Search Results (329)

This study includes an interpretable machine learning (ML) framework for predicting the shear contribution of externally bonded fiber-reinforced polymer (FRP) composites in reinforced concrete beams. A database including total 313 experimental specimens was collected from previous experimental research. The data screening process has been conducted using the Isolation Forest algorithm, resulting in 268 cleaned specimens. The cleaned database was divided into a training subset containing 214 specimens and an independent test set containing 54 specimens. The trained subset was enlarged into 5204 synthetic data using two advanced generative models including Wasserstein generative adversarial network and conditional Variational autoencoder (CVAE). Separate constrained monotonic neural network (CMNN) models were then trained on both datasets and WGAN-based CMNN achieved $R^2=0.9524$ for the synthetic training dataset and $R^2=0.9120$ for the independent test set, whereas the CVAE-based CMNN achieved corresponding values of 0.9632 and 0.9011. To improve practical applicability, response functions were extracted from WGAN-based CMNN and fitted with analytical expressions to derive a closed-form prediction equation. The proposed equation was independently validated using separate unseen test specimens, which were not used in CMNN training and achieved R² $=$ 0.79, RMSE $=$ 24.98 kN, MAE $=$ 19.65 kN, MAPE $=$ 21.72%, VAF $=$ 79.35%, U95 $=$ ±54.94 kN, SI $=$ 3.04, and PI $=$ 0.11. Compared with ACI 440.2R-17, CSA-S806.12, CNR-DT200 R1.2013, TR-55, and JSCE, the proposed equation showed superior accuracy while maintaining a transparent and design-oriented format. Full article

Lightweight materials with improved strength characteristics are increasingly required in aerospace, automotive, impact protection, and vibration damping applications to enhance structural efficiency and service life. Although aluminum metal foams have been found to be promising lightweight cellular materials, their load-bearing performance is rather limited, thus limiting their use for high-performance structural applications. The composite metal foams in the present study were produced by CaCO₃ as foaming agent and AA7075 as the base material by gas-releasing particle decomposition method, in which the foaming agent is transformed into CO₂ gas to generate pores during foaming. Cell size distribution analysis, density, and energy-dispersive spectroscopy were used to investigate the composite foams containing 0, 1, 2 and 3 wt.% Si₃N₄, while quasi-static uniaxial compression testing was employed to measure the compressive strength of these foams. Si₃N₄ of 2 wt.% and 3 wt.% resulted in better pore refinement and uniformity of cells, as revealed in the microstructural analysis. The density was raised from 0.21 to 0.61 g/cm³ by reinforcement addition. The compression strength increased from 7.85 to 23.64 MPa, while energy absorption increased from 5.10 to 20.52 MJ/m³ for foams containing 0 and 3 wt.% Si₃N₄, respectively. The yield strength also improved from 4.92 to 15.98 MPa, and the plateau stress from 7.37 to 22.57 MPa. Improved mechanical behavior is due to the following: refinement of pores, thickness of the ligaments, more compact structure, and load transfer in the cellular structure. Full article

The activity and stability of Ni-based catalysts for CO₂ methanation strongly depend on the morphology and chemical composition of the support. In this work, Ni catalysts with four oxidic supports (SiO₂, Al₂O₃, CeO₂, ZrO₂) were synthesized via a one-step spray pyrolysis approach. Comprehensive characterization by STEM-EDS, XRD, and N₂ adsorption was used to resolve support morphology, Ni particle size, and nanoparticle incorporation into the support matrix. Beyond steady-state activity and reaction mechanism, the support material also affects the activation period and initial stability of the catalysts. By combining temperature-programmed methanation scans on fresh and spent samples with long-term stability tests, we clearly identify support-dependent changes in initial activity and their correlation with Ni–support interactions. Enhanced physical embedding and stronger chemical binding of Ni nanoparticles significantly reduce activity changes during the first hours on stream. Overall, this study demonstrates that the support and the corresponding metal–support interactions not only affect reaction pathways and activity, but also the pretreatment and activation required to reach a stable operating point, which is of crucial importance in kinetic catalysis research. Full article

