Search Results (1,155)

This study explores a novel approach to enhance the surface properties of Ti-Al alloys for biomedical applications by creating a compositional gradient layer through aluminum deposition using Electrical Discharge Machining (EDM). The primary goal was to develop a metallurgically bonded intermetallic zone that supports strong adhesion and improved compatibility for subsequent hydroxyapatite (HA) deposition. Aluminum was deposited onto a Ti6Al4V substrate via EDM under controlled conditions, followed by thermal and thermochemical treatments to induce diffusion and intermetallic phase formation. Comprehensive analyses using optical and electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) revealed the formation of well-adhered layers composed of complex Ti-Al intermetallics such as TiAl₂ and TiAl₃, along with oxide phases including TiO₂ and Al₂O₃. Thermal and thermochemical treatments further improved surface hardness, reaching up to 1057 HV, and influenced the diffusion behavior of aluminum, titanium, and vanadium. Adhesion tests confirmed that the untreated and thermochemically treated layers exhibited superior mechanical stability, while thermal treatment alone led to brittleness and delamination. These findings demonstrate that a properly engineered intermediate aluminide layer can significantly improve the performance of bioceramic coatings, particularly HA, by providing enhanced structural integrity and biocompatibility. Full article

Indium, widely used in indium–tin oxide (ITO) coatings for liquid crystal displays (LCDs), is a scarce and strategically important metal with increasing demand. Recycling waste LCD panels offers an efficient secondary source to address supply risks and environmental concerns. In this study, a hydrometallurgical flow sheet was developed under mild conditions for indium (In) recovery. Leaching trials with sulphuric acid at varying concentrations, pulp densities, temperatures, and times showed that 5% H₂SO₄ (v/v) with 100 g/L pulp density at 60 °C for 30 min achieved ~98% dissolution of In, while minimizing the co-leaching of Al and Sn. Kinetic analysis indicated a diffusion-controlled mechanism for In dissolution with an activation energy of 21.2 kJ mol⁻¹. The leached liquor was further purified through solvent extraction by 20% Cyanex 921 (v/v), achieving optimum In extraction at pH 2.5 with an organic-to-aqueous phase ratio of 1/3, reaching equilibrium within 15 min. The McCabe–Thiele plot shown indicates the complete In extraction in two stages. FT-IR studies confirmed the In-extractant bonding at optimized conditions. 10% H₂SO₄ (v/v) was used for the stripping of In from the loaded organic, ensuring nearly complete back-transfer of indium with excellent phase separation. The integrated process yielded ~97% In recovery in stripping. The pure salt of Indium could be obtained by evaporation/crystallization of pure indium solution. The developed process has the potential to be transferred for commercial exploitation after scale-up and pilot trial. Full article

This study systematically investigates the influence of 3D printing parameters on the surface morphology and coating performance of polylactic acid (PLA) substrates finished with traditional Chinese lacquer. PLA specimens were fabricated using fused deposition modeling (FDM) with varying print speeds, layer heights, and infill densities, followed by natural lacquer coating and controlled curing. Surface roughness, gloss, adhesion, and wear resistance were evaluated through standardized tests, while microstructural analysis using SEM revealed the interfacial morphology and film uniformity. Results indicate that layer height is the most dominant factor, exerting significant effects on all surface and coating properties. Increasing layer height led to higher surface roughness, which in turn reduced gloss due to enhanced diffuse scattering but improved adhesion and wear resistance through stronger mechanical interlocking. Print speed showed a secondary influence on adhesion, attributed to its effect on interlayer bonding and surface porosity, while infill density exhibited minimal influence except on wear resistance. The application of Chinese lacquer significantly reduced surface irregularities owing to its excellent self-leveling and gap-filling capabilities, producing smooth, durable, and well-adhered coatings. Overall, the study demonstrates that integrating traditional lacquer with modern FDM technology provides a sustainable and high-performance finishing solution for 3D-printed PLA, bridging cultural craftsmanship with advanced additive manufacturing for potential applications in decorative, protective, and eco-friendly products. Full article

