Mechanical reliability and size-dependent strength behavior remain critical concerns for CAD/CAM restorative materials. This study evaluated resin-based CAD/CAM materials, including resin composite blocks (RCBs) and nanoceramics. The influence of specimen size on flexural strength and the applicability of Weibull-based strength predictions were assessed by comparing experimental and Weibull-predicted values. Twelve CAD/CAM materials were investigated, including ten resin-based materials and two controls (lithium disilicate ceramic and polymethyl methacrylate). Rectangular specimens (1 × 4 × 14 mm and 1 × 12 × 14 mm) were tested using a three-point bending test. Flexural strength, modulus, and resilience were calculated. Reliability and size dependence were assessed using two-parameter Weibull statistics and effective-volume-based predictions. Data were analyzed using statistical tests selected according to data distribution characteristics (α = 0.05). RCBs exhibited higher flexural strength, modulus, and resilience than nanoceramics (p < 0.05). Weibull analysis indicated higher reliability and limited size dependence for RCBs, whereas nanoceramics showed greater variability. The ceramic control exhibited the expected reduction in strength with increasing specimen size. In contrast, resin-based materials showed inconsistent responses to changes in specimen size. Prediction error analysis revealed variable agreement between predicted and experimental values, indicating that agreement with classical Weibull assumptions was material-dependent. Resin-based CAD/CAM materials demonstrated limited size-dependent behavior compared with brittle ceramics. The reduced agreement between experimental and Weibull-predicted values suggests that effective-volume scaling may have limited applicability for these contemporary materials and should be interpreted cautiously on a material-specific basis.
Lithium disilicate-based glass-ceramics (LDC) are widely used for esthetic restorations, yet their surface and optical behavior can vary depending on the composition and surface treatment procedure. The purpose of this study was to compare the surface, colorimetric, and optical properties of LDC materials with different compositions after being subjected to polishing or glazing. Rectangular specimens were prepared by sectioning four compositions of LDC CAD/CAM blocks (IPS e.max CAD [IPS], Amber Mill [AM], Amber Mill Direct [AMD], Initial LiSi [ILS]). Baseline surface roughness (Ra), color, translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP) and gloss (GU) values were recorded. Each group was divided into two subgroups according to surface treatments, one undergoing glazing and the other polishing, followed by post-treatment measurements (n = 10). Color change (ΔE00) for each group was calculated based on the CIEDE2000 formula. In addition to baseline and final Ra, TP, CR, OP, and GU measurements, the changes in these parameters (ΔRa, ΔTP, ΔCR, ΔOP, and ΔGU) were calculated by subtracting the baseline values from the final values obtained after polishing or glazing. One extra specimen from each group was prepared for scanning electron microscopy (SEM) analysis. Mann-Whitney U, Kruskal-Wallis H, and Wilcoxon signed-rank tests were used for statistical analysis (α = 0.05). The surface, colorimetric, and optical properties differed significantly based on the type of LDC material and the surface treatment method. The Ra values of IPS, AMD, and ILS decreased significantly after glazing compared to polishing (p = 0.016), which was confirmed by SEM analysis. Both surface treatments significantly reduced Ra values compared with baseline across all material groups (all p ≤ 0.013). Glazing resulted in higher mean ΔE00 values than polishing for IPS (p = 0.011) and ILS (p = 0.0001). For IPS, TP values were lower in the glazed specimens than those that were polished (p = 0.001), whereas the opposite trend was observed for CR values (p = 0.001). Regardless of the LDC material type, glazing produced significantly lower OP values (all p ≤ 0.041) and higher GU values (all p ≤ 0.023) than polishing. Surface, colorimetric, and optical properties of LDC materials varied depending on the surface treatment method and material composition. While both surface treatments effectively reduced surface roughness, glazing enhanced surface gloss and opalescence more prominently, but induced material-specific color changes. Glazing also enhanced the translucency of IPS e.max CAD compared to other LDC materials.
