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Investigation on thermal barrier effects of 8YPSZ coatings on Al-Si alloy and validation through simulation
In high temperature engineering field, protection of metal components operating at high temperatures has been a problem since the attempts to realize high efficiency aero engines in the 1940s. Researchers have been working on finding a solution for this issue and thermally insulating the surface of the base metal component with a suitable high temperature material, generally a ceramic, is one solution. The Thermal Barrier Coatings, popular worldwide as TBCs have found wide spread applications in aerospace and automobile industry after its successful application in aerospace engines in mid 1970s. In the field of aerospace, generally a super alloy will be the substrate and in automobile field this process is very much suited on aluminium casting alloys, which is the raw material for high speed diesel engine cylinder blocks and pistons. Although a good quantity of research work on TBCs have been completed in the field of aerospace, the published literature on such coatings on Aluminium castings alloys are limited. Present research aims to throw some light in this grey area by plasma spray coating Aluminium-Silicon (Al-Si) substrates with popular Yttria Partially Stabilized Zirconia as top coat and underlying nickel aluminide bond coat. Al-Si alloys are widely used in automobiles. Experiments were conducted to evaluate the temperature drop across a 250 mm thick TBC at different ceramic surface temperatures and then validating the experimental results by simulation in ANSYS. Experimental results and simulated results showed a close match, thereby validating the findings. 2019 Elsevier Ltd. All rights reserved. -
Residual stresses analysis on thermal barrier coatingsndt tool for condition assessment
Improvement in the engine efficiency follows reduction in fuel consumption which is possible by increasing the engine combustion temperature. Coating the piston of diesel engine with a high temperature-resistant material, known as thermal barrier coating, generally 68% Y2O3 stabilized ZrO2, is a popular method to reduce the temperature it experiences in service and to increase engine efficiency. Whether bare or coated component, fabrication and different thermal expansion coefficients of the ceramic coating and piston metal cause generation of residual stresses in them. These hidden residual stresses (tensile or compressive) play a significant role in governing the failure mechanism of the different sections of the components and their important role (also developed in service) is mostly neglected in engineering practices. Residual stresses analysis of components in service may throw light on the condition of the components without destroying them. In this work, portable X-ray residual stress analyzer was used to evaluate the condition of AlSi alloys piston flat plates that were coated with 250-m-thick 68% Y2O3 stabilized ZrO2 and subjected to thermal treatments. The analysis revealed (a) residual stress-free pattern for uncoated AlSi substrate, (b) compressive residual stress at the substrate (AlSi)coating (TBC) interface and (c) tensile residual stress at the substrate (AlSi)coating (TBC) interface of a thermal shocked coated substrate. The analysis method exhibited good possibility for using this as a tool for non-destructive testing for predicting the onset of failure at the coating substrate interface, without destroying the component in service. Springer Nature Singapore Pte Ltd 2020. -
Protection offered by thermal barrier coatings to Al-Si alloys at high temperatures - A microstructural investigation
Thermal barrier coatings, with ~50 mm thick Nickel-Aluminide bond coat and ~250 mm thick Yttria-Stabilized zirconia ceramic top coats were synthesized by Air Plasma Spray coating process on flat plates machined from Al-11Si alloy diesel engine pistons. Coating process parameters and qualifications that were followed were based on previous studies made on the same substrates. The ceramic coatings were subjected to various thermal treatments such as (a) thermal shock cycling tests and (b) continuous heating in a furnace. Uncoated Al-Si samples were simultaneously subjected to the same thermal treatments and used as reference to study the protection offered by the coatings to the base metal substrates. Thermal shock cycles tests involved subjecting the coated and uncoated Al-Si plates to oxy-acetylene