Nagaraj Nandihalli, PhD | Ames Laboratory (original) (raw)

Papers by Nagaraj Nandihalli, PhD

Journal of Energy Storage, 2025

Over the past 20 years, nanocarbons have become more significant as nanostructured fillers in com... more 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 implanted
approaches to produce porous carbon materials, CNTs and fibers, carbon nanospheres, carbon dots, reduced graphene oxide, corresponding nanocarbon hybrid materials, and the purification and modification of CNTs are discussed. Finally, 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 or their particles as arcing agents or catalysts, and carbonaceous materials as internal or external susceptors during synthesis and modifications are presented in detail.

Critical Reviews in Solid State and Materials Sciences, Jan 10, 2024

Sustainability, 2024

Lithium (Li), a leading cathode material in rechargeable Li-ion batteries, is vital to modern ene... more Lithium (Li), a leading cathode material in rechargeable Li-ion batteries, is vital to modern energy storage technology, establishing it as one of the most impactful and strategical elements. Given the surge in the electric car market, it is crucial to improve lithium recovery from its rich
mineral deposits using the most effective extraction technique. In recent years, both industry and academia have shown significant interest in Li recovery from various Li-bearing minerals. Of these, only extraction from spodumene has established a reliable industrial production of Li salts. The
current approaches for cracking of the naturally occurring, stable α-spodumene structure into a more open structure—β-spodumene—involve the so-called decrepitation process that takes place at
extreme temperatures of ~1100 ◦C. This conversion is necessary, as β-spodumene is more susceptible to chemical attacks facilitating Li extraction. In the last several decades, many techniques have been
demonstrated and patented to process hard-rock mineral spodumene. The objective of this review is to present a thorough analysis of significant findings and the enhancement of process flowsheets over
time that can be useful for both research endeavors and industrial process improvements. The review focuses on the following techniques: acid methods, alkali methods, carbonate roasting/autoclaving
methods, sulfuric acid roasting/autoclaving methods, chlorinating methods, and mechanochemical activation. Recently, microwaves (MWs), as an energy source, have been employed to transform
α-spodumene into β-spodumene. Considering its energy-efficient and short-duration aspects, the review discusses the interaction mechanism of MWs with solids, MW-assisted decrepitation, and Li extraction efficiencies. Finally, the merits and/or disadvantages, challenges, and prospects of the
processes are summarized.

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Crystals, 2024

Renewable and non-renewable energy harvesting and its storage are important components of our eve... more Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their widespread use, improving LIBs’ performance, such as increasing energy density demand, stability, and safety, remains a significant problem. The anode is an important component in LIBs and determines battery performance. To achieve high-performance batteries, anode subsystems must have a high capacity for ion intercalation/adsorption, high efficiency during charging and discharging operations, minimal reactivity to the electrolyte, excellent cyclability, and non-toxic operation. Group IV elements (Si, Ge, and Sn), transition-metal oxides, nitrides, sulfides, and transition-metal carbonates have all been tested as LIB anode materials. However, these materials have low rate capability due to weak conductivity, dismal cyclability, and fast capacity fading owing to large volume expansion and severe electrode collapse during the cycle operations. Contrarily, carbon nanostructures (1D, 2D, and 3D) have the potential to be employed as anode materials for LIBs due to their large buffer space and Li-ion conductivity. However, their capacity is limited. Blending these two material types to create a conductive and flexible carbon supporting nanocomposite framework as an anode material for LIBs is regarded as one of the most beneficial techniques for improving stability, conductivity, and capacity. This review begins with a quick overview of LIB operations and performance measurement indexes. It then examines the recently reported synthesis methods of carbon-based nanostructured materials and the effects of their properties on high-performance anode materials for LIBs. These include composites made of 1D, 2D, and 3D nanocarbon structures and much higher Li storage-capacity nanostructured compounds (metals, transitional metal oxides, transition-metal sulfides, and other inorganic materials). The strategies employed to improve anode performance by leveraging the intrinsic features of individual constituents and their structural designs are examined. The review concludes with a summary and an outlook for future advancements in this research field.