To evaluate the effects of alumina airborne-particle abrasion, glass-bead airborne-particle abrasion, and hydrofluoric acid etching of intaglio surfaces on the color difference and translucency of a nano-hybrid ceramic after cementation to resin abutment specimens, and to analyze the relationships between surface roughness and these parameters. Thirty nano-hybrid ceramic discs were allocated to alumina airborne-particle abrasion (hereinafter called as AL), glass-bead abrasion (hereinafter called as GB), or 9.5% hydrofluoric acid etching (hereinafter called as ET) (n = 10, respectively). Surface roughness (Ra) was measured with a 3D confocal laser microscope. Treated specimens were cemented to 3D-printed resin abutment specimens with the same translucent resin cement, and CIELAB coordinates were recorded using a spectrophotometer with black and white backgrounds to calculate CIEDE2000 color difference (ΔE00) and translucency parameter (TP00). Surface microstructures and elemental compositions were assessed by field-emission scanning electron microscopy (hereinafter abbreviated as FE-SEM) and energy-dispersive x-ray spectroscopy (hereinafter abbreviated as EDS). Data were analyzed using one-way or Welch ANOVA with post hoc tests and Pearson correlation (α = 0.05). Ra decreased in the order of AL>GB > ET (p < 0.001). ET (with the lowest Ra) showed greater ΔE00 and lower TP00 than AL and GB (p < 0.001), though no significant correlations between Ra and either ΔE00 or TP00 were found in it. However, in AL and GB, larger ΔE00 and lower TP00 correlated with higher Ra (p < 0.05). Etched (ET) surfaces showed distinct open micro-porosity and reduced Si with increased F and Na. Hydrofluoric acid etching of the nano-hybrid ceramic intaglio surface resulted in greater color difference and lower translucency after cementation than alumina or glass-bead airborne-particle abrasion. Surface roughness was associated with ΔE00 and TP00 only in the airborne-particle abrasion groups. For nano-hybrid ceramic restorations, the intaglio surface-conditioning method can influence post-cementation color difference and translucency. Under the present in vitro conditions, alumina and glass-bead airborne-particle abrasion produced smaller color differences and higher translucency than the evaluated hydrofluoric acid-etching protocol, suggesting that these treatments may be more favorable when shade matching and translucency preservation are clinically prioritized.
Effluents from textile, leather, paper, food, and cosmetic industries are recognized as major sources of dye pollution, while antibiotic contamination primarily originates from pharmaceutical, medical, and aquaculture activities. Both forms of pollution pose significant environmental and public health risks, necessitating the development of advanced multifunctional materials for wastewater remediation. In this study, a novel 3D-printed SiO2-BaTiO3/SrTiO3-polymeric composite scaffold was developed, integrating a triple synergistic mechanism comprising adsorption, photocatalysis, and piezocatalysis for the efficient mitigation of methylene blue (MB) dye and tetracycline (TC) pollutants. The BaTiO3 and SrTiO3 nanoparticles were synthesized via a solution combustion method, while SiO2 was sustainably obtained from bagasse ash, exhibiting surface areas of 11.88, 4.77, and 74.16 m2/g, respectively. The 3D-printed porous architectures, precisely designed using computer-aided modeling, enhanced active surface accessibility and facilitated mass transfer, thereby improving overall catalytic efficiency. The SiO2-BaTiO3-polymer and SiO2-SrTiO3-polymer composites achieved over 60% MB removal by adsorption, 18% by photocatalytic degradation under UV illumination, and over 20% by piezocatalytic degradation under ultrasonic vibration, resulting in total degradation efficiencies exceeding 88% for MB and 85% for TC. The integration of waste-derived SiO2, functional titanate ceramics, and additive manufacturing underscores the novelty of this work, providing a sustainable and scalable pathway for next-generation wastewater treatment systems in alignment with the United Nations Sustainable Development Goals (SDGs).
The growing accumulation of industrial waste and the depletion of natural mineral resources underscore the need for sustainable approaches to producing ceramic and construction materials. Among the most promising secondary raw materials are coal combustion by-products and metallurgical slags, which are suitable for ceramic applications. This review summarizes recent advances in the use of coal ash, blast furnace and steelmaking slags, together with clay-based raw materials, for the fabrication of ceramic and composite materials. Special attention is given to the physicochemical properties of technogenic raw materials and their effects on sintering, porosity, densification, mechanical strength, and thermal stability. Modern processing methods, including pressing and high-temperature firing, are also discussed. The influence of key technological parameters, such as oxide composition, particle size distribution, firing temperature, and activation conditions, is analyzed. In addition, the review examines major challenges related to raw material heterogeneity, structural instability, thermal stress development, cracking, free CaO reactivity, and environmental risks associated with heavy metal leaching. Recent studies show that incorporating industrial waste into ceramic systems reduces waste disposal, natural resource consumption, energy use, and CO2 emissions, while promoting sustainable and resource-efficient technologies. Ash- and slag-based ceramics therefore remain highly promising materials for construction applications.
