Sodium Oxide Content Research Articles

Examination, conservation and analysis of a gilded Egyptian bronze Osiris

A heavily corroded Egyptian bronze figurine of the god Osiris was examined and shown to have been originally gilt with gold leaf and inlaid with blue glass. Detailed formal comparison between this Osiris figure and the known corpus of bronze and stone sculpture leads to the inference that the statuette dates to the time between the Third Intermediate Period and the fourth century BC, with a greater probability of originating from the Third Intermediate Period through to the 26th Dynasty, or even possibly as late as the fourth century on the basis of stylistic similarities. An extensive corrosion crust of atacamite and chalconatronite completely obscures inlaid glass decoration, found during the investigation, together with remnants of a gilded surface. Analysis of the glass by electron microprobe showed a composition consistent with early Egyptian blue glass with high sodium oxide and low potassium oxide content. The solid cast bronze is a leaded tin bronze, and the gold is a gold foil applied to the bronze surface, originally alternating in decoration with the blue glass. The chalconatronite and atacamite patina appear to be closely associated in the development of the unusual but extensive chalconatronite crust that now covers part of the surface, as a natural corrosion process in this case, not derived from subsequent conservation treatment. The loss of the light blue corrosion crust was prevented by consolidation with Paraloid B72, as examination over several months showed no sign of continued chemical instability.

Vaporization and thermodynamic properties of melts in the Na2O-B2O3-SiO2 system

The vapor composition, partial pressures of the molecular species of the vapor, and activities of the melt components in the Na2O–B2O3–SiO2 system at temperatures of 1300 and 1350 K are studied using the Knudsen effusion mass-spectrometric method. It is shown that the vapor composition depends on the concentration ratio of sodium and boron oxides in the condensed phase. When the content of boron oxide is larger than the content of sodium oxide in the condensed phase, the vapor contains NaBO2, (NaBO2)2, and B2O3 molecules. At the ratio [Na2O] : [B2O3] > 1, the gas phase contains atomic sodium. The activities obtained for NaBO2 and B2O3 indicate substantial negative deviations from an ideal behavior.

A Study of the Acid–Base Properties of Melts in the Na2O–B2O3–SiO2 System: III. Composition Joins with a Constant Sodium Oxide Content from 40 to 50 mol %

Three joins in the Na2O–B2O3–SiO2 system at constant Na2O contents of 40, 45, and 50 mol % are studied by the high-temperature method of determining oxygen ion exponents pO for oxide melts. It is found that, unlike the melts with a lower sodium oxide content, the basicity of the studied melts increases when changing over from the pseudobinary silicate system to the sodium borate system. The acid–base properties of ternary melts are simulated under the assumption that their basicity is determined by the interaction in pseudobinary systems. It is shown that the basicity of the melts under investigation is governed, to a large extent, by the dissociation of structural–chemical groupings of the sodium metasilicate–sodium metaborate composition.

A study of the acid-base properties of melts in the Na2O-B2O3-SiO2 system: II. Composition joins with sodium oxide contents of 25, 30, and 35 mol %

The exponent of oxygen ion activity pO = \( - \log a_o ^{2 - } \) for melts in the Na2O–B2O3–SiO2 system along the composition joins with constant sodium oxide contents of 25, 30, and 35 mol % is studied by an electromotive force (emf) technique at 950°C. Measurements are performed using two variants of the technique of determining pO, namely, in high-temperature salt solutions of oxide systems in KF and with a salt bridge between two oxide melts. It is shown that the basicity of melts increases with an increase in the Na2O content at a constant concentration ratio of glass-forming oxides. The acid–base properties of sodium borosilicate melts are simulated under the assumption of acid–base interaction between the components. It is found that the basicity of the studied melts along the composition joins with constant sodium oxide contents of 30 and 35 mol % is governed primarily by the acid–base interaction in Na2O–B2O3 and Na2O–SiO2 binary systems and, to a lesser extent as compared to low-alkali composition joins (below 20 mol % Na2O), by the formation of Na2O · B2O3 · 2SiO2 and Na2O · B2O3 · 6SiO2 ternary compounds.