Advanced Science, Jul 17, 2022

The pillars of Green Chemistry necessitate the development of new chemical methodologies and proc... more The pillars of Green Chemistry necessitate the development of new chemical methodologies and processes that can benefit chemical synthesis in terms of energy efficiency, conservation of resources, product selectivity, operational simplicity and, crucially, health, safety, and environmental impact. Implementation of green principles whenever possible can spur the growth of benign scientific technologies by considering environmental, economical, and societal sustainability in parallel. These principles seem especially important in the context of the manufacture of materials for sustainable energy and environmental applications. In this review, the production of energy conversion materials is taken as an exemplar, by examining the recent growth in the energy-efficient synthesis of thermoelectric nanomaterials for use in devices for thermal energy harvesting. Specifically, "soft chemistry" techniques such as solution-based, solvothermal, microwave-assisted, and mechanochemical (ball-milling) methods as viable and sustainable alternatives to processes performed at high temperature and/or pressure are focused. How some of these new approaches are also considered to thermoelectric materials fabrication can influence the properties and performance of the nanomaterials so-produced and the prospects of developing such techniques further.

Journal of Solid State Chemistry, 2013

Critical Reviews in Solid State and Materials Sciences, 2022

Materialia, 2020

Different contents of NaCl (2%, 4%, 6%, and 8 wt%) was incorporated in polycrystalline PbTe sampl... more Different contents of NaCl (2%, 4%, 6%, and 8 wt%) was incorporated in polycrystalline PbTe samples and consolidated via spark-plasma-sintering (SPS). NaCl acted as a dopant material during SPS. The effect of doping through NaCl increased the carrier concentration without deteriorating mobility. The incorporation of NaCl helped the formation of a porous structure which facilitated high rate of phonon scattering and decreased the thermal conductivity. Experimental observation suggests that the origin of electrical property is due to the extra carriers given by Na, and that Fermi level is well optimized by the compensation effect acquired by Cl doping. The energy barrier heights (EB) for charge carriers in PbTe/NaCl samples is lower than the EB of reference PbTe. High Seebeck coefficient of 300 µV/K at 773 K combined with the lower thermal conductivity of 0.55 W/m-K, yielded an improved figure-of-merit (zT) value as high as 1.2 at 773 K in a 6wt%NaCl:PbTe. In the PbTe/NaCl series, PbT...

The growing market for sensors, internet of things, and wearable devices is fueling the developme... more 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,S...

Ceramics International, 2020

A series of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites (y = 0, 0.04, 0.06, 0.08, and 0.11) was fabr... more A series of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites (y = 0, 0.04, 0.06, 0.08, and 0.11) was fabricated by hydrothermal synthesis of PbTe and Zn0.85Al0.15Te nanoparticles separately, followed by intimate mixing, pressing, and sintering in evacuated-and-encapsulated Pyrex ampoules at 380 °C for 12 h. Thermoelectric properties were characterized from 120-600 K. With increasing Zn content, the peak thermopower shifts to higher temperatures, Hall carrier concentration increases, and the lattice thermal conductivity decreases. As compared to the pristine PbTe, thermoelectric properties of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites have improved considerably. The y = 0.11 sample exhibits the highest zT ~1 comparable to the state-of-the-art p-type PbTe-based materials. The enhanced zT is ascribed to reduced thermal conductivity, elevated electrical conductivity and thermopower. This unique new method of material synthesis and doping is very promising to obtain high-performance thermoelectric...

Materials Chemistry and Physics

AIP Advances

Green laser sintering of copper oxide (CuO) nano particle (NP) film to form Cu conductive lines A... more Green laser sintering of copper oxide (CuO) nano particle (NP) film to form Cu conductive lines AIP Advances 8, 095008 (2018);

Journal of Alloys and Compounds

AIP Advances

NiSb nanoparticles by 0.034, 0.074 and 0.16 volume fractions were successfully coated on bulk pol... more NiSb nanoparticles by 0.034, 0.074 and 0.16 volume fractions were successfully coated on bulk polycrystalline Ni 0.05 Mo 3 Sb 5.4 Te 1.6 thermoelectric (TE) particles through a solvothermal route without deteriorating the bulk Ni 0.05 Mo 3 Sb 5.4 Te 1.6 material. The samples were consolidated through hot pressing and their thermoelectric (TE) properties were characterized. At 400 K, 500 K, and 600 K, 0.074 NiSb sample exhibited 22%, 16% and 11.3% increases in the power factor (P.F.) compared to bulk material. The main contributing factor to this enhanced power factor is the elevated electrical conductivity. For the same sample, the reciprocal relationship between Seebeck coefficient and electrical conductivity is decoupled. Sample 0.16 NiSb exhibited the highest electrical conductivity among the three samples. The thermal conductivity of the 0.16 sample was less temperature sensitive compared to other samples. HRTEM and SEM tools were applied to comprehend microstructural features and their relationship to TE transport properties. Pore effect on the thermal and electrical conductivity was elucidated. This study shows that grain-boundary manipulation via this wet chemistry technique is indeed an economically viable method to fabricate and optimize the transport properties of bulk TE materials.

