Nickel Particle Size Research Articles

LDH@MgSiO3 multi-core@shell catalyst for dry reforming of methane

In this paper, LDH@SiO2 catalyst was prepared via coating a layer of silica over LDH (Layered Double Hydroxide) nanoplates. Then it was calcined and further treated by hydrothermal method with magnesium acetate to convert silica layer into MgSiO3. After H2- reduction, a layer of branch-like MgSiO3 was observed as the shell and nickel nanoparticles with average diameter around 10 nm were encapsulated within the shell, which was called as LDH@MgSiO3 multi-core@shell catalyst. This catalyst was then tested in dry reforming of methane (DRM) at 675 °C and the CH4 conversion was kept stable around 25% for 30 h time on stream at GHSV of 360 L/gcat/h. Besides, the H2/CO ratio in the product gas was 0.85, much higher than that of LDH@SiO2 catalyst, indicating its superb selectivity. Characterization revealed that the formation of MgSiO3 was beneficial to reduce the nickel particle size, modify the porosity and improve the surface alkalinity, which enhanced the DRM activity and selectivity. More importantly, it enhanced the hydrothermal stability, thus preventing the reconstruction of the shell.

Preparation of a finely dispersion nickel-based in-situ pyrolysis catalyst: Influence of lignocellulosic constituents

Metal/biochar catalysts could be synthesized via directly subjecting biomass impregnated with metal salts to pyrolysis. The properties of biochar are intricately linked to the inherent composition of the raw material, which in turn could influence the degree of metal dispersion and its catalytic impact. The poplar sawdust and its fractioned proportion was employed for the preparation of Ni-based biochar catalysts. The work mainly focuses on the impact of lignocellulosic material with diverse compositions on the dispersion of nickel particles during the calcination-pyrolysis co-process. Given that cellulose and holocellulose constituted the majority of the material, the matching catalyst support may encourage the migration of nickel species to produce substantial amounts of particles, perhaps as a result of several reactions such as dehydration and aromatization. In contrast, the utilization of sawdust as a support demonstrated a remarkable effect in dispersing nickel particles, nickel particle size and H2 uptake were 7.0nm and 19.8 μmol/g, respectively, while also displaying exceptional catalytic activity in the hydrogenation of vanillin, with the maximum conversion and 2-methoxy-4-methylphenol (MMP) yield of 99.7% and 69.0%. It has been determined that the presence of lignin in the system has a beneficial impact on the dispersion of nickel and its catalytic activity.

Research on high-entropy spinel microwave absorption materials: Exploration of machine learning and experimental integration

With the advancement of electronic communication technology, the intensity of electromagnetic radiation is increasing, and traditional wave-absorbing materials no longer meet the demands in various current environments. Spinel ferrite is one of the earliest materials used for absorbing electromagnetic waves, and the introduction of "high entropy" and controlling the degree of entropy disorder can achieve performance regulation. Nonetheless, the lengthy testing period and high costs associated with trial and error have posed challenges, limiting the development of high entropy microwave absorbing materials. This study utilized machine learning techniques to construct a high-entropy spinel microwave absorption property database. The design of CoxNi0.4-xCu0.2Zn0.2Mn0.2Fe2O4 (X = 0, 0.1, 0.2, 0.3, 0.4) was informed by the SHAP plots of the GBR model. Machine learning demonstrates that factors such as cobalt and nickel content, particle size, and others significantly influence microwave absorption performance. The experimental result manifests it and Co content regulate the microwave absorbing performance through adjusting the defect density and particle size. The CoxNi0.4-xCu0.2Zn0.2Mn0.2Fe2O4 with optimized Co content achieved a reflection loss (RL) of −45.32 dB, and an effective absorption bandwidth (EAB) of 6.48 GHz. This approach significantly reduced the research period, presented a novel research methodology for other scholars, and expedited the research progress in the field of microwave absorbing materials.

