Browsing by Author "Ramakrishna, S."

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3D printing of highly pure copper
(MDPI AG membranes@mdpi.com, 2019) Tran, T.Q.; Chinnappan, A.; Lee, J.K.Y.; Loc, N.H.; Tran, L.T.; Wang, G.; Vijay Kumar, V.V.; Jayathilaka, W.A.D.M.; Ji, D.; Doddamani, M.; Ramakrishna, S.
Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
Photo-electrochemical green-hydrogen generation: Fundamentals and recent developments
(Elsevier Ltd, 2024) Baiju, S.; Masuda, U.; Datta, S.; Tarefder, K.; Chaturvedi, J.; Ramakrishna, S.; Tripathi, L.N.
Scalable, cost-effective production and earth-abundant material platforms for clean energy sources such as green hydrogen are key research problems. Understanding the fundamentals is the basis of the advancement of research in green hydrogen production. Quantum materials such as two-dimensional materials are emerging material platforms for green-hydrogen generation. Quantum mechanical tools such as density functional theory play a crucial role in understanding quantum phenomena hence improving the efficiency of hydrogen production from the quantum materials. In this review article, we discuss the basic principles of green hydrogen generation using photo-electrochemical water splitting. The methods to evaluate the catalytic activity of the catalysts are discussed in detail. A broad classification of the photo/electro-catalysts for water splitting is further elaborated. We discuss methods to enhance the performance of the catalysts by doping the hetero-atoms, and the synergic effects of using other nanomaterials such as quantum dots and plasmonic nanostructures. The concept of electron transfer enhancement due to magnetic nanostructures is also discussed in detail. The introduction and application of surface plasmons for enhanced hydrogen generation are also discussed. Finally, we discuss the application of hydrogen in a fuel cell for the generation of electricity. © 2023 Hydrogen Energy Publications LLC
Processing of cenosphere/HDPE syntactic foams using an industrial scale polymer injection molding machine
(2016) Bharath, Kumar, B.R.; Doddamani, M.; Zeltmann, S.E.; Gupta, N.; Ramesh, M.R.; Ramakrishna, S.
Rapid production of high quality components is the key to cost reduction in industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in the injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components. 2015 Elsevier Ltd.
Processing of cenosphere/HDPE syntactic foams using an industrial scale polymer injection molding machine
(Elsevier Ltd, 2016) Bharath Kumar, B.R.; Doddamani, M.R.; Zeltmann, S.E.; Gupta, N.; Ramesh, M.R.; Ramakrishna, S.
Rapid production of high quality components is the key to cost reduction in industrial applications. The present work is the first attempt of manufacturing syntactic foams, hollow particle filled lightweight composites, using an industrial scale injection molding machine. High density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. Development of syntactic foams with cenospheres serves dual purpose of beneficial utilization of industrial waste fly ash and reduction in the cost of the component. The pressure and temperature used in the injection molding process are optimized to minimize fracture of cenospheres and obtain complete mixing of cenospheres with HDPE. The optimized parameters are used for manufacturing syntactic foams with 20, 40 and 60 wt.% cenospheres. With increasing cenosphere content, density and strength reduce and modulus increases. Surface modification of constituents results in rise in strength with increasing filler content. A theoretical model based on a differential scheme is used to estimate the properties of cenospheres by conducting parametric studies because of inherent difficulties in direct measurement of cenosphere properties. The potential for using the optimized injection molding process is demonstrated by casting several industrial components. © 2015 Elsevier Ltd.