Problematic fine-grained soils exhibit low strength and inadequate durability, highlighting the need for sustainable stabilization using eco-friendly binders. This study examined the strength development and durability of a natural CH soil (NSs) stabilized with fly ash (FA) based geopolymer exposed to sulfate attack and freeze–thaw (F–T) cycles. The effects of FA content (0–40%) and NaOH molarity (0–10 M) on unconfined compressive strength (UCS) were evaluated after 1, 7, 28 and 56 days of curing. Durability was assessed separately under accelerated laboratory conditions after 1, 3, 5, 7 and 11 F–T cycles and 7, 28 and 56 days of sulfate exposure. In non-activated specimens, FA contents of up to 30% enhanced the UCS primarily through the microfiller effect and possible time-dependent pozzolanic reactions. Alkali activation promoted the development of a compact binding matrix through the dissolution and polycondensation of aluminosilicate precursors, with the microstructural and chemical observations being consistent with the possible formation of C-(A)-S-H and/or N-A-S-H-type reaction products. F30M8 exhibited the highest strength, reaching a 56-day UCS of 1488.58 kPa compared with 282.46 kPa for untreated NSs. F30M8 retained approximately 94% of its UCS after 11 F–T cycles and 92% after 56 days of sulfate exposure. XRD, FTIR, and SEM-EDX analyses provided evidence of aluminosilicate restructuring and the development of a dense microstructure under alkaline activation. This refined matrix may have contributed to limiting sulfate- and ice-crystal-induced deterioration, thereby helping to preserve the structural integrity of the FA-based geopolymer-stabilized NS specimens, whereas untreated and non-activated FA-stabilized specimens disintegrated under sulfate exposure. These findings indicate that FA-based geopolymer stabilization has considerable potential for natural CH soil under the laboratory exposure conditions investigated in this study.
The hot deformation behavior and microstructure evolution of a novel near-α Ti65 titanium alloy with an initial lamellar microstructure were investigated by isothermal compression. Compression tests were conducted at 950–1010 °C in the α + β phase region and 1050–1110 °C in the β phase region, with strain rates of 0.01–10 s−1 and deformation amounts of 30–75%. The flow behavior, strain-compensated Arrhenius constitutive model, processing map and microstructural evolution were systematically analyzed. The results indicate that the flow stress decreases with increasing temperature and decreasing strain rate, while flow softening is more pronounced in the α + β region than in the β region. The apparent activation energies are 1050.27 kJ/mol for the α + β region and 203.51 kJ/mol for the β region, indicating distinct deformation mechanisms. The established constitutive models exhibit high prediction accuracy, with R and AARE values of 0.98 and 5.97% in the α + β region and 0.99 and 4.29% in the β region, respectively. Processing-map analysis identifies two instability domains at high strain rates: 990–1020 °C/3.5–10 s−1 in the upper α + β region and 1060–1110 °C/1.65–10 s−1 in the β region. Microstructural observations reveal that dynamic spheroidization of lamellar α dominates deformation in the α + β region, whereas dynamic recovery accompanied by limited β dynamic recrystallization occurs in the β region. Increasing deformation amount at 980 °C and 0.01 s−1 promotes α-lamella fragmentation, spheroidization, grain refinement and texture weakening. The maximum pole density decreases to 6.23 mrd at a high deformation amount. By directly correlating strain-dependent processing-map characteristics with quantitative microstructural and crystallographic evolution, this work provides a microstructure-based basis for optimizing the hot-working window of Ti65 alloy with an initial lamellar microstructure.
