Search Results (264)

Advanced technologies, such as antimicrobial coatings on food contact surfaces (FCSs), are critical to prevent the occurrence of food-contaminating bacteria. Titanium dioxide coatings were fabricated by the sol–gel method on stainless steel following an experiment consisting of eight different combinations of these synthetic parameters: type of protocol (method), amount of surfactant, aging time, spinning speed, and sintering temperature. Hardness and elastic modulus values of the eight coating combinations were assessed by nanoindentation, and their values were statistically analyzed to determine which protocol and sintering temperature were significant influencing factors. Additional experimental points were procured to obtain trends relating sintering temperature to hardness and elastic modulus. Within the experimental range studied, hardness monotonically increased with sintering temperature, reaching its maximum value at 595 °C, while elastic modulus attained a maximum value at 640 °C. These maxima’s isotherms were overlapped on the coating’s photocatalytic activity contour plot to explore which combinations of protocol, aging time, and sintering temperature yielded optimal photocatalytic activity, hardness, and elastic modulus. The optimized coating was tested against two representative foodborne pathogens, Escherichia coli O157:H7 and Staphylococcus aureus cells and their biofilms, and was characterized by nanoindentation, scanning electron microscopy, and X-ray diffraction. The properties of the coating, as found in this study, present evidence for its potential FCS applications. Full article

This study reports the successful fabrication and application of floatable syntactic foams derived from fine magnesium powder (<45 µm) utilizing expanded perlite (0.25 g/cm³, 0.2–0.4 mm) as the pore former. Sample disks with densities as low as 0.9 g/cm³ were produced via the classical press and sinter process. To ensure reasonable mechanical properties, the specimens were formed under a pressure of 200 MPa in a hardened steel die, followed by high-vacuum sintering (~3 × 10⁻⁶ torr) at 640 °C for 1 h. The resulting foams exhibited sufficient mechanical strength to allow for precision machining into a microboat. We demonstrated their potential use as a Marangoni-induced microswimmer. Spontaneous locomotion was observed when ethanol was used as a propellant, which generates a surface tension gradient between the upper and rear parts of the swimmer. The microboats achieved propulsion speeds of approximately 160 mm/s when propelled by a 95% ethanol + 5% ink mixture. Using a small volume (~4 µL) of the alcohol mixture, the swimmer could cover distances exceeding 350 mm. Full article

Additive and coating technologies, such as high-velocity oxy-fuel (HVOF) thermal spraying and direct metal laser sintering (DMLS), often require extensive post-processing to meet dimensional and surface quality requirements, which remains challenging for nickel-based superalloys such as Inconel 718. This study presents the design and topology optimisation of a cutting tool with a linear cutting edge, capable of operating in turn-milling or turning modes, offering a viable alternative to conventional grinding. A non-optimised tool served as a baseline for comparison with a topology-optimised variant improving cutting-force distribution and stiffness-to-mass ratio. Finite element analyses and experimental turn-milling trials were performed on DMLS and HVOF Inconel 718 using carbide and CBN inserts. The optimised tool achieved significantly reduced roughness values: for DMLS, Ra decreased from 0.514 ± 0.069 µm to 0.351 ± 0.047 µm, and for HVOF from 0.606 ± 0.069 µm to 0.407 ± 0.069 µm. Rz was similarly improved, decreasing from 4.234 ± 0.343 µm to 3.340 ± 0.439 µm (DMLS) and from 5.349 ± 0.552 µm to 4.521 ± 0.650 µm (HVOF). The lowest measured Ra, 0.146 ± 0.030 µm, was obtained using CBN inserts at the highest tested cutting speed. All improvements were statistically significant (p < 0.005). No measurable tool wear was observed due to the small engagement and the use of a fresh cutting edge for each pass. The resulting surface quality was comparable to grinding and clearly superior to conventional turning. These findings demonstrate that combining topology optimisation with a linear-edge tool provides a practical and efficient finishing approach for additively manufactured and thermally sprayed Inconel 718 components. Full article

