Unmodified Samples Research Articles

Mechanistic Understanding of Superior Methylene Blue Adsorption Capacity in a Novel g-C3N4 Modified Amorphous Na-Ca-Mg Silicate Adsorbent: Insights from Multinuclear Solid-State NMR Spectroscopy.

Silicate-based adsorbents offer significant advantages over traditional materials, particularly due to their superior thermal and chemical stability, enhanced regenerability, and the ability to endure more rigorous operating conditions. In this study, an amorphous Na-Ca-magnesium silicate adsorbent (SAAM) and its g-C3N4-modified counterpart (gCN-SAAM) were synthesized via alkali activation and a subsequent thermal process, respectively. The g-C3N4 modification resulted in a novel hybrid adsorbent with a remarkable methylene blue (MB) adsorption capacity of 420 mg g-1, four times higher than the unmodified sample, setting a new benchmark. Solid-state 29Si (MAS and CP/MAS), 1H MAS, and 13C CP/MAS NMR spectroscopy were used to investigate the complex structures of these adsorbents and their interactions with MB. The local structure of SAAM primarily consists of Q3 Si units, with minor Q0 and Q1 Si species, structural water, and Mg-OH sites. Exposure to MB caused an upfield shift in the 29Si CP/MAS spectrum and enhanced resonances in the high-field region, indicating MB interaction with Si sites. 1H MAS NMR spectra revealed significant interactions between water molecules in the geopolymer-like framework of SAAM and MB. The thermal treatment of SAAM with urea to produce gCN-SAAM enhanced the polymerization of Q3 Si species and increased the relative fraction of Q4 Si sites. This treatment also reduced the intensity of some Mg-OH units, showing interaction with g-C3N4. After MB adsorption on gCN-SAAM, NH2 groups of g-C3N4 disappeared, and shifts in the C2N-NHx and C3N sites indicated their involvement in adsorption, while Si sites remained intact. This thermal method creates a sustainable, cost-effective and efficient adsorbent for MB removal from wastewater. Multinuclear NMR spectroscopy provides detailed insights into the adsorbent's complex structure and MB interactions, potentially guiding the design of improved future adsorbents.

Tribological Properties and Wear Mechanism of Phenolic Resin Incorporated Rare Earth Oxides

Different proportions of rare earth oxides, specifically cerium oxide and yttrium oxide, were incorporated into phenolic resin-based friction materials to mitigate the thermal degradation of resin-based friction materials. The effects of these additives on the mechanical properties and tribological performance of resin-based friction materials were thoroughly investigated, and the microstructure and phase composition were characterized via field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The addition of rare earth oxides favorably improved the density, hardness, compression strength, and shear strength of the composites, with rare earth yttrium oxide dominating the hardness of the composites and cerium oxide dominating the compression strength of the composites, but changes in the ratio of the two had a small effect on their density, shear strength, and impact strength. Among them, the highest density, hardness, compressive strength, and shear strength of the modified sample could reach 2.310 g/cm3, 118 HRL, 187.5 MPa, and 43.5 MPa, respectively, and their properties were improved by 7.7%, 14.6%, 19%, and 51%, respectively, compared with the unmodified sample Y0. The incorporation of rare earth oxides was not conducive to the improvement of the fade friction coefficient and recovery friction coefficient of the composites, but was beneficial to the stabilization of the recovery friction coefficient of the composites and the reduction in their average wear rate, with the yttrium oxide-dominated matched samples focusing on high-temperature stability, and cerium oxide-dominated matched samples focusing on the antioxidant reduction property. The homogeneous dispersion and synergistic enhancement effect of the rare earth oxides in the matrix materials enhanced the structural integrity and densification of the matrix materials and improved the interfacial strength and surface wear resistance of the composites. The worn surface of the unmodified sample Y0 was mainly abrasive and thermal fatigue wear, the worn surface of the yttrium oxide-dominated matched samples Y1 and Y2 was mainly abrasive wear, and the worn surface of the cerium oxide-dominated matched samples Y3 and Y4 was mainly adhesive and thermal fatigue wear.

Photoactivated rose bengal-doped TiO2 nanoparticles modified fifth-generation adhesive on the survival rate of Streptococcus mutants and mechanical properties of tooth-colored restorative material to carious dentin.

