Search Results (206)

Ceramic dental prosthetics with internal metal structures are made from a cobalt–chromium alloy that is coated with ceramic. This study aims to validate surface treatments for the metal that enhance the adhesion of the ceramic coating under masticatory forces. Surface conditioning is performed using mechanical methods, like sandblasting (SB), and thermal methods, such as oxidation (O). The ceramic coating is applied to the metal component following the conditioning process, which can be conducted using either a single method or a combination of methods. Each conditioned sample undergoes characterization through various techniques, including drop shape analysis (DSA), scanning electron microscopy (SEM), X-ray diffraction (EDX), and atomic force microscopy (AFM). After the ceramic coating is applied and subjected to thermal sintering, the metal–ceramic samples are mechanically tested to assess the adhesion of the ceramic layer. The research findings, illustrated by scanning electron microscopy (SEM) images of the metal structures’ surfaces, indicate that alloy powder particles ranging from 10 to 50 µm were either adhered to the surfaces or present as discrete dots. Particles that exceed the initial design specifications of the structure can be smoothed out using sandblasting or mechanical finishing techniques. The energy-dispersive spectroscopy (EDS) results show that, after sandblasting, fragments of aluminum oxide remain trapped on the surface of the metal structures. These remnants are considered impurities, which can negatively impact the adhesion of the ceramic to the metal substrate. The analysis focuses on the exfoliation of the ceramic material from the deformed metal surfaces. The results emphasize the significant role of the sandblasting method and the micro-topography it creates, as well as the importance of the oxidation temperature in the treatment process. Drawing on 25 years of experience in dental prosthetics and the findings from this study, this publication aims to serve as a guide for applying the ceramic bonding layer to metal surfaces and for conditioning methods. These practices are essential for enhancing the adhesion of ceramic materials to metal substrates. Full article

This study explored the effects of the finishing deformation temperature on the microstructure and properties of CrVNb micro-alloyed steel following thermomechanical processing (TMP). The investigation encompassed the influence of the deformation temperature on the ferrite grain size, precipitate characteristics, hardness and flow stress. The microstructure characterization was performed using optical and electron microscopy techniques. The results show that decreasing the deformation temperature refined the ferrite grains, though a bimodal ferrite grain structure formed when the deformation temperature fell to about 100 °C below the Ar3 temperature. Additionally, lower deformation temperatures increased the number density of strain-induced precipitates (SIPs), whereas the density of finer precipitates (random and interphase precipitates (IPs)) decreased. The highest hardness was observed in a sample deformed at 950–850 °C temperatures. These findings highlight the impact of the finishing deformation temperatures on the microstructural and mechanical properties, providing valuable insights for optimizing steel processing conditions. Full article

This study examined the effect of build orientation on the surface finish of micro-optofludic (MoF) devices fabricated via a polydimethylsiloxane (PDMS)-based 3D-printing primary–secondary fabrication protocol, where an inkjet 3D-printing technique was implemented. The molds (i.e., primaries) for fabricating the MoF devices were 3D-printed in two orientations: along $XY$ (Dev-1) and across $YX$ (Dev-2) the printhead direction. Next, the surface finish was characterized using a profilometer to acquire the primary profile of the surface along the microchannel’s edge. The results indicated that the build orientation had a strong influence on the latter, since Dev-1 displayed a tall and narrow Gaussian distribution for a channel width of 398.43 ± 0.29 µm; Dev-2 presented a slightly lower value of 393.74 ± 1.67 µm, characterized by a flat and broader distribution, highlighting greater variability due to more disruptive, orthogonally oriented, and striated patterns. These results were also confirmed by hydrodynamically testing the two MoF devices with an air–water slug flow process. A large experimental study was conducted by analyzing the mean period trend in the slug flow with respect to the imposed flow rate and build orientation. Dev-1 showed greater sensitivity to flow rate changes, attributed to its smoother, more consistent microchannel geometry. The slightly narrower average channel width in Dev-2 contributed to increased flow velocity at the expense of having worse discrimination capability at different flow rates. This study is relevant for optimizing 3D-printing strategies for the fabrication of high-performance microfluidic devices, where precise flow control is essential for applications in biomedical engineering, chemical processing, and lab-on-a-chip systems. These findings highlight the effect of microchannel morphology in tuning a system’s sensitivity to flow rate modulation. Full article

