Advances in Nickel Nanoparticle Synthesis via Oleylamine Route

Silver Shell Thickness-Dependent Conductivity of Coatings Based on Ni@Ag Core@shell Nanoparticles

Introductions

Ink based on metallic nanoparticles has been widely used so far for the fabrication of electronic circuits and devices using printing technology. This study aimed at the analysis of the effect of the silver shell thickness of nickel@silver core@shell (Ni@Ag) nanoparticles (NPs) on the fabrication and conductive properties of deposited coatings.

Methods

The process of the synthesis of Ni@Ag NPs with various silver shell thicknesses was developed. The physicochemical properties (size, stability against aggregation process) of synthesized Ni@Ag nanoparticles were analyzed. The films based on ink containing Ni@Ag NPs with different silver shell thicknesses were fabricated and sintered in a temperature range of 120-300 °C and at times from 15 to 90 min. The dependence of their conductive properties on the applied temperature and time as well as silver shell thickness was evaluated.

Results

Ni NPs were coated with 10, 20, 30, 35, 45, and 55 nm silver shell thickness. The resistivity of coatings based on obtained NPs depends on the thickness of the Ag shell and the sintering temperature. After sintering at 300 °C, the highest decrease in its value (at an optimal sintering time of 60 min) from about 100 µΩ·cm to 9 µΩ·cm was observed when the thickness of the shell increased from 10 to 55 nm. At the lowest sintering temperature (120 °C) the highest conductivity (about 50% of that for bulk nickel) was obtained for films based on Ni@Ag NPs with 45 and 55 nm of the silver shell thickness.

Discussions

The analysis of the resistivity of the sintered films showed that higher conductivity was obtained for the coatings formed from Ni@Ag NPs with the thicker Ag shell; moreover, thicker shells allowed a lowering of sintering temperature due to higher conductivity and a lower melting point of silver in comparison to nickel NPs.

Air-Stable Ni Catalysts Prepared by Liquid-Phase Reduction Using Hydrosilanes for Reactions with Hydrogen

The liquid-phase reduction method for the preparation of metal nanoparticles (NPs) by the reduction of metal salts or metal complexes in a solvent with a reducing agent is widely used to prepare Ni NPs that exhibit high catalytic activity in various organic transformations. Intensive research has been conducted on control of the morphology and size of Ni NPs by the addition of polymers and long-chain compounds as protective agents; however, these agents typically cause a decrease in catalytic activity. Here, we report on the preparation of Ni NPs using hydrosilane (Ni-Si) as a reducing agent and a size-controlling agent. The substituents on silicon can control not only the size but also the crystal phase of the Ni NPs. The prepared Ni NPs exhibited high catalytic performance for the hydrogenation of unsaturated compounds, aromatics, and heteroaromatics to give the corresponding hydrogenated products in high yields. The unique feature of Ni catalysts prepared by the hydrosilane-assisted method is that the catalysts can be handled under air as opposed to conventional Ni catalysts such as Raney Ni. Characterization studies indicated that the surface hydroxide was reduced under the catalytic reaction conditions with H2 at around 100 °C and with the assistance of organosilicon compounds deposited on the catalyst surface. The hydrosilane-assisted method presented here could be applied to the preparation of supported Ni catalysts (Ni-Si/support). The interaction between the Ni NPs and a metal oxide support enabled the direct amination of alcohols with ammonia to afford the primary amine selectively.

A review on the recent progress, opportunities, and challenges of 4D printing and bioprinting in regenerative medicine

Four-dimensional (4 D) printing is a novel emerging technology, which can be defined as the ability of 3 D printed materials to change their form and functions. The term 'time' is added to 3 D printing as the fourth dimension, in which materials can respond to a stimulus after finishing the manufacturing process. 4 D printing provides more versatility in terms of size, shape, and structure after printing the construct. Complex material programmability, multi-material printing, and precise structure design are the essential requirements of 4 D printing systems. The utilization of stimuli-responsive polymers has increasingly taken the place of cell traction force-dependent methods and manual folding, offering a more advanced technique to affect a construct's adjusted shape transformation. The present review highlights the concept of 4 D printing and the responsive bioinks used in 4 D printing, such as water-responsive, pH-responsive, thermo-responsive, and light-responsive materials used in tissue regeneration. Cell traction force methods are described as well. Finally, this paper aims to introduce the limitations and future trends of 4 D printing in biomedical applications based on selected key references from the last decade.

Computational Framework of Magnetized MgO-Ni/Water-Based Stagnation Nanoflow Past an Elastic Stretching Surface: Application in Solar Energy Coatings

In this article, motivated by novel nanofluid solar energy coating systems, a mathematical model of hybrid magnesium oxide (MgO) and nickel (Ni) nanofluid magnetohydrodynamic (MHD) stagnation point flow impinging on a porous elastic stretching surface in a porous medium is developed. The hybrid nanofluid is electrically conducted, and a magnetic Reynolds number is sufficiently large enough to invoke an induced magnetic field. A Darcy model is adopted for the isotropic, homogenous porous medium. The boundary conditions account for the impacts of the velocity slip and thermal slip. Heat generation (source)/absorption (sink) and also viscous dissipation effects are included. The mathematical formulation has been performed with the help of similarity variables, and the resulting coupled nonlinear dimensionless ordinary differential equations have been solved numerically with the help of the shooting method. In order to test the validity of the current results and the convergence of the solutions, a numerical comparison with previously published results is included. Numerical results are plotted for the effect of emerging parameters on velocity, temperature, magnetic induction, skin friction, and Nusselt number. With an increment in nanoparticle volume fraction of both MgO and Ni nanoparticles, the temperature and thermal boundary layer thickness of the nanofluid are elevated. An increase in the porous medium parameter (Darcy number), velocity slip, and thermal Grashof number all enhance the induced magnetic field. Initial increments in the nanoparticle volume fraction for both MgO and Ni suppress the magnetic induction near the wall, although, subsequently, when further from the wall, this effect is reversed. Temperature is enhanced with heat generation, whereas it is depleted with heat absorption and thermal slip effects. Overall, excellent thermal enhancement is achieved by the hybrid nanofluid.

A low temperature organic synthesis of monodispersed NiRu nanocrystals for CO2 methanation

In this study, monodispersed NiRu nanocrystals with a diameter of 3 nm were synthesized at 90 °C via a tuning hot-inject method to lower the temperature of the organic phase synthesis of monodispersed nanomaterials. The key factor for the nanocrystalline formation of NiRu alloy nanocrystals was summarized in detail. Simultaneously, the synergistic effect of Ni and Ru in CO2 methanation was explored. Doping trace Ru can significantly improve the conversion rate of CO2 methanation and CH4 selectivity. The underlying mechanism was studied in detail via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed hydrogen reduction (H2-TPR) and desorption (H2-TPD) tests, and temperature-programmed desorption of CO2 (CO2-TPD). This study gives out a new way for the general synthesis of monodisperse nickel-based nanocrystals and provides a reference for the development and application of monodispersed nanoparticles for CO2 methanation.