Design and Manufacturing of Si-Based Non-Oxide Cellular Ceramic Structures through Indirect 3D Printing

Additive manufacturing of Polymer-Derived Ceramics (PDCs) is regarded as a disruptive fabrication process that includes several technologies such as light curing and ink writing. However, 3D printing based on material extrusion is still not fully explored. Here, an indirect 3D printing approach combining Fused Deposition Modeling (FDM) and replica process is demonstrated as a simple and low-cost approach to deliver complex near-net-shaped cellular Si-based non-oxide ceramic architectures while preserving the structure. 3D-Printed honeycomb polylactic acid (PLA) lattices were dip-coated with two preceramic polymers (polyvinylsilazane and allylhydridopolycarbosilane) and then converted by pyrolysis respectively into SiCN and SiC ceramics. All the steps of the process (printing resolution and surface finishing, cross-linking, dip-coating, drying and pyrolysis) were optimized and controlled. Despite some internal and surface defects observed by topography, 3D-printed materials exhibited a retention of the highly porous honeycomb shape after pyrolysis. Weight loss, volume shrinkage, roughness and microstructural evolution with high annealing temperatures are discussed. Our results show that the sacrificial mold-assisted 3D printing is a suitable rapid approach for producing customizable lightweight highly stable Si-based 3D non-oxide ceramics.

ELID Mirror Surface Grinding for Concave Molds by Conductive Elastic Wheel Containing Carbon Black

Elastic grinding wheels have previously been adopted for the development of the mirror surface finishing method for concave spheres. In this study, new conductive elastic grinding wheels, to which electrolytic in-process dressing (ELID) can be applied, are developed; the aim of the study is to address the challenge of maintaining a constant removal rate for rubber bond wheels. When ELID grinding is performed using a non-diene (isobutane isoprene rubber, IIR)-based wheel, a larger removal amount is achieved, and a higher-quality surface is also achieved compared to a diene (acrylonitrile-butadiene rubber, NBR)-based wheel. In addition, to investigate the effect of grinding wheel bond hardness on the removal amount and ground shape accuracy, grinding wheels with various levels of hardness are prepared by controlling the amount of carbon black contained in them, and grinding experiments are conducted. Thus, a larger removal amount is achieved using a harder grinding wheel, but the roughness of the ground surfaces deteriorates. Therefore, in practice, it is necessary to select an appropriate grinding wheel that can achieve both productivity and surface quality. Finally, to obtain a high-quality mirror finish on a concave spherical surface, ELID grinding is performed on the workpieces as is done for spherical lens molds. Thus, high-quality mirror surfaces with roughness Ra < 10 nm were generated. When the work pieces are ground using a grinding wheel of the same radius, excessive removal occurs at the edge of the concave spherical profile, decreasing the form accuracy. Numerical simulation demonstrates that chamfering of the grinding wheel is effective for improving the shape accuracy. The results of this study are expected to contribute to automation and cost reduction in the mirror-finishing process for concave molds.

Development of Antibacterial and Antifouling Innovative and Eco-Sustainable Sol–Gel Based Materials: From Marine Areas Protection to Healthcare Applications

Bacterial colonization of surfaces is the leading cause of deterioration and contaminations. Fouling and bacterial settlement led to damaged coatings, allowing microorganisms to fracture and reach the inner section. Therefore, effective treatment of surface damaged material is helpful to detach bio-settlement from the surface and prevent deterioration. Moreover, surface coatings can withdraw biofouling and bacterial colonization due to inherent biomaterial characteristics, such as superhydrophobicity, avoiding bacterial resistance. Fouling was a past problem, yet its untargeted toxicity led to critical environmental concerns, and its use became forbidden. As a response, research shifted focus approaching a biocompatible alternative such as exciting developments in antifouling and antibacterial solutions and assessing their antifouling and antibacterial performance and practical feasibility. This review introduces state-of-the-art antifouling and antibacterial materials and solutions for several applications. In particular, this paper focuses on antibacterial and antifouling agents for concrete and cultural heritage conservation, antifouling sol–gel-based coatings for filtration membrane technology, and marine protection and textile materials for biomedicine. In addition, this review discusses the innovative synthesis technologies of antibacterial and antifouling solutions and the consequent socio-economic implications. The synthesis and the related physico-chemical characteristics of each solution are discussed. In addition, several characterization techniques and different parameters that influence the surface finishing coatings deposition were also described.

