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Molecular anisotropy plays an important role in the glass transition of a liquid. Recently, a novel bulk glass state has been discovered by optical microscopy experiments on suspensions of ellipsoidal colloids. "Liquid glass" is a disordered analog of a nematic liquid crystal, in which rotation motion is hindered but particles diffuse freely. Global nematic order is suppressed as clusters of aligned particles intertwine. We perform Brownian dynamics simulations to test the structure and dynamics of a dense system of soft ellipsoidal particles. As seen in the experiments and in accordance with predictions from the mode coupling theory, on the time scale of our simulations, rotation motion is frozen but translation motion persists in liquid glass. Analyses of the dynamic structure functions for translation and rotation corroborates the presence of two separate glass transitions for rotation and translation, respectively. Even though the equilibrium state should be nematic, aligned structures remain small and orientational order rapidly decays with increasing size. Long-wavelength fluctuations are remnants of the isotropic-nematic transition. [ABSTRACT FROM AUTHOR]

In order to illustrate the effects of Al 2 O 3 on silicate structure for synthesizing sodium calcium silicate compounds, the formation characteristics, lattice parameters, molecular structure and element chemical state of sodium calcium silicates with different Al 2 O 3 proportions through solid-state reaction were investigated using XRD, SEM-EDS, Raman spectroscopy and XPS analyses. Increasing the Al 2 O 3 content facilitates the formation of Na 2 CaSiO 4 and converts the polymorph of Na 2 Ca 6 Si 4 O 15 from γ- type into β -type. The product particles aggregate to form clumps by increasing the Al 2 O 3 content when the molar ratios of Na 2 O and CaO to SiO 2 are 0.5 and 1.5, and the network orderliness of silicates deteriorates to form glassy phase at the low CaO and Na 2 O contents. Al 2 O 3 can engage in the bonding process with silicate crystals to produce a finite solid solution. Increasing the Al 2 O 3 porportion is advantageous for facilitating the participation of [AlO 6 ] in the Si-O-Al bonding reaction, which leads to the depolymerization of [Si 2 O 7 ]6-, [Si 3 O 10 ]8- and [Si 6 O 18 ]12− and promotes the formation of silicate chains of [SiO 4 ]4- and [Si 2 O 7 ]6-. Moreover, increasing the contents of Na 2 O and CaO promote the formation of [AlO 4 ] and the depolymerization within silicate chains, which increases the bonding number of Si-O ter and Al-O ter and then reduces the binding energies of Si2p and Al2p orbits. [ABSTRACT FROM AUTHOR]

This research mainly focused on studying the influence of various curing media on the properties of lightweight geopolymer composites. Here, Ground Granulated Blast furnace Slag (GGBS), Paddy straws, and the combination of sodium silicate and sodium hydroxide at the ratio of 2.5:1 were used to produce geopolymer composites. For this experiment, two different parameters, i.e., variation of paddy straw (0, 5, 10, 15, and 20%) and variation of curing media (Intermittent, Heat, and Saline water), were chosen. The compressive strength of a 20% addition of paddy straw is dramatically reduced by 88.6%, while the density is reduced to 40.42%. Maximum flexure and tensile strength were noted as 65.11 and 45.5%, respectively, for the 15% addition of paddy straw. An interesting fact found from the samples cured under Saline water enhanced the overall compressive strength, tensile and flexural strength by 12.85, 45.5, and 21.2%, respectively, compared to the other two curing media. [ABSTRACT FROM AUTHOR]

Wellbore instability problems mainly contribute to increased nonproductive time (NPT) through drilling operation developments in the Southern Iraq oilfield. This work aims to study the impact of drilling fluid chemicals on shale formation based on lab tests. At the same time, a mechanical earth model (MEM) constructs for the wellbore failure analysis, which simulates the mechanical effect on the shale formation. The Lab tests showed that the shale formation is of many types, including illite, kaolinite, palygorskite clay mineral, montmorillonite, and non-clay minerals quartz and calcite, where kaolinite was a dominant clay mineral of the shale. The shale samples swelled slightly when sodium silicate was used with polymer mud, but they had significant swelling when potassium chloride was applied with polymer mud. The MEM showed that the leading cause of those problems is using unsuitable mud weight (10.4 ppg) during the drilling of the Tanuma formation. Thus, the model indicates that an equivalent mud weight of 11 ppg for vertical wells will be required to stabilize the Mishrif and Tanuma shale formations. This work was unique in studying chemical and mechanical effects to analyze the wellbore stability and develop the optimum solutions. [ABSTRACT FROM AUTHOR]

Alkaline iron (Fe) batteries are attractive due to the high abundance, low cost, and multiple valent states of Fe but show limited columbic efficiency and storage capacity when forming electrochemically inert Fe3O4 on discharging and parasitic H2 on charging. Herein, sodium silicate is found to promote Fe(OH)2/FeOOH against Fe(OH)2/Fe3O4 conversions. Electrochemical experiments, operando X‐ray characterization, and atomistic simulations reveal that improved Fe(OH)2/FeOOH conversion originates from (i) strong interaction between sodium silicate and iron oxide and (ii) silicate‐induced strengthening of hydrogen‐bond networks in electrolytes that inhibits water transport. Furthermore, the silicate additive suppresses hydrogen evolution by impairing energetics of water dissociation and hydroxyl de‐sorption on iron surfaces. This new silicate‐assisted redox chemistry mitigates H2 and Fe3O4 formation, improving storage capacity (199 mAh g−1 in half‐cells) and coulombic efficiency (94 % after 400 full‐cell cycles), paving a path to realizing green battery systems built from earth‐abundant materials. [ABSTRACT FROM AUTHOR]

Sodium silicate shell for investment casting is widely used in parts production. However, the key problems with this technique are that the shell has a low green strength, fired strength, and high residual strength in the shell; as well as environmental pollution resulting from toxic gas containing ammonia from the evaporation of ammonia liquor used as a hardener during the hardening process. The former is related to uncontrollable hardening reaction process, while the latter is related to hardener characteristics. In this work, the microfluidic technique was employed to precisely control of the hardening reaction of the shells, and aluminum potassium sulfate solution served as replacement for ammonia liquor. The green, fired, and residual strength of the shell specimens and their high-temperature self-load deformation were investigated. It is found that the hardening reaction can be effectively controlled, and the hardening characteristics of the shells were obviously improved. The bending strength of the shells increases initially and then decreases at the time of micro-droplet spreading. The specimens hardened for 8 min by micro-droplet method reached the highest green strength level of 37.48 MPa, a fired strength of 10.07 MPa, and a lowest high-temperature self-load deformation value of 0.18%, about 150%, 65% higher, and 53% lower than by the current immersion method, respectively. Moreover, the fracture surfaces of the specimens were observed using scanning electron microscopy (SEM). The results reveal that the number of cracks in the sodium silicate gel film in the shell decreased significantly. The cracking tendency caused by shrinkage stress during hardening was reduced. This is due to the accurate reactant flow control provided a large number of microreactors for sodium silicate hardening. The hardener micro-droplets with an excellent monodispersity dispersed in a small volume on the surface of a continuous phase of water glass film, the volume shrinkage caused by micro-hardening can easily be compensated by the continuous phase of the liquid sodium silicate in the adjacent region and the cracking stress is partially or completely relaxed. The shrinkage trend in the process of dehydration polymerization of sodium silicate decreased and the bending strength of shell specimen improved. Microfluidic technique provides a powerful means for accurate delivery of reactant and control of gel structure during shell hardening. [ABSTRACT FROM AUTHOR]

