Papers by Keyword: Nickel

Abstract: This study proposes a simple method for fabricating metal particles. Metal nanoparticles are synthesized in an aqueous solution. The synthesis method is based on the galvanic replacement of one metal with another, i.e., the deposition of a metal on the surface of another metal using difference between the standard electrode potentials of the metals under ultrasonication. An aqueous colloidal solution of metallic copper (Cu) nanoparticles is prepared using Cu acetate and a metallic zinc (Zn) plate. A similar colloidal solution of metallic Cu nanoparticles is prepared using Cu acetate and a metallic iron plate. No metallic nanoparticles are obtained using metallic aluminum and nickel (Ni) plates because of the formation of passivated layers. An aqueous colloidal solution of metallic Ni nanoparticles is prepared using Ni acetate and a metallic Zn plate; however, Ni_0.7Zn_0.3O is also formed. The results of the study show that the proposed method can be used to produce metallic particles in a simple manner.

Abstract: This research aims to synthesize and characterize Ni(II)-terephthalate-pyrazine complex and to determine the thermal stability and porosity profile of the synthesized compound. The Ni(II)-terephthalate-pyrazine was made by solvothermal reaction using dimethylformamide at 130 and 150 °C and in Ni(II):terephthalic-acid:pyrazine mol ratios of 1:1:2 and 1:1:4. The precipitated products were characterized by infrared spectroscopy, SEM, and powder-XRD in order to confirm the presence of both ligand in the synthesized compound. Meanwhile, the thermal stability and porosity profile of the synthesized compound were determined by DTA-TGA and surface area analysers, respectively. Experimental data shows that green pale powder was obtained from all reactions in considerably good yield, which is different from the dark green crystalline solid of Ni(II)-terephthalate. SEM image reveals that the product has a smooth-wavy surface morphology. Infrared spectra of the synthesized compound show peaks of functional groups of C=O, C–O, C=N, and C–N groups, which confirm the presence of both ligands. Powder XRD analysis suggests that the crystal system of the synthesized compound is different from that of the Ni(II)-terephthalate. Based on these analyses, the targeted Ni(II)-terephthalate-pyrazine is successfully obtained. Moreover, the synthesized compound has lower thermal stability than that of Ni(II)-terephthalate, while the BET calculation suggest that the synthesized compound has pore volume of 0.10-0.14 cm³/g, pore diameter of 8.1-10.65 nm and surface area of 24-30 (m²/g). This porosity profile suggest that the synthesized compound is open for further application, such as adsorption or photocatalysis.

Abstract: Single crystal of [Ni(4-AP)₄(NCS)₂] complex compound has been obtained using solvothermal method at 70 °C for 15 hours (yield = 41%). Crystal structure of [Ni(4-AP)₄(NCS)₂] has a distorted octahedral structure with orthorhombic crystal system, Pccn space group, Z = 4, and a, b, and c values of 17.1091(5) Å, 9.6686 (3) Å, 16.1998 (5) Å. Hirshfeld Surface analysis shows that intermolecular hydrogen bonds in the complex compound comes from N–H∙∙∙∙N and N–H∙∙∙∙S. The intermolecular interactions are dominated by H---H, C---H/H---C, and H---S/S---H by 39.0%, 29.6%, and 24.7%, respectively. The relatively less contributions are N---H/H---N, S---C/C---S, and S---N/N---S at 6.3%, 0.2%, and 0.1%, respectively. The [Ni(4-AP)₄(NCS)₂] complex has antibacterial activity against Escherichia coli and Staphylococcus aureus.

Abstract: Laser Thermal Annealing (LTA) is a key process step to improve the 4H-SiC devices by reducing their on-state resistance. In this study, we investigate the electrical, structural and morphological properties of nickel contact fabricated by LTA. A contact formed by a classical Rapid Thermal Annealing (RTA) was also fabricated as reference. Based on structural analysis, the phases formed by LTA do not match with RTA sample ones that has better ohmic properties. Nevertheless, the LTA contacts reach a specific contact resistance of 2.4×10^-5 Ω.cm² for an annealing at 4.75 J.cm^‑2, which represents a significant improvement in comparison with our previous contacts fabricated with the same experimental protocol using titanium.

Abstract: In this work, an empirical model of structural and material composition of low-ohmic nickel silicide contact formation on n-type 4H-SiC by laser annealing as well as by RTA is presented. For this purpose, systematic studies with different annealing parameters were performed. The development of the empirical model is based on results from characterization of the nickel silicide by FIB-SEM, TEM, XRD analysis as well as electrical characteristics received from 4-point-measurements.

