Abdul Faheem Khan

Investigation of the mechanical properties of electrodeposited nickel and magnetron sputtered chromium nitride coatings deposited on mild steel substrate

Abstract Electrodeposition and magnetron sputtering techniques have been employed for the deposition of Ni and bilayer NiCrN coatings, respectively, on mild steel substrate. Ni electrodeposition was performed using sulfate Watt’s bath, while magnetron sputtering was performed on electrodeposited Ni using DC power 350 W and base pressure of 3 × 10−5 Torr in order to prepare bilayer NiCrN coatings. Structural and mechanical properties of Ni and bilayer NiCrN coatings have been investigated using various characterization techniques such as SEM-EDX, XRD, hardness, adhesion testing, etc. SEM analysis reflects the formation of spherical/nodular particles of varying sizes in NiCrN coating whereas Ni coating shows irregular, agglomerated, and non-uniform distribution of particles. Formation of hard CrN phase in NiCrN coating has been confirmed by XRD and EDX. NiCrN coating exhibits better hardness in comparison with Ni coating due to the formation of nitride phase. Micro scratch testing of bilayer NiCrN coating shows better interlayer adhesion and adhesion with mild steel substrate. The combination of electrodeposition and magnetron sputtering can produce inexpensive NiCrN coating containing hard CrN phase with better mechanical properties for automotive applications.

Structural and mechanical properties of (Cr, Ni) N single and gradient layer coatings deposited on mild steel by magnetron sputtering

Ternary single and gradient layer (Cr, Ni) N thin films were deposited on the mild steel substrate by unbalanced magnetron sputtering technique in order to evaluate mechanical properties for machine tools and automotive applications. Microstructure, chemical composition, surface morphology and phase analysis were carried out using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction, respectively. Both single and gradient layer of (Cr, Ni) N coatings show a significant increment in mechanical properties such as hardness, adhesion strength and surface roughness along with the reduction of friction coefficient. Mechanical tests revealed that the hardness of the gradient layer increased up to 3.1 times due to the formation of Cr2N and Ni phase whereas single layer showed the least friction. Single layer CrNiN layer exhibited 27.2% less surface roughness (Ra) in comparison with gradient layer. High values of surface roughness, hardness, thickness and friction could be correlated with high film-to-substrate adhesion (Lc2) for the gradient layer.

Gamma irradiation-Induced chemical decomposition related bandgap engineering in SnO2 nanoparticles

Gamma irradiation-induced chemical decomposition and related phase transformation from SnO2 nanoparticles (NPs) to SnO have been studied using X-ray diffraction (XRD), Raman spectroscopy, transmiss...

STUDY OF Co/Sn MULTILAYER SYSTEM WITH VARIOUS TIN LAYER THICKNESS AND REFLOW TEMPERATURES

Co–Sn–Co multi-layer films with various Sn-layer thicknesses have been deposited by using the electrodeposition technique. The deposition was performed at room temperature on gold coated silicon substrates. The thickness of Sn layer was kept ∼4.5, 2.5, 1.5 and 1μm, while the thickness of each Co layer was fixed to ∼0.75μm. The Sn layer was sandwiched between two Co layers. The total thickness of the films was ∼6, 4, 3, 2.5μm, respectively. The intended ratio of Sn was about 25 at.% while Co was about 75 at.%. The separation inside the Sn-layer has been observed at higher Sn-layer thicknesses with increasing reflow temperature. It may be due to the combined effect of thermal stress arising during cooling from elevated reflow temperatures and solidification shrinkage in the thick Sn layer due to the formation of IMC CoSn2. However, 1μm has been found to be a critical thickness, which remains intact when sandwiched between two cobalt layers. The structure of these multi-layer films was studied as a function of temperature. It has been observed from X-ray diffraction (XRD) that the as-deposited films exhibit strong peaks belonging to elemental Co and Sn. At temperatures of 270–290∘C, CoSn2 begins to appear and grow at the interfaces and in the middle of Sn layer with the decrease in elemental Sn. However, sufficient amount of Co is still present in pure form as is evident by the XRD and field emission scanning electron microscopy images at all temperatures. This study confirms that only one reaction product, viz. CoSn2, formed in as-deposited during reflow at temperatures 270–290∘C for a fixed time of 10min, although several other stable IMCs, e.g. Co3Sn2, CoSn, CoSn2, CoSn3 exist in the Co–Sn system at 250∘C according to phase diagram. It is not uncommon that all the thermodynamically stable IMCs do not form in the system due to kinetic reasons. Accordingly, the formation of IMCs through interfacial reaction has been discussed in this paper.

Nanostructured SnO2-Ge Multi-layer thin Films with Quantum Confinement Effects for Solar Cell.

BACKGROUND It is well-known that multi-layer films with nanostructure can give novel properties by interfacial phenomenon and quantum confinement effects. Nanostructured multi-layer thin films are presently being analyzed for their vast applications in the area of optoelectronics technology particularly photovoltaics. Hereof, two dimensional thin films with nanostructure are of prime importance due to their structure dependent optical, electrical, and opto-electronic properties. It has been revealed that these films exhibit quantum confinement effects with band gap engineering. The main focus of the research is to evaluate the effect on structural and optical properties with number of layers. METHODS Nanostructured SnO2-Ge multi-layer thin films were fabricated using electron beam evaporation and resistive heating techniques. Alternate layers of SnO2 and Ge were deposited on glass substrate at a substrate temperature of 300 °C in order to obtain uniform and homogeneous deposition. The substrate temperature of 300 °C has been determined to be effective for the deposition of these multi-layer films from our previous studies. The films were characterized by investigating their structural and optical properties. The structural properties of the as-deposited films were characterized by Rutherford Backscattering Spectroscopy (RBS) and Raman spectroscopy and optical properties by Ultra-Violet-Near infrared (UV-VIS-NIR) spectroscopy. RESULTS RBS studies confirmed that the layer structure has been effectively formed. Raman spectroscopy results show that the peaks of both Ge and SnO2 shifts towards lower wavenumbers (in comparison with bulk Ge and SnO2, suggesting that the films consist of nanostructures and demonstrate quantum confinement effects. UV-VIS-NIR spectroscopy showed an increase in the band gap energy of Ge and SnO2 and shifting of transmittance curves toward higher wavelength by increasing the number of layers. The band gap lies in the range of 0.9 to 1.2 eV for Ge, while for SnO2, it lies between 1.7 to 2.1 eV. CONCLUSION Analysis of results suggests that the nanostructured SnO2-Ge multi-layer thin film can work as heterojunction materials with quantum confinement effects. Accordingly, the present SnO2-Ge multi-layer films may be employed for photovoltaic applications. Few relevant patents to the topic have been reviewed and cited.