The grouting method is commonly used to seal rock fissures in subsea tunnels, and therefore the water and mud inrush can be prevented in this way. However, the current understanding of the grout diffusion mechanism inside the rock fissure under seawater conditions is still limited, especially inside the inclined rock fissure. This study first presented a novel rock fissure geometry schematization, which can be simplified to a single fissure with different inclinations. Then, based on the obtained time-varying grout viscosity under seawater conditions, the grout diffusion model of cement and sodium silicate grout (C-S grout) was developed by combining the equilibrium equation, constitutive equation, and continuity equation, which can be used to calculate the key parameters involved in rock fissure grouting, i.e., the grouting pressure and grout diffusion distance. After that, the change of grouting pressure with time was obtained. Furthermore, the numerical simulation of grouting in the inclined rock fissure was performed to verify the suitability of the grout diffusion model, and the comparison between them shows that they match reasonably well with each other. It is hoped that the conclusions could aid in the design of grouting in rock fissures around subsea tunnels with C-S grout in the future. HIGHLIGHTS: A novel rock fissure geometry schematization is presented. The C-S grout diffusion model in the inclined rock fissure under seawater is developed. The effect of time-varying viscosity on grout diffusion under seawater conditions is studied. The relation between the grouting pressure and grout diffusion distance is obtained. The numerical simulation of grouting in the inclined rock fissure is performed. [ABSTRACT FROM AUTHOR]

Cracks in concrete structures are unavoidable, resulting in the deterioration of concrete structures. An effective way to heal cracks, integrated with a suitable monitoring method, is of great significance. This research explores and demonstrates the autonomic healing and simultaneous ultrasonic monitoring of thin cracks using silica-based chemical agents. The sensitivity of ultrasonic waves to the change in the elastic properties of the medium through which it propagates is used to monitor the progressive healing of cracks in concrete. An increase in the ultrasonic pulse transmission (UPT) signal strength with the progression of healing in cracked concrete was used to interpret the condition of the crack. The ultrasonic results were validated by visual observations, an increase in compressive strength and a reduction in water permeability. Further, the efficacy of silica-based chemical healing agents in crack-healing concrete was also verified by microstructural scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests. The study successfully demonstrates the efficacy of sodium silicate as an effective chemical healing agent in cementitious materials, with the healing process well picked up by ultrasonic pulse transmission measurements. Practical Applications: The results of the study indicate that the utilization of sodium silicate as a healing agent in civil structures, integrated with the nondestructive monitoring of the healing process using the ultrasonic pulse transmission technique, represents an innovative approach to enhancing the durability and sustainability of concrete structures. Some practical applications include the following (1) the strength and life span of concrete bridges can be improved by integrating a crack repairing system with sodium silicate and monitoring through ultrasonic methods; (2) a sodium silicate solution can be injected into masonry substrate and mortar joints of historical buildings where cracks and weathering action have compromised the structural stability, and ultrasonic transducers can be strategically placed to monitor the healing progression and restoration process; and (3) this technique can be used to improve the resilience of marine structures by using sodium silicate as a healing solution in underwater concrete structures and combining it with ultrasonic monitoring. [ABSTRACT FROM AUTHOR]

Chemical activation of geopolymer concrete is critical for improving its performance. The purpose of this research is to improve the chemical activation of self-compacted fly ash-based geopolymer concrete exposed to chlorides using magnetized water. A multicompound activator containing sodium hydroxide (SH) and sodium silicate (SS) was used to activate fly ash. Various SS/SH ratios (1.0–3.0), various molarities of SH (8–16 M), and MW of 1.2 tesla were considered. Slump flow, L-box, v-funnel, compressive strength, chloride profile, and X-ray diffraction approaches were performed. The results confirmed that the optimal concentration of SH increased from 14 M in nonmagnetized concrete to 16 M in magnetized concrete, indicating that MW has a positive impact on the chemical activation and consequently the geopolymerization reaction. Concrete workability decreased as the SH concentration and SS/SH ratio increased. Using an SS/SH ratio of 3.0 results in superior mechanical behavior and increased chloride penetration resistance. [ABSTRACT FROM AUTHOR]

Halide perovskite quantum dots (QDs) glass has attracted much attention in the field of optoelectronics, but its photoluminescence (PL) properties and water stability still need further improvement. In this work, the melt-quenching method is used to successfully precipitate CsPbBr 3 QDs in borosilicate glass. By increasing the concentration of ZnO, the photoluminescence quantum yield (PLQY) of CsPbBr 3 QDs glass is enhanced up to 30 times from 1.91 % to 65.87 %. The results demonstrate that the introduction of ZnO loosens the glass network structure, which contributes to the QDs to precipitate. In addition, it can be found that the PL intensity maintains 91.68 % of the initial PL intensity after 30 days of immersion, which is attributed to ZnO delays the corrosion of borosilicate glass by water. The effect of ZnO-modified borosilicate glass structure on PL and stability provides a certain reference value for further research on QDs glass, and the good PLQY and water stability make ZnO-modified CsPbBr 3 QDs glass a potential material in the field of WLEDs. [ABSTRACT FROM AUTHOR]

A comparative study on three types of fireproofing coatings (namely, cementitious, sodium silicate, and epoxy) was made to determine their effectiveness in protecting steel structures. The effects of these coatings on the external protection of steel were structurally, thermally, and mechanically studied. The prepared cementitious coatings endured the heat until 1200 °C for 1 h showing dimensions stability without deformation nor cracking during firing. Both crushing strength (CS) and bulk density measurements decreased from 69 to 18 kg/cm2 and from 1.62 to 1.00 g/cm3 'respectively' with increasing both perlite and vermiculite percentages. Six of the prepared 48 sodium silicate and epoxy coatings succeeded in bearing heat until 900 °C for 3.5 h sustaining the steel substrates' temperature below 60 °C following the Underwriters Laboratory-94 (UL-94) standard. This protective effect was due to the formation of a hard glassy phase on the steel surface isolating it from the heat by the action of the applied constituents. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) thermograms for these succeeded samples revealed that they gave a high residual weight ranging from 63 to 88% when tested from room temperature up to 900 °C. Performing the scanning electron microscopy (SEM) test revealed that physical blending between both the binder and additives (other coating ingredients') has occurred. The results concluded that the used ingredients, which have low prices, compared to the imported ones, and are locally available, are recommended for the fire protection of steel. [ABSTRACT FROM AUTHOR]

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a green, environmentally friendly, and cost-effective grouting material, geopolymer requires consideration of grouting performance indicators such as strength and fluidity in order to achieve good injectability. For this reason, indoor ratio optimization experiments were conducted using liquid-solid ratio, water glass content, and water glass modulus as experimental factors. A multivariate second-order response surface regression model was constructed for compressive strength, flowability, and final setting time, and the influences of single factor and its interaction on various grouting performance indicators were obtained through variance analysis. The degree of influence of experimental factors on grouting performance indicators is as follows: liquid-solid ratio, water glass content, and water glass modulus. The interaction between liquid-solid ratio and water glass content has a significant impact on compressive strength, while the interaction between the other two factors has no significant impact on grouting performance indicators. Using the analytic hierarchy process and expert assignment method to obtain the relative weights of various grouting performance indicators, a multi- objective satisfaction function was constructed to optimize the ratio of slag-fly ash geopolymer grouting materials. Based on this, SEM testing was conducted on the slurry stone body with the best comprehensive ratio of grouting performance indicators. The results show that a small number of spherical unreacted fly ash particles can still be observed in the system, the slag particles and cement particles are basically fully reacted, and the oligomeric gel-like reaction products are rearranged and extended by deposition, and cross-lap with each other to form a dense and complete spatial network-like structure. [ABSTRACT FROM AUTHOR]

