Browsing by Author "Sachin Kumar Yadav"

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3D nanocomposites of β-TCP-H3BO3-Cu with improved mechanical and biological performances for bone regeneration applications
(Nature Research, 2025) Sarvesh Kumar Avinashi; Rajat Kumar Mishra; n. Shweta; Saurabh Kumar; Amreen Shamsad; Shama Parveen; Surajita Sahu; Savita Kumari; Zaireen Fatima; Sachin Kumar Yadav; Monisha Banerjee; Monalisa Mishra; Neeraj Mehta; Chandkiram Gautam
Recently, 3-D porous architecture of the composites play a key role in cell proliferation, bone regeneration, and anticancer activities. The osteoinductive and osteoconductive properties of β-TCP allow for the complete repair of numerous bone defects. Herein, β-TCP was synthesized by wet chemical precipitation route, and their 3-D porous composites with H3BO3 and Cu nanoparticles were prepared by the solid-state reaction method with improved mechanical and biological performances. Several characterization techniques have been used to investigate the various characteristics of fabricated porous composites. SEM and TEM studies revealed the porous morphology and hexagonal sheets of the β-TCP for the composite THC8 (82TCP-10H3BO3-8Cu). Moreover, the mechanical study showed excellent compressive strength (188 MPa), a high Young’s modulus (2.84 GPa), and elevated fracture toughness (9.11 MPa.m1/2). An in vitro study by MTT assay on osteoblast (MG-63) cells demonstrated no or minimal cytotoxicity at the higher concentration, 100 µg/ml after 24 h and it was found a more pronounced result at 20 µg/ml on increasing the concentration of Cu nanoparticles after incubating 72 h. The THC12 composite showed the highest antibacterial potency exclusively against B. subtilis. S. pyogene, S. typhi and E. coli. at 10 mg/ml, indicating its potential effectiveness in inhibiting all of these pathogens. Genotoxicity and cytotoxicity tests were also performed on rearing Drosophila melanogaster, and these findings did not detect any trypan blue-positive staining, which further recommended that the existence of composites did not harm the larval gut. Therefore, the fabricated porous composites THC8 and THC12 are suitable for bone regrowth without harming the surrounding cells and protect against bacterial infections. © The Author(s) 2025.
Beyond graphene basics: A holistic review of electronic structure, synthesis strategies, properties, and graphene-based electrode materials for supercapacitor applications
(Elsevier Ltd, 2025) Sachin Kumar Yadav; A. Sameer Ruban Kumar; Neeraj Mehta
This review presents a comprehensive analysis of graphene-based electrode materials for supercapacitor application, focusing on electronic structure, synthesis strategies, and key attributes. The remarkable 2D-structure of graphene, characterized by sp2 hybridized carbon atoms, confers exceptional electronic mobility (100000 cm2V−1s−1), large specific surface area (2600 m2g-1), and mechanical flexibility (2.4 ± 0.4 TPa), making it an ideal contender for next-generation energy storage devices. We have discussed various synthesis strategies, including CVD, mechanical exfoliation, and chemical reduction, emphasizing their impact on the electrochemical performance of graphene electrodes. The integration of graphene with other nanomaterials, such as metal oxides, TMDs, conducting polymers, and MXenes, is explored to enhance the specific capacitance, cycle stability, and energy density of supercapacitor electrode materials. This review also covers the tunable electronic properties of graphene, addressing charge transport, ion diffusion, and electrochemical performance, which are critical for efficient supercapacitor design. Graphene-based electrodes' flexibility and mechanical stability are examined, highlighting their role in wearable and portable electronic applications. Challenges such as large-scale production, electrode degradation, and cost-effectiveness are also discussed, offering potential solutions through innovative synthesis routes and composite material design. This review provides a holistic perspective on the current advancement of graphene-based electrode materials for supercapacitor applications. © 2025 Elsevier Ltd
Impedance spectroscopy of multicomponent Se-Te-Sn-In chalcogenide glass ceramics
(Elsevier B.V., 2025) Kaushal Kumar Sarswat; Sachin Kumar Yadav; Neeraj Mehta
The present research investigates the influence of indium incorporation (2%, 4%, and 6%) in Se78-xTe20Sn2Inx chalcogenide glass-ceramic alloys on electrical impedance spectroscopy, complex modulus, and temperature-dependent conductivity across a broad frequency range (0.1–500 kHz) and temperature window (300–333 K). The impedance response, analyzed using equivalent circuit modeling, reveals a transition from a single to a double semicircular arc, indicating contributions from both grain and grain boundary regions. A distinct non-Debye relaxation behavior and negative temperature coefficient of resistance (NTCR) are observed, highlighting thermally activated charge transport. The activation energy derived from relaxation time and AC conductivity follows Arrhenius trends, while the Meyer-Neldel rule confirms entropy-assisted hopping conduction. The shortest relaxation time (∼10⁻¹¹ s) and moderate activation energies (0.26–0.34 eV) suggest excellent dielectric responsiveness and rapid polarization, favorable for energy storage and conversion devices. These results underscore the potential of indium-doped Se-Te-Sn glasses as functional layers in next-generation thermoelectric modules, supercapacitors, and solid-state ionic conductors for energy applications. © 2025 The Author(s)
