Nickel Nanopowders Research Articles

STUDY OF THE COMBINED EFFECT OF POST-SYNTHETIC ALKALINE TREATMENT AND NICKEL MODIFICATION OF MFI ZEOLITE ON THE DYNAMICS OF ITS DEACTIVATION IN THE PROCESS OF REFINING STRAIGHT-RUN GASOLINE

To determine the combined effect of post-synthetic treatments on the catalytic properties of MFI type zeolite (other names ZSM-5 or pentasil) during the upgrading of straight-run gasoline fraction of oil, MFI zeolite was synthesized and on its basis a sample was obtained, treated with an alkaline solution, as well as a nickel-containing sample after alkaline treatment of the zeolite. Modification of zeolite powder treated with an alkaline solution with nanosized nickel powder was carried out by dry mechanical mixing of the original powders in a vibrating mill. The activity and dynamics of deactivation of the obtained zeolite catalysts during the upgrading of straight-run gasoline fraction of oil were studied. Along with determining the characteristics of the target reaction products - high-octane gasoline, an analysis of the resulting gaseous hydrocarbons was carried out and the amount of carbon compaction products was determined. It has been shown that post-synthetic treatments of zeolite have a positive effect on the qualitative composition and yield of catalysates and reduce the rate of deactivation of zeolite catalysts. Post-synthetic alkaline treatment of MFI zeolite significantly reduces its aromatizing and cracking activity, resulting in an increased yield of high-octane gasoline with improved environmental characteristics. The introduction of nickel nanopowder into alkali-treated zeolite further enhances this tendency. Carrying out post-synthetic treatments of zeolite increases the time of stable operation of the resulting zeolite systems in the process of upgrading straight-run gasoline and reduces the amount of carbon compaction products formed. The state, location and dimensions of the zeolite carrier, nickel particles and carbon compaction products were determined using the transmission electron microscopy method. It has been shown that oxidative regeneration of a carbonized catalyst makes it possible to almost completely remove the resulting carbon deposits from the surface of both the active component and the zeolite support. For citation: Velichkina L.M., Gerasimov E.Yu., Vosmerikov A.V. Study of the combined effect of post-synthetic alkaline treatment and nickel modification of MFI zeolite on the dynamics of its deactivation in the process of refining straight-run gasoline. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 103-112. DOI: 10.6060/ivkkt.20246708.10t.

Oxide coated nickel powder as support for platinum(0) nanoparticles: Magnetically separable catalysts for hydrogen generation from the hydrolysis of ammonia borane

We report the development of a novel method for the preparation of magnetically separable platinum nanoparticles. Magnetic nickel nanopowder is initially synthesized in a radiofrequency plasma reactor where in-line passivation was carried out with oxygen gas, resulting in the formation of nickel oxidecoated nickel particles. Following this, platinum nanoparticles are deposited onto the surface of the oxidecoated nickel nanopowder, forming Pt0/Ni@NiO nanocatalysts for the hydrolytic dehydrogenation of ammonia borane. The Pt0/Ni@NiO nanoparticles, containing 0.24 % wt. Pt, exhibit remarkable catalytic activity in the hydrolytic dehydrogenation of ammonia borane, with a turnover frequency of 468 (mol H2)×(mol Pt)−1×min−1 for releasing 3 equivalent H2 gas per mole of ammonia borane from its hydrolysis at 25 ºC. This heightened catalytic activity of Pt0/Ni@NiO nanoparticles is attributed to the favorable metal-support interaction between the platinum(0) nanoparticles and oxide surface, namely the bonding of platinum to the oxide surface, as elucidated by the XPS analysis. More importantly, Pt0/Ni@NiO nanoparticles can be separated from the reaction solution by using an external magnet.

Dynamic compaction of nickel nanopowders: Experiment and MD simulation using the laser shock method

In this paper, a method of dynamic compaction of nanopowders by laser shock is proposed, which is suitable for the compaction of micro-parts with the advantage of high strain rate and controllability. The effect of pre-pressure and laser energy on the mechanical properties and microstructural characteristics of nickel compacts were analysed experimentally. The results indicate a progressive improvement in the mechanical properties of nickel billets with increasing prepressure and laser energy. Notably, under the prepressure of 3 GPa and laser energy of 1.8 J, dense nickel compacts were achieved with the relative density of 94.45% and the microhardness of 170–240 Hv. Molecular dynamics simulation reveals that at a certain pressure threshold, plastic deformation, lattice modification, and dislocation slip occur among nanoparticles, causing strain hardening and a gradual increase in relative density. Furthermore, nanoparticle size inversely correlates with the compaction pressure. The main bonding mechanism of particles is cold welding.

