Search Results (1,365)

Adhesive fracture in layered structures is governed by subsurface crack evolution that cannot be accessed using surface-based diagnostics. Methods such as digital image correlation and optical spectroscopy measure surface deformation but implicitly assume a straight and uniform crack front, an assumption that becomes invalid for interfacial fracture with wide crack openings and asymmetric propagation. In this work, terahertz time-domain spectroscopy (THz-TDS) is combined with double-cantilever beam testing to directly map subsurface crack-front geometry in opaque adhesive joints. A strontium titanate-doped epoxy is used to enhance dielectric contrast. Multilayer refractive index extraction, pulse deconvolution, and diffusion-based image enhancement are employed to separate overlapping terahertz echoes and reconstruct two-dimensional delay maps of interfacial separation. The measured crack geometry is coupled with load–displacement data and augmented beam theory to compute spatially averaged stresses and energy release rates. The measurements resolve crack openings down to approximately 100 μm and reveal pronounced width-wise non-uniform crack advance and crack-front curvature during stable growth. These observations demonstrate that surface-based crack-length measurements can either underpredict or overpredict fracture toughness depending on the measurement location. Fracture toughness values derived from width-averaged subsurface crack fronts agree with J-integral estimates obtained from surface digital image correlation. Signal-to-noise limitations near the crack tip define the primary resolution limit. The results establish THz-TDS as a quantitative tool for subsurface fracture mechanics and provide a framework for physically representative toughness measurements in layered and bonded structures. Full article

High electrostrain, excellent thermal stability, and low hysteresis are critical requirements for advanced high-precision actuators. However, simultaneously achieving these synergistic properties in lead-free ferroelectric ceramics remains a significant challenge. In this work, a targeted B-site doping strategy was employed to develop novel lead-free (0.99-x)BaTiO₃-xBaZrO₃-0.01Bi(Zn_2/3Nb_1/3)O₃ (BT-xBZ-BZN, x = 0–0.2) ceramics. Systematic investigation identified optimal Zr⁴⁺ substitution at x = 0.1, which yielded an outstanding combination of electromechanical properties. For this optimal composition, a high unipolar electrostrain (S_max = 0.11%) was achieved at 50 kV/cm, accompanied by an ultra-low hysteresis (H_S = 1.9%). Concurrently, a large electrostrictive coefficient (Q₃₃ = 0.0405 m⁴/C²) was determined, demonstrating excellent thermal robustness with less than 10% variation across a broad temperature range of 30–120 °C. This superior comprehensive performance is attributed to a composition-driven evolution from a long-range ferroelectric to a pseudocubic relaxor state. In this state, the dominant electrostrictive effect, propelled by reversible dynamics of polar nanoregions (PNRs), minimizes irreversible domain switching. These findings not only present BT-xBZ-BZN (x = 0.1) as a highly promising lead-free candidate for high-precision, low-loss actuator devices, but also provide a viable design strategy for developing high-performance electrostrictive materials with synergistic large strain and superior thermal stability. Full article

We present a rapid, energy-efficient, and ecofriendly route for the synthesis of alkaline earth titanate perovskites—CaTiO₃, SrTiO₃, and BaTiO₃—using an affordable, commercially available CO₂ laser engraver, commonly found in makerspaces and small-scale workshops. The method involves direct laser irradiation of compacted pellets composed of low-cost, abundant, and non-toxic precursors: TiO₂ and alkaline earth carbonates (CaCO₃, SrCO₃, BaCO₃). CaTiO₃ and BaTiO₃ were synthesized with phase purities exceeding 97%, eliminating the need for conventional high-temperature furnaces or prolonged thermal treatments. X-ray diffraction (XRD) coupled with Rietveld refinement confirmed the formation of orthorhombic CaTiO₃ (Pbnm), cubic SrTiO₃ (Pm3⁻m), and tetragonal BaTiO₃ (P4mm). Raman spectroscopy independently corroborated the perovskite structures, revealing vibrational fingerprints consistent with the expected crystal symmetries and Ti–O bonding environments. All samples contained only small amounts of unreacted anatase TiO₂, while BaTiO₃ exhibited a partially amorphous fraction, attributed to the sluggish crystallization kinetics of the Ba–Ti system and the rapid quenching inherent to laser processing. Transmission electron microscopy (TEM) revealed nanoparticles with average sizes of 50–150 nm, indicative of localized melting followed by ultrafast solidification. This solvent-free, low-energy, and highly accessible approach, enabled by widely available desktop laser systems, demonstrates exceptional simplicity, scalability, and sustainability. It offers a compelling alternative to conventional ceramic processing, with broad potential for the fabrication of functional oxides in applications ranging from electronics to photocatalysis. Full article

