Search

Efficient adsorption of Ba ions was achieved using Sn@TiO2 nanocomposite generated by ultrasonication process with subsequent calcination at 300 °C. X-ray diffraction, nitrogen adsorption-desorption isotherm, X-ray photoelectron spectroscopy, Fourier transformer infra-red, and scanning/transmission electron microscopy analyses were performed to probe the structural and textural features of the adsorbent powder. The XPS, FTIR, and EDX analyses confirmed the Sn doping into TiO2 host lattice. Some interesting features, including the increase of crystallite size and lattice parameters, were attained due to the successful Sn incorporation into the TiO2 host, as indicated further by XRD analysis. The sorption results fitted the Langmuir isotherm model and the kinetic data complied with the pseudo-second-order kinetics. The adsorption process improved markedly above the pHzc due to the electrostatic attraction between the negatively charged Sn@TiO2 particles’ surface and the positively charged Ba ions. The achieved high-performance mesoporous Sn@TiO2 nanostructures for the adsorption of Ba2+ could be potentially utilized to remove other toxic metal cations.

Extensive research to explore cost-effective carbon materials as electrocatalysts and electrode materials for energy conversion and storage has been conducted in the recent literature. This raised a crucial question regarding the origin of this electrocatalytic activity from the heteroatom doping/ hierarchical porous defect-rich architecture and/ or the trace metal impurities introduced during synthesis/ inherent to the precursor. In this work, an insight into this issue is provided by considering a lignocellulosic biowaste, Euryale Ferox (foxnut) shells as a precursor to derive micro/ mesoporous defective graphitic carbon sheets by the phosphoric acid (H3PO4) dictated in-situ carbonization for oxygen reduction reaction (ORR) and supercapacitor applications. The sample synthesized at 900 °C (FP900) shows an onset potential of 0.98 V vs. reversible hydrogen electrode (RHE), ORR current density of 5.5 mA cm−2, and current stability of 93% (in 10 h measurement) in 0.1 M KOH. In addition, a symmetric supercapacitor device is assembled using the prepared material and the specific capacitance of 207.5 F g−1 at 1 A g−1 is obtained. An attempt to explain the origin of the electrochemical performance is made by establishing parallels with the physicochemical characterizations. The inherently doped heteroatoms give rise to electroactive functionalities and the wide enough pore size distribution improves the active sites utilization efficiency by enhancing the accessibility to electrolytic ions resulting in better electrochemical performance. Furthermore, the contribution from the intrinsic trace metal impurities is evaluated using X-ray fluorescence (XRF) spectroscopy. The presented research clarifies the non-contributing nature of trace metal species owing to the inaccessibility of active sites and lower abundance in F900 and FP900, respectively.

The objective of this work was to grow carbon nanocoils (CNCs) on the glass fiber (GF) surface by chemical vapor deposition (CVD) and to prepare laminated composites by hand lay-Up, where CNC-coate...

Microlens arrays find many useful applications in sensing devices though their fabrication is challenging due to rigorous requirement of clean-room processing and equipments thereof. In this context, herein a method for fabrication of large focal number (F#) and high fill factor microlens arrays is presented. These microlens arrays have well-defined boundaries and can be used for wavefront sensing applications. This method of fabrication is robust and can be used for achieving hexagonal as well as square aperture and also it is well suited for mass production. The presence of chrome pedestals below the pillars of photoresist prevents the lenses from merging while reflow and leads to nice and well defined lens boundaries with high fill factor. Main advantage of this method is that it does not require the reactive ion etching and multiple layer lithography and thereby it can be a very inexpensive method of fabrication of large F# (>25) and high fill factor (>95%) microlens arrays. The fabricated microlens arrays have been quantitatively characterized for pitch, aperture size, sag height, surface profile, roughness and 2-D point spread function. Experiments have been carried out to validate these microlens arrays in wavefront sensing for optical metrology applications.

In recent years, heteroatoms-doped graphene, with its exceptional properties, has generated significant advances in many fields of modern nanoscience and nanotechnology. With the rapid progress in ...

Active and durable oxygen reduction reaction (ORR) catalysts are of utmost importance to realize the commercialization of hydrogen fuel cells and metal-air batteries. Al-substituted MnFe2O4-based ternary oxide and reduced graphene oxide (MAF-RGO) nanocomposite is synthesized using an in-situ co-precipitation followed by a hydrothermal process and verified for ORR electrocatalysis in the alkaline electrolyte (0.1 M KOH). MAF-RGO is first analyzed using physicochemical characterization tools including X-ray diffraction, Raman spectroscopy, sorption studies, electron microscopy, X-ray photoelectron spectroscopy, etc. Further, the characteristic ORR peak centered at 0.56 V vs. reversible hydrogen electrode (RHE) in cyclic voltammetry (CV) studies confirms the electrocatalytic performance of MAF-RGO. The ORR onset potential of 0.92 V vs. RHE is obtained in linear sweep voltammetry (LSV) measurement at 1600 rpm in O2-saturated electrolyte exhibiting an improved ORR performance as compared to the commercial electrocatalyst. The reduction kinetics is observed to follow the desirable near 4-e- mechanism. In addition, the electrocatalyst exhibits improved relative current stability of 86% and methanol poisoning resistance of 82%, which is better in comparison to the standard Pt/C. The observed electrochemical performance results from the synergism between the oxygen vacancy-rich Al-substituted metallic oxide active species and the functional group enriched predominantly mesoporous RGO sheets with excellent electrical conductivity. The introduction of metallic species enhanced the inter-planar spacing between graphitic sheets easing the maneuver of reactant species through the electrocatalyst and accessing more ORR-active sites. This study establishes the potency of mixed transition metal oxide/nanocarbon composites as durable high-performance ORR-active systems.

