Silicate Solution Research Articles

Innovative shielding solutions by geopolymer paste and fly ash as effective substitution of cement materials for sustainable protection

This study aimed to evaluate gamma radiation shielding material based on fly ash (FA) type ASTM C 618 Class F with a sodium silicate solution with two molarity values. The composite geopolymer paste was synthesized by activating the alkaline solution and curing at 70 °C for 1 h. The sodium silicate solution was added to the FA matrix with two molarity values of SiO2/Na2O (2.2 and 3.3). The density of each sample GPp1 and GPp2 are 2.121 g/cm3 and 2.212 g/cm3, respectively. The XRD patterns revealed the successful preparation of the prepared samples. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) determined the samples' surface morphology and elemental composition. The compressive strength of GPp2 sample was higher than for the GPp1 sample at 7 and 28 days, respectively. The density and tensile strength of the GPp2 sample are high compared to GPp1. Also, the thermal expansion coefficients for GPp2 are 5.16 × 10-4 K-1 while the GPp1 equals 2.65 × 10-4 K-1. To evaluate the photon shielding competences of the geopolymer samples, the parameters such as half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff), and exposure buildup factor (EBF) were calculated. The highest Zeff was obtained for the GPp2 sample, whereas the lowest values were obtained for MFP, HVL, and Neff. Additionally, μm values were compared to theoretical Phy-X/PSD. It can be concluded that the investigated fly ash-based geopolymer paste is a promising material for gamma radiation shielding.

Fabrication and Characterization of Silica Nanoparticles from Beach Sand

Silica nanoparticles (SNPs) have many important applications including anti-reflection coating, self-cleaning surface and drug carriers. They are usually synthesized from the commercial precursor such as tetraethyl orthosilicate (TEOS). On the other hand, the natural silica can be found abundantly in organic materials such as rice husk and palm shell or in inorganic material such as beach sand and clay. Therefore, obtaining SNPs from the natural resources is very strategic for economic and technology considerations. This motivates the current study performing the synthesis and characterization of SNPs derived from the beach sand as one of natural resources available. Fort this purpose, the silica sands were mixed with sodium hydroxide (NaOH) for 2 hours at 90⁰ C, prior to filtering process for gaining the sodium silicate solution (SSS) which was further refluxed with hydrochloric acid (HCl) of 3 and 5 M until its pH reached the value of 7, and finally dried. The characterizations carried out on the resulting SNPs included UV-Vis and FTIR spectroscopies, XRD and SEM. The XRD study confirmed that the resulting samples are amorphous silica phase with the average crystallite size of 4.8 and 2.9 nm for the SNPs synthesized with 3 and 5 M chloric acid, respectively. The image analysis of SEM results revealed that the obtained SNPs have the average diameter of 11.6-12.00 nm. The formation of SNPs was further confirmed with the UV-Vis and FTIR spectroscopies. On the basis of investigation results, it was shown that the desired silica nanoparticles can be successfully derived from the beach sand.

Alkali-Activated Copper Slag with Carbon Reinforcement: Effects of Metakaolinite, OPC and Surfactants

Copper slag is an industrial residue with a large unutilized fraction. This study presents the development of alkali-activated composites from a copper slag named Koranel®. The effects of metakaolinite, ordinary Portland cement (OPC) and surfactants were investigated. The reactivity of Koranel with potassium silicate solutions with molar ratio R = SiO2/K2O varying from 1 to 2.75, with 0.25 intervals, was investigated using isothermal calorimetry. The reactivity was relatively low at 20 °C; the reaction started after a few hours with a low silica modulus, to several weeks with the highest silica modulus. The substitution of Koranel by OPC (5 wt.%) or by metakaolinite (10–20 wt.%), both led to higher reaction heat and rate; meanwhile, the addition of 2 wt.% polyethylene glycol/2-methyl 2,4 pentanediol delayed the reaction time in the system containing metakaolinite. Raising the curing temperature from 20 °C to 80 °C shortened the setting time of the low reactive systems, from several days to almost instantaneous, opening perspectives for their application in the production of prepreg composite materials. The use of carbon fabric as reinforcement in the alkali-activated matrix led to composite materials with flexural strength reaching 88 MPa and elastic modulus of about 19 GPa—interesting for engineering applications such as high-strength lightweight panels.