Enthalpies of Chromium Oxide Solution in Soda Lime Borosilicate Glass Systems

Chromium oxide (Cr2O3) solubility was measured in soda lime borosilicate glass from 1400 to 1500 K. The temperature dependence of the solubility increased with increased sodium oxide concentration. The enthalpies of solution for the equilibrium phases were calculated from the solubility data in the temperature range from 1400 to 1500 K. The enthalpy of fusion for Cr2O3 at 1450 K was calculated to be 108.0 kJ·mol−1. This value was less than our measured values for enthalpy of solution, 111.0 ± 0.5 and 158.4 ± 0.3 kJ·mol−1, indicating that all enthalpies of mixing were positive; that is, the mixing process was endothermic. This characterized the interaction between solute and solvent as repulsive.

Information on the absolute length scales of ion transport processes in glasses from electrical conductivity and tracer diffusion data

We show that absolute values for the time-dependent mean-square displacement of mobile ions in glasses can be obtained from a combined analysis of electrical conductivity and tracer diffusion data. By applying this method to sodium germanate glasses of different compositions, we find that the distances the ions cover in characteristic stages of the transport process increase considerably with decreasing sodium oxide content. At low sodium oxide contents, we observe a linear relation between the transport distances and the interionic separation distances, while this relation is lost at high sodium oxide contents. The same is found to be true for other alkali ion conducting glassy systems. The analysis of this effect is important for discriminating between the influence of the network structure and of the interionic Coulomb interactions on the ion dynamics.

Light hydrocracking of vacuum distillate

Technology developed previously at VNII NP [3, 4] for two-stage hydrocracking at a pressure of 15 MPa, with the feed hydrotreatod in the first stage (a process aimed at obtaining motor fuels), has not yet been commercialized. The selection of a particular hydrocracking technology will be determined by the end result desired, the quality of the feedstock, and the properties of the catalyst that is used. The process design is influenced considerably by the catalyst type and composition and the charging conditions. As shown by an analysis of the literature and patent data, catalyst compositions for hydrocracking generally contain ultrastable Y zeolites in the REE or H form [5 - 7]. Zeolites in the REE form are more resistant to the action of catalyst poisons present in the feed (nitrogen bases, heavy metals, etc.). Such zeolites are used extensively in manufacturing catalysts for cracking untreated or partially hydrotreated feeds. Zeolites in the H form are less resistant to catalyst poisons, but they are more active in cracking reactions. Hence they are used in manufacturing catalysts for hydrocracking feedstocks that have been thoroughly treated. The content of sodium oxide in the zeolite must not exceed 1%, and should be less than 0.5%. Therefore, in obtaining hydrocracking catalysts, Y zeolite in the REE form is recommended as the most resistant to poisoning. The functional properties of hydrocracking catalysts are determined to a great degree by the zeolite type and content. In the first application of the domestic multifunctional zeolitic catalyst GK-8, in single-stage cracking at 15 MPa and 405-410~ it was found that the process could yield up to 50% jet fuel fractions or up to 70% winter-grade diesel fuel. However, this catalyst did not come into any extensive use, owing to problems in catalyst manufacture. Another commercial catalyst, GKO-1, for which the commercial manufacturing technology has been worked out at the Omsknefteorgsintez Production Association, has a high hydrodesulfurizing activity but is insufficiently stable, owing TABLE 1

Influence of sodium oxide content on bioactive glass properties.

The rate of in vivo degradation and level of bioactivity of bioactive glasses are composition dependent [1]. By altering bioactive glass composition, the rate of resorption can be controlled. The network connectivity of a glass can be used to predict various physical properties of the glass including its solubility and, hence, its bioactivity [2]. Glass solubility increases as network connectivity is reduced. Glasses in the soda-lime phosphosilicate system were studied. The initial choice of composition was based on phosphate content and low network connectivity. A systematic substitution of calcium oxide for sodium oxide on a molar basis was made in order to examine the influence of sodium oxide content on the glass properties while keeping the network connectivity constant. The glass transition temperature and the peak crystallization temperature were seen to decrease linearly with increasing sodium oxide content. Thermal expansion coefficient and glass density were also seen to be related to sodium oxide content. Preliminary in vitro biocompatibility studies revealed that the glasses of higher sodium oxide content were associated with a cytotoxic response. The measurement of media pH indicated that this cytotoxic effect was due to ion exchange reactions at the glass surface.