This study experimentally investigated boiling phenomena and heat transfer enhancement on sintered Cu micro/nanoporous surfaces under saturated pool boiling conditions. To evaluate the effects of the combined micro/nanostructures, microporous Cu layers and pillar-integrated surfaces were fabricated using micro-sized (diameter <75 mm) metal powder sintering, while nanostructures were formed through thermal oxidation. Boiling experiments revealed that the boiling heat transfer coefficient (BHTC) and critical heat flux (CHF) of the microporous Cu surfaces surpassed those of the reference surface SiO₂. The microporous pillar surface exhibited the best performance, demonstrating enhancements of approximately 2.7-fold and 7.3-fold in CHF and BHTC, respectively. High-speed imaging attributed this improvement to increased nucleation site density, rapid detachment and generation of small bubbles, efficient surface rewetting by capillary wicking, and liquid–vapor pathway separation enabled by the pillar geometry. Distinct transient temperature peaks and recoveries were observed on the oxidized pillar surfaces. Despite temporary overheating, strong capillary wicking from the superhydrophilic nanostructures recovered to the nucleate-boiling regime, which suppressed irreversible dryout and extended the boiling performance beyond the smooth surface CHF by 2.1 times. The results revealed that increasing the nucleation site density, enhancing the capillary-driven liquid supply, and ensuring effective separation of the vapor and liquid pathways improved the boiling heat transfer in multiscale porous structures. The sintered Cu micro/nanoporous surfaces demonstrated stable and efficient heat transfer across a wide range of heat fluxes, highlighting their potential for advanced thermal management applications and realizing optimally designed high-performance boiling surfaces. Full article

In this work, the results of the structural and phase state of LaNi₅-based alloys modified with Ti, Mn, and Co elements, obtained by mechanical alloying and subsequent spark plasma sintering, are presented. X-ray diffraction analysis was carried out to determine the phase composition, lattice parameters, microstrain, and average crystallite size, as well as to study the morphology and microstructure of the synthesized samples. It was established that the ball-to-powder ratio (BPR) and the milling speed affect the degree of intermetallic phase formation and the level of accumulated microstrains. The optimal mechanical alloying parameters make it possible to form the necessary precursor components for subsequent spark plasma sintering (SPS). It was determined that the SPS process effectively promotes the formation of intermetallic phases such as TiNi, LaNi₄Mn, LaNi₃Mn₂, and LaNi₄Co, ensuring high crystallinity and a reduction in defects accumulated during mechanical alloying. The morphology and microstructure of the samples with titanium, manganese, and cobalt additions showed that at the mechanical alloying stage, all systems are characterized by a dispersed and agglomerated structure, a wide particle size distribution, and a developed surface. After SPS, all series exhibited material consolidation and the formation of a dense matrix with distinct grain boundaries. Full article

This study evaluated the effects of different sintering protocols on the mechanical and microstructural properties of two multilayered zirconia materials: strength-gradient zirconia (KATANA YML) and color-gradient zirconia (KATANA UTML). Bar-shaped specimens were fabricated from both zirconia types. Three sintering protocols were applied: a manufacturer-recommended conventional protocol (7 h at 1550 °C), a high-speed protocol (54 min at 1600 °C), and a modified high-speed protocol (51 min at 1600 °C). Eighty-four specimens underwent three-point flexural strength testing. SEM and XRD analyses were used to assess microstructure and phase composition. No significant differences in flexural strength were found among sintering protocols (p > 0.05), but YML consistently showed higher strength than UTML (p < 0.05). The highest strength in YML was observed after high-speed sintering, followed by the shortened and conventional protocols. In UTML, the modified protocol yielded the highest strength, followed by the high-speed and then conventional protocol. SEM revealed finer, more homogeneous grains with shorter sintering times. XRD confirmed stable phase composition across all protocols. High-speed and modified high-speed sintering protocols can reduce processing time without compromising zirconia’s mechanical performance. Material type had a greater effect on flexural strength than sintering time, though microstructure was protocol dependent. Proper selection of zirconia type and sintering strategy is essential for optimal outcomes. Full article