Assessment of the antimicrobial, micro tensile bond strength (μTBS), and degree of conversion (DC) of fifth-generation adhesive modified using photoactivated 0.5% rose bengal (RB) and photoactivated RB-doped titanium dioxide nanoparticles (TiO2NPs) in different concentrations (2% and 5%) as compared with the unmodified adhesive bonded to the carious affected dentin (CAD). Forty mandibular molars with caries progression up to the middle third of the dentin, as per the International Caries Detection and Assessment System (ICDAS) score of 4 and 5 were included. Specimens were divided into four groups based on etch and rinse adhesive (ERA) modification group 1: unmodified ERA, group 2: photoactivated 0.5% RB photosensitizer (PS) modified ERA, group 3: photoactivated RB-doped 2 wt% TiO2NPs adhesive, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive. Followed by adhesive and composite restoration on the CAD surface. All the specimens were thermocycled and an assessment of μTBS and failure pattern analysis was performed. The antibacterial potency of RB and RB-doped TiO2NPs (2% and 5%) followed by their activation using visible light against Streptococcus mutans (S.mutans) were tested. The survival rate of S.mutans was assessed using the Kruskal-Wallis test. The analysis of μTBS involved the use of ANOVA, followed by a post-hoc Tukey honestly significant difference (HSD) multiple comparisons test. Group 1 (Unmodified ERA) (0.52 ± 0.31 CFU/mL) treated samples unveiled the highest means of bacterial survival and lowest μTBS (11.32 ± 0.63 MPa). Nevertheless, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest outcomes of S.mutans survival (0.11 ± 0.02 CFU/mL) and highest bond strength (18.76 ± 1.45 MPa). The photoactivated RB-doped 2 wt% TiO2NPs in adhesive demonstrated promising enhancements in both μTBS and antibacterial efficacy against S.mutans. However, it is noteworthy that this modification led to a decrease in the DC of the adhesive. RESEARCH HIGHLIGHTS: Unmodified ERA-treated samples unveiled the highest bacterial survival and the lowest μTBS. Photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest S.mutans survival rate and highest bond strength. DC decreased with an increase in concentration of TiO2.

Study on the corona aging characteristics of KH570-modified nano-Al(OH)₃ cycloaliphatic epoxy resin in hygrothermal environments

Cycloaliphatic epoxy(CE) resin may experience insulation degradation and pose a threat to the safe operation of equipment when used in high-temperature and high-humidity environment. Therefore, to enhance the corona aging resistance of CE under harsh conditions, this study incorporated γ-methacryloxypropyltrimethoxysilane-modified (KH570) nano-Al(OH)₃ with varying content into the CE. The samples were subjected to corona aging tests under different hygrothermal conditions. The corona aging characteristics of CE in high-temperature and high-humidity environments were analyzed using scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), resistivity, and dielectric loss measurements before and after modification. The results indicate that as humidity increases, the unmodified samples develop pores and cracks on the surface, which leads to an increased water absorption rate and internal hydrolysis. However, with the increase in filler content, the water absorption channels on the sample surface decrease, effectively suppressing chemical moisture absorption and maintaining the stability of the internal chemical structure. Among the various filler contents, the effect was most pronounced at 3%wtCE. Under 65 % RH conditions, the volume/surface resistivity increased by 27.28 % and 26.9 %, respectively, the leakage current decreased by 64.85 %, while the dry and wet breakdown voltages increased by 9.3 kV and 6.85 kV, respectively, and the dielectric loss variation with humidity was reduced. Compared to the unmodified material, KH570-modified nano-Al(OH)₃ has significantly improved the insulation and aging resistance properties of the material under hot and humid corona aging conditions. This study provides a reference for improving the performance of epoxy resins under high temperature, high humidity, and strong electric field conditions.