Abstract: In this work, the influence of different surface roughness and surface treatments on the minimum energy density required to form low-ohmic nickel contacts on n-type 4H-SiC by laser annealing was investigated. The annealing was performed by a frequency-tripled Nd:YVO₄ laser with a pulse duration of 50 ns. To evaluate the effects, the grinded or polished C-side of 4H-SiC wafers with surface roughness between 0.3 and 70 nm was sputter-deposited with nickel and subsequent laser annealed. Sheet resistance measurements showed that the minimum energy density required to achieve a low-resistance contact depends significantly on the surface roughness. The rougher the surface, the lower the minimum energy density to form a low-ohmic contact.

Abstract: Solid-state diffusion bonding effectively joins dissimilar materials, even with varying metallurgical properties and melting points. In this study, a Cu/Ni joint was produced at a bonding temperature of 950°C for 60 minutes under a vacuum. The microstructural and mechanical properties of the bonding interface were evaluated using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), microhardness tests, and X-ray diffraction (XRD). It was found that the EDS point scan analysis revealed the formation of a solid solution of Cu-Ni at the bonding interface. Since Cu-Ni exhibit complete solubility with each other, no intermetallic compounds (IMCs) were formed. The microhardness indicated that the bonding interface had a microhardness of 20% and 54% higher than the base metals (BM) of Ni and Cu, respectively.

Abstract: The adsorption of nickel (II) ions by natural zeolites of the Sokirnitskoe (Transcar-pathia, Ukraine) and Kholinskoye (Eastern Transbaikalia, Russia) deposits has been studied. According to X-ray phase analysis data, the zeolite-containing sample of the Sokirnitskoe deposit contains at least 75 wt. % clinoptilolite and impurity rock - quartz SiO₂. The sample of the Kholinskoye deposit consists of heulandite (not less than 75 wt. %), as well as an impurity rock - potassium spar KAlSi₃O₈. The assessment of the ad-sorption capacity of zeolites with respect to nickel (II) ions was carried out on the basis of the analysis of adsorption isotherms. The pH of the medium of the studied aqueous solutions was 5.5–5.8. The value of ad-sorption of nickel (II) ions by heulandite is twice that for clinoptilolite and amounts to 0.104 mmol/L. The adsorption of nickel (II) ions was investigated using the Langmuir, Freundlich and Dubinin-Radushkevich models. On the basis of the Dubinin-Radushkevich adsorption model, the values of the free energy of adsorption are determined. That indicates the physical nature of the interaction of the adsorptive and the adsorbent, in the case of the zeolite of the Sokirnitskoe deposit. It is shown that the adsorption of nickel (II) ions by the zeolite of the Kholinskoye deposit proceeds according to the ion-exchange mechanism. This explains the higher adsorption values of nickel (II) ions by this sample.

Abstract: We study ultrafast magnetization dynamics induced by laser heating using various phenomenological temperature models. The temperature dynamics of the electrons, spins and lattice for thin foils is investigated. Numerical results for the temperature and magnetization dynamics for them are compared with those available in the literature.

Abstract: The increment of pilot plant waste at UniKL MICET and eggshell waste cause disposal problems, such as the water and soil pollution, human health concerns, and disruption to aquatic ecosystems. Thus, to reduce the effect of disposal problem to the environment, pilot plant waste is converted into biodiesel, while eggshell is converted into catalyst in this study. This paper reports on the effect of catalyst preparation method and reaction temperature on biodiesel yield and quality. Transesterification process of pilot plant waste (olein and stearin) was conducted by using Ni/CaO (eggshell) catalyst from different preparation methods at different reaction temperatures (328 K, 333 K, 338 K and constant reaction time (5 hours), methanol-to-oil ratio (15:1), and weight of catalyst (8 wt%). The catalysts were synthesized via wet impregnation and sol–gel method and its physicochemical properties were subsequently characterized by TGA and FTIR analysis. Biodiesel analysis was done using GCMS and FTIR, while the physical properties (density, flash point, and kinematic viscosity) of biodiesel were measured according to ASTM D6751. Kissinger-Akahira-Sunose (KAS) kinetic model shows that the catalyst prepared by wet impregnation method has the lowest activation energy, which was 81.48 kJ mol^–1. In addition, GCMS analysis shows that reaction temperature at 338 K produced the highest yield of biodiesel (88.26%). In conclusion, the best catalyst preparation method was wet impregnation method and the best reaction temperature was 338 K. In addition, the physical properties of the produced biodiesel corresponded to ASTM standard, thereby indicating high quality of biodiesel and can be used as petroleum-diesel substitute.