Effect of basicity on redox equilibria in sodium silicate melts: An in situ electrochemical investigation

Redox ratios of chromium and antimony were directly measured at 1000°C in sodium silicate melts by electrochemical methods. The redox ratios were found to increase while increasing the sodium oxide content, i.e. the liquid basicity. It was shown that the logarithm of the redox ratio is a linear function of the logarithm of the sodium oxide activity. Our results differ systematically from those obtained on quenched samples. The results are discussed in the light of a thermodynamic model considering activities of molecular species. We suggest that, when dissolved in silicate melts, multivalent ions form oxocomplexes which are not fully discrete species because non-bridging oxygens can intervene in their coordination sphere. We also concluded that there are rapid exchanges of oxygen atoms between the oxocomplexes and the solvent.

Two opposite effects of sodium on elastic constants of silicate binary glasses

(1 - x)SiO 2- xNa 2O glasses have been studied by Brillouin scattering when sodium oxide molar concentration x, varies in the range 0.05 < x < 0.44. Non-linear dependence of elastic constants on sodium oxide concentration is shown unambiguously for the first time and the compressive elastic constant C 11 experienced a non-monotonic behaviour with a minimum value around x = 0.15. These results are compared with those obtained previously in the case of other alkali silicate glasses (Li, K). The variations of elastic constants of these glasses with the alkali metal nature and concentration are discussed on the basis of relations with the molar density of silicon atoms and the force constants between modifiers and non-bridging oxygens.

Intermediate Range Order in Sodium Tellurite Glasses

ABSTRACTInformation about the spatial distribution of sodium cations in sodium tellurite glasses is obtained from the decay rate of sodium spin echoes. The spin echoes decay due to the magnetic dipole coupling between sodium nuclei, with each pair contributing to the rate in proportion to 1/r6, where r is the distance between the pair. The experiment is used to probe the sodium distributions in sodium tellurite glasses as a function of sodium oxide content, and the resulting distance distributions are interpreted by comparison with model distributions. At low sodium contents the distribution is similar to that of a random model in which the sodium ions are constrained to be no closer than a minimum cut-off distance. At higher contents the distributions deviate significantly from the random model, suggesting the onset of medium range order in the distribution of sodium ions. This order is most pronounced at 20% sodium oxide content, the composition at which this glass has been claimed to have maximum stability against devitrification.

In situ electrochemical investigation of copper in binary sodium silicate melts at 1000 °C

The influence of the melt composition on the redox ratio of copper in binary sodium silicates at 1000 °C was determined by means of in situ electrochemical methods. The redox ratio was calculated from the currents measured by Repetitive Multi-Pulse Chronoamperometry. It appears that the redox ratio does not depend on the total copper concentration over the range 0,25 to 1 wt% Cu. However, the proportion of copper(II) was found to increase with increasing basicity, ie with increasing the sodium oxide content. We deduced from a model based on the formation of pure ionic oxocomplexes that the coordination number of the Cu(II) oxocomplex is greater than that of the Cu(I) oxocomplex. The difference between the coordination numbers, which is calculated from the experimental results is equal to 0.56. The fractional number is quite far from the integer that would indicate the occurrence of well defined oxocomplexes of copper.

Raw Materials for Alumina Ceramics

A brief presentation is made of the raw materials for alumina ceramics. The important source is the alumina trihydrate resulting from the Bayer process. Purification of the Bayer aluminate liquor to minimise organics, iron oxide and silica, reduction of sodium oxide content, special conditions of precipitation and calcination and fine grinding of the calcined material lead to the production of various grades of alumina. Other processes involve acidification of the aluminate liquor followed by drying and calcination or treatment of aluminium amalgam with water to precipitate aluminium hydroxide. Typical properties and applications of alumina ceramics are discussed. A survey of the world scene is made and the situation in India is briefly reviewed. The importance of introducing collaborative efforts to accelerate activities in this field in India is stressed.

Ultrasonic investigation and infrared absorption of some sodium borate glasses

Ultrasonic velocities and absorption measurements in sodium borate glasses containing Na2O have been made using the pulse echo technique at 4, 5 and 6 MHz. Results showed an increase in velocity as the sodium oxide content (mol%) increased. The ultrasonic absorption results showed the presence of very high and well-defined peak which shifts its position to lower temperatures with increasing frequency. This suggests some sort of relaxation process and the activation energy of this process increased with increasing Na2O concentration (mol%). The infrared absorption spectra of sodium borate glasses confirmed the results obtained by ultrasonic investigations.