Coral aggregate seawater concrete (CASC) capitalizes on locally sourced aggregates in marine and reef engineering, enabling in situ material utilization and conferring marked benefits in curbing conventional resource consumption and construction expenditures—a combination that underpins its considerable promise for reef infrastructure development. To date, research efforts have largely been confined to macroscopic mechanical characterization and qualitative microstructural inspections, and quantitative assessments of mesoscopic damage evolution across the full loading-to-failure process remain relatively scarce. In response, to quantitatively characterize the mesoscopic damage evolution mechanism of CASC with different natural aggregates, the present study draws upon statistical damage theory and incorporates uniaxial compressive stress–strain responses from CASC mixtures formulated with four replacement ratios (0%, 33%, 67%, and 100%) of natural coarse and fine aggregates, thereby establishing a statistical damage constitutive model. The model is intentionally structured to decipher the intricate interplay that translates progressive mesoscopic deterioration into the eventual macroscopic mechanical signature, rather than merely describing phenomenological curves. The outcomes reveal favorable concordance between model-generated predictions and experimental measurements. Introducing natural aggregates appreciably modulates the cumulative damage trajectory at the mesoscale; with rising replacement ratios, the macroscopic mechanical performance of CASC is systematically fortified, concomitant with orderly shifts in characteristic damage indices (εa, εb, εh and H). Specifically, when the replacement ratio of natural fine aggregate is fixed at 0%, as the replacement ratio of natural coarse aggregate increases from 0% to 100%, the values of εa, εb, εh, and H increase by 35.8%, 36.9%, 32.2%, and 66.5%, respectively. Additionally, both the fracture damage variable DR and the integrated transverse strain area derived from digital image correlation (DIC) exhibit monotonic ascending trends as loading advances. Collectively, these contributions offer a theoretical foundation for performance optimization and a deeper mechanistic understanding of damage behavior in CASC.
The durability of prestressed spun-cast concrete poles is typically assessed on the basis of the nominal mix design parameters and the assumption of material homogeneity. However, the centrifugal spinning of fresh concrete mix results in an uneven distribution of its components throughout the wall thickness, which may affect the actual cement content in individual layers and consequently, the durability. As part of this study, the distribution of cement content in spun concrete poles was analysed using an experimental approach based on the analysis of hardened concrete composition. Samples were taken from various locations along the height of the pole and divided into layers across wall thickness. Cement content, aggregate distribution, porosity, and water absorption were determined using a combination of chemical and physical methods. The results indicate that although the average cement content meets the design requirements (minimum amount of cement exceeds 300 kg/m3), there are significant local variations, particularly in the inner and outer layers of the cross section. The inner layer is characterized by increased cement content and porosity, while the outer layer is characterized by a higher coarse aggregate content and reduced cement content. It was also observed that the spinning program used in the production of the poles resulted in a homogeneous concrete structure at the top of the pole, where the spinning radius is smallest, with no signs of delamination. However, delamination of the concrete structure was observed at lower sections of the pole. These results highlight the limitations of assuming homogeneous material properties in durability design and suggest that the actual performance of spun concrete elements may deviate from predictions based on the standards. The results have direct implications for assessing the durability of spun concrete poles used in exposure classes such as XC4 and XD1.
Titanium and its alloys are widely used in cardiovascular devices because of their favorable mechanical properties, corrosion resistance, and biocompatibility. Nevertheless, their surfaces do not fully prevent nonspecific protein adsorption, platelet activation, thrombosis, bacterial colonization, or long-term degradation under physiological conditions. Silicon-nitride-based (SiNx) coatings represent a promising strategy for addressing these limitations by combining chemical stability, mechanical durability, hemocompatibility, and antibacterial activity. This review critically examines silicon-nitride-based (SiNx) coatings on titanium for cardiovascular applications, focusing on deposition technologies, interfacial phenomena, surface characteristics, and biological performance. Particular attention is given to physical vapor deposition parameters, coating adhesion, residual stresses, interfacial reactions, corrosion resistance, and mechanical stability. Relationships between surface chemistry, wettability, protein adsorption, platelet response, hemolysis, and cellular behavior are discussed, alongside the effects of static and dynamic testing conditions. SiNx is also compared with Au, TiN, TiO2, ZrN, and silicon carbide-based coatings. Despite encouraging in vitro results, clinical translation remains limited by insufficient standardization, scarce long-term and flow-dependent data, and an incomplete understanding of degradation mechanisms. Future studies should integrate interface engineering with microfluidic models, standardized hemocompatibility testing, artificial intelligence-assisted optimization of process–structure–property–biological response relationships, and regulatory considerations to support the safe clinical translation of SiNx-coated cardiovascular devices.