The growing volume of construction and demolition waste and the high carbon footprint of cement production have driven interest in waste-derived materials for sustainable concrete. This study presents a critical systematic review of the use of gypsum waste powder (GWP) and ceramic waste powder (CWP) as partial cement replacements, focusing on material mechanisms, performance limits, durability behaviour and sustainability trade-offs. The review follows PRISMA 2020 guidelines, and peer-reviewed studies published between 2015 and 2025 were systematically screened and synthesized. The review indicates that CWP exhibits a broader and more reliable performance window than GWP, attributed to its silica-rich composition, pozzolanic reactivity and microfilling effect. Cement replacement levels of approximately 10-20% CWP are consistently associated with improved compressive and flexural strength, reduced chloride penetration and enhanced durability under controlled curing conditions, whereas higher replacement levels require blending with reactive supplementary cementitious materials. In contrast, GWP demonstrates a narrower and exposure-sensitive applicability, with effective replacement typically limited to 10-15% due to sulphate-related risks affecting setting behaviour and long-term durability. From a sustainability perspective, partial cement replacement using GWP and CWP can reduce embodied CO₂ emissions by approximately 7-10% per 10% cement substitution, although net benefits depend strongly on processing energy, transportation distance and durability performance. Overall, this review establishes clear performance thresholds, failure mechanisms and applicability boundaries for GWP and CWP, providing decision-oriented guidance for sustainable concrete design and identifying key research needs related to durability, standardization and life cycle assessment.
In this work, to address the limitation of low strength and hardness of single-phase CoCrFeNi high-entropy alloy, SiC particles were introduced as a reinforcing phase to prepare CoCrFeNi matrix composites with SiC contents of 0 wt%, 1 wt%, 2.5 wt% and 5 wt% via spark plasma sintering (SPS). It was preliminarily predicted that SiC particles would be uniformly distributed along grain boundaries of the CoCrFeNi matrix. During sintering, partial SiC decomposes at high-temperature, high-activity interfaces, regulating carbide precipitation and phase structural evolution, while residual undecomposed SiC remains at grain boundaries to pin boundaries and refine grains, thereby synergistically enhancing mechanical properties and wear resistance. Microstructural characterization reveals that all samples maintain a face-centered cubic (FCC) solid-solution matrix, and samples with non-zero SiC addition contain Cr7C3 carbides, which are mostly distributed at grain boundaries. With the increase in SiC content, mechanical performance is remarkably improved compared with the unreinforced CoCrFeNi matrix: the hardness rises from 198.8 HV to 321.7 HV, the yield strength is greatly enhanced from 242.5 MPa to 673.4 MPa, and the tensile strength increases from 557.9 MPa to 755.7 MPa. The improved yield strength originates synergistically from grain refinement, solid-solution strengthening, grain-boundary strengthening and dislocation strengthening. By clarifying the influence of microstructural defects on critical shear stress (τ0) and normal fracture stress (σ0), the intrinsic mechanism governing tensile mechanical performance and ductile-brittle fracture transition was revealed. This optimized CoCrFeNi/SiC composite exhibits excellent strength-hardness comprehensive performance, showing promising application potential for high-load, wear-resistant and structural service components under severe tribological and pressure conditions.
