Increase In Na2O Concentration Research Articles

Electronic and optical properties of Na2O doped P2O5-TeO2− CoO-ZnO glasses

The phospho-tellurite glasses, (P2O5)0.25-(TeO2)0.5-x-(CoO)0.1-(ZnO)0.15-(Na2O)x ; x = 0.15, 0.20, 0.25, 0.30 and 0.35 were prepared by melt quenching and their non-crystalline nature confirmed through XRD. Density is found decreased and molar volume increased with increase of Na2O concentration and they behaved opposite to each other. The physical parameters such as transition metal ion density, mean distance between TMIs, small polaron radius, oxygen packing density and field strength were estimated. DC conductivity was measured by following two probe method in the temperature range 303K – 633K. High temperature conductivity is explained by Mott’s small polaron hopping (SPH) model and low temperature conductivity by Mott’s VRH model. Both conductivity and activation energy are found to be increasing with Na2O content. Density of states at Fermi level are found to be of the order of 1021 to 1024 eV−1 cm−3. UV-Vis spectra were recorded for the wavelength range 200-800 nm. Optical band gap (direct and indirect) except for x=0.20 is found increased, urbach energy and refractive indexes are found decreased with Na2O concentration. Various optical parameters such as molar polarizibility, metallization criterion, reflection loss, electronic polarizability, optical transmission coefficient, dielectric constant and optical dielectric constant have been determined.

The potential usage of waste ferrochrome slag in alkali-activated mixes

Ferrochrome slag (FCS) is a by-product of the stainless-steel industry which is mostly discarded in landfills without being efficiently utilized. The production of industrial solid wastes like FCS has been increasing for several decades and escalating the environmental risks associated with them. To address this issue, this study concentrated on the usage of FCS as a partial substitution for blast furnace slag (BS) in manufacturing alkali-activated paste and mortar. BS was replaced with FCS in varying proportions up to 30% (wt.%) and activated with varying Na2O dosages. The fresh, physical, mechanical, and microstructural properties were investigated. The test outcomes indicated that FCS incorporation was beneficial in improving the flowability by consistently reducing both yield stress and plastic viscosity more than 54% and 70%, respectively, when FCS replacement was 30%. Furthermore, the inclusion of FCS alleviated the rapid setting issue of BS-based alkali-activated systems by delaying the setting times. The increase in Na2O concentration remarkably decreased the water absorption, open porosity and capillary sorptivity of the mortars, while no adverse effect was observed on the physical properties of the mortars with the FCS addition. The compressive strength of mortars increased between 152% and 254% when Na2O dosage was increased from 4% to 8%, while strength was mostly preserved with the addition of FCS. The higher Si/Al atomic ratio and the higher pH values was found favorable for the higher compressive strength of the mixes. The primary reaction product was found as C-A-S-H gels, whereas FCS addition increased the crystalline phases and favored the formation of M-A-S-H gels.

Formulating eco-friendly geopolymer foam concrete by alkali-activation of ground brick waste

This study investigates ground brick waste powder as a primary precursor to develop eco-friendly geopolymer foam concrete (BGFCs) using a chemical foaming method. The effect of alkali content on the reaction kinetics of brick powder is studied and correlated with the properties of BGFCs. The reaction rates and the formation of crystalline phases of BGFCs were identified by Fourier Transform Infrared Spectroscopy and X-Ray Diffraction test method, respectively. It is found that increasing the alkali content (Na2O) in the mix has significantly enhanced the reaction kinetics of brick powder with the rapid formation of geopolymer gel in the matrix. This has resulted in the enhancement of mechanical properties and rapid setting in BGFCs. For instance, the increase in Na2O concentration from 1:40 to 1:12 has increased the compressive strength of BGFC by 245%. The corresponding initial setting times were reduced from 315 min to 140 min. The rapid setting of geopolymer mixture has resulted in a fine, regular, and homogenous distribution of air voids in the BGFCs. Finally, carbon emission calculations were conducted to assess the environmental impacts of developed BGFCs and compared with Ordinary Portland cement (OPC) foamed concrete. It is found that the developed BGFCs could significantly reduce the carbon emission up to 60% compared to their OPC counterparts.

Effect of Na2O on Properties, Structure, and Crystallization of CaO–Al2O3‐Based Mold Fluxes

This article investigates the effect of Na2O on melting properties, viscosity, flux structure, crystallization behavior, and heat transfer of CaO–Al2O3‐based mold fluxes with Na2O concentration varied from 3.5 to 12.1 mass pct. With the increase in Na2O content, both melting temperature and viscosity at a given temperature decrease. The Raman spectroscopy indicates that increasing the Na2O content decreases the degree of polymerization, in line with the decrease in viscosity. Flux crystallization is studied using single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results show that flux crystallization tendency is enhanced with the increase in Na2O content. This increase is more significant when the Na2O content changes from 9.1 to 12.1 mass pct. X‐ray diffraction analysis of the fluxes heat treated at different temperatures reveals that the crystal precipitates vary with the flux composition and temperature. Heat transfer measurement using the IR emitter technique (IET) shows that the increase in Na2O concentration impedes the heat transfer, in line with the increased crystallinity of the fluxes.

