22 research outputs found
Fabrication of novel red light emitting PVA/ZnO: Eu3+ electrospun composite nanofibers
No full textPolyvinyl Alcohol (PVA)/ZnO: Eu3+ composite nanofibers (NFs) have been successfully prepared by Electrospinning technique. The crystal structure, surface morphology, distribution of elements and photoluminescence properties of composite NFs were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and Photoluminescence (PL) spectroscopy respectively. XRD pattern confirmed the successful incorporation of ZnO: Eu3+ nanophosphors into the PVA matrix whereas EDX demonstrated the homogeneous distribution of elements. The bonding characteristics of composite NFs were analyzed by FTIR. The composite NFs exhibited red emission peak at 635 nm under the excitation wavelength of 266 nm. Tunability in colors from blue to red is observed for the composite NFs. Excellent values of color coordinates of the PVA/ZnO: Eu3+ composite NFs make them fascinating for illuminating the solid state lighting (SSL) world
A Strategy to Produce Single and Double Layer Graphene Sheets
No full textWe report an easy and scaleable approach to produce single and double layer graphene (Gr)-sheet from re-exfoliation of expanded graphite (EG) with large area. Transmission and scanning electron microscopic observations show that the Gr-sheets have an area of ~ (12 x 10) μm2. Raman spectroscopy has confirmed the presence of single and double layer Gr-sheet with I2D/IG ratio as ~ 1.7. Scanning probe microscopy studies reveals that on re-exfoliation of EG, thickness of Gr-layer decreases from 6-7 nm to 0.8-1.1 nm. This infers that re-exfoliation overcomes the problem of insufficient oxidation or inadequate pressure buildup during heat treatment.</jats:p
Dielectric and impedance properties of three dimension graphene oxide-carbon nanotube acrylonitrile butadiene styrene hybrid composites
No full textFacile synthesis of bulk SnO2 and ZnO tetrapod based graphene nanocomposites for optical and sensing application
No full textIn the present investigation Tin oxide(SnO2)/Graphene, Zinc oxide tetrapods(ZnO-T)/Graphene and SnO2/ZnO-T/Graphene nanocomposites were synthesized using simple chemical route from a mixture of few layer graphene (FLG) derived from re-exfoliation of expanded graphite and Sn02 and ZnO-T nano structures via sonication and centrifugation. The resultant composites structures were characterized by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscope (SEM), High resolution transmission electron microscope (HRTEM) and Photoluminescence spectroscopy. The XRD studies reveal crystallographic phases of all the three compounds exist in nanocomposite. The SEM demonstrated SnO2 and ZnO-T were uniformly distributed with few layer graphene (FLG). HRTEM micrograph reveals SnO2 and ZnO-T were incorporated in between graphene layers and resultant nanocomposites have advantages of both micro and nanostructures. All three types of nanocomposites were fascinating morphological structures which altered both optical absorbance and photoluminescence properties. The initial investigation suggests that all metal oxide graphene nanostructure composites well responding as humidity sensor in different humidity environment
Tri-axial Seismic Simulation of Solar Inverter – Productivity Improvement
No full textAbstractOften, earthquake is a tri-axial event, as in, it excites the system in all three directions. Evaluation of big systems like high capacity solar inverters for such events through testing is quite expensive. Trend these days is to qualify the system using CAE simulation, in contrast to testing. Simulation of big systems is always a challenge, as it becomes computationally expensive due to high node count and large number of modes in the frequency range of interest. In this work, seismic analysis is performed using commercial FEA software ANSYS. Conventional way of seismic simulation in ANSYS is to first excite the system separately in the orthogonal directions and then compute the tri-axial response by superposition of responses in individual directions. In this paper, based on the response spectrum analysis, a tri-axial seismic analysis methodology is proposed and implemented on complicated high capacity solar inverters. Proposed methodology calculates a resultant mode participation factor from mode participation factors due to excitation in individual directions and then performs the mode combination. It was observed that computational time was reduced to 1/3rd without any compromise in the accuracy of response. Also, proposed simulation methodology doesn’t require separate static analysis to account for the effect of missing mass. This further increases the productivity of a seismic engineer performing a finite element analysis
The production of multi-layer graphene nanoribbons from thermally reduced unzipped multi-walled carbon nanotubes
No full textAn easy and scalable approach is reported for the production of multi-layer graphene nanoribbons (GNRs) from thermally treated unzipped multi-walled carbon nanotubes (MWCNTs) by controlled oxidation and intercalation. The prepared GNRs are characterized using transmission and scanning electron microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. AFM studies show that the thickness of the unzipped MWCNTs lies in the range of 100-124 nm, which correspond to similar to 150-185 GNRs, whereas the width is in the ranges of 500-700 nm. This could be due to the displacement of loose individual graphene layers in the solvent during sonication process. The irregular edges of the multi-layer GNR appeared due to the presence of functional groups attached at the edges, is confirmed by XPS. The XPS studies reveals that the amount of defects present on the nanoribbons after heat treatment at 1000 degrees C is almost same as that of as synthesized MWCNTs. However, on heat treatment at 2500 degrees C, defects are reduced and the quality of ribbon is improved. Also, Raman spectroscopy has confirmed that on heat treatment at 2500 degrees C the quality of GNRs is improved and I(D)/I(G) ratio decreases from 0.92 to 0.44
One-step synthesis of lignin-derived carbon nanofibers without the need for stabilization: Characterization and applications
No full textThermal oxidative stabilization is a crucial parameter in carbon nanofiber (CNF) synthesis which which is important for the retention of fiber geometry during the rigorous carbonization process. However, its conventional implementation is burdened by significant time and energy expenditures. This study explores the feasibility of circumventing the stabilization step and its repercussions on the properties of lignin-PVA-derived electrospun CNF mats. Electrospun mats were subjected to carbonization after thermal stabilization (St-CNF) and without thermal stabilization (NSt-CNF). The morphological analysis revealed that despite the exclusion of stabilization, the fibrous structure remains intact without fusion. However, its noticeable impact on carbon yield, graphitic content, and defect density of CNF has been observed. In comparison to NSt-CNF, the St-CNF has higher carbon yield and mass loss fraction, suggesting additional cross-linking and thermal stability. Additionally, a higher specific surface area (381.5 m2/g) and pore volume (0.40 cc/g) were also observed in St-CNF compared to NSt-CNF (162.9 m2/g, 0.15 cc/g), enhancing the electrochemical properties such as specific capacitance (191.5 F/g), energy and power density (26.6 Wh/kg at 520.5 W/kg) of St-CNF. This study provides valuable insight into the properties of lignin-based CNFs, prepared by including or excluding the stabilization step, and explores their potential effect in energy storage applications
Excellent mechanical properties of long multiwalled carbon nanotube bridged Kevlar fabric
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