A number of synthesis parameters directly influence the degree of reticulation/geopolymerisation of metakaolin exposed to alkaline solutions of sodium hydroxide and/or sodium silicate. In the latter case, a sodium silicate solution can be depolymerised by the introduction of an appropriate amount of NaOH. The effects of the ageing of the activator solution on the reticulation of metakaolin-based geopolymers are quantified for the first time in this work. We studied the anionic species of the sodium silicate solution with the addition of NaOH made just before the preparation of the paste, 24 h or 7 days before. These three ageing periods cause a significant difference in the Si-bearing species in solution, as demonstrated by nuclear magnetic resonance on 29Si. The effect of these anionic species on the reticulation/polymerisation of metakaolin at room temperature was demonstrated by solid-state 27Al and 29Si MAS-NMR, the chemical stability in various solutions (deionised water, HCl, HNO3, H2SO4), and X-ray diffraction on geopolymer powders before and after immersion in acids. Compressive strength before and after the immersion in acidic media was an additional measurement to assess the overall structural stability of the 3D polymerised network of the final dense ceramic-like product. Ageing of the activator solution affected the chemical stability of the hardened geopolymers accompanied by a slight to severe reduction in strength after leaching in HNO3 or HCl and in H2SO4, respectively. The quantitative MAS-NMR description of the Si and Al coordination in the geopolymers was correlated with the chemical stability where the formulations with the higher number of Q4(0Al) and Q4(1Al) for the silicon species were more resistant (lower number of Na+ compensating for Al+3 to be exchanged with H+). The formulations with higher Al content in the structure, i.e. higher number of Q4(3Al) silicon species showed higher mechanical stability. These results show that the timing of the preparation of the alkaline activator is essential for a correct mix design. [ABSTRACT FROM AUTHOR]

High cost and resistance to harsh working conditions are challenges faced by most microwave absorbers for wide applications. Here, a low-cost graphene-based high-temperature microwave absorbing material is prepared. When the ratio is adjusted appropriately, excellent absorbing performance can be achieved at room temperature: C-2 is the most efficient material with respect to microwave absorption: it has an effective absorption bandwidth as wide as 4.6 GHz, and the minimum reflection is −39.2 dB with a thickness of 1.5 mm. Using the permittivity and TG data of the composites at 800 °C attained, it is demonstrated that the decomposition temperature of composites can be increased from 450° to 820°. When the mass ratio of graphene nanosheets and water glass is 1:2, the composites have the best high-temperature microwave absorption performance: C-2 exhibited the microwave absorption ability with a minimum reflection loss value of approximately −29.6 dB at 16.4 GHz, a thickness of 1.5 mm even at 800 °C. [ABSTRACT FROM AUTHOR]

The phase composition of the powder synthesized from aqueous solutions of sodium silicate Na2SiO3 and iron sulfate FeSO4 at the molar ratio Fe/Si = 2, as determined by x-ray diffraction (XRD) data, included hydrated sodium iron sulfate Na2Fe(SO4)2 · 4H2O and an x-ray amorphous product based on hydrated iron and silicon oxides. The phase composition of the powder obtained by fourfold washing of the synthesized powder in distilled water was represented by an x-ray amorphous product. Following firing in the air at temperatures ranging from 400 to 1200°C, hematite (Fe2O3) and cristobalite (SiO2) were identified in powder samples and the corresponding ceramics. Following firing at 900°C in graphite powder bedding, the phase composition of ceramic samples included magnetite (Fe3O4), laihunite (Fe4.74(SiO4)3), and fayalite (Fe2SiO4). The powder prepared from the product isolated from the mother liquor included hydrated sodium iron sulfate, Na2Fe(SO4)2 · 4H2O, and sodium iron sulfate hydroxide hydrate (metasideronatrite), Na4Fe2(SO4)4(OH)2 · 3H2O. Following heat treatment at 400°C, sodium iron sulfate (Na3Fe(SO4)3) was identified as the predominant phase in the powder. Powders resulting from the interaction of aqueous solutions of sodium silicate and iron sulfate can be used in the manufacture of high-temperature dyes and materials with magnetic properties, the creation of analogs of lunar or Martian regolith, as well as the development of functional (cathode) materials for Na-ion batteries. [ABSTRACT FROM AUTHOR]

Cement, which is a significant constituent in concrete, plays a crucial role in the construction industry. The manufacturing process of cement releases substantial amounts of CO2, thereby contributing to environmental concerns. To address this issue, geopolymers have emerged as promising alternative substitutes to ordinary Portland cement. However, one of the challenges in utilizing geopolymer binders is the need for activators to initiate the polymerization process. Sodium silicate and sodium hydroxide solution are commonly used activators, but ground granulated blast-furnace slag (GGBS) reacts quickly with these activators and reduces the setting time. In order to arrest quick settings and enhance the efficiency of concrete production, "water glass" is used as an activator. The present study investigates the flexural and split tensile strength of geopolymer concrete by optimizing the dosage of polypropylene fibers for different mix proportions of GPC activated with water glass. The optimum dosage of fibers was obtained by the addition of different dosages of polypropylene fibers ranging from 0, 0.2%, 0.4%, 0.6% and 0.8%. The results from the investigation revealed a consistent augmentation in compressive strength with the incremental addition of fibers up to a threshold of 0.6%; beyond this point, the strength exhibited a dimin-ishing trend, while the flexural strength and split tensile strength were enhanced from 25% to 45% with the addition of an optimum dosage of polypropylene fibers. By optimizing the material formulations and mix proportions, it is possible to achieve a superior performance by minimizing the environmental impact on the construction industry. [ABSTRACT FROM AUTHOR]

Despite quinoa (Chenopodium quinoa Willd.) gaining international popularity in the early 21st century for its nutritional benefits, there remains a critical need to optimize its cultivation practices in arid regions. Current research often overlooks the combined effects of supplemental irrigation and foliar treatments on quinoa's yield and water efficiency, particularly under challenging environmental conditions like those in Borg El-Arab, Egypt. Field studies were conducted in Borg El-Arab, Alexandria, Egypt, during the winter seasons of 2021/2022 and 2022/2023 to determine the influence of supplemental irrigation (rainfed, 2000, and 4000 m3/hectare, respectively) and foliar spraying of sodium silicate (control, 200, and 400 ppm) on yield, yield components, seed quality, and water usage efficiency in quinoa cv. Chibaya grown in arid lands. Three replications were used in a split-plot design. The main plots were designated for irrigation, while the subplots were designated for foliar spraying. The results indicate that applying irrigation at a rate of 4000 m3/hectare significantly increased leaf dry weight per plant by 23.5%, stem dry weight per plant by 18.7%, total dry weight per 25 plants by 21.4%, leaf area per plant by 19.2%, and straw yield by 26.8% compared to the control treatment. There were no significant differences between irrigation with the rate of 4000 m3 or 2000 m3/hectare on biological yield kg/hectare, N (%), P (mg/100 g), and protein (%). The utilization of sodium silicate had no significance on all studied features except for straw yield kg ha−1 at the rate of 200 or 400 ppm. The results regarding the RAPD1 primer revealed that the 2000+0 silicon treatment was the only treatment that resemble the control with no up- or downregulated fragment. Moreover, 20 upregulated fragments were observed in all treatments, while 19 DNA fragments were downregulated. Furthermore, the results obtained regarding the RAPD2 primer revealed that 53 fragments were upregulated and 19 downregulated. Additionally, the RAPD3 primer demonstrated that 40 DNA fragments were upregulated, whereas 18 downregulated DNA fragments were detected. It may be inferred that the application of irrigation at a rate of 4000 m3 ha−1 might serve as a supplemental irrigation method. Spraying sodium silicate at a 400 mg L−1 concentration could alleviate the dry climate on the Egyptian shore. [ABSTRACT FROM AUTHOR]

High early-strength concrete and geopolymer offer advantages of faster construction and require less curing time than traditional concrete. Bagasse ash (BA), an inert pozzolan with low reactivity in alkaline media, was activated with 10M NaOH to enhance its porosity and surface area. It was then incorporated into an 80:20 wt% mixture of metakaolin (MK) and BA to improve the early-strength properties of geopolymers. This study investigates the effects of varying amounts of activated bagasse ash (ABA) on the physical and mechanical properties of a binary MK-BA-based geopolymer. The pozzolan-to-alkali ratio was maintained at 1:1, with a difference of 10M NaOH-to-Na2SiO3. The results indicated that the compressive strength of formulation with 50 wt% ABA increased by approximately 33% compared with formulation without ABA. XRD analysis showed a sodium aluminum silicate peak at 3 days, which decreased after 28 days, confirmed by SEM/EDS. The transformation of sodium aluminosilicate gel into a dense geopolymer matrix was observed, with IR spectra demonstrating the presence of Si–O-(Si/Al) bonds contributing to high compressive strength formulations. Overall, the ABA led to the early formation of the geopolymer 3D network with high compressive strength values. [ABSTRACT FROM AUTHOR]