Desilication of concentrated alkali solution by novel desilication reagent calcium hydroferrocarbonate: Part II. Desilication reaction and kinetics

Using a hydroferite desilication reagent, calcium hydroferrocarbonate (CHFC), the desilication reaction in concentrated caustic aluminate solution was studied. The results indicated that process parameters, such as temperature, Na2O concentration, molar ratio of Na2O to Al2O3, and initial mass ratio of alumina to silica (mass ratio of alumina to silica), significantly affected the reaction efficiency. The reaction kinetics were found to exhibit a reaction order of 1.3 ± 0.15 for desilication; the empirical rate constant k was 64.4 ± 2.4 and the apparent activation energy Ea was 25.8 ± 3.2 kJ/Mol, which was much lower than the values obtained by adding Ca(OH)2, C3AH6(calcium Hydroaluminate, 3CaO·A12O3·CaCl2·6H2O), and Friedel's salt (3CaO·A12O3·CaCl2·10H2O). In the desilication process, silica reacts with CHFC on the surface to form hydroandradite and calcium aluminum iron hydroxide. Subsequently, with an increase in Na2O concentration and temperature, hydroandradite and calcium aluminum iron hydroxide dehydrated to form calcium aluminum iron silicate and Fe(OH)3

Nano Crystallites and Clustered Species in Modified Sodium Telluride Glasses

The structural properties, crystalline and clustering behavior of xNa2O·(1-x)TeO2 (15 £ x £ 65 mol% glasses have been investigated by FTIR spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM ). The experimental results have demonstrated that the basic structural units in telluride glasses change from highly strained TeO4 trigonal bipyramids to more regular TeO3 units containing non bridging oxygen atoms (NBO). The concentration of NBO atoms in telluride network increases with increasing? Na2O content. The present results suggest that (NBO) atoms in telluride glasses exist in their pure form in glasses of up to 35 mol% Na2O. But at higher Na2O concentrations, NBO atoms do not exist in their pure form; that is, the majority of NBO atoms are coordinated with high concentration from Na cations to form nano-crystalline clusters. The results based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calomerty (DSC) reveal the presence of two crystalline phases: ? TeO2 and Na2Te4O9 phases during the crystallization process of the prepared glass in the region < 50 mol% Na2O. But at higher Na2O concentrations, Na2Te2O5 and NaTeO3 crystalline clustered phase in the nono size scale are the dominant type. This means that NBO in TeO3 trigonal pyramids will interact with the excess of Na cation resulting in the three-dimensional network containing nano size clusters particularly in telluride glasses containing 50 and 65 mol% Na2O. An increase in Na2O concentration in Na2O-rich telluride network results in increasing Na coordination instead of breaking more tellurium–oxygen bonds.

Optical, structural and Near-IR NLO properties of gold nanoparticles doped sodium zinc borate glasses

Gold (Au) nanoparticles (NP) embedded borate glasses with the molar composition of (x‒0.1)Na2O‒10ZnO‒(90‒x)B2O3‒0.1AuCl3 (x = 10, 20, 30 mol %) have been prepared via melt quench technique. The effect of Na2O content on properties such as optical, structural and nonlinear optical (NLO) properties of gold NPs containing sodium zinc borate glasses were studied using UV‒Visible absorption, Fourier Transform Infrared spectroscopy (FTIR), High Resolution-Transmission Electron Microscope (HR‒TEM) and Z-scan measurements. X‒ray diffraction (XRD) measurements confirmed the glassy nature of the samples. UV‒Visible absorption spectra of glasses comprising Au NPs demonstrated a broad surface plasmon resonance (SPR) absorption peak near 577 nm due to the transition from d‒band to the Fermi level and this SPR peak demonstrated a red‒shift with increase in Na2O concentration. HR‒TEM micrographs revealed the presence of uniformly distributed and spherical shaped Au nanoparticles with an estimated average particle size of ∼6 nm (±1.5 nm). Nonlinear Optical (NLO) measurements were performed at three different off‒resonant wavelengths (750 nm, 800 nm, 850 nm) using femtosecond (fs) pulses (150 fs, 80 MHz) delivered by aTi:sapphire oscillator. Saturable Absorption (SA) kind of nonlinearity has been observed in the open aperture (OA) Z-scan data and is attributed to intraband transition within the Au NPs, while the closed aperture (CA) Z-scan data illustrated a negative type of nonlinear refraction attributed to effect of self-defocusing. NLO studies and the obtained nonlinear coefficients suggest that, the NZB glasses are potential candidates for mode-locking and switching applications in near-infrared spectral region.