European Journal of Inorganic Chemistry, 2016

Journal of Energy Storage, 2025

Over the past 20 years, nanocarbons have become more significant as nanostructured fillers in com... more 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 implanted
approaches to produce porous carbon materials, CNTs and fibers, carbon nanospheres, carbon dots, reduced graphene oxide, corresponding nanocarbon hybrid materials, and the purification and modification of CNTs are discussed. Finally, 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 or their particles as arcing agents or catalysts, and carbonaceous materials as internal or external susceptors during synthesis and modifications are presented in detail.

Critical Reviews in Solid State and Materials Sciences, Jan 10, 2024

Sustainability, 2024

Lithium (Li), a leading cathode material in rechargeable Li-ion batteries, is vital to modern ene... more Lithium (Li), a leading cathode material in rechargeable Li-ion batteries, is vital to modern energy storage technology, establishing it as one of the most impactful and strategical elements. Given the surge in the electric car market, it is crucial to improve lithium recovery from its rich
mineral deposits using the most effective extraction technique. In recent years, both industry and academia have shown significant interest in Li recovery from various Li-bearing minerals. Of these, only extraction from spodumene has established a reliable industrial production of Li salts. The
current approaches for cracking of the naturally occurring, stable α-spodumene structure into a more open structure—β-spodumene—involve the so-called decrepitation process that takes place at
extreme temperatures of ~1100 ◦C. This conversion is necessary, as β-spodumene is more susceptible to chemical attacks facilitating Li extraction. In the last several decades, many techniques have been
demonstrated and patented to process hard-rock mineral spodumene. The objective of this review is to present a thorough analysis of significant findings and the enhancement of process flowsheets over
time that can be useful for both research endeavors and industrial process improvements. The review focuses on the following techniques: acid methods, alkali methods, carbonate roasting/autoclaving
methods, sulfuric acid roasting/autoclaving methods, chlorinating methods, and mechanochemical activation. Recently, microwaves (MWs), as an energy source, have been employed to transform
α-spodumene into β-spodumene. Considering its energy-efficient and short-duration aspects, the review discusses the interaction mechanism of MWs with solids, MW-assisted decrepitation, and Li extraction efficiencies. Finally, the merits and/or disadvantages, challenges, and prospects of the
processes are summarized.

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Crystals, 2024

Renewable and non-renewable energy harvesting and its storage are important components of our eve... more Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their widespread use, improving LIBs’ performance, such as increasing energy density demand, stability, and safety, remains a significant problem. The anode is an important component in LIBs and determines battery performance. To achieve high-performance batteries, anode subsystems must have a high capacity for ion intercalation/adsorption, high efficiency during charging and discharging operations, minimal reactivity to the electrolyte, excellent cyclability, and non-toxic operation. Group IV elements (Si, Ge, and Sn), transition-metal oxides, nitrides, sulfides, and transition-metal carbonates have all been tested as LIB anode materials. However, these materials have low rate capability due to weak conductivity, dismal cyclability, and fast capacity fading owing to large volume expansion and severe electrode collapse during the cycle operations. Contrarily, carbon nanostructures (1D, 2D, and 3D) have the potential to be employed as anode materials for LIBs due to their large buffer space and Li-ion conductivity. However, their capacity is limited. Blending these two material types to create a conductive and flexible carbon supporting nanocomposite framework as an anode material for LIBs is regarded as one of the most beneficial techniques for improving stability, conductivity, and capacity. This review begins with a quick overview of LIB operations and performance measurement indexes. It then examines the recently reported synthesis methods of carbon-based nanostructured materials and the effects of their properties on high-performance anode materials for LIBs. These include composites made of 1D, 2D, and 3D nanocarbon structures and much higher Li storage-capacity nanostructured compounds (metals, transitional metal oxides, transition-metal sulfides, and other inorganic materials). The strategies employed to improve anode performance by leveraging the intrinsic features of individual constituents and their structural designs are examined. The review concludes with a summary and an outlook for future advancements in this research field.

Advanced Science, Jul 17, 2022

The pillars of Green Chemistry necessitate the development of new chemical methodologies and proc... more The pillars of Green Chemistry necessitate the development of new chemical methodologies and processes that can benefit chemical synthesis in terms of energy efficiency, conservation of resources, product selectivity, operational simplicity and, crucially, health, safety, and environmental impact. Implementation of green principles whenever possible can spur the growth of benign scientific technologies by considering environmental, economical, and societal sustainability in parallel. These principles seem especially important in the context of the manufacture of materials for sustainable energy and environmental applications. In this review, the production of energy conversion materials is taken as an exemplar, by examining the recent growth in the energy-efficient synthesis of thermoelectric nanomaterials for use in devices for thermal energy harvesting. Specifically, "soft chemistry" techniques such as solution-based, solvothermal, microwave-assisted, and mechanochemical (ball-milling) methods as viable and sustainable alternatives to processes performed at high temperature and/or pressure are focused. How some of these new approaches are also considered to thermoelectric materials fabrication can influence the properties and performance of the nanomaterials so-produced and the prospects of developing such techniques further.