Properly refrigerating hard-to-cut alloys during grinding is key to achieve high quality, strict tolerances, and good surface finishing. Nonetheless, literature about the influence of cooling-lubrication conditions (CLCs) on dimensional accuracy of ground components is still scarce. Thus, this work aims to evaluate surface quality, grinding power, and dimensional accuracy of Inconel 718 workpieces after grinding with silicon carbide grinding wheel at different grinding conditions. Four different CLCs were tested: flood, minimum quantity of lubrication (MQL) without graphene, and with multilayer graphene (MG) at two distinct concentrations: 0.05 and 0.10 wt.%. Different radial depths of cut values were also tested. The results showed that the material’s removed height increased with radial depth of cut, leading to coarse tolerance (IT) grades. Machining with the MQL WG resulted in higher dimensional precision with an IT grade varying between IT6 and IT7, followed by MQL MG 0.10% (IT7), MQL MG 0.05% (IT7-IT8), and flood (IT8). The lower tolerances achieved with MG were attributed to the lowering in the friction coefficient of the workpiece material sliding through the abrasive grits with no material removal (micro-plowing mechanism), thereby reducing grinding power and the removed height in comparison to the other CLC tested. Full article

Wire electrical discharge machining (WEDM) is a standard micro-manufacturing technology. In WEDM, surface roughness (SR), deviation dimension (DD), and machining time (MT) are critical requirements that impact machining quality and are affected by various input parameters. The workpiece often performs multiple machining steps (roughing, semi-finishing, and finishing) to achieve high accuracy. Each machining step directly affects the accuracy and machining time, and the preceding machining step influences the subsequent machining step parameters. Many input control parameters regulate WEDM’s performance. Thus, optimizing process control parameters at each step is essential to achieve optimal results. This study investigates the influence of input parameters, including pulse on time (Ton), pulse off time (Toff), and servo voltage (SV), on SR, DD, and MT when machining AISI D2 mold steel through rough, semi-finish, and finish cutting. Taguchi and Analysis of Variance (ANOVA) are applied to analyze and optimize this WEDM process. The results display that the optimal surface roughness values for rough, semi-finish, and finish-cut stages are 2.03 µm, 1.77 µm, and 0.57 µm, corresponding to the parameter set of Ton = 6 μs, Toff = 10 μs, and SV = 30 V; Ton = 3 μs, Toff = 15 μs, and SV = 60 V; and Ton = 21 μs, Toff = 45 μs, and SV = 60 V, respectively. In addition, in the finish-cut stage, the parameters for optimal DD of 0.001 mm (0.04%) are Ton = 3 μs, Toff = 15 μs, and SV = 40 V. In contrast, those values for optimal MT of 218 s are Ton = 3 μs, Toff = 30 μs, and SV = 40 V. All optimal input values are confirmed by the manufacturing mold and die parts. Full article

The burr removal and finishing of drilled hole walls typically require multiple post-processing steps. This experimental study introduces a novel single-step drilling approach using modified drill bits for simultaneous burr removal and surface finishing in aluminum 6061-T6. The odified-1 drill, equipped with a deburring micro-insert, achieved superior results, with a chamfer height of −2.829 mm, drilling temperature of 40.28 ◦C, and surface roughness of 0.082 µm under optimal conditions. Multi-objective optimization using the RSM and MOGA-ANN identified the optimal drilling parameters for the Modified-1 drill at 3000 rpm under water lubrication as compared to dry conditions and kerosene. Experimental validation confirmed the high prediction accuracy, with deviations under 6%. These results establish the Modified-1 twist drill bit with a deburring
 micro-insert as a highly effective tool for burr-free high-quality drilling in a single operation. This innovative drill design presents an efficient, single-step solution for burr elimination, chamfer formation, and surface finishing in drilling operations. Full article

