the incorporation of Li into the sodalite is low.

Preparation and optical properties of sodium borosilicate glasses containing Sb nanoparticles

Sb nanoparticles have been successfully prepared from SbCl3 in sodium borosilicate (Na2O–B2O3–SiO2) glass matrix by sol–gel method, involving metallic sodium as sodium source, boric acid as boron source and SiO2 come from hydrolysis of tetraethoxysilane. The feasibility of process conditions were analyzed by using Fourier Transform Infrared (FT-IR), thermal gravimetric (TG), and nuclear magnetic resonance (NMR). X-ray diffraction (XRD) study revealed that the rhombohedral structure of metal Sb have formed in the glass. The particle was found to be spherical shaped and highly monodispersed with an average size of about 32.63nm as analyzed from transmission electron microscopy (TEM). The surface plasmon resonance (SPR) of Sb nanoparticle was studied from the UV–Vis absorption. The nonlinear optical properties were studied by using the Z-scan technique with a Ti:sapphire laser at 800nm. Results showed that the third-order optical nonlinear susceptibility χ(3) of the glass was determined to be 4.85×10−11esu.

Third-order optical nonlinearity of Na2O–B2O3–SiO2 glass doped with lead nanoparticles prepared by sol–gel method

Lead-nanoparticles-doped Na2O–B2O3–SiO2 (NBS) glass was prepared by sol–gel and atmosphere control methods. The formation mechanism and the microstructure of the specimens were investigated by differential thermal analysis and thermal gravimeter, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, and nitrogen adsorption measurements, respectively. The linear and nonlinear optical properties of the glass were analyzed by UV/VIS/NIR spectrophotometry and Z-scan technology. The results showed that the Pb nanoparticles in spherical shape with the average particle size about 18.9nm belong to cubic crystal system and have good crystallinity and dispersibility in the glass matrix as well as exhibit excellent nonlinear optical properties. The specimen has a high linear optical transmittance, and little absorption peaks appear in the examined wavelength range. The third-order optical nonlinear parameters calculated are γ of 1.67×10−16m2/W, β of 7.02×10−11m/W, and χ(3) of 2.61×10−17m2/W2.

Structural variation in gamma ray irradiated PbO–Na2O–B2O3–SiO2 glasses

Glasses with compositions xPbO–15Na2O-(70−x) B2O3–15SiO2 where x=5, 10, 15, 20 and 25 (mol%) have been prepared using the melt quenching technique. The structural properties of these glasses have been investigated using the FTIR spectroscopy. The effect of the presence of modifier PbO on the glass system is also studied. The FT-IR spectral investigation of these glasses exhibits characteristic vibrations of BO4 and BO3 units together with SiO4 as well as PbOn (n=4,6) groups. The gamma ray interaction of the present glass system in the dose range 0.1–60kGy is investigated. The results indicate that gamma rays result in the structural rearrangements in glass affecting the bridging and non bridging oxygens.

Interstitial sites for He incorporation in nuclear glasses and links to the structure: Results from numerical investigation

To investigate rare gases incorporation in glasses in relation with nuclear waste confinement, a wide range of borosilicate glasses have been studied by means of molecular dynamics simulations. The rare gases solubility is related to the number of interstitial sites accessible for these gases. To elucidate any relation between the number of interstitial sites and the glass composition, a large set of glass compositions that contain the most representative components in nuclear glasses is considered. We are mainly interested in SBN glasses (SiO2–B2O3–Na2O). A composition dependent force field was used to model the interactions between the atoms. Delaunay tessellation method was used to characterize the different topologies accessible for rare gases and analyze the interstitial sites distribution. In order to investigate irradiation effects by nuclear energy deposition on the number of interstitial sites accessible for He, disordered glasses representative of structures submitted to series of displacement cascades, were prepared by modifying the preparation procedure and the number of interstitial site changes were analyzed.

Raman spectroscopic study of structural changes induced by micro-indentation in low alkali borosilicate glasses

We report on the effect of micro-indentation on the local structure of glasses in the ternary borosilicate glass system Na2O–B2O3–SiO2. Indentation experiments were performed with loads ranging from 0.49 to 4.91N and for loading times of 10–30s in order to analyze the impact on the silicate and borate sub-networks in glasses ranging from pure SiO2 to binary Na2O–4B2O3, with a ratio of R=Na2O/B2O3<0.5. The Raman spectra reveal distinct changes in the glass structure, which can be correlated to different densification mechanisms occurring in the silicate and borate sub-networks, respectively. A clear trend from anomalous (densification-driven) deformation in silica-rich to normal (shear-driven) deformation behavior in alkali borate-rich glasses is observed.