Geopolymers made using organic bases. Part I: Synthesis and atomic structure

AbstractGeopolymers can act as a facile forming route to aluminosilicate ceramic composites due to being processed as fluids rather than as powders. However, the compositions available via typical alkali geopolymers are limited by the presence of alkali cations, introduced by the alkali silicate solution precursors. In order to expand the ceramic compositions that are accessible by geopolymer processing, this study explored the use of three strong organic bases (guanidine, tetramethylguanidine [TMG], and tetramethylammonium hydroxide [TMAOH]) as alternatives to inorganic alkali hydroxides in geopolymer synthesis. Silicate solutions were able to be produced with all three bases and favorable silica speciation was identified in the guanidine and TMG silicate solutions. Monolithic bodies were produced using guanidine and TMAOH, while no TMG samples hardened. By 27Al and 29Si nuclear magnetic resonance spectroscopy and powder X‐ray diffraction, the guanidine samples were determined to be structurally similar to those made using sodium hydroxide and hence can be called geopolymers, while the solids made with TMAOH were not structurally similar to sodium geopolymers and contained one or more unknown phases. This study has demonstrated that geopolymers can be made using organic bases rather than alkali hydroxides and that the speciation of dissolved silica alone does not indicate that an organic base silicate solution will be reactive.

Effect of sand–precursor ratio on mechanical properties and durability of geopolymer mortar with manufactured sand

Abstract The geopolymer mortar (GPM) prepared from industrial by-products and alkali activation solution (AAS) is one of the hot spots of current building materials. As a feasible alternative to natural river sand, manufactured sand (MS) alleviates the global ecological pressure. In this study, MS was used for fine aggregate. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solution were used as AAS. Metakaolin (MK) and fly ash (FA) were used as the precursor to prepare MK-FA-based GPM with MS (MS-GPM), which was of great significance for saving non-renewable resources, mitigating the greenhouse effect, and recycling waste. Numerous studies were conducted to explore the effect of sand–precursor ratio (r sp) on mechanical and durability characteristics of MS-GPM. Relationships between compressive strength and tensile or flexural strength were established by linear fitting equation. Finally, analysis of variance (ANOVA) was used to systematically calculate the effect of r sp on performance. The results indicated that the mechanical strength and impermeability of MS-GPM decreased and crack resistance increased with r sp from 1 to 5. The strength of MS-GPM was the best when r sp was 1. With the increase of r sp, the proportion of MS in MS-GPM increases, and the relative cementitious material decreases, which has an adverse impact on mechanical properties and impermeability. Linear fitting revealed that the compressive strength of MS-GPM was closely related to tensile strength and flexural strength. ANOVA results indicated that r sp in the range of 1–5 had great effects on the performance of MS-GPM. The aim of this article is to further promote the possibility of applying MS-GPM in practical engineering by designing reasonable r sp.

Coiling of Secondary Tubes Formed from the Colloidal Exhaust of Primary Chemical Gardens.

Chemical gardens are self-organized precipitate structures such as thin-walled tubes and membrane-bound cells reminiscent of biological shapes. These usually inorganic precipitates compartmentalize the reaction system and allow the study of materials synthesis in very steep concentration gradients. We create such tubes by steadily injecting a mixture of MnCl2 and CuSO4 solutions into a large reservoir of sodium silicate solution. The growing tube is open at its tip and ejects a stream of colloidal particles that aggregate to form a secondary tube above the original one. This secondary tube can coil into a tightly wound nest-like structure, freely suspended underneath the solution-air interface. Using three-dimensional image reconstruction, we analyze the onset of coiling and show that the structure is helical with a helix radius that increases in the vertical direction. The height at which the coiling begins is lowered with each successive repeat of the growth experiment, suggesting that coiling is induced by small variations in the density of the silicate solution.

Mechanical Framework for Geopolymer Gels Construction: An Optimized LSTM Technique to Predict Compressive Strength of Fly Ash-Based Geopolymer Gels Concrete.