This study investigates the effect of SiC nanoparticle addition on the microstructure, interfacial reactions, and mechanical properties of Zn5Al3Ti active solder used for ultrasonic soldering of AlN ceramic to copper substrates. Composite solders containing 3 and 6 wt.% SiC nanoparticles were prepared and applied under flux-free ultrasonic soldering conditions. The solder alloys were evaluated by tensile testing, while the soldered joints were evaluated by shear strength testing. The solder microstructure and interfacial regions were characterized using SEM/EDS analysis. The results showed that the addition of SiC nanoparticles modified the microstructure of the Zn5Al3Ti solder and influenced the mechanical performance of the ceramic/metal joints. Among the investigated systems, the AlN/Zn5Al3Ti + 6 wt.% SiC/Cu joint exhibited the highest shear strength, reaching approximately 101 MPa. SEM/EDS observations revealed the formation of compact multilayered interfacial regions, including possible Cu–Zn intermetallic phases at the Cu/solder interface and Al–Ti–Zn-based reaction products near the solder/AlN interface. The improved joint performance may be attributed to the combined effect of SiC-induced microstructural modification, the presence of Si-containing particles, and the formation of compact metallurgical bonds. The results indicate that Zn5Al3Ti solder modified with 6 wt.% SiC nanoparticles is a promising material for producing strong AlN/Cu joints under the applied ultrasonic soldering conditions. Full article

This study investigated the impact of cobalt/nickel-silicate loadings on graphitic carbon nitride at 10% and 20% doses, designated (CoNiSi-10) and (CoNiSi-20), for the removal of ciprofloxacin (CPF), a hazardous, bioaccumulative antibiotic. The synthesized composites were characterized in detail using SEM, EDX, TEM, N₂ adsorption–desorption, XRD, and FTIR techniques. The CoNiSi-10 and CoNiSi-20 exhibited CPF q_t values of 64 and 107 mg g⁻¹, respectively, which were consistent with the surface area results. Adsorption kinetics indicated that CPF uptake on CoNiSi-10 and CoNiSi-20 fitted the Lagergren model, with the liquid-film and intraparticle-diffusion mechanisms co-governing CPF sorption. The isotherm investigations indicated CPF adsorption on CoNiSi-10 and CoNiSi-20 aligned with the Langmuir model, suggesting a homogeneous surface, while the Dubinin-Radushkevich results primarily indicated physisorption-based CPF removal. The thermodynamic analyses supported the physisorption outcome and indicated that CPF sorption onto CoNiSi-10 and CoNiSi-20 was endothermic. A five-cycle reusability test yielded average efficiencies of 94% and 96% for CoNiSi-10 and CoNiSi-20, respectively, and an after-sorption analysis indicated their stability and robustness. The ease of synthesis and excellent sorption performance may nominate CoNiSi-10 and CoNiSi-20 as promising adsorbents for treating pharmaceutically contaminated wastewater. Full article

Graphite is widely used as an anode in lithium-ion batteries (LIBs); however, its limited capacity restricts the energy density enhancement. Si-based anodes offer much higher capacity, but their significant volume changes during repeated lithiation and delithiation generate mechanical stress and can damage the electrode/current-collector interface. Herein, high-strength nanotwinned Cu (NT-Cu) was fabricated and employed as current collectors for carbon-coated Si/β-Si₃N₄-based anodes. The electroplated 5 μm-thick NT-Cu foils exhibited tensile strength exceeding 760 MPa. The role of the Cu current collector was investigated by comparing NT-Cu foils with different mechanical properties and commercial Cu foils. The results show that electrochemical performance was not governed by UTS alone; instead, a balanced combination of tensile strength, ductility, and surface morphology was important for improving cycling stability and rate capability. To further improve cycling retention, artificial graphite was incorporated into the Si/β-Si₃N₄ composite. Using a 5 μm electroplated NT-Cu foil and a Si/β-Si₃N₄/artificial graphite composite anode, the pouch cell retained 81.51% of its capacity and delivered 267.3 mAh g⁻¹ after 206 cycles. These results demonstrate the potential of NT-Cu for improving the stability of Si-containing LIB anodes. Full article