Bio-inspired helicoidal laminates can redirect damage under transverse loading, but their response as sandwich face sheets remains unclear because the core changes both deformation and load transfer. This study experimentally and numerically investigated the quasi-static penetration of 73-ply carbon/epoxy laminates and Nomex honeycomb sandwich panels with cross-ply, quasi-isotropic, uniform helicoidal (5°, 10°, and 20°), and hybrid helicoidal layups. A fully ply-resolved model was developed for the monolithic laminates, whereas an eight-sublaminate model with an explicitly represented honeycomb core was used for the sandwich panels. H73(10–5) achieved the highest monolithic-laminate peak load of 5.23 kN, 46.1% above CP73 and 35.5% above QI73. The sandwich panels exhibited two load peaks separated by a core-crushing plateau. S-H73(5–10) produced the highest first peak load of 8.99 kN, while S-H73(10–5) achieved the highest penetration energy of 108.37 J. Experiments, simulations, and fractographic observations showed that the intact core constrained upper-face-sheet bending and promoted localized indentation-assisted punching-shear perforation. The crushed core subsequently transferred load to the lower face sheet, which failed through bending- and membrane-dominated tearing.
This study employs molecular dynamics simulations to construct a CSH/SiO2 nanochannel model, systematically investigating the dynamic transport behavior of pure water and Na2SO4 solution within the pores across temperatures ranging from 293 K to 368 K. The results elucidate the fluid intrusion mechanism under the combined effects of elevated temperature and sulfate ions. Results show that: (i) Water migration within the CSH/SiO2 channel exhibits wall-dependent differences. The interaction between water and the CSH surface is approximately eight times stronger than with the SiO2 side at 293 K, causing water molecules to preferentially advance along the CSH side. As the penetration depth difference between the two sides increases, local water molecules extend toward the SiO2 side, forming liquid finger-like protrusions that lead to rapid filling on the SiO2 side. (ii) Elevated temperature enhances water molecule mobility; at 368 K, the mean square displacement of water in the pure water system is about 3.7 times greater than at 293 K, and the critical time for liquid finger formation on the SiO2 side decreases from 700 ps at 293 K to 100 ps at 368 K. (iii) The introduction of Na2SO4 solution alters the transport mechanism within the nanochannel. Na+ and SO42− form ionic coordination structures with oxygen and calcium sites on the CSH surface, establishing Na-OCSH and S-CaCSH ionic bonds, which reduces the solution’s transport rate. Na+ and SO42− adsorb and accumulate near the CSH/SiO2 interface; heating weakens their hydration shells and strengthens the ion association between Na+ and SO42−, promoting the formation of local ion clusters.
Fluorine in phosphogypsum (PG) poses a persistent leaching risk, and PG-based cemented paste backfill (CPB) offers a practical option for in situ stabilization. In this study, fluorine transformation from phosphate rock (PR) to PG and further to CPB was quantified using acid dissolution for total fluorine (TF) determination and sequential extraction for fluorine speciation. Pearson correlation analysis was used to examine statistical relationships among fluorine fractions. TF decreased progressively during wet-process phosphoric acid production, PG stockpiling, and CPB preparation. However, the proportion of mobile fluorine increased from PR to CPB, indicating incomplete reversal of process-induced fluorine activation. CPB immobilized most mobile fractions, increasing the residual fraction to 88.83–97.17% of TF and achieving fluorine transfer efficiencies of 93.59–94.75%. Speciation results showed marked decreases in water-soluble fluorine (Ws-F) and exchangeable fluorine (Ex-F) in CPB, while Pearson correlation analysis further suggested strong statistical associations among Ws-F, Ex-F, and other fractions, suggesting potential interconversion pathways under alkaline, Ca-rich CPB conditions. Nevertheless, a Ws-F-dominated mobile fraction remained in CPB, accounting for 2.83–11.19% of TF, and governed the long-term leaching risk. Therefore, assessing CPB based on process-oriented fluorine speciation, rather than merely on TF content, is critical for optimizing PG-based CPB formulations and achieving the safe reutilization of PG.
