This in vitro study compared CO2 laser surface-conditioning protocols with airborne-particle abrasion in zirconia repaired using two complete repair systems. Eighty zirconia specimens were allocated according to repair system and surface-conditioning protocol. Conditioning consisted of airborne-particle abrasion with 50-& micro;m Al2O3 or CO2 laser scanning protocols comprising 1, 2, or 3 passes with different scanning directions. Color measurements were obtained before and after 6000 thermocycles, and specimen-level color differences (Delta E*ab) were calculated using the CIELAB formula. Nominal shear bond strength (SBS) was evaluated using a universal testing machine, and surface morphology was qualitatively examined by SEM. Data were analyzed using factorial methods with multiplicity-adjusted comparisons (alpha = .05). Two-way ANOVA demonstrated significant differences in SBS according to repair systems and surface-conditioning protocols (p=.018). The highest SBS was observed in the airborne-particle abrasion group repaired with feldspathic glass-ceramic. Within this repair system, the 3-pass laser protocol showed significantly higher SBS than the 1-and 2-pass protocols (p<.05), whereas differences among laser-treated composite resin groups were not significant (p>.05). Composite resin repair-system groups demonstrated greater color change after thermocycling than feldspathic glass-ceramic groups. SEM revealed qualitative differences in surface morphology among protocols. Under the tested conditions, airborne-particle abrasion produced the highest SBS values. The laser groups represent distinct scanning protocols rather than an isolated test of repetition alone. Differences between repair approaches should be interpreted at the repair-system level because adhesive chemistry and resin-layer configuration differed. All Delta E*ab values exceeded the perceptibility threshold of 1.2, while composite repair-system means exceeded the acceptability threshold of 2.7.
The development of multifunctional protective coatings capable of withstanding both aggressive corrosive environments and elevated temperatures remains a significant challenge in industrial applications. In this study, a novel LiMn1.5Ni0.25Co0.20Cu0.05O4 mixed-metal oxide nanopowder was synthesized via a controlled sol-gel/co-precipitation route and investigated as a heat-resistant and anticorrosive pigment for steel protection. The prepared nanopigment exhibited nanosized particles ranging from 15 to 50 nm with high fineness (7H), excellent thermal stability, negligible moisture content, and outstanding resistance to solvent bleeding, confirming its suitability for coating applications. The synthesized nanopowder was incorporated into a silicone-based coating system and compared with a commercial coating formulation (F1) and a zinc phosphate-containing formulation (F2). Structural characterization by XRD confirmed the formation of a stable crystalline spinel phase, while microscopic examination revealed a homogeneous particle distribution with limited agglomeration. Mechanical evaluation demonstrated significant improvements in coating hardness, adhesion strength, impact resistance, and chemical durability without compromising flexibility. Heat-resistance testing revealed remarkable thermal stability of the coating containing LiMn1.5Ni0.25Co0.20Cu0.05O4 nanopigment (F3), which maintained excellent film integrity up to 700 degrees C, whereas commercial formulations exhibited cracking and severe degradation at considerably lower temperatures. Furthermore, immersion testing in 3.5 wt.% NaCl solution showed superior corrosion protection, with negligible blistering, absence of rust formation, and minimal corrosion creep after 28 days of exposure. The enhanced performance is attributed to the synergistic effects of the mixed transition-metal oxides, nanoscale particle size, high barrier properties, and strong pigment-binder interactions that collectively improve coating compactness and resistance to heat and corrosive species. This work demonstrates, for the first time, the successful utilization of LiMn1.5Ni0.25Co0.20Cu0.05O4 nanopowder as a multifunctional protective pigment that simultaneously enhances thermal resistance, mechanical durability, and corrosion protection. The developed coating system offers a promising environmentally friendly alternative for high-performance protective coatings intended for aerospace, energy, marine, and industrial applications.
Epoxy molding compounds (EMCs) play a critical role in determining warpage and interfacial delamination in fan-out wafer-level packaging (FOWLP). In this study, we propose an integrated simulation framework that links the thermomechanical properties of EMCs to package-level warpage and local crack-tip responses during the FOWLP process. Representative volume element (RVE) models with silica filler volume fractions ranging from 30 to 70 vol% are used to evaluate the temperature-dependent elastic modulus and coefficient of thermal expansion (CTE) of EMCs. Both elastic and viscoelastic models are considered for the epoxy matrix. The RVE-predicted properties are subsequently incorporated into a process-level finite element model and localized sub-models to investigate warpage and mixed-mode interfacial fracture parameters, including the Mode I and Mode II stress intensity factors and the J-integral. The results show that a higher silica filler volume fraction increases the EMC stiffness and reduces its CTE. Global warpage and local interfacial crack-driving force exhibit distinct filler-dependent trends, indicating that global deformation alone does not fully represent the local fracture response. These findings highlight the importance of linking EMC filler-scale composition to both package-level deformation and interfacial fracture for the thermomechanical design of FOWLP.
