Silica Research Articles

Characterization of Palm Kernel Shell Ash Nanoparticles as Coating Material for High Temperature Applications

The kernel shell of oil palm (Elaesis guineensis) was milled, calcinated and synthesized into nanoparticles (np) with a view to analyzing and ascertaining its high temperature strength. The synthesized particles were characterized to reveal their elemental composition and temperature of maximal decomposition/destruction, with the solgel method employed in the nanoparticle synthesis. The morphology of the Palm Kernel Shell Ash nanoparticles (PKSAnp) viewed from Transmission Electron Microscope (TEM) revealed that the nanoparticles were solid in nature but vary in sizes with some spherical particles visible, and an average particle size found to be 39.17nm. The Electron Dispersion Spectroscope (EDS) result shows that only elements such as C, O, Si, Al, Ca, and K are present in the PKSAnp, with silicon (Si) found to be dominant. Oxides of Silicon and Aluminum (SiO2 and Al2O3) were identified as the key chemical compounds in PKSAnp from X-Ray Fluorescence (XRF) investigation whereas K2O, CaO and Na2O were among the other oxides present in traces. The Thermogravimetric analysis (TGA) curve shows a lower proportion of breakdown and a residual weight stability at temperatures above 1000oC, coinciding with the silica content in PKSAnp. This is comparable and consistent with known high temperature coating materials in previous literature.

Optical property discrepancies found between healthy and unhealthy skin cells using digital holographic microscopy with three wavelengths

Cancer and other health disorders can be differentiated by changes in cell optical properties such as their refractive index, thickness, and topology (height and width). Here, we employ three wavelengths simultaneously in digital holographic microscopy (3λ-DHM) to visualize the whole cell topology as 3D images through a numerical reconstruction algorithm applied to a hologram. By identifying the cell state and the changes in its optical properties, it is possible to discern between healthy and unhealthy cells. The simultaneous use of three wavelengths provides a rapid and straightforward quantitative reconstruction of the whole cell without the need for an unwrapping algorithm. This is a benefit over traditional methods, which often require complicated procedures. The performance of the approach was first validated in a known sample, a silicon dioxide thin film, where we were able to corroborate its refractive index with the values reported in the literature. Then the method was applied to fixed skin cells finding a refractive index of 1.3443 for healthy cells and 1.3246 for cells found in tumor tissue. We discuss and highlight differences based on the refractive index to demonstrate that the employed process can provide reliable information to distinguish characteristics between healthy and unhealthy cells.

Effect of carbon black and silicon dioxide nanoparticle exposure on corona receptor ACE2 and TMPRSS2 expression in the ocular surface.

The Coronavirus disease 2019 (COVID-19) pandemic has led to a global health crisis, including ocular symptoms, primarily targeting the Angiotensin-Converting Enzyme 2 (ACE2) receptor. PM2.5 air pollution may increase infection risk by altering ACE2 expression. Silicon Dioxide (SiO2) and carbon black (CB), major components of PM2.5 from sands and vehicle emissions, were studied for their effects on ACE2 and Transmembrane Protease Serine 2 (TMPRSS2) expression in corneal and conjunctival cells, and ocular tissues. Human corneal epithelial cells (HCECs) and conjunctival epithelial cells (HCjECs) were exposed to nanoparticles (NPs) for 24 hours, assessing viability via WST-8 assay. TNF-α, IL-6, and IL-1β levels in the medium were measured. An in vivo rat study administered NPs via eye drops, with Rose Bengal staining to evaluate damage. ACE2, TMPRSS2, and Angiotensin II (AngII) protein expressions were quantified by Western blot. ACE2 expression in HCjECs increased with NP exposure, while it decreased in HCECs. CB exposure increased TNF-α, IL-6, and IL-1β levels in HCECs. In vivo, corneal exposure to CB decreased ACE2 expression, whereas conjunctival exposure to SiO2 increased ACE2 expression. These changes suggest that SiO2 exposure may increase the risk of COVID-19 through the ocular surface, while CB exposure may decrease it.