The metal thickness uniformity of the micro-electroforming process determines the structural accuracy, surface finish, and functional characteristics, which directly affect the quality, performance, and reliability of the final parts. However, due to the non-uniformity of the electric field distribution, the problem of thickness non-uniformity in the micro-electroforming process has always been one of the key challenges limiting its application and development. The auxiliary cathode structure can improve the uniformity of electroforming thickness by regulating the cathode electrodeposition rate and electric field distribution and is widely used in the micro-electroforming process. In this study, with the micro-array metal die core as the research object, based on finite element simulations, the effect of the geometrical parameters of the auxiliary cathode on the thickness uniformity of electroforming is analyzed in depth. This study introduces the optimization method of the BP neural network and the NSWOA (Non-dominated Sorting Whale Optimization Algorithm) and achieves a significant improvement in the unevenness of electroforming thickness by designing and adjusting the parameters of the position, width, and shape of the auxiliary cathode. The unevenness of the microarray metal mold core is reduced to 4% from 475% without the auxiliary cathode, using the auxiliary cathode structure designed with this method. Full article

The 316L stainless steel material boasts exceptional corrosion resistance and plasticity, among other benefits, and finds extensive application in automotive components, molds, aerospace parts, biomedical equipment, and more. This work focuses on the surface polishing of selective laser melting (SLM) 316L stainless steel using 1064 nm nanosecond laser processing and mechanical grinding. The influence of laser processing parameters on the surface roughness of SLM-316L stainless steel was investigated using an orthogonal experiment. After laser processing, the surface roughness of SLM-316L stainless steel was reduced from 7.912 μm to 1.936 μm, but many randomly distributed irregular micro-cracks appeared on the surface. EDS and XRD detections illustrated that iron oxides were generated on the surface of SLM-316L stainless steel after laser processing. Mechanical grinding was further performed to achieve a nanometer surface finish and remove the metal oxides and micro-cracks generated on the surface of SLM-316L stainless steel after laser processing. The AFM measurement results indicate that the surface roughness of SLM-316L stainless steel was reduced to approximately 3 nm after mechanical grinding. Moreover, the micro-cracks and iron oxides on the surface of laser-processed SLM-316L stainless steel were completely removed. This work provides guidance for the precision polishing of SLM-316L stainless steel. Full article

Sustainable development initiatives are essential for enhancing the social economy and environmental preservation in marginalised rural areas of Tanzania. This study examines the impact of an IoT micro-factory on sustainable development, addressing issues such as inadequate production techniques, agribusiness monopolisation practices, the shortage of small-scale factories, and the failure to leverage global market comparative advantages. It explores the mediating role of architectural innovation and the moderating role of industrial symbiosis. The study surveyed 196 participants, including 100 orange farmers, 96 industrial engineers in the beverage sector, and conducted interviews with 3 industrial managers and 3 industrial consultants. SmartPLS 4 was used to evaluate the relationships between constructs. The results indicate that both IoT micro-factories and global production networks (GPNs) have a direct influence on sustainable social-economic development. Architectural innovation mediates these relationships, while industrial symbiotic moderates the interaction between IoT micro-factories and architectural innovation. The findings emphasise the importance of IoT micro-factories for sustainable development, with industrial symbiotic relationships addressing gaps in knowledge, skills, and equitable trade. The industrial stakeholders should prioritise IoT micro-factories as small-scale factories to promote sustainable development in rural communities of developing countries. Full article