The demand for electromagnetic interference (EMI) shielding has increased strongly in the last few years, owing to the fast technological developments in the electronics industry. In order to meet these markedly increased demands, many new layer-structured materials (as well as other structures with various morphologies) are being investigated to replace conventionally used metal sheets for the purpose of EMI shielding. Carbon-based nanostructures and their composites are used for EMI protection due to their low weight, cost-effectiveness, and good thermal/electrical properties. Polymers are also low density materials, with the added benefits of low cost and easy processing. Composites combining various polymers with different types of conducting carbon fillers have been proposed as EM wave absorbers. MXene-based 2D layered materials have also received tremendous attention for application in EMI shielding. In this review article, we have systematically summarized the recent research on materials designed for microwave/radio wave absorption and EMI shielding. The text covers carbon-based nanostructured materials, various kinds of polymers, layered inorganic materials and their composite hybrids. The review is concluded with a brief discussion of the perspectives and outstanding challenges for future EMI shielding applications of carbon, polymers and MXene-based materials.

Zigzag and armchair graphene nanoribbons (ZGNR and AGNR) have been investigated using the density functional theory (DFT) and nonequilibrium Green’s function (NEGF) framework. Based on binding energy calculations, both-edge-F-functionalized ZGNR emerges as the most thermostatically and energetically stable among various ZGNR and AGNR configurations. The band structures and density of states (DOS) reveal that all the examined configurations of ZGNR exhibit metallic behavior. The I–V characteristics of both-edge-F-functionalized ZGNR shows pure linear behavior among all the configurations of ZGNR and AGNR. For interconnect modeling, the small-signal dynamic performance parameters RBq, CBq, and Lkq are calculated using the standard two-probe model. Furthermore, both-edge-F-functionalized ZGNR shows lower values of CBq (98.07pF/cm), Lkq (45.38nH/ $$\mu $$ m) and quantum delay (42.17 $$\mu $$ s) due to the higher Fermi velocity. The impact of variation of the contact length and ribbon length on the both-edge-F-functionalized ZGNR interconnect model is also presented. F-functionalized ZGNR is a potential candidate for use in future low-power nanoscale high-speed interconnect applications.

The incorporation of a highly doped Si layer below the Si film, termed as the ground plane, in the electrostatically doped junctionless tunnel field effect transistor (ED-JLTFET) with high-K gate stack. This allows the conceptualization and realization of highly reduced ambipolar behaviour with enhancement in the drive current. The deployed GP sinks the electric field induced at drain side, increases the effective channel length for the short channel devices, prevents the direct source-to-drain tunneling and also the channel-to-drain tunneling in reverse direction at negative gate voltages. A significant reduction of sub-threshold slope and DIBL is also reported for the considered device structure. Using a calibrated exhaustive TCAD study, the detailed sensitivity analysis is also carried for the proposed device with the parametric sweep method. Further, the device analog/RF performance is also comprehensively examined for its high frequency operations. Interestingly, it is also observed that the deployment of this GP also results in better volume depletion. Moreover, due to electrostatically doped structure, the reported device is also expected to have a lower thermal budget, immune towards the random dopant fluctuations (RDFs) effects and tolerant towards the velocity degradation effects as well. Hence, the reported device is a potential candidate for implementing ultra low power steep switching transistors.

The presented study stresses that the deposition temperature is an important parameter to determine the quality and properties of deposited Cu2O thin films on copper (Cu) and fluorine-doped tin oxide (FTO) substrates. The optical and electrical properties of chemical bath deposited (CBD) cuprous oxide (Cu2O) thin films with a variety of deposition temperatures (50, 60, 70, and 80 °C) have been extensively investigated. The X-ray diffraction studies reveal the cubic polycrystalline structure of deposited thin films. The scanning electron microscopy (SEM) exhibits a homogeneous thin film constituting Cu2O crystals for 60 °C. Optical studies show the least energy bandgap of 1.90 eV at the optimized deposition temperature. The Cu deposited Cu2O thin film possesses very little resistivity and higher charge carrier concentration mainly due to the contribution from the conducting Cu substrate. The Cu2O films exhibit p-type conductivity in addition to comparable Hall mobility and improved charge carrier concentration by two orders of magnitude in the case of FTO substrate (~ 1017 cm−3). The I–V characteristics of fabricated Schottky junction with the prepared optimized thin film is presented. This study establishes 60 °C as the optimum temperature for Cu2O thin film deposition on different substrates.

Employing plant extracts to obtain nanomaterials is an ecofriendly and highly appreciated synthetic approach. In this work a simple, green chemistry method, based on sol–gel, was used for ZnO nanoparticles synthesis by using two Sudanese medicinal plant extracts: Adanosia digitata (ZnO-A) and Balanites aegyptiaca (ZnO-B) under ultrasonic energy. The X-ray diffraction (XRD) revealed the formation of wurtzite hexagonal ZnO nanostructures, while the scanning electron microscopy (SEM) analysis displayed their diverse morphologies. The X-ray photoelectron spectroscopy (XPS) data showed the impact of extract via the variation in of the O1s and Zn2p3/2 and Zn2p1/2 orbitals binding energy of Zn–O. The UV-visible investigation indicated a variation of bandgap energy (E g ), where the ZnO nanoparticles displayed the lowest E g . The synthesized nanomaterials have exhibited high photocatalytic efficiency towards the methylene blue (MB) dye. The findings revealed the possibility of obtaining nanoparticles with tailored properties by using plants extracts.

The photodegradation of Congo red dye by (Y2O3)n ZnO photocomposites was investigated through a sequence of experiments. X-ray diffraction analysis indicates nanocomposites' evolution having the ZnO wurtzite structure with increase in crystallite size and Y2O3 phase segregation, as confirmed by the appearance and gradual growth of the Y2O3 peak. Field emission scanning electron microscopy observations reveal irregular spherical morphology with increased agglomeration due to Y2O3 loading. Diffuse reflectance spectra exhibit bandgap widening and red shift of the absorption edge with the doping process. Brunauer–Emmett–Teller analysis denotes improved porosity as manifested by the surface area, pore diameter, and pore volume increments after yttrium loading. Fortuitously, photocatalysts demonstrate excellent photodegradation rates for CR dye, reaching 93% at a higher rate of 43 × 10–3 min−1. The photocomposite 1% Y2O3–ZnO exhibits a threefold enhancement in the visible photocatalytic process in an aqueous solution. The photocatalytic performance is discussed in detail concerning pH and oxygen species, which contribute to the photodegradation of CR dye. The results obtained in this study clearly highlight the superior performance (Y2O3)n ZnO as a highly efficient photocatalyst in the degradation of dyes in water.