Deicing salt effectively melts ice and snow to maintain traffic flow in seasonal freezing zones, but its erosion effect compromises the water stability and structural integrity of asphalt pavements. To comprehensively explore the impacts of salt erosion on the interfacial behaviors of rubber asphalt–aggregate systems, this study developed a multiscale characterization method integrating a macroscopic mechanical test, microscopic tests, and molecular dynamics (MD) simulations. Firstly, laboratory-controlled salt–freeze–thaw cycles were employed to simulate field conditions, followed by quantitative evaluation of interfacial bonding properties through pull-out tests. Subsequently, the atomic force microscopy (AFM) and Fourier transform infrared spectrometer (FTIR) tests were conducted to characterize the microscopic morphology evolution and chemical functional group transformations, respectively. Moreover, by combining the diffusion coefficients of water molecules, salt solution ions, and asphalt components, the mechanism of interfacial salt erosion was elucidated. The results demonstrate that increasing NaCl concentration and freeze–thaw cycles progressively reduces interfacial pull-out strength and fracture energy, with NaCl-induced damage becoming limited after twelve salt–freeze–thaw cycles. In detail, with exposure to 15 freeze–thaw cycles in 6% NaCl solution, the pull-out strength and fracture energy of the rubber asphalt–limestone aggregate decrease by 50.47% and 51.57%, respectively. At this stage, rubber asphalt exhibits 65.42% and 52.34% increases in carbonyl and sulfoxide indexes, respectively, contrasted by 49.24% and 42.5% decreases in aromatic and aliphatic indexes. Long-term exposure to salt–freeze–thaw conditions promotes phase homogenization, ultimately reducing surface roughness and causing rubber asphalt to resemble matrix asphalt morphologically. At the rubber asphalt–NaCl solution–aggregate interface, the diffusion of Na⁺ is faster than that of Cl⁻. Meanwhile, compared with other asphalt components, saturates exhibit notably enhanced mobility under salt erosion conditions. The synergistic effects of accelerated aging, salt crystallization pressure, and enhanced ionic diffusion jointly induce the deterioration of interfacial bonding, which accounts for the decrease in macroscopic pull-out strength. This multiscale investigation advances understanding of salt-induced deterioration while providing practical insights for developing durable asphalt mixtures in cold regions. Full article

The organic/inorganic hybrid compound bis(2-amino-6-bromopyridinium) tetrachloridocuprate(II) (HABPy)₂[CuCl₄] was synthesized in crystalline form in a 77% yield from aqueous HCl solutions containing Cu(OAc)₂ and 2-amino-6-bromopyridine (ABPy). Single-crystal X-ray diffraction analysis revealed that the compound crystallizes in the monoclinic, centrosymmetric space group C2/c. The Cu atom shows a distorted tetrahedral coordination geometry with a τ₄ value of 0.69 (τ₄ = 1 for a perfect tetrahedron). The structure consists of organic (HABPy)⁺ cation layers at z = 0 and z = ½, alternating with inorganic [CuCl₄]²⁻ dianion layers at z = ¼ and z = ¾. These layers, parallel to the (001) plane, are interconnected by a plethora of supramolecular forces such as N–H···Cl hydrogen bonds, forming a three-dimensional network. Powder X-ray diffraction confirmed the purity of the synthesized bulk material. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy support the protonation of the pyridine N atom. Hirshfeld surface analysis allowed us to further study the supramolecular forces in the crystal structure. The material shows purely paramagnetic behavior according to S = ½ with an effective magnetic moment µ_eff of 1.85 µB and a g factor of 2.14, in keeping with magnetically isolated [CuCl₄]²⁻ dianions. UV-vis diffuse reflectance spectroscopy of the orange-red material showed a tiny band at 314 nm and an intense band peaking at 622 nm. The optical gap was found to be 2.25 eV. The photoluminescence spectrum shows a partially structured band with maxima at 416 and 436 nm when irradiating at 370 nm, the wavelength of the maximum band found in the excitation spectrum. Full article

Biodegradable composites obtained by reinforcing thermoplastic starch (TPS) with lignocellulosic fibers show great potential, but their strong sensitivity to water still limits practical applications. Among possible reinforcements, Helianthus tuberosus (topinambur) represents an underutilized agricultural residue that has been scarcely explored in this context. In this work, we demonstrate for the first time that topinambur fiber can improve the water vapor barrier properties of cassava starch films, while also providing a detailed analysis of sorption isotherms and the humidity-dependent relationship between surface roughness and contact angle, aspects rarely addressed in previous studies. SEM revealed uniform fiber dispersion and integration. Water sorption kinetics showed that fiber addition reduces both hydration and sorption time constant, indicating lower water affinity and greater water mobility. Water sorption isotherms confirmed that fiber incorporation significantly alters overall hydration and water–matrix interactions, revealing reduced effective water solubility in films. Water vapor permeability also decreased with fiber addition, mainly due to decreased water solubility, rather than changes in water diffusivity. While fiber addition enhanced surface-water repellency across all humidity levels, roughness exhibited a humidity-dependent response FTIR analysis confirmed fiber–matrix compatibility and suggested new hydrogen bonding. Overall, these findings identify topinambur fiber as a novel reinforcement for designing biodegradable films with improved humidity resistance for agroecological applications. Full article