Passivation Effect of Rock-Salt Nitride Materials on a Planar p-Si Photocathode for Solar Water Reduction.

Photoelectrochemical water splitting, which uses sunlight to produce clean hydrogen fuel, is gaining traction with rising concerns about fossil fuels and pollution. Silicon (Si) photocathodes are promising for this process due to their light absorption and favorable band alignment for hydrogen production. However, limitations such as reflectance, low photovoltage, and rapid photocorrosion hinder their overall performance and stability. An interfacial insulating layer such as SiOx ensures superior durability to p-Si photocathodes. However, the inherent heterogeneity and intrinsic defects pose challenges to effective surface passivation. This study investigates the challenges of photocorrosion and utilization of a thin titanium nitride (TiN) passivation layer deposited using direct-current magnetron sputtering to protect the native silicon oxide (SiOx) layer. Additionally, a molybdenum oxynitride (Mo(O,N)x) bifunctional layer is employed to enhance both the electrocatalytic activity and durability of the photocathode. The presence of oxygen and nitrogen within this cocatalyst layer modifies the surface chemistry of the p-Si photocathode, promoting favorable interfacial interactions with electrolyte species during PEC reactions. This modification facilitates efficient charge transfer processes and accelerates reaction kinetics, ultimately optimizing the performance and operational lifetime of the photocathode. The resulting Mo(O,N)x/TiN/p-Si photocathode exhibited a remarkable onset potential of +0.46 VRHE in harsh acidic conditions under simulated sunlight (AM 1.5G illumination, 100 mW·cm-2). Notably, the photocathode demonstrated exceptional long-term stability exceeding 140 h, highlighting the combined TiN passivation and Mo(O,N)x cocatalyst as a protection strategy.

Recovery and Size-Tuning of Amorphous Silica from Geothermal Scales in Batangas, Philippines

Scale deposits in geothermal power plants are well-known potential sources of minerals. Extensive research in mineral recovery is crucial due to the considerable variability in scale composition and geochemistry based on location. Geothermal scales from Batangas, Philippines, were used to synthesize size-modified amorphous silica (SiO2) via sol-gel method. Initial analyses employing x-ray fluorescence spectroscopy (XRF), total dissolved solids (TDS), electrical conductivity (EC), and pH measurements confirmed that the scale is rich in silica and salts at neutral pH. Then, the effect of varying scale concentration, precipitation pH, and aging time on the particle size distribution of recovered amorphous silica were investigated. Dynamic light scattering (DLS) for particle size analysis (PSA) revealed that the sample with 2.5% (w/v) scale precursor in NaOH and precipitated until pH 10 had the lowest average cumulant diameter (1.66 μm). Moreover, the synergy of precipitation pH and aging time was found to significantly affect the polydispersity index and cumulative diameter of precipitated SiO2 based on 23 factorial ANOVA at 0.05 significance level. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed that the precipitates were amorphous SiO2 with spherical morphology. This study proves the viability of utilizing geothermal scales from Batangas, Philippines for the synthesis of amorphous SiO2 with controlled particle size, which is a potential filler for composite materials.

Study on the Mechanism of Bubble Defects in the PECVD Amorphous Silicon Films on Dielectric Substrate