In this work, a sol–gel method has been employed to fabricate Cr-doped ZnO nanoparticles (NPs) in the presence of starch at different annealing temperatures. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and Fourier transforms infrared spectroscopy (FTIR). All samples were defined as hexagonal wurtzite ZnO with particle sizes equal to 26, 22, and 31 nm for pure ZnO, Cr-doped ZnO at 500 °C and 700 °C, respectively. The Cr-doped ZnO photocatalyst at 500 °C shifted the band gap energy of ZnO from 3.16 to 3.09 eV. The nanomaterials' photocatalytic activity was tested through the photodegradation of congo red (CR) under visible light illumination. The results demonstrated that the Cr-doped ZnO annealed at 500 °C is an excellent photocatalyst with enhanced degradation competence towards CR dye by virtue of its reduced size and lower band gap energy. The kinetics of the photodegradation fitted the pseudo-first-order model while the mechanistic investigations revealed the great impact of h+ and ·OH on the degradation process. The starch-stabilized chromium-doped ZnO shows a high photocatalytic activity towards CR, indicating their possible environmental remediation application.

The paper presents the structural stability and electronic properties of Zigzag Gallium Nitride nano ribbons(ZGaNNR) by considering the lithium(Li) atom by employing density functional theory (DFT). Li atom has been considered as a passivating element at various symmetric sites. By using Li atoms, a significant impact has been observed on the structural and electronic characteristics of ZGaNNRs. Bare@edges_both structure emerged to be the most energetically stable among other structures. For Li-passivation@edge_Ga structures, the minimum band gap has been noticed for III-V group family of nanoribbons. Interestingly, other structures of ZGaNNRs turn metallic nature irrespective of the Li site. Further, Li-bare@edge_N structure possesses the highest Fermi velocity as compared to other structures. This is useful for designing high speed interconnect applications. Further, we investigated the effective mass of various Li-ZGaNNR structures using standard two probe models. The effective mass of H-bare@edge_N structure reveals the highest effective mass in both valence and conduction bands. The proposed work proves the high capability towards the designing of the nano-scale devices.

Herewith we report a facile synthesis of zinc oxide doped with (5, 10, 15 and 20 wt%) titanium oxide nanocomposites in gelatin under ultra-sonication. The X-ray diffraction (XRD) data revealed the ZnO formation in addition to a rutile TiO2 phase. The ZnO phase size decreased, while the rutile TiO2 phase increased with a TiO2 loading increment. The scanning electron microscopy (SEM) displayed a combination of spherical and hexagonal particles with 60–80 nm size distribution. The photocatalytic activity of the prepared nanostructures was assisted using Rhodamine B dye, where they showed enhanced photodegradation competence under visible light irradiation. The kinetics of photodegradation followed the first-order kinetics with the 20%wt sample showing the maximum activity. The mechanistic investigation revealed the dominance of h+ and ·O2− species during the dye photodegradation. The results indicate the potential application of such gelatin-stabilized nanostructures for dye illumination from aqueous solutions under sunlight.

Lignin is one of the primary residues obtained after the processing of lignocellulosic biomass. However, most residual lignin is burnt directly to get rid of it, albeit one of the few biorenewable waste resources that can yield aromatics. Therefore, the present study investigates reductive depolymerization of Kraft lignin into aromatics in the presence of Pt/HZSM-23 catalyst. In this regard, the lignin conversion experiments were performed under mild reaction conditions at a temperature range of 100 °C to 200 °C for 1 h to 12 h in a high-pressure batch reactor. Besides, a comparative study was done on the effect of the supply of external hydrogen and in-situ hydrogenation. Eventually, 87.3% lignin conversion was measured yielding 65.1% bio-oil, primarily aromatics at optimized experimental conditions. It was observed that the mesopores in the Pt/HZSM-23 catalyst facilitate the transfer of larger molecules derived from the Kraft lignin, thus causing an overall improvement in the catalytic activity. A mechanistic study based on experimental conditions and products detected using GC-MS revealed that the in-situ hydrogen transfer route is more favorable for lignin depolymerization than externally supplied hydrogen.

In this research work, Carbon-carbon composites (CCCs) were fabricated via carbonization of carbon nanotubes (CNTs)-coated carbon textile (CNT-CF) reinforced polymer matrix composites (PMCs) preforms at 600, 900, 1200, and 1500 °C in a tubular furnace. To obtain CNT-CF, MWCNTs were produced radially on the surface of the nano-nickel particles plated carbon textile at 700°C using catalytic chemical vapor deposition method and C2H2 gas as a carbon source. The effects of CNT coating on carbon textiles were evaluated using FESEM, HR-TEM, XRD, Raman, TGA, and BET analysis. The effects of heat treatment temperatures on CNTs coated and uncoated PMCs manufactured using simple hand-layup method subsequently hot compressing were evaluated through XRD, FESEM, density, electrical conductivity measurement, tensile and flexural test, and viscoelastic properties using DMTA. The CNT coated CCCs obtained at 1500°C exhibited ∼ 66, 62, 83, 27, 44, 30, and 36% enhancement in electrical conductivity, storage modulus, loss modulus, tensile strength, Young’s modulus, flexural strength, and flexural modulus of CNT coated CCCs, respectively compare to uncoated CCCs. Moreover, substantial enhancement in thermal stability of PMCs and CCCs make CNT-CF as one of the competent alternate reinforcement for the fabrication of structural parts used in high-performance applications.