flame to allow the ceramic surface to be maintained at 500 C for 1000 cycles (one cycle comprised of heating for 60 s, withdrawal from flame and forced cooling in ambient air for 60 s) and similar thermal shock cycles in an electric furnace. The specimen were also heated in a furnace at 300 C for 1000 continuous hours. Stresses induced during thermal shock cycles and oxidation of bond coat-ceramic coat interface during the exposure to heat are the main reasons for the coating's failure. Details of an investigation on the microstructural changes and oxidation behaviour of the substrate and the ability of the coatings to protect the metal substrates from oxidation are presented. Microstructural studies were carried out by employing a Scanning Electron Microscope attached with Energy Dispersive X-ray spectroscopy facility. The findings were compared on (a) uncoated Al-Si alloy and (b) thermal barrier coated Al-Si alloy with a goal to understand the capability of the coatings to protect the metal from the influences of thermal treatments, at temperatures lower than the melting point of the Al-Si alloy. 2019 Elsevier Ltd. All rights reserved. -
Thermal Barrier Coating Development on Automobile Piston Material (Al-Si alloy), Numerical Analysis and Validation
This work is focused on the thermal barrier coating (TBC) development on aluminium-silicon (Al-Si) alloy casting materials, widely used as automobile components (cylinder blocks, pistons etc.). TBCs enable enhanced combustion within the chambers of diesel engines resulting in improved performance and components life. Uniform coating thickness development on complex contours of automobile pistons is a challenging task worldwide which results in varying thermal barrier characteristics across the non-uniform thickness. In consistent (in thickness) coatings are most likely to lead to uneven thermal barrier effects across the TBC thicknesses which directly affect the performance and the lubrication system of the engine. This warrants the development of stable and consistently thick coatings for ideal performance of the Low Heat rejection (LHR) engine. The present research work involved building different thicknesses (100, 125 and 150?m) of commercial 6-8%Yttria stabilized zirconia (YSZ) TBCs on 50? to 75? thick nickel aluminide (NiAl) bond coat. The influence of thickness on thermal barrier characteristics via experimentation and numerical analysis has been studied. Flat plates machined from automobile pistons were used as substrates. The coatings were characterized for thermal barrier effects for hot ceramic surface face temperatures up to 550C (by using oxy-acetylene flame to heat up the TBC surface), structural phase analysis by X-ray Diffraction (XRD) and microstructure analysis in metallographic cross section by employing Scanning Electron Microscope (SEM). An analytical investigation also was carried out to determine the approximate temperature at each interface. A code was developed to calculate the temperature drops across the coated plate and the net heat available at the coated surface using MATLAB. This is important considering the effects, small changes in temperatures will bring on the creep life on the metal. 2019 Elsevier Ltd. -
Comparative experimental study of base line and thermal barrier coated four stroke four cylinder diesel fueled engine with low heat rejection
The depletion of conventional fuel source at a fast rate and increasing of environment pollution motivated extensive research in energy efficient engine design. In the present work, experimental investigations were carried out on a four-stroke four-cylinder diesel-fuelled Base Line Engine (BLE) by conducting a normal load test and measuring the required Brake Thermal Efficiency (BThE) and Specific Fuel Consumption (SFC) in a 100 HP dyno facility. A six-gas Analyser was used for the measurement of Unburnt Hydrocarbons (UBHC), Carbon monoxide (CO), Carbon dioxide (CO2), free Oxygen (O2), Nitrogen oxides (NOx), Sulphur oxides (SOx) and a smoke meter was used to measure smoke opacity. Low Heat Rejection (LHR) engine was realized by coating the crown of the aluminium alloy piston with the most popular Thermal Barrier Coating (TBC) material, namely 8%Yttria Partially Stabilized Zirconia (8YPSZ), after coating qualification on research pistons, specifically fabricated to retain the piston material specification, and the geometry of the crown contour. A normal load test was conducted on LHR engine to evaluate the performance as well as to determine the concentration of pollutants. A ~30% improvement in BThE and ~35% improvement in SFC was exhibited by the LHR engine at all loads studied (7 to 64%). While UBHC level showed an increase, the CO, CO2 and O2 contents as revealed in the emission test showed a mixed response (high and low) for an LHR engine. Compared with BLE, NOx and smoke level in LHR engine emission showed an increasing trend with the load. On comparing BLE and LHR engine test results, value addition to the BLE in terms of reduced fuel consumption and pollutants was observed. Universiti Malaysia Pahang, Malaysia. -