Power modules in silicon carbide (SiC)-based modular multilevel converters (MMCs) suffer from notably severe thermal imbalance and localized overheating. This paper puts forward an asymmetric SiC power module with direct integration of a vapor chamber (VC), designed to balance the thermal distribution inside MMC SMs. Specifically, the chips on the lower side of the HBSM are soldered onto a VC, which is additionally mounted on the direct bonding copper (DBC). Endowed with merits such as favorable temperature uniformity, exceptional thermal conductivity, compact size, flexible design, high integration level, and reasonable cost, the VC serves as an outstanding heat diffuser significantly expanding the effective thermal conduction area and reducing thermal resistance. Moreover, in this structure, the VC also functions as a conductor for device current. Finite element method (FEM) simulation results reveal that the proposed structure can notably reduce the hotspot temperature (from 109 $°\mathrm{C}$ to 71.8 $°\mathrm{C}$), the maximum temperature difference among chips (from 45 $°\mathrm{C}$ to 13.89 $°\mathrm{C}$), and the low-frequency temperature swing (TSL) (from 68 $°\mathrm{C}$ to 38 $°\mathrm{C}$). Consequently, the issues of localized overheating and thermal imbalance in SiC-MMC SMs are effectively addressed. Lifetime analysis further indicates that the proposed structure can reduce the annual damage rate of the chip solder layer by 92.6%. Full article

This study explores the influence of vibration timing on the performance of high early-strength cement-based composites used in bridge wet joints. A series of experimental techniques, including SEM, MIP, and RCM tests, were employed to evaluate microstructural evolution, mechanical properties, and durability. The results indicate that vibration applied between the initial and final setting phases has a critical impact, significantly reducing early-age compressive, flexural, and bond strengths. This deterioration is mainly attributed to micro-crack formation and enhanced pore connectivity, as confirmed by SEM and MIP analyses. Moreover, vibration markedly increases the chloride diffusion coefficient, particularly in mixtures with higher water-to-binder ratios, thereby raising long-term durability concerns. These findings underscore the necessity of optimizing mix proportions and strictly controlling vibration timing to ensure both the mechanical performance and service life of high early-strength cement composites in bridge construction. The study provides practical insights for the design and application of durable, resilient bridge wet joints. Full article

The high-strength aluminum alloy 7B04 used in aircraft structures poses challenges in welding. In this study, 7075 aluminum alloy powder is used as an interlayer to strengthen the vacuum diffusion bonding (DB) joint of 7B04 aluminum alloy. Surface treatments with plasma activation before DB can effectively increase the bonding rate and lap shear strength (LSS) of the joint. The effects of DB temperature, pressure, and holding time on the joint LSS were analyzed by developing a quadratic regression model based on the response surface method (RSM). The model’s determination coefficient reached 99.52%, with a relative error of about 5%, making it suitable for 7B04 aluminum alloy DB process parameters optimization and joint performance prediction. Two sets of process parameters (505 °C-5.7 h-4.5 MPa and 515 °C-7.5 h-4.4 MPa) were acquired using the satisfaction function optimization method. Experimental results confirmed that the error between measured and predicted LSS is approximately 5%, and a higher LSS of 174 MPa was achieved at 515 °C-7.5 h-4.4 MPa. Full article

Thermal barrier coatings (TBCs) extend gas-turbine blade lifetime by improving high-temperature oxidation resistance and mechanical performance. We investigated the microstructural evolution, TGO growth, and Al depletion in air-plasma-sprayed (APS) single-layer YSZ top coat over a NiCrCoAlY bond coat on Ni-based superalloy circular plates, heat treated isothermally at 850 °C and 1000 °C for 50–5000 h. Cross-sectional SEM/EDS analysis showed TGO quadratic thickening kinetics at both temperatures, reaching ~10 µm at 1000 °C/5000 h, the growth rate of which was ~5.8 times higher than at 850 °C. On top of the single-layer TGO of Al₂O₃ observed from the onset, a NiCrCo oxide layer appeared and grew from ≥500 h at 850 °C, with increasing growth rate and cracking. The layer configuration of the YSZ top coat, the TGO of Al₂O₃, and the bond coat (comprising β-NiAl and γ-NiCr) on top of GTD111, showed an Al concentration gradient in the bond coat starting at 850 °C for 250 h, which intensified with increased duration and temperature. The decrease in Al concentration in the bond coat and the growth of TGO are due to the dissolution of β-NiAl and subsequent Al diffusion to the Al₂O₃ TGO. Full article