Optimizing Charge Separation and Transport: Enhanced Photoelectrochemical Water Splitting in α-Fe2O3/CZTS Nanorod Arrays

This study explores the enhancement of α-Fe2O3 (hematite) nanorod arrays for photoelec-trochemical applications by constructing a Cu2ZnSnS4 (CZTS) heterojunction. While α-Fe2O3 offers good stability, a low cost, and environmental benefits, its efficiency is limited by slow oxygen evolution kinetics, high carrier recombination rates, and low conductivity. By introducing CZTS, a material with strong light absorption and charge transport properties, we enhance the separation of photogenerated charge carriers, reduce charge transfer resistance, and increase the carrier concentration, thereby boosting the overall photoelectrochemical performance. The experimental results show that a modified FC-15 photoanode achieves a photocurrent density of 3.40 mA/cm2 at 1.60 V vs. RHE, a substantial increase compared to 0.40 mA/cm2 for unmodified α-Fe2O3. Band gap analysis reveals a reduced band gap in the FC-15 material, enhancing light absorption and boosting the photoelectrocatalytic performance. In photoelectrochemical water-splitting tests, the FC-15 photoanode achieves a hydrogen production rate of 41.6 μmol/cm2/h, which is significantly improved over the unmodified sample at 5.64 μmol/cm2/h. These findings indicate that the CZTS/α-Fe2O3 heterojunction effectively promotes charge separation, enhances charge transport, and improves light absorption, substantially increasing photocatalytic efficiency. This heterojunction approach offers new insights and technical strategies for developing photocatalytic materials with potential applications in renewable energy.

Investigation of Combined Aging and Mullins Stress Softening of Rubber Nanocomposites.

The present study investigated the effects of thermal aging, ultraviolet radiation (UV), and stress softening on the performance properties of rubber modified with Cloisite Na+ or Cloisite 20A. Tensile strength (TS), strain at break (SB), modulus, and the retention coefficient were measured before and after aging. Results showed that TS and SB decreased by about 50% after 7 days of aging for all tested samples due to the breakage of the chemical bonds between rubber and nanoparticles. The modulus at 300% elongation increased by 20%, 15%, and 7% after thermal aging for the unmodified sample, nanocomposites with Cloisite Na+, and Cloisite 20A, respectively. The shape retention coefficient of all samples was not affected by heat, except for the virgin rubber sample, which exhibited a decrease of about 15% under thermal aging. The virgin matrix and nanocomposites showed different values of aging coefficient during thermal aging and UV radiation. The dissipated energy of samples that were aged after stretching was slightly higher than that of samples that were aged after stretching due to the breakdown of the bonds within the nanocomposites. Loading-reloading energy results showed that the level of stress softening was lower when Mullins was applied after the aging of the samples. Differential scanning calorimetry results indicated a slight decrease in Tg1 in the aged and stretched samples and an increase in the temperature of the first endothermic peak due to the addition of nanofillers in the stretched and aged samples. Thermogravimetric analysis revealed that all tested samples exhibited similar thermograms, regardless of their state of stretching or aging. Scanning electron microscopy analysis showed that the fracture surface of the virgin unaged sample was rough with some holes, while it was flatter and less rough after aging.

Interphase mechanics vs chemical compatibility: Generating a deformable PA6-carbon fiber interphase

Good interfacial adhesion is typically correlated to obtaining the best tensile/flexural performance for carbon fibre-reinforced composites. The nature or even presence of the interphase, a localized region around the fibre-matrix junction, is often discussed but notoriously difficult to visualize and characterise. Here, a surface-initiated electro-polymerization approach to covalently graft either polyacrylamide or polygylcidyl methacrylate to the carbon fibres was used. This was followed by continuous melt compounding into the polyamide-6 matrix prior to injection moulding. Analysis via X-ray photoelectron spectroscopy (XPS) coupled with topological/visual study through scanning electron microscopy (SEM), showed distinct surface changes after modification and at the composite fracture surface. Additionally, mechanical (tensile, flexural, and tribological characteristics) and thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)) investigations were performed. The results showed that the unmodified CF samples exhibit higher tensile and flexural modulus than the modified CF samples. However, the wear rate has been significantly decreased for modified CF samples. SEM of fractured composite surfaces showcased a clear interphase region surrounding the fibre, highlighting the importance of interphase/interphase mechanics in the design of optimal composite interfaces.