The amorphous silicon (a-Si) grown by plasma enhanced chemical vapor deposition (PECVD) has been widely applied in advanced semiconductor devices. However, it still suffers from the bubble defects when the deposition temperature goes above 450 °C. In this work, we have investigated the influence of underlying materials on the formation of bubbles of a-Si. The a-Si was deposited on different dielectric substrates, including silicon nitrides (SiN) and silicon dioxide (SiO2), using PECVD technique at a substrate temperature of 500 °C. A large number of bubbles of the a-Si has been observed on the thermal ALD deposited SiN underlayer, and some of them even burst. In contrast, no bubble defects were observed at the a-Si grown on PECVD SiN and PECVD SiO2 films. Such deviation may be attributed to the quality of the underlying material, which induces the H/H2 diffusion during the growth of a-Si and results in bubbles. A solution based on the model has been used to suppress the formation of such bubbles. An inserting layer of SiO2 was introduced in between SiN and a-Si to improve the density of the lower layer material and the adhesion between the two materials. As a result, there is no bubble defects at the surface of a-Si observed using optical microscope. Our work reveals the mechanism of the formation of bubble defects and paves a new method to eliminate the bubbles defects and to form high-quality a-Si, which shows potential in the manufacture of semiconductor devices.

Ultralight SiO2 Nanofiber-Reinforced Graphene Aerogels for Multifunctional Electromagnetic Wave Absorber.

The high-efficiency utilization of two-dimensional (2D) graphene layers for developing durable multifunctional electromagnetic wave (EMW) absorbing aerogels is highly demanded yet remains challenging. Here, renewable, low-density, high-strength, and large-aspect-ratio ceramic silicon dioxide (SiO2) nanofibers were efficiently prepared to assist in the preparation of ultralight yet robust, highly elastic, and hydrophobic graphene aerogels using facile, scalable freeze-drying followed by a carbonization approach. The ceramic nanofibers efficiently prevent the agglomeration of graphene and enhance interfacial interactions, significantly promoting mechanical strength. In addition to the high conduction loss capability derived from the interconnected graphene network, high interfacial polarization derived by abundant heterogeneous interfaces is accomplished for the three-dimensional (3D) hybrid aerogels. The hybrid aerogels thus showcase excellent EMW absorption performance, involving a minimum reflection loss of -74.5 dB at 1.8 mm and an effective absorption bandwidth of 5.7 GHz, comparable to those of the best EMW absorbers. Furthermore, the integration of one-dimensional SiO2 and 2D graphene into 3D hybrid aerogels enables remarkable photothermal antibacterial, photothermal oil absorption, and thermal insulation performances. This work thus provides a type of ultralight ceramic/graphene aerogel with a high-efficiency utilization of graphene for accomplishing high-performance multifunctional applications.

Multifunctional Temporary Dental Nanofillers Enhanced with Synergistically Active Chlorine-Containing Molecules against Streptococcus mutans and Its Effects on Oral Epithelial Cells.

Temporary dental fillers are critical for safeguarding teeth during the period between caries removal and permanent restoration. However, conventional fillers often lack sufficient antimicrobial properties to prevent bacterial colonization. To address this issue, the study researches on the development of antimicrobial Temporary Dental Nano-Fillers (TDNF) capable of targeting multiple cariogenic pathogens, including Streptococcus mutans, Lactobacillus casei, Candida albicans, and mixed-species planktonic cells/biofilms, which play a significant role in the progression of dental caries. The TDNF was formulated using a combination of Chloramine-T (CRT) and Cetylpyridinium Chloride (CPC), both known for their antimicrobial efficacy, and embedded in a nanoparticle matrix of hydroxyapatite (HAP) and silicon dioxide (SiO2). The synergistic antimicrobial effect of CRT and CPC, with MIC90 values of 12.5 and 6.25 ppm, respectively, displayed potent activity against S. mutans. Proteomic analysis, including gene ontology and protein-protein interaction network evaluations, further confirmed significant disruptions in S. mutans metabolic and stress response pathways, highlighting the bactericidal effectiveness of the formulation against S. mutans. Additionally, the formulation demonstrated sustained antimicrobial efficacy against other cariogenic pathogens such as L. casei, C. albicans and mixed-species planktonic cells and biofilms over a 16-day period. The TDNF (HAP+SiO2+CRT+CPC matrix) exhibited superior mechanical properties with a compressive strength of 237.7 MPa, flexural strength of 124.3 MPa, and shear bond strength of 52 MPa. Biocompatibility tests conducted on human oral squamous carcinoma cells (OECM-1) indicated over 95% cell viability, affirming its safety for preclinical or clinical applications. The multifunctional TDNF developed in this study successfully combines mechanical reinforcement with broad-spectrum antimicrobial efficacy, offering a promising interim solution in dental restorations. Its ability to protect against microbial colonization, while maintaining structural stability, positions it as an effective temporary material that enhances patient outcomes during the period before permanent restoration.