Structural and Dielectric Studies on Na2O-PbO-SiO2 Glasses

Structural studies on x Na2O.(50-x)PbO.50SiO2 glasses have been carried out by different spectroscopic techniques. FTIR, EDX, NMR and dielectric spectroscopies are applied to follow the change in glass structure in terms of bridging oxygen (BO), non-bridging oxygen (NBO), and cluster species upon adding of Na2O at expense of PbO. NBOs are formed in the silicate network upon Na2O addition, since Na2O plays the role of glass modifier. Changes in relative area of Q2 (obtained from IR analysis) and NMR chemical shift of silicon nuclei with increasing Na2O are indicative for formation of the less shielded silicate units. While in sodium rich silicate glasses, the structural role of Na2O is changed due to changing Na coordination. FTIR analysis could be used to elucidate the changes related to changing the role of Na2O. The data obtained are correlated with that obtained from EDX spectroscopy. Moreover, the role of Na2O on the process of cluster formation when it substitutes PbO is determined. NBOs only are formed in the silicate network upon Na2O addition up to 30 mol%. On the other hand, in sodium rich silicate glasses an additional type of oxygen (free oxygen O2−) is present. The free oxygen is required for sodium to form aggregated cluster, specially at high concentration of Na2O (50 mol%). An increase in Na2O concentration in Na2O-rich silicate network results in increasing Na coordination instead of breaking more silicon–oxygen bonds. Scanning electron micrographs (SEM) and EDS spectroscopy in correlation with FTIR results confirm the presence of Na cluster species. The effect of clusters formation on AC conductivity was discussed according to jump relaxation model. Some parameters related to AC conductivity are found to be affected by the presence of cluster species in the glass network.

Uticaj procesnih parametara na osobine 4a zeolita uz karakterizaciju X-ray i FT-IR instrumentalnim metodama

For more than three decades 4A zeolite has been an irreplaceable ingredient of powder detergents, but there is still striving to it's improvement in order to meet the ever more stringent market and environmental demands.Alumina d.o.o., as one of the world-renowned producers of this zeolite, tends to meet these requirements, and one of the latest examples is the work on the production of zeolite 4A with increased adsorption of surface active substances, and the testing of parameters for the synthesis of such a zeolite as well as its characterization is the subject of this paper. The zeolite synthesis were performed to examine the effect of the Na2O concentration in the reaction system, as well as the crystallization time on thecharacteristics of detergent zeolite, namely:the adsorption of dibutylphthalate (DBP), the mean particle diameter, and the ion exchange capacity. The additional characterization of the samples was performed by XRD and FTIR instrumental methods. It's shown that the conditions examined have a significant effect on the characteristics of the synthesized powders. In general, at all crystallization times, adsorption of DBP, as well as the mean diameter, increases with the increase in Na2O concentration, while the ion exchange capacity decreases,and it is very important to find the right conditions in which all the parameters will be satisfactory.The influence of the crystallization time is not significantly pronounced when adsorption is concerned, but it is on the other characteristics of zeolite.XRD diffractograms and FT-IR spectroscopy showed the effect of reaction conditions on the crystallinity of the synthesized powders, and the relationship between the crystallinity and other characteristics of 4A zeolite.

Paste backfill of high-sulphide mill tailings using alkali-activated blast furnace slag: Effect of activator nature, concentration and slag properties

The effect of activator type, concentration and slag composition on the strength and stability properties of paste backfill (CPB) of high-sulphide tailings using alkali-activated slag (AAS) as binder (7wt.%) were investigated in this study. Acidic and neutral (AS–NS) slags were activated with liquid sodium silicate (LSS) and sodium hydroxide (SH) at 6–10wt.% concentrations. Ordinary Portland cement (OPC) results were used for comparison. The strength development was found to remarkably improve with increasing the concentration from 6 to 8wt.%. Further increase in concentration did not enhance the strength. SH was determined to produce higher early-age strength whilst LSS produced higher long-term strengths as an indication of slag selectivity for activators. More extensive gypsum formation was observed at lower concentrations in SEM/EDS studies. An increase in Na2O concentration raised the activator consumption. High concentrations also led to poorly crystallized C–S–H gel, loose structure and drying shrinkage cracks especially in NS–SH samples. A reduction in total porosity up to 20% was obtained in AAS samples compared to OPC. Amorphous structure, chemical modulus ratio and/or basicity index (BI) values were seen to control the pozzolanic reactivity, and therefore, the alkali-activation and hardening process.

