Silicate Formation Research Articles

Influence of colloid synthesis techniques on barium silicates formation using silica hydrogel derived from serpentine minerals

In the paper the interaction between silica SiO2 hydrogel recovered from serpentines (Mg(Fe))6[Si4O10](OH)8, sodium hydroxide NaOH and barium chloride BaCl2 in aqueous medium has been investigated by thermal and X-ray diffraction analyses. The experimental results have shown that depending on colloid synthesis conditions, the reactions occurring in the SiO2–NaOH–BaCl2–H2O system can develop in different directions. The stirring of the boiling aqueous suspension prepared in different ways from the mentioned reagents in air at ambient pressure can either lead to the precipitation of hydrated barium silicate species like BaSiO3·H2O or BaH2SiO4. On heating BaSiO3·H2O begins to crystallize into barium metasilicate BaSiO3 nano-sized particles after crystalline water removal at the temperature of 400 °C and reaches final crystallization at 800 °C. Unlike BaSiO3·H2O, the heat-treatment of BaH2SiO4 is accompanied by the formation of two barium silicate species: BaSiO3 and barium orthosilicate Ba2SiO4. The data derived from the experiments have allowed to better understand the mechanism of interactions occurring in the solution and to reveal the main factor governing the precipitates formation.

Mass spectrometry study of lignocellulosic biomass combustion and pyrolysis with NOx removal

Herein, a study of the thermal combustion/pyrolysis behaviour of three lignocellulosic biomass materials was tested. Alongside this, an investigation on the reduction of the subsequently produced pollution emissions was carried out. The lignocellulosic biomasses (miscanthus × giganteus, orange peel waste (OPW) and potato peel waste (PPW)) were physiochemically characterised, along with in-situ gas detection from the combustion/pyrolysis processes. XRD and EDX results showed high level of inorganic salts in the bulk and surface of the samples tested, which had an impact on the combustion/pyrolysis behaviour. Among the three lignocellulosic biomasses tested, OPW showed the highest higher heating value of 17.88 MJ Kg−1, whereas potato ash was the best candidate as a potential source of potassium (23.8 wt%) to be used in the fertiliser industry. The EDX results showed that miscanthus was the only lignocellulosic biomass to show high % Si in the surface composition. This was the reason for the low-temperature melting due to the formation of low fusion-temperature silicate as a result of SiO2, K, Cl and S. Pyrolysis experiments were conducted under pure nitrogen atmosphere, where hydrogen gas was observed in the temperature range of 580–700 °C. Combustion experiments were run under air where NOx emissions are generated during the combustion process. To mitigate those emissions, coupling the DeNOx catalyst with urea to construct an in-situ NH3-SCR system during the combustion achieved low levels of NOx emissions.

Reaction of pseudowollastonite with carbonate-bearing fluids: Implications for CO2 mineral sequestration

The kinetics of silicate carbonation in aqueous solutions are typically sluggish, especially at neutral to alkaline conditions. This hampers the complete understanding of the mechanisms and parameters that control mineral carbonation during carbon capture and storage (CCS). Here we study the hydrothermal dissolution and carbonation of pseudowollastonite (psw; α-CaSiO3), one of the most reactive silicates known, under a range of geochemical conditions ranging from acidic to strongly alkaline pH, presence/absence of different background alkali metal ions and carbonate sources (K2CO3 and Na2CO3, pH ~13, or NaHCO3 and KHCO3, pH ~9). We show that in addition to amorphous silica precipitation, the formation of secondary Na + Ca- or K + Ca-silicates in the presence of Na+ and K+ background ions, respectively, fosters the progress of psw carbonation. However, the formation of Ca-containing secondary crystalline silicates and Ca-containing amorphous silica is shown to be a strong handicap for a fully effective carbonation. In all cases a higher conversion into CaCO3 (up to ~70 mol%) is achieved when using bicarbonate salts (i.e., lower initial pH). By using a reactor with a pressurized CO2-solution, with and without Na+ or K+ background ions, rapid and nearly complete conversion of psw with a CaCO3 yield ~92 mol% is achieved because, in addition to the initial low pH (~3.7) that favored α-CaSiO3 dissolution, abundant Ca-free non-passivating amorphous silica formed along with calcite. These results imply that the presence (e.g., use of sea water during CO2 injection or mixing with saline formation solutions) or the release of different alkali metal ions (e.g., after feldspar and/or basaltic glass dissolution) in combination with a reaction-induced pH increase during in situ CCS scenarios may strongly limit carbonation due to the capture of alkaline-earth metals in secondary silicates and a reduction in reaction rates. In turn, our results show that the high conversion achieved in pure CO2-aqueous systems, while relevant for ex situ CCS, may not reflect the actual conversion in multicomponent natural systems following reactive transport during in situ CCS. Moreover, the precipitation of secondary silicate and calcium carbonate phases have a direct cementing effect, which could be detrimental for in situ CCS, as it would likely reduce host rock permeability, but would be relevant and beneficial for the setting of novel CaSiO3-based non-hydraulic cements with reduced CO2 footprint.