Determination of the porosity characteristics by pycnometric methods

Data on pore size distribution in solids are obtained by pycnometric density-based methods for measuring the pore structure of materials. The results of measuring open porosity by weighing a dry sample followed by evacuation and saturation with distilled water at atmospheric pressure, impregnation with water under pressure using a hydrostat and mercury porosimetry are presented. The samples of porous nickel obtained using powder technology by sintering of the compacts from mixtures of nickel nanopowder with powder ammonium bicarbonate NH4HCO3 (a blowing agent), the volume fractions of which were 80 and 20%, respectively, were studied. A powder blowing agent with a particle size of 63 – 125, 140 – 200, and 250 – 315 μm was used. A theoretical estimation of the pore size available for the penetration of the impregnating liquid was carried out for three methods used for the determination of open porosity. It is shown that upon water saturation after evacuation the liquid can penetrate only into pores larger than 3 μm. Moreover, in porous structures with a large fraction of submicron pores, the actual values of the open porosity are significantly underestimated when using the method of saturation with distilled water after evacuation. The higher the fraction of fine pores in the material, the lower the open porosity value. The difference between the open porosity values determined by methods of water impregnation using a hydrostat and mercury porosimetry was negligible. It has been established that among three considered methods for measuring open porosity, only the method of saturation with distilled water after evacuation cannot be used in analysis of structures with submicron pores. The results obtained can be used to develop porous functional materials and products with a given porosity structure.

Effect of porosity on rapid dynamic compaction of nickel nanopowder.

The shock-loading behavior of nanomaterials requires careful investigation because these complex systems are widely used in environments subjected to impulsive loads. Planar plate impact experiments are conducted to study shock compaction waves in 94% porous nickel powder containing spherical ∼55 nm particles in the pressure and strain rate ranges of 0.1-0.4 GPa and 106-107 s-1, respectively. The distinct two-step structure of these waves is captured by a laser velocimetry technique with high time resolution. This structure is caused by the formation of faster precursor waves traveling ahead of main compaction waves. The complexity of the shock Hugoniot curve of the tested nanomaterial is described using the obtained two-wave data and earlier results for higher pressures. The effect of initial porosity on the fronts of both waves and compressed states behind them is demonstrated using the current data and those that were collected previously for 50% porous samples of similar nanopowder.

Porosity of Nickel Nanopowder Compacts Consolidated by Gas Extrusion

Porosity of Nickel Nanopowder Compacts Consolidated by Gas Extrusion

In English

The preparation of ceramic composites based on metal nanopowders allows us to change significantly the thermal characteristics of the ceramic matrix, which is important for the creation of heat-conducting ceramics technology. The work establishes the most efficient method of obtaining nickel nanopowder on a “P-5848” potentiostat by electrolysis of nickel sulfate (NiSO4) with the addition of boric acid (H3BO3), thiourea ((NH4)2CS) and nickel(II) chloride (NiCl2). The synthesis of Ni nanopowder was carried out at a current density from 1.0 to 3.3 A/dm2 and at a temperature of 45–65 °C, where a platinum (Pt) plate was chosen as an anode, and the cathode was specially made of especially pure aluminum (Al). The results of the study showed the synthesis of Ni nanopowder with a size of 55 nm in the form of thin scales. Electrochemical reactions at the cathode and anode are also considered in the work. Several successful experiments were also carried out in the work, which made it possible to develop an economically profitable technology for the synthesis of copper nanopowder by the electrolysis method at 13.3 ampere-hours of current per 1 dm2 of the anode surface at a relatively low temperature of the copper sulfate solution (CuSO4). Copper nanopowder is removed to the bottom of the bath from the anode by impact shaking. An equally successful experiment was carried out, where the cathode was in the form of several copper plates at the distance of 0.8 cm from each other with a voltage between them of 0.775 V, and a current density of 15.3 A/dm2 at the temperature of 54 °С in an electrolyte with 45 % H2SO4, 8 % Na2SO4 and 4 % CuSO4. The work contains tables with initial and final data of all experiments on the synthesis of nanopowders by the electrolysis method.