Enhancing the mechanical performance of aluminium-based materials remains a critical challenge for their application in demanding environments. In this context, aluminium-based hybrid nanocomposites reinforced with multi-walled carbon nanotubes (MWCNTs) and nano-sized silicon carbide (nSiC) have been developed to overcome inherent limitations of pure aluminium, such as relatively low hardness, limited compressive strength and poor wear resistance. The composites were fabricated via powder metallurgy by incorporating a fixed 1 wt.% MWCNT content along with varying nSiC additions in the range of 0–4 wt.%, enabling a systematic evaluation of the effect of hybrid reinforcement on the overall material properties. Compared to pure aluminium, the composites exhibited significant improvements in mechanical and tribological properties, with the Al–1 wt.% MWCNT–4 wt.% nSiC composition showing the highest enhancement, achieving increases of ~149% in hardness and ~45% in compressive strength. Microstructural analysis revealed strong matrix–reinforcement bonding, notable grain refinement, and a largely uniform reinforcement distribution, with minor agglomeration at higher nSiC content. The hybrid nanocomposites also demonstrated superior wear resistance, while fractography indicated a transition from ductile fracture in pure aluminium to a mixed intergranular–transgranular mode, promoting effective load transfer and improved performance. Full article

This study examines the microspherical high-calcium fly ash (HCFA) and the high-strength binder material based on it by method of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS). The composition of 568 individual microspheres of the initial HCFA was determined and presented as ternary diagrams CaO–Al₂O₃–SiO₂ and CaO–FeO–SiO₂. The binder specimens have a compressive strength of 24–82 MPa at a curing time of 3–300 days. Their strength is close to that of CEM I 42.5N cement specimens with a curing time of up to 28 days, but exceeds it with a curing time of up to 300 days. The SEM-EDS method showed that the predominant composition of hydration products is concentrated in the high-calcium region of the CaO–Al₂O₃–SiO₂ diagram with a CaO content of 60–80%. The SiO₂ content in them is 15–30%, and their composition includes 1–15% Al₂O₃ and 5–14% FeO. It follows that the predominant products that provide the strength of the binder are calcium silicate hydrates with a CaO/SiO₂ ratio of 1.7 to 4.2. The results contribute to the data for development of models for predicting the effect of HCFA on the properties of composite binders. Full article

Ni/Siral catalysts with different Si/Al ratios were prepared by incipient wetness impregnation (IWI) to assess the impact of support composition on Ni²⁺ speciation and ethylene oligomerization (EO) performance. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (TPR), X-ray diffraction (XRD), NH₃ temperature-programmed desorption (TPD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with energy-dispersive X-ray (EDX) analysis, and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). The EO catalysts were tested in a fixed-bed reactor at 225 °C under 11 bar ethylene and at 120 °C under 26 bar ethylene. Ni/Siral-70 was the most active catalyst investigated, but Ni/Siral-30 also exhibited good performance. The active sites were inferred to be isolated Ni²⁺ ions on amorphous SiO₂-Al₂O₃ containing interstitial Al³⁺ ions that enhance Brønsted acidity; Ni/Siral-70 displayed the highest concentration of these sites based on CO DRIFTS. Formation of NiAl₂O₄ surface species limited the activity of Ni/Siral-30 and especially Ni/Siral-5. The catalysts were also tested using a simulated ethane oxidative dehydrogenation (ODH) product stream containing 44% ethylene, 44% ethane, 4.5% methane, 2% H₂, 4.5% CO₂, 0.9% propylene, and 0.1% CO. The simulated ODH mixture gave lower EO conversion than 50/50 ethylene/N₂ at 225 °C and 11 bar over Ni/Siral-30, consistent with catalyst poisoning. In contrast, EO conversion over the Ni/Siral-70 catalyst was unaffected under these conditions. Catalyst testing at 120 °C and 26 bar revealed catalyst poisoning by feed impurities for both catalysts. Low-temperature/high-pressure EO activity was not recovered by simple thermal regeneration of Ni/Siral-30 at 300 °C. Full article