A comparative discussion of the evidence for biogenic silica in Wufeng-Longmaxi siliceous shale reservoir in the Sichuan basin, China

Abstract The siliceous Wufeng-Longmaxi Formation is the main shale gas play in China. It contains a large amount of silica, which has been reported to be of biogenic origin. The previous evidences for a biogenic origin include the presence of siliceous skeletal debris resembling organisms, such as sponge spicules, various parameters, such as the ratios of Al/(Al + Fe + Mn) and Si/(Si + Fe + Al + Ca), and a number of different correlations, such as a positive relationship of silica content with total organic matter (TOC). However, these evidences, especially various parameters and correlations, become unpersuasive when comparing Wufeng-Longmaxi Formation siliceous shale with other shale in these parameters and correlations. A series of petrographic thin section and scanning electron microscope (SEM) observations, elemental analysis, TOC analysis and mineral composition analysis were conducted to verify the unpersuasiveness of the existing evidences, and then propose new evidences to demonstrate the abundance of biogenic silica in Wufeng-Longmaxi siliceous shale. It is shown that siliceous ellipsoids are a better mark of biogenic silica in Wufeng-Longmaxi siliceous shale than sponge spicule, radiolarian and foraminifera. Except for the Barium (Ba) concentration, most elemental composition data cannot be used to distinguish biogenic silica from silica with an airborne volcanic ash origin. Furthermore, the poor crystal morphology of the silica in Wufeng-Longmaxi siliceous shale was a clear difference from the airborne volcanic ash-derived silica in Lucaogou Formation and hydrothermal silica in Nutitang and Doushantuo formations. Hence, the crystal morphology can be considered as a distinguishing feature for biogenic silica.

Thermal characteristics of ferronickel slag on roasting process with addition of sodium carbonate (Na2CO3)

Thermal characterization of ferronickel slag waste has been studied using TG / DTA, XRD, and SEM-EDX. The characterization of the initial samples of ferronickel slag was carried out TG / DTA to 1200°C. The result obtained is at a temperature of 800°C, there is an increasing mass and up to 4.68% at a temperature of 1200°C. At temperature of 807.4°C to 845.8°C, an exothermic reaction occurs. The increasing mass is due to the ferronickel slag which is originally in the form of metal, and then it was roasted to undergo an oxidation reaction so that the metal that has been formed, it returned into oxides. So that the weight of the sample mass increase. Samples of ferronickel slag added with sodium carbonate were also analyzed using TG / DTA. The results obtained are 2 endothermic peaks at temperatures of 90.6°C and 858.9°C with a total mass reduction of 49.3%. At a temperature of 90.6°C, there is a heavy loss caused by 2.38% loss of surface water. The XRD result of ferronickel slag is composed of enstatite (MgSiO3), forsterite (Mg2SiO4), fayalite (Fe2SiO4), and quartz (SiO2) structures. From the XRD analysis, the composition of silica oxide associates with magnesium and iron in the form of enstatite, forsterite, and fayalites is a very dominant composition. The roasting process of a mixture of ferronickel slag with sodium carbonate was carried out by heating at a temperature of 800-1000°C for 1 hour, and the sample result of roasting were analyzed using XRD. The result of roasting shows that the roasting process takes place more perfectly at higher temperature; it is indicated by the increasing phase intensity of SiO2 and the formation of sodium silicate (Na2SiO3). The result of SEM shows that the higher the temperature, the distribution of Na, Si, and O elements tend to cluster in the same place or spot, while the elements of Mg, Si, and O are less bonded.