Vertical silicon nanowedge formation by repetitive dry and wet anisotropic etching combined with 3D self-aligned sidewall nanopatterning

Three-dimensional (3D) stacking of nano-devices is an effective method for increasing areal density, especially as downscaling of lateral device dimensions becomes impractical. This stacking is mainly achieved through plasma processing of stacked layers on top of a silicon (Si) substrate, which offers process flexibility but poses challenges in obtaining vertical sidewalls without plasma induced damage. A novel wafer-scale fabrication method is presented for realizing sub-200 nm vertically stacked Si nanowedges at the wafer scale, using iterative dry etching, wet anisotropic etching, and thermal oxidation. This approach forms nanowedges by the slow etching {111} Si planes, resulting in smooth surfaces at well-defined angles. A silicon nitride (Si3N4) hard mask is used in an iterative (etch-and-deposit) process, with its thickness determining the number of process iterations. By optimizing etch selectivity during dry etching and/or increasing the initial Si3N4 thickness, the number of process iterations can be increased. The periodicity of the nanowedges can be adjusted by varying the etch time of both dry and wet anisotropic etching. A thin silicon dioxide (SiO2) layer (∼6 nm) is grown on the nanowedges during each iteration. 3D sidewall patterning at the sub-20 nm scale is achieved using corner lithography and local oxidation of Si to selectively open the concave corners. Rhombus-shaped structures are formed at each concave corner after wet anisotropic etching of Si. This novel technology platform will allow for the 3D fabrication of high-density nanodevices for electronic, fluidic, plasmonic, and other applications.

The extraction of inorganic phase-change materials from sugar industry wastes with the purpose of solid waste management

ABSTRACT This study focused on the feasibility of identifying and recycling inorganic phase-change materials (PCMs) from sugar industry wastes in two cities of Qazvin and Hamadan in Iran. In this study, dry sugar beet pomace, sugar beet pomace, sugar beet molasses, leaves and plant residues of sugar beet and sugarcane bagasse were investigated. The inorganic materials were identified by X-ray Diffraction (XRD), thermal characteristics were determined by differential scanning calorimetry (DSC), and morphological characteristics were determined by scanning electron microscopy (SEM). Additionally, physical and thermal properties of molasses and bagasse samples were analyzed to determine their suitability as inorganic PCMs. The results of this study demonstrated that molasses and bagasse have the potential to be used as mineral PCMs in thermal energy storage applications. The results of this study demonstrated that in the wet sugar beet pomace the highest and lowest concentrations of inorganic PCMs were silicon dioxide (SiO2) and sodium chloride (NaCl), respectively. Moreover, the highest calcium fluoride (CaF₂) composition was reported in dry sugar beet pomace. In the samples of leaves and residues of sugar beet and sugarcane bagasse, the highest concentration of was NaCl. The detection and recycling of mineral PCMs from sugar industry wastes offer a sustainable solution for waste management and provide a renewable source of thermal energy storage materials. Implication Statement This study demonstrated the potential for the extraction of inorganic phase-change materials from sugar industry wastes as a means of solid waste management. By repurposing these materials, we can reduce the environmental impact of sugar production and contribute to sustainable practices in the industry.