Developing an efficient anticorrosive system through advanced modification of plasma-electrolyzed MgO with CeNiLDH complexed with V₂O₅ nanoparticles and (2E)-But-2-enedioic acid

Advanced hybrid materials with unique properties are essential for addressing the demands of increasingly complex applications. Despite their importance, the self-assembly of layered double hydroxides (LDH) with metallic oxide nanoparticles and dicarboxylic acids is constrained by a limited understanding of the formation mechanisms and difficulties in evaluating their anticorrosive performance. In this study, we developed a novel anticorrosive system by intercalating CeNiLDH with a complex of vanadium pentoxide (V₂O₅) nanoparticles and (2E)‑but-2-enedioic acid ((2E)-BDA) on a MgO layer created through plasma-electrolysis of AZ31 Mg alloy. This system was compared with LDH films intercalated with either V₂O₅ or (2E)-BDA alone. The intercalation of LDH with V₂O₅ and (2E)-BDA resulted in a flower-like structure, while modification with their complex led to a more compact, cloud-like formation. These cloud-like structures, driven by enhanced absorption and robust hydrogen bonding throughout the hierarchical network, effectively suppress corrosion by delaying the movement of corrosive anions. This was reflected in a polarization resistance of 1.51 × 10¹⁰ Ω·cm², which is approximately two orders of magnitude times higher than the resistance of the unmodified LDH film (3.41 × 10⁸ Ω·cm²). Additionally, the corrosion current density (icorr) of the VOBDA sample showed a decrease by four orders of magnitude compared to the unmodified LDH sample, emphasizing the superior anticorrosive performance of this hybrid coating. Density functional theory (DFT) was used to elucidate the bonding and formation mechanisms between LDH and the inorganic-organic complex.

Development of Technologies for Processing Polypropylene Foil Waste and Their Use in the Production of Finished Products.

This work aims to assess the possibility of using packaging industry waste to modify polypropylene products (PPs). The products were made in the form of extruded foil and injected samples. The products were produced using regranulate made of polypropylene cast foil. Maleic anhydride-modified polypropylene (MAPP) and polyolefin elastomer (POE) with a glycidyl ester functional group were used to modify the polypropylene. The samples were produced based on 50% foil waste reground and 50% pure PP. The rheological properties of the blends were assessed using the melt mass flow rate (MFR) technique; thermal properties using the differential scanning calorimetry method (DSC). The products manufactured using the injection molding method were subjected to an analysis of mechanical properties, such as tensile strength and impact strength. Also, in the case of film samples, tensile strength was assessed. Color-change assessments with CIE L*a*b* were carried out for all materials. Injection-molded products based on recycled metallized cast foil showed favorable mechanical properties such as tensile strength (1 MAPP = 26.7 MPa; 2 MAPP = 27.1 MPa), which was higher than the original material (cPP = 20.7 MPa). Also, for the films produced from regrind, the tensile strength was at a level similar (1 MAPP = 24.6 MPa; 2 MAPP/POE = 25.1 MPa) to the films extruded from virgin materials (cPP = 24.9 MPa). The introduction of a POE additive to the blends resulted in increased impact strength (1 MAPP/POE = 31 kJ/mol; 2MAPP/POE = 18 kJ/mol; 3 MAPP/POE = 11 kJ/mol) in relation to unmodified samples (cPP = 7 kJ/mol). The introduction of a POE additive to the tested mixtures improved the impact strength of the injected products by almost 4 times for sample 1 MAPP/POE and 2.5 times for sample 2 MAPP/POE in comparison to virgin cPP. These studies confirmed that foil waste can be successfully used to modify polypropylene products shaped both in the injection and extrusion processes.

Oxygen vacancy induced defect dipoles in BiVO4 for photoelectrocatalytic partial oxidation of methane

A strong driving force for charge separation and transfer in semiconductors is essential for designing effective photoelectrodes for solar energy conversion. While defect engineering and polarization alignment can enhance this process, their potential interference within a photoelectrode remains unclear. Here we show that oxygen vacancies in bismuth vanadate (BiVO4) can create defect dipoles due to a disruption of symmetry. The modified photoelectrodes exhibit a strong correlation between charge separation and transfer capability and external electrical poling, which is not seen in unmodified samples. Applying poling at −150 Volt boosts charge separation and transfer efficiency to over 90%. A photocurrent density of 6.3 mA cm−2 is achieved on the photoelectrode after loading with a nickel-iron oxide-based cocatalyst. Furthermore, using generated holes for methane partial oxidation can produce methanol with a Faradaic efficiency of approximately 6%. These findings provide valuable insights into the photoelectrocatalytic conversion of greenhouse gases into valuable chemical products.

Glass fiber waste as a potential bitumen modifier and stabilizing agent in asphalt mixture.

