Search Results (2,396)

Background/Objectives: In-office bleaching commonly employs high concentrations of hydrogen peroxide (HP) or carbamide peroxide (CP), which may compromise enamel integrity. This in vitro paired-design study aimed to compare the chemical and mechanical effects of three commercial bleaching agents—Opalescence Boost (40% HP), Opalescence Quick (45% CP), and BlancOne Ultra+ (35% HP)—on human enamel. The null hypothesis assumed no significant differences between the control and treated samples. Given the ongoing debate over pH, active ingredients, and enamel impact, comparing whitening systems remains clinically important. Methods: Forty-two extracted teeth were assigned to three experimental groups (n = 14) with matched controls. Each underwent a single bleaching session per manufacturer protocol: Opalescence Boost (≤60 min), Opalescence Quick (15–30 min), and BlancOne Ultra+ (three light-activated cycles of 8–10 min). Enamel chemical changes were analyzed by Fourier transform infrared (FTIR) spectroscopy (phosphate and carbonate bands), and surface hardness by Vickers microhardness testing. Paired t-tests (α = 0.05) assessed statistical significance. Results: FTIR analysis revealed alterations in phosphate and carbonate bands for all agents, most notably for Opalescence Boost and BlancOne Ultra+. Microhardness testing showed significant reductions in enamel hardness for Opalescence Boost (control: 37.21 ± 1.74 Hv; treated: 34.63 ± 1.70 Hv; p = 0.00) and Opalescence Quick (control: 45.82 ± 1.71 Hv; treated: 39.34 ± 1.94 Hv; p < 0.0001), whereas BlancOne Ultra+ showed no significant difference (control: 51.64 ± 1.59 HV; treated: 51.60 ± 2.34 Hv; p = 0.95). Conclusions: HP-based agents, particularly at higher concentrations, caused greater enamel alterations than CP-based products. While clinically relevant, the results should be interpreted cautiously due to in vitro limitations and natural enamel variability. Full article

Although cemented carbides have been manufactured by the powder metallurgy (P/M) technology for over a century now, systematic developmental efforts are still underway. In the present study, tool life improvements in metal grooving applications are the key objective. Four PVD-coated cemented carbides compositions, dedicated to groove steel, stainless steel, cast iron, and aluminium alloys, have been newly designed, along with their manufacturing conditions. Physical, mechanical and chemical characteristics—such as sintered density, modulus of elasticity, hardness, fracture toughness, WC grain size, and the chemical composition of the substrate material, as well as the chemical composition, microhardness, structure, and thickness of the coatings—have been studied. A series of grooving tests have also been conducted to assess whether modifications to the thus far marketed tool materials, tool geometries, and coatings can improve cutting performance. In order to compare the laboratory and application properties of the investigated materials with currently produced by reputable companies, commercial inserts have also been tested. The experimental results obtained indicate that the newly developed grooving inserts exhibit excellent microstructural characteristics, high hardness, fracture toughness, and wear resistance and that they show slightly longer tool life compared to the commercial ones. Full article

This study investigated the individual and combined effects of α-amylase (6 and 10 ppm), xylanase (70 and 120 ppm), and cellulase (35 and 60 ppm) on the physicochemical and nutritional properties of Chinese steamed buns (CSBs) supplemented with 15% buckwheat flour. The addition of individual enzymes did not significantly affect the volume or texture of the buckwheat-enriched CSBs, although it increased the crumb moisture content and porosity. In contrast, enzyme combinations can improve specific volume and reduce hardness. The enzyme combination (α-amylase 6 ppm, xylanase 70 ppm, and cellulase 60 ppm) yielded the highest specific volume (2.50 mL/g) and the lowest hardness (271.46 g). Regarding chemical properties, individual enzymes had minimal impact, while the combined treatment (6, 70, 60 ppm) decreased starch and dietary fiber content. For nutritional properties, the glycemic response of the CSBs varied depending on the concentration of the enzyme combination used. Full article