Micro-milling is increasingly recognized as a crucial technique for machining intricate and miniature 3D aerospace components, particularly those fabricated from difficult-to-cut Ti-6Al-4V alloys. However, its practical applications are hindered by significant challenges, particularly the unavoidable generation of burrs, which complicate subsequent finishing processes and adversely affect overall part quality. To optimize the burr formation in the micro-milling of Ti-6Al-4V alloys, this study proposes a novel hybrid-ranking optimization algorithm that integrates Grey Relational Analysis (GRA) with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This approach innovatively combines GRA and TOPSIS with a random forest regression (RFR) model, facilitating the exploration of nonlinear and complex relationships between input parameters and machining outcomes. Specifically, the effects of spindle speed, depth of cut, and feed rate per tooth on surface roughness and burr width generated during both down-milling and up-milling processes were systematically investigated using the proposed methodology. The results reveal that the depth of cut is the most influential factor affecting surface roughness, while feed rate per tooth plays a critical role in controlling burr formation. Moreover, the GRA-TOPSIS-RFR method significantly outperforms existing optimization and prediction models, with the integration of the RFR model enhancing prediction accuracy by 42.6% compared to traditional linear regression approaches. The validation experimental results agree well with the GRA-TOPSIS-RFR-optimized outcomes. This research provides valuable insights into optimizing the micro-milling process of titanium components, ultimately contributing to improved quality, performance, and service life across various aerospace applications. Full article

The draping of textile semi-finished products for complex geometries is still prone to errors, e.g., wrinkles, gaps, and fiber undulations, leading to reduced mechanical properties of the composite. Reinforcing textiles made from carbon fiber (CF) rovings (i.e., endless continuous fibers) can be draped mainly based on their ability to deform under in-plane shearing. However, CF rovings are hardly stretchable in the fiber direction. These limited degrees of freedom make the production of complex shell-shaped geometries from standard CF-roving fabrics challenging. Contrary to continuous rovings, this paper investigates the processing of spun yarns made of recycled carbon fibers (rCFs), which are discontinuous staple fibers with defined lengths. rCFs are obtained from end-of-life composites or production waste, making them a sustainable alternative to virgin carbon fibers in the high-performance components of, e.g., automobiles, boats, or sporting goods. These staple fiber-spun yarns are considerably more stretchable, which is due to the ability of the individual fibers to slide against each other when deformed, resulting in improved formability of fabrics made from rCF yarns, enabling the draping of much more complex structures. This study aims to develop and characterize woven fabrics based on previous studies of rCF yarns for thermoset composites. In order to investigate staple fiber-spun yarns, a previous micro-scale modeling approach is extended. The formability of fabrics made from those rCF yarns is investigated through experimental forming tests and meso-scale simulations. Full article

This study focuses on preparing and characterizing functionalized silver nanoparticle-based (Ag-F NPs) finishing agents for leather treatment. Ag-F NPs were synthesized and functionalized through a ligand exchange process with citric acid, enhancing their dispersion stability in aqueous media. The nanoparticles were incorporated into polyurethane- and nitroemulsion-based finishing formulations and applied to ovine and bovine leather via a spray coating process. Morphological (SEM, TEM), structural (XRD), thermal (TGA), and spectroscopic (FT-IR) analyses confirmed successful functionalization and uniform dispersion within the finishing layer. Leather samples treated with Ag-F NPs exhibited a significant improvement in antibacterial properties, with microbial growth reduction of up to 90% after 72 h. Additionally, accelerated aging tests demonstrated enhanced UV resistance, with a 30% lower color change (∆E) compared to control samples. The Ag-F NPs-based finishing layers also exhibited superior abrasion and micro-scratch resistance, maintaining a stable coefficient of friction over time. These findings demonstrate the potential of Ag-F NPs as multifunctional leather-finishing agents, making them highly suitable for applications in the automotive, footwear, and leather goods industries. Full article