Towards Achieving Circular Economy in the Production of Silica from Rice Husk as a Sustainable Adsorbent

The growing concern over water pollution and waste management requires innovative solutions that promote resource efficiency within a circular economy. This study aims to utilize rice husk (RH) as a sustainable feedstock to develop highly porous silica particles and generate valuable by-products, addressing the dual challenges of waste reduction and water contamination. We hypothesize that optimizing the production of amorphous silica from acid-washed RH will enhance its adsorptive properties and facilitate the concurrent generation of bio-oil and syngas. Amorphous silica particles were extracted from acid-washed RH with a yield of 15 wt% using a combination of acid washing at 100 °C, pyrolysis at 500 °C, and calcination at 700 °C with controlled heating at 2 °C/min. The optimized material (RH2-SiO2), composed of small (60–200 nm) and large (50–200 µm) particles, had a specific surface area of 320 m2/g, with funnel-shaped pores with diameters from 17 nm to 4 nm and showed a maximum cadmium adsorption capacity of 407 mg Cd/g SiO2. Additionally, the pyrolysis process yielded CO-rich syngas and bio-oil with an elevated phenolic content, demonstrating a higher bio-oil yield and reduced gas production compared to untreated RH. Some limitations were identified, including the need for bio-oil upgrading, further research into the application of RH2-SiO2 for wastewater treatment, and the scaling-up of adsorbent production. Despite the challenges, these results contribute to the development of a promising adsorbent for water pollution control while enhancing the value of agricultural waste and moving closer to a circular economy model.

Investigation of Pozzolan Activity, Chemical and Granulometric Composition of Micro- and Nanosilicon of the Bratsk Ferroalloy Plant

The article presents the findings of a study conducted on a range of microsilicon grades selected at the Bratsk Ferroalloy Plant. The following analytical techniques were employed: X-ray fluorescence analysis, X-ray diffraction analysis, a granulometric composition study, and pozzolanic properties. The grades of the investigated microsilicon are compared with the furnace grade and the grade of the produced ferrosilicon. The findings of the research conducted at the Bratsk Ferroalloy Plant indicate that the microsilicon produced at the facility is suitable for use as an additive in the production of tires, artificial irregularities, and other rubber products intended for use on roads. In such applications, the quality and durability of the material are determined by its ability to withstand abrasion and wear. Therefore, it is essential to utilize the purest, most amorphous, and most finely dispersed silicon dioxide. The gas cleaning device GCD-4 FeSi-75 exhibits the greatest number of these parameters among the samples presented. Different samples of microsilica have a color from white to dark gray. The chemical and granulometric compositions were determined. The pozzolan activity was investigated. Based on the conducted analyses, it is possible to draw conclusions about the properties of materials and the potential for use in the construction industry for concretes of various values. The results of the analyses indicate that silicon dioxide with GCD-4 FeSi-75 is suitable for use in critical concrete structures. The quality of the silicon dioxide with GCD-4 FeSi-75 can be compared with that of Elkem 971. It is recommended that all the studied samples be employed as modifiers for cast iron, with the GCD-4 FeSi-75 sample being the optimal choice for testing in steels. The utilization of this modifier enables a reduction in the consumption of FeSi, exerting both an alloying and modifying effect on the melt. However, it is essential to emphasize the necessity for technological selection of the method of administration, as the powder, in its pure form, is susceptible to combustion and is not readily digestible. The quality of such a modifier, with a stable guaranteed effect, is comparable to the use of FeSi. Silicon dioxide plays an essential role in the production of refractories. The primary criteria for this industry are purity, the minimum content of the crystalline phase, and the activity of the material. It is recommended that the material from GCD-4 FeSi-75 be used in the production of refractories.