To improve the resource utilization of dredged silt and industrial waste, this study explores the efficacy of using ground granulated blast furnace slag (GGBS), active calcium oxide (CaO), and sodium silicate (Na2O·nSiO2) as alkali activators for silt stabilization. Through a combination of addition tests, response surface method experiments, and microscopic analyses, we identified key factors influencing the unconfined compressive strength (UCS) of stabilized silt, optimized material ratios, and elucidated stabilization mechanisms. The results revealed the following: (1) CaO exhibited the most pronounced stabilization effect, succeeded by Na2O·nSiO2, whereas GGBS alone displayed marginal efficacy. CaO-stabilized silt demonstrated rapid strength augmentation within the initial 7 d, while Na2O·nSiO2-stabilized silt demonstrated a more gradual strength enhancement over time, attributable to the delayed hydration of GGBS in non-alkaline conditions, with strength increments noticeably during later curing phases. (2) Response surface analysis demonstrated substantial interactions among GGBS-CaO and GGBS-Na2O·nSiO2, with the optimal dosages identified as 11.5% for GGBS, 4.1% for CaO, and 5.9% for Na2O·nSiO2. (3) X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses clarified that the hydration reactions within the GGBS-Na2O·nSiO2 composite cementitious system synergistically enhanced one another, with hydration products wrapping, filling, and binding the silt particles, thereby rendering the microstructure denser and more stable. Based on these experimental outcomes, we propose a microstructural mechanism model for the stabilization of dredged silt employing GGBS-CaO-Na2O·nSiO2. [ABSTRACT FROM AUTHOR]

• nSi-DA6, showed a notable increase in shoot and root dry weight, the number of leaves and the chlorophyll content. • nSi-DA6 and nSi-Atonik increased the phenols and flavonoids content and antioxidant activity in the leaves. • Sodium silicate and nSi-DA6 treatments increased the essential oil content in Z. multiflora. • The highest content of carvacrol and thymol was observed with Atonik and Si nanoparticles. Nanoparticles can drastically improve the growth, yield and quality of medicinal plants. In this study, silicon (Si) nanocomplexes were green synthesized from the growth regulators DA-6 and Atonik, and their effects on the growth, bioactive compounds, essential oil yield and composition in Zataria multiflora medicinal plant were compared with sodium silicate, a regular Si nanoparticle, DA-6 and Atonik. The Si-containing treatments such as sodium silicate and nanoparticles significantly increased shoot and root dry weight and the number of leaves, but not the inflorescence dry weight; however, the growth improvement effects of the Si-nanocomplexes were more evident. The nSi-DA6 and nSi-Atonik treatments did not affect the carotenoids and protein contents but increased the chlorophyll content in the leaves. The Si-nanocomplexes by increasing total phenols and total flavonoids enhanced antioxidant activity in the plant. Accumulation of epicatechin, naringenin and rosmarinic in response to the application of the Si-nanocomplexes promotes cardiovascular health effects and antioxidant activity of the plant. The essential oil (EO) content of the plants (2.75 %) increased to about 3.2 % after the application of Si-nanocomplexes. The main compounds of EO were carvacrol, thymol and linalool. The Si-nanocomplexes increased carvacrol and thymol content in the EO, however, linalool content remained unchanged after the treatments. Therefore, the application of silicon nanocomplexes increased the antioxidant and antimicrobial activity of EO without reducing the important factor in the fragrance of the EO. In conclusion, the application of 6 mM of nSi-DA6 and nSi-atonik nanoparticles was suggested to improve the growth and quality of Z. multiflora. [ABSTRACT FROM AUTHOR]

Spent waterglass foundry sand (SWFS) is a major waste in foundry industries and should be disposed of preferentially. Two SWFS subjected to working temperatures of 100°C (SWFS1) and 800°C (SWFS8) were prepared to investigate their effects on the flow, compressive strength, micromechanical properties, and pore structure of alkali-activated slag (AAS). Experimental results confirmed that the overall performance of AAS was determined by the dissolved properties of the dried waterglass coating and the content of SWFS. The flow values of AAS in the first 1 h were increased by adding two SWFS. SWFS1 can release abundant silica tetrahedra into the activation system, contributing to micromechanical and macromechanical properties. The compressive strength of SWFS1 -added AAS mortars was increased by 28.8% to 49.0% at 28 days. In contrast, SWFS8 exerted weaker dissolved properties. The compressive strength of AAS mortars was slightly enhanced and the maximum increment at 28 days was only 8.5%. In summary, this paper confirmed the feasibility of using SWFS as reactive fine aggregates for AAS owing to the dried waterglass coating. [ABSTRACT FROM AUTHOR]

In this paper, high transmittance glass-ceramics containing Zirconium Yttrium Oxide (Zr 0.82 Y 0.18 O 1.91) nanocrystals were successfully prepared by melt cooling and crystallization heat-treatment method. The effects of Y 2 O 3 concentration on the structure, crystallization performance, transmittance, and indentation fracture toughness of Na 2 O–Al 2 O 3 –B 2 O 3 –SiO 2 –ZrO 2 glass and glass-ceramics were explored. The addition of Y 2 O 3 improved the Vickers hardness (4.81 GPa–5.25 GPa) and indentation fracture toughness (0.78 MPam1/2 to 0.95 MPam1/2) of the glasses. Y 2 O 3 successfully facilitated the precipitation of the non-alkaline crystalline phase Zr 0.82 Y 0.18 O 1.91 at low heat-treatment temperatures. The precipitation of Zr 0.82 Y 0.18 O 1.91 nanocrystals improves the Vickers hardness (5.17 GPa–5.56 GPa) and indentation fracture toughness (0.90 MPam1/2 to 1.01 MPam1/2) in glass-ceramics, while concurrently preserving a high level of visible light transmittance (∼90 %). This demonstrates its potential applications in the field of protective covers for electronic displays. [ABSTRACT FROM AUTHOR]

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The origin of life is associated with the existing environmental factors of the Precambrian Era of the Earth. The minerals rich in sodium silicates, in aluminum and in other chemical elements, such as kaolinite, were among the factors present at that time. Kaolinite is an abundant mineral on our planet, which indicates that it possibly had an essential role in the origin of the first blocks that constructed life on Earth. Evidence of this is the cherts, which are rocks with a high concentration of silica that retain the vestiges of the most ancient life on our planet. There are also inorganic structures called biomorphs that are like the cherts of the Precambrian, which take on a morphology and crystalline structure depending on the chemical molecules that make up the reaction mixture. To evaluate the interaction of kaolinite with DNA, the objective of this work is to synthesize biomorphs in the presence of kaolinite and genomic DNA that comes from a prokaryote and a eukaryote microorganism. Our results show that the difference between the prokaryote DNA and the eukaryote DNA favors the morphology and the crystalline phase of the calcium silica–carbonate biomorphs, while in the case of the barium silica–carbonate biomorphs, the environmental factors participate directly in the morphology but not in the crystalline phase. Results show that when a mineral such as kaolinite is present in genomic DNA, it is precisely the DNA that controls both the morphology and the crystalline phase as well as the chemical composition of the structure. This fact is relevant as it shows that, independently of the morphology or the of size of the organism, it is the genomic DNA that controls all the chemical elements toward the most stable structure, therefore allowing the perpetuation, conservation and maintenance of life on our planet (since the origin of the genomic DNA in the Precambrian Era to the present day). [ABSTRACT FROM AUTHOR]