This work reports a scalable method to synthesize hierarchically porous, hetero-atom doped activated carbon nanosheet from waste biomass−human hair, and demonstrates the use of this carbon as an ultra-high performance electrode material for supercapacitor applications. Microscopic analyses reveal that sheet size ranges from 50 to 200 nm having a thickness of 15–27 nm. As-synthesized, carbon nanosheets possess a hierarchical porous structure having a specific surface area of 1548 m2 g−1. Heteroatom concentration (nitrogen, oxygen, and sulfur) of around 25% is confirmed from XPS analysis. Therefore, the novel interconnected hierarchical porous nanosheets structure enables fast adsorption and transportation of ions during electrochemical processes. Also, the abundant chemically available electroactive heteroatom species in the material enhance the wettability of ions and contribute to pseudocapacitance. The electrochemical analyses through cyclic voltammetry and galvanostatic charge-discharge measurements in 6 M KOH reveal the quasi-EDLC behavior of the activated carbons due to the presence of heteroatoms. A reprensentative KOH activated carbon shows an excellent specific capacitance value of 999 F g−1 at a current density of 1 A g-1. The symmetrically assembled two-electrode device also delivers a maximum energy density of 32 W h Kg-1 at a power density of 325 W Kg-1. In addition, excellent cyclic stability of 98% capacitance retention is observed after 10,000 continuous GCD cycles even at a high current density of 5 A g−1. Symmetric flexible supercapacitor device using KOH-PVA-K3FeCN6 as redox gel polymer electrolyte shows a synergistic specific capacitance of 145 mF cm−1 at a current density of 0.8 mA cm−1 exhibiting very less deviation in bending mode. Therefore, this waste biomass derived heteroatom doped hierarchical porous carbon nanosheets can be a promising material for cost-effective high- performance supercapacitor.

Heteroatom-doped graphene and its derived layered materials play a substantial role in several emerging science fields, demonstrating great potential for implementation in new devices and for improving the performance of existing technologies. A wide variety of strategies have been applied for the controlled synthesis and for achieving the intended doping/co-doping levels in the carbon network of graphene-based materials. Precise and reproducible doping is crucial for altering the Fermi energy level and to tune the band gap according to the desired device/application. Heteroatom-doped and co-doped graphene-based materials (n-type and p-type doping) have been synthesized for devices in energy-related applications using various chemical and physical routes. In this review article, we survey the most recent research works on the synthesis of heteroatom-doped graphene materials such as reduced graphene oxide, graphene oxide, graphene quantum dots and graphene nanoribbons. Applications of these materials in energy storage/conversion devices (supercapacitors, batteries, fuel cells, water splitting and solar cells) are also reviewed. Finally, the challenges and future perspectives for heteroatom-doped graphene materials are briefly discussed. We hope this article offers a useful starting point for researchers entering the field, providing an overview of synthesis approaches and energy applications.

The present work reports the synthesis of Al-X wt.% Si (X = 20, 30, 40 and 50) alloys by a unique combination of pressureless sintering (PLS) and hot forging at 800 and 1000 MPa forging pressures with 37.5 and 50% deformation, respectively, in a specially designed die. The effect of hot forging parameters on densification, hardness, compressive strength and microstructures of the alloys was studied as well as suitably compared with the conventional PLS alloys. The ‘PLS + forged’ alloys, specifically 50% deformed at 1000 MPa, yielded excellent densification and subsequent very good mechanical properties. The combination of hot forging pressure and temperature enabled the high densification due to pore collapse, fracturing of Si particles leading to Al flow between the fractured Si particles and better interfacial diffusion between Si and Al. Moreover, the alloys showed excellent electrical conductivity (~67% of that of pure Al), low coefficient of thermal expansion (CTE) and high thermal conductivity (TC) at par with the same alloys prepared with other methods, like spark plasma sintering, hot pressing and Osprey techniques.

Rational and strategic fabrication of cost-effective, active and durable oxygen reduction reaction (ORR) electrocatalyst is the bottle-neck for the commercialization of fuel cells and metal-air batteries. Atomically dispersed nickel (Ni)/nickel sulfide (NixSy) anchored on heteroatom doped networked hierarchical porous carbonaceous sheets are synthesized from nickel nitrate and guanidine thiocyanate. The sample annealed at 750 °C followed by acid-treatment (Ni-GT-750-A) emerges as the best performing pH-universal ORR catalyst with an onset potential of 0.91 (0.1 M KOH) and 0.89 V (0.1 M HClO4) vs. reversible hydrogen electrode (RHE). It also exhibits better current durability (95.0 and 60%) and methanol tolerance (90.6 and 80.3%) in comparison to the commercial catalyst (65.0, 27, −33.0 and 16.5%) in alkaline and acidic media, respectively. An insight into the microstructure and ORR-active chemical sites is obtained with the aid of electron microscopic (FE-SEM and HR-TEM) and physiochemical (sorption isotherm, XRD, Raman and XPS) studies, respectively. The enhanced activity results from the synergistic influence of metallic ORR-active sites in hierarchical porous doped defective carbon support, which provides the well-interlinked conducting channel for electron transfer and additional ORR-active sites. The introduced electrocatalyst establishes Ni decorated doped carbon systems as potential revolutionary substitutes for commercial systems.

In the present study, the milled carbon fiber (MCF) and conductive polyaniline (PANI) are impregnated in the epoxy matrix to synthesize lightweight nanocomposite providing efficient microwave absor...

In this research work, a dual-metal hetero-dielectric with nitride gate all around field effect transistor (DM-HD-NA GAAFET) has been proposed to address and mitigate an essential issue of drain induced barrier lowering and tunnelling leakage current. This device also provides better transconductance, output conductance, early voltage, and transforming growth factor so that it can also be used for radio-frequency (RF) applications. In this structure, silicon dioxide (SiO 2 ) is used at the source side while the silicon nitride (Si 3 N 4 ) is used at drain side to reduce tunnelling of charge. In DM-HD-NA GAAFET, gate material engineering (GME) technique is also being used in which higher work function metal is used at source side in order to accelerate charge carriers while lower work function metal is used at drain side so that it can increase ON-state current ( I ON ). The obtained results are compared with dual-metal hetero-dielectric with vacuum gate all around field effect transistor (DM-HD-VA GAAFET) to analyse its performance. In the proposed device structure, I ON increased by GME approach while I OFF decreased by hetero-dielectric method so it improves I ON / I OFF ratio for DM-HD-NA GAAFET compared to DM-HD-VA GAAFET device.

