Properties of nanostructured nickel thin films obtained by glancing angle deposition

Istraživanja nanostrukturnih tankih slojeva nikla su od velikog značaja zbog veoma dobrih fizičkih i hemijskih svojstava ovog metala. Nikl je materijal koji ima veliku primjenu u različitim oblastima nauke i tehnologije, zahvaljujući svojstvima kao što su visoka Curie-va temperatura, niska električna otpornost, dobra toplotna provodljivost, otpornost na koroziju, itd...Research of nanostructured nickel thin films is of great importance because of very good physical and chemical properties of this material. Nickel is a material used in various fields of science and technology, due to its properties such as high Curie temperature, low electrical resistivity, good thermal conductivity, corrosion resistance, etc..

Optical properties of zigzag nickel nanostructures obtained at different deposition angles

In this study, nickel (Ni) thin films were deposited at two different angles (65o and 85o) using Glancing Angle Deposition technique, to the thicknesses of 60 – 290 nm. Structural analysis of the deposited films was performed by scanning electron microscopy and X-ray diffraction, while spectroscopic ellipsometry was used for the investigation of optical properties. Electrical resitivity of the samples was determined by four-point probe method. Structural analysis showed that the Ni films grow in a shape of zigzag nanocolumns, where the deposition angle strongly affects their porosity. As the thickness of the films increase they absorb light strongly and become less dense. Besides, samples deposited at the angle of 85o exhibit higher values of electrical resistivity as compared to the samples deposited at the angle of 65o, which can be correlated with high porosity and the growth mechanism of the deposited nanostructures

The Effect of Thickness and Deposition Angle on Structural, Chemical and Magnetic Properties of Nickel Slanted Columns

In this work, the influence of different deposition angles on the structural, chemical and magnetic properties of nickel (Ni) thin films was investigated. Nickel samples were deposited by glancing angle deposition technique at two different angles, 65o and 85o. Characterization of the thin films was carried out by scanning electron microscopy, X-ray photoelectron spectroscopy and magneto-optical Kerr effect microscopy. Structural analysis was found that the changes in the deposition angle have a great influence on the porosity of the film as well as on the amount of the present nickel oxide (NiO) in the samples. On the other hand, we have also found that different deposition angle changes the magnetic response of nickel film. The coercivity of the samples deposited at the angle of 85o is significantly higher compared to the samples deposited at lower angle which could be correlated with the higher porosity and the amount of NiO in the thin films

Electrochemically exfoliated graphene as support of platinum nanoparticles for methanol oxidation reaction and hydrogen evolution reaction

To enhance the utilization efficiency of platinum (Pt) in electrochemical energy conversion, the precise selection of support materials presents a highly promising strategy. We have developed an efficient and stable bifunctional catalyst for methanol oxidation (MOR) and hydrogen evolution (HER) reaction in an alkaline medium. The Pt-based electrocatalyst, denoted as Pt/e-rGO with low Pt loading was successfully synthesized using graphene sheets as the support via chemical reduction using formic acid as the reducing agent. Graphene sheets are obtained by anodic electrochemical exfoliation of graphite tape. Significant enhancement of intrinsic activity toward MOR and HER was achieved for Pt/e-rGO compared to the commercial Pt/C catalyst. Structural characterization was performed by TEM, SEM and XPS. XPS analysis shows that the graphene is highly reduced. TEM analysis unveiled that the majority of the Pt nanoparticles (NPs) exhibit a diameter in the range of 4-5 nanometers, which is significant because the efficiency of electrooxidation of methanol on supported Pt NPs shows a strong dependence on particle size distribution. Catalyst activity was studied by cyclic voltammetry and linear sweep voltammetry in 0.1M KOH. Electrochemical active surface area (ECSA) was measured by CO-stripping voltammetry and estimated to be 67.93 m2 /g. Current density of 11.28 mA/cm2 ECSA at 0.82 V vs. RHE for MOR is achieved. Onset potential for MOR is 0.55 V vs. RHE. Meanwhile, for HER overporential at the current density -10 mA/cm2 ECSA was 119 mV.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Fungicide sensitivity of selected Verticillium fungicola isolates from Agaricus bisporus farms