Reaction of $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-x}$$ (YBCO) and fused silica in YBCO glass fibres

This work introduces the first reported experiments on drawing \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-x}\) (YBCO) into fibres with a fused silica cladding using a fibre draw tower to manufacture YBCO glass fibres. These fibre draw experiments allowed manufacturing fibre sections with core diameters between 50 and 200 \(\upmu \)m and a length of around 1.2 m. However, reactions between the fused silica cladding and the YBCO core were revealed by the fibre drawing process. Therefore, this study focusses on investigating these reactions (in as-drawn fibres as well as after additional heat-treatments) using energy dispersive spectroscopy analyses on an environmental scanning electron microscope as well as using X-ray photoelectron spectroscopy analyses and a cross-polarized light study. The results showed the formation of silica precipitations inside the as-drawn YBCO core, forming an interface layer between the core and the cladding regions, as well as the presence of a high silicon content inside the core with a possible silicate formation. Additional heat-treatments have shown the formation of silica and copper oxide co-precipitations at \(900{^{\circ }}\hbox {C}\). In addition, heat-treatments at higher temperatures have shown the occurrence of further reactions, which led to a degradation of the core and the formation of new phases.

Effects of mineral matters on the interactions between lignite and corncob during temperature-programmed co-pyrolysis

A lignite and a corncob were employed to investigate the effects of the inherent minerals on the interactions between lignite and corncob during pyrolysis. Prior to pyrolysis experiments, the selected samples were demineralized by using HCl and HF solution. Pyrolysis experiments for the raw samples, demineralized samples and their various purposeful blends of lignite and corncob were conducted in a lab-scale fixed-bed reactor. The results showed that the inherent minerals can significantly affect the pyrolysis behavior of the individual feedstocks. Particularly, it was observed that the alkali and alkaline earth metal species (AAEMs) in corncob was capable of promoting the decomposition of tar macromolecules and cracking liquid tar to form gas and char, which thus led to an increased gas yields with distinct soot observed. In terms of the blends, it was observed that the blends of the demineralized corncob and the demineralized lignite produced an unexpected higher yield of liquid tar than other blends. This suggested that the AAEMs in corncob or lignite could play a catalytic role in the decomposition of tar macromolecules, and this catalytic ability in corncob became stronger than that in lignite. The experimental results also indicated that the catalytic ability of the AAEMs varied in the blends of lignite and corncob. For the blends of the raw samples of lignite and corncob, this catalytic ability of the AAEMs was weaker for decomposing tar macromolecules compared to that in the blends of raw corncob and demineralized lignite or demineralized corncob and raw lignite. The interaction between catalytically active K and Ca species from corncob and the aluminosilicate species in the coal mineral matter occur, leading to the formation of calcium silicate (Ca2SiO4), which resulted in the formation of inactive compounds. In addition, it was observed that the inherent minerals in the raw samples could promote the reactivity of char with oxygen, which could be particularly observed with the char made from the raw sample of corncob.

Quantifying Reaction Products of Silicon Monoxide Electrodes during Initial Cycle in Lithium-Ion Batteries

Silicon monoxide (SiO) is a potential high-capacity anode material for lithium-ion batteries. However, its low initial Coulombic efficiency hinders its adoption in commercial batteries. The irreversible capacity of SiO is typically attributed to the formation of lithium silicate (such as Li4SiO4), lithium oxide (Li2O) and solid electrolyte interphase (SEI), but the amount of each product is typically not quantified. Here, we use an electrochemical approach, depth of discharge test, which we developed earlier [1] to estimate the amount of reaction products. Based on the first cycle discharge-charge capacities as well as the proportion of reversible capacity at different state of discharge (see Figure 1a and 1e), the lithiation mechanism of pristine SiO1.12 is estimated to be: SiO1.12 + 3.10 Li+ + 3.10 e- → 0.63 Li3.75Si + 0.15 Li2O + 0.11 Li4SiO4 + 0.26 SiO2 where inactive SiO2 in the material accounts for the lower-than-theoretical capacity, Li4SiO4 takes in lithium but cannot release them back, while Li3.75Si and Li2O give partial reversibility upon delithiation. We found that the amount of reaction products depends strongly on how the material is treated. Table I summarizes the corresponding reaction mechanisms [2]. In particular, while carbon-coating (SiO@C) increases the reversible capacity (y) as it increases its electrical conductivity which allows easier access to the lithium from Li2O, larger irreversible capacity is also observed with more Li4SiO4 formation. On the other hand, disproportionation (d-SiO@C-900°C and 1000°C) decreases the irreversible capacity in the initial cycle with the formation of large cluster of SiO2 which is electrochemically inactive. Though, the reversible capacity is reduced. Our results suggest that there are opportunities to further improve the first cycle efficiency of SiO by finding ways to control the reaction products during the initial lithiation process. More results and discussions will be presented at the meeting.