Quantitative determination of gangue content is important for efficient coal use and intelligent coal–gangue separation. We combine transmission terahertz time-domain spectroscopy (THz-TDS), multidomain feature fusion, and machine learning to predict gangue mass fraction in coal–gangue mixtures. Time- and frequency-domain signals, refractive index, absorption and extinction coefficients, and complex permittivity were extracted from samples with different gangue contents. Five-fold cross-validation was used to compare random forest, support vector regression, Gaussian process regression, an artificial neural network, and an Effective Medium Theory-constrained Physics-Informed Neural Network (EMT-PINN). EMT-PINN achieved the best performance, with a coefficient of determination (R2) of 0.81 ± 0.15, a mean absolute error (MAE) 3.17 ± 0.59%, and a root mean square error (RMSE) of 5.79 ± 0.21%, compared with R2 values of 0.72 ± 0.08, 0.61 ± 0.21, 0.74 ± 0.11, and 0.64 ± 0.18 for RF, SVR, GPR, and ANN, respectively. These results demonstrate the potential of physics-informed THz spectroscopy for rapid and physically interpretable quantitative characterization of coal–gangue mixtures.
The development of straightforward and efficient strategies for the preparation of polymer-functionalized mesoporous silica remains an important challenge in the design of advanced hybrid materials. Herein, we report a novel and simplified approach to the covalent functionalization of mesoporous silica particles (MSP) with poly(2-ethyl-2-oxazoline) (PEtOx), based on the direct termination of living cationic polymer chains by amino groups immobilized on the silica surface. In contrast to conventional grafting-to methods, the proposed strategy eliminates the need for polymer end-group functionalization while avoiding the synthetic complexity associated with surface-initiated polymerization. Well-defined PEtOx chains with number-average molar masses of 5000 and 7500 g mol−1 were synthesized by cationic ring-opening polymerization (CROP) and subsequently grafted onto amino-functionalized MSP. Successful covalent immobilization of the polymer was confirmed by Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), contact angle measurements, and nitrogen adsorption–desorption studies. The modification preserved the ordered mesoporous architecture while increasing particle hydrophilicity and decreasing the specific surface area and pore volume due to polymer incorporation. Shorter polymer chains exhibited higher grafting efficiency than higher-molar-mass analog, indicating that steric hindrance is an important factor influencing the grafting process. The presented methodology provides a versatile and experimentally accessible platform for the preparation of well-defined poly(2-oxazoline)-functionalized mesoporous silica with tunable physicochemical properties. Owing to the combination of a porous inorganic framework and a polymer shell, the obtained hybrid materials represent promising candidates for drug delivery, adsorption technologies, and other advanced biomedical and environmental applications.
(1) Background: Repairing fractured provisional restorations may avoid refabrication, but success depends on substrate chemistry, repair protocol, and aging. This study evaluated shear bond strength (SBS) and failure behavior after chairside repair of PEMA-, PMMA-, and bis-acryl-based provisional materials. (2) Methods: In total, 380 specimens were prepared. Repairs used the substrate material, a dedicated repair system, or flowable composite without pretreatment or after a methacrylate repair primer, an MMA/Bis-GMA primer, or a multifunctional methacrylate coating. Half underwent 5000 thermocycles (5–55 °C). SBS was determined using a notched-edge test based on ISO 29022:2013, and failure modes were evaluated. An HC3-robust three-factor model was followed by Holm-adjusted Welch comparisons. (3) Results: A material × protocol × aging interaction occurred (p < 0.001). Homologous repair yielded 17.88–20.35 MPa for PEMA and 25.09–25.30 MPa for PMMA. Pretreatment improved composite repair across substrates. Pre-test failures affected 40.0% of PEMA and 13.3% of PMMA specimens but no bis-acryl specimens. Unprimed flowable composite produced complete pre-test failure with PEMA, low SBS with PMMA, and moderate SBS with bis-acryl. Thermocycling effects were protocol-dependent. (4) Conclusions: Conventional acrylics should be repaired homologously or after chemical conditioning, whereas flowable composite alone may be suitable for minor, non-load-bearing bis-acryl corrections.