Five isolates of Verticillium fungicola, isolated from diseased fruiting bodies of Agaricus bisporus collected from mushroom farms in Serbia during 2002-2003, were studied. By observing their colony morphology under different growth conditions and their pathogenic characteristics, the isolates were identified as V. fungicola var. fungicola. The peat/lime casing was the primary source of infection. Testing of sensitivity to selected fungicides showed that all isolates were highly resistant to benomyl (EC50 values were higher than 200.00 mg/l), moderately sensitive to iprodione (EC50 values were between 11.93 and 22.80 mg/l), and highly sensitive to prochloraz-Mn (EC50 values were less than 3.00 mg/l)

Microstructure – Properties relationship in laser-welded AZ31B magnesium alloy

The AZ31B magnesium alloy was laser-welded at three different (1.2, 1.6, and 2 kW) laser output powers in the present work. All the butt weld joints are almost defect-free. The size of the weld joint slightly increases with increasing laser output power. The weld metal is formed by columnar grains of the alpha phase at the weld metal/base metal interface, but a finely equiaxed grain microstructure is formed in the centres of fusion zones. The minor phases are Mg17Al12 and (Al,Mg)8Mn5. The weld metal microstructure manifests clear refinement with a decrease in laser output power. Microstructural changes are reflected in changes in mechanical properties; weld joints prepared at the lowest laser output power manifest the highest microhardness, ultimate tensile strength, yield strength, and almost 90% joint efficiency. This is related to the different extents of strengthening mechanisms that act most effectively in weld joints made at 1.2 kW laser output power. Detail analysis of fracture surfaces confirmed that lower laser output power and general microstructural refinement favours the formation of plastically deformed material, which is in excellent agreement with both the experimentally determined and the calculated values of yield strength

Investigation of Ion Release and Antibacterial Properties of TiN-Cu-Nanocoated Nitinol Archwires

Background: The use of nitinol (NiTi) archwires in orthodontic treatment has increased significantly due to unique mechanical properties. The greatest obstacle for safe orthodontic treatment is chemically or microbiologically induced corrosion, resulting in nickel (Ni) release. The aim of this investigation was to enhance corrosion resistance and introduce antibacterial properties to NiTi archwires by coating them with copper (Cu) doper titanium nitride (TiN-Cu). Methods: NiTi archwires were coated with TiN-Cu using cathodic arc evaporation (CAE) and direct current magnetron sputtering (DC-MS). The morphology of the sample was analyzed via field emission scanning electron microscopy (FESEM) and chemical composition was assessed using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR). Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to estimate the ion release. The biocompatibility of samples was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyl tetrazolium bromide (MTT) assay. Antibacterial activity was tested against Streptococcus mutans and Streptococcus mitis. Results: Physicochemical characterization revealed well-designed coatings with the presence of TiN phase with incorporated Cu. TiN-Cu-nanocoated archwires showed a statistically lower Ni release (p < 0.05). Relative cell viability was the highest in 28-day eluates of TiN-Cu-nanocoated archwires (p < 0.05). The most remarkable decrease in Streptococcus mitis concentrations was observed in the case of TiN-Cu-coated archwires (p < 0.05). Conclusion: Taking into account biocompatibility and antibacterial tests, TiN-Cu-nanocoated archwires may be considered as a good candidate for further clinical investigation

Synthesis temperature influence on the structure, morphology and electrochemical performance of NaxMnO2 as cathode materials for sodium-ion rechearchable batteries