As an environmentally responsible alternative to conventional concrete, geopolymer concrete recycles previously used resources to prepare the cementitious component of the product. The challenging issue with employing geopolymer concrete in the building business is the absence of a standard mix design. According to the chemical composition of its components, this work proposes a thorough system or framework for estimating the compressive strength of fly ash-based geopolymer concrete (FAGC). It could be possible to construct a system for predicting the compressive strength of FAGC using soft computing methods, thereby avoiding the requirement for time-consuming and expensive experimental tests. A complete database of 162 compressive strength datasets was gathered from the research papers that were published between the years 2000 and 2020 and prepared to develop proposed models. To address the relationships between inputs and output variables, long short-term memory networks were deployed. Notably, the proposed model was examined using several soft computing methods. The modeling process incorporated 17 variables that affect the CSFAG, such as percentage of SiO2 (SiO2), percentage of Na2O (Na2O), percentage of CaO (CaO), percentage of Al2O3 (Al2O3), percentage of Fe2O3 (Fe2O3), fly ash (FA), coarse aggregate (CAgg), fine aggregate (FAgg), Sodium Hydroxide solution (SH), Sodium Silicate solution (SS), extra water (EW), superplasticizer (SP), SH concentration, percentage of SiO2 in SS, percentage of Na2O in SS, curing time, curing temperature that the proposed model was examined to several soft computing methods such as multi-layer perception neural network (MLPNN), Bayesian regularized neural network (BRNN), generalized feed-forward neural networks (GFNN), support vector regression (SVR), decision tree (DT), random forest (RF), and LSTM. Three main innovations of this study are using the LSTM model for predicting FAGC, optimizing the LSTM model by a new evolutionary algorithm called the marine predators algorithm (MPA), and considering the six new inputs in the modeling process, such as aggregate to total mass ratio, fine aggregate to total aggregate mass ratio, FASiO2:Al2O3 molar ratio, FA SiO2:Fe2O3 molar ratio, AA Na2O:SiO2 molar ratio, and the sum of SiO2, Al2O3, and Fe2O3 percent in FA. The performance capacity of LSTM-MPA was evaluated with other artificial intelligence models. The results indicate that the R2 and RMSE values for the proposed LSTM-MPA model were as follows: MLPNN (R2 = 0.896, RMSE = 3.745), BRNN (R2 = 0.931, RMSE = 2.785), GFFNN (R2 = 0.926, RMSE = 2.926), SVR-L (R2 = 0.921, RMSE = 3.017), SVR-P (R2 = 0.920, RMSE = 3.291), SVR-S (R2 = 0.934, RMSE = 2.823), SVR-RBF (R2 = 0.916, RMSE = 3.114), DT (R2 = 0.934, RMSE = 2.711), RF (R2 = 0.938, RMSE = 2.892), LSTM (R2 = 0.9725, RMSE = 1.7816), LSTM-MPA (R2 = 0.9940, RMSE = 0.8332), and LSTM-PSO (R2 = 0.9804, RMSE = 1.5221). Therefore, the proposed LSTM-MPA model can be employed as a reliable and accurate model for predicting CSFAG. Noteworthy, the results demonstrated the significance and influence of fly ash and sodium silicate solution chemical compositions on the compressive strength of FAGC. These variables could adequately present variations in the best mix designs discovered in earlier investigations. The suggested approach may also save time and money by accurately estimating the compressive strength of FAGC with low calcium content.

Ultrasound-Assisted Synthesis of Humic-Silica Composites by the Isolation of Humic Substances from Peat and Lignite.

The aim of the presented study was to evaluate an integrated, direct procedure for the synthesis of humic-silica composites (HSiC) by the isolation of humic substances (HS) from peat and lignite by the use of sodium silicate solution as an extractant. The obtained materials, because of the presence of humic functional groups, may potentially be used for removing contaminants from aqueous solutions. The quantitative assessment was based on experiments designed according to the Box-Behnken plan. The statistical analysis of the results allowed to determine the optimal conditions of the process tested, for which the isolation efficiency of humic substances (HS) was greater than 50 % for both raw materials. This made it possible to synthesize humic silica composites with a high content of HS, which have been qualitatively evaluated. This step was focused on the analysis of the humic structure using elemental analysis, spectroscopic methods, and differential thermal analysis coupled with thermogravimetry. On the basis of them, the presence of structures characteristic for HS in the HSiC tested was observed. Moreover, the results of the thermal analysis pointed to the higher thermal stability of the synthesized compounds, compared to the HS isolated with the use of a traditional extractant.