Kinetic modeling and iso-conversional analysis of glass-ceramics of selenium doped with carbon nanomaterials
(Institute of Physics, 2025) Sachin Kumar Yadav; Shiv Kumar Pal; A. Dahshan; Neeraj Mehta
This study addresses a gap in understanding the impact of carbon nanomaterial doping on the crystallization kinetics of selenium glass, particularly when utilizing model-free iso-conversional methods. Previous research has explored the properties of elemental selenium; however, the role of dopants like multiwall carbon nanotubes (MWCNTs) and graphene in altering glass-to-crystal phase transitions at non-isothermal conditions has not been thoroughly analyzed. In the context of selenium glass crystallization, multiwall carbon nanotubes (MWCNTs), and graphene may alter the crystal growth kinetics significantly during glass/crystal phase transformation. Keeping in mind these facts, the present endeavor focuses on analyzing the doping effect of MWCNT and Graphene on the non-isothermal kinetic reaction mechanism of Selenium measured with differential scanning calorimetry (DSC) at different heating rates. The model-free relations such as Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Tang, and Straink methods were applied using iso-conversional approach for determining the activation energy of amorphous to crystalline transformation as well as the Avrami index. Iso-conversional study yields adequate activation energy as a function of the conversion coefficient. We have observed the decreasing behavior of Ec(α) along with the extent of crystallization of four iso-conversional methods. The kinetic triplet parameters (i.e., activation energy Eα, rate constant Kα, and order parameter nα) have been calculated using the VHR method derived from the Johnson-Mehl-Avrami (JMA) rate equation. The value of ‘n’ is reduced with the rise in the value of the extent of conversion α which indicates the reduction in the growth rate of crystallization because of its saturation. This study provides novel insights into the thermal stability and kinetic mechanisms within doped selenium glass-ceramics, expanding the potential applications of chalcogenide glasses in phase-change memory and other fields. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Perspectives of dielectric and A.C. conductivity behavior of MWCNT and graphene-doped amorphous Selenium thin films
(Springer, 2024) Sachin Kumar Yadav; S.S. Fouad; H.E. Atyia; N. Mehta
In the current study, we have focused on the dielectric and A.C. conductivity behavior in thin films of Se:Graphene and Se:MWCNTs nanocomposite samples by doping graphene and MWCNT in g-Se. The thin films of aforesaid nanocomposites have been prepared by physical vapor deposition. The well-known Meyer–Neldel rule and Jonscher’s Universal power law have been employed to investigate the variation of A.C. conductivity with frequency and temperature. The strong dependence of conductivity over temperature is described using a model that is applied for correlated barrier hopping (CBH) in Se:MWCNTs thin films. However, the non-overlapping small polaron tunneling (NSPT) model is found to be applicable for Se:Graphene thin film. The activation energy for the nanocomposite thin films was evaluated from the Arrhenius plot. The random free energy barrier hopping model explains the system’s ac conductivity (σac). In our study, we observed the Meyer–Neldel rule (MNR) as well as reverse MNR for Se:Graphene and Se:MWCNTs nanocomposite thin films, respectively. The investigation of dielectric loss confirms that the theory of Guintini regarding dielectric dispersion applies to our samples. © 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Study of linear and non-linear optoelectronic properties of thermally grown thin films of amorphous selenium doped with graphene, multiwalled carbon nanotubes, and silver nanoparticles
(Elsevier Ltd, 2023) Sachin Kumar Yadav; H.E. Atyia; S.S. Fouad; Arvind Sharma; Neeraj Mehta
The present research covers the impact of doping of different nano-materials [Graphene, Multiwalled Carbon Nanotubes (MWCNTs), and Silver nanoparticles (Ag: NPs)] on the optoelectronic properties of selenium glass. For this, we have prepared the amorphous thin films (ATFs) of pure selenium and nano-additives doped Se and the systematic optical characterization of ATFs of as-prepared samples has been done. We have examined the optical characteristics of prepared ATFs by collecting the experimental spectral data of reflection/transmission in the range of 400 nm to 2500 nm. Knowing the spectral variation of the dispersion parameters, we have calculated the values of the optical band gap Egopt and Urbach tail Ee. The indirect optical transition is found in the present samples that are confirmed by the transition power factor m. The values of real component (i.e., ε') and imaginary components (i.e., ε″) of the dielectric constant and its value in the high-frequency range (i.e., ε∞), as well as single-oscillator dispersion parameters, are also determined. The value of infinite dielectric constant (ε∞) of ATF of parent selenium (ε∞ = 2.65) is increased significantly after the doping of graphene (ε∞ = 3.82), MWCNT (ε∞ = 4.37), and Ag: NPs (ε∞ = 6.19). Further, we have investigated the dependence of tan δ (dissipation factor), τ (relaxation time), optical/electrical conductivities, and volume/surface energy loss functions on photon energy hν. The nonlinear properties of the samples are discussed in terms of their susceptibility and nonlinear refractive index. © 2023 Elsevier B.V.