Purpose: To solve the problem of poor activity, large accumulation and low utilization rate of lithium slag,a technical study on the preparation of alkali-activated cementitious materials with lithium slag as the main raw material and mineral powder as silicon-aluminum corrective material was proposed. Method;The influence of various influencing factors on the compressive strength of cementitious materials was explored by orthogonal experiments to obtain the optimal raw material ratio; the optimal activation conditions of lithium slag were obtained by mechanical activation and thermal activation, and the microstructure of lithium slag-based cementitious materials was characterized by XRD and SKM. Result; The results show that when the lithium slag is mechanically activated for 60 min utes and thermally activated at 650 *C for 1 hour with a content of 60%,a water glass modulus of 1,a water glass content of 12%,a liquid-solid ratio of 0. 4,a curing temperature of 20 *C,and a stirring time of 10 minutes,the 28-day strength of the cementitious material can reach 45. 52 MPa;the main hydration products of the cementitious material are sodium zeolite,C-S-H gel,leucite,etc. The gel fills the pores,increases the density,and improves the performance of the cementitious material. Significance;It provides a new idea for the comprehensive utilization of lithium slag. [ABSTRACT FROM AUTHOR]

This study evaluates the quality and mechanical performance of various shapes of reclaimed concrete aggregates (RCAs), including elongated, cone-shaped, angular, and ordinary mix, in comparison to fresh aggregates (FAs). The RCAs are treated with fly ash-based geopolymer, and the effects of various percentages of geopolymer content on the geotechnical properties of the modified RCAs are investigated. The study finds that the angular shape of an RCA exhibits more strength than other shapes, and the use of fly ash-based geopolymer significantly improves the mechanical characteristics of the modified RCAs by up to 10%. The research also shows that the use of fly ash-based geopolymer-treated RCAs in the subbase layer of flexible pavements can lead to a reduction in the required thickness of the base layer, resulting in significant cost savings and curtailment of CO2 emission compared to the use of FAs. Abbreviations: AASTHO: American association of state highway and transportation officials; A: Area of cross-section of flexible pavement; ACV: Aggregate crushing value; AIV: Aggregate impact value; BS: British standard; ASTM: American society for testing and materials; Cc: Co-efficient of curvature; CO2: Carbon dioxide; Cu: Co-efficient of uniformity; D50: Mean grain size; DCW: Demolished concrete waste; CBR(s): Soaked California bearing ratio; FA: Fresh aggregate; FI: Flakiness index; EI: Elongation index; GC: Geopolymer content; GSD: Grain size distribution; k: Co-efficient of permeability; LAAV: Los Angeles abrasion value; m: Drainage co-efficient; m2: Drainage co-efficient of base layer; m3: Drainage co-efficient of subbase layer; ma: Dry mass of additive; MR: Resilient modulus; MR(B): Resilient modulus of base layer; MR(SB): Resilient modulus of subbase layer; MR(SG): Resilient modulus of subgrade layer; mRSM: Dry mass of reclaimed subbase material; NAOH: Sodium hydroxide; Na2SiO3: Sodium silicate; PKR: Pakistani Rupees; R: Reliability; RCA: Recycled concrete aggregate; So: Overall standard deviation; SN: Structural number; USCS: Unified soil classification system; NCHRP: National cooperative highway research programme; NHA: National highway authority; W18: 18-kip equivalent single axle loads; US$: US Dollars; ξOGC: Optimum geopolymer content; wopt: Optimum moisture content; γdmax: Maximum dry unit weight; a: Structural layer co-efficient; a1: Structural layer co-efficient of asphalt concrete; a2: Structural layer co-efficient of base layer; a3: Structural layer co-efficient of subbase layer; ΔPSI: Present serviceability index; tb: Thickness of base; tsb: Thickness of subbase; δ: Total material weight [ABSTRACT FROM AUTHOR]

Surface coating processes are carried out at high temperatures, so high heat input is applied to the material to be coated and may cause internal structure deterioration. In order to overcome this situation, the ability to reduce the coating temperature with a pretreatment such as Mechanical Activation was investigated in this study. In order to minimize the effect of alloying elements, DIN St28 steel is used. Powders containing B + SiC + KBF4 were mechanically alloyed by planetary ball milling devices to 10 and 20 h, respectively. By mixing boron-containing powder and sodium silicate, the samples were boronized at 923-1173 K temperature and 3-12 h. At the end of the mechanical alloying process, it was determined that the powder particle sizes were in the nanometer scale. According to the microstructure analysis, a single-layer Fe2B structure was successfully obtained on the samples surfaces. While no boride layers were formed on the sample surfaces at temperatures below 1023 K without MA pretreatment, boride layers were formed under these temperatures with MA pre-treatment. It has been observed that the depth of the Fe2B boride layer, which has achieved high diffusivity by creating many defects in the form of nanometer-sized crystal particles, increased with repeated fracture and cold welding of the powder particles with increasing mechanical alloying times. By calculating the activation energies of the powders, their relations with the mechanically unalloyed samples were compared and empirical formulas that could be used for similar experimental conditions were produced. The highest microhardness value was measured as 2200 HV and above. [ABSTRACT FROM AUTHOR]

Alkali-activated slag cementitious (AASC) foamed concrete (FC) has presented challenges such as rapid setting time and poor working performance. The use of sodium citrate (Na3Cit) as a retarding agent can improve the workability and microstructure of AASC foamed concrete. The effects of the dosage, modulus of water glass (WG, the main component is Na2O·nSiO2), and retarding agent on the properties and structure of FC were studied in this paper. The results indicated that using a water binder ratio of 0.4, WG with a modulus of 1.2, and an additional amount of 15% and 0.5% of Na3Cit, the prepared FC had a flowability of 190 mm. Its initial and final setting times were 3.7 h and 35.3 h. Its 7 d and 28 d compressive strengths reached 1.1 MPa and 1.5 MPa, respectively. After hardening, the pore walls were dense and consistent in size, with few larger pores and nearly spherical shapes. The addition of Na3Cit resulted in the formation of calcium citrate, which adsorbed onto the slag surface. This hindered the initial dissolution of the slag, reduced the number of hydration products produced, and decreased the early strength. With increasing curing time, the slag in the FC mixture dissolved further. This led to the decomposition of a portion of calcium citrate and the release of Ca2+. The Ca2+ reacted with [Si(OH)4]4− and [Al(OH)4]−, creating more C-(A)-S-H gel. This gel filled the voids in the FC and repaired any defects on the pore walls. Ultimately, this process increased the compressive strength of the FC in the later stages. [ABSTRACT FROM AUTHOR]

Alkalization has been used in aquaculture to improve water quality and increase production. With its intensification, there is a demand for new alkalizing agents or the same agents but with different purities and particle sizes. Therefore, this study aimed to evaluate the effect of alkalizing on the cultivation of juvenile jundiá Rhamdia quelen in a recirculation system. The juveniles were cultured to four alkalization procedures: water without alkalization, water with sodium silicate, water with sodium bicarbonate, and water with calcium carbonate. At the end of the experiment, the biomass and biomass gain of the fish grown in sodium bicarbonate water were higher than those in the environment without alkalizing. There were no differences in other performance parameters such as weight, total length, head length, weight gain, length gain, survival, Fulton, or specific growth rate. The alkalinization doubled the alkalinity and increased the water pH, with the pH of calcium carbonate having the highest value and higher stability over time. The ammonia, nitrite, and nitrate concentrations demonstrated greater nitrification efficiency in waters that received alkalinization, mainly with calcium carbonate and sodium bicarbonate. Calcium carbonate water resulted in the highest hardness due to calcium, which provided the lowest phosphate concentration. The results, associated with the ease of obtaining and the price, suggest that sodium silicate has potential to alkalize and should be further studied. Sodium bicarbonate should be utilized as an alkalizing agent in the intensive cultivation of R. quelen juveniles. [ABSTRACT FROM AUTHOR]