A donor–acceptor coordination polymer (TPA-Zn) was synthesized by Zn(II)-assisted self-assembly of an in situ generated triphenylamine (TPA) cored tristerpyridine ligand. The polymer absorbs a broad-spectrum of light and exhibits visible light-assisted hydrogen generation (27.1 mmol g−1 over 9 h) from water with 2.9% quantum efficiency at 400 nm. The microscopy images show a mesoscale fibrous morphology and the Brunauer–Emmett–Teller (BET) analysis reveals the porous nature of TPA-Zn (surface area: 234.5 m2 g; d = 6.98 nm), both of which are helpful for substrate diffusion during catalysis.

This study investigates the role of metal-support interaction (MSI) in the performance of Ni/TiO2, Ni/SBA-15, Ni/MgO, and Ni/Al2O3 catalysts for the tri-reforming of methane (TRM) reaction. To impart weak metal-support interaction (WMSI), the catalysts were calcined at 400 °C. While calcination at 850 °C or above temperature generated strong metal-support interaction (SMSI) in each catalyst. The experimental results reveal that Ni/TiO2 and Ni/MgO catalysts having WMSI displayed high initial activity due to the higher extent of reduction and Ni dispersion. However, these catalysts deactivated during 10 h reaction run. On the other hand, the performances of Ni/TiO2 and Ni/MgO catalysts having SMSI were unsatisfactory. For Ni/SBA-15 catalyst system, catalysts having weaker MSI were more active than the catalyst having stronger MSI. However, the stability of Ni/SBA-15 catalysts was governed by Ni confinement in the pores of SBA-15 rather than the strength of MSI. Ni/Al2O3 having SMSI had monodispersed Ni atoms in close association with Al2O3, which resulted in higher reforming activity compared to that of Ni/Al2O3 having WMSI. Overall, the present study asserts that the strength of MSI has a significant influence on the activity and stability of methane tri-reforming catalysts; however, the suitability of either strong or weak MSI is subject to catalyst composition.

Ba-doped ZnO nanostructures (0.8–4 mmol) were successfully fabricated by the co-precipitation method. X-ray diffraction analysis indicated that all samples exhibited a typical hexagonal wurtzite ZnO structure with the emergence of BaO phase. Moreover, the incorporation of Ba resulted in an increase of crystallite size and lattice parameter while microstrain decreases. The broadening of the Zn–O vibrational band and the redshift in Raman vibrational modes provided clear evidence of the incorporation of Ba within ZnO host lattice. Furthermore, Ba doping prompted an increase of the dielectric constant and ac conductivity (σac). Additionally, the subsequent decrease in tangent loss with increasing the applied field frequency was associated with the hopping frequency of electron that enhances the charge carriers’ mobility.

The aim of this work consists on the synthesis of a nanomaterial for heavy metal ion removal from aqueous solutions. Al-doped ZnO (ZnO:Alx%) nanopowders with 0 to 5% Al content are prepared via an amended sol-gel method. The morphology and microstructure of the prepared ZnO:Alx% are probed by means of scanning electron microscopy (SEM), X-ray particles diffraction (XRD) analysis, energy dispersive X-ray spectroscopy (EDS) and elemental mapping. The findings reveal the prevalence of the hexagonal wurtzite ZnO structure with increasing crystallite size (45 to 60 nm) as a result of Al doping. SEM images show nearly spherical nanoparticles with considerable aggregation. EDS and elemental mapping analysis confirm the incorporation of Al within ZnO host lattice. The relatively large surface area as estimated from N2 adsorption makes the nanopowders very favorable for the uptake Cd(II), Cr (IV), Co (II) and Ni(II) from aqueous solution. The ZnO:Alx% with 1 wt% Al exhibits the highest uptake rate of heavy metal ions. The adsorption process has been found to be spontaneous and endothermic and obey Langmuir adsorption model. The high tendency of the prepared nanoparticles to eliminate heavy metal ions renders them suitable candidates for environmental remediation. Desorption studies with 0.1 M NaOH indicate that ZnO:Alx% can be regenerated effectively.

BACKGROUND: Decontamination of water by means of photocatalysis is seen as a sustainable solution. However, catalysts with low recovery from liquid suspension remain the main predicament that obstructs their industrial applications. To overcome this shortcoming, a methodology is reported here for the functionalization of nanospinel nickel zinc ferrite by cystamine ligand to develop Ni₀.₅Zn₀.₅Fe₂O₄@cystamine magnetic recyclable catalyst for water decontamination applications. RESULTS: The diffraction patterns of bare and functionalized nanoferrites indicated that the cubic inverse spinel structure of the particles was not changed after cystamine functionalization. X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses confirmed the chemical bonding between cystamine and spinel ferrites. The spherical morphology and elemental composition were studied through high‐resolution transmission electron spectroscopy (HRTEM) images and energy‐dispersive X‐ray (EDX) analysis respectively. Deeper understanding of the catalyst's optical behavior and calculation of the energy band gap were achieved by means of photoluminescence spectroscopy. Magnetic saturation values were calculated from vibrating sample magnetometer (VSM) analysis, and almost negligible change was found. A possible photocatalytic mechanism for the removal of organic dye is proposed. CONCLUSION: The present findings imply that the presence of amine groups on the catalyst surface, good dispersibility stability and outstanding catalytic activity make functionalized nanoferrite a suitable candidate for industrial wastewater treatment. Easy synthesis, easy work‐up and short reaction times are some of the advantages of the methodology. © 2019 Society of Chemical Industry

This Spotlight on Applications highlights the significant impact of microwave-assisted methods for synthesis and modification of carbon materials with enhanced properties for electrodes in energy storage applications (supercapacitors and batteries). For the past few years, microwave irradiation has been increasingly used for the synthesis of carbon materials with different morphologies using various precursors. Microwave processing exhibits numerous advantages, such as short processing times, high yield, expanded reaction conditions, high reproducibility, and high purity of products. On this frontier research area, we have discussed microwave-assisted synthesis, defect creation, simultaneous reduction and exfoliation, and heteroatom doping in carbon materials. By careful manipulation of microwave irradiation parameters, the method becomes a powerful and efficient tool to generate different morphologies in carbon-based materials. Other important outcomes are the flexible control over the degree of reduction and exfoliation of graphene derivatives, the generation of defects in graphene-based materials by metals, the intercalation of metal oxides into graphene derivatives, and heteroatom doping of graphene materials. The Spotlight on Applications aims to provide a condensed overview of the current progress in carbon-based electrodes synthesized by microwave, pointing out outstanding challenges and offering a few suggestions to trigger more research endeavors in this important field.