Assessment of thermal barrier effects across 8%Y2O3-ZrO2 coatings on Al-Si substrates via electrical heating source
Ceramic Thermal Barrier Coatings (TBCs) provide protection to metals from degradation at high temperature. A major factor deciding the effectiveness of the coating in service is the temperature drop across the thickness of the coating. Common practice to determine the temperature drop is to subject the coating with a high heat providing flame with preset velocity by using combustible gases focused towards the coated surface, that keep the surface at desired stabilization temperature and the temperature is measured at the back side of the coating, i.e. at the metal side. The challenge is to heat the complete specimen surface using the flame and to reach an accurate stabilization temperature by using the flame as the heating source. In the present work, this challenge was overcome by using a uniform source of heat i.e. an electric heater on the entire coating surface. This paper presents the results obtained by studying the thermal barrier effects across TBCs by using the electrical heating source that provided the heat on the ceramic surface in a controlled and uniform manner, thereby establishing a newer assessment method. The TBCs were prepared by plasma spray coating commercial 8%Yttria-Stabilized Zirconia (8YSZ) as the top ceramic coat on flat plates of Aluminium 11% Silicon alloy removed from diesel engine pistons. TBC thicknesses varied between 100?m and 600?m. Air Plasma Spray coating was employed to coat the substrates which initially were spray coated with 50-75 ?m thick bond coat of Nickel Aluminide. Thermal barrier test was conducted by heating the entire coated surface uniformly and by keeping the ceramic surface temperature constant till the stabilization in the range of 300C to 500C. The temperature drop achieved was in the range of 46C to 127C depending upon the coating thickness. Details of the tests conducted and results obtained are presented. 2019 Author(s). -
Challenges in Plasma Spraying of 8%Y2O3-ZrO2 Thermal Barrier Coatings on Al Alloy Automotive Piston and Influence of Vibration and Thermal Fatigue on Coating Characteristics
Although Thermal Barrier Coatings (TBCs) have found extensive application in automotive engines to enhance performance and to reduce fuel consumption and pollution, challenges of obtaining uniform and consistent coatings on non-uniform and irregularly shaped components are overcome only when the coatings are deposited via robot controlled APS or EBPVD. Atmospheric Plasma Spraying (APS) is the most commonly used and relatively cost-effective method to make TBCs: but not all APS facilities are equipped with comprehensive coating accessories. In a reciprocating diesel engine, the bowl at the piston crown forms one side of the combustion chamber and includes the space between piston crown (generally 9% Si-Al alloy in light - medium duty diesel fuel vehicle) and cylinder head. To achieve maximum effective fuel spray distribution and combustion, normally the crown of the piston has complex contours. One of the many service related parameters to be monitored to reduce the innumerable faults contributing to the performance of the engine is vibration. This paper addresses the issue related with the challenges associated with the plasma spraying of consistent and adherent TBC on Al-9% Si research pistons and its complex contours by APS, subjecting the coated pistons to thermal fatigue tests and evaluation of the coating characteristics after subjecting to vibration. 2018 Elsevier Ltd. -
Populist Protests and the Dynamic Zero-COVID Policy: (Re)emerging Pragmatic Populism in China