Bioinspired, graded structures with hierarchical porosity, combining high surface area with low density, are attractive for a wide range of applications. Local adaptation of properties makes it possible to fine‐tune their strength and degradation kinetics over time. Production of such structures is, however, still scientifically and technically challenging. A versatile approach for fabricating hierarchical, porous structures from water‐glass (WG), exploiting its inherent foaming ability in conjunction with robocasting, for applications such as, bone‐replacement scaffolds, is presented. The unique processing route that is proposed uses a purely inorganic, mouldable sodium silicate hydrogel based on WG as ink for robocasting, which makes it cost‐effective and highly environmentally friendly. The WG‐based hydrogels can be used in a pure state, and also as carrier systems, e.g., for tricalcium phosphate. Following heat treatment at a relatively low temperature of 450 °C, the robocast parts develop hierarchical porosities. Multi‐microscale porosity is created due to foaming during heating, in addition to the macroscale porosity designed during robocasting. The suggested process opens up a powerful alternative to fabrication routes presently available for hierarchically porous structures. [ABSTRACT FROM AUTHOR]

This study compares the structural, microstructural, thermal, and mechanical properties of geopolymer pastes (GPs) created through traditional methods and those derived from ready-to-use powders for geopolymer (RUPG) materials. The metakaolin (MK) precursor was activated using a sodium silicate solution or CaO and MOH (where M is Na or K). Various ratios of precursor/activator and Na2SiO3 or CaO/MOH were tested to determine the optimal combination. For RUPG, the MK precursor was activated by replacing the sodium silicate solution with quicklime. Metakaolin, alkaline hydroxide, and quicklime powders were mixed at different CaO ratios (wt%) and subjected to extensive ball milling to produce RUPG. The RUPG was then hydrated, molded, and cured at 20 °C and 50% relative humidity until testing. Analytical methods were used to characterize the raw and synthesized materials. Classic geopolymers (CGPs) activated with quicklime burst after one hour of molding. The results indicated slight amorphization of GP compared to raw MK, as confirmed by X-ray diffraction analysis, showing N(K)-A-S-H in CGP and N(K)-A-S-H with calcium silicate hydrate (C-S-H/C-A-S-H) in RUPG. The compressive strength of MK-based geopolymers reached 31.45 MPa and 34.92 MPa for GP and CGP, respectively, after 28 days of curing. [ABSTRACT FROM AUTHOR]

To improve the adaptability to complex shaped products, TiC particulates (TiCp) reinforced high-manganese steel matrix (TiCp/HMS) composites were prepared by the squeeze casting infiltration method, and the microstructure and the mechanical properties of the composites were investigated, with different TiCp volume fractions (35%, 50%, 65%). Water glass was applied as binder in the TiCp preforms, in which iron powder was added to adjust the TiCp fractions, and Si powder to activate the bonding of TiCp/steel interface. The results showed that with the increase of the volume fraction, the hardness of the composites increases gradually, with the highest reaching 60.7 HRC at 65 % TiCp, which is 2.7 times that of the matrix. However, the bending strength decreases gradually, with the maximum 439.0 MPa obtained at 35% TiCp. The impact toughness of the composites changes slightly. Due to the use of water glass, brittle glass phase is formed at the TiCp/steel interface, which reduces the mechanical properties of the composites. The addition of Si powder can improve the comprehensive mechanical properties of the composites. [ABSTRACT FROM AUTHOR]

Objective The contradiction of the oil-water relationship is prominent in offshore high porosity and permeability reservoirs. To address this issue, the adaptability evaluation of delayed gelation elastic silicic acid gel water plugging agent (6 wt% sodium silicate, 0.85 wt% activator ternary weak acid monoammonium GL-1 and 0.1 wt% mixed meter hydroxide) and the study of injection parameters were carried out. Methods The gelation properties and long-term stability of the water plugging agent were investigated using a visual method. The injectability, plugging ability, water erosion resistance, and selectivity of the water plugging agent were evaluated using sand-filled tube experiments, and the injection volume, acting position and injection rate of the water plugging agent were optimized. Results The adaptability evaluation showed that the gelation time of the water plugging agent from strength A to strength E was 72 h, and the final gel strength could reach strength I, which could meet the requirements of on-site implementation. The highest injection pressure was only 0.72 MPa, and the water plugging agent had good injectability. The water plugging agent had good selectivity, plugging and water erosion resistance properties. It could preferentially enter the high permeability channeling path. The plugging rate of the high permeability channeling path after gelation was more than 96%, and the breakup pressure gradient was higher than 4.46 MPa/m. The plugging rate was reduced by 2.31% after 50 PV continuously high-intensity water injection. After aging at 65 ℃ for 180 days, the dehydration rate was only 2.61%, indicating that the water plugging agent had good long-term properties after gelation. The experimental study of injection parameters showed that the optimal injection parameters of the water plugging agent were 0.8 PV of injection volume, 3 mL/min of injection rate, and the best acting position in the middle of the sand-filled tube. The plugging rate was 98.03% under the optimal injection conditions. Conclusion The delayed gelation elastic silicic acid gel water plugging agent was available for water plugging the high porosity and permeability reservoirs. [ABSTRACT FROM AUTHOR]

Nanotechnology can contribute significantly to the aquaculture sector for a wide range of applications. In this study, silica nanoparticles were prepared from beach sand and characterized. The XRD pattern was obtained and confirms the crystalline nature of potassium aluminium silicate [K(AlSi3O8)], sodium silicate (Na2Si2O5), and silicon dioxide (SiO2). FTIR confirms that intense peaks at 445, 795, and 1036 cm−1 are characteristic of Si–O–Si stretching vibration. TEM micrograph of silica nanoparticles found a spherical morphology with an average size of 42 nm. In vitro anti-WSSV (white spot syndrome virus) activity was carried out using PmLyo-Sf9 cells by attachment inhibitory and virucidal activity; the optimum concentration was determined as 320 μg/mL. The interaction of silica nanoparticles and VP28 envelope protein was confirmed using in silico approach. The complexes K(AlSi3O8)-VP28, Na2Si2O5-VP28, and SiO2-VP28 had binding affinities of −5.2, −7.2, and −8.3 Kcal/mol, respectively. [ABSTRACT FROM AUTHOR]

To reduce environmental pollution and conserve natural resources, calcined oyster shell ash (COSA), class F fly ash (FFA) and flue gas desulfurisation gypsum (FGDG) were used in an attempt to improve the engineering properties of alkali-activated ternary cementitious paste. The COSA – obtained by calcining crushed oyster shells at 800°C for 3 h and then grinding to pass through a no. 100 sieve – was used to substitute FFA at rates of 2.5, 5.0 and 7.5 mass%. The alkali solution used was 10M sodium hydroxide and sodium silicate with a modulus of 2.5. The hardened paste with 7.5% COSA, 1% FGDG and ratio of weight of added water to dry binder of 0.09 at 56 days had the highest compressive strength of 62 MPa. Microstructural analyses (scanning electron microscopy and energy-dispersive X-ray spectroscopy) showed that the resulting calcium aluminosilicate hydrate gel was found to have a compact microstructure, which improved the compressive strength of specimens. In summary, COSA successfully replaced natural limestone as a calcium oxide activator to manufacture an alkali-activated ternary cementitious paste containing FFA and FGDG. [ABSTRACT FROM AUTHOR]

This study investigates the use of waste glass as an active aggregate in glass polymers based on water glass, aiming to enhance the sustainability of construction materials by utilizing recyclable waste. Methodologically, the research employs a combination of water glass as a binder with waste glass, analyzing their chemical interaction and the resulting mechanical properties. The primary findings reveal that the inclusion of finely ground waste glass not only promotes the polycondensation and hardening processes of water glass but also significantly influences the adhesive and cohesive strengths of the developed glass polymers. After 7 days of hardening, the tensile strength of these materials exceeds that of standard concrete with values reaching up to 4.11 MPa, indicating strong adhesion capabilities that could pull out fragments of the concrete substrate. Conclusively, the study underscores the potential of waste glass in improving the structural and economic efficiencies of building materials, contributing to a reduction in landfill waste and offering a promising avenue for the innovative use of recyclable materials in construction. [ABSTRACT FROM AUTHOR]