Sintering additives play a decisive role in the densification behavior, mechanical properties, and thermal conductivity of silicon nitride ceramics. In this study, Mg₂Si and YH₂ were used as sintering additives for gas pressure sintering of silicon nitride based on the synergistic mechanism of “silicide silicon extraction-hydride dehydrogenation”. The regulation rules of the additives on ceramic densification, mechanical properties, and thermal conductivity were systematically investigated. Two optimization strategies were proposed for the technical route of replacing traditional oxide additives with non-oxide systems. (i) Rare-earth hydride YH₂ was used to replace traditional rare-earth oxides. It reacts with SiO₂ to achieve strong deoxidation and precisely regulate the liquid phase composition. (ii) Metal silicide Mg₂Si was used to replace metal oxides. It promotes the preferred growth of β-Si₃N₄ grains, consumes oxygen in the system, and reduces lattice defects. Mg₂Si introduces Si into the liquid phase, increasing the Si/O ratio, which lowers lattice oxygen content and supports higher thermal conductivity. YH₂ consumes SiO₂ on the Si₃N₄ surface, which reduces liquid phase oxygen content and inhibits lattice oxygen incorporation, promoting a liquid phase with a high N/O ratio. Compared with traditional Y₂O₃, YH₂ increases the Y₂O₃/SiO₂ ratio in the liquid phase. It promotes grain growth, reduces SiO₂ activity, and further improves the thermal conductivity of ceramics. Silicon nitride ceramics prepared by gas pressure sintering at 1750 °C with 3 wt.% Mg₂Si and 4 wt.% YH₂ composite additives exhibit the highest thermal conductivity of 87 W/(m·K), with a Vickers hardness of 14.36 GPa and a flexural strength of 643.15 MPa. This study provides an innovative idea for the preparation of high-performance silicon nitride heat dissipation substrates. Full article

Silicon-based anodes are considered promising alternatives to graphite anodes owing to their high theoretical lithium-storage capacity and abundant reserves. However, silicon nanoparticle anodes are severely limited by large volume expansion, unstable interfacial chemistry, and poor electrical connectivity during repeated lithiation/delithiation. Herein, we develop a yolk–shell N-doped carbon network (NCN) strategy to construct Si@void@NCN composites. The optimized Si@void@NCN-1 achieves a balanced architecture between void buffering and carbon network integrity, delivering a high initial discharge capacity of 1245.5 mAh g⁻¹ and an initial charge capacity of 735.8 mAh g⁻¹. It also demonstrates stable long-term cycling performance, retaining a reversible capacity of 402.5 mAh g⁻¹ after 500 cycles at 0.5 A g⁻¹ with a capacity retention of 68.66%, and shows improved rate reversibility and electrode structural stability, with an electrode thickness increase of only 80.4% after rate cycling, much lower than that of densely carbon-coated Si@C. Kinetic analysis, post-cycling structural characterization, and in situ EIS further reveal that the yolk–shell void-buffering structure and the N-doped three-dimensional conductive network act synergistically to mitigate Si volume expansion, enhance structural stability, and facilitate electron/ion transport. This study emphasizes the importance of integrating buffering structures with Si/C composites, providing guidance for the rational design of advanced silicon-based electrode materials. Full article

To further improve the high-temperature dry sliding performance of Si₃N₄ ceramics, a CrAlN transition layer was introduced to improve interfacial stability, while Ag was incorporated as a solid lubricant into the CrAlN matrix. The effects of Ag content on the microstructure and mechanical properties of the coatings were systematically examined, and the tribological performance was evaluated from 25 °C to 550 °C under dry sliding conditions. The Ag concentration increased with increasing Ag target power and affected the morphology, nanoparticle distribution, surface roughness, and mechanical properties of the coatings. Among the tested samples, the coating containing 9.6 at.% Ag exhibited a comparatively favorable combination of mechanical properties within the investigated composition range, with a hardness of 11.5 GPa, an H/E ratio of 0.0913, and an H³/E² value of 0.096 GPa. Tribological tests showed that the average coefficient of friction decreased from 0.32 at 25 °C to 0.12 at 550 °C. This reduction may be associated with temperature-assisted Ag redistribution toward the worn surface and the possible development of Ag-rich surface features at elevated temperatures. However, the wear rate increased with temperature, reaching 3.6 × 10⁻⁵ mm³/(N·m) at 550 °C, suggesting that friction reduction was accompanied by increased material removal and possible near-surface weakening. These results indicate that controlling Ag content is important for balancing friction reduction and wear resistance in ceramic-based self-lubricating coatings. Full article