Flexible and wearable pressure sensors are essential for monitoring of human motion and are distinguished by their increased sensitivity and outstanding mechanical robustness. In this study, we systematically engineered a flexible and wearable pressure sensor with a multilayer conductive architecture, arranging a sponge substrate coated in a consecutive manner with a barium zirconium titanate thin film, followed by polypyrrole, multiwalled carbon nanotubes, and eventually polydimethylsiloxane. The foundation of additional conductive pathways is enabled via the utilization of a porous framework and the hierarchical arrangement, causing the achievement of an excellent sensitivity of 9.71 kPa^–1 (0–9 kPa), a rapid 40 ms response time, and a fast 60 ms recovery period, combined with a particularly low detection limit (125 Pa) and an extended pressure range from 0 to 225 kPa. Furthermore, the integration of a rough and porous barium zirconium titanate/barium titanate thin film is expected to deliver a voltage output (1.25 V) through piezoelectric working mechanisms. This study possesses the potential to provide an innovative architecture design for advancing the development of future electronic devices for health and sports monitoring. Full article

We report the synthesis and multifunctional characterization of copper-reinforced Ba_0.85Sr_0.15TiO₃ (BST) ceramic composites with Cu contents ranging from 0 to 40 wt%, prepared by a sol–gel route and densified using spark plasma sintering (SPS). X-ray diffraction and FT-IR analyses confirm the coexistence of cubic and tetragonal BST phases, while Cu remains as a chemically separate metallic phase without detectable interfacial reaction products. Microstructural observations reveal abnormal grain growth induced by localized liquid-phase-assisted sintering and progressive Cu agglomeration at higher loadings. Scanning electron microscopy reveals abnormal grain growth, with the average BST grain size increasing from approximately 3.1 µm in pure BST to about 5.2 µm in BST–Cu40% composites. Optical measurements show a continuous reduction in the effective optical bandgap (apparent absorption edge) from 3.10 eV for pure BST to 2.01 eV for BST–Cu40%, attributed to interfacial electronic states, defect-related absorption, and enhanced scattering rather than Cu lattice substitution. Electrical characterization reveals a percolation threshold at approximately 30 wt% Cu, where AC conductivity and dielectric permittivity reach their maximum values. Impedance spectroscopy and equivalent-circuit analysis demonstrate strong Maxwell–Wagner interfacial polarization, yielding a maximum permittivity of ~1.2 × 10⁵ at 1 kHz for BST–Cu30%. At higher Cu contents, conductivity and permittivity decrease due to disrupted Cu connectivity and increased porosity. These findings establish BST–Cu composites as tunable ceramic–metal systems with enhanced dielectric and optical responses, demonstrating potential for specialized high-capacitance decoupling applications where giant permittivity is prioritized over low dielectric loss. Full article

The rising global demand for prosthetic limbs, driven by approximately 185,000 amputations annually in the United States, underscores the need for innovative and cost-efficient solutions. This study explores the integration of hybrid materials, advanced 3D printing techniques, and smart sensing technologies to enhance prosthetic finger production. A Taguchi-based design of experiments (DoE) approach using an L09 orthogonal array was employed to systematically evaluate the effects of infill density, infill pattern, and print speed on the tensile behavior of FDM-printed PLA components. Findings reveal that higher infill densities (90%) and hexagonal patterns significantly enhance yield strength, ultimate tensile strength, and stiffness. Additionally, the rheological properties of polydimethylsiloxane (PDMS) were optimized at various temperatures (30–70 °C), characterizing its viscosity, shear-thinning factors, and stress behaviors for 3D bioprinting of flexible sensors. Barium titanate (BaTiO₃) was incorporated into PDMS to fabricate a flexible tactile sensor, achieving reliable open-circuit voltage readings under applied forces. Structural and functional components of the finger prosthesis were fabricated using FDM, stereolithography (SLA), and extrusion-based bioprinting (EBP) and assembled into a functional prototype. This research demonstrates the feasibility of integrating hybrid materials and advanced printing methodologies to create cost-effective, high-performance prosthetic components with enhanced mechanical properties and embedded sensing capabilities. Full article