Diamond, renowned for its exceptional electrical, physical, and chemical properties, including ultra-wide bandgap, superior hardness, high thermal conductivity, and unparalleled stability, serves as an ideal candidate for next-generation high-power and high-temperature electronic devices. Among diamond-based devices, Schottky barrier diodes (SBDs) have garnered significant attention due to their simple architecture and superior rectifying characteristics. This review systematically summarizes recent advances in diamond SBDs, focusing on both metal–semiconductor (MS) and metal–interlayer–semiconductor (MIS) configurations. For MS structures, we critically analyze the roles of single-layer metals (including noble metals, transition metals, and other metals) and multilayer metals in modulating Schottky barrier height (SBH) and enhancing thermal stability. However, the presence of interface-related issues such as high densities of surface states and Fermi level pinning often leads to poor control of the SBH, limiting device performance and reliability. To address these challenges and achieve high-quality metal/diamond interfaces, researchers have proposed various interface engineering strategies. In particular, the introduction of interfacial layers in MIS structures has emerged as a promising approach. For MIS architectures, functional interlayers—including high-k materials (Al₂O₃, HfO₂, SnO₂) and low-work-function materials (LaB₆, CeB₆)—are evaluated for their efficacy in interface passivation, barrier modulation, and electric field control. Terminal engineering strategies, such as field-plate designs and surface termination treatments, are also highlighted for their role in improving breakdown voltage. Furthermore, we emphasize the limitations in current parameter extraction from current–voltage (I–V) properties and call for a unified new method to accurately determine SBH. This comprehensive analysis provides critical insights into interface engineering strategies and evaluation protocols for high-performance diamond SBDs, paving the way for their reliable deployment in extreme conditions. Full article

Catalytic upgrading of pyrolysis oils is an important step for producing replacement hydrocarbon-rich liquid biofuels from biomass and can help to advance pyrolysis technology. Catalysts play a pivotal role in influencing the selectivity of chemical reactions leading to the formation of main compounds in the final upgraded liquid products. The present work involved a systematic study of solvent-free catalytic reactions of cyclohexanone in the presence of hydrogen gas at 160 °C for 3 h in a batch reactor. Cyclohexanone can be produced from biomass through the selective hydrogenation of lignin-derived phenolics. Three types of catalysts comprising undoped NbOPO₄, 10 wt% NiO/NbOPO₄, and 30 wt% NiO/NbOPO₄ were studied. Undoped NbOPO₄ promoted both aldol condensation and the dehydration of cyclohexanol, producing fused ring aromatic hydrocarbons and hard char. With 30 wt% NiO/NbOPO₄, extensive competitive hydrogenation of cyclohexanone to cyclohexanol was observed, along with the formation of C₆ cyclic hydrocarbons. When compared to NbOPO₄ and 30 wt% NiO/NbOPO₄, the use of 10 wt% NiO/NbOPO₄ produced superior selectivity towards bi-cycloalkanones (i.e., C₁₂) at cyclohexanone conversion of 66.8 ± 1.82%. Overall, the 10 wt% NiO/NbOPO₄ catalyst exhibited the best performance towards the production of precursor compounds that can be further hydrodeoxygenated into energy-dense aviation fuel hydrocarbons. Hence, the presence and loading of NiO was able to tune the activity and selectivity of NbOPO₄, thereby influencing the final products obtained from the same cyclohexanone feedstock. This study underscores the potential of lignin-derived pyrolysis oils as important renewable feedstocks for producing replacement hydrocarbon solvents or feedstocks and high-density sustainable liquid hydrocarbon fuels via sequential and selective catalytic upgrading. Full article

In this paper, SiC and Si/SiC ceramics were fabricated using direct laser powder bed fusion with chemical vapor infiltration. Their microstructure, mechanical properties and the impacts of silicon addition were analyzed. The incorporation of silicon led to an increase in the relative density of the silicon carbide ceramics from 76.4% to 78.3% and the compression strength increased from 39 ± 13 MPa to 90 ± 8 MPa after laser powder bed fusion with chemical vapor infiltration. The melting and re-solidification of silicon allows the silicon to encapsulate the silicon carbide grains, changing the microstructure and the failure mechanism of the silicon carbide ceramics, resulting in a small amount of silicon residue. In the LPBF-CVI SiC ceramic specimen, the LPBF-formed SiC exhibits a microhardness of 24.2 ± 1.0 GPa. In LPBF-CVI Si/SiC, the spherical dual-phase structure displays a moderately increased hardness (25.9 ± 4.4 GPa), and the CVI-formed SiC exhibits a hardness of 55.3 ± 9.3 GPa. Full article