Effect of metal coating on physicochemical properties of ceramic foam for flame suppression application

Combustible dust may result in a catastrophic dust explosion with much larger accident consequences than gas explosions. In this study, porous materials are explored as a promising solution for mitigating explosions. This study focussed on the investigation of aluminium powder explosion in the influence of ceramic foam, with and without coating with non-precious nickel nanopowders. The microscopic properties and structural characteristics of the ceramic foam were analyzed using X-ray spectroscopy, X-ray diffractometry, and scanning electron microscopy. The findings revealed that the nickel-coated ceramic foams are non-uniform and almost spherical in shape, with obvious agglomerations of metallic-silica present on the strut structure. Compared to non-coated ceramic, it can be said that nickel-coated ceramic foams demonstrate a significant reduction in maximum overpressure by approximately 10%. This suggests that the interconnected micro-network structure of the nickel-ceramic walls aids in quenching the flame of the aluminium dust explosion and hence, suppressing the overpressure.

A comparative study on the influence of heating modes on the properties of cobalt and nickel nanopowders produced by the chemical-metallurgy method

The effect of heating modes on the properties of Co and Ni nanopowders obtained by the chemical-metallurgy method was compared. It was shown that all established heating modes (isothermal, non-isothermal and mixed) ensure the production of Co and Ni nanopowders with an average size of less than 100 nm, while the mixed regime makes it possible to obtain reduction products with the best characteristics in terms of dispersion and morphology.

Пористость консолидированных методом газовой экструзии компактов из никелевых нанопорошков

The method of hot gas extrusion differs from other methods of metal pressure treatment in that the processed material is subjected to intense plastic deformation by extrusion under conditions of high isostatic pressure of inert gas and heating in the area of plastic deformation. The method makes it possible to process powder materials, while inevitably there is a need to control mechanical properties by controlling porosity and pressure inside the pores. The paper presents a method for calculating the pressure inside the pores from the minimum size of the closed pore. The pore pressure was evaluated on materials obtained by the consolidation of nickel nanopowders by hot gas extrusion. Quantitative processing of the material cross-section view images obtained by scanning electron microscopy showed that the minimum pore size is 220 nm. The formula for calculating the pore pressure is derived from the formula for calculating the critical pore radius. It takes into account the external impact pressure (the gas pressure during the extrusion process was equal to 400 MPa), the surface tension coefficient and the yield strength of nickel (at the extrusion start temperature of 910 °С), as well as the minimum pore radius. The proposed method for calculating the pressure inside a closed pore will allow us to evaluate the mechanical properties of materials obtained by various methods of powder metallurgy.

Molecular-Dynamical Investigation of Thermomechanical Properties of Spherical Solid and Hollow Nickel Nanopowder during Laser Additive Manufacturing Process

Molecular dynamics (MD) simulation with the embedded-atom method (EAM)/alloy potential is used to investigate the property of the nanoscale hollow spherical Nickel (Ni) powder during the laser additive manufacturing (AM) process. The thermomechanical properties of the Ni nanopowder is also explored (1) at room temperature and (2) from room temperature to the melting temperature during laser AM of powder bed fusion. As a result, the optimum parameters for the laser AM process are proposed. The optimal coalescence temperature of the nanoscale hollow spherical Ni powder is in the range between 980 and 1421K, while the melting temperature is in the range between 1320 and 1470 K. The coalescence and melting temperatures are lower than the melting point of Ni (1728 K).

Ultrafast sodium-ion storage in an interconnected Ni/Ni3S2 nanocomposite with long-term cycling performance