Effect of the incorporation of spent diatomaceous earths on the properties of alkaline activation cements based on sewage sludge ash

The aim of this research is to evaluate the synergistic effect of the incorporation of spent diatomaceous earth (SDE) from beer filtration on the technological properties of alkaline-activated cements (AACs) based on sewage sludge ash (SSA). Pastes have been manufactured by mixing different amounts of precursor, SSA (30–70% by weight) and SDE (30–70% by weight). The cements were activated using a solution of sodium silicate (50% by weight) and sodium hydroxide (50% by weight NaOH with 8 M) as activator. A liquid/binder (l/b) ratio of 1.2 were used for cements with 30–40% by weight of SSA and 1.0 for binders with 50–70% by weight of SSA. The specimens were cured at room temperature for 7, 28 and 56 days. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the microstructural characterization of the AACs. The mix proportion of the precursors or the CaO/SiO ratio exerts a substantial impact on the physical, mechanical, and thermal characteristics of the examined AACs. Binders containing 40% by weight SSA and 60% by weight SDE show optimal technological properties, reaching compressive strengths of 32.8 and 36.8 MPa at 28 and 56 days of curing, respectively. This may be due to the formation of different gel types according to SEM analysis: a compact gel phase characterized by a fibrous structure corresponding to the N-(A)-S-H gel surrounding flatter and more uniform zones corresponding to the calcium aluminosilicate gel, C-A-S-H, and a mixed amorphous N,C-A-S-H gel. The results indicated that is possible to produce more sustainable alternative binding materials from the recovery of two types of waste: one from the wastewater treatment, and the other originating from the filtration process in the brewing industry.

Assessing alkali activation of waste stone wool from greenhouses combined with direct foaming or granulation to obtain recycled plant substrate.

Stone wool is commonly used as a plant substrate in soilless cultivation and discarded after one growing season. Stone wool waste is difficult to recycle, and thus it is typically landfilled. Alkali-activation of stone wool (i.e., milling and mixing with an alkaline solution) has been shown to be a feasible way to upcycle this waste fraction into, for example, construction products. In this study, the aim was to develop recycled plant substrate from stone wool waste from greenhouses via alkali activation. Waste stone wool from greenhouses was characterized by X-ray fluorescence (XRF) and mixed with sodium silicate solution either directly or after ball milling. The alkali-activation process was combined with the addition of H 2O 2, pre-made foam, or granulation to obtain suitable porous material for the plant substrate application. Preliminary greenhouse cultivation experiments of pea ( Pisum sativum) were conducted with alkali-activated stone wool mixed with peat (a weight ratio of 1:1) and fertility analysis of the mixture were conducted. The results indicated that the most feasible production method was to use ball-milled stone wool and to combine alkali activation with granulation. The obtained granules could reach 2.7 MPa as compressive strength while the other methods resulted in very fragile material. The preliminary greenhouse cultivation experiments revealed that there were significant levels of nutrients (Ca, P, K, and S) and alkalinity leached from the granules which hindered the growth of pea. The high P and S amounts were also confirmed by the XRF results of stone wool. It can be concluded that the developed granules did not function well as a plant substrate for pea but could enable the re-utilization of the nutrients contained in the greenhouse stone wool waste. Moreover, their application to acidic sulfate soils could be feasible as it would utilize the alkalinity of granules.