Kinetics and Mechanism of Low-Grade Manganese Ore Reduction by Natural Gas

The calcination and the reduction behaviors of a low-grade manganese ore by methane was studied at 973 K to 1273 K by several techniques. The onset temperatures of thermal decompositions of pyrolusite and calcite phases for this ore were found to be 868 K and 1056 K, and the rates of decompositions are obtained as 1.4 × 10−3 s−1 and 1.53 × 10−3 s−1, respectively. Because of the presence of manganese in the goethite structure of the ore, the goethite decomposition resulted in higher degrees of decomposition and magnetite formation at the studied temperature range. The exothermic reduction of manganese oxides to MnO started prior to the reduction of the coexisting iron oxides, and the apparent activation energy of reduction of Mn3O4 to MnO was determined. The reduction of manganese oxides resulted in CO2 gas release due to the reaction of H2O with the carbon supplied via methane cracking. Although manganese oxide minerals of the ore were not carburized at the experimental conditions, the manganese associated with iron oxides was carburized to cementite ((Fe,Mn)3C), and it was accompanied with CO gas release. Higher rates and extents of manganese oxides reduction were obtained with increase in temperature; however, the simultaneous formation of manganese silicates was more favorable at higher temperatures and hindered complete reduction.

An initial study on alkali activated limestone binders

Alkaline cements were studied using limestone as the only precursor activated with solutions of sodium hydroxide and waterglass; the activator was used at concentrations of 7 and 10%Na2O using modules of Ms = 0, 1 and 1.5. The compressive strength was followed on pastes and mortars for up to 360 days after an initial curing at 60 °C for 24 h. A paste with 7%Na2O and Ms = 1.5 and a mortar with 10%Na2O and Ms = 1 reached strength of 15-25 MPa after 360 days; the mortars showed trends towards higher strength with time. The characterization by SEM, EDS, XRD, FTIR indicated that the microstructure consisted of a mixture of silica gel, carbonates, C-S-H, N-C-S-H and N-S-H. 29Si MAS-NMR showed the formation of calcium silicates possibly of long chains which contributed to the strength.

Control of the formation and luminescent properties of polymorphic erbium silicates on silicon

We report on the control of the formation and the luminescent properties of polymorphic forms of erbium (Er) silicates by the modification of annealing temperatures, annealing atmospheres and chemical compositions. Four Er silicate polymorphs, X1-Er2SiO5, y-Er­2Si2O7, α-Er2Si2O7 and β-Er2Si2O7, are fabricated in Er-doped SiO2 films. Higher annealing temperatures turn the Er silicates into more stable polymorphs, but the annealing in O2 and the deviation of chemical compositions from the stoichiometry of Er silicates will restrain this process. The luminescent properties of these polymorphs are quite different due to their strong correlation with the crystallographic structures. Photoluminescence spectra with the main peaks at 1530 nm, 1536 nm, 1529 nm, and 1539 nm are obtained for X1-Er2SiO5, y-Er­2Si2O7, α-Er2Si2O7 and β-Er2Si2O7, respectively, and the highest photoluminescence efficiency is associated to Er ions in y-Er2Si2O7.

Термодинамическое моделирование процесса окисления доэвтектического сплава Moss-Mo3Si, легированного скандием или неодимом

In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in Mo-Mo3Si-Sc5Si3 и Mo-Mo3Si-NdSi systems with dry and moist air was performed in the temperature range 25-2000 °C. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics silicates, molybdates of scandium and neodymium were entered. Based on the obtained dependences of the composition of phases on temperature and charge of the oxidant (air or vapor-air mixture), the sequence of phase formation was determined and the compositions of oxidation products were estimated. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5Si-3(Sc, Nd) (wt.%) alloys involves a sequence of the following chemical transformations: at the beginning Mo and Sc (Nd) silicides oxidize forming Sc2O3 ( Nd2O3), SiO2 and elemental Mo, then molybdenum is oxidized to MoO2 and Sc2O3 or Nd2O3 interacts with SiO2 with the formation of appropriate silicates Sc2Si2O7 или Nd2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Sc2(MoO4)3 or Nd2Mo4O15 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. In addition, the formation of Nd2Mo2O7 and Nd2 (MoO4)3 is possible. During the oxidation of the Mo-5Si-3Nd alloy at T> 1700 oC, Nd(OH)3 can be formed in the condensed reaction products. According to the results of complete thermodynamic analysis, the formation of silicates and molybdates of scandium and neodymium can promote to the formation of a protective film on the surface of the alloys, which limits the diffusion of oxygen in them, and as a result, the oxidation resistance of alloys should increase.