The deterioration of Malaysia's flexible road pavements due to rutting and moisture damage presents a critical problem. Meanwhile, disposing of glass fiber wastes from manufacturing process further worsens environmental concerns. This research explores the feasibility of using glass fiber wastes as bitumen modifiers and stabilizers in stone mastic asphalt (SMA). The performance of SMA14 incorporating glass fiber waste using wet method and dry method were compared in this study. Bitumen 60/70 PEN was modified with varying percentages of glass fiber waste namely, 0.5%, 1.0%, 1.5%, and 2.0% by weight of bitumen. The SMA14 mixture was modified with glass fiber waste at 0.3% by the weight of total mixture. The physical and rheological characteristic of modified bitumen binder were assessed using penetration, softening point, storage stability, viscosity, and dynamic shear rheometer (DSR) tests. The Marshall properties and performance of the SMA14 mixture incorporating glass fiber waste were evaluated. The findings demonstrate that glass fiber waste-modified bitumen exhibits enhanced penetration, softening point, viscosity, and rutting resistance compared to the unmodified sample. Adding glass fiber waste using dry method shows significant resistance to abrasion and rutting and demonstrates higher indirect tensile strength and TSR value.

Surface treatment effects on morphological and property enhancements of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/Diss fibers (Ampelodesmos mauritanicus) biocomposites

AbstractThe present research investigates the influence of chemical modifications on the surface of Diss fibers (Ampelodesmos mauritanicus) as an effective reinforcing agent for biocomposites based on poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV). The Diss fiber surface underwent three different chemical treatments: alkaline, alkaline/peroxide, and alkaline/silane. Changes in morphology, mechanical properties, thermomechanical behavior, and contact angle measurements of the biocomposite materials were studied according to the following weight ratio PHBV/Diss fibers 80/20. Scanning electron microscopy (SEM) analysis of the fractured surface of the biocomposite samples revealed improved adhesion between Diss fibers and the PHBV matrix after surface modification, compared with the unmodified sample. The study demonstrated that the incorporation of Diss fibers leads to an enhancement in the mechanical performances of PHBV‐based biocomposites. The tensile properties of the modified biocomposites showed a significant increase in Young's modulus compared with the biocomposites with untreated fiber. Similar trends were observed in the data obtained from dynamic mechanical analysis (DMA) and contact angle measurement. Overall, the study highlights the beneficial effects of Diss fibers modification, particularly with the alkali–silane combination, in enhancing the properties of PHBV biocomposites, there by broadening their potential application fields.Highlights The study explores the potential of Diss fibers as an effective reinforcement for PHBV‐based biocomposites. Fully biodegradable biocomposites based on PHBV/Diss fibers are melt‐compounded. Diss fibers are chemically modified by alkaline, alkaline/peroxide, and alkaline/silane. The chemical treatment has considerably enhanced the properties and morphology of the biocomposites, being however much higher for alkaline/silane treatment. The method can be used for specific applications and large‐scale production.

Enhancing Fire Resistance of Geopolymers Modified with Thermal Insulation Additives

This study aims to improve the fire resistance of geopolymers by adding thermal insulation materials. These additives help the material perform better at high temperatures. Previous research focused on using fly ash, metakaolin, and zeolite in geopolymer composites. This study looks at how porous additives affect compressive strength and whether non-destructive testing can measure damage after heat exposure. Four temperature tests were set: 400 °C for 60 min, 400 °C for 120 min, 800 °C for 60 min, and a maximum of 658 °C for 120 min. The results showed that the compressive strength and ultrasonic pulse velocity (UPV) dropped as the temperature increased, with a sharp decrease at 800 °C. Unmodified samples broke apart at high temperatures, while modified samples lost 40% to 70% of their strength. The study confirmed that a dense, amorphous matrix improves heat resistance, even with porous additives like fly ash. A link between UPV and compressive strength was found, suggesting non-destructive testing could be useful for checking structural integrity after a fire.