Process optimization for silica dissolution from e-waste as a sustainable step towards bioremediation

High-purity silicon represents a major component of e-waste. Current methods for e-waste remediation are energy-intensive or chemical-based. Herein, a microbial route for silica dissolution from e-waste was explored, as microbes play an active role in balancing the silicon cycle. The study focused on an isolated silicate solubilizing bacterium (SSB) Staphylococcus gallinarum CON2 for its capability to solubilize silica in e-wafers and silicon dioxide chips. Bacterial silica dissolution was optimized for various parameters using Plackett Burman design. Heteropoly acid method was standardized for quantitative analysis of dissolved silica. Bacterial treatment of e-wafers from solar panels and laboratory-coated silicon dioxide chips were carried out under pre-optimized conditions. For comparison purpose, another SSB was also evaluated for e-waste remediation at similar conditions. The amount of released silicic acid after e-waste treatment was determined, and its presence was further confirmed by FTIR analysis. Etching and loosening of silicon dioxide particles on the surface were observed under SEM at different magnifications. The novel potential of silica dissolution from e-waste by isolated S. gallinarum CON2 was confirmed. A significant difference in the actions of both silicate solubilizing bacteria on the topography of the e-waste specimens was observed.

Synthesis of Novel Graphene Oxide-chitosan-silicon Dioxide Nanocomposite Embedded in Polysulfone Membrane for Oily Water Treatment

Oil and gas exploration activities result in generation of large quantities of produced water. Globally, for each barrel of oil, three barrels of produced water is generated. The oil content in produced water can vary between 3 and 20% depending on the location and age of the hydrocarbon well. Due to their hydrophobic nature, conventional hydrophobic polymeric membranes struggle to effectively separate oil from produced water. In this work, an innovative strategy is suggested by employing a hydrophilic/super-oleophobic nanocomposite to develop novel polymeric membranes able to effectively separate oil content from produced water without negatively affecting the other membrane properties such as the total flux and fouling. Graphene oxide-chitosan-silicone oxide (GO-CH-SiO2) nanocomposite was synthesized by functionalizing graphene oxide (GO) with chitosan (CH) and silicon dioxide (SiO2). To improve the membrane flux, anti-fouling propensity, and oil rejection, the synthesized nanocomposites were doped in the polysulfone membranes matrix. The effect of GO-CH-SiO2 concentration, GO:CH ratio, and GO-CH:SiO2 ratio on the performances of developed membranes was experimentally assessed, and morphology of the synthesized membrane was investigated using appropriate characterization techniques. The experimental results showed that the membrane with GO:CH of 1:2 and GO-CH: SiO2 ratio of 1:6.5 showed the highest pure water permeation flux of 28.35 LMH/bar with a comparable flux recovery rate of 76% and oil rejection efficiency of 98.5%. The study’s findings underscore the potential of GO-CH-SiO2 nanocomposite membranes for oil–water separation research, presenting a promising solution for treating produced water in the oil and gas industry. Further research is needed to scale up this technology and improve membrane performance by optimizing the nanocomposite composition and conducting long-term performance tests.

Formation of Superhydrophobic Coatings Based on Dispersion Compositions of Hexyl Methacrylate Copolymers with Glycidyl Methacrylate and Silica Nanoparticles

In the last decade, the task of developing environmentally friendly and cost-effective methods for obtaining stable superhydrophobic coatings has become topical. In this study, we examined the effect of the concentrations of filler and polymer binder on the hydrophobic properties and surface roughness of composite coatings made from organic–aqueous compositions based on hexyl methacrylate (HMA) and glycidyl methacrylate (GMA) copolymers. Silicon dioxide nanoparticles were used as a filler. A single-stage “all-in-one” aerosol application method was used to form the coatings without additional intermediate steps for attaching the adhesive layer or texturing the substrate surface, as well as pre-modification of the surface of filler nanoparticles. As the ratio of the mass fraction of polymer binder (Wn) to filler (Wp) increases, the coatings show the lowest roll-off angles among the whole range of samples studied. Coatings with an optimal mass fraction ratio (Wn/Wp = 1.2 ÷ 1.6) of the filler to polymer binder maintained superhydrophobic properties for 24 h in contact with a drop of water in a chamber saturated with water vapor and exhibited roll-off angles of 6.1° ± 1°.

