arXiv subjects

Nagaraj Nandihalli

Publications and source records attributed to Nagaraj Nandihalli.

4 recordsLinked to original sources

arXiv2025

Microwave-driven synthesis and modification of nanocarbons and hybrids in liquid and solid phases

Over the past 20 years, nanocarbons have become more significant as nanostructured fillers in composites and, more recently, as functional elements in a brand-new class of hybrid materials. Microwave-assisted synthesis and processing is a burgeoning subject matter in materials research with significant strides in the realm of nanocarbon during the last decade. The review examines recent approaches to producing various nanocarbons using microwaves as energy sources, the characterization of such materials for various applications, and their results. The underlying factors supporting the increased performance of such materials or their composites are analyzed and reaction mechanisms are presented wherever necessary. In particular, the recently developed and verified approaches to produce porous carbon materials, CNTs and fibers, carbon nanospheres, carbon dots, CQDs, reduced graphene oxide, nanocarbon hybrid materials, and the purification and modification of CNTs are discussed. The reduction of graphene oxide and the preparation of graphene derivative hybrids using solid-state and liquid-state routes such as polyopl, mixed solvents, ionic liquids, and microwave-assisted hydrothermal/solvothermal methods are analyzed in detail. In addition, the principles of microwave heating in liquid and solid states, the use of metals particles as arcing agents or catalysts, and carbonaceous materials as internal or external susceptors during synthesis and modifications are presented in detail.

cond-mat.mtrl-sci↗

arXiv2024

A short account of thermoelectric film characterization techniques

Thermoelectric films and periodic structures have particularly intriguing electrical and thermal transport features due to their low dimensionality. As a result, they have piqued the attention of researchers from across the spectrum of disciplines. Their applications span from cooling fast CPUs to providing energy for wearable devices. The progress in the techniques for synthesizing TE materials and fabricating thin films has facilitated the emergence of a flourishing research domain in the field of electrical and thermal transport at the nanoscale. Further, a significant proportion of contemporary electronic, opto-electronic, and solar energy components are composed of materials featuring numerous interfaces and nanoscale contacts. Consequently, it is imperative to explore the thermal energy transfer and charge carrier transport across the films with thickness dimensions in the nanometer range. The development of cutting-edge approaches for grasping complicated processes at the nanoscale is critical. This review provides a concise overview of the prevalent methodologies developed over the last two decades and employed for the characterization of the Seebeck coefficient and electrical and thermal conductivity of thermoelectric films.

cond-mat.mtrl-sci↗

arXiv2024

Performance analysis of photodetectors based on 2D materials and heterostructures

The unprecedented demand for sophisticated, self-powered, compact, ultrafast, cost-effective, and broadband light sensors for a myriad of applications has spurred a lot of research, precipitating in a slew of studies over the last decade. Apart from the photosensing ability of an active element in the light sensor, the device architecture is crucial in terms of photoinduced charge carrier generation and separation. Since the inception of graphene and the subsequent research growth in the atomically thin 2D materials, researchers have developed and adapted different families of 2D materials and device architectures, including single element 2D, 0D/2D, 2D/2D, 1D/ 2D stacked structures, and so on. This review discusses the recent reports on the light-sensing properties of various 2D materials, their heterostructures, and characteristics applicable to the ultraviolet-near infrared (UV-NIR), short-wave IR (SWIR), mid-wave IR (MWIR), long-wave IR (LWIR), and terahertz (THz) spectral ranges. It highlights the novelty of the burgeoning field, the heightened activity at the boundaries of engineering and materials science, particularly in the generation of charge carriers, their separation, and extraction, and the increased understanding of the underpinning science through modern experimental approaches. Devices based on the simultaneous effects of the pyro-phototronic effect (PPE) and the localized surface plasmon resonance (LSPR) effect, the photothermoelectric effect (PTE)-assisted photodetectors (PDs), waveguide-integrated silicon-2D PDs, metal-2D-metal PDs, and organic material PDs are examined rigorously. Theoretical treatment utilizing various computational approaches to investigate 2D materials and heterostructures for photodetection applications is also briefly discussed.

physics.app-ph↗

arXiv2021

Thermoelectric films and periodic structures and spin Seebeck effect systems: Facets of performance optimization

The growing market for sensors, internet of things, and wearable devices is fueling the development of low-cost energy-harvesting materials and systems. Film based thermoelectric (TE) devices offer the ability to address the energy requirements by using ubiquitously available waste-heat. This review narrates recent advancements in fabricating high-performance TE films and superlattice structures, from the aspects of microstructure control, doping, defects, composition, surface roughness, substrate effect, interface control, nanocompositing, and crystal preferred orientation realized by regulating various deposition parameters and subsequent heat treatment. The review begins with a brief account of heat conduction mechanism, quantum confinement effect in periodic layers, film deposition processes, thin film configurations and design consideration for TE in-plane devices, and characterization techniques. It then proceeds to alayzing the latest findingd on the TE properties of Bi2(Te,Se)3 and (Bi,Sb)2Te3, PbTe, GeTe, SnSe, SnTe, Cu2-xSe, and skutterudite films, including superlattices and the performance of TE generators, sensors, and cooling devices. Thickness dependent microstructure evolution and TE characteristics of films in relation to temperature are also analyzed. In the context of spin Seebeck effect (SSE) based systems, SSE mechanism analysis, developments in enhancing the spin Seebeck signal since its first observation, and recent developments are covered from the facets of new system design, signal collection, magnetic manipulation, interface conditions, thickness-dependent longitudinal spin Seebeck signal, and length scale of phonon and magnon transport in longitudinal SSE (LSSE) in different bi-layer systems. At the end, possible strategies for further enhancing zT of TE films and spin Seebeck signals of many systems are addressed.

physics.app-ph↗