Herein, graphene nanocomposite of CuO–rGO is synthesized by simple precipitation reaction. Characterization by different techniques confirms the reduction of graphene oxide and formation of CuO–rGO. ...The CuO nanocrystals are uniformly distributed on graphene sheets. Neutron and X‐ray diffraction (XRD) prove the formation of single phase of CuO monoclinic crystal system with space group C2/c. Infrared spectroscopy shows vibration modes of graphene and CuO. Morphological characterization is carried out by scanning electron microscope (SEM) (SEM) and transmission electron microscope (TEM). It shows that the particle size ranges from 20 to 60 nm in which confirmed by four different theoretical approaches calculated from XRD peaks broadening data. The electronic properties using X‐ray photoelectron spectroscopy are also provided.
The reduction of graphene oxide and formation of CuO–rGO nanocomposite is achieved and confirmed; the crystallite size and micro strain are calculated and tested with four different theoretical approaches based on X‐ray diffraction peaks broadening. X‐ray photoemission spectroscopy and fast fourier transform infrared spectroscopy prove the reduction of graphene by disappearance of graphene oxide peak and prove the ability of using in energy storage applications.
•The melting temperatures of EMIM TFSI confined in carbon mesopores decrease relatively to the bulk IL.•The rotation motions of molecular groups of solid IL confined in pores are slower than this ...motions for IL bulk.•In the low temperature region EMIM TFSI confined in pores forms a low symmetry structure than observed for IL bulk.•The structure of EMIM TFSI confined in nanocarbons of two different diameters (1.4 nm and 4.6 nm) is similar.
We report the melting behavior of ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) confined in nanoporous carbons. The ionic liquids (ILs) are recently mentioned as promising substances in electrochemistry as electrolytes in supercapacitors. The investigation of melting behavior of applied ionic liquid is important for low temperature operation conditions for supercapacitors. In this work, we presented the experimental studies of the melting behavior of EMIM TFSI confined in carbon micropores of about 1.4 nm pore size and also carbon mesopores of pore size of 4.6 nm. The methods of Dielectric Relaxation Spectroscopy (DRS) and Differential Scanning Calorimetry (DSC) in wide temperature ranges were applied. To investigate structural properties of the systems, temperature-controlled Wide-angle X-ray scattering (WAXS) and Neutron Diffraction (ND) methods were adopted. The results obtained from DSC and DRS indicate that the melting temperature of EMIM TFSI confined in carbon nanopores decrease relative to the bulk ionic liquid. Analysis of the structures and dielectric relaxation processes of the EMIM TFSI below their pore melting point indicates the different structure and slower dynamic of EMIM TFSI confined in pores relative to the bulk.
Tungsten carbide hard metal alloy with 6% by weight cobalt was studied before and after irradiation at different fluencies with 167 MeV132Xe ions. Raman spectroscopy, X-ray diffraction, neutron ...diffraction and positron lifetime spectroscopy were employed in order to assess the microstructural evolution in the material upon irradiation fluence increase. Analysis of the Raman spectrum for the pristine, non-irradiated material unveils that the surface is composed of a graphite-like phase and highly oxidized tungsten atoms spread in the carbon matrix. All characteristic peaks of tungsten carbide (WC) and possible cobalt phases are either missing or strongly overlapped in all Raman spectra. Bonding between tungsten and oxygen atoms broke upon irradiation and total deoxidation of the surface is detected for the two highest fluencies investigated at 5 × 1013 ions/cm2 and 3,83 × 1014 ions/cm2. Increasing the irradiation dose causes amorphization of the carbon phase on the surface accompanied by “up and down” trend of change in carbon cluster size. The Raman spectra analysis also unveils, that molecular nitrogen (N2) from the atmosphere penetrates the carbon matrix upon irradiation. The results from the X-ray and neutron diffraction reveal that the main phase in the material is δ-WC and also give information about changes of the lattice parameters with increasing fluence. Reorganization of the induced point defects to dislocation defects as a function of the irradiation dose is discussed, but no phase transition of the main δ-WC phase is detected. Steady increase of compressive internal stress with increasing irradiation dose is noted by XRD. The tendency is not monotonic and the stress leans towards saturation at the highest fluence, with the highest value of −5.26 GPa. The Positron lifetime spectroscopy measurements show the presence of short lifetime component ranging from 170 ps to 190 ps, interpreted as small vacancy clusters. The intensities of the different positron lifetime components vary with the irradiation dose non-monotonically.
•Irradiation with 167 MeV 132Xe ions on WC-6Co to four different fluencies.•Up and down pattern for change in size upon irradiation for C and δ-WC phases.•Simultaneous carbon amorphization and surface deoxidation at the highest fluence.•No main δ-WC phase transition upon irradiation.•Reorganization of point defects to dislocation defects upon irradiation.
Recently, ionic liquids are very promising substances mentioned in electrochemistry as electrolytes in supercapacitors. Due to the fact the operation conditions for supercapacitors require low ...temperatures, an important issue is an investigation of melting behavior of ionic liquid applied as an electrolyte. In the presented work, we report the experimental studies of the melting behavior of 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI); for this purpose the methods of dielectric spectroscopy (DS) and differential scanning calorimetry (DSC) in wide temperature ranges were applied. To investigate the structural properties of the system the temperature-controlled WAXS and Neutron Diffraction methods were adopted. The measurements of the complex permittivity of the studied EMIM TFSI allowed us to determine the relaxation of the system in wide temperature range from 140 K to 300 K. The results obtained from DSC and DS indicate that the ionic liquid on the heating process undergoes two phase transitions: solid-solid transition at temperature 230 K and the melting transition at 257 K, wherein the melting process is not homogeneous. Based on the structural studies results, performed in the temperatures range 10 K – room temperature, it was shown that in the temperature range 10 K–230 K EMIM TFSI forms a crystal monoclinic structure where the rotation motions of molecular groups are observed. At the higher temperature up to the melting temperature the crystal structure is undefined and the rotational motions of molecular groups are changed.
•The melting process of EMIM TFSI ionic liquid is not homogeneous.•Below 230 K EMIM TFSI forms a monoclinic crystal with the rotational motions of molecular groups.•At 230 K system reveals the solid-solid transition from monoclinic to undefined crystal symmetry.•The transition from solid to liquid phase is at 257 K; the residuals of crystal phase exist above 257 K.