Molecular dynamics simulations were conducted using the attachment energy (AE) model to investigate the growth morphology of lead 2,4,6-trinitrororesorcinate (LTNR, lead styphnate) under vacuum and different solvents. The adsorption energy of LTNR on (001), (110), (011), (020), (111), (200), and (201) crystal planes were calculated. Meanwhile, the crystal morphology in solvents of ethanol, toluene, dichloromethane, acetone, dimethyl sulfoxide (DMSO), and water at 298 K was predicted by calculating the interaction energies between the solvents and crystal planes. The calculated results show that the morphology of LTNR crystals in different solvents is significantly different. In toluene, LTNR crystal morphologies are flat, while in pure solvents of ethanol, acetone, and DMSO, the number of crystal planes increases, and the crystal thickness is larger. In the water, LTNR tends to form tabular crystals, which is similar to the experimental results. Both radial distribution function (RDF) and mean squared displacement (MSD) analyses reveal that hydrogen bonding dominates the interactions between LTNR and solvent molecules. Solvent molecules with higher diffusion coefficients exhibit increased desorption tendencies from crystal surfaces, which may reduce their inhibitory effects on specific crystallographic planes. However, no direct correlation exists between solvent diffusion coefficients and crystal plane growth rates, suggesting that surface attachment kinetics or interfacial energy barriers play a more critical role in crystal growth. Full article

A sheet-type sinter-bonding material was developed to form thermally stable and highly heat-conductive joints suitable for wide-bandgap (WBG) semiconductor dies and high-heat-flux devices, and its bonding characteristics were investigated. To enhance the cost-competitiveness of the bonding material, Ag-coated Cu (Cu@Ag) particles were employed as fillers instead of conventional Ag particles. To facilitate accelerated sintering, a bimodal particle size distribution comprising several micron- and submicron-sized particles was adopted by synthesizing and mixing both size ranges. For sheet fabrication, a decomposable resin was used as the essential binder component, which could be removed during the bonding process via thermal decomposition. This approach enabled the formation of a sintered bond line composed entirely of Cu@Ag particles. Thermogravimetric and differential thermal analyses revealed that the decomposition of the resin in the sheet occurred within the temperature range of 290–340 °C. Consequently, sinter-bonding conducted at 350 °C and 370 °C exhibited significantly superior bondability compared to bonding at 330 °C. In particular, sinter-bonding at 350 °C for just 60 s resulted in a highly densified joint microstructure with a low porosity of 7.6% and high shear strength exceeding 25 MPa. The formation of the bond line was initiated by sintering between the outer Ag shells of the adjacent particles. However, with increasing bonding time or temperature, sintering driven by Cu diffusion from the particle cores to the outer Ag shells, particularly in the submicron-sized particles, was progressively enhanced. These results obtained from the fabricated sheet-type materials demonstrate that, even with the use of resin, rapid solid-state sintering between filler particles combined with the removal of resin through decomposition enables the formation of a metallic bond line with excellent thermal conductivity. Full article