Термодинамическое моделирование процесса окисления доэвтектического сплава Moss-Mo3Si, легированного иттрием

In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in the Mo-Mo3Si-Y5Si3 system with dry and moist air was performed in the temperature range 25-2000 °C. To predict the composition of oxidation products and the sequence of the formation of phase components, the dependences on the temperature and consumption of oxidants – water vapor and oxygen of the air – are obtained. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics of Y2Si2O7, Y2SiO5 silicates and yttrium molybdates Y2Mo3O12, Y2MoO6 were entered. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5 wt. % Si alloy of the hypoeutectic composition doped with yttrium can be represented as a sequence of the following chemical transformations: firstly Mo and Y silicides oxidize forming Y2O3, SiO2 and metallic Mo, then molybdenum is oxidized to MoO2 and Y2O3 interacts with SiO2 with the formation of silicates Y2SiO5 and Y2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Y2Mo3O12 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. Based on the results of a complete thermodynamic analysis, the possibility of the formation of silicates and yttrium molybdate during the oxidation of the hypoeutectic alloy Mo-5Si-3Y (wt. %) was established. This can increase its oxidation resistance due to the formation of a protective film limiting the diffusion of oxygen into the alloy, which, of course, requires experimental confirmation.

Experimental investigation of specific heat capacity improvement of a binary nitrate salt by addition of nanoparticles/microparticles

Abstract Several recent studies reported anomalous enhancement of specific heat capacity by doping minute concentration (e.g. 1 wt.%) of nanoparticles into the eutectic salt. In this work, silica particles with three different sizes and nano-sized silicon nitride and silicon carbide particles were dispersed in solar salt with particle concentrations of 0.5–7 wt.%. To prepare the composite material, a conventional two-step aqueous solution method was used and the drying approach was modified to suit large-scale production. The specific heat capacities of the composites, pure solar salt and particles were measured using differential scanning calorimetry in a temperature range of 300–400 ᵒC and the results were compared. Silicon nitride and silicon carbide nanoparticles have marginal effect on the specific heat capacity of solar salt over the examined concentration of 0.5–3 wt.%. The specific heat capacity of silica composites with 3 wt.% of silica were enhanced by 4.3–9.7% over that of the pure solar salt. However, when 5 wt.% and 7 wt.% of silica (30 μm) were dispersed, the specific heat capacity was reduced by 10.6% and 9%, respectively. Material characterization of the composite material proved the formation of sodium silicate due to reaction of silica and sodium nitrate, which is probably correlated to the reduction of specific heat capacity.

XPS study of homemade plasma enhanced atomic layer deposited La2O3/ZrO2 bilayer thin films

The ZrO2/La2O3 bilayer structure has been formed on Si by using atomic layer deposition system. The ZrO2/La2O3 (ZLS) bilayer was swapped to La2O3/ZrO2 (LZS) on Si and the interface properties were investigated. The chemical compositions of deposited thin films were studied by using XPS, while surface properties were investigated by means of AFM. The shift in binding energies of both gate stacks were observed. The XPS study shows the formation of silicate at the interface of both stacks. The lower surface roughness of 0.15 nm was observed for the LZS gate stack over the ZLS gate stack. This indicates that, La2O3/ZrO2/Si combination could be a more promising candidate for future MOS devices than that of ZrO2/La2O3/Si.

