Density functional theory simulation of cobalt oxide aggregation and facile synthesis of a cobalt oxide, gold and multiwalled carbon nanotube based ternary composite for a high performance supercapattery

A novel ternary composite consisting of cobalt oxide (Co3O4) nanoparticles (NPs) grown on multiwalled carbon nanotubes (MWCNTs) and mixed with gold (Au) NPs is synthesized by a single step hydrothermal route. Initially, density functional theory (DFT) simulations were carried out to model the aggregation of Co3O4 NPs and validated further with experimental results. To circumvent this issue, MWCNTs with gold NPs were introduced, which significantly reduced the particle aggregation. Standard three electrode cell studies revealed that the Co3O4/Au@MWCNT composite possesses an excellent energy density, rate capability and very good cyclic stability compared to unsupported Co3O4 or the binary Co3O4@MWCNT. The promising electrochemical performance compared to the single Co3O4 or the binary Co3O4@MWCNT materials is assigned to the synergetic effects of MWCNTs and Au to disaggregate the Co3O4 NPs and to enhance the overall conductivity, respectively. In order to get insight into the evaluation of the performance, two electrode devices were assembled employing activated carbon as a negative electrode and the Co3O4/Au@MWCNT composite as a positive electrode material. The two electrode supercapattery device demonstrated splendid cycling stability with a retention value of 91.90% in 1 M KOH for over 3500 cycles. Additionally, it exhibited an excellent energy density of 18.80 W h kg-1 at a power density of 302.00 W kg-1. These encouraging outcomes can be associated with the distinctive morphology, outstanding conductive networks, increased electroactive sites, and emergence of strong networking of Co3O4, MWCNT and Au in the ternary composite. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

High performance supercapattery incorporating ternary nanocomposite of multiwalled carbon nanotubes decorated with Co 3 O 4 nanograins and silver nanoparticles as electrode material

Cobalt oxide (Co3O4) nanograins were in situ grown on chemically activated multiwall carbon nanotubes (MWCNT) and anchored with silver (Ag) nanoparticles to form a ternary nanocomposite (MWCNT-Co3O4-Ag) by simple single step hydrothermal route. The structural crystallinity and successful synthesis of MWCNT-Co3O4-Ag nanocomposite were confirmed by X-ray diffraction. The surface morphology, homogeneity, specific surface area and crystallinity were evaluated by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy with mapping, Brunauer Emmett Teller and X-ray diffraction analysis, respectively. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy were conducted in 1 M KOH electrolyte to analyze electrochemical performance of the prepared samples as an electrode material for supercapattery. The MWCNT-Co3O4-Ag nanocomposite witnessed the maximum specific capacity of 83.88 Cg-1 at 0.6 Ag-1 which is substantially higher than MWCNT-Co3O4 (55.33 Cg-1) and Co3O4 nanograins (39.24 Cg-1) in standard three electrode cell system. The remarkable electrochemical performance of ternary nanocomposite was associated with the effect of Co3O4 nanograins, conductive platform provided by the MWCNT and synergistic effect of Ag nanoparticles. The supercapattery devices were fabricated in a configuration of MWCNT-Co3O4-Ag//activated carbon. The hybrid device was capable to operate in stable potential window of 1.5 V even at higher scan rates. It was observed that the fabricated supercapattery showed an energy density of 16.5 Whkg−1 with power density of 297.5 Wkg-1 at current density of 0.2 Ag-1. Additionally, life cycle test revealed that supercapattery was highly stable and lost only 6.4% of its initial capacity after 3000 cycles

ALD grown nanostructured ZnO thin films: Effect of substrate temperature on thickness and energy band gap

Nanostructured ZnO thin films with high transparency have been grown on glass substrate by atomic layer deposition at various temperatures ranging from 100 °C to 300 °C. Efforts have been made to observe the effect of substrate temperature on the thickness of the deposited thin films and its consequences on the energy band gap. A remarkably high growth rate of 0.56 nm per cycle at a substrate temperature of 200 °C for ZnO thin films have been achieved. This is the maximum growth rate for ALD deposited ZnO thin films ever reported so far to the best of our knowledge. The studies of field emission scanning electron microscopy and X-ray diffractometry patterns confirm the deposition of uniform and high quality nanosturtured ZnO thin films which have a polycrystalline nature with preferential orientation along (100) plane. The thickness of the films deposited at different substrate temperatures was measured by ellipsometry and surface profiling system while the UV–visible and photoluminescence spectroscopy studies have been used to evaluate the optical properties of the respective thin films. It has been observed that the thickness of the thin film depends on the substrate temperatures which ultimately affect the optical and structural parameters of the thin films