Synthesis and characterization of graphene oxide-based nanofluids and study of their thermal conductivity
(Springer Science and Business Media B.V., 2022) Sachin Kumar Yadav; Diptarka Roy; Anil Kumar Yadav; Pinky Sagar; Sarvesh Kumar Avinashi
In the present research work, we investigated the effect of loading mass concentrations (0.05%, 0.15%, and 0.25 mass %) and temperature (10–50 °C) on the thermal properties of graphene oxide-ethylene glycol (GO-EG) nanofluids. A two-step approach was adopted to prepare the GO-EG nanofluids with different mass proportions without any surfactant. The thermal kinetic analysis was performed by modulated DSC and TGA. Thermal stability and particle size distribution of the nanofluids were monitored by using UV–visible spectroscopy and dynamic light scattering. The experimental findings on the thermal transport characteristics of the as-prepared nanofluid samples are influenced by loading mass concentration, increasing temperature because of the high relative area of dispersed nanoparticles at higher particle concentration, dispersion quality of nanofluids. The thermal conductivity (TC) of GO-EG nanofluid shows an enhancement of 36.72% for (sample no. 3, i.e., GO 3) and shows a semi-linear dependence profile between temperature and TC, with increasing mass concentration due to the decrease in interfacial thermal resistance between GO and EG. The observed results are in good agreement with previously reported literature and reveal the promising prospect for usage as a state-of-the-art heat transport fluid in the coolant industry. © 2022, Akadémiai Kiadó, Budapest, Hungary.
Synthesis and characterization of nanostructured graphene-doped selenium
(Royal Society of Chemistry, 2023) Sachin Kumar Yadav; Amit Kumar; N. Mehta
In this work, we explore various properties of elemental selenium glass (g-Se) by doping with graphene through the facile melt-quench technique. The structural information of the synthesized sample was found by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy. The analyses confirm that the graphene-doped g-Se behaves like a glass-ceramic material. Electrical and dielectric measurements were performed to discover the consequences of graphene incorporation on the nano-structure of g-Se. The electrical measurements of the dielectric parameters (i.e., dielectric constant ϵ′ and loss ϵ′′) and conductivity (σac) reveal that graphene incorporation causes a rise in the dielectric constant but simultaneously increases dielectric loss. The enhancement in ϵ′ and ϵ′′ values is thought to be a consequence of the interface effect between graphene and the host selenium glass. Calorimetric experiments were performed in a standard differential scanning calorimetry (DSC) unit on the glassy nanocomposite in non-isothermal mode. By measuring the kinetic temperatures at four heating rates, the kinetics of the crystallization/glass transition were studied. The results were examined to understand the role of graphene doping on the well-known phase transitions (i.e., glass transition and crystallization) of g-Se. © 2023 The Royal Society of Chemistry.
Tailoring of physical properties of glassy selenium (g-Se) by using multi-walled carbon nanotubes (MWCNTs)
(Elsevier Ltd, 2023) Sachin Kumar Yadav; Amit Kumar; N. Mehta
The present research reports the studies of the different physical properties of a novel kind of glass nanocomposite sample that belongs to the nano-structuring of glassy selenium (g-Se) by choosing multiwall carbon nanotubes (MWCNTs) as a dopant. The structural analysis of the sample is done by employing different techniques [e.g., Scanning electron microscopy (SEM), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Raman spectroscopy]. The detailed analysis reveals that the MWCNTs are incorporated successfully in the glass matrix of Se. The occurrence of thermally activated glass transition/crystallization in the present glass nanocomposite sample has been investigated by thermal analysis of calorimetric measurements. The thermo-mechanical and electrical properties of this sample have been studied by micro-indentation test, and current–voltage measurements respectively. We have also compared different physical properties of current glass composites with that of g-Se for understanding the consequences of MWCNTs doping in the parent g-Se. The detailed analysis shows that the electrical conductivity, hardness, threshold voltage of resistive switching, and modulus of elasticity of the parent sample (i.e., g-Se) are increased drastically after the doping of MWCNTs, whereas there is a drastic reduction in the thermal stability and volume of the micro-voids. © 2023 Elsevier B.V.