Electroless nickel deposition (ELD) is an autocatalytic technique extensively used to impart conductive, protective, and mechanical functionalities to inherently non-conductive synthetic substrates. This review systematically explores the fundamental mechanisms of electroless nickel deposition, emphasising recent advancements in surface activation methods, solvent systems, and microstructural control. Critical analysis reveals that bio-inspired activation methods, such as polydopamine (PDA) and tannic acid (TA), significantly enhance coating adhesion and durability compared to traditional chemical etching and plasma treatments. Additionally, solvent engineering, particularly using polar aprotic solvents like dimethyl sulfoxide (DMSO) and ethanol-based systems, emerges as a key strategy for achieving uniform, dense, and flexible coatings, overcoming limitations associated with traditional aqueous baths. The review also highlights that microstructural tailoring, specifically the development of amorphous-nanocrystalline hybrid nickel coatings, effectively balances mechanical robustness (hardness exceeding 800 HV), flexibility, and corrosion resistance, making these coatings particularly suitable for wearable electronic textiles and smart materials. Furthermore, commercial examples demonstrate the real-world applicability and market readiness of nickel-coated synthetic fibres. Despite significant progress, persistent challenges remain, including reliable long-term adhesion, internal stress management, and environmental sustainability. Future research should prioritise environmentally benign plating baths, standardised surface activation protocols, and scalable deposition processes to fully realise the industrial potential of electroless nickel coatings. Full article

In recent years, significant attention has been directed toward the development of coating materials capable of tailoring surface properties for various functional applications. Transition metal nitrides, in particular, have garnered interest due to their superior physical and chemical properties, including high hardness, excellent wear resistance, and strong corrosion resistance. In this study, a fabrication process for CrN-based thin films was developed by combining reactive direct current magnetron sputtering (dcMS) with post-deposition annealing in air. CrN coatings were deposited by reactive dcMS using different argon-nitrogen (Ar:N₂) gas ratios (4:1, 3:1, 2:1, and 1:1), followed by annealing at 550 °C for 1.5 h in ambient air. XRD and EDS analysis revealed that this treatment results in the formation of a composite phase comprising CrN and Cr₂O₃. The resulting coating exhibited favorable mechanical and tribological properties, including a maximum hardness of 12 GPa, a low wear coefficient of 0.254 and a specific wear rate of 7.05 × 10⁻⁶ mm³/N·m, making it a strong candidate for advanced protective coating applications. Full article

Knowing the superior biochemical defense mechanisms of sessile organisms, it is not hard to believe the cure for any human sickness might be hidden in nature—we “just” have to identify it and make it safely available in the right dose to our organs and cells that are in need. For decades, green tea catechins (GTCs) have been a case in point. Because of their low redox potential and favorable positioning of hydroxyl groups, these flavonoid representatives (namely, catechin—C, epicatechin—EC, epicatechin gallate—ECG, epigallocatechin—EGC, epigallocatechin gallate—EGCG) are among the most potent plant-derived (and not only) antioxidants. The proven anti-inflammatory, neuroprotective, antimicrobial, and anticarcinogenic properties of these phytochemicals further contribute to their favorable pharmacological profile. Doubtlessly, GTCs hold the potential to “cope” with the majority of today‘s socially significant diseases, yet their mass use in clinical practice is still limited. Several factors related to the compounds’ membrane penetrability, chemical stability, and solubility overall determine their low bioavailability. Moreover, the antioxidant-to-pro-oxidant transitioning behavior of GTCs is highly conditional and, to a certain degree, unpredictable. The nanoparticulate delivery systems represent a logical approach to overcoming one or more of these therapeutic challenges. This review particularly focuses on the lipid-based nanotechnologies known to be a leading choice when it comes to drug permeation enhancement and not drug release modification nor drug stabilization solely. It is our goal to present the privileges of encapsulating green tea catechins in either vesicular or particulate lipid carriers with respect to the increasingly popular trends of advanced phytotherapy and functional nutrition. Full article