Computer aided designed/ computer aided manufactured (CAD/CAM) materials offer diverse options for prosthetic rehabilitations, yet correlation between materials' surface properties and aging through chewing simulation needs characterization. The aim of this study is to measure and evaluate the effect of three body wear on three CAD/CAM materials (poly methylmethacrylate (PMMA), composite resin and polyether ether ketone (PEEK)) regarding their microhardness and surface roughness. Seventy-two disc-shaped specimens (20 × 6 mm) were fabricated (n = 24/ group) from PMMA (Yamahachi PMMA Disk), Nano-ceramic Composite (Grandio Blocs, VOCO), and PEEK (BioHPP, Bredent). Specimens were subjected to 120,000 chewing cycles in a chewing simulator using a 3-body wear protocol with a pumice slurry. Wear volume (mm3) was measured digitally. Surface roughness (µm) and Vickers hardness (VHN) were evaluated twice: at baseline and within the wear facets post-simulation. Data were analyzed using Two-way and One-way ANOVA (P-value < 0.05), and Pearson correlation was used to measure the relationship between properties. One-way ANOVA revealed a significant difference between material types (P = 0.000*), with composite exhibiting the lowest mean volume loss (0.08 mm3), significantly outperforming PEEK (0.23mm3) and PMMA (0.55 mm3). For surface roughness, a significant interaction was observed between material type and wear simulation (P = 0.000*), while there was no significant interaction between them on surface hardness (P = 0.89). Composite significantly outperformed PEEK and PMMA regarding all tested properties. The 3-body wear simulation induced significantly different volumetric loss across all groups, with the magnitude of loss largely dependent on the material's specific composition and baseline hardness. In addition, the surface roughness and microhardness of three investigated materials were considerably impacted by three-body wear. PMMA have the lowest wear resistance, lowest microhardness, and the greatest surface roughness both before and after wear, while composites with high filler loading and high microhardness have the highest wear resistance followed by PEEK. After wear, the surface roughness of the composite is acceptable.
Aramid nanofiber (ANF) composites are promising thermal interface materials due to their excellent mechanical and thermal stability, prominent electrical insulation properties, flame retardance and remarkable chemical corrosion resistance, making them capable of operating under extreme conditions. However, their low intrinsic thermal conductivity limits their application for heat dissipation in high-power electrical components. This review systematically summarizes recent advances in enhancing the thermal conductivity of ANF composites from three critical perspectives: filler selection and design, interface modification strategies, and construction of ordered thermal-conduction pathways. We summarize the advantages of composites with different types of thermally conductive fillers (ceramic, carbon, metal, and MXene fillers), analyze the effects of hydrogen bonding, electrostatic attraction, and chemical crosslinking on interfacial thermal resistance, and discuss 0D/1D/2D, gradient and multilayer ordered thermal-conduction pathway design for achieving high thermal conductivity. Future challenges and research directions are also proposed, providing guidance for the development of next-generation high-performance thermal management materials.
Ceramic-matrix composites face a persistent challenge: the trade-off between strength and toughness. Inspired by the mineral bridge architecture of nacre, we propose a reverse interphase design that contrasts with conventional dense-laminar pyrolytic carbon given the active incorporation of nanopores. Multiscale characterization and simulations reveal a dual reinforcement mechanism: nanopores reduce the interfacial debonding strength and induce crack deflection that protects fibers from brittle fracture. Meanwhile, the resulting rough fracture paths enhance interfacial frictional stress and load transfer, thereby improving the matrix bearing capacity and energy dissipation. This asymmetric modulation of interfacial properties simultaneously preserves fiber integrity and maximizes energy dissipation. The resulting single-tow Cf/SiC composites exhibit 903 MPa tensile strength, which is 38% higher than that of conventional designs, and a 1.8-fold increase in fracture energy. The interphase-enabled mechanisms identified here are intrinsically scalable, with their effectiveness further demonstrated in architectured ceramic-matrix composites. This work demonstrates a shift from empirical optimization toward theory-driven interface design and establishes a viable route to overcome the classical strength-toughness dilemma in structural composites.