In order to reduce the negative impact on the environment caused by the massive accumulation of red mud (RM) and Yellow River sand (YRS), new alkali-excited granulated blast-furnace slag (GGBS)/RM/YRS (AGRY) geopolymer cementitious materials were prepared by combining RM and YRS with GGBS in different ratios and using sodium silicate as the alkali exciter. The effects of YRS dosage and different curing conditions on the mechanical properties, hydration products, and pore structure of cementitious materials were investigated and analyzed in terms of cost and carbon emissions. The results showed that when the dosage of YRS was 40%, the compressive strength of the prepared AGRY cementitious material could reach 48.8 MPa at 28 d under standard curing, which showed mechanical properties comparable to those of the cementitious material without YRS. The cementitious material has a more compact internal structure, and the combination of RM and YRS promotes the chemical reaction of Al and Si elements and generates the (N, C)-A-S-H gel products, which are the key to the strength enhancement of the cementitious material. In addition, the prepared cementitious material is only 90% of the cement cost for the same strength and has low carbon emission accounting for only 43% of the cement carbon emission. This study not only provides a new way for the resource utilization of RM and YRS, but also contributes an excellent new environmentally friendly material for the construction industry to achieve the goal of low carbon development. [ABSTRACT FROM AUTHOR]

This study focuses on the use of alkali-activated materials and geopolymer grouts in deep soilmixing. Three types of grouts, incorporating metakaolin and/or slag and activated with sodium silicate solution, were characterized at different scales to understand the development of their local structure and macroscopic properties. The performance of the soilmix was assessed by using combinations of the grouts and model soils with different clay contents. Feret's approach was used to understand the development of compressive strength at different water-to-solid ratios ranging from 0.65 to 1. The results suggested that incorporating calcium reduced the water sensitivity of the materials, which is crucial in soilmixing. Adding soils to grouts resulted in improved mechanical properties, due to the influence of the granular skeleton. Based on strength results, binary soilmix mixtures containing 75% of metakaolin and 25% of slag, with H2O/Na2O ratios ranging from 28 to 42 demonstrated potential use for soilmixing due to the synergistic reactivity of metakaolin and slag. The optimization of compositions is necessary for achieving the desired properties of soil mixtures with higher H2O/Na2O ratios. [ABSTRACT FROM AUTHOR]

Fluororubber (FKM) has an important application in the industrial field. However, the coloring problem of FKM has been affecting the performance of its mechanical properties. Herein, a novel silicon dioxide (SiO2) colored with acid orange 7 (AO7) was prepared by sol–gel method to ameliorate the mechanical properties and coloring property of FKM. Acid orange silica sol was prepared by adding AO7 to sodium silicate solution, and then colored SiO2-AO7 was prepared by freeze drying. The effects of SiO2-AO7 modified FKM on mechanical properties, thermal conductivity and coloring were systematically studied. The results show that SiO2-AO7 has the advantage of enhancing the mechanical properties of FKM without affecting its color appearance. Relative to the unmodified FKM, the tensile strength and modulus at 300% elongation saw enhancements of 47.2% and 21.8% respectively. The SiO2-AO7 offers exceptional coloration and mechanical reinforcement, showing strong suitability for industrial application. [ABSTRACT FROM AUTHOR]

This study explores the potential of biosilica including diatom and diatomaceous earth as alternative silica sources for metakaolin-based geopolymers. Diatomaceous earth, composed of fossilised diatom frustules rich in amorphous silica, and diatoms, a sustainable source of renewable biosilica, are investigated for their effectiveness in enhancing geopolymer properties. Through detailed analyses including FTIR, XRD, and SEM, the study evaluates the impact of these biosilica sources on geopolymer compressive strength and microstructure, comparing them with conventional sodium silicate. Results show that diatoms exhibit significant promise, achieving 28-day strength up to 17.9 MPa at a 30% mass fraction, while diatomaceous earth reaches 26.2 MPa at a 50% addition rate, demonstrating their potential as active silica sources. Furthermore, the study elucidates the role of organic matter in biosilica on geopolymerisation, highlighting its influence on active silica release and the strength performance of products. This study proposes a novel pathway to enhance the sustainability of geopolymers through the utilisation of biosilica from diatoms, contributing to advancements in eco-efficient construction materials. [ABSTRACT FROM AUTHOR]

In vitro-In vivo correlation (IVIVC) is a main focus of the pharmaceutical industry, academia and the regulatory sectors, as this is an effective modelling tool to predict drug product in vivo performance based on in vitro release data and serve as a surrogate for bioequivalence studies, significantly reducing the need for clinical studies. Till now, IVIVCs have not been successfully developed for in situ forming implants due to the significantly different in vitro and in vivo drug release profiles that are typically achieved for these dosage forms. This is not unexpected considering the unique complexity of the drug release mechanisms of these products. Using risperidone in situ forming implants as a model, the current work focuses on: 1) identification of critical attributes of in vitro release testing methods that may contribute to differences in in vitro and in vivo drug release from in situ forming implants; and 2) optimization of the in vitro release method, with the aim of developing Level A IVIVCs for risperidone implants. Dissolution methods based on a novel Teflon shape controlling adapter along with a water non-dissolvable glass fiber membrane (GF/F) instead of a water dissolvable PVA film (named as GF/F-Teflon adapter and PVA-Teflon adapter, respectively), and an in-house fabricated Glass slide adapter were used to investigate the impact of: the surface-to-volume ratio, water uptake ratio, phase separation rate (measured by NMP release in 24 h post injection in vitro or in vivo), and mechanical pressure on the drug release patterns. The surface-to-volume ratio and water uptake were shown to be more critical in vitro release testing method attributes compared to the phase separation rate and mechanical pressure. The Glass slide adapter-based dissolution method, which allowed for the formation of depots with bio-mimicking surface-to-volume ratios and sufficient water uptake, has the ability to generate bio-relevant degradation profiles as well as in vitro release profiles for risperidone implants. For the first time, a Level A IVIVC (rabbit model) has been successfully developed for in situ forming implants. Release data for implant formulations with slightly different PLGA molecular weights (MWs) were used to develop the IVIVC. The predictability of the model passed external validation using the reference listed drug (RLD), Perseris®. IVIVC could not be developed when formulations with different PLGA molar ratios of lactic acid to glycolic acid (L/G) were included. The present work provides a comprehensive understanding of the impact of the testing method attributes on drug release from in situ forming implants, which is a valuable practice for level A IVIVC development. [Display omitted] [ABSTRACT FROM AUTHOR]

Structural alteration of synthetic implants aims to achieve better bioactivity, higher cellular response, and regulated degradability, all of which are critical criteria for a biomaterial to serve as a graft in bone regeneration. The aim of this work was to synthesize silicon-substituted hydroxyapatite and test its bioactivity in simulated body fluid (SBF) by proving the use of sodium metasilicate (Na2SiO3.9H2O) as an affordable precursor of silica. Thus, the study evaluated the in vitro bone-bonding capacity of hydroxyapatite (Ca10(PO4)6(OH)2) (HA) substituted with silicate ion (Ca10(PO4)6−x(SiO4)x(OH)2−x; SixHA). The SixHA with x = 0.4 was synthesized by utilizing a wet precipitation method with sodium metasilicate as a low-cost silica alternative for alkoxysilane precursors. The SixHA was then examined for properties such as morphology, elemental composition, phase composition, and the nature of chemical bonds using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffractometry (XRD), and Fourier transformed infrared spectroscopy (FTIR), respectively. An in vitro bioactivity experiment was also carried out by incubating the SixHA in simulated body fluid (SBF) at 36.5 ◦C for 7 and 14 days. The obtained results revealed the substitution of SiO44− for some PO4 3− groups in the hydroxyapatite structure. The SixHA nucleated more apatite crystals on its surface and demonstrated some degradability during the periods of immersion in SBF. The characteristics of the SixHA imply that it could be used as a graft in bone restoration applications, thus signifying that sodium metasilicate could serve as an economic silica source for silicon-substituted hydroxyapatite production. [ABSTRACT FROM AUTHOR]