This study investigates the friction stir joining of AA6082-T6 aluminum alloy and Noryl GFN2 polymer in a buttstrap configuration, targeting the development of lightweight cylindrical-shaped structures where the polymer provides thermal, chemical, and electrical insulation, while the aluminum ensures mechanical integrity. A parametric analysis was carried out to assess the ability to produce friction stir buttstrap composite panels in a single processing step and assess the resulting tensile and flexural behavior. To that end, travel and rotating speeds ranging from 2150 to 2250 rpm, and 100 to 140 mm/min, respectively, were employed while keeping plunge depth and the tilt angle constant. A total of nine composite joints were successfully produced and subsequently subjected to both tensile and four-point bending tests. The tensile and flexural strength results ranged from 80 to 139 MPa, and 39 to 47 MPa, respectively. Moreover, the microstructural examination revealed that all joints exhibited a defect within the joining region and its size and shape had a significant effect on tensile strength, whereas the flexural strength was less affected with more uniform results. The joining region was also characterized by a decrease in hardness, particularly in the pin-affected region on the aluminum end of the joint, exhibiting a W-shaped pattern. Contrarily, on the polymeric end of the joining region, no significant change in hardness was observed. Full article

Background: Dental enamel demineralization is a critical early event in the development of dental caries. To address this, bioactive compounds have been explored for their potential to mitigate enamel demineralization and promote remineralization. Previous studies have demonstrated that varnishes containing natural compounds such as trans,trans-farnesol (tt-farnesol), quercetin, and theobromine exhibit antimicrobial activity, suggesting potential in caries prevention. Thus, this laboratory study assessed the ability of these varnishes to prevent enamel caries lesion formation by using a chemical model to determine whether these natural compounds interfered with de- and remineralization processes in the absence of a cariogenic biofilm. Methods: Sixty bovine enamel specimens, each measuring 5 × 5 × 2 mm, were selected according to their initial surface hardness (SHI), measured by Knoop hardness in three indentations spaced 100 µm apart. The specimens were allocated to the following groups in a random manner (n = 15): an experimental varnish without compounds (NC/negative control); experimental varnishes containing the combination of tt-farnesol, quercetin, and theobromine at concentrations of 1.5% (E1) and 4.5% (E2); and Duraphat™ (NaF 5%/gold standard—D). After applying the varnishes, they remained in artificial saliva for 6 h. The specimens were then subjected to 8 pH cycles, including 4 h of demineralization and 20 h of remineralization. Surface hardness was measured again to calculate the percentage of surface hardness loss (%SHL), and three specimens from each group were examined using scanning electron microscopy. Comparisons were made using ANOVA (p < 0.05). Results: The D group (5% NaF) demonstrated a significantly lower %SHL (75.5% ± 7.88) than the other groups (p < 0.05). E1 (86.3% ± 5.33) was statistically similar to NC (81.8% ± 4) but lower than E2. E2 showed the highest %SHL (91.6% ± 3.64) compared to the other groups. Surface demineralization was evident in all specimens post pH cycling. Conclusion: The bioactive varnishes containing tt-farnesol, quercetin, and theobromine at concentrations of 1.5% and 4.5% did not exhibit a protective effect against mineral loss in dental enamel in the absence of a cariogenic biofilm. Full article

The stabilization of heavy metal elements, such as zinc, in the form of ions within the glass-ceramics represents a valuable approach to addressing environmental pollution caused by heavy metals. This study investigates the feasibility and physicochemical properties of diopside-based glass-ceramics synthesized from zinc-containing smelting slag. The zinc-rich smelting slag is abundant in SiO₂, Al₂O₃, CaO, and other constituents, thereby providing cost-effective and efficient raw materials for glass-ceramic production. The conversion of zinc-containing smelting slag into glass-ceramics was achieved through a melting process. We analyzed the effects of varying doping levels on the properties of the resulting glass-ceramics. The results indicated that as the doping level of smelting slag increases, the crystallization temperature of the glass-ceramics decreases while the crystal phases of diopside and anorthite progressively increase, significantly enhancing both mechanical strength and chemical stability. Notably, when the doping level reaches 60%, these glass-ceramics exhibit remarkable physical properties, including high density (3.12 g/cm³), Vickers hardness (16.60 GPa), and excellent flexural strength (150.75 MPa). Furthermore, with increasing amounts of doped smelting slag, there are substantial improvements in acid resistance, alkali resistance, and corrosion resistance in these materials. Raman spectroscopy and EDS analysis further verified a uniform distribution of the crystal phase and effective immobilization of heavy metal zinc. Full article