Tuning dielectric, mechanical, and electrical properties in rGO/graphite-reinforced selenium nanocomposites
(Elsevier Ltd, 2025) Sachin Kumar Yadav; A. Dahshan; Neeraj Mehta
This work examines the dielectric, electrical, and microhardness properties of melt-quench prepared graphite@rGO#Selenium nanocomposites. The dielectric properties of the nanocomposites (NCs) have been investigated over a frequency range of 100–500 kHz and a temperature range of 303–333 K. Frequency-dependent a.c. conductivity studies reveal that the prepared NCs follow the correlated barrier hopping (CBH) conduction mechanism. The permittivity increases due to interfacial polarization and the expansion of the microcapacitor network. The frequency-dependent electrical conductivity follows universal Jonscher's power law. The thermally activated electrical conductivity of NCs was determined along with the activation energy, hopping distance, and maximum barrier height of the NCs. These findings indicate that Se:rGO NC shows promise as a dielectric material with a high dielectric constant and low dielectric loss. The enhanced mechanical properties are attributed to the increased crystallinity of the pure selenium matrix and rGO-reinforced NC. This study aims to elucidate the relaxation behaviour and conduction mechanism of graphite/rGO-reinforced selenium NCs across various temperatures. © 2025
Unveiling of physical, structural, morphological, and electrical properties of Fe2O3doped (30-x)BaO•30TiO2•40SiO2•x[Fe2O3], (0≤x≤6) glass-ceramics potential for energy storage devices
(Elsevier Ltd, 2025) Rajat Kumar Mishra; Sarvesh Kumar Avinashi; Sachin Kumar Yadav; Zaireen Fatima; Rajbala Nain; Rakhi; Savita Kumari; Shweta; Neeraj Mehta; Rakesh Kumar Dwivedi; Chandkiram Gautam
Glass-ceramics with tuneable dielectric properties are increasingly sought after for next-generation multilayer ceramic capacitors (MLCCs) used in advanced electronic applications. However, developing compositions that simultaneously offer high dielectric constants, low dielectric losses, and excellent thermal stability remains a significant challenge. Herein, Fe2O3-doped (30-x)BaO•30TiO2•40SiO2•x[Fe2O3] (0≤x ≤ 6 mol%) glass and glass-ceramics are synthesized using a melt-quenching followed by controlled heat treatment technique. XRD is performed which indicates a transition from amorphous to crystalline structures after heat treatment, with a major phase of tetragonal fresnoite (Ba2TiSi2O8). To check the bonding mechanisms, Fourier transform infrared (FTIR) and Raman spectroscopies are performed. X-ray photoelectron spectroscopy was performed for analysing the elemental composition, and electronic state of a material. However, to study the microstructural behaviour, crystalline nature, and compositional variations, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), followed by energy dispersive spectroscopy (EDS) were also performed. Dielectric properties of the GCs are studied over 10 Hz to 1 MHz. Notably, 24BaO•30TiO2•40SiO2•6Fe2O3(BTSFC6) (x = 6 mol%) sample demonstrates improved dielectric constant (εr = 31740.4) and low dielectric loss (Tanδ = 0.13) at 10 Hz (at 500 °C). The incorporation of Fe2O3not only enhances the AC conductivity but also modifies the electrical relaxation behaviour, as evident from modulus and Cole–Cole plots, which indicate non-Debye-type relaxation and a negative temperature coefficient of resistivity (NTCR) behaviour. Furthermore, hysteresis loop measurements were conducted, revealing that an increase in Fe2O3content in BTSFC glass-ceramics leads to a systematic enhancement in ferroelectric properties and energy storage capacity. This improvement enables material to be tailored for a wide range of applications, from low-loss dielectrics to high-energy storage devices. Therefore, this study demonstrates that strategic Fe2O3doping effectively tailors the structural and dielectric characteristics of barium-titanate silicate glass-ceramics, positioning the BTSFC6 composition as a promising candidate for the fabrication of energy storage devices in demanding thermal and electronic environments. © 2025 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.