Effect of construction demolition waste as fine aggregate and NaOH molarity on strength and fracture parameters of slag based geopolymer mortars

To achieve sustainable development, it is imperative that we find ways to manage sand resources wisely. One approach to mitigate the impact of sand extraction is the recycling of construction demolition waste (CDW) and its reuse in construction activities. This research paper primarily delves into the investigation of the strength and fracture properties of slag-based geopolymer mortar (SGPM) while varying the molarities of sodium hydroxide and altering the proportions of recycled fine aggregate (RFA) sourced from CDW. Two distinct binder-to-fine aggregate mix ratios, namely 1:1 and 1:3, were taken into consideration. The study employed sodium hydroxide (NaOH) and sodium silicate solutions as alkali-activators. Various NaOH concentrations of 2 M, 4 M, 6 M, 8 M, and 10 M were utilized, and RFA was employed to replace natural fine aggregate at levels of 10%, 20%, 30%, and 40%. The workability of SGPM was assessed in terms of flowability, while the compressive and flexural strengths were measured following a 28-day curing period. Moreover, fracture parameters, including load–deflection behavior, peak load, deflection at peak load, and fracture energy, were investigated through a three-point bending (TPB) test conducted on notched beams. The test results revealed that the flowability, expressed as a percentage of flow, decreased as the molarity of NaOH and the percentage of RFA increased. Conversely, the compressive and flexural strength values exhibited an upward trend as the NaOH concentration increased from 2 to 10 M. A substantial improvement in both compressive and flexural strengths was observed at a 10 M NaOH solution, with increases of 20.73% and 10.63% in the 1:1 mix ratio and 18.94% and 10.46% in the 1:3 mix ratio. However, these values decreased with an increase in the percentage of RFA, ranging from 10 to 40%. Notably, specimens containing 8 M and 10 M NaOH concentrations demonstrated a more brittle behavior compared to specimens with other NaOH concentrations. Moreover, a decline in fracture energies was evident as the molarity of NaOH and the percentage of RFA increased. These findings highlight effect of NaOH concentration, RFA content on mechanical and fracture properties of SGPM, providing valuable insights for sustainable construction materials.

Technology for Purifying Gas Emissions of Chemical Plants from Sulfur Dioxide Using Granular Carbonate Sludge

The results of studies on purification of gas emissions (GE) with a granular sorbent based on carbonate sludge from chemical water treatment are presented. The choice of conditions for modifying carbonate sludge with a sodium silicate solution to obtain a granular sorbent has been experimentally substantiated. It is confirmed that the data obtained correspond to and complement the theoretical principles and laws of colloidal and physical chemistry, industrial ecology, which is important for the choice of engineering solutions. A technological scheme for adsorption purification with a regeneration cycle of granular sorption material based on carbonate sludge from the Naberezhnye Chelny CHPP has been developed. It was concluded that the efficiency of GE treatment increased by up to 99% when using the proposed measures. The environmental and economic indicators of the use of the resulting granular sorbent in the scheme for purifying GE from SO2 in production of sodium hydrosulfite have been calculated. The prevented environmental harm to the environment from the use of the proposed technology has been determined, as well as the cost of production of granular sorption material and the payback period.

Mechanical Properties and Microstructure of Highly Flowable Geopolymer Composites with Low-Content Polyvinyl Alcohol Fiber

Geopolymer enhances mechanical properties with polyvinyl alcohol (PVA) fibers, but there has been limited research exploring low PVA fiber dosages for mechanical properties in 3D printing or shotcrete. This study experimentally investigated slag and fly ash-based geopolymer mixtures reinforced with 0.1%, 0.15%, and 0.2% PVA fiber by volume as well as a control group without PVA fibers. These mixtures were prepared using fly ash, quartz sand, slag powder, silica fume, and an aqueous sodium silicate solution as the alkali activator, with the addition of PVA fiber to enhance composite toughness. The mechanical properties of the composites, encompassing dog-bone tensile properties, cubic compressive strength, bending and post-bending compressive strength, and prism compressive properties, were evaluated. Significantly, specimens with 0.15% PVA fibers exhibited optimal performance, revealing a notable 28.57% increase in tensile stress, a 36.45% surge in prism compressive strain, and a 47.59% rise in tensile strain compared to fiber-free specimens. Furthermore, environmental scanning electron microscopy observations were employed to scrutinize the microscopic mechanisms of composites incorporating PVA fibers, slag, and fly ash. In comparison to fiber-free specimens, prism compressive specimens with 0.15% PVA fibers demonstrated a 27.17% increase in post-cracking loading capacity, a 44.07% increase in post-cracking ductility, a 50.00% increase in peak strain energy, and a 76.36% increase in strain energy ratio.