In this study, the impact of incorporating energetic substituents such as -NO₂, -NH₂, -NH₃, -N₂ (both with perchlorate anion), and -N₃ into 4,6-dinitrobenzimidazol-2-one on its detonation performance and stability was investigated. The DFT B3LYP/cc-pVTZ method was employed to evaluate key molecular properties: the HOMO–LUMO gap, cohesive energy, chemical hardness, and electronegativity. Based on these parameters, the resulting changes in chemical and thermal stability were assessed. The results achieved highlight the significant role of ionic bonding in enhancing both the stability and density of the compounds. Our results indicate that the benzimidazoles enriched by energetic groups possess energetic properties better than TNT, with some variants surpassing HMX. The analysis of the stability and sensitivity based on oxygen balance investigation suggests that by varying the incorporated substituents, it is possible to design both primary and secondary explosives from a common molecular scaffold. Full article

The escalating global demand for fresh water, driven by urbanization and industrial growth, underscores the need for sustainable water management, particularly in the water-intensive construction sector. Although prior studies have primarily concentrated on treated wastewater, the practical viability of utilizing untreated wastewater has not been thoroughly investigated—especially in developing nations where treatment expenses frequently impede actual implementation, even for non-structural uses. While prior research has focused on treated wastewater, the potential of untreated or partially treated wastewater from diverse industrial sources remains underexplored. This study investigates the feasibility of incorporating wastewater from textile, sugar mill, service station, sewage, and fertilizer industries into concrete paver block production. The novelty lies in a dual approach, combining experimental analysis with XGBoost-based machine learning (ML) models to predict the impact of key physicochemical parameters—such as Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Hardness—on mechanical properties like compressive strength (CS), water absorption (WA), ultrasonic pulse velocity (UPV), and dynamic modulus of elasticity (DME). The ML models showed high predictive accuracy for CS (R² = 0.92) and UPV (R² = 0.97 direct, 0.99 indirect), aligning closely with experimental data. Notably, concrete pavers produced with textile (CP-TXW) and sugar mill wastewater (CP-SUW) attained 28-day compressive strengths of 47.95 MPa and exceeding 48 MPa, respectively, conforming to ASTM C936 standards and demonstrating the potential to substitute fresh water for non-structural applications. These findings demonstrate the viability of using untreated wastewater in concrete production with minimal treatment, offering a cost-effective, sustainable solution that reduces fresh water dependency while supporting environmentally responsible construction practices aligned with SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production). Additionally, the model serves as a practical screening tool for identifying and prioritizing viable wastewater sources in concrete production, complementing mandatory laboratory testing in industrial applications. Full article

Ultra-fine-grained bainitic (UFGB) steels offer excellent mechanical properties, which can be further improved by applying diamond-like carbon (DLC) coatings. However, poor adhesion between the coating and substrate remains a key limitation. Since the steel’s microstructure degrades at high temperatures, enhancing adhesion without heating the substrate is essential. This study investigates surface hardening combined with simultaneous nitrogen and hydrogen doping during the Radio Frequency Chemical Vapor Deposition (RFCVD) process to improve coating performance. Varying gas compositions were tested to assess their effects on coating properties. Nitrogen incorporation decreased hardness from 12 GPa to 9 GPa but improved adhesion, while hydrogen limited damage after coating failure. Optimizing the gas mixture led to enhanced adhesion and wear resistance. Raman and X-ray photoelectron spectroscopy (XPS) analyses confirmed that the optimized coatings had the highest sp³ bond content and elevated nitrogen levels. While both hardness and adhesion contributed to wear resistance, no direct link to coating thickness was found. Overall, co-doping with nitrogen and hydrogen is an effective approach to improve adhesion and wear resistance without requiring high processing temperatures or complex equipment. Full article