Revolutionizing Dye Sensitized Solar Cells – Impact of Silicon Dioxide Purity Derived from Coal Fly Ash for Enhanced Photoelectric Performance

Revolutionizing Dye Sensitized Solar Cells – Impact of Silicon Dioxide Purity Derived from Coal Fly Ash for Enhanced Photoelectric Performance

Preliminary investigation on spent garnet as a novel supplementary cementitious material

The escalating global demand for cement, a fundamental material in infrastructure development, has exacerbated environmental challenges, particularly through significant carbon dioxide (CO₂) emissions, which account for approximately 8.3 % of global anthropogenic CO₂ output. This research explores the potential of spent garnet powder, a byproduct of abrasive water jet machining, as a sustainable supplementary cementitious material (SCM) to mitigate these impacts. The spent garnet powder, characterized by a high concentration of silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃), was subjected to rigorous analysis. X-ray Fluorescence (XRF) confirmed its chemical suitability for pozzolanic applications, while laser particle size analysis revealed a finer granulometry relative to Ordinary Portland Cement (OPC), which is advantageous for enhancing pozzolanic reactivity. Scanning Electron Microscopy (SEM) demonstrated the angular and irregular morphology of the garnet particles, which is conducive to improved interfacial bonding within the cement matrix. X-ray Diffraction (XRD) identified active mineral phases that are critical for promoting pozzolanic reactions, and Thermogravimetric Analysis (TGA) demonstrated the material’s superior thermal stability, with minimal decomposition at elevated temperatures. Fourier Transform Infrared Spectroscopy (FTIR) identified strong silicon-oxygen (Si-O) and aluminum-oxygen (Al-O) bond structures, indicative of robust pozzolanic potential. The Strength Activity Index (SAI) and Frattini tests further substantiated the pozzolanic activity, revealing that a 10 % replacement of OPC with SGP not only enhances compressive strength but also meets the stringent requirements of ASTM C618. Additionally, the economic analysis underscores the cost-effectiveness of utilizing spent garnet powder, presenting a viable strategy for reducing both production costs and CO₂ emissions in the cement industry. This study conclusively positions spent garnet powder as a highly promising supplementary cementitious material, with significant implications for advancing sustainable construction practices and reducing the environmental footprint of cement production.

Mechanically robust and durable polyurethane-based superhydrophobic coating containing silica nanoparticles derived from hydrothermal assisted sol–gel method

In the current study, a suspension of hydrothermal assisted sol–gel synthesised superhydrophobic silica nanoparticles (h-SNPs) are sprayed over apartially cured polyurethane (PUR) surface on aluminium substrate. The surface exhibited superhydrophobic (SH) property with a water contact angle of 166 ± 2° and awater sliding angle of < 5°. X-ray diffraction study confirmed the formation of amorphous silica nanoparticles. The particle size determined by field emission scanning electron microscope is about 19–21 nm. The roughness of the coating is 3.5 µm as characterised using a surface profilometer. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy investigations indicated the presence of urethane linkages from PUR and siloxane stretching from h-SNPs. The adhesion of the coating tested with a cross-hatch cutter as per ASTM D3359 shows a rating of 5B. The coating qualified mandrel bend test conducted according to ASTM D255. No cracks are observed at the deformed areas and water drops roll off the surface, demonstrating the integrity of the coating and its superhydrophobicity. The coating exhibits high robustness as evident from sandpaper abrasion and tape peel tests. When compared to superhydrophobic polyurethane (SH PUR) coating developed using commercial silica as reported in our previous work, the developed h-SNPs coating is much more durable as confirmed by accelerated weathering test and anti-icing test. The SH coating also exhibits superhydrophobicity even after 200 h of accelerated weathering test and 16 de-icing cycles. The coating withstands 15 days of water immersion and also displays self-cleaning property.