Study on the mechanical behavior of construction and demolition waste-based geopolymers under high-temperature conditions

ABSTRACT This study explores the mechanical properties of geopolymers derived from construction and demolition waste exposed to high temperatures. Geopolymers were exclusively crafted from waste bricks or ceramic tiles, activated with potassium hydroxide/sodium silicate solution. We assessed compressive deformation during 850°C − 1050°C exposure and residual strength post 600°C − 1050°C exposure (simulating ISO 834 curve). Microstructure and bulk properties were also examined.Both geopolymers exhibitecd consistent post-fire behavior. Compressive strength decreased between 600°C and 800°C but rebounded at 1050°C, surpassing initial levels. At 1050°C, density dropped by 8–9%, with a 7–10% mass loss. In fire tests, ceramic tile-based geopolymers displayed plastic deformation at all tested temperatures without macro-fractures, whereas brick-based geopolymers remained elastic up to 1000°C with evident macro-fractures.These findings suggest the potential of both geopolymers as fire-resistant building materials, contributing to advancements in construction materials.

Growth and characterization of plasma electrolytic oxidation coating on 60%SiCp/2009 aluminum matrix composite

A ceramic coating on 60vol.%SiCP/2009 aluminum matrix composite was prepared by plasma electrolytic oxidation (PEO) in silicate solution. The microstructure, composition and wettability of the PEO coating and its corrosion resistance were investigated. The generation mechanism of spark discharge on the SiC particles surface was also discussed. It is found that the insoluble compound (SiO2) from silicate solution is vital for the ignition of spark discharge on the SiC particles surface. The defects in the Al−Si−O compounds provide a priority path for the conduction of discharge current on the SiC particles surface. A uniform coating of 5.5 μm was fabricated after 1200 s. Moreover, with the increase of time, the surface free energy of PEO coating reached the maximum of 37.10 mJ/cm2 at 40 s, and then decreased to 25.95 mJ/cm2 at 1200 s. Furthermore, the corrosion resistance of the composite was greatly improved by PEO treatment.

The Effects of Various Silicate Coatings on the Durability of Concrete: Mechanisms and Implications

Silicate solutions can improve the durability of concrete conveniently and effectively. To horizontally compare the enhancement effects of different composite silicate solutions, three types of silicate surface treatment agents were prepared by using sodium silicate, potassium silicate, and lithium silicate as the main agents, along with urea, sodium polyacrylate, catalysts, and fluoro-carbon surfactants as the adjuvants. Furthermore, their effects on the durability of concrete were compared. The results showed that silicate surface treatment could reduce the content of Ca(OH)2, increase the content of hydrated calcium silicate (C-S-H), and improve the compactness and hydrophobicity of the hardened cement surface. Although the three surface treatments enhanced the durability of concrete, the effects differed based on the complexities and mixtures. The sodium silicate compounded with potassium silicate performed the best of all three, wherein the content of the C-S-H gel increased by 389.8%, the permeability decreased by 60.6%, the water contact angle improved to 83.5° and the chloride ion resistance and freeze–thaw resistance of concrete increased by 36.7% and 37.34%, respectively, compared with the control sample.

Suitability evaluation of selected sand geological formations for synthesis high purity crystalline silica, Iraq

This study aims determination if the sand collected from Injana and Dibdibba Formations are suitable for use as low-cost raw materials in the manufacture of high-purity crystalline silica. Sand is distributed in vast quantities within the two Formations, which occupy large portions of Iraq’s southern desert. Quartz is the predominant mineral phase, followed by calcite, feldspar, and dolomite respectively, based on mineral analysis data. SiO2 is the main oxide in sand with an average of (82.76%), (90.24%) and the rest of oxides are CaO (6.28%), (1.64%), Al2O3 (4.02%),(3.19%), Fe2O3(2.73%), (0.86%), K2O+ Na2O (2.05%), (2.51%), SO3(0.05%), (0.47%), MnO (0.01%), (0.03%) P2O2 (0.23%),(0.03%), and MgO (1.75%), (1.01%) in Injana and Dibdibba Formations respectively, which are considered as impurities impact the manufacturing properties of sand. The coprecipitation method, which produces high purity crystalline silica at a low cost, involves three steps: the first involves soaking raw sand powder in 2M HCl for 24 hours; The second involves mix purified sand with NaOH while stirring and heating it to 95C° to produce Na2SiO3; and the third involves adding 3M HCl to sodium silicate solution to produce Si(OH)4 and drying it to produce high purity of silica. The prepared silica got mineral analysis and chemical analysis. The synthesized silica was in the crystalline phase, according to the results of the mineral characterization. In synthetic silica of Injana and Dibdibba sand, The amount of SiO2 increased according to chemical analysis, reaching 96.62%, and 97.69% respectively, while all other oxides (impurities) were lowered to their lowest levels. FE-SEM revealed the existence of spherical, well-agglomerated synthetic silica particles within the size 28.6 nm and 24.76 nm in synthetic silica particles of Injana sand and Dibdibba sand respectively.