The lithium-ion batteries are the most commonly used for energy storage in portable devices. Since lithium is relatively rare on earth but rapidly consumed, it is necessary to find an adequate replacement. Owing to the similar chemical properties of sodium and lithium, but much higher availability, sodium ion batteries are one of the best candidates to replace lithium-ion batteries. A variety of materials such as manganese oxide, vanadium oxide or phosphate can be used as an electrode material (anode and cathode) in sodium ion batteries due to the high ability of intercalation of sodium. In this work, NaxMnO2 powder was synthesized by glycine nitrate method. The precursor powder was annealed for four hours at different temperatures: 800, 850, 900 and 950 °C. The characterization of the obtained materials was carried out using following methods: X-ray diffraction (XRD), scanning electron spectroscopy with energy dispersive X-ray spectroscopy (SEM/EDS) and transmission electron spectroscopy with energy dispersive Xray spectroscopy (TEM/EDS). Electrochemical properties were studied using cyclic voltammetry and chronopotentiometry in an aqueous solution of NaNO3. The layer structured Na0.7MnO2.05 with sheet-like morphology and Na0.4MnO2 with 3-D tunnel structure and rod-like morphology was obtained at 800 oC and 900 oC respectively. Na0.44MnO2 with rod-like morphology was annealed at 900 and 950 oC. 3D-tunnel structure Na0.44MnO2 obtained at 900 oC showed the best electrochemical behaviour in aqueous NaNO3 solution

Synthesis and characterization of Na0.4MnO2 as cathode material for aqueous sodium-ion batteries

The application of rechargeable batteries is growing significantly and there is a need for developing cheaper batteries with good performances. Sodium-ion batteries could be a viable option due to higher abundance of sodium against lithium mineral resources, its low price and similar principles intercalate Na+ ions as Li+ ions in lithium-ion batteries. Different materials as manganese oxides and vanadium oxide are used as electrode materials in sodium batteries. Na0.44MnO2 was regarded as one of the most promising cathode materials for sodium-ion batteries due to its high specific capacity and good cyclability. In this work, Na0.4MnO2 was synthesized using glycine-nitrate method (GNM). The structure of synthesized powder was characterized by X-Ray Diffraction (XRD), while the particles morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elemental mapping was performed by energy-dispersive Xray spectroscopy (EDS). XRD results showed that the phase structure of Na0.4MnO2 was orthorhombic with tunnel structure. TEM and SEM micrographs of obtained powder material showed uniformed rod-like shape particles with the average lengths and widths of 300 nm and 80 nm, respectively and EDS analysis confirmed that the sample contains Na, Mn, and O in an appropriate ration. The electrochemical behavior of Na0.4MnO2 was investigated by cyclic voltammetry (CV) in a saturated aqueous solution of NaNO3 at scan rates from 20 to 400 mV•s-1. The initial discharge capacity of Na0.4MnO2 in NaNO3 solution was 50 mA•h•g- 1, while after 15 cycles its value increased for 9%. while the efficiency (the ratio of the capacity charge and discharge) was amounting to ~ 95%. This indicates that material synthesized by GNM can be used as cathode material in aqueous sodium-ion batterie

Hydrogen evolution reaction on bimetallic Ir/Pt(poly) electrodes in alkaline solution

Hydrogen evolution reaction (HER) was studied in alkaline solution on Pt(poly) electrode modified by spontaneously deposited Ir nanoislands. Comprehensive insight into the characteristics of the bimetallic Ir/Pt(poly) catalysts was obtained by a combination of Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS) and classical electrochemical techniques. HER investigations have shown that the presence of spontaneously deposited Ir enhances the activity of bare Pt(poly) in alkaline solution. This was attributed to the heterogeneity of the active surface sites and to the electronic interaction between two metals in close contact which together facilitated the adsorption of the H intermediate species.This is peer-reviewed version of the article: Svetlana Štrbac, Milutin Smiljanić, Thomas Wakelin, Jelena Potočnik, Zlatko Rakočević, Hydrogen evolution reaction on bimetallic Ir/Pt(poly) electrodes in alkaline solution, Electrochimica Acta (2019), [https://dx.doi.org/10.1016/j.electacta.2019.03.100][http://cer.ihtm.bg.ac.rs/handle/123456789/2951