Electro-Discharge Machining of Zr67Cu11Ni10Ti9Be3: An Investigation on Hydroxyapatite Deposition and Surface Roughness

This study attempts to simultaneously machine and synthesize a biomimetic nanoporous hydroxyapatite coating on the Zr67Cu11Ni10Ti9Be3 bulk metallic glass (BMG) surface. The aim is to investigate and optimize the hydroxyapatite deposition rate and the surface roughness during the electro-discharge coating of Zr67Cu11Ni10Ti9Be3 BMG. Scanning Electron Microscopy (SEM), X-ray powder Diffraction (XRD) and Energy-dispersive X-ray Spectroscopy (EDS) were employed to characterize and analyze the results. Response Surface Methodology using D-optimum custom design approach was utilized to generate the models and optimize the input parameters. A globule nanostructured and nanoporous coating of about 25.2 µm thick, containing mainly Ca, O, and K were ascertained. Further XRD analysis confirmed the deposition of biocompatible oxides (HA, CaZrO3, and ZrO2) and hard ZrC coating on the Zr67Cu11Ni10Ti9Be3 BMG surface. A significant improvement in cell viability was observed in the HA electro-discharge coated BMG specimens. The numerical models for the Hydroxyapatite Deposition Rate (HDR) and Surface Roughness (SR) were developed and experimentally validated using the optimized parameters setting suggested by the software. The achieved average predicted error of 4.94 and 5.09% for the HDR and SR respectively confirmed the excellent reproducibility of the developed models

Investigation of Coatings, Corrosion and Wear Characteristics of Machined Biomaterials through Hydroxyapatite Mixed-EDM Process: A Review

Together, 316L steel, magnesium-alloy, Ni-Ti, titanium-alloy, and cobalt-alloy are commonly employed biomaterials for biomedical applications due to their excellent mechanical characteristics and resistance to corrosion, even though at times they can be incompatible with the body. This is attributed to their poor biofunction, whereby they tend to release contaminants from their attenuated surfaces. Coating of the surface is therefore required to mitigate the release of contaminants. The coating of biomaterials can be achieved through either physical or chemical deposition techniques. However, a newly developed manufacturing process, known as powder mixed-electro discharge machining (PM-EDM), is enabling these biomaterials to be concurrently machined and coated. Thermoelectrical processes allow the migration and removal of the materials from the machined surface caused by melting and chemical reactions during the machining. Hydroxyapatite powder (HAp), yielding Ca, P, and O, is widely used to form biocompatible coatings. The HAp added-EDM process has been reported to significantly improve the coating properties, corrosion, and wear resistance, and biofunctions of biomaterials. This article extensively explores the current development of bio-coatings and the wear and corrosion characteristics of biomaterials through the HAp mixed-EDM process, including the importance of these for biomaterial performance. This review presents a comparative analysis of machined surface properties using the existing deposition methods and the EDM technique employing HAp. The dominance of the process factors over the performance is discussed thoroughly. This study also discusses challenges and areas for future research

A comprehensive assessment of laser welding of biomedical devices and implant materials: recent research, development and applications

This review comprehensively covers the research accomplished in the field of laser welding of biomedical devices and implant materials. Laser welding technology in the recent past has been envisaged for numerous biomedical applications encompassing the reconstruction, fabrication, joining and sealing of the implanted biomaterials. It is the most studied and an increasingly applied manufacturing technology that garners the distinct advantages of smaller beam diameters leading to minimal thermal cycles that reduce the size of heat affected zone and instigate microstructural refinement. This paper presents a detailed critical review of similar and dissimilar welding of titanium alloys, cobalt-chromium alloys, steel, bulk metallic glasses and polymer-based biomaterials. Mechanical properties of the welded joints such as fatigue load, tensile and flexural strength, elongation, hardness and modulus of elasticity are discussed. The effect of laser processing parameters on microstructural features and the corresponding metallurgical defects encountered such as cracks, porosities, voids or the loss of alloying elements are reviewed. Furthermore, the corrosion behavior, cytotoxicity and biocompatibility of the welded implants in the simulated mediums are discussed. Furthermore, this article also summarizes the present-day applications associated with implant materials and is aimed at the further involvement of the laser precision technology in producing materials and joints with desired biomechanical characteristics. Lastly, the current research gaps on the role of laser welding of implants and the anticipated emerging fronts are summarized

A Critical Review on Physical Vapor Deposition Coatings Applied on Different Engine Components

Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented in the light of literature. It is revealed that PVD coating is significantly effective on wear resistance, scuffling resistance, surface roughness, and friction of the components in IC engine. Laboratory test and data from actual service so far suggest that the plasma-activated electron beam evaporation coating is perhaps one of the best choices for smooth surface finishing with improved mechanical and tribological properties. However, there are still some problems in its practical usage. This compressive review paper presents the major shortcomings of PVD coatings on IC engine components and the possible solutions if any. Finally, a number of issues have been reported which need to be encountered for further studies. © 2018 Taylor & Francis Group, LLC