Deposition of SiOx layer by plasma-enhanced chemical vapor deposition for the protection of silver (Ag) surfaces

Silver surfaces have been treated with plasma-enhanced chemical vapor deposition to produce SiO2-like coatings for possible applications in the jewelry industry. Different experimental conditions have been tested in order to optimize the protective effectiveness of the deposited layers. Samples were analyzed with optical and scanning electron microscopy and energy-dispersive spectrometry

Laser-induced forward transfer (LIFT) of material using ablation of thin films

We show the controlled transfer of thin films of different metallic materials to a receiving substrate. Single pulses from a mode locked (40ps pulse), frequency-doubled Nd:YAG laser (energy flux approximate to 13J/cm2 at 532nm) were used. Receiving substrates (metals, semiconductors or crystals) were placed parallel, at a close proximity to the thin film. Optical and scanning electron microscopy (SEM) as well as EDAX analysis were performed, showing evidence of the production of micrometric scale patterns. In particular, we studied the transfer of precious metal to metal/crystals for possible application in the jewellery industry

Influence of consecutive picosecond pulses at 532 nm wavelength on laser ablation of human teeth

The interaction of 40 ps pulse duration laser emitting at 532 nm wavelength with human dental tissue (enamel, dentin, and dentin-enamel junction) has been investigated. The crater profile and the surface morphology have been studied by using a confocal auto-fluorescence microscope (working in reflection mode) and a scanning electron microscope. Crater profile and crater morphology were studied after applying consecutive laser pulses and it was found that the ablation depth increases with the number of consecutive pulses, leaving the crater diameter unchanged. We found that the thermal damage is reduced by using short duration laser pulses, which implies an increased retention of restorative material. We observe carbonization of the irradiated samples, which does not imply changes in the chemical composition. Finally, the use of 40 ps pulse duration laser may become a state of art in conservative dentistry

Laser induced forward transfer (LIFT) of materials using 40 ps pulses-experimental and quantitative modelisation study

In this paper we report the results of experiments on LIFT performed using single pulses from a mode locked (40ps pulses), frequency doubled Nd:YAG laser (energy flux approximate to 13J/cm(2) at lambda = 532 nm). We studied the controlled transfer of thin films of different metallic materials to a receiving substrate. Optical and scanning electron microscopy (SEM) as well as Energy-dispersive X-ray spectroscopy (EDAX) analysis were performed, showing evidence of the production of micrometric scale patterns. One of our objectives is to investigate and develop possible applications of LIFT in jewellery industry. In order to understand the experimental results we developed a simple analytical model based on the Rankine-Hugoniot relations. Comparison between experimental and simulated results is presented

Hydrothermally Assisted Synthesis of Porous Polyaniline@Carbon Nanotubes–Manganese Dioxide Ternary Composite for Potential Application in Supercapattery

In this study, ternary composites of polyaniline (PANI) with manganese dioxide (MnO2) nanorods and carbon nanotubes (CNTs) were prepared by employing a hydrothermal methodology and in-situ oxidative polymerization of aniline. The morphological analysis by scanning electron microscopy showed that the MnO2 possessed nanorod like structures in its pristine form, while in the ternary PANI@CNT/MnO2 composite, coating of PANI over CNT/MnO2, rods/tubes were evidently seen. The structural analysis by X-ray diffraction and X-ray photoelectron spectroscopy showed peaks corresponding to MnO2, PANI and CNT, which suggested efficacy of the synthesis methodology. The electrochemical performance in contrast to individual components revealed the enhanced performance of PANI@CNT/MnO2 composite due to the synergistic/additional effect of PANI, CNT and MnO2 compared to pure MnO2, PANI and PANI@CNT. The PANI@CNT/MnO2 ternary composite exhibited an excellent specific capacity of 143.26 C g−1 at a scan rate of 3 mV s−1. The cyclic stability of the supercapattery (PANI@CNT/MnO2/activated carbon)—consisting of a battery type electrode—demonstrated a gradual increase in specific capacity with continuous charge–discharge over ~1000 cycles and showed a cyclic stability of 119% compared to its initial value after 3500 cycles