This study reports the physicochemical characterization and structure-property relationships of rigid sheep wool/phenolic novolac panels developed as bio-based thermal insulation for building envelopes. Mixed Polish sheep wool was washed, mechanically opened, and formed into nonwoven mats, then impregnated with either neat or flame-retardant novolac resin to obtain lightweight boards with a fiber content of about 50 wt%. Elemental analysis, ICP-OES, FTIR spectroscopy, and laser and electron microscopy were used to evaluate the fiber composition, keratin structure, morphology, and fiber-matrix interfaces. Mechanical performance under three-point bending and shear, differential scanning calorimetry, thermogravimetric analysis, and transient hot-probe thermal-conductivity measurements were applied to link microstructure with functional behavior. Novolac impregnation transformed the compliant wool mat into self-supporting panels, increasing the flexural modulus to the 0.8-1.4 GPa range and flexural strength to approximately 48-52 MPa, while the shear modulus and work to failure rose by more than an order of magnitude relative to the loose wool reference. Thermal conductivity remained in a typical range for natural-fiber insulations (λ = 0.061 W·m-1·K-1 for the wool mat and 0.071-0.074 W·m-1·K-1 for the composites), although higher than that of expanded polystyrene. DSC and TGA confirmed that wool fibers remain thermally stable up to about 200-220 °C, that the novolac resin cures around 140 °C, with typical phenolic reaction enthalpies, and that both formulations generate high char residues of roughly 60-80 wt% at 600 °C under nitrogen, evidencing a strong charring propensity rather than directly quantifying fire resistance. Overall, the results position sheep wool/novolac panels between conventional bio-based insulation and structural composites and highlight their potential as sustainable, circular insulation materials for energy-efficient building envelopes.
High-entropy MAX phases (TiVNbTa)2AlC have attracted increasing attention due to their potential advantages in structural stability, damage tolerance, and mechanical reliability under complex service environments. This work studied the crystal and electrical structures with the elastic properties, the synthesis reactions and further wear resistance of HE-MAX (TiVNbTa)2AlC theoretically and experimentally. The charge transfer between both M-C atoms and M-Al atoms turned more intense, which correspondingly strengthened the M-C and M-Al bonds, respectively. Because of the dope on M-sites, (TiVNbTa)2AlC exhibited larger fracture toughness KIC and a lower brittle index M, which suggested lower brittleness, better crack extension resistance, and higher damage tolerance than Ti2AlC. In this work, high-entropy (TiVNbTa)2AlC MAX phase ceramics were successfully synthesized by a powder metallurgy route combined with pressureless sintering and spark plasma sintering (SPS). The effects of raw material composition and sintering temperature on phase evolution, microstructure formation, mechanical properties, and tribological behavior were systematically investigated. The results show that a highly pure (TiVNbTa)2AlC phase with a phase fraction of 96.8% could be obtained at a molar ratio of M:Al:C = 2:1.2:0.8 and a sintering temperature of 1550 °C. Phase evolution analysis indicated that the reaction process followed the sequence of intermetallic compound (IMC) formation → carbide formation → MAX phase formation. Severe lattice distortion induced by the multi-principal-element solid solution significantly enhanced the hardness of the material, which was markedly higher than that of conventional ternary MAX phases. Owing to its higher hardness and more homogeneous solid-solution structure, HE-MAX (TiVNbTa)2AlC could inhibit the formation of surface microcracks and reduce the driving force for crack propagation to some extent. Therefore, the lower wear rate not only reflected improved tribological performance but also demonstrated the beneficial role of high-entropy design in enhancing resistance to surface damage.