Bioavailability Improvement by Atomic Layer Coating: Fenofibrate A Case Study

Biopharmaceutical Classification Systems (BCS) class II drugs show poor solubility and high permeability in the body. Fenofibrate (FF) is a classic example of a BCS class II drug, used to treat high cholesterol and triglyceride (fat-like substances) levels in the blood. Atomic layer coating (ALC) is a surface engineering technology adapted from the semiconductor industry, where metal oxides are coated one atomic layer at a time over the active pharmaceutical ingredients (API) particles. ALC coating was proven to improve the processability, alter the hydrophilicity, improve the stability, and fine-tune the release of drugs. Herein, we report the intervention of ALC coating in enhancing the bioavailability of a poorly water-soluble drug (fenofibrate) in the animal model. The physical properties of uncoated fenofibrate were compared with those of zinc oxide-coated and silicon oxide-coated fenofibrate. Following the application of the coatings, the structural integrity (both chemical stability and solid-state stability) of the active pharmaceutical ingredient (API) remained uncompromised, as corroborated by 1H NMR and powder X-ray diffraction analyses. Notably, zinc oxide-coated fenofibrate exhibited favorable flow characteristics, whereas no discernible enhancement in flow behavior was observed for silicon oxide-coated fenofibrate. The results from contact angle measurements suggest that the silicon oxide-coated fenofibrate exhibits superior wetting behavior, as indicated by a contact angle nearing 0°. The application of ALC demonstrates an enhanced dissolution rate when compared to the uncoated active pharmaceutical ingredient (API) while leaving its equilibrium solubility unaffected. Coating the API with silicon oxide improves particle hydrophilicity and wetting properties, whereas zinc oxide coating aids in particle de-agglomeration, thereby enhancing their interaction with an aqueous medium. In vivo bioavailability studies conducted on rodents and larger animal (dog) models indicate a substantial increase in bioavailability (approximately 2 times) for the silicon oxide-coated API in comparison to the uncoated API, as determined by the area under the curve (AUC). Furthermore, the Cmax values for the silicon oxide-coated API also demonstrate a significant increase (approximately 3 times) over the uncoated API. Notably, an oral subacute toxicity study of ALC silicon-coated fenofibrate revealed no toxic effects attributable to the coating. This study underscores the potential of ALC in augmenting the bioavailability of BCS(II) drugs.

Hydrate management strategies for CO2 injection into depleted gas reservoirs

Sequestering CO2 in depleted gas reservoirs using carbon capture, utilization, and storage technologies has emerged as a viable strategy for mitigating global carbon emissions. However, CO2 hydrate formation during injection processes is challenging and poses a risk to the operational integrity and efficiency of sequestration projects. This study investigated CO2 hydrate formation dynamics within silica gel environments that closely mimicked the median pore size of natural sandstone reservoirs, particularly targeting depleted gas fields in the East Sea of Korea. Integrating kinetic insights into experimental hydrate formation assessments and molecular dynamics simulations provided a comprehensive understanding of the CO2 hydrate formation mechanisms, as well as the formation dynamics and stability of the CO2 hydrates. For example, the hydrate formation kinetics were significantly reduced in the small pores, suggesting the feasibility of implementing more economical hydrate inhibitor injection strategies during CO2 injection. Moreover, this study evaluated the inhibitory effects of NaCl and methanol on CO2 hydrate stability by accurately measuring the three-phase (H-Lw-V) equilibria and employing silica gels (6 nm pore size). The presence of methanol and amorphous silica significantly impacted hydrate formation, with methanol potentially influencing the local structure around the hydrate phase and silica hindering hydrate growth through dynamic interactions with CO2 molecules. In addition, we elucidated the complex interplay between CO2, water, and methanol (hydrate inhibitor) within the constrained environments of porous media, offering strategic insights for the development of effective CO2 injection and sequestration strategies. Integrating molecular-level observations with real-world geological modeling presents a novel methodology for enhancing the safety, efficiency, and environmental sustainability of carbon capture and storage operations. The findings of this study provide critical insights into hydrate phase behavior, highlighting the importance of precise equilibrium determination under simulated reservoir conditions to effectively anticipate and mitigate hydrate formation challenges.