In a previous study [1], the authors have investigated stacked silicon microcoolers and quantified their thermal performance envelope in a separable format where the microcooler is attached to an electronic package lid with an intervening TIM2. In this study, we expand the previous study by integrating the stacked microcoolers into an electronic package, i.e., by removing the lid and the TIM2.A summary of thermal resistance and pressure drop experimental data spanning a wide range of fluid flow rates is presented. Additionally, numerical modeling using FEA/CFD models is conducted and the results compared to the experimental data.Results reveal that the thermal performance of the integrated microcoolers is ~ 30% superior that of the separated microcoolers. The numerical model results accurately predict the experimental data to within 20%. Directions for future thermal performance improvements using multiple inlet/outlet ports and varying the number of cooler stacks are identified using the numerical models.

We introduce a new packaging technology termed as Direct Bonded Heterogeneous Integration (DBHi) where a Si-bridge is directly bonded to and in between processor chips using Cu pillars, allowing high-bandwidth low-latency low-power communication between the chips. The DBHi package structure, test vehicle design, and bond and assembly details are first described. The test vehicle package consists of chips with standard interconnect pitch where they join to a laminate chip-carrier and fine-pitch pads in the region where the chips joins to a bridge. The bridge has Cu pillars correspondingly mating to the pads on the chips. The bond and assembly sequence starts with first joining the silicon chips and bridge using a thermocompression bonding process followed by a mass reflow join of the chips to the laminate. The assembly is then underfilled and capped using specialized techniques. Mechanical modeling was extensively used to simulate the DBHi structure and assembly process to allow material selection and reliability prediction. The mechanical models were calibrated using warpage measurements. The stress/strain reliability metrics of the DBHi package are compared to a non-bridge package of the same dimensions. Results show that the main focus should be directed towards ensuring a robust assembly process as the standard reliability stress/strain metrics of the DBHi package are very similar to a non-bridge package. Thermal measurements using chip heaters and temperature sensors were conducted to calibrate a numerical thermal model of the DBHi package. The thermal model was exercised to show the relation between the allowable chip and bridge power densities for the particular package size and cooling conditions. DBHi test packages were created using the best-known assembly process and then measured for continuity performance. A variety of inter- and intra-bridge daisy chain nets were incorporated into the test vehicle for continuity measurements. Post-assembly continuity measurements demonstrated a robust assembly process for multiple rounds of assembly. Reliability performance was demonstrated using standard JEDEC tests of thermal cycling, aging, and temperature/humidity.

The recently introduced Direct Bonded Heterogeneous Integration (DBHi) Si bridge technology has chips connected by a bridge housed inside a cavity or trench that is precisely machined in the chip-carrier laminate. The size, thickness, and placement centrality of the bridge are critical parameters that are necessary to prevent interference with the laminate substrate trench. In this study, we compared laser and saw dicing processes for the DBHi bridge technology. Different laser dicing recipes are developed and optimized. The laser and saw dicing process are compared for dimensional tolerances, edge quality, and die strength of the bridge chips. The die strength is affected by the edge defects on the top and bottom surfaces adjacent to the edges and is measured using a three-point bend fixture in a Universal Testing Machine (UTM). The laser dicing process is improved to equalize the die strength at both the surfaces as well as to achieve equal or higher die strength than blade dicing specifically for the thinner wafer thicknesses.

With increasing processing capability and power consumption in multi-layered micro-electronic packages, efficient thermal management and structural integrity continue to remain crucial factors for ensuring package reliability. Effective and simple to implement analytical methods for temperature and warpage prediction are important tools to predict the thermo-mechanical performance of a package. While many existing analytical thermal models predict exact or approximate solutions [1], [2], they are computationally expensive for non-uniform power distributions and do not account for the effect of thermal warpage on the package thermal resistances and the temperature distribution. Similarly, existing methodologies for calculating the warpage or thermal stresses in bi- and multi-layer strip [3], [4] do not consider non-uniform power distribution on the chip surface.This paper presents an analytical solution for the temperature distribution in a multilayer chip-on-spreader package, combining the thermal warpage of the chip and package with the imposed uniform and non-uniform power distributions on the chip. An analytical solution is developed to calculate the warpage and the radius of curvature for a multilayer unlidded package as a result of mismatch in the thermal expansion of the package components as its temperature varies. The model is verified against Timoshenko’s model for two layers and is found to be a match. The temperature distribution on the chip is calculated using an analytical method for an unwarped package [5] where the linear superposition principle is applied to an exact solution of heat transfer in the spreader, coupled with 1D heat conduction from the chip and the thermal interface material (TIM) to the spreader. The two methods are solved implicitly until a converged solution is reached. The temperature distribution and the warpage results are presented for 10 by 10 grid uniform and non-uniform power maps applied to the chip. The model predicts a significant change in the temperature distribution as a result of package warpage. The results are also reported for a 60 by 60 grid non-uniform power map representative of power dissipation in a server chip. A comparison between the analytical model and the numerical results is also presented and are found to be in good agreement.

Using silicon for microcooler fabrication is advantageous over metals as it can be micromachined for smaller fin wall and channel width dimensions, increasing the thermal heat transfer coefficient [1], [2]. Since the fin height is limited by the wafer thickness, multiple microcoolers are stacked to increase the total fin height to enhance the heat transfer from a chip. Stacked silicon microcoolers have been previously designed, fabricated, and characterized for thermal performance [3].In a multi-core processor package, the power density across the chip surface is highly nonuniform; the power density in the cores can be 4-6 times that outside the cores. In this study, we explore a variety of non-uniform power distributions on the chip surface for characterizing the thermal performance of integrated stacked silicon microcoolers. An array of individually controllable heaters, present on the test chip, is used to generate heating patterns corresponding to high-power computing cores. The thermal resistance to the heat transfer across the microcooler and the pressure drop in the water flow across the microcooler are characterized as a function of the flow rate. The cooling power limits of such high-power computing core maps are also defined. Finally, a numerical analysis is performed for the non-uniform power dissipation cases to validate the experimental results.