To investigate freeze–thaw damage evolution and mix proportion effects in PVA fiber–fly ash–slag powder composite concrete (PVA-FA-SPC), nine composite concrete mixtures were designed using an L9(33) orthogonal array at a water to binder ratio of 0.45, with plain concrete serving as the reference, and subjected to 200 rapid freeze–thaw cycles. Freeze–thaw resistance was evaluated using surface deterioration, the mass loss rate, and the relative dynamic elastic modulus. Within the investigated factor levels, PVA fiber volume content exhibited the strongest main effect trend, followed by the total mineral admixture replacement rate and the fly ash to slag powder mass ratio. T20R1:2P0.3, containing 20% total mineral admixture replacement, a fly ash to slag powder mass ratio of 1:2, and 0.3% PVA fiber, showed the best measured performance, retaining a relative dynamic elastic modulus of 79.18% after 200 cycles. A two-parameter Weibull function was used as a phenomenological description of the damage evolution; compared with the classical exponential model, the average RMSE decreased from 0.032 to 0.019 and the average MAPE decreased from 5.07% to 2.98%. Because only nine independent orthogonal mixtures were available for parameter mapping, a common shape parameter of α0 = 2.1403 was adopted, and a parsimonious equation for the scale parameter β was selected using the small-sample-corrected Akaike Information Criterion (AICc) together with leave-one-mixture-out cross-validation (LOMO-CV). LOMO-CV yielded R2 = 0.886, RMSE = 0.034, MAE = 0.025, and WMAPE = 19.98%; however, T20R1:2P0.3 exhibited a node WMAPE of 72.75%, indicating a local limitation of the reduced order mapping. Three non-orthogonal mixtures within the same material system yielded R2 = 0.943, RMSE = 0.026, and WMAPE = 15.36%. The proposed model is therefore intended for local trend analysis and preliminary mix screening within the calibrated material system and parameter range rather than for universal service life prediction.
The Bi/Bi2O3-type oxygen sensor is extensively employed for oxygen monitoring in liquid lead-bismuth eutectic (LBE)-cooled reactors, yet its low-temperature measurement accuracy remains a critical bottleneck limiting engineering deployment. This study aims to extend the lower operating temperature limit of the sensor through synergistic optimization of the reference electrode and solid electrolyte. The effects of the Bi/Bi2O3 mass ratio, filling amount, and yttria-partially stabilized zirconia (YPSZ) electrolyte wall thickness on sensor performance were systematically investigated over 300–600 °C. Electrochemical impedance spectroscopy and finite element simulations (COMSOL Multiphysics® 6.3, COMSOL Inc., Stockholm, Sweden) were used to elucidate the underlying mechanisms. The results show that the optimized sensor with a Bi/Bi2O3 mass ratio of 95:5, a filling amount of 10 g, and a YPSZ wall thickness of 1.5 mm extended the stable operating limit from 350 °C to 300 °C, achieving a relative electromotive force error of 3.13% at 300 °C and maintaining over 4000 h of drift-free service. The improved low-temperature accuracy is attributed to the reduced oxygen ion migration activation energy (0.48 eV) and lower bulk impedance of the thick-walled YPSZ after high-temperature activation. These findings provide a material optimization strategy and theoretical basis for wide-temperature-range, long-lifetime oxygen sensing in lead-based reactors.
This study examines how mechanically activated fly ash (TF), a polycarboxylate superplasticizer (PC), and an air-entraining admixture (AE) affect the hydration, microstructure, pore structure, mechanical properties, and freeze–thaw resistance of fine-grained concrete. Mechanical activation increased the specific surface area of the untreated ash (UF) from 3710 to 6450 cm2/g and reduced its mean particle size to 6.06 μm. Replacing 5 wt.% of cement with TF accelerated the nucleation of hydration products and densified the microstructure, as confirmed by exothermic profiling, XRD, and SEM. PC delayed the exothermic peak yet produced the highest heat-release intensity, indicating more efficient wetting and dispersion of reactive surfaces. The TF–PC system reached 39.3 MPa at 28 days, while the ternary TF–PC–AE composition achieved 33.2 MPa with a refined pore-size distribution (mercury intrusion porosimetry). The combined use of PC and AE tripled the pore volume in the 0.01–0.10 μm range and increased it by 28.7% (0.1–1 μm) and 46.21% (1.0–10 μm). The calculated potential freeze–thaw resistance rose from 54.25 to 61.97 and 72.83, confirming the beneficial role of 3–10 μm pores. After 110 accelerated freeze–thaw cycles, the optimized ternary composition lost only 0.55% of its mass.