Nickel sulfide (Ni3S2) is a potential anode candidate for sodium-ion batteries due to its abundance, stable structure, and low price. However, its rate and cycling performance require improvement for practical applications. This paper reports the facile synthesis of a unique composite consisting of an interconnected nickel/nickel sulfide nanocomposite (Ni/Ni3S2) by heating a mixture of nickel nanopowder and sulfur. The interconnected nanostructured backbone of the nickel nanoparticles facilitates continuous electron pathways in the composite, while the embedded nanosized nickel sulfide domain reduces the diffusion length and improves reaction kinetics. The Ni/Ni3S2 electrode exhibits excellent rate performance in dimethyl ether (DME) electrolyte, with a current density of 80 A g−1 and capacity of 151 mA h g−1; it also exhibits stable, ultralong cycling performance. Synergism between the unique nanostructure of the composite and the low-viscosity DME electrolyte may be responsible for the extraordinary cycling and rate performance. A full cell with a Na3V2(PO4)3 (NVP) electrode delivers a capacity of 111 mA h g−1 at 100 A g−1; moreover, the Ni/Ni3S2–NVP full cell retains 55% of its capacity after 5000 cycles at 20 A g−1. The developed strategy, which uses a conductive metal-nanoparticle/metal-sulfide nanocomposite, is applicable to other systems and is scalable for practical applications.

The effect of a mixture of iron and nickel nanopowders of various concentrations on the growth and yield of corn

This paper shows the effect of various doses of a mixture of nanopowders of metals-microelements of iron and nickel (Fe + Ni) on the growth of corn, yield and its structure. Various doses of a mixture of Fe+Ni nanopowders were studied in the range of 0.5-2.0 g/t for corn ROSS 145 MB (grain hybrid). A mixture of iron and nickel nanopowders is effective in dressing corn before sowing. When using a dose of NP Fe + Ni 1.0 g/t, the height of plants in the phase of 5-6 leaves increased by 7.1%, in the flowering phase the leaf area increased by 18.4% higher than the control. It is shown that a mixture of Fe+Ni nanopowders 1.0 g/t increased the yield of green mass with cobs by 12.6%, cobs without a wrapper - by 14.3%, the weight of 10 cobs - by 185 g or 10.9% higher than the control. Under the influence of the optimal dose of nanopowders NP Fe + Ni 1.0 g/t in corn grain, the ash level increased by 0.18%, crude protein - by 1.4%, the amount of fat practically did not change. The content of vitamins has changed significantly, for example, vitamin C in the experiment is almost 2 times higher than the control, vitamin A - by 48%, vitamin E - lower than the control by 20%.

Effect of Nickel Nanopowder on the Thermal Degradation of Coal Tar Distillate

Regularities of influence of nickel nanopowder on the thermal degradation of coal tar distillate were deter-mined using model-free Kissinger, Flynn-Wall-Ozawa and model-fitting Coats-Redfern methods. Coal tar distillate with a boiling point of <350 °C was obtained by simple distillation of primary coal tar from the Shubarkol deposit. Nickel nanopowder was used as a catalyst and was added to coal tar distillate in a quantity of 1 % of the mass of the distillate and then the process of thermal degradation of coal tar distillate was con-ducted at heating rates 5, 10 and 20 °C/min in an inert gas medium. Nickel powder was obtained by high-voltage discharge impact on the dc electrolysis. X-ray diffraction (XRD) analysis showed that the obtained nickel powder has face-centered cubic structure and the average crystallite size calculated by the Scherrer equation was ~ 34 nm. Calculations of activation energy were performed via processing of thermogravimetric data. The Kissinger method showed that the activation energy value decreases from 145.19 kJ/mol to 43.65 kJ/mol, by the Flynn-Wall-Ozawa (FWO) method the value decreases from 152.82 kJ/mol to 51.65 kJ/mol, and by the Coats-Redfern method the value decreases from 143.38 kJ/mol to 52.64 kJ/mol. Ap-plicability of these methods is ensured by the high values of correlation coefficients.

Interaction dynamics between compacted pyrophoric nickel nanopowders and air

The dynamics of interaction with the air of non-passivated pyrophoric nickel nanopowders pressed into cylindrical compacts has been investigated in detail. A method for preventing self-ignition in the air of compacts made of nickel nanopowder has been experimentally established.