In this article, the mechanism of relaxation polarization currents occurring at a constant temperature (isothermal process) in crystals with ionic-molecular chemical bonds (CIMBs) in an alternating electric field was investigated. Methods of the quasi-classical kinetic theory of dielectric relaxation, based on solutions of the nonlinear system of Fokker–Planck and Poisson equations (for the blocking electrode model) and perturbation theory (by expanding into an infinite series in powers of a dimensionless small parameter) were used. Generalized nonlinear mathematical expressions for calculating the complex amplitudes of relaxation modes of the volume-charge distribution of the main charge carriers (ions, protons, water molecules, etc.) were obtained. On this basis, formulas for the current density of relaxation polarization (for transient processes in a dielectric) in the k-th approximation of perturbation theory were constructed. The isothermal polarization currents are investigated in detail in the first four approximations (k = 1, 2, 3, 4) of perturbation theory. These expressions will be applied in the future to compare the results of theory and experiment, in analytical studies of the kinetics of isothermal ion-relaxation (in crystals with hydrogen bonds (HBC), proton-relaxation) polarization and in calculating the parameters of relaxers (molecular characteristics of charge carriers and crystal lattice parameters) in a wide range of field parameters (0.1–1000 MV/m) and temperatures (1–1550 K). Asymptotic (far from transient processes) recurrent formulas are constructed for complex amplitudes of relaxation modes and for the polarization current density in an arbitrary approximation k of perturbation theory with a multiplicity r by the polarizing field (a multiple of the fundamental frequency of the field). The high degree of reliability of the theoretical results obtained is justified by the complete agreement of the equations of the mathematical model for transient and stationary processes in the system with a harmonic external disturbance. This work is of a theoretical nature and is focused on the construction and analysis of nonlinear properties of a physical and mathematical model of isothermal ion-relaxation polarization in CIMB crystals under various parameters of electrical and temperature effects. The theoretical foundations for research (construction of equations and working formulas, algorithms, and computer programs for numerical calculations) of nonlinear kinetic phenomena during thermally stimulated relaxation polarization have been laid. This allows, with a higher degree of resolution of measuring instruments, to reveal the physical mechanisms of dielectric relaxation and conductivity and to calculate the parameters of a wide class of relaxators in dielectrics in a wide experimental temperature range (25–550 K). Full article

As 3D stacking technologies advance, low-temperature hybrid Cu bonding has become essential for fine-pitch integration. This study focuses on evaluating Pd nanolayers deposited by electroless plating (ELP) on Cu surfaces and compares them to electroplated (EP) Pd to assess their suitability for hybrid bonding. Pd nanolayers (5~7 nm) were deposited on Cu films, and their surface morphology, crystallinity, and chemical composition were characterized using AFM, TEM, GIXRD, and XPS. EP-Pd layers exhibited lower roughness and larger grain size, acting as effective Cu diffusion barriers. In contrast, ELP-Pd layers showed small grains, higher surface roughness, and partial Cu diffusion and oxidation. At 200 °C, both Pd layers enabled bonding, but ELP-Pd samples achieved more uniform and continuous interfaces with thinner copper oxide layers. Shear testing revealed that ELP-Pd samples exhibited higher average bonding strength (20.58 MPa) and lower variability compared to EP-Pd (16.47 MPa). The improved bonding performance of ELP-Pd is attributed to its grain-boundary-driven diffusion and uniform interface formation. These findings highlight the potential of electroless Pd as a passivation layer for low-temperature hybrid Cu bonding and underscore the importance of optimizing pre-bonding surface treatments for improved bonding quality. Full article

Objective: This study aimed to evaluate the effect of incorporating bioactive particles (montmorillonite loaded with chlorhexidine, MMT/CHX) and different concentrations of silica nanoparticles (0%, 3%, 5%, 7%, 10%, and 15 wt%) into a universal dental adhesive on its degree of conversion, bond strength, water sorption, solubility, and antimicrobial activity. Materials and Methods: A universal adhesive was modified with 1 wt% MMT/CHX and varying amounts of silica nanoparticles. Degree of conversion was analyzed by Fourier transform infrared spectroscopy (FTIR), and microtensile bond strength was evaluated at 24 h, 6 months, and 12 months after water storage. Water sorption and solubility were measured according to ISO 4049, and antibacterial activity was tested against Streptococcus mutans using the agar diffusion method. Results: All experimental adhesives containing ≥7% silica showed significantly reduced water sorption and solubility. The presence of MMT/CHX imparted consistent antimicrobial activity across all experimental groups. Degree of conversion remained stable across all groups and storage periods. Notably, after 12 months, only the experimental groups maintained or improved bond strength, while the control group showed a significant reduction. Failure mode analysis indicated increased mechanical integrity with higher filler content. Conclusions: Incorporating 1 wt% MMT/CHX and ≥7 wt% silica into a universal adhesive improved long-term bond strength, reduced degradation, and introduced antibacterial properties without compromising polymer conversion. These findings support the potential of developing durable, bioactive adhesive systems for restorative dentistry. Clinical Significance: The incorporation of bioactive and reinforcing nanoparticles into universal adhesives enhances bond durability and introduces antibacterial properties without compromising polymerization. This innovation may lead to longer-lasting restorations and reduced risk of secondary caries in clinical practice. Full article