3D nanorhombus nickel nitride as stable and cost-effective counter electrodes for dye-sensitized solar cells and supercapacitor applications.

Transition metal nitride based materials have attracted significant interest owing to their excellent properties and multiple applications in the field of electrochemical energy conversion and storage devices. Herein we synthesize 3D nanorhombus nickel nitride (Ni3N) thin films by adopting a reactive radio frequency magnetron sputtering process. The as-deposited 3D nano rhombus Ni3N thin films were utilized as cost-effective electrodes in the fabrication of supercapacitors (SCs) and dye-sensitized solar cells (DSSCs). The structure, phase formation, surface morphology and elemental composition of the as-deposited Ni3N thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM). The electrochemical supercapacitive performance of the Ni3N thin films was examined by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques, in 3 M KOH supporting electrolyte. The areal capacitance of the Ni3N thin film electrode obtained from CV analysis was 319.5 mF cm-2 at a lower scan rate of 10 mV s-1. Meanwhile, the Ni3N thin film showed an excellent cyclic stability and retained 93.7% efficiency of its initial capacitance after 2000 cycles at 100 mV s-1. Interestingly, the DSSCs fabricated with a Ni3N CE showed a notable power energy conversion efficiency of 2.88% and remarkable stability. The prominent performance of the Ni3N thin film was ascribed mainly due to good conductivity, high electrochemically active sites with excellent 3D nano rhombus structures and high electrocatalytic activity. Overall, these results demonstrate that the Ni3N electrode is capable of being considered for efficient SCs and DSSCs. This investigation also offers an essential directive for the advancement of energy storage and conversion devices.

Phase transition and thermal expansion studies of alumina thin films prepared by reactive pulsed laser deposition.

Aluminium oxide (Al2O3) thin films were deposited on Si (100) substrates at an optimized oxygen partial pressure of 3 x 10(-3) mbar at room temperature by pulsed laser deposition (PLD). The films were characterized by high temperature X-ray diffraction (HTXRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The HTXRD pattern showed the cubic y-Al2O3 phase in the temperature range 300-973 K. At temperatures ≥ 1073 K, the δ and θ-phases of Al2O3 were observed. The mean linear thermal expansion coefficient and volume thermal expansion coefficient of γ-Al2O3 was found to be 12.66 x 10(-6) K(-1) and 38.87 x 10(-6) K(-1) in the temperature range 300 K-1073 K. The field emission scanning electron microscopy revealed a smooth and structureless morphology of the films deposited on Si (100). The atomic force microscopy study indicated the increased crystallinity and surface roughness of the films after annealing at high temperature.

Development of a CrN/Cu nanocomposite coating on titanium-modified stainless steel for antibacterial activity against Pseudomonas aeruginosa.

A relatively simple method was developed to fabricate CrN/Cu nanocomposite coatings using pulsed DC magnetron sputtering for application in antibacterial activity. These nanocomposite coatings were applied on titanium (Ti)-modified stainless steel substrata (D-9 alloy) and the antibacterial activity of these coating with respect to the Gram-negative bacterium Pseudomonas aeruginosa was investigated qualitatively and quantitatively. Scanning electron microscopy, epifluorescence microscope analyses, and total viable counts confirmed that inclusion of copper in the CrN/Cu nanocomposite coatings provided antibacterial activity against P. aeruginosa. The quantitative examination of the bacterial activity of P. aeruginosa was estimated by the survival ratio as calculated from the number of viable cells which formed colonies on nutrient agar plates.

X-ray diffraction study of nanocrystalline titania thin films prepared by pulsed laser deposition.

Pulsed laser deposition of phase pure thin films of rutile and anatase from a rutile target is investigated. Rutile films prepared at the base pressure and at < or =473 K were amorphous and the crystalline quality was improved with increasing substrate temperature. The crystallite size was found to vary from 2 nm to 58 nm in the temperature range 573-973 K. Addition of oxygen has been found to be beneficial in promoting the formation of anatase phase even at a temperature of 673 K. From the base pressure to 10(-4) mbar, films were rutile, while at approximately 0.001 mbar, the rutile phase was found to transform to anatase. Rietveld analysis indicated about 20% of anatase and about 80% of rutile phase for the films prepared at 0.001 mbar of oxygen partial pressure. Good quality anatase films were formed at approximately 0.05 mbar, while the films were amorphous at higher partial pressures of oxygen.

Synthesis and properties of ceria thin films prepared by pulsed laser deposition.

Cerium oxide (CeO2) thin films were prepared on (100) Si and glass substrates using pulsed laser ablation at different oxygen partial pressures (2.5 x 10(-5)-3.5 x 10(-1) mbar) and at a substrate temperature of 873 K. XRD studies on the films showed that the films are polycrystalline having fluorite structure. The oxygen partial pressure has a dominant effect on the thickness, crystallite size and preferred orientation of the films. At an oxygen partial pressure of 3.5 x 10(-2) mbar, the intensity of (200) reflection is maximum and film possesses the maximum crystallite size of about 50 nm. Though all the films are highly transparent in the visible region, films prepared at an oxygen partial pressure of 3.5 x 10(-1) mbar, exhibits maximum transmittance (>90% @ 632 nm). The optical band gap is found to decrease from 3.66 to 3.42 eV with the increasing oxygen partial pressure.

A study on the influence of copper content in CrN/Cu nanocomposite thin films prepared by pulsed DC magnetron sputtering.

Synthesis of nanocomposite thin films of CrN/Cu deposited on (100) Si and D-9 alloy substrates by pulsed magnetron sputtering as a function of copper content in the range 15.1-35.8 at.% is investigated. XRD analysis of the films deposited at 773 K with nitrogen flow rate of 10 sccm indicated that the films are nanorystalline and bi-phasic (fcc-CrN and fcc-Cu). Scanning electron microscopy showed a structureless morphology for CrN, while agglomerates were obtained for CrN/Cu nanocomposite thin films. Atomic force microscopy also confirmed the agglomeration of particles with increasing Cu content. The amount of copper content in the nanocomposite films had also shown a significant reduction in the crystallite size of CrN. The nano hardness measurements showed a peak hardness of 17 GPa for the films with copper content of 15.1 at.%. The hardness values were found to decrease significantly with Cu content > 31.1 at.%.

Microstructural studies of nanocomposite thin films of Ni/CrN prepared by reactive magnetron sputtering.

Synthesis and characterization of nanocomposites of Ni/CrN thin films prepared by DC magnetron sputtering from a target of 50 wt.%Ni-50 wt.%Cr is investigated. The films prepared as a function of nitrogen flow rate and substrate temperature showed that the films contained Ni and CrN phases with crystallite sizes in the nanometer range. Measurement of nanomechanical properties of the composite films exhibited a significant decrease in the values of hardness and Young's modulus than those of pure CrN films.