Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Equal channel angular processing-a modern deforming technique for quality products(Elsevier, 2021) Bhat K, U.K.; Bhat Panemangalore, D.B.; Bhat, S.The grain size plays a significant role in determining the mechanical properties of the materials. Decreasing grain size increases strength, toughness, and ductility. Due to these, a lot of research has been executed to develop deforming techniques to produce ultrafine-grained materials. Among several plastic deformation techniques available, equal channel angular pressing or processing (ECAP) produces ultra-fine grained materials with substantial amount of high angle grain boundaries. ECAP produces ultra-fine grained material with typical substructural features, which are difficult to achieve using other severe deformation techniques. This chapter presents characteristics, variables, die design, and die materials employed in the process. The chapter also presents recent developments in the domain, such as, use of finite element techniques, etc. © 2021 Elsevier Inc. All rights reserved.Item Microelectronic materials, microfabrication processes, micromechanical structural configuration based stiffness evaluation in MEMS: A review(Elsevier B.V., 2022) Manvi, M.; Mruthyunjaya Swamy, K.B.Microsystem or micro-electro-mechanical system (MEMS) is a revolutionary enabling technology, that is responsible for many of the technological advancements over the past few decades. Many such microsystems consist of suspensions mostly in the form of microcantilevers which are intended to perform desired function by detecting the changes in cantilever bending or vibrational frequency. The bending or deflection of the cantilever beam critically depends upon the mechanical properties, like stiffness, which is contingent on the type of materials, fabrication processes, and structural configurations. This paper evaluates cantilever stiffness of different MEMS devices in relation to aforesaid aspects. Common microelectronic materials like silicon, silicon dioxide, silicon nitride, gold, polymers etc. were seen to provide stiffness ranging from 0.012 N/m to 319.74 N/m that is influenced by elastic modulus & density for a given design. Likewise, fabrication process was seen to affect stiffness through process temperature & residual stress effects for different materials. Also, the structural shape geometry was observed to influence the same due to modified cross-sectional areas and straight & folded spring configurations. In this review, light is shed on abovementioned parameters which are found to be crucial in designing efficient MEMS devices and structures. © 2022 Elsevier B.V.Item An investigation on photophysical and third–order nonlinear optical properties of novel thermally–stable thiophene–imidazo [2,1-b][1,3,4] thiadiazole based azomethines(Elsevier Ltd, 2019) Kakekochi, V.; Udayakumar, U.; Nikhil, N.P.; Chandrasekharan, K.The use of ?–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto–electronic properties. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1–TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1–TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z–scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (?eff) of the order of 10?10 m W?1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the ?–conjugation, providing an improved ?eff (0.81 × 10?10 m W?1) to TI1 compared to that of TI2 (0.55 × 10?10 m W?1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices. © 2019 Elsevier LtdItem Impact of donor–acceptor alternation on optical power limiting behavior of H–Shaped thiophene–imidazo[2,1-b] [1,3,4]thiadiazole flanked conjugated oligomers(Elsevier Ltd, 2020) Kakekochi, V.; Nikhil, P.; Chandrasekharan, K.; Udayakumar, U.A new series of four D–A–D configured conjugated oligomers with H–type structure, possessing two thiophene–imidazo [2,1-b][1,3,4]thiadiazole branches and thiophene (TIT), thiophene–1,3,4-oxadiazole–thiophene (TITO), thiazolo [5,4-d]thiazole (TITz), phenyl–thiazolo [5,4-d]thiazole–phenyl (TIPTz) units as central core moieties were efficiently synthesized. These core moieties were specifically selected to increase the planarity, rigidity, stability, extend the ?–conjugation and to understand the influence of central core on nonlinear absorption coefficient (?eff) and optical limiting behavior of the synthesized oligomers. The structure-property relationships of these oligomers were established by the optical absorption (UV–Vis), electrochemical (CV) and theoretical (DFT) studies. The “effective two–photon absorption” of oligomers was confirmed by single–beam Z–scan analysis. The exceptional increase in nonlinear response was achieved with the oligomers TITO and TIPTz with nonlinear absorption coefficient (?eff) of 1.62 and 2.71 × 10?10 m W?1, and limiting thresholds of 6.02 and 3.14 J cm?2, respectively, which suggest that these oligomers could be potent materials for practical applications in laser photonics. © 2020 Elsevier Ltd