Hydrophobic and hygroscopic properties of cellulose treated with silicone agents

The effects of various cellulose treatments on the hydrophobic properties and sorption behavior with respect to liquid water uptake and water vapor sorption were examined within the study. Different hydrophobic agents based on silicon compounds were applied to improve the properties of cellulose-based sheets. The 1H,1H,2H,2H perfluorooctyltriethoxysilane treatment increased hydrophobicity significantly, while N-octyltriethoxysilane and inorganic sodium silicate solution treatments only slightly affected the properties. Silicone-cellulose interaction varied, influencing the fiber saturation and moisture content of the material. The swelling differences between untreated and treated cellulose and, consequently, the uncovering of new active sorption sites during a swelling process and the increase in the content of bound water were confirmed by the T2 relaxation times analysis. The GDW sorption model estimated maximum water content but lacked activation dynamics. The blocking phenomenon of active sorption sites together with silicone improved hydrophobicity had different mechanisms for applied agents. The 1H,1H,2H,2H perfluorooctyltriethoxysilane additionally cross-linked silane structure and restricted cellulose swelling.

Open-cell cordierite-based foams from eco-friendly geopolymer precursors via replica route

Open-cell cordierite-based foams with high porosity were synthesized by a facile replica route, using geopolymers as precursors and polyurethane foams as polymer templates. The geopolymer precursors, incorporating MgO as an additional magnesium source, were prepared using metakaolin and fly ash under activation of NaOH solution and sodium silicate solution. Polyurethane foams with geopolymer were obtained by an impregnation method. The hybrid foams comprising polyurethane foam and geopolymer were cured/solidified at 75 °C for 24 h. Subsequently, the hybrid foams were subjected to ammonium ion-exchange followed by sintering at 1200 °C for 2 h to produce porous cordierite-based ceramics. The resulting foamed ceramics were characterized in terms of bulk density, porosity, structural evolution, and mechanical properties. Porous cordierite-based ceramic foams exhibiting a total porosity of approximately 88.64 vol% and a compressive strength of around 0.47 MPa were successfully fabricated by the replica route.

SYNTHESIS OF NANO-SILICA FROM LOA KULU RICE HUSK USING THE SOL-GEL METHOD

Silica is a material that is widely found in nature and is able to withstand corrosion attacks from corrosive environments. However, this natural material must be extracted to obtain high purity silica. Simple sol-gel method is used to solve the extraction problem (nano-silica with high purity). The natural materials used in this research come from organic materials, namely rice husks from the local area (Loa Kulu area). The main objective of this experiment is studying the effect concentration of HCl for crystalline size. The synthesis of silica was carried out with the preparation of ashes, then mixed with NaOH 7M until a solution of sodium silicate was produced. Silicate sodium solution was pressed with HCl 2M to form a silica gel with pH 7, 5, and 3 then was dried to produce silica powder. Silica powder was then burned at a temperature of 1000°C to produce silica with a crystalline phase. Based on the experiment, silica powder before calcination has amorphous phase and at any pH variation, the crystallite size calculated with the Debye Scherrer approach does not show any change the crystallite size by the variation of the silica gel’s pH. In addition, silica powder calcinated at 1000°C has amorphous and cristobalite phases and showed changes in crystal size after calculated with Debye Scherrer’s approach.