Precision dicing with diamond wheels is a key technology in semiconductor dicing, integrated circuit manufacturing, aerospace, and other fields, owing to its high precision, high efficiency, and broad material applicability. As a critical processing stage, a comprehensive analysis of dicing technologies is essential for improving the machining quality of hard-and-brittle optoelectronic materials. This paper reviews the core principles of precision diamond wheel dicing, including dicing processes and blade preparation methods. Specifically, it examines the dicing mechanisms of composite and multi-mode dicing processes, demonstrating their efficacy in reducing defects inherent to single-mode approaches. The review also examines diverse preparation methods for dicing blades, such as metal binder sintering and roll forming. Furthermore, the roles of machine vision and servo control systems are detailed, illustrating how advanced algorithms facilitate precise feature recognition and scribe line control. A systematic analysis of key components in grinding wheel dicer is also conducted to reduce dicing deviation. Additionally, the review introduces models for tool wear detection and discusses material removal mechanisms. The influence of critical process parameters—such as spindle speed, feed rate, and dicing depth—on dicing quality and kerf width is also analyzed. Finally, the paper outlines future prospects and provides recommendations for advancing key technologies in precision dicing, offering a valuable reference for subsequent research. Full article

In this study, the effects of batch and continuous grinding on the ceramic floor tile body were investigated in terms of cost, capacity, and technical aspects. In batch milling, a changing speed during grinding was more efficient than a constant speed. Capacity and energy consumption increased as the mill rotation speed increased in continuous grinding. Specific energy consumptions were measured as 36 kW/ton and 43.1 kW/ton, with 1.6 ton/h and 8.375 t/h capacities. Additionally, d₁₀, d₅₀, and d₉₀ values for ground ceramic floor tile bodies were determined to be 2.5, 9.5, and 47.2 µm and 2.5, 9.4, and 48.1 µm for batch and continuous grinding, respectively. No significant difference was observed in the color and shrinkage values, while water absorptions were calculated to be 1.1% and 0.3% as sintering properties for batch and continuous methods, respectively. In the phase analysis of a sintered body prepared using the continuous method, mullite and quartz were observed, while microcline was also analyzed differently from such minerals for the batch one. Structural changes, surface morphology, and roughness were also interpreted by DTA/TG, SEM, and AFM analysis. The presence of plastic clay minerals during the grinding process in batch milling caused non-plastic raw materials not to be ground sufficiently, and sintering characteristics changed. Full article

This study investigated the effect of piranha solution etching duration on the shear bond strength of zirconia ceramics bonded to resin cement, comparing it to conventional sandblasting treatment. Fifty fully sintered zirconia specimens (6.0 mm diameter, 4.0 mm thickness) were prepared and randomly divided into five groups (n = 10): sandblasting control and piranha solution treatment for 1, 2, 3, and 4 min. Piranha solution was prepared by mixing 98% H₂SO₄ and 35% H₂O₂ in a 3:1 ratio. All specimens were bonded to resin composite cylinders using dual-cure resin cement. Shear bond strength testing was performed using a universal testing machine at a 0.5 mm/min crosshead speed. Failure modes were analyzed using a stereomicroscope and classified as adhesive, cohesive, or mixed failures. One-way ANOVA revealed significant differences between groups (p < 0.05). Tukey’s post hoc test showed that 1-min piranha treatment produced significantly lower bond strength (7.64 ± 2.02 MPa) compared to all other groups. The 2-min (15.17 ± 2.79 MPa), 3-min (14.99 ± 3.27 MPa), and 4-min (18.34 ± 3.15 MPa) piranha treatments showed no significant differences compared to sandblasting (15.41 ± 2.61 MPa). Failure mode analysis revealed 100% adhesive failures for the 1-min group, while all other groups showed 80% adhesive and 20% mixed failures. Piranha solution treatment duration significantly affected zirconia bonding performance. While 1-min treatment proved inadequate, 2–4 min treatments achieved bond strengths comparable to sandblasting. The findings suggest that piranha solution treatment for 2–4 min represents a viable alternative to sandblasting for zirconia surface preparation, with the 2-min protocol being the most efficient choice for clinical application. Full article