In-Process Chatter Detection Using Signal Analysis in Frequency and Time-Frequency Domain

All machining processes involve vibrations generated by structural sources such as a machine’s moving parts or by the interaction between cutting tools and work-pieces. Relative vibrations between the work-pieces and the cutting tool are the most relevant from the point of view of the regenerative chatter phenomenon. In fact, these vibrations can lead to a chip yregeneration effect, which results in unwanted consequences, rapidly degenerating towards a very poor quality of surface finishing or, in case of severe chatter conditions, to machine-tool or work-piece damage. In the past decades, two different approaches for chatter avoidance were proposed by the scientific community, and they are commonly referred to as Out-of-Process (OuP) and in-Process (iP) solutions. The OuP solutions are off-line approaches, which allow to properly set the working parameters before machining starts. Ip solutions are on-line techniques, which allow to dynamically change the working parameters during machining by using single or multiple sensors. By monitoring the machining process, iP algorithms try to keep the machining process in stable working conditions while keeping high productivity levels. This study dealt with a novel iP chatter-detection strategy based on the Power Spectral Density (PSD) analysis and on the Wavelet Packet Decomposition (WPD) of different sensor signals. The preliminary results demonstrate the stability and feasibility of proposed indicators for chatter detection in industrial application.

Monitoring and Predicting the Surface Generation and Surface Roughness in Ultraprecision Machining: A Critical Review

The aim of manufacturing can be described as achieving the predefined high quality product in a short delivery time and at a competitive cost. However, it is unfortunately quite challenging and often difficult to ensure that certain quality characteristics of the products are met following the contemporary manufacturing paradigm, such as surface roughness, surface texture, and topographical requirements. Ultraprecision machining (UPM) requirements are quite common and essential for products and components with optical finishing, including larger and highly accurate mirrors, infrared optics, laser devices, varifocal lenses, and other freeform optics that can satisfy the technical specifications of precision optical components and devices without further post-polishing. Ultraprecision machining can provide high precision, complex components and devices with a nanometric level of surface finishing. Nevertheless, the process requires an in-depth and comprehensive understanding of the machining system, such as diamond turning with various input parameters, tool features that are able to alter the machining efficiency, the machine working environment and conditions, and even workpiece and tooling materials. The non-linear and complex nature of the UPM process poses a major challenge for the prediction of surface generation and finishing. Recent advances in Industry 4.0 and machine learning are providing an effective means for the optimization of process parameters, particularly through in-process monitoring and prediction while avoiding the conventional trial-and-error approach. This paper attempts to provide a comprehensive and critical review on state-of-the-art in-surfaces monitoring and prediction in UPM processes, as well as a discussion and exploration on the future research in the field through Artificial Intelligence (AI) and digital solutions for harnessing the practical UPM issues in the process, particularly in real-time. In the paper, the implementation and application perspectives are also presented, particularly focusing on future industrial-scale applications with the aid of advanced in-process monitoring and prediction models, algorithms, and digital-enabling technologies.

Roughness Effect on Corrosion of Gr-Cu -Ni Coated Steel in Saline Water

Effect of surface roughness on corrosion behavior for carbon steel was coated by metallic layers Cu- Ni Reinforced with Gr layers. Surface finishing P320, P600 and P1200 mesh used until a mirror shiny surface before metallic coated with Gr layers at consecrations 0.25, 0.5, 1and 2 g/l of Gr. First, X-ray diffraction), electron microscopy associated for carbon steel & Gr and Microscopic test for coated specimens. The techniques were performed to study the effect of saline water (3.5%) on the corrosion behaviors, Open circuit potential, Tafel polarization and impedance spectroscopy tests. At P320 Equivalent Circuit elements were decreasing but, Corrosion reaction’s Rp was increased at 5 min and 0.25 g/l. And also, coating’s Rpore with Electrolyte’s Ru were increasing at 30 min for 0.5 g/l, and also coating’s Rpore and Electrolyte’s Ru were increased at 20 min for 1 g/l, At P600 ECE’s were decreasing but, corrosion reaction’s Rp was increased at 30 min 1 g/l, and also, coating’s Rpore and Electrolyte’s Ru were increased at 20 min for 1 g/l, and At P1200 ECE’s were decreasing but, Coating’s Ccoat was increased at 5 min 0.25 g/l, and also coating’s Rpore and Electrolyte’s Ru were increased at 0.5g/l, 30 min.