Diffusion of sodium ions in borosilicate glasses by molecular dynamics method

Molecular dynamics simulations of borosilicate glasses with different sodium oxide content has been carried out. The generated structure indicates that the major number of oxygen atoms introduced as Na2O consumes in the borate network to convert the BO3 triangles to BO4 tetrahedra. The formation of nonbridging oxygen ions in the silica site occurs during the formation of BO4 tetrahedra with low rate. At higher concentrations of Na2O, the NBO's increases abruptly. The self diffusion of sodium ions depends essentially on the temperature, composition (number of Na+ ions) and the rate of cooling. The phase separation mechanism in borosilicate glasses can be detected by MD simulation since the environment of the B−O, Si−O and B−O−Si can be easily reached.

Distributions of sodium oxide concentration and refractive index in ion-exchanged glass

Diffusion equations with the diffusion coefficient depending on concentration were solved by the finite difference method. Distributions of sodium oxide concentration and refractive index calculated for an ion-exchanged glass are compared with results measured by electron microprobe analysis and interference microscopy respectively. Even if the interdiffusion coefficients of the ions in the glass vary over long ion exchange times, the error between calculation and measurement can be made as small as possible by selecting an interdiffusion coefficient for a suitable ion exchange time to calculate the concentration distribution in the glass ion-exchanged for a different time.

NMR study of structure of sodium boroaluminate glass at high sodium content

Nuclear magnetic resonance has been used to study the structure of sodium boroluminate (NABAL) glasses with varying sodium oxide content. A structural change is found at high sodium oxide content which is in the region where abrupt changes in glass properties have been found by different workers. A structural model is suggested based on the results of computer simulation and measurements of activation energy. The model is suggestive in explaining the abrupt changes observed in different kinds of measurements, such as conductivity.

Sintering Temperature of Porous Glass and Transition Temperature of High Silica Glass

High silica porous glasses were prepared by varying acid treatment of phase-separated soda borosilicate glass and one of them was impregnated by sodium nitrate solutions. The porous glasses were heat treated to form nonporous glasses and the end point of their thermal shrinkage (sintering temperature) was determined. The glass transition temperature was determined for NaNO3-impregnated and sintered glasses. The glass transition temperature was linearly related to the sintering temperature and decreased linearly with increasing logarithm of sodium oxide content. ΔTg/ΔlogC, where Tg is the glass transition temperature and C is the content of water (-0.1wt%) or sodium oxide (0.1-3wt%) of nonporous glasses, was determined. Sodium oxide lowered the glass transition temperature more strongly than water. ΔTg/ΔlogC was calculated for pure silica glass and some silicate glasses from the data available in the literatures and compared with the results of the present work. ΔTg/ΔlogC for water decreased and that for sodium oxide increased with decreasing glass transition temperature.

The X-Ray Fluorescence Spectroscopy of Inorganic Solids. VII. The Fe Kβ1,3 Energy Shifts in Oxide Glasses

Abstract The Fe Kβ1,3 energy shifts in the binary sodium borate, silicate, and phosphate glasses containing small amounts of the iron ion were examined. The Fe Kβ1,3 energy decreases with an increase in the sodium oxide content in the borate and silicate glasses. The data are in accordance with those of previous studies that the coordination number of the Fe(III) ion is four in the borate and silicate glasses and six in the phosphate glasses. The structure of the coordination sphere around the Fe(III) ion in the borate glasses was also discussed.

Optical absorption spectra of pulse irradiated oxide glasses.

The pulse radiolysis technique was applied to sodium metaphosphate, alkali borate and Nabal glasses. In the sodium metaphosphate glass a transient peak around 2.0eV was observed. The transient peak disappears after 5μs following irradiation. In sodium borate glasses the intensity of the early stage spectra increases with increasing sodium oxide content. By resolving the observed spectra into Gaussian peaks, the relation between the intensity of the individual peak and composition was discussed. Generally, the composition dependence of the early stage spectra was similar to that of the permanent spectra by X-ray irradiation, reflecting the structure of borate glasses. In sodium glasses is also observed a tansient peak around 1.6eV whose intensity increases with increasing basicity. On the other hand in the glasses containing aluminium oxide the presence of the center which is associated with aluminium ion was deduced, whose life time is perhaps to be order of μs to ms.