Effect of antioxidants on the stability and corrosiveness of palm biodiesel upon exposure of different metals

The properties of biodiesel get aggravated when metals are exposed into it. The present study aims to investigate the effect of antioxidants on the fuel properties of palm biodiesel upon exposure to copper and mild steel. The used antioxidants include pyrogallol (PY) and butylated hydro-oxy toluene (BHT). Static immersion tests of metal coupons in palm biodiesel in the absence and presence (500 ppm) of antioxidants were conducted at room temperature (25˚C-27 °C) for 60 days. The investigated fuel properties include induction period, density, viscosity, acid number and calorific values. Results showed that pyrogallol was more effective to suppress the degradation of metal surface, fuel composition and fuel properties

Do digital students show an inclination toward continuous use of academic library applications? A case study

Rapid use of internet-based applications like mobile library applications (MLA) are depicting the modern era of digital students and literature broadly discussed the initial adoption of MLA among students. However, there is a need to investigate the continuance use intention of applications to overcome an acceptance-discontinuance phenomenon. Therefore, this research was performed for the empirical support toward continued usage of MLA by integrating an extended expectation confirmation model (EECM), technology acceptance model (TAM), media affinity theory, and service quality. This study worked on the focus of uncovering the factors which were creating hindrance in long term use of MLA. It was conducted with the self-controlled cross-sectional survey-based study. An overall 307 surveys were collected to verify the proposed theoretical model with structural equation modelling (SEM) technique. Finding of the study inferred that service quality, confirmation, MLA affinity, perceived usefulness, satisfaction and perceived ease of use are explaining the direct or indirect strong influence on continuous use of MLA. Current research empirically assessed to expose the deep intuition toward users' continuous usage intention of MLA. Outcomes will oblige as a controller for operative choices in development and resource distribution toward confirming the accomplishment of the mobile library application's mission and vision

Current research and development status of dissimilar materials laser welding of titanium and its alloys

Since its inception, laser beam welding as a high-quality fusion joining process has ascertained itself as an established and state of art technology exhibiting tremendous growth in a broad range of industries. This article provides a current state of understanding and detailed review of laser welding of titanium (Ti) alloys with corresponding dissimilar counterparts including steel, aluminium, magnesium, nickel, niobium, copper, etc. Particular emphasis is placed on the influence of critical processing parameters on the metallurgical features, tensile strength, hardness variation, percentage elongation and residual stress. Process modifications to improve dissimilar laser weldability by virtue of techniques such as laser offsetting, split beam, welding-brazing, hybrid welding and materials modifications by means of the introduction of single or multiple interlayers, fillers and pre-cut grooves are exploited. Detailed and comprehensive investigations on the phenomena governing the formation and distribution of the intermetallic phase, material flow mechanisms, their relations with laser parameters and their corresponding impact on the microstructural, geometrical and mechanical aspects of the welds are thoroughly examined. The critical issues related to the evolution of defects and the corresponding remedial measures applied are explored and the characteristics of fracture features reported in the literature are summarised in thematic tables. The purpose of this review is tantamount to emphasise the benefits and the growing trend of laser welding of Ti alloys in the academic sector to better exploit the process in the industry so that the applications are explored to a greater extent

Metamaterials subwavelength terahertz resonant cavities

Abstract One of the unique properties of metamaterials is the ability to manipulate electromagnetic waves at subwavelength scales, made possible by their structure on these scales. Here, rather than consider effective bulk properties, we consider the properties of microscopic features based on considering resonant unit cells. We used wire array metamaterials to form localized resonant cavities by changing the resonance frequency of one or more unit cells, surrounded by unchanged unit cells that do not support resonance for the propagating mode (i.e. forming a band gap). We validate our approach experimentally with electromagnetic waves in the terahertz range, demonstrating and characterizing subwavelength resonant cavities in this range. These resonant cavities can pave the way for ultra-compact subwavelength waveguides and other optical components

Metamaterials subwavelength terahertz resonant cavities

One of the unique properties of metamaterials is the ability to manipulate electromagnetic waves at subwavelength scales, made possible by their structure on these scales. Here, rather than consider effective bulk properties, we consider the properties of microscopic features based on considering resonant unit cells. We used wire array metamaterials to form localized resonant cavities by changing the resonance frequency of one or more unit cells, surrounded by unchanged unit cells that do not support resonance for the propagating mode (i.e. forming a band gap). We validate our approach experimentally with electromagnetic waves in the terahertz range, demonstrating and characterizing subwavelength resonant cavities in this range. These resonant cavities can pave the way for ultra-compact subwavelength waveguides and other optical components