Modulating nickel precursors to construct highly active Ni/Y2O3 catalysts for CO2 methanation

Constructing the interface of Ni/Y2O3 heterogeneous catalyst is a feasible strategy for efficient catalyst design in CO2 methanation, which can create the active Y–O–Ni interfacial sites by utilizing the interaction between Ni and Y2O3. In this work, the strategy of using different nickel precursors (nickel nitrate, nickel acetate, basic nickel carbonate and nickel citrate) was used to prepare various Ni-based catalysts supported on Y2O3, which were estimated for their catalytic performance on CO2 methanation. The catalysts were characterized based on BET, XRD, TEM, H2-TPR, XPS and CO2-TPD, etc. The results indicated a close correlation between the metal dispersion and particle size of Ni/Y2O3 catalysts and the nickel precursor employed. The Y–O–Ni interface structure in Ni/Y2O3 catalysts, associated with basic sites, provides a richer source of basic sites, offering more active sites for CO2 adsorption and activation. Ni/Y2O3 catalyst prepared with nickel nitrate as the precursor exhibited characteristics such as a highly enhanced nickel dispersion, a smaller nickel particle size, and more abundant metallic Ni0 sites. Moreover, nickel nitrate-derived Ni/Y2O3 catalyst exhibited optimal catalytic activity, achieving a CO2 conversion rate of up to 92 % at 300 °C, with 100 % selectivity to CH4, and displaying good stability over 30 h. Therefore, the dispersion of Ni and the size of Ni particles could be controlled by adjusting the precursor, which is closely associated with the catalytic activity of Ni/Y2O3 catalyst. This work unveils the interface-property relationship of Ni/Y2O3 catalysts and provides a new insight into strategy of constructing more effective Ni-based catalyst for CO2 methanation through the controlled nickel precursor.

Combined steam and CO2 reforming of methane over Ni-based catalysts with spherical porous structure

Combined steam and dry reforming of methane (CSDRM) is expected to be promising when considered as a new alternative feedstock for F-T synthesis because it can produce high-quality syngas without carbon deposition. In this study, the support particle sizes were varied independently to assess their influence on the performance of the metallic Ni. The catalytic activity is most influenced by nickel particle size and distribution, and it has also been investigated for its significant role in the metal-support interaction. To perform CSDRM, the Ni-based catalyst was prepared by impregnation method on a spherical nano-silica support prepared by sol–gel method. The size of the spherical silica nanoparticles (40–300 nm) was controlled by varying the ethanol molar concentration; the spherical particles showed high performance on a uniform and evenly drawn support. In the 44 nm spherical silica catalyst, it was confirmed that the maximum dispersion increased to 21 % and the reducibility increased to 36 %. For stable synthesis gas production, various feed gas ratios (0.7:1.3:1.7) were established and the respective feed gas components (CH4, CO2 and steam) and reactions were investigated. Also, with the increase in the concentration of steam in the feed gas ratio, there was a significant increase in CO production. This trend was attributed to competing reactions occurring due to the side reactions (WGS↔RWGS; CO+H2O↔CO2 + H2) and was investigated with equilibrium constant values using thermodynamic equilibrium plot data. From the experimental results obtained, the catalyst showed high performance on a stable support and produced a stable H2/CO ratio of 2 for 100 h, without side reactions, at the feed gas ratio (CH4:CO2:H2O = 1:0.6:0.85).

Quantifying Microstructure Features for High-Performance Solid Oxide Cells.

The drive for sustainable energy solutions has spurred interest in solid oxide fuel cells (SOFCs). This study investigates the impact of sintering temperature on SOFC anode microstructures using advanced 3D focused ion beam-scanning electron microscopy (FIB-SEM). The anode's ceramic-metal composition significantly influences electrochemical performance, making optimization crucial. Comparing cells sintered at different temperatures reveals that a lower sintering temperature enhances yttria-stabilized zirconia (YSZ) and nickel distribution, volume, and particle size, along with the triple-phase boundary (TPB) interface. Three-dimensional reconstructions illustrate that the cell sintered at a lower temperature exhibits a well-defined pore network, leading to increased TPB density. Hydrogen flow simulations demonstrate comparable permeability for both cells. Electrochemical characterization confirms the superior performance of the cell sintered at the lower temperature, displaying higher power density and lower total cell resistance. This FIB-SEM methodology provides precise insights into the microstructure-performance relationship, eliminating the need for hypothetical structures and enhancing our understanding of SOFC behavior under different fabrication conditions.