Modern manufacturing is increasingly shaped by the paradigm of Industry 4.0 (Smart Manufacturing). As one of its nine pillars, additive manufacturing plays a crucial role, enabling high-quality final products with improved profitability in minimal time. Advances in this field have facilitated the emergence of diverse technologies—such as Fused Deposition Modelling (FDM), Stereolithography (SLA), and Selective Laser Sintering (SLS)—allowing the use of metallic, polymeric, and composite materials. Within this context, Klipper v.0.12, an open-source firmware for 3D printers, addresses the performance limitations of conventional consumer-grade systems. By offloading computationally intensive tasks to an external single-board computer (e.g., Raspberry Pi), Klipper enhances speed, precision, and flexibility while reducing prototyping time. The purpose of this study is twofold: first, to identify and analyze bottlenecks in low-cost 3D printers and second, to evaluate how these shortcomings can be mitigated through the integration of supplementary hardware and software (Klipper firmware, Raspberry Pi, additional sensors, and the Mainsail interface). The scientific contribution of this study lies in demonstrating that a consumer-grade FDM 3D printer can be significantly upgraded through this integration and systematic calibration, achieving up to a 50% reduction in printing time while maintaining dimensional accuracy and improving surface quality. Full article

Background: To overcome the esthetic limitations of dental monolithic zirconia restorations, multichromatic systems were developed to combine improved structural integrity with a natural shade gradient that mimics the optical properties of natural teeth. In response to the clinical demand for time-efficient, i.e., chairside fabrication of zirconia restorations, rapid sintering protocols have become necessary to adjust clinical efficiency along with material performance. This study addresses the challenges of a rapid sintering protocol related to optical performance and phase transformation of the final restoration and the zirconia–cell interaction. Methods: The influence of a rapid sintering protocol on the color stability of the final dental restoration was evaluated by the CIE L*a*b* color space. Phase transformation was assessed through X-ray diffraction analysis. Cellular behavior was evaluated by measuring wettability, the material’s surface energy, and a cell mitochondrial activity assay on human gingival fibroblasts. Results: Optical measurements demonstrated that the total color change in all layers after rapid sintering was above the perceptibility threshold (ΔE* > 1.2), while only the polished enamel layer (ΔE* = 3.01) exceeded the acceptability threshold (ΔE* > 2.7), resulting in a clinically perceptible mismatch. Results of X-ray diffraction analysis, performed for fixed occupancy at Z_0.935Y_0.065O_0.984, revealed that rapid sintering caused a decrease in the cubic (C-) phase and an increase in the total amount of tetragonal (T-) phases. Conventionally sintered zirconia consists of 54% tetragonal (T-) and 46% cubic (C-) phase, whereas in the speed-sintered specimens, an additional T1 phase was detected (T = 49%; T1 = 27%), along with a reduced cubic fraction (C = 24%). Additionally, a small amount of the monoclinic (M) phase is noticed. Although glazing as a surface finishing procedure resulted in increased hydrophilicity, both polished and glazed surface-treated specimens showed statistically comparable cell adhesion and proliferation (p > 0.05). Conclusions: Rapid sintering induced perceptible color changes only in the enamel layer of multichromatic zirconia, suggesting that even layer-specific alterations may have an impact on the overall esthetic outcome of the final prosthetic restoration. Five times higher heating and cooling rates caused difficulty in reaching equilibrium, leading to changes in lattice parameters and the formation of the metastable T1 phase. Full article