Electrospinning (ES) can produce nonwoven fibrous mats with high surface area and interconnected porosity, making them attractive for biomedical and functional material applications. However, conventional ES often relies on volatile organic solvents, raising safety, environmental, and translational concerns. Fully aqueous ("green") ES offers an appealing alternative, although many water-soluble polymers remain difficult to spin and may show limited stability under hydrated conditions. In this study, two fully aqueous binary systems, poly(vinylpyrrolidone)-sodium alginate (PVP-SA) and poly(vinylpyrrolidone)-riboflavin (PVP-RF), were investigated to decouple the roles of sodium alginate (SA) and riboflavin (RF) on solution behaviour, fibre formation, morphology, dry-state mechanical properties, and surface chemistry. Aqueous PVP solutions (20% w/v; molecular weight 1.3 MDa) were blended with SA (1-5 wt% relative to PVP) or RF (1-10 wt% relative to PVP). Electrical conductivity and rheological properties were evaluated prior to ES under controlled conditions, with simultaneous ultraviolet (UV) exposure at 344 nm during fibre collection. RF did not significantly alter conductivity (~0.74-0.75 µS·cm-1), whereas SA increased conductivity up to 2.75 ± 0.03 µS·cm-1 at 5 wt%. All formulations exhibited shear-thinning behaviour, while 10 wt% RF increased the zero-shear viscosity relative to neat PVP. Morphological analysis showed that low SA contents produced uniform fibres, whereas higher SA levels (4-5 wt%) led to bead defects and reduced fibre diameter (down to 85 ± 25 nm). Dry-state mechanical performance decreased with increasing SA content, while 10 wt% RF improved tensile strength and toughness, reaching an ultimate tensile strength of 5.21 ± 0.15 MPa and toughness of 40.51 ± 1.53 MJ·m-3. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated subtle UV-driven redistribution of surface chemical states, consistent with mild photo-oxidative microstructural modification rather than extensive covalent network formation. Because the UV irradiance was not directly measured and wet-state stability was not assessed, the UV-related findings are interpreted as preliminary chemical evidence rather than confirmation of stabilized fibre mats. Overall, this work establishes a solvent-free aqueous ES platform in which ionic and photoactive additives can be used to tailor fibre morphology, dry-state mechanical behaviour, and surface characteristics without toxic reagents.
Developing multielement doped Pb-free (K,Na)NbO₃ piezoelectrics often hindered by complex doping trends and tedious trial-and-error experimentation. Here, we present a human-in-the-loop, artificial intelligence guided materials design framework that utilizes large language models to capture implicit structure-property knowledge from prior literatures and propose new compositions. Expert intervention further directs experimental realization based on materials science principles and experiential knowledge, accelerating discovery of targeted compositions. Using collaborative strategy, synthesized random composition exhibiting piezoelectric charge constant d33 of 440 - 500 pC/N which further enhanced to 600-620 pC/N through crystallographic texturing and sintering aid optimization. Despite inherently off-MPB degradation (at R.T), this composition maintained steady electromechanical coupling (kij) and d31 up to 160 oC. To validate practical relevance, a cantilever-based magneto-mechano-electric (MME) energy harvester was fabricated, delivering a power density of ~ 705μW/cm3 at the second harmonic, outperforming reported Pb-free MME designs. Here, we demonstrate an exceptional approach towards developing application-specific functional materials through the synergy of AI-driven recommender systems, human expert validation, and experimental realization.
Dielectric capacitors offering ultrafast charge-discharge capability and superior reliability are essential for advanced electronic systems, but achieving both high energy density and efficiency within simple and eco-friendly compositions remains a great challenge. Here, guided by machine learning, we achieve high-efficiency and thermally stable capacitive energy storage in strontium titanate-based ceramics. Through synergistic local structural engineering and optimized fabrication process, the materials exhibit enhanced polarization, reduced hysteresis loss, and improved breakdown strength. The designed materials deliver an ultrahigh energy density of 10.69 J cm-3 with a near-ideal efficiency of ∼97% and a record high figure of merit of 392 J cm-3 at room temperature, and retains high performance at 150°C with a figure of merit of 152 J cm-3 and an efficiency of ∼94%. This remarkable performance arises from the incorporation of Bi3+ ions with high polarizability at the A-sites of strontium titanate quantum paraelectrics, which breaks structural symmetry and induces lattice and octahedral distortions, leading to the formation of nanoscale polar clusters with highly dynamic fluctuations. These findings establish a compositionally simple, environmentally benign pathway for developing dielectrics with superior energy storage capability and thermal stability, offering new opportunities for high-performance capacitive energy storage systems.