Populist protests in the Peoples Republic of China (PRC) have recently emerged as a reaction against the Chinese authorities stringent measures under its dynamic zero-COVID policy. Besides the vehement criticism and protests against the dynamic zero-COVID policy, during some protests, there have been ensuing calls across the country for President Xi Jinping to step down. The article argues that this scenario can further deteriorate the overall political legitimacy of the Communist Party of China on a long-term basis. According to the article, the protests indicate the re-emergence of populism in the PRC, which incidentally and historically has parallels to the protests at Tiananmen Square, and the 1919 May Fourth Movement. The article theorizes John Deweys concept of pragmatic populism and the aspect of protests during the period, which inherently provides many ideational and relational facets with the recent protests in China. 2023 Jawaharlal Nehru University. -
Manipur: the British legacy
[No abstract available] -
THE GREAT RESET AND THE NEARTERM IMPLICATIONS FOR THE CHINESE ECONOMY: A POST PANDEMIC OUTLOOK
The Great Reset has had a severe impact on the Chinese economy, with implications domestically, and on the global supply chain. One consequence has been the decline in the overall market demand in China, with a significant negative impact on infrastructure development and the labour industry. A unique aspect is a survey is to analyze the impact of COVID-19 on innovation and integration of digital technologies in China. The authors analyse the impact of the Great Reset on the Chinese economy, the implications on the supply chains that China is a crucial part of, and the global implications thereof. (2023), (Universidade Federal do Rio Grande do Sul). All Rights Reserved. -
Hierarchical BiFeO3/Cr2CTx MXene composite as a multifunctional catalyst for hydrogen evolution reaction and as an electrode material for energy storage devices
A multifunctional hierarchical Bismuth ferrite/chromium carbide (BiFeO3/Cr2CTx) MXene has been employed as both electrode material for supercapacitors as well as an electrocatalyst for electrocatalytic water splitting. Here, a facile method is suggested for synthesizing Cr2CTx MXene from the chromium aluminum carbide (Cr2AlC) MAX Phase. X-ray diffraction studies, Scanning electron microscopy, and high-resolution transmission electron microscopy indicate that the aluminum atomic layers are removed from Cr2AlC MAX structure. The electrochemical test reveals that the BiFeO3/Cr2CTx MXene composite, which is produced with less Al2O3, performs well in the hydrogen evolution reaction (HER) with a low overpotential of 128 mV in 1 M potassium hydroxide. 53.3 mV dec?1, and 0.16 ? cm?2, respectively, are the values of the calculated Tafel slope and charge transfer resistance. In a dielectrode electrolysis system, BiFeO3/Cr2CTx MXene electrode needs only 1.81 V of cell potential to provide 10 mA cm?2 with long-term stability. The specific capacity of 671.2 C g?1 at a current density of 1 A g?1 is obtained for BiFeO3/Cr2CTx MXene electrode with 90% capacitance retention after 3000 cycles. The potential use of BiFeO3/Cr2CTx MXene towards HER and supercapacitor application is demonstrated by this study, which offers a gentle path for the fabrication of Cr2CTx MXene composites for energy storage and HER applications. 2023 Elsevier Ltd -
N-doped graphene quantum dots incorporated cobalt ferrite/graphitic carbon nitride ternary composite for electrochemical overall water splitting
Multicomponent electrocatalysts containing carbon supports play a crucial role in influencing the hydrogen and oxygen evolution reactions which enhance the total water splitting. Herein, we report a ternary composite with cobalt ferrite, graphitic carbon nitride, and N-doped graphene quantum dots prepared via hydrothermal technique. The purity of the samples is established by carrying out various characterization methods. The intrinsic characteristics of the obtained materials are investigated by employing electrocatalytic processes in an alkaline media toward hydrogen and oxygen evolution reactions. Cobalt ferrite/graphitic carbon nitride/N doped graphene quantum dots electrocatalyst demonstrates a very low overpotential towards hydrogen evolution reaction of 287 mV at a constant 10 mA cm?2 current density in 1.0 M KOH. Tafel slope and Rct values generated are 94 mV dec?1 and 0.86 cm2, respectively. Oxygen evolution reaction studies reveal an overpotential of 445 mV at 10 mA cm?2 with a Tafel slope of 69 mV dec?1. Finally, the cell potential needed for the cobalt ferrite/graphitic carbon nitride/N doped graphene quantum dots electrode to achieve 10 mA cm?2 in total water splitting is only 2.0 V while displaying long-term stability. 2022 Hydrogen Energy Publications LLC -