Dry Reforming of Methane over Mn-modified Ni-based Catalysts

Ni-based bi- and trimetallic Mn, Mg and aluminum containing catalysts prepared by the solution combustion synthesis (SCS) method were tested in dry reforming of methane (DRM). As a comparison 12 wt.% Ni/α-Al2O3 catalyst prepared by wet impregnation was also investigated. The catalysts were characterized by means of XRD, N2 physisorption, H2-TPR, CO2-TPD, NH3-TPD, TPO, CHNS, TGA, SEM and TEM. Formation of crystalline MnAl2O4 was observed at high temperatures during SCS. The average nickel particle size varied in the range of 12–36 nm. Addition of Mn promoted reduction of Ni and elevated the amount and strength of the basic sites.Graphical

Highly dispersed nickel-tuned silica lanthana catalyst: Interplay of morphology and textural properties for hydrogen-rich syngas through the carbon dioxide reforming of methane

Methane (CH4) and carbon dioxide (CO2) are major contributors to the rise in greenhouse gas emissions, exacerbating global warming. Consequently, it is crucial to convert and utilize these gases effectively to mitigate their impact on the atmosphere. Carbon dioxide (dry) reforming of methane (DRM) offers an efficient solution for converting CH4 and CO2 into syngas (H2/CO). In this study, we compare the effectiveness of a robust catalytic system, including a fibrous silica lanthana-supported nickel (NSLF-10) catalyst, to a silica lanthana-supported nickel composite (NSL-C) developed using commercial lanthana and silica. Our investigation focuses on their respective performances in the production of hydrogen-rich syngas through DRM. The NSLF-10 catalyst exhibited improved physicochemical properties such as uniformly dispersed nickel, stronger metal-support interaction, small nickel particle size, and increased surface area, which significantly enhanced the catalytic performance of DRM. Notably, the NSLF-10 catalyst achieved a high conversion of CH4 and CO2 at 85 % and 83 %, respectively, with an elevated H2/CO ratio compared to the NSL-C catalyst, which has a conversion of CH4 and CO2 at 72 % and 64 %, respectively. The unique properties of the NSLF-10 catalyst provide a high synergistic effect between the nickel active sites and SLF support, leading to a high conversion of CH4 and CO2 with no signs of catalytic deactivation.

Densification Behaviours of TiC/Ni Metal Ceramic Alloys Produced by Powder Metallurgy

Ceramic Metallic Alloys of TiC/Ni, Comprising Titanium Carbide with Nickel Contents of 5%, 15%, 30%, and 50%, were Fabricated through Solid-Phase Sintering at 1400°C with a 2-hour Holding Time and a Pressure of 50MPa. This Study Explores the Impact of Nickel Content on the Mechanical and Structural Properties. The Solidification Mechanism between TiC and Ni is Governed by Carbon Diffusion through TiC Particles, Affecting the Morphology of TiC and Carbon Particles in Ni Samples. The Reaction Behavior within the TiC/Ni Alloys was Analyzed, and Microstructural and Mechanical Characteristics were Examined to Evaluate the Influence of Varying Nickel Contents. Results indicate that in all samples, the TiC matrix exhibited a solid solution of the FCC phase. The reaction mechanism of Ti-C-Ni reveals the evolution of solid phase formation with increasing nickel content. As nickel content increases, the mass and size of nickel particles grow, leading to a more uniform and homogeneous structure. At a nickel content of 15%, the samples displayed a bending strength of 1200 ± 50 N, a microhardness of 800 ± 20 (HV 0.1), and a density of 5.6 ± 0.2.