The deterministic integration of functional oxide thin films on technologically relevant substrates is a longstanding challenge for oxide electronics. Two-dimensional Ca2Nb3O10 nanosheets have emerged as versatile epitaxial templates, enabling high-quality film growth on arbitrary substrates by decoupling the overlying layer from the underlying support. However, the intrinsic gaps inherent in monolayer nanosheet assemblies originate from irregular geometry and stochastic deposition processes. These gaps create exposed substrate regions that introduce a second, distinct growth environment, whose influence on film properties remains poorly understood. Here, we demonstrate that these nanoscale gaps are not merely structural imperfections but rather tunable elements that govern the crystallinity, transport behavior, and magnetic anisotropy of SrRuO3 thin films. By engineering Ca2Nb3O10 nanosheets with controlled lateral size distributions (>20 μm and <2 μm) and systematically varying substrate coverage (≈90% and ≈95%), precise modulation of the crystallographic phase of gap-nucleated SrRuO3 is achieved. The phase varies from amorphous on SiO2 to polycrystalline on Si and Al2O3, and coexists with c-axis-oriented epitaxy templated by the nanosheets. This coexistence gives rise to emergent phenomena including nonuniaxial magnetic anisotropy, two-channel anomalous Hall signatures, and stepwise magnetization reversal, all of which are tunable through coverage and substrate selection. Bilayer nanosheet coatings effectively eliminate gap contributions, restoring pristine in-plane easy magnetization axis and confirming complete film-substrate decoupling. Our findings establish a previously unrecognized design paradigm in which the deliberate control of nanosheet gaps enables the engineering of composite magnetic and electronic ground states in oxide thin films, providing a scalable route toward multifunctional spintronic devices on arbitrary substrates.
Potassium sodium niobate (KNN) lead-free piezoelectric ceramics feature eco-friendliness and low density, coupled with superior high-frequency driving efficiency, albeit with inferior low-frequency performance. Conversely, Terfenol-D exhibits outstanding low-frequency driving capability but suffers from high density and poor high-frequency efficiency. This work proposes a ternary symmetric driving structure that integrates the complementary advantages of KNN and Terfenol-D, developing an underwater acoustic transducer with excellent lightweight design, low-frequency response, and broadband performance. The ternary symmetrically excited transducer maintains stable nodal planes across different operating frequencies and exhibits two distinct resonant frequencies. The vibration equation is analytically solved, and modal analysis is performed to clarify the evolution of the dual-resonance frequencies. A prototype transducer weighing 2.8 kg is fabricated and tested in an anechoic water tank. It delivers a maximum transmitting voltage response of 145 dB at 1.7 kHz with a broad operating bandwidth of 1-6 kHz. Compared with previously reported transducers, its weight is reduced by 26% to 93%. Benefiting from the double-ended radiation structure, the transducer yields a nearly omnidirectional radiation pattern. This ternary symmetrically excited transducer holds promising application prospects for underwater acoustic detection, communication, and navigation systems on unmanned underwater vehicle platforms.
ConspectusNegative thermal expansion (NTE) is a counterintuitive property in metamaterials that can be observed upon excitation of certain low-frequency vibrational modes. Conventional materials expand upon heating, showing positive thermal expansion (PTE), whereas NTE materials contract, which is unusual. NTE challenges conventional lattice-dynamical concepts and is of significant importance for a wide range of applications such as in composite material for dental filling, glass-ceramic cooktops, etc. Over the past three decades, major efforts have focused on discovering and tuning NTE compounds. NTE has been reported in a wide range of materials in bulk and low-dimensional systems. To date, the vast majority of experimentally and theoretically identified NTE materials belong to bulk crystalline systems, whereas discovery of two-dimensional (2D) NTE systems is limited. Nevertheless, this phenomenon is remarkably amplified due to reduced dimensionality, enhanced anharmonicity, and unconventional phonon dynamics. Quantum confinement alters electronic, optical, mechanical, and thermal properties significantly in these systems. They sustain large NTE over exceptionally wide temperature ranges, often attributed to rigid-unit modes (RUMs) in framework structures. NTE in 2D materials can arise from several mechanisms including flexural phonons, structural transition, anisotropic bonding, conformational changes, geometric flexibility, electronegativity differences, spin-crossover, etc. We demonstrate a comprehensive and mechanism-oriented overview of NTE in 2D materials, encompassing elemental monolayers such as in graphene and graphyne analogues, h-boron nitride, transition-metal dichalcogenides, metal phosphides, arsenides and other emerging 2D materials. Beyond intrinsic mechanisms, we discuss tunability strategies unique to atomically thin systems, including pore size modulation, heteroatom substitution, defect modification, and magnetic or electronic-state control. Recent studies link NTE in 2D materials to phonon transport and topology-driven lattice responses and reveal trade-offs between thermal expansion and lattice thermal conductivity (TC). Most low-TC 2D systems exhibit pronounced NTE and vice versa. Spontaneous symmetry breaking in 2D-materials is associated with pseudo Jahn-Teller (PJT) distortions. The machine-learning (ML)-based predictions highlight the strong structural dependence of NTE in 2D materials. Despite growing interest in NTE materials across diverse applications, rational structural design and controlled tuning of lattice expansion remain challenging. This Account assesses current limitations and outlines future directions based on high-throughput calculations, ML, and topology-guided design for realizing enhanced NTE in 2D systems.