Aerated Concrete, Based on the Ash of Thermal Power Plants, Nanostructured with Water-Soluble Fullerenols

This study is devoted to the synthesis of aerated concrete by a non-autoclave method using ash from thermal power plants and a nanopreparation. Fullerenol-m was used as a nanopreparation. The fullerenol-m content in the sealing water of aerated concrete changed in the range of 0.00 ÷ 0.03 mas.%. The main performance characteristics of the nanostructured aerated concrete were studied, namely the compressive strength, impact toughness, thermal conductivity, density and moisture content. A significant improvement in the performance characteristics of the nanomodified aerated concrete compared to unmodified samples was demonstrated, which was most clearly manifested as an increase in impact toughness by several (three to five) times. The best performance characteristics of the modified aerated concrete were observed at a fullerenol-m concentration relative to the added cement within 0.022–0.028 wt.%. The authors attribute such a strong change and improvement in the physical, chemical and operational properties of aerated concrete when modified with fullerenol-m to the fact that fullerenol-m (a few thousandths of wt.%) has a very strong structuring effect on the sealing water and, as a consequence, on the resulting aerated concrete.

Optimizing the radiation synthesis and swelling of agar-based acrylate superabsorbent hydrogel for irrigation water conservation

This study reports the synthesis of novel agar/poly methacrylic acid/poly acrylic acid (AG/PMAc/PAc) superabsorbent hydrogels via gamma radiation and their subsequent urea modification to enhance swelling and water retention for agricultural applications. The superabsorbent hydrogels were prepared by irradiating aqueous mixtures of varying agar concentrations with methacrylic acid/acrylic acid (MAc/Ac) monomers, followed by urea treatment at different cycles and concentrations. The morphological characteristics and chemical structures were confirmed by SEM and FTIR, respectively. The maximum swelling occurred at 6 % agar and 1 % urea modification. Remarkably, the 1 % urea-modified hydrogel displayed a 41.1 % swelling increase and 236.4 % enhancement after the second modification cycle compared to unmodified samples. Water retention studies showed the modified hydrogel retained 53.2 % moisture after 14 days versus the complete drying of unmodified hydrogels. Soil application studies demonstrated the modified hydrogel increased moisture content by 177.3 % after 20 days, promoting better growth with 30 % more leaves and 38.9 % higher stem length in Vicia faba plants versus controls. This novel radiation-synthesized, urea-modified hydrogel with exceptional swelling and moisture retention capabilities shows promising potential for sustainable agricultural irrigation and crop productivity enhancement under water-deficit conditions.

Antimicrobial activities of modified and unmodified pectin obtained from peels of Irvingia gabonensis, Cola milleni, and Theobroma cacao on specific pathogenic organisms

The antibacterial and antifungal activities of ethanolic extracts of pectin derived from the peels of Theobroma cacao, Cola milleni, and Irvingia gabonensis were investigated against phytopathogenic bacteria and fungi. The agar diffusion method was employed to test the extracts against Staphylococus aureus, Pseudomonas aeroginosa, Chromobacterium violaceum, Streptococcus feacalis, Xanthomonas axonopodis, Erwinia carotovora, Sclerotium rulfsii, Pythophthora palmivora, and Pyricularia oryzae. Significant differences (p<0.05) were observed in all control groups. The extracts inoculated with Streptomycin exhibited the highest activity against all bacterial strains. Conversely, the unmodified extracts of pectin samples from cola, cocoa, and wild mango displayed the least inhibitory activity against the tested bacterial strains, while the modified extracts with Chloro Acetic Acid (CAA), Para Amino Benzoic Acid (PABA), and Para Nitro Benzoic Acid (PNBA) showed varying inhibitory effects. The control sample inoculated with Mancozeb demonstrated the highest zone of inhibition against all fungal strains in the three pectin samples. However, the modified pectin samples exhibited increased inhibitory effects compared to the unmodified pectin extract, although the results were closer to the control. The higher values of modified pectin can be attributed to the presence of modifying agents such as long-chain hydrocarbons, acetic acid, chloro compounds, carboxyl, benzene rings, amino groups, and nitro groups. The presence of secondary metabolites in the pectin samples may also contribute to the higher values observed in both modified and unmodified samples. Overall, the results indicate the fungicidal and bactericidal potential of the extracts against the tested organisms, suggesting their potential use as broad-spectrum antimicrobial agents.