Reliable in-situ defect classification is essential for ensuring the mechanical performance of parts produced by material extrusion. However, machine learning and deep learning models often suffer from poor generalization because training datasets typically consist of many correlated signal segments generated from only a limited number of independent print jobs. To address this problem, we analyze how job-specific characteristics are distributed across signal components and find that they are concentrated primarily in the signal level rather than in the residual component. Motivated by this observation, we propose Level-Aware Residual Mixup(LARM), a data augmentation method that separately interpolates the level and residual components of sensor signals. LARM preserves realistic job-level characteristics by restricting level interpolation to values observed in real print jobs while allowing flexible mixing of residual components within the same defect class. We evaluate LARM against representative augmentation methods across diverse classification models under a realistic job-level leave-one-group-out cross-validation protocol. Experimental results demonstrate that LARM achieves better generalization than both training without augmentation and representative augmentation methods.
This study evaluated the effects of the methyl methacrylate (MMA)-containing adhesive primer Visio.link on the surface characteristics of sandblasted poly(ether ether ketone) (PEEK) and its bond strength to four dental resin cements: the MMA-based resin cement Super-Bond EX (SB) and the composite-based resin cements RelyX Universal Resin Cement (RX), G-CEM LinkForce (GC), and Panavia V5 (PA). Sandblasted PEEK specimens were tested with or without primer application. Surface morphology, surface roughness, and surface free energy were evaluated, and shear bond strength (SBS) was measured after 1 day of water storage and after 20,000 thermal cycles. Primer application smoothed the sandblasted surface, reduced surface roughness, increased the polar component, and decreased the dispersive component and total surface free energy. Primer application significantly increased the initial SBS of RX, GC, and PA; however, thermal aging reduced bonding durability and caused pretest debonding in several groups. For SB, primer application did not significantly affect the initial SBS, whereas the sandblasted group showed significantly higher SBS than the primer-treated group after aging. The effect of the MMA-containing primer therefore depended on resin cement type and aging condition. These findings suggest that primer application should be considered according to the composition and bonding mechanism of the resin cement rather than routinely incorporated into PEEK bonding procedures.
The development of more sustainable asphalt materials requires modified bitumen binders that combine thermal resistance, adhesion, and deformation capacity. In this study, soft paving-grade bitumen was modified with styrene–butadiene–styrene polymer, oil refinery sludge, titanium slag, and lead-furnace cyclone dust. Binders with bitumen-to-modifying-system ratios from 90:10 to 60:40 were characterized by FTIR, TGA/DSC, XRD, and portable XRF analyses and evaluated using penetration-type consistency, softening-point, qualitative adhesion, and tensile deformation tests. The modifying-system content produced non-monotonic changes in binder properties. Among the investigated formulations, the 75:25 composition provided the most balanced response, with a penetration depth of 8.6 mm, a softening point of 65.0 °C, a maximum elongation of 355.66 mm, and high qualitative film retention on mineral aggregate. In contrast, the 60:40 binder showed increased penetration and the lowest elongation, indicating that excessive modifier loading was unfavorable. The 75:25 binder was subsequently used in small-scale asphalt concrete sections and showed acceptable preliminary behavior during mixture preparation, placement, and compaction. The results demonstrate composition-dependent relationships in the investigated multicomponent system and support further evaluation of selected industrial by-products in modified bitumen binders.