Background/Objectives: Since biomineralization by calcium silicate-based sealers (CSBSs) was reported, retrieving canal filling materials may be challenging during endodontic retreatment due to their adhesion to dentin. This study aimed to evaluate the possibility of removing residual mineral deposits from two kinds of CSBSs compared to the AH Plus Jet (AHJ). Methods: Root canals of mandibular premolars were prepared, obturated with the sealer-based obturation method using a WOG medium gutta-percha cone and one of the following sealers: AHJ, AH Plus Bioceramic (AHB), and Ceraseal (CER) (n = 12/group). After 3 weeks, endodontic retreatment was conducted with the WOG files, followed by instrumentation with XP-endo Finisher (XPF). Micro-computed tomography scanning was obtained after canal filling, after retreatment with WOG, and after the use of XPF. The percentage of the removed filling volume was calculated. One-way ANOVA with Tukey’s test and a non-parametric test with Bonferroni’s correction were performed. Root canal dentin after retreatment was examined using a scanning electron microscope (SEM). Results: After supplementary instrumentation with XPF, the mean residual filling volumes for the AHJ, AHB, and CER groups were 1.35 mm³, 0.55 mm³, and 0.82 mm³, respectively. The AHJ group showed greater residual volume compared to the AHB group (p < 0.05). The AHB and CER groups demonstrated higher mean percentages of removed filling volume at 94.8%, and 92.5%, respectively, compared to 87.1% for the AHJ group (p < 0.05). More mineral deposits were observed in the CER group with SEM. Conclusions: AHB and CER are retrievable during endodontic retreatment, with CER preferable due to greater mineral deposits in dentinal tubules. Full article

In October 2021, a mural painting was discovered in the crypt of Parma Cathedral (Italy). It was covered by a wall, erasing it form historical memory. The painting, presumably from the 15th–16th century, depicts the Madonna and Child enthroned in the center, between Saints Peter and John. Before the restoration project, investigations were conducted with different techniques to identify the pigments and binders used, the nature of the surface finish and the efflorescence. Micro-Raman spectroscopy detected numerous pigments compatible with the presumed age. An interesting result concerns the presence of crocoite (lead chromate), an unusual and rare pigment for this period. These pigments were confirmed through investigation by means of Scanning Electron Microscopy coupled to Energy-Dispersive X-ray Spectroscopy (SEM-EDS). Fourier Transform Infrared Spectroscopy (FT–IR) and Gas Chromatography/Mass Spectroscopy (GC/MS) were used to identify the binder and the type of wax used in the finish layer. The rather widespread presence of egg, used to spread the paint, allows us to affirm that this mural painting was created as a fresco, with substantial parts a secco. Full article

Doce de leite is a caramel-like confection, mainly produced in several Latin American countries, with increasing popularity worldwide. This overview outlines nine distinct industrial technologies for the production of doce de leite: (1) total batch manufacturing process; (2) batch manufacturing system with fractionated mix addition; (3) manufacturing with pre-concentration in a vacuum evaporator and finishing in an open pan; (4) manufacturing with pre-concentration in a vacuum evaporator, finishing in an open pan, and lactose micro-crystallization; (5) continuous flow manufacturing with total concentration in a vacuum evaporator and a viscosity control holding tank (hot well); (6) manufacturing with total concentration in a vacuum evaporator and sterilization in an autoclave system; (7) manufacturing with sucrose pre-caramelization and a total batch system; (8) manufacturing in colloidal mill without an evaporation process; and (9) manufacturing based of doce de leite bars with a sucrose crystallization stage. We conducted a literature review to gather data on the discussed processes and their principal characteristics, which may be pertinent to doce de leite manufacturers. The choice of a specific process will depend on the desired doce de leite characteristics, the type of doce de leite to be produced, and the manufacturing company’s requirements. When properly integrated, these technologies contribute to efficient and profitable production, yielding high-quality products with appropriate chemical, microbiological, and sensory characteristics at an industrial scale. Full article