Two-dimensional Ti3C2 MXene for photocatalytic hydrogen production: A review
This study focuses on the utilization of two-dimensional Ti3C2 MXene as a catalyst for photocatalytic hydrogen production. MXenes, a class of transition metal carbides/nitrides, exhibit exceptional properties conducive to enhancing photocatalytic reactions. This research explores the performance of Ti3C2 MXene as a cocatalyst in photocatalytic systems, aiming to improve charge separation, inhibit recombination, and facilitate efficient hydrogen evolution from water under light irradiation. The synthesis methods, catalyst-loading strategies, and overall photocatalytic mechanisms are investigated, shedding light on the potential of Ti3C2 MXene as a promising material for advancing hydrogen production through sustainable means. 2023 Korean Chemical Society, Seoul & Wiley-VCH GmbH. -
Advances in the use of ceramic catalysts in fine chemical synthesis
Ceramics are versatile materials that have been put to many different uses. Catalysis is one such area where they have been used, both as catalyst and as a robust support material for catalysts. Properties like porosity and thermal and mechanical stability make ceramics attractive in these applications. Oxidation, esterification, hydrogenation, reduction, condensation reaction, and FriedelCrafts reaction are important reactions, which have uses spanning a wide range of applications, most notably in energy and environment. This chapter gives the recent advancements in ceramic materials used in the synthetic applications of the abovementioned reactions. The type and class of the ceramic material used and its role have been mentioned for these reactions. 2023 Elsevier Ltd. All rights reserved. -
CoFe2O4 nanoparticles embedded 2D Cr2CTx MXene: A new material for battery like hybrid supercapacitors and oxygen evolution reaction
The progress of effective electrode materials for high-performance supercapacitors is one of the most cutting-edge fields of study in the search for alternative and renewable energy uses. 2D MXenes, with their distinctive physiochemical features, have successfully improved the electrode materials by imparting superior energy storage, thus distinguishing themselves among electrode materials. A new class of cobalt ferrite nanoparticles embedded Cr2CTx MXene sheets have been fabricated and tested for supercapacitor applications. Notably, the cobalt ferrite acts as interlayer spacers between Cr2CTx MXene layers. The Cobalt ferrite/Cr2CTx MXene composite offers enhanced supercapacitive features compared to pristine cobalt ferrite or Cr2CTx MXene sheets. The cobalt ferrite/Cr2CTx MXene nanocomposite shows a maximal specific capacity of 763.83C g?1 (1909.6 F g?1) at 1 A g?1. The fabricated device using the prepared material exhibited a capacitance retention of 99 % up to 2500 cycles. Also, this attractive nanocomposite displays a charge transfer resistance of only 0.25 ?, which is highly beneficial to charge-discharge at higher current rates. 2024 Elsevier Ltd -
A review of hierarchical nanostructures of TiO2: Advances and applications
In the past few decades, extensive studies have been carried out on TiO2 nanostructures having hierarchical morphologies and their applications in diverse fields. By controlling the size and composition of the different TiO2 morphologies, new and improved properties have been realized, leading to significant advancements in materials chemistry, in the broad areas of energy and environment. The improved efficiency and wide applications of these materials are attributed to their physicochemical properties such as stability, efficient electronic and ionic charge transfer, higher specific surface area, etc. In this review, we discuss the different morphologies of hierarchical TiO2 nanoparticles and the properties that have been influenced by these morphologies, enabling their diverse applications. Several composites using the different TiO2 hierarchical forms have been synthesized which too find wide applications. The excellent physical properties of zero, one, two, and three-dimensional TiO2 nanostructures, the relationship between the morphologies of TiO2 nanostructures, and their activities in energy and environment applications have been discussed. 2021 The Author(s) -
Synthesis of Carbon Containing Composites for Energy and Environmental Applications