The effect of electrokinetic sodium silicate injection into sand formation containing fine grains was studied in this research. A soil was grouted by Na-silicate in a 160 mm length electrokinetic cell with a 1 V/cm potential gradient for 1 week. Silicate solutions of 5% and 10% concentrations were injected through the reservoir next to the anode electrode, while 10% phosphoric acid or 30 mg/l bicarbonate solutions were used in the cathode chamber. When comparing the results, it was evident that the electrokinetic (EK) process without additives does not significantly enhance soil strength, except in the vicinity of the cathode electrode. Specifically, the most notable increase in strength was observed in the section proximal to the cathode, which demonstrated approximately 3.1 times higher strength than the control sample (i.e., without EK application). The obtained results indicate that injecting 5% and 10% Na-silicate solutions significantly increase the strength of soil all over the sample. Significant improvement in soil strength was observed when Na-Si was injected with bicarbonate as a catholyte during the EK process. Strength at the anode increased by 82% and 107% at 5% and 10% Na-Si concentrations, respectively. Resistance in the middle of the cell samples remained consistent for both concentrations. Immediate application of bicarbonate catholyte and silicate injection notably enhanced soil strength, while efficiency decreased when Na-Si was injected with phosphoric acid catholyte, especially near the cathode. Higher silicate concentrations resulted in reduced penetration length in both acid and bicarbonate catholytes. It can also be concluded that adding silicate to the anode chamber meaningfully reduces the electro-osmotic flow after 2 or 3 days. [ABSTRACT FROM AUTHOR]

The materials used in concentrating solar power (CSP) systems are becoming of interest because of the high energy efficiency of energy storage. Molten salts can be used as both heat-storage media and heat-transfer fluid in a CSP system. In molten salts, steel alloys used in vessels and pipelines are highly vulnerable to hot corrosion. To protect steel alloys, applying a coating is an excellent strategy to extend the life of the alloy. NiCrAl coatings are well-suited for high-temperature environments. The purpose of this study was to investigate the corrosion behavior of NiCrAl with Si addition coatings on AISI304 in molten salt. NiCrAl coatings with and without Si addition were deposited using the high-velocity oxygen fuel (HVOF) technique. The corrosion test was performed using an immersion test in modified solar salt with 0.5% NaCl at 400–600 °C. Gravimetric methods evaluate the weight change for immersion tests. At 400 °C, an increased amount of weight gain due to the oxidation reaction and molten salt infiltration was observed. At 600 °C, the corrosion reaction was more dominant, and apparent oxidation was decreased; however, oxidation products NiO and sodium aluminum silicate were detected. Si addition supports the formation of the protective oxide sodium aluminum silicate, which inhibits molten salt oxidation reaction and molten salt infiltration. [ABSTRACT FROM AUTHOR]

Nb2O5/TiO2 composite coatings were prepared in sodium silicate electrolyte, and the high-temperature oxidation properties of the coatings were improved. SEM showed that the number of micro-pores on the surface of the coatings decreased, and the content of Nb2O5 increased from 0 to 9.45% with the increase in Nb2O5 concentration. The coatings comprised O, Na, Al, Si, P, K, Ti, and Nb. Nb entered and was uniformly distributed in the coatings, and its content increased from 0 to 13.76%. Meanwhile, the thickness of the coatings increased from 29.57 to 43.27 µm. The coatings comprised anatase-TiO2, rutile-TiO2, Nb2O5, and Al2TiO5. The valence of Nb was assigned to Nb2O5 and NbxOy. The average oxidation rate decreased from 2.4333 × 10−5 to 2.8056 × 10−6 mg cm−2 s−1. Nb2O5 in the coatings hindered the high-temperature oxidation process and improved the high-temperature properties of the coatings. [ABSTRACT FROM AUTHOR]

Tetrasodium silicate (Na4SiO4) has emerged as a promising candidate for battery applications due to its favorable ionic transport properties. Atomic-scale simulations employing classical pair potentials have elucidated the defect mechanisms and ion migration dynamics in Na4SiO4. The Na Frenkel defect, characterized by the creation of a Na vacancy and an interstitial Na⁺ ion, is identified as the most energetically favorable defect process, facilitating efficient vacancy-assisted Na⁺ ion migration. This process results in three-dimensional ion diffusion with a low activation energy of 0.55 eV, indicating rapid ion movement within the material. Among monovalent dopants (Li⁺, K⁺, and Rb⁺), K⁺ was found to be the most advantageous for substitution on the Na site. For trivalent doping, Al is the most favorable on the Si site, generating additional Na⁺ ions and potentially enhancing ionic conductivity. Ge was identified as a promising isovalent dopant for the Si site. These theoretical findings suggest that Na4SiO4 could offer high ionic conductivity and stability when optimized through appropriate doping. Experimental validation of these predictions could lead to the development of advanced battery materials with improved performance and durability. [ABSTRACT FROM AUTHOR]

Although alkali-activated materials (AAMs) are considered potential substitutes for Portland cement, they still come with elevated costs and significant carbon dioxide emissions. The development of alternative activators, such as sodium silicate based on the dissolution of rice husk ash (RHA), could partially overcome these disadvantages. However, to maximise the mechanical performance of AAMs, the production of RHA-based sodium silicate (RHA-SS) needs to be fully understood. The production process of an alternative RHA-SS activator was thus investigated through experimental evaluations of RHA grinding time, RHA dissolution time and thermal curing temperature and time. Mechanical performance was evaluated through compressive strength tests carried out on alkali-activated pastes made up of metakaolin, as a precursor, and two different activators (RHA-SS and a commercial sodium silicate). Microstructural features were evaluated through X-ray diffraction, scanning electron microscopy and thermogravimetry analyses. Optimal production was obtained for a grinding time of 30 min, a thermal curing temperature of 40°C, dissolution time of 6 h and a thermal curing time of 8 h. The results show the efficiency of the alternative alkaline activator, which may represent a technically viable solution for larger scale application to AAMs. [ABSTRACT FROM AUTHOR]

Enhancing both the dynamic damping and static strength of ordinary Portland cement (OPC) concrete simultaneously is a significant challenge. Geopolymer concrete (GPC), particularly fly ash-based GPC, offers a promising alternative. This study explores the relationship between damping and strength in heat-cured, low-calcium fly ash-based GPC using sodium silicate (SS) and sodium hydroxide (SH) activators. The findings reveal that SS activators demonstrate stronger positive correlations between damping and strength compared to SH activators. Microstructural analysis indicated that increasing SS dosage from 55 kg/m² to 98 kg/m² resulted in a 17% increase in dynamic damping ratios and a 39% increase in static compressive strength. These results highlight the potential of GPC to surpass OPC concrete in applications requiring both enhanced damping and strength, offering a dual benefit not typically achievable with OPC. The study contributes to a deeper understanding of GPC's capabilities, paving the way for its broader adoption in construction projects. [ABSTRACT FROM AUTHOR]

In the production of cast aluminum automotive parts, cores made of sand and binders are often used to create the complex features that cannot be formed by the mold, such as internal passages. Core binders can be grouped into two different categories: organic and inorganic, depending on the binder system used. Conventional organic binders use petroleum-based materials that are sources of harmful gases. In contrast, inorganic binders such as sodium silicates (water glass) are environmentally friendly. The fabrication of inorganic cores requires a drying step that involves thermal dehydration (using hot box and hot air injection) and chemical reactions (polymerization) to give the sand core the necessary strength to withstand the constraints developed during core storage and the casting process. This drying step increases the duration of the process and affects the production line. This study evaluated different thin layer drying models to understand the drying behavior of sand cores in the inorganic process that uses both hot air and warm box. The Page model was found to best describe the drying kinetics based on experimental measurements on a rectangular core. The sorption properties of the core were determined by characterizing the desorption isotherms at three different temperatures. The energy required to remove water from the core was estimated and it is found that the highest energy reached a theoretical maximum at a box temperature of around 135 °C. [ABSTRACT FROM AUTHOR]