In this present study, sodium- and strontium-modified bismuth titanate—Bi_0.5Na_0.5TiO₃ (BNT) and Bi_0.5Sr_0.5TiO₃ (BST)—were synthesized using the auto-combustion technique with citric acid (C₆H₈O₇) and glycine (C₂H₅NO₂) as fuels in an optimized ratio of 1.5:1. The resulting powders were characterized using X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, UV–Visible diffuse reflectance spectroscopy (DRS), and Fourier-transform infrared (FT-IR) spectroscopy. The electrical behavior of the samples was studied using an LCR meter. XRD analysis confirmed the formation of a single-phase perovskite structure with average crystallite sizes of 18.60 nm for BNT and 22.03 nm for BST, attributed to the difference in ionic radii between Na⁺ and Sr²⁺. An increase in crystallite size was accompanied by a corresponding increase in lattice parameters and unit-cell volume. The Williamson–Hall analysis further validated the strain-size contributions. EDX (Energy-Dispersive X-ray analysis) results confirmed successful incorporation of Na⁺ and Sr²⁺ without detectable impurity phases. Optical studies revealed distinct absorption peaks at 341 nm for BNT and 374 nm for BST, and the optical bandgap (E_g), calculated using Tauc’s relation, was found to be 2.6 eV and 2.0 eV, respectively. FT-IR spectra exhibited characteristic Ti-O vibrational bands in the range of 420–720 cm⁻¹, consistent with the perovskite structure. For electrical characterization, the powders were pelletized under 3-ton pressure and sintered at 1000 °C for 3 h. The dielectric constant (ε_r), dielectric loss (tan δ), and ac conductivity (σ) of both samples increased with frequency. The combined structural, optical, and electrical results indicate that the optimized compositions of BNT and BST possess properties suitable for use in capacitors and other energy-storage applications. Full article

Titanium compounds are an integral component for paint pigments, food additives (E171), catalysts, precursors for resistant structural materials, medicine, and water, and air purification and disinfection processes. A new and rather promising trend for titanium dioxide production is obtaining it from minerals with magnesium titanium structure. Magnesium titanates obtained by pyrometallurgical processing of quartz–leucoxene concentrate (oil sandstones). It was found that the optimal pyrometallurgical processing conditions were 4 h and a temperature of 1425–1450 °C, with TiO₂ → Mg_XTi_YO_Z conversion exceeding 95%, and that sulfation of the magnesium titanate mixture with 60–70% H₂SO₄ for 150–210 min allows a 95% extraction of titanium compounds into solution. Investigation of the mechanism of titanium compound precipitation from Mg-Ti-containing sulfuric acid solutions revealed that in the pH range from 3 to 6, only titanium compounds were extracted from solution, while coprecipitation of magnesium compounds begins only at pH above 6.5. The product obtained by precipitation is titanium dioxide with an anatase structure, with particle distribution ranging from 0.8 to 5.0 µm and a developed surface area over 250 m²/g with mesopores characteristic of sorption materials. Full article