Journal of Solid State Chemistry, 2013

Critical Reviews in Solid State and Materials Sciences, 2022

Materialia, 2020

Different contents of NaCl (2%, 4%, 6%, and 8 wt%) was incorporated in polycrystalline PbTe sampl... more Different contents of NaCl (2%, 4%, 6%, and 8 wt%) was incorporated in polycrystalline PbTe samples and consolidated via spark-plasma-sintering (SPS). NaCl acted as a dopant material during SPS. The effect of doping through NaCl increased the carrier concentration without deteriorating mobility. The incorporation of NaCl helped the formation of a porous structure which facilitated high rate of phonon scattering and decreased the thermal conductivity. Experimental observation suggests that the origin of electrical property is due to the extra carriers given by Na, and that Fermi level is well optimized by the compensation effect acquired by Cl doping. The energy barrier heights (EB) for charge carriers in PbTe/NaCl samples is lower than the EB of reference PbTe. High Seebeck coefficient of 300 µV/K at 773 K combined with the lower thermal conductivity of 0.55 W/m-K, yielded an improved figure-of-merit (zT) value as high as 1.2 at 773 K in a 6wt%NaCl:PbTe. In the PbTe/NaCl series, PbT...

The growing market for sensors, internet of things, and wearable devices is fueling the developme... more 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,S...

Ceramics International, 2020

A series of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites (y = 0, 0.04, 0.06, 0.08, and 0.11) was fabr... more A series of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites (y = 0, 0.04, 0.06, 0.08, and 0.11) was fabricated by hydrothermal synthesis of PbTe and Zn0.85Al0.15Te nanoparticles separately, followed by intimate mixing, pressing, and sintering in evacuated-and-encapsulated Pyrex ampoules at 380 °C for 12 h. Thermoelectric properties were characterized from 120-600 K. With increasing Zn content, the peak thermopower shifts to higher temperatures, Hall carrier concentration increases, and the lattice thermal conductivity decreases. As compared to the pristine PbTe, thermoelectric properties of Pb1-y(Zn0.85Al0.15)yTe-Te nanocomposites have improved considerably. The y = 0.11 sample exhibits the highest zT ~1 comparable to the state-of-the-art p-type PbTe-based materials. The enhanced zT is ascribed to reduced thermal conductivity, elevated electrical conductivity and thermopower. This unique new method of material synthesis and doping is very promising to obtain high-performance thermoelectric...

Materials Chemistry and Physics

AIP Advances

Green laser sintering of copper oxide (CuO) nano particle (NP) film to form Cu conductive lines A... more Green laser sintering of copper oxide (CuO) nano particle (NP) film to form Cu conductive lines AIP Advances 8, 095008 (2018);

Journal of Alloys and Compounds

AIP Advances

NiSb nanoparticles by 0.034, 0.074 and 0.16 volume fractions were successfully coated on bulk pol... more NiSb nanoparticles by 0.034, 0.074 and 0.16 volume fractions were successfully coated on bulk polycrystalline Ni 0.05 Mo 3 Sb 5.4 Te 1.6 thermoelectric (TE) particles through a solvothermal route without deteriorating the bulk Ni 0.05 Mo 3 Sb 5.4 Te 1.6 material. The samples were consolidated through hot pressing and their thermoelectric (TE) properties were characterized. At 400 K, 500 K, and 600 K, 0.074 NiSb sample exhibited 22%, 16% and 11.3% increases in the power factor (P.F.) compared to bulk material. The main contributing factor to this enhanced power factor is the elevated electrical conductivity. For the same sample, the reciprocal relationship between Seebeck coefficient and electrical conductivity is decoupled. Sample 0.16 NiSb exhibited the highest electrical conductivity among the three samples. The thermal conductivity of the 0.16 sample was less temperature sensitive compared to other samples. HRTEM and SEM tools were applied to comprehend microstructural features and their relationship to TE transport properties. Pore effect on the thermal and electrical conductivity was elucidated. This study shows that grain-boundary manipulation via this wet chemistry technique is indeed an economically viable method to fabricate and optimize the transport properties of bulk TE materials.

European Journal of Inorganic Chemistry, 2016