Composite photocatalysts g-C<SUB>3</SUB>N<SUB>4</SUB>/TiO<SUB>2</SUB> for hydrogen production and dye decomposition

The photocatalytic activity of the g-C3N4 /TiO2 composite samples in the processes of dye (methylene blue) decomposition and hydrogen evolution from an aqueous ethanol solution under the action of visible radiation (400 nm) has been studied. A new original method for the synthesis of the g-C3N4 /TiO2 composite by depositing g-C3N4 /TiO2 to TiO2 nanoparticles during sol-gel synthesis is proposed. The synthesized photocatalysts were characterized by X-ray diffraction, low-temperature gas adsorption, X-ray photoelectron spectroscopy, high-resolution transmission microscopy, and diffuse reflectance spectroscopy in the UV and visible regions. The maximum activity in the hydrogen evolution reaction was 1.3 mmol h–1, which exceeds the rate of hydrogen evolution on the unmodified g-C3N4 and TiO2 samples.

Effect of Electron Irradiation on the Optical Properties of Zinc Oxide Powder Modified by Magnesium Oxide Nanoparticles

The effect of modifying ZnO powders with MgO nanoparticles (with a concentration of 0.1–10 wt. %) on their diffuse reflectance spectra in the region of 0.2–2.5 μm before and after irradiation with 30 keV electrons was studied. Modification of ZnO powder was carried out by MgO nanopowder with concentrations from 0.1 to 10 wt. % using a solid-state method at 650°C heating temperature. X-ray diffraction analysis showed that this method of modification there is no formation of additional phases. It has been established that zinc oxide structure symmetry belongs to the P63mc space group, magnesium oxide – to the Fm–3m space group. The spectral reflectance of such powders in the visible region is over 90%. Under irradiating by 30 keV electrons of initial and modified ZnO powders, as well as MgO nanopowder, a decrease in their reflectance recorded in the entire studied region of the spectrum. It has been established that modification with MgO nanoparticles at a concentration of 3 wt. % leads to an increase in radiation resistance by a factor of 1.32 compared to unmodified samples. This effect is determined by the sink of radiation defects on the large specific surface area of nanoparticles.

Enhancing moisture-resistance in polyimide aerogels: A novel hydrophobic modification approach with ortho-positioned long-chain barriers

Polyimide (PI) aerogels possess significant potential for various applications due to their outstanding mechanics and thermal insulation. However, a major drawback of these aerogels is their susceptibility to moisture, which not only compromises their insulative performance but also leads to an increase in weight. To address this issue, we have developed a moisture-resistance technique by incorporating a long-chain hydrophobic barrier at the ortho position relative to the imide groups to enhance the moisture-resistance of the PI aerogels. This approach involved using a series of diamines with hydroxyl groups strategically located at the ortho position of imide groups as reactants. The resulting PI aerogels demonstrated a significant improvement in water resistance, reducing water-uptake to merely one-tenth of that recorded in unmodified samples. Furthermore, the effectiveness of this hydrophobic modification was validated through molecular dynamics simulations, which indicated a diffusion coefficient of 4.41 × 10−11 m2/s after modification. These findings represent a considerable advancement in developing effective methods for hydrophobic modification of PI aerogels, with potential applications in aerospace, electronic communications, and environmental protection.

The effect of the modification mechanism of SiO2 in resin‐based friction materials on the mechanical and tribological performance

AbstractThis study aimed to address the thermal degradation of resin‐based friction materials in the mid‐temperature stage (200–250°C), as well as the resulting instability of the friction coefficient and decrease in the mechanical properties. To investigate the impact on the toughening and wear resistance properties, this study employed nanosilica‐modified resin‐based friction materials. The mechanical, friction, and wear properties of the modified samples were tested using a Rockwell hardness tester, hydraulic universal testing machine, and constant speed friction tester. The phase composition and microstructure of the samples were analyzed by scanning electron microscope, energy‐dispersive x‐ray spectroscopy, x‐ray diffraction. When the mass fraction of nanosilica was 3%, modified sample S3 exhibited excellent mechanical properties, with shear strength and compressive strength reaching 40.3 and 171.7 MPa, respectively, which were increased by 30% and 9% compared to unmodified sample S1. Moreover, the density and hardness of sample S3 showed minimal variation compared to those of unmodified sample S1. In the temperature range of 100–250°C, the wear rate of modified sample S3 remained within the range of 0.22 × 10−7–0.38 × 10−7 N−1 m−1, with a friction coefficient of 0.38 at 200°C, demonstrating excellent wear resistance.