In this study, La-doped TiO₂-SiO₂ composite films were deposited on glass substrates by radio-frequency magnetron sputtering. The evolution of microstructure and macroscopic properties was systematically investigated across an annealing temperature range of 350–650 °C. The results show that the La-doped TiO₂-SiO₂ composite structure effectively suppresses abnormal grain growth and delays the anatase-to-rutile phase transition, thereby improving the films’ high-temperature structural stability. Notably, the composite film annealed at 550 °C (LS-550) exhibits the highest anatase crystallinity and forms a dense, smooth (RMS = 1.37 nm), crack-free nanocrystalline network. In terms of wettability, the improved hydrophilicity is attributed to the combined effects of La incorporation and hydrophilic silanol (Si-OH) groups in the amorphous SiO₂ phase. As a result, the water contact angle of the LS-550 film decreases dramatically to 28.0°, indicating excellent hydrophilicity. Moreover, the LS-550 film demonstrates an optimal photocatalytic degradation efficiency of approximately 76% for methylene blue, significantly outperforming the pure TiO₂ film. Furthermore, the enhanced mechanical performance is associated with the combined effects of the SiO₂-containing amorphous phase and the finer microstructure induced by La incorporation. Consequently, the critical load (Lc) of the LS-550 film reaches 75.64 mN, significantly exceeding that of the pure TiO₂ film annealed at the same temperature (61.25 mN). In summary, the composite film annealed at 550 °C concurrently achieves high crystallographic thermal stability, robust interfacial mechanical durability, excellent surface hydrophilicity, and enhanced photocatalytic activity, thereby offering practical guidance for developing TiO₂-based coatings with self-cleaning potential for high-rise building curtain walls. Full article

This work presents the design of a $\beta$-Ga₂O₃ MOSFET incorporating a P-type Ga₂O₃ buffer layer on a high-thermal-conductivity AlN/SiC composite substrate. The electrical characteristics of the device were simulated using Sentaurus TCAD. Results demonstrate that the integration of the composite substrate effectively mitigates self-heating effects, reducing the peak temperature ($T_{\mathit{max}}$) from 776.5 K to 570.9 K at 300 K, while simultaneously increasing the threshold voltage ($V_{\mathit{th}}$) from −0.35 V to 1.52 V. Through systematic optimization of the P-Ga₂O₃ buffer layer thickness and doping concentration, the device achieves a breakdown voltage ($V_{\mathit{br}}$) of 4781 V, a power figure of merit (PFOM) of 2.18 GW/cm², an $I_{DS}$, on/off ratio of 9.20 × 10⁹, and cut-off/maximum oscillation frequencies ($f_{\mathit{t}}$/$f_{\mathit{max}}$) of 1.29 GHz and 1.40 GHz, respectively. These findings provide a theoretical foundation for developing $\beta$-Ga₂O₃-based power devices with high breakdown voltage, improved thermal conductivity, and low specific on-resistance ($R_{\mathit{on},\mathit{sp}}$). Full article

The development of polyolefin from bio-renewables has been considered an important subject in terms of circular economy. In this study, exploring the possibility of β-myrcene (MY) incorporation in propene copolymerization has been studied in the presence of various catalysts: phenoxide-modified half-titanocene, Cp’TiCl₂(O-2,6-ⁱPr₂-4-C₆H₃) [Cp’ = Cp* (C₅Me₅), Me₃SiC₅H₄], and ketimide-modified half-titanicene, Cp’TiCl₂(N=C^tBu₂) (Cp’ = Cp*, Cp). Among the complexes tested, the permethylated Cp* catalysts, Cp*TiCl₂(O-2,6-ⁱPr₂-4-C₆H₃) and Cp*TiCl₂(N=C^tBu₂), exhibited moderate catalytic activities in the copolymerizations, affording the copolymers up to 3 mol% MY incorporation. The other catalysts showed negligible activity in the attempted copolymerizations. The resulting copolymers were amorphous and possessed sole glass transition temperatures (T_g), suggesting uniform compositions; the T_g values decreased with increasing comonomer (MY) content, reaching values as low as −17 °C. The results introduce valuable insights into the structure–property relationships of myrcene-based copolymers and pave the way for the future designs of tailored molecular catalysts for the synthesis of biobased elastomers. Full article