The population has grown rapidly, resulting in increased energy consumption and environmental issues. Researchers are developing new materials with unique physical and chemical properties to tackle these challenges. This has led to a focus on exploring novel approaches to synthesize micro and nanomaterials for use in the energy and environmental sectors. In this study, carbon-containing catalysts were developed as photocatalysts, electrocatalysts for water splitting reactions, and electrode materials for supercapacitor application. To evaluate the physicochemical characteristics of these materials, various characterization methods were employed, including X-ray diffraction, newlineScanning Electron Microscopy, Energy Dispersive X-ray Spectrometry, X-Ray Photoelectron Spectroscopy, High-resolution Transmission electron microscopy, Fourier Transform Infrared Spectroscopy, Differential reflectance spectroscopy, Dynamic light scattering, and Thermogravimetric analysis. The electrochemical and photocatalytic studies of the prepared materials were carried out by optimizing the different parameters. The four chapters include newlineCr2AlC MAX Phase as the catalyst used for photocatalysis, bismuth ferrite/Cr2CTx MXene, cobalt ferrite/Cr2CTx MXene composites for supercapacitor and electrocatalytic water splitting, bismuth ferrite/graphitic carbon nitride/N-doped graphene quantum dots for supercapacitor application, and Cobalt ferrite/graphitic carbon nitride/N-doped graphene quantum dots for supercapacitor and newlineelectrocatalytic water splitting application. -
Advanced Approaches for Hate Speech Detection: A Machine and Deep Learning Investigation
The prevalence of online social media platforms has led to an alarming rise in the frequency of cyberbullying and hate speech. This study uses a variety of machine-learning approaches and deep- learning algorithms to identify hate speech. The goal is to create a thorough and successful method for locating and categorizing hate speech on online networks. Our suggested approach intends to deliver a comprehensive solution to address the urgent problem of cyberbullying and hate speech in the digital sphere by leveraging the strength of these cutting-edge techniques. We work to make social media users' online experiences safer and more welcoming by identifying and addressing such harmful online actions. Through rigorous experimentation, we evaluate the efficacy of these methodologies, ultimately revealing that the Bidirectional Gated Recurrent Unit (Bi-GRU) outperforms the other employed techniques. The Bi-GRU model demonstrates superior hate speech detection capabilities, substantiated by robust performance metrics. This research contributes to the field by providing empirical evidence that deep learning models, such as Bi-GRU, can significantly advance hate speech detection accuracy. The findings underscore the potential of leveraging advanced neural architectures in the pursuit of fostering a more inclusive and respectful digital space. 2024 IEEE. -
Facial Expression Recognition Using Pre-trained Architectures
In the area of computer vision, one of the most difficult and challenging tasks is facial emotion recognition. Facial expression recognition (FER) stands out as a pivotal focus within computer vision research, with applications in various domains such as emotion analysis, mental health assessment, and humancomputer interaction. In this study, we explore the effectiveness of ensemble methods that combine pre-trained deep learning architectures, specifically AlexNet, ResNet50, and Inception V3, to enhance FER performance on the FER2013 dataset. The results from this study offer insights into the potential advantages of ensemble-based approaches for FER, demonstrating that combining pre-trained architectures can yield superior recognition outcomes. 2024 by the authors. -
Machine Learning-Based Classification of Autism Spectrum Disorder across Age Groups
Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition that has gained significant attention in recent years due to its increasing prevalence and profound impact on individuals, families, and society as a whole. In this study, we explore the use of different machine learning classifiers for the accurate detection of ASD in children, adolescents, and adults. Furthermore, we conduct feature reduction to identify key features contributing to ASD classification within each age group using Cuckoo Search Algorithm. Logistic Regression has the highest accuracy compared to the other two models. 2024 by the authors.