Promising Directions for the Stabilization of Ferroalloy Production Slags

In this paper the analysis of the processes for spontaneous decay of slags from the production of refined ferroalloy grades is performed. It is shown that the main reason for the decay is the formation of a dicalcium silicate in highly basic melts with CaO / SiO2 ratio of 1.5-3.1. Based on the performed studies, three main promising directions for the stabilization of slags of ferroalloy production have been formed. First direction is the replacement of the calcium cation (or transformation) in a dicalcium silicate, for example, with the magnesium cation or the production of non-decaying compounds of the gehlenite type (2CaO·Al2O3·SiO2), mainly due to the application of phase composition peculiarities of the waste rock for ferroalloy raw materials. Second direction is the reduction of the dicalcium silicate content with a decrease in the ratio of CaO / SiO2 in the slag less than 1.4, due to the separation of the silicothermic reduction process into two stages, obtaining in the first stage a low-basic (CaO / SiO2 = 1.3-1.4) non-decaying tailing slag, and on the second one - highly basic return slag (1.8-1.9), which is used in the first stage of this technological chain. The third direction is the replacement of the SiO anion of dicalcium silicate with other anions, for example, ВО by means of small additions of calcium borate, colemanite, etc. A possibility for stabilization of ferroalloy production slags with obtaining of construction crushed stone corresponding to the requirements of TU 0798-69-00186499-2014 "Crushed stone and sand from ferroalloy slags. Technical conditions», is shown experimentally.

The development of a new route to the synthesis of strontium orthosilicate

A new route including precipitation combined with calcination has been developed for the synthesis of strontium orthosilicate (Sr2SiO4) nano-sized particles. The stirring of the boiling aqua suspension prepared from hydrosilicagel derived from serpentine minerals ((Mg(Fe))6[Si4O10](OH)8), sodium hydroxide (NaOH) and strontium chloride (SrCl2) results in the precipitation of hydrated strontium silicate species whose dehydration is followed by their crystallization into strontium ortho- and metasilicate SrSiO3 on heating. The stirring time and sodium hydroxide concentration are the key parameters controlling strontium silicates formation. The influence of these parameters on the precipitates formation and their phase transformations at various temperatures has been studied by X-ray diffraction, thermal analyses and electron microscopy. The optimal parameters, namely the molar ratio of initial reagents, stirring time, the temperature and duration of heat treatment providing strontium orthosilicate synthesis, have been suggested. The average particle size of strontium orthosilicate synthesized by this method is 20–40 nm.

Green and Sustainable Concrete – The Potential Utilization of Rice Husk Ash and Egg Shells

Concrete which is widely used material in the construction industry, has a carbon footprint. Approximately 10% of global Carbon Dioxide (CO2) gas is emitted during the production of cement which is vital ingredient of concrete. The increase in production of cement affects global warming and climate change. Therefore, many have attempts have been made to develop green and sustainable concrete by utilizing different waste materials. With the utilization of waste materials as cement replacement, the CO2 gas emissions can be reduced as well as resolve the environmental issues that the inhabitants face during the disposal of such waste materials. This paper reviews the potential and innovative utilization of Rice Husk Ash (RHA) and Eggshells as partial cement replacement to develop green concrete. RHA which is rich in silica and eggshells contain identical amount of calcium oxide as cement, when finely grinded and used together as partial cement replacement, can trigger a pozzolanic reaction, in which silica reacts with calcium oxide resulting in the formation of calcium silicates which are responsible for achieving higher strengths.

Discovery of Stars Surrounded by Iron Dust in the Large Magellanic Cloud

Abstract We consider a small sample of oxygen-rich, asymptotic giant branch stars in the Large Magellanic Cloud, observed by the Spitzer Space Telescope, exhibiting a peculiar spectral energy distribution, which can hardly be explained by the common assumption that dust around Asymptotic Giant Branch stars is primarily composed of silicate grains. We suggest that this uncommon class of objects is the progeny of a metal-poor generation of stars, with metallicity Z ∼ 1–2 × 10−3, formed ∼100 Myr ago. The main dust component in the circumstellar envelope is solid iron. In these stars the poor formation of silicates is set by the strong nucleosynthesis experienced at the base of the envelope, which provokes a scarcity of magnesium atoms and water molecules, required for the silicate formation. The importance of the present results to interpret the data from the incoming James Webb Space Telescope is also discussed.

Mechanisms of adhesion degradation at the photovoltiac module's cell metallization‐encapsulant interface

AbstractAdhesion measurements and chemical characterization of the encapsulant/silver metallization interface of a photovoltaic (PV) module through temperature, humidity, and voltage bias exposures were conducted. Results demonstrate two independent degradation mechanisms: (a) with voltage bias, the ionic conduction of Na+ ions through the encapsulant results in the formation of sodium silicate at the silver metallization surface, thereby weakening that interface and (b) with moisture ingress, dissociation of the silane bonding to silver in the silver oxide similarly weakens this interface resulting in significantly lower debond energies.