Thermal analysis is used to predict operating temperatures in electronic packages. Thermal analysis is deterministically conducted using finite element, control volume, finite difference, or analytical methods. Input parameters include package geometry, material properties, and cooling conditions. Accuracy of the predicted temperatures depends on the accuracy of the material properties and the imposed heat transfer coefficient. The run-time for a thermal model depends on the complexity of the package geometry. For a complex computational fluid dynamics (CFD) model, the run-time may extend over several hours.In this paper, we utilize a predictive model using artificial neural networks (ANNs). The forward and backward propagation steps of the neural network model are programmed using MATLAB, with a cost function that minimizes the error between the inferred and the input data generated using a finite element model. The input data are randomized and then normalized so that the ANN weights can be reasonably determined.The input data are generated using analytical and ANSYS thermal models of a chip-on-substrate geometry applicable to electronic packaging. The chip size, the TIM bond thickness, the heat spreader thermal conductivity and thickness, and the heat transfer coefficient imposed on top of the heat spreader are varied in the thermal model. The imposed heat transfer coefficient combines the effect of the cooling fluid and the extended surface area of a heat sink or cold plate attached to the lid.Various input sets are analyzed to co-optimize the size of the training set, the number of hidden layers in the ANN model, and the inference error. It is demonstrated that ANN methods can be effectively used to predict package operating temperatures.

One of the essential requirements for efficient performance and longer service life of machined components is a good surface finish. Though there are other traditional finishing processes like lapping, grinding, and honing. However, the major disadvantage associated with them is, they can process only simple geometry. Abrasive flow machining (AFM), due to its self-deforming characteristic, is used for finishing parts having predominantly irregular geometry. All AFM processes comprise a machine, fixture, and media (i.e., carrier/or putty mixed with abrasive particles) among which, media (viscoelastic polymer) plays a dominant role. The commercial abrasive, which is one of the constituents of the viscoelastic media for AFM, which provides the finishing action (abrasion), are very expensive and hence it is a major problem for the small industries. Also, the finishing cost per unit component (workpiece) with a commercial media having SiC/diamond abrasives turns out to be very high, which makes its use uneconomical for mass finishing. Therefore, in the present research work, an attempt has been made to develop an alternative low-cost AFM media by replacing commercial abrasives with waste coal fly-ash. The developed media are characterized through static and dynamic rheological tests, thermogravimetric analysis, and finishing experiments on aluminum and mild steel workpieces to judge the performance of newly developed media concerning the traditional one. The percentage improvement obtained in average surface roughness(ΔRa) through fully fly-ash-based media (68% fly-ash) is ~56% for the aluminum and ~49% for mild steel workpieces.

The recently introduced Direct Bonded Heterogeneous Integration (DBHi) Si bridge technology [1] consists of chips directly connected by a bridge chip though Cu pillars, enabling high speed and high band-width communication between CPUs, GPUs and memory chips. The bridge chip resides in a cavity machined in the laminate chip carrier. The remaining structure of the DBHi package is similar to a standard flip-chip package. In this study, we focus on the thermal characterization of the DBHi package using measurements and simulations. We determine how much heat generation is allowed for a bridge chip using a conventional cooling solution from the chip top side. The thermal measurements are conducted using a DBHi package with thermal test chips containing heaters and temperature sensors. The chips are heated by supplying power to the heaters and the temperatures on the chips are measured using resistance temperature devices. We then build a simulation model which is calibrated with the thermal measurement results by adjusting the heat transfer coefficient applied to the package lid top. The model comprises two chips, a bridge chip, interconnects between the chips and the bridge, interconnects between the two large chips and a laminate, a Thermal Interface Material (TIM) and a heat-spreader (a lid). Based on this simulation model, it is examined how much heat generation is allowed for a bridge chip when its maximum temperature is to remain below 75 °C (with an ambient = 40 °C). For example, it is simulated that when each chip generates 100 W (total 200 W for two chips), 26.5 W of heat generation is allowed for a bridge chip. We also consider potential cooling solutions from the laminate side.

Cocrystallization of a nonconductive, boron-based host with aromatic guests generates conductive cocrystals. Carrier mobilities of the cocrystals with either pyrene or tetrathiafulvalene were measu...

Biomass-derived syngas (CO2 + CO + H2) has emerged as a potential non-fossil fuel source to yield transportation fuel via Fischer Tropsch Synthesis (FTS) reaction. Thus, the present study demonstrates the conversion of CO2 containing syngas into fuel range hydrocarbon via Fischer Tropsch Synthesis over Fe–Co bimetallic catalyst. The experimental tests were carried out in a fixed bed continuous reactor to investigate the effect of CO2 on CO/CO2 conversion. Accordingly, obtained data were validated by FTS kinetic model for a plug flow reactor. It was found that the unique combination of Fe and Co bimetallic catalyst facilitates both FTS and water gas shift (WGS) reaction simultaneously that helps to convert CO2 along with CO. It was also observed that the presence of iron in the catalyst helps in conversion of CO2 into hydrocarbons, only when a particular concentration of CO2 in syngas is reached, i.e., critical ratio RC (CO2/CO + CO2) due to the occurrence of reverse water gas reaction (RWGS) which varies with the temperature and the feed gas composition (H2/CO/CO2 molar ratio). At 240 °C and hydrogen deficient condition, the critical ratio was measured to be 0.74 whereas for hydrogen balanced condition, it was measured 0.6. The kinetic model developed in the present study predicted trends for % CO conversion, % carbon conversion, and % CO2 conversion which is applicable for a wide range of critical ratio RC (CO2/(CO + CO2) = 0 to 1). The model also predicted that a positive conversion of CO2 could be achieved at lower CO2 concentration by increasing the reaction temperature. At 260 °C and 280 °C, the value of Rc were 0.31 and 0.18 were measured.