Plasma‐catalytic CO2 methanation over NiO/bentonite catalysts prepared by solution combustion synthesis

AbstractA solution combustion synthesis (SCS) process to prepare nickel catalyst over bentonite (NiO/Ben) is reported. Compared to the traditional impregnation method, NiO/ben produced by SCS has smaller nickel particle size and higher dispersion. With a metal loading of 20 wt%, the afforded NiO/Ben demonstrates excellent catalytic activity for CO2 methanation in a dielectric barrier discharge reactor. In certain discharge conditions (H2:CO2 ratio of 5 in feed gas, discharge input power of 45 W, and gas hourly space velocity of 11 320 h−1), CO2 conversion and CH4 selectivity are as high as 55.8% and 84.6%, respectively. Under the conditions of plasma configuration, the strong interaction between the nickel species and the support plays an important role in the CO2 methanation process.

Low-cost and highly stable Ni@NC materials synthesized from metal-organic framework precursors for selectively catalytic hydrogenation of p-nitrophenol under mild conditions

The catalytic hydrogenation of aromatic nitro compounds under mild conditions to generate amino compounds is a great challenge in terms of conversion, selectivity and stability. In this paper, two classes of nitrogen-doped carbon coated nickel nanoparticles, coined Ni@NC-P and displaced Ni@NC-T were prepared by high-temperature pyrolysis of MOFs using inexpensive terephthalic acid and high-priced trimesic acid as carbon source, respectively. One from the former class, namely the Ni@NC-P-500 catalyst, exhibits the best catalytic performance, which is superior to Ni@NC-T-500 Samples. For the selective hydrogenation of p-nitrophenol under mild conditions (60 °C, 2 h), the Ni@NC-P-500 catalyst shows >99.9 % conversion of p-nitrophenol and >99.9 % selectivity for p-aminophenol and can be recycled five times without obvious decrease of conversion and selectivity, thanks to its larger specific surface area (382.02 m2·g−1), smaller nickel particle size (8.2 nm), higher nitrogen content (especially pyridine nitrogen), higher electron-rich nickel content and less hydrophilic properties than that of the Ni@NC-T-500. The excellent stability and recyclability of the catalysts are mainly attributed to their core–shell structure, i.e., zero-valent nickel nanoparticles encapsulated within a nitrogen-doped carbon layer with an appropriate microporous structure, whereas zero-valent nickel nanoparticles have the ability to activate dihydrogen and block dioxygen.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in isopropanol over hydrotalcite-derived nickel-based catalyst

A series of hydrotalcite-derived nickel-based catalysts were synthesized by coprecipitation, drying, calcination and reduction, and used for the selective hydrogenation of furfural to tetrahydrofurfuryl alcohol. Ni1Zr1Al2-R, with specific surface area (SBET) of 145.6 m2, narrow pore size distribution of 7.1 nm, and small Ni0 particle size of 7.31 nm, showed 100 % furfural conversion and 94.5 % tetrahydrofurfuryl alcohol selectivity under mild conditions (140 °C, 2 h). It was found that furfural was first hydrogenated to furfuryl alcohol, which was further hydrogenated to tetrahydrofurfuryl alcohol. XRD and TEM showed that Ni0 (111) plane played an important role on the catalytic hydrogenation process. Al increased the specific surface area (SBET) and total acid sites of the catalyst, providing more possibilities for the catalyst to contact the substrate. The introduction of Zr improved the ratio of medium acid sites and decreased the size of metal nickel particles, improving the resistance to carbon deposition and allowing the structure and catalytic performance to remain stable after five recycles.

A-site defects boosted exsolution on (La0.5Ca0.5)(1-α)Ni0.06Ti0.94O3-δ for ethanol steam reforming

With global industrialization and population increase, the constraints of fossil