The main objective of this systematic review was to synthesise current knowledge on tricalcium phosphate (TCP) as a functional modifier of poly(methyl methacrylate) (PMMA)-based bone cements, relating the microstructure of PMMA/TCP composites to their mechanical, biological and functional (handling) performance. Web of Science, Scopus and PubMed were searched for 2010–2025. Studies reporting primary quantitative data on PMMA cements specifically modified with TCP were eligible. Over one hundred records were screened by two independent reviewers, yielding 15 studies appraised qualitatively and combined by narrative synthesis. The evidence links polymerisation of the PMMA matrix, calcium and phosphate ion release from TCP, apatite-layer precipitation, and cell-mediated TCP resorption coupled to bone remodelling. TCP, especially β-TCP or biphasic calcium phosphate systems, can balance mechanical stability with bioactivity: moderate β-TCP contents (of the order of 10 wt% for solid cements under quasi-static compression) preserve clinically acceptable properties while enhancing osteoconductivity, though this limit falls for porous, α-TCP-containing and fatigue-loaded formulations. Porosity, TCP amount, crystalline form and particle size are the governing microstructural variables. The evidence is limited, dominated by in vitro and short-term static tests, with heterogeneous formulations and no controlled clinical data, so benefits should be interpreted qualitatively rather than as firm quantitative relationships. The review was not registered; this research received no external funding.
Chrome-containing corundum–spinel castables are the preferred materials for ladle purging plugs due to their excellent slag resistance, high mechanical strength, and good volume stability. However, their poor thermal shock resistance often leads to transverse cracking or thermal spalling, thereby limiting their service life improvement. Since aggregates typically constitute 70 wt% of castables, modifying the aggregates may be an effective strategy to enhance the thermal shock resistance. To this end, alumina spherical aggregates were prepared via a pan granulation technique using α-Al2O3 powders as the raw material and a ZnCl2 solution as the binder. The effects of the firing temperature on the physical properties and the microstructure of the as-fabricated aggregates were investigated, followed by an evaluation of their impact on castable performance. After firing at 1400 °C for 3 h, the resulting alumina spherical aggregates exhibited a porous interior and a dense exterior structure, with an apparent porosity of 27.21%, a water absorption capacity of 9.38%, and a crushing rate of 51.3%. When these aggregates were incorporated into castables, their apparent porosity increased, while the bulk density and the cold strength showed slight reductions; however, their thermal shock resistance was notably improved. Among the formulations tested, the castable containing 4% of 0.2–0 mm spherical aggregates exhibited the best thermal shock resistance, with a residual strength of 7.96 MPa and a strength retention rate of 27.85%.
Background/Objectives: Rice husk silica (RHS) is a biosustainable filler with potential application in dental flowable composites (FCs). However, early post-polymerisation colour change in RHS-incorporated FCs may vary with material formulation, particularly resin composition and photoinitiator system, and may also be affected by the colour-assessment device used. This study compared the 24 h post-polymerisation colour change of 10 experimental RHS-incorporated FC groups formulated with five photoinitiator systems and two commercial FCs used as control, using three colour-assessment devices. Methods: Two UDMA/TEGDMA formulations (U50 and U40), each containing 50 wt% nanohybrid RHS, were prepared with different photoinitiator systems (CQ, PPD, CQ/PPD, BAPO, or TPO). CIELAB coordinates were recorded immediately after curing and after 24 h of dry, dark storage at 37 °C using D1 (VITA Easyshade), D2 (Ds-700d Portable Spectrophotometer), and D3 (ColorMeter Pro). The same specimens were measured with all three devices, with five matched specimens from each of the 12 composite groups (N = 60). A mixed repeated-measures ANOVA was performed with device as the within-subject factor and composite as the between-subject factor; agreement was additionally assessed using Bland–Altman analysis and an absolute-agreement intraclass correlation coefficient (ICC). Results: Device, composite, and the device × composite interaction were significant (all p < 0.001). Estimated mean ΔE*ab was highest for D1 (5.019), followed by D3 (2.368) and D2 (1.777), and all device pairs differed significantly after Bonferroni adjustment. Bland–Altman analysis showed systematic positive bias for D1 relative to D2 and D3. The absolute-agreement ICC was 0.130 (95% CI 0.078–0.177), indicating poor agreement. Conclusions: The magnitude of early 24 h colour change depended on both the composite material and the measurement device. The three devices should not be assumed to be directly interchangeable for ΔE*ab assessment; the same calibrated device should be used throughout a longitudinal comparison.