The integration of nanomaterials with the micro-wave technology is a significant step toward the development of low-cost and low-power RF gas sensors. But, the issues associated with materials like insignificant surface area and poor conductivity, are barriers for the rapid detection of wide range of gas concentrations. In this paper, we demonstrate the proof-of concept using an RF complementary split ring resonator (CSRR) integrated ZnO/N-doped graphene (NGN) nano-hybrid to study the gas sensing properties. This RF device senses the presence of ammonia based on the change in the electrical conductivity of the nanohybrid material upon gas exposure. For this, we have designed and fabricated various new CSRR structures, namely, the meander (M-CSRR) and the CSRR, with the concentric-etched square pattern (SP-CSRR) other than the conventional CSRR (C-CSRR). The fabricated CSRRs are coated with the solvothermal methodically prepared ZnO/NGN nanomaterials and a comparison among them is also made. The comparison revealed that the SP-CSRR coated ZnO/NGN sensor had the maximum shift in the S21 resonance frequency ( $\Delta \text {f}_{\mathbf {S21}} = 13$ MHz at 100 ppm) among all at room temperature. Furthermore, the SP-CSRR-ZnO/NGN sensor exhibited a large-S21 frequency shift of 133 MHz for 500 ppm of ammonia and has shown excellent reproducibility with 0.05% of variation. We have also projected the plausible sensing mechanism for this RF sensing device.

A facile synthesis of undoped and 2.0 % selenium-doped zinc oxide nanoparticles (NPs) was efficaciously accomplished through a mechanochemical route using zinc acetate dihydrate, oxalic acid, and Se powder in a solid state reaction. After calcination at 450 °C, the obtained nanostructures were probed by X-ray diffraction, where the acquired data revealed the pertinence of the wurtzite hexagonal ZnO for both undoped (ZnO) and doped (Se/ZnO) NPs and crystallite sizes of 30 and 24 nm for ZnO and Se/ZnO, respectively. The formation of the target NPs was confirmed by the scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and the Fourier transformation infrared molecular vibrations data. The porosity investigations indicated 33.65 m2/g Brunauer–Emmett–Teller surface area, 197 Å pore diameter, and 0.172 cm3/g pore volume for the Se/ZnO NPs compared to lower values for the pristine ZnO. The band gap energies were 3.19 and 3.15 eV for ZnO and Se/ZnO as perceived from the Tauc plots of the UV-visible absorption measurements. The photodegradation of methylene blue dye under UV illumination was found to follow the pseudo–first-order kinetics with an enhanced performance by the doped samples as reflected by the higher (3.2 × 10−3 s−1) rate constant relative to the undoped sample (1.7 × 10−3 s−1). A photodegradation mechanism was suggested in the light of the band gap energy investigation. The obtained findings indicate the improvement of ZnO properties by doping with Se through a simplistic and inexpensive approach.

Constructing nanostructures of high capacity materials and hybridizing the same with conductive carbon networks are important for high performing lithium ion batteries. Here, we demonstrate new carambola-shaped crystalline SnO2 (c-SnO2), which is wrapped in a three-dimensional multiwalled carbon nanotube network (c-SnO2@3D-CNT). The carambola structure of c-SnO2 is constructed by changing the surface energy of a specific crystalline plane using a potassium fluoride capping agent. The as-designed c-SnO2@3D-CNT achieves a high capacity of 1140.2 mA·h·g−1 at 50 mA·g−1, a capacity retention of 50.7% retained at 1000 mA·g−1 relative to 50 mA·g−1, and a cycling stability of 72.0% over 500 cycles at a high rate of 1000 mA·g−1. In particular, the c-SnO2@3D-CNT shows a high volumetric capacity of 1674.8 mA·h·cm−3 at 50 mA·g−1 and 849.2 mA·h·cm−3 at 1000 mA·g−1, which is greater than those of previous SnO2-based materials. This finding is associated with the compact packing of hierarchical carambola structure having multiple concave surfaces into dense and porous electrode. Therefore, the hierarchical carambola structure and 3D hybrid architecture provide a buffer space for volume expansion and fast ion/electronic conducting pathways, which impart a high volumetric capacity, improved cyclic and rate performances, and higher reversibility than other SnO2 materials.

The potential use of Barium (Ba) doped ZnO nanoparticles for the photo-degradation of a mixture of dyes that mimics natural effluents has been attempted. Undoped and Ba-doped ZnO nanoparticles were efficiently synthesized via co-precipitation method. The effect of Ba concentration on the structural, morphological, optical properties and photocatalytic activity of ZnO nanoparticles was probed. X-ray diffraction analysis disclosed the formation of hexagonal polycrystalline nanoparticles with ZnO wurtzite crystal structure having an average crystallite sizes ranging from 20 nm for pure ZnO up to 28 nm in diameter after adding different ratios of barium. The FE-SEM images revealed rod-like nanoflakes morphology for all of the samples with a clear influence of the presence of Ba impurities on the width of the rods. Mapping analysis showed even Ba distribution in the ZnO lattice. FTIR spectra manifested the presence of the characteristic absorption peak at 400–600 cm−1 of Zn–O stretching modes confirming the target nanoparticles synthesis. While the BET and BJH data analysis indicated increased specific surface area and reduced pore volume as a result of Ba intercalation. The incorporation of Ba into the ZnO matrix has shifted the 371 nm absorption band to 475 nm as observed in photoluminescence spectra for all samples. This red shift in the absorption was reflected in lowering the band energy enabling it to decolorize a dyes mixture under visible light illumination. Based on the aforesaid results, the Ba doping is responsible for the visible light driven photocatalytic activity of the composites.

The slurry erosion behavior of high-velocity oxy-fuel-sprayed iron-based amorphous coatings and the reference stainless steel were both investigated. The slurry erosion–corrosion test was performed in a rotating disk rig facility with circulating system using distilled water and 3.5 wt.% NaCl slurries. The performance of uncoated substrate and as-coated samples was evaluated at various operating parameters, namely impingement angle, slurry concentration, and specimen rotational speed. The effects of the slurry erosion parameters on the microstructure and the properties of the coatings were systematically studied. The wear mechanisms of coated and uncoated samples were investigated using scanning electron microscopy. The results showed that amorphous coating exhibited higher slurry erosion–corrosion resistance compared to the stainless steel.