Zirconia is widely used in prosthodontics due to its excellent biocompatibility, mechanical properties, and esthetic characteristics. This article reviews the fundamentals of sintering zirconia for prosthodontic applications. Various sintering techniques, including conventional, spark plasma, high-speed, and microwave sintering, are discussed regarding their influence on translucency, strength, and microstructure. This review aims to provide a comprehensive reference for the sintering methods of zirconia currently used or may be used for dental prosthodontics. Full article

The reconstruction of segmental bone defects requires patient-specific scaffolds that combine mechanical safety, biological functionality, and rapid manufacturing. We converted CT-derived mandibular geometry into a functionally graded Ti-6Al-4V lattice and optimised porosity, screw layout, and strut thickness through a cyber-physical loop that joins high-fidelity FEM, millisecond ANN, and a BN for uncertainty quantification. Fifteen candidate scaffolds were fabricated by direct metal laser sintering and hot isostatic pressing and were mechanically tested. FEM predicted stress and stiffness with 98% accuracy; the ANN reproduced these outputs with 94% fidelity while evaluating 10,000 designs in real time, and the BN limited failure probability to <3% under worst-case loads. The selected 55–65% porosity design reduced titanium use by 15%, shortened development time by 25% and raised multi-objective optimisation efficiency by 20% relative to a solid-plate baseline, while resisting a 600 N bite with a peak von Mises stress of 225 MPa and micromotion < 150 µm. Integrating physics-based simulation, AI speed, and probabilistic rigour yields a validated, additively manufactured scaffold that meets surgical timelines and biomechanical requirements, offering a transferable blueprint for functional scaffolds in bone and joint surgery. Full article

Fuel layered-distribution sintering (FLDS) is a technology that can effectively reduce fuel consumption and achieve a more uniform temperature distribution within the sintering bed compared to traditional iron ore sintering. In this study, the melting quality index, combined with the maximum temperature and the duration of melting temperature, are used as performance indicators to investigate the effects of coke size and oxygen content on sintering characteristics under layered fuel distribution conditions. The results indicate that increasing the oxygen content can enhance the velocity of the flame front in the sinter pot, thereby accelerating the sintering process. However, excessive oxygen content may lead to fluctuations in the quality of the sinter. Small coke sizes provide higher melting quality in the upper region of the sinter pot, while large coke sizes perform better in the lower region. For a 600 mm sintering bed layer, an oxygen enrichment time of 6 min with oxygen concentration of 27% and coke particle diameter of 2.0 mm can balance sintered ore quality, sintering time, and flame front speed, ensuring the yield of sintered ore. These findings provide an effective pathway for energy saving and emission reduction in iron ore sintering plants. Full article

In the power industry, various electrically insulating materials are used to ensure proper mechanical, thermal, and dielectric performance over decades of equipment operation. In power transformers, cellulose is the predominant material in manufacturing various insulation components. Most of these products are manufactured by wet-molding technology. However, this process is long, labor-intensive, and highly energy-demanding. Under the frame of an EU-funded grant, a new kind of insulation material and manufacturing process were developed. Fully bio-based material (produced in the form of pellets) can be processed using additive manufacturing, allowing for much shorter manufacturing times for insulation products, with considerably less scrap and energy consumption (due to the elimination of the drying stage). The focus of the project was extrusion additive manufacturing technology, but at a later stage, a biomaterial powder was developed, making it possible to print with other technologies. In the paper, comparative studies on various additive manufacturing techniques of newly developed biopolymers have been presented, including extrusion, High Speed Sintering (HSS), and Selective Laser Sintering (SLS). The applicability of such material in power transformers required extensive testing of various properties. These results are discussed in the paper and include: oil compatibility, volume resistivity measurements, permittivity and dissipation factor measurements, determination of partial discharge inception voltage, partial discharges measurement, and breakdown voltage measurements. Although mechanical properties remain below industrial targets, the pioneering results provide a promising route for unique directions toward more sustainable manufacturing of high-voltage cellulose insulation and ideas for improving the material properties during the printing process. Full article