Hydrogen Desorption Properties of MgH2 + 10 wt% SiO2 + 5 wt% Ni Prepared by Planetary Ball Milling

MgH2 is a very hopeful material for application as hydrogen storage material in the solid form. This is due to its reversibility and its ability to store large amounts of hydrogen, which is 7.6 wt%. However, this material still has weaknesses, namely high operating temperature and slow kinetic reactions. Various attempts have been made to overcome this weakness, including downsizing and adding catalyst. In this study, double catalyst was used, namely natural silica extracted from rice husk ash and nickel nano powder, with a composition of MgH2 + 10 wt% SiO2 + 5 wt% Ni. The purpose of this research was to study the effect of downsizing and using these catalysts to the thermodynamic and kinetic properties of the hydrogen storage material MgH2. Samples were prepared by using High Energy Ball Milling (HEBM), with variations in milling time of 1, 5, 10, and 15 hours. The X-ray Diffraction (XRD) pattern showed the presence of an impurity phase in the samples milled for 10 and 15 hours. It also showed a reduction in grain size with increasing milling time. However, agglomeration has occurred in the samples milled for 15 hours. From the Scanning Electron Microscope (SEM) results can be seen that the sample with longer milling time, were homogeneously distribute. Thermal investigation showed that the lowest desorption temperature was achieved in samples with milling time of 5 and 10 hours, namely 287 °C and 288 °C. This study shows that natural silica catalyst plays a role in improving the thermodynamic characteristics of MgH2, while Ni plays a role in improving the kinetic characteristics of MgH2. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Highly porous, hierarchically structured nickel nanomaterials consolidated by powder metallurgy methods

Highly porous permeable nickel materials with a hierarchical structure were consolidated by powder metallurgy methods in sintering-dissolution and sintering-evaporation processes from nickel nanopowder and micropowders of two different types of space holders – water-soluble sodium chloride NaCl and thermally unstable ammonium bicarbonate NH4HCO3, respectively. Nanopowder nickel materials with three levels of hierarchical porosity were obtained using bidisperse micropowders of soluble NaCl space holder.

Thermal Stability of Compact Pyrophoric Nickel Nanopowder Samples after Passivation

The use of nanopowders implies the ability to safely store them without changes in their physicochemical parameters ensured by passivation. In this work, we have determined the thermal stability range in air for compact samples of different diameters prepared from pyrophoric nickel nanopowders and then passivated. The results demonstrate that compact samples prepared from nickel nanopowder can be safely stored in air at temperatures of up to about 200°C without additional oxidation, which points to their high thermal stability. The lack of a noticeable heat release during slow heating to 200°C and the presence of only Ni in both the passivated and heat-treated samples according to X-ray diffraction data suggest that the oxide layer is very thin or that there are noncrystalline oxide phases. The observed uniform oxygen and nickel distributions over fracture surfaces of samples after heating suggests that their interaction with air during both the passivation process and heating to temperatures on the order of 200°C is a bulk process.

Features of Nickel Nanoparticles Structure Synthesized by the Spark Discharge Method

Nickel nanopowders are obtained by the spark discharge method, which is based on the evaporation of the electrode surface under the action of the discharge current, followed by vapor condensation and the formation of nanoparticles. Nickel electrodes with a purity of 99.99% are used to synthesize the nickel nanoparticles in the setup. Nitrogen is used as the carrier gas with a purity of 99.998%. XRD, TEM, and EDX analyses of the nanopowders are performed. Moreover, HRTEM images with measured interplanar spacings are obtained. In the nickel nanopowder samples, a phase of approximately 90 wt% with an expanded crystal lattice of 6.5% on average is found. The results indicate an unusual process of nickel nanoparticle formation when the spark discharge method is employed.

The influence of heating conditions of the samples of nickel nanopowders on the modes of their interactions with the air

In the present work, compact samples of pyrophoric nickel nanopowders with an average particle size of 55 nm obtained by the method of chemical metallurgy were investigated. The possibility of passivation of compact samples 3 mm in diameter made of nickel pyrophoric nanopowders in the air is experimentally shown for the first time. The time of complete passivation is only 3–5 s for a relative sample density 0.4–0.5. According to X-ray phase analysis, only Ni phase was observed in passivated samples. It was found that passivated samples maintain thermal stability in the air at slow (< 10 °C/s) heating to ~ 200 °C; it is an important parameter for fire safety at handling of nanopowders. The analysis of passivated samples by the SEM method showed no traces of sintering of nickel nanoparticles, even after testing for thermal stability. The uniform distribution of oxygen within passivated samples according to energy dispersive X-ray analysis data indicates the volumic nature of the interaction of samples with the air during passivation. For the passivated samples, critical heating conditions were determined, under which self-ignition occurs.