Rheology of alkali-activated slag pastes. Effect of the nature and concentration of the activating solution

An understanding of the rheological behaviour of OPC-based products has been widely studied, for it is essential to determining and predicting the fresh and hardened characteristics and properties of pastes, mortars and concretes. The rheology of alkali-activated material (AAM) systems has been much less intensely researched, however.The present study aimed to ascertain the effect of factors such as the nature and concentration of the alkaline activator on the rheological behaviour of alkali-activated slag (AAS) pastes, with a comparison between the rheological parameters and fluidity of these pastes to the same parameters in OPC. More specifically, the study explored how paste rheology was affected by the nature of the alkaline activator (NaOH, 50/50wt% NaOH/Na2CO3 or waterglass – Wg), its concentration (3–5% Na2CO3 of slag weight) and, in the waterglass solution, the SiO2/Na2O ratio.The findings showed that AAS paste rheology is affected by the nature of the activator. The rheological behaviour in AAS pastes activated with NaOH alone or combined with Na2CO3 was similar to the rheology observed in OPC pastes, and fit the Bingham model. Conversely, the AAS pastes activated with waterglass fit the Herschel–Bulkley model and their rheology proved to depend on both the SiO2/Na2O ratio and the Na2O concentration. Moreover, regardless of the activator used (NaOH, Na2CO3 or waterglass), an increase in Na2O concentration implies a raise of shear stress.The formation of primary C–S–H gel in Wg–AAS and its effect on paste rheology were confirmed. Gel formation was likewise shown to be related to the SiO2/Na2O ratio and activator concentration.

Partitioning of trace elements between Na-bearing majoritic garnet and melt at 8.5 GPa and 1500–1900 °C

New experimental data on trace element partitioning between Na-bearing majoritic garnet and melt at P=8.5GPa and T=1500–1900°C applicable to partial melting of Na-rich eclogite are presented. We have found that Na-bearing garnet is a liquidus phase of the system at 1850–1650°C being accompanied by enstatitic pyroxene at lower temperatures. With decreasing temperature, Na concentration in garnet increases up to >1wt.% Na2O due to progressive incorporation of a Na majorite component (Na2MgSi5O12). Most of the studied trace elements are incompatible, except for Er, Tm, Yb (in some runs), Lu, and Sc (in all runs), which are distributed into garnet. The main characteristic of the trace-element partitioning in our experiments is a different behaviour of the LREE (La, Ce, Pr) in comparison with MREE and HREE (Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, and Lu). In particular, a significant increase of D values for LREE with the increase of Na2O concentration in garnet is observed. As predicted from lattice strain, partitioning coefficients for REEs entering the X site of garnet exhibit a near-parabolic dependence on ionic radius. The results of the study are applied to the formation of inclusions of Na-bearing majoritic garnets in diamonds, and equilibrium melts significantly enriched in LREEs.

Solubility of Al2O3 in the Na2O−Al2O3−H2O−CH3OH System at (30 and 60) °C

To realize the objective of high alumina yield and a high molar Na2O/Al2O3 ratio in caustic solutions for Bayer plants, this paper presents the solubility of Al2O3 in methanol-water solvent mixtures with a fixed mass ratio of methanol to water 1:1 at (30 and 60)degrees C and containing various Na2O concentrations. The Al2O3 solubility in the Na2O-Al2O3-H2O-CH3OH quaternary system increases with an increase of Na2O concentration, reaching maximum values of 1.70% and 2.48% by weight at (30 and 60) degrees C, respectively. Then, the solubility decreases with a further increase in the Na2O concentration. The equilibrium solids are aluminum hydroxide Al(OH)(3) and mono-sodium aluminate hydrate Na2O center dot Al2O3 center dot 2.5H(2)O in the different alkali concentration regions. The data show that the solubility of Al2O3 in the Na2O-Al2O3-H2O-CH3OH quaternary system is much lower than that in the Na2O-Al2O3-H2O ternary system.

Viscosity of Molten Na2O─B2O3 Slags

The viscosity of sodium borate slags at high Na2O concentrations (37.3 to 49.4 mol%) and high temperatures (1000° to 1300°C) follows an Arrhenius‐type relationship. This relationship was also observed for sodium borate slags (mass% Na2O/mass% B2O3= 0.86) containing CaO and CaF2 for the same temperature range. There has been a reduction in viscosity of the sodium borate slags (mass% Na2O3mass% B2O = 0.53 to 0.86) with increase in Na2O concentration. On adding CaO (10 to 50 mass%) to the sodium borate slag (mass% Na2O/mass% B2O3= 0.86), the viscosity increased considerably, while an addition of CaF2 (S to 15 mass%) to the slag (30.9 mass% Na2O3 35.8 mass% B2O3, 33.3 mass% CaO) decreased the viscosity. The average activation energies of Na2O─B2O3, Na2O─B2O3─CaO3 and Na2O─B2O3─CaO─CaF2 slag systems have been estimated as 14.6, 124.7, and 41.4 kJ/mol, respectively, for the given composition ranges and 1000° to 1300°C temperature range.