The Spt-Ada-Gcn5 acetyltransferase (SAGA) complex is a conserved transcriptional coactivator that coordinates histone modifications and transcriptional regulation in eukaryotes. In Cryptococcus neoformans, SAGA governs key virulence traits, yet the roles of several core scaffold subunits remain undefined. Here, we characterize the functional roles of Spt7, a core SAGA component, in C. neoformans. Comparative genomics revealed that C. neoformans Spt7 retains conserved histone fold and bromodomain motifs. Deletion of SPT7 produced pleiotropic phenotypes, including defective melanization and capsule formation, impaired titan cell development, and heightened sensitivity to thermal, metal, antifungal, and cell wall stresses. The spt7Δ mutant exhibited strong sensitivity to the echinocandin micafungin, implicating Spt7 in maintaining cell wall integrity. The spt7Δ mutant was avirulent in a murine inhalation model. At the chromatin level, SPT7 deletion disrupted SAGA-dependent histone post-translational modifications, increasing H2B ubiquitination while reducing H3K14ac and H3K18ac levels. Proteomic profiling revealed reduced abundance of ribosomal, mitochondrial, and translational proteins and upregulation of lipid metabolic and secretory pathway components. Collectively, our findings establish Spt7 as a central integrator of SAGA-mediated chromatin regulation, proteomic balance, and virulence in C. neoformans and highlight the SAGA core as a potential antifungal target. Full article

Bone regeneration relies on the coordinated interplay between mechanical and biological cues. Piezoelectric composites, capable of converting mechanical strain into electrical signals, offer a promising approach to stimulate osteogenesis. This study aimed to develop and characterize polycaprolactone (PCL) and barium titanate (BaTiO₃) composite scaffolds fabricated through thermally induced phase separation (TIPS), and to systematically evaluate the effects of polymer concentration and ceramic incorporation on scaffold morphology, porosity, mechanical properties, and cytocompatibility were systematically evaluated. The resulting scaffolds exhibited a highly porous, interconnected architecture, with 9% PCL formulation showing the most uniform morphology and consistent mechanical and biological behavior. Incorporation of BaTiO₃ did not alter pore structure or compromise cytocompatibility but slightly enhanced stiffness and surface uniformity. SEM-based image analysis confirmed homogeneous BaTiO₃ dispersion across all formulations. MTT assays and confocal microscopy demonstrated robust pre-osteoblast adhesion and spreading, particularly on denser composite scaffolds, confirming that the inclusion of BaTiO₃ supports a favorable environment for cell proliferation. Overall, optimizing polymer concentration and ceramic dispersion enables fabrication of structurally coherent, cytocompatible scaffolds. The findings establish structure–property–biology relationships that serve as a baseline for future investigations into the electromechanical behavior of PCL/BaTiO₃ scaffolds and their potential to promote osteogenic differentiation under physiological loading. Full article

Poly(vinylidene fluoride) (PVDF) nanofibers have emerged as promising materials for flexible piezoelectric sensors, yet their performance is fundamentally constrained by the limited formation and alignment of the electroactive β-phase. In this study, we report a phase-engineering strategy that integrates ionic functionalization, inorganic nanofiller incorporation, and post-fabrication corona poling to achieve enhanced crystalline ordering and electromechanical coupling in electrospun PVDF nanofibers. Tetrabutylammonium perchlorate increases solution conductivity, enabling uniform, bead-free fiber formation, while barium titanate nanoparticles act as nucleation centers that promote β-phase crystallization at the expense of the non-polar α-phase. Subsequent corona poling further aligns molecular dipoles and strengthens remnant polarization within both the PVDF matrix and embedded nanoparticles. Structural analyses confirm the synergistic evolution of crystalline phases, and piezoelectric measurements demonstrate a substantial increase in peak-to-peak output voltage under dynamic loading conditions. This combined phase-engineering approach provides a simple and scalable route to high-performance PVDF-based piezoelectric sensors and highlights the importance of coupling crystallization control with dipole alignment in designing next-generation wearable electromechanical materials. Full article