Background and Objectives: Professional ballet dancers endure high occlusal loads, increasing cervical defect prevalence. Conventional composites fail frequently under such conditions. This randomized clinical trial (RCT) compared 24-month performance of a polymer-infiltrated ceramic network (PICN, VITA Enamic) versus a self-curing bioactive composite (Stela) for cervical restorations. Materials and Methods: Twenty professional ballet dancers (40 cervical defects: 21 carious, 19 abfraction) were enrolled in a paired split-mouth RCT. Each received one PICN inlay and one self-curing composite restoration on two non-adjacent defects. Restorations were assessed at 6, 12, and 24 months using United States Public Health Service (USPHS) criteria (primary: marginal integrity) and a dye penetration test. Secondary outcomes included secondary caries, hypersensitivity, and Oral Health Impact Profile-14 (OHIP-14). Statistical tests: McNemar, Fisher's exact, Kaplan-Meier, log-rank (α = 0.05). Results: At 24 months, marginal integrity (USPHS Alpha) was maintained in 91% of PICN restorations for carious defects and 89% for abfraction defects, compared to 70% and 50% for self-curing composite, respectively. No PICN restoration failed (0%). Self-curing composite failures were 20% (carious) and 30% (abfraction) (exploratory uncorrected p = 0.031; non-significant after correction). Dye penetration was lower for PICN in abfraction defects (11% vs. 60%, adjusted p = 0.048) but not in carious defects (9% vs. 30%, adjusted p = 0.317). Kaplan-Meier survival favoured PICN (log-rank p = 0.001); 24-month survival probability: PICN 100% (95% CI: 83-100%), self-curing composite 75% (95% CI: 55-95%). No secondary caries or serious adverse events occurred. Conclusions: PICN hybrid ceramic provided superior marginal integrity and zero failures over 24 months in cervical restorations of professional ballet dancers, outperforming the self curing composite. Within this high-risk population, PICN inlays are recommended for abfraction defects. However, because the study was conducted exclusively in professional ballet dancers, direct extrapolation to the general population should be made with caution. The self-curing composite may be considered for carious defects when light curing is problematic, but patients should be informed of higher failure risk. Longer studies are needed.
This study evaluated the effects of different printing orientations on the mechanical properties and surface roughness of a 3D-printed definitive resin-based composite (RBC) material. Bar shaped samples were fabricated from a 3D-printed RBC (VarseoSmile TriniQ) using three different build orientations (0°, 45°, and 90°) and lithium disilicate ceramic (IPS e.max CAD). Flexural strength and elastic modulus were evaluated using a three point bending test. Surface microhardness was assessed with a Vickers hardness test, and surface roughness was measured using a contact profilometer. Following mechanical testing, the sample surfaces and fractured regions were further examined by scanning electron microscopy (SEM) for topographic and fractographic evaluation. Statistical analysis was performed at α = 0.05 using one way ANOVA, with post hoc comparisons conducted using the Tamhane test. Significant differences were observed among the tested materials for all evaluated parameters (p < 0.001). IPS group demonstrated superior mechanical properties and lower surface roughness compared to the 3D-printed RBCs. Within the 3D-printed groups, the 0° build orientation exhibited higher flexural strength, whereas the 90° orientation showed increased surface hardness. Elastic modulus and surface roughness were not significantly influenced by printing orientation (p > 0.05). SEM analyses supported the quantitative findings by revealing a homogeneous and compact microstructure in IPS group and orientation-dependent surface and fracture features in the 3D-printed RBC groups. IPS e.max CAD demonstrated superior mechanical performance. The 0° orientation improved flexural strength, while the 90° orientation enhanced surface hardness, suggesting that build orientation should be selected according to the intended clinical function.