The Effect of Different Pre-Surface Finishing Method on the Aluminium Anodization of the 6XXX Series Alloy

In this study, the effect of different pre-surface finishing method on the aluminium anodization was investigated for AA 6063 alloy. Within the scope of pre-surface finishing method which is acidic solution concentrations and process time were determined. Acidic solution was determined by using hydrofluoric acid (HF) and nitric acid (HNO3). Also Gresoff LIM-5 LV chemical was used with different concentrations and process time for degreasing process. The etching effect of acidic solution on aluminium samples was investigated. The optimal etching behaviour was obtained with 1.0% concentration of HF and 3.2% concentration of HNO3 at 10 minutes process time. Also optimal surface properties were observed with 1.0% concentration of Gresoff LIM-5 LV at 12 minutes process time. Then anodic oxidation was performed by using 180 g / L sulfuric acid (H2SO4) and 18 volt (V). Surface morphology of the final aluminium profiles were examined with SEM analysis, Roughness, Gloss and Thickness tests.

Experimental analysis of surface finishing properties in Magnetically Assisted Abrasive Finishing of ASTM B16 Brass

Magnetically assisted abrasive finishing (MAAF) presents an attractive concept of surface and edge finishing by fine magnetic abrasive particles (MAPs). This study aims to contribute an experimental evaluation of the effect of process parameters viz. magnetic field density (MFD), circumferential speed of workpiece, and abrasive grit size on the surface finishing properties in MAAF when experiments were performed for finishing pipes of ASTM B16 brass material with the sintered MAPs. The developed model is based on the obtained experimental data accompanied by “Box- Behnken design (BBD) of response surface methodology (RSM)” analysis. Apart from deciding significant parameters, this analysis also presents the modeling of finishing properties and optimizes the desired performance parameters. Analysis of variance (ANOVA) includes data of standard deviation, coefficient of determination (R2), adjusted, and predicted (R2). MFD and speed show a significant effect on both the responses viz. “surface roughness improvement rate (SRIR) and material removal rate (MRR)”. Analysis has shown that abrasive grit size is the most dominant parameter towards SRIR followed by MFD. The maximum SRIR of 88.12% (minimum Ra 50 nm) and 4.28 mg/min is achieved through multi-objective optimization with 0.8 T MFD, 500 rpm speed, and 300 µm grit size. The mathematical models of SRIR and MRR were also developed using RSM, focusing on varying MFD, speed, and grit size which can be used to predict the desired surface finishing properties. The model generated for SRIR, and MRR has an error of 0.204 % and 2.506 % respectively. Further SEM images were taken to understand the surface appearance of the finished surface.

Electrochemical Polishing of 7075 Al Alloy in Phosphoric Acid

7075 aluminum (Al) alloy has been widely used in aircraft structures and other high-end electronic products owing to its excellent mechanical and chemical properties, while its damage-free and highly efficient surface finishing remains a challenge. Herein, we demonstrate a systematic study of the anodic behaviors of 7075 Al alloy during the electrochemical polishing (ECP) process in phosphoric acid under different applied potentials, and the changes of surface morphology, roughness, electric current and resistance are studied intensively. According to the surface morphology and current density, ECP of 7075 Al can be divided into 4 stages including the negative leveling stage, leveling and corrosion stage, levelling and brightening stage, and pitting and corrosion stage. Different factors influencing each stage and the effects of impurity phases in the ECP process are experimentally validated. Under optimized conditions, a mirror surface with a roughness (Ra) of 46.7 nm (decreased from an initial value of 153.2 nm) can be obtained by ECP for 10 min. The presented findings are of great value for the further development of ECP process of multiphase alloys.