Background and Objectives: The insertion of endosseous implants requires the alveolar bone to be drilled, which produces alterations of the osseous neoalveolus approximately 1 mm deep, an area that will later be subjected to osseous renewal. The healing of the bone around the inserted implant is complex and depends on numerous factors, amongst which the size of the insertion orifice relative to the diameter of the implant, the design, and the pace and depth of the threads play an essential part. Therefore, the aim of this paper is to investigate from a histologic point of view the osseointegration of the implants inserted in a rabbit cortical bone by creating a 150 µm high healing chamber. Materials and Methods: 5 mm-long and 2 mm-wide titan implants were inserted into the femur of 15 12-month-old rabbits by using a drill with a 1.8 mm diameter, obtaining a spiralled healing chamber 150 µm high. The animals were euthanized after 7, 14, and 28 days according to effective legal and ethical protocols. The bone around the implants was severed 5 µm thick. After coloring with the Tricrom Goldner method, the sections that intercepted most centrally the intervention area were examined and photographed with an Olympus microscope. Results: The histologic result showed osseous healing within the healing chamber in the third to the endosteum of the implant after 7 days from the insertion. After 14 days, the osseous healing spread to 2/3 of the healing chamber. After 28 days, the whole healing chamber was occupied by bone. Conclusions: The healing chamber favored proper conditions for osseous healing, which began at the level of the endosteum. This statement is based on the histologic findings of bone formation after 7 days only in the third of the endosteum of the healing chamber. A 150 µm height of the healing chamber obtained in the rabbit cortical bone does not pose a risk of connective tissue proliferation. Full article

Light-controlled ion drag pumps have attracted considerable interest in soft robotics, biomedical engineering, and microelectromechanical systems (MEMS) due to their non-contact energy supply and high spatiotemporal controllability of light. However, experimental studies on their pumping performance and influencing factors remain limited. This study integrates the photoelectric effect with field emission phenomena to design and fabricate a light-controlled ion drag pump using lanthanum-modified lead zirconate titanate (PLZT) ceramic. The light-controlled pump enables non-contact energy transfer and fluid transport via high-energy laser irradiation. A series of experiments systematically investigate its pumping performance and key influencing factors. Results indicate that optimizing electrode structure and fluid channel design, along with increased light intensity, significantly enhances pumping performance. This work provides fundamental design guidelines for the application of light-controlled ion drag pumps in microfluidics, flexible robotics, and microdevice thermal management. Full article

The aim of this study was to evaluate structural changes and their impact on the functional properties of Ti-6Al-4V and Ti-6Al-7Nb titanium alloys produced by L-PBF. In the as-built condition, these alloys, despite high strength due to the presence of metastable α’ martensite, exhibit limited ductility. The samples were subjected to heat treatment at 850–1000 °C for 1 h, followed by aging at 500 °C for 4 h in an argon atmosphere. Analysis revealed a gradual microstructural transformation from the columnar structure characteristic of L-PBF to an equilibrium Widmanstätten microstructure. As a result of the decomposition of martensite and the formation of an α + β phase mixture, changes in microhardness and mechanical properties were observed. After heat treatment, the microhardness decreased by 15% for Ti-6Al-4V (from 427 ± 1 HV to 362 ± 25 HV) and by 12% for Ti-6Al-7Nb (from 408 ± 6 HV to 359 ± 15 HV). The Ti-6Al-7Nb alloy exhibited higher maximum elongation (7.7 ± 1.1%) than Ti-6Al-4V (4.8 ± 0.5%) due to a greater fraction of the β phase. The results highlight the critical role of the controlled α′→α + β transformation in tailoring the properties of titanium alloys and provide a basis for optimizing manufacturing processes for medical and aerospace components. Full article

This study presents the results of a study of the reaction interaction and contact angle during contact between a titanium melt and a calcium metatitanate substrate. It is shown that at temperatures slightly above the melting point, the titanium melt poorly wets the CaTiO₃ substrate surface. The contact angle and the onset temperature of active reaction vary depending on the fractional composition of the CaTiO₃ powders from which the substrates are made and their porosity. Under isothermal holding conditions below the onset temperature of active reaction, the contact angle changes insignificantly. At the onset temperature of the reaction interaction, after a short stabilization period of the contact angle, the reaction leads to rapid penetration of the molten droplet into the depth of the CaTiO₃ substrate and, in some cases, to the expulsion of a Ca-Ti-O liquid phase from the reaction zone. The interaction of titanium melt with calcium titanate is accompanied by a series of physicochemical reactions associated with the reaction interaction, which intensifies with increasing temperature and causes the restoration of calcium to a metallic state and the dissolution of oxygen in the titanium melt, as well as the formation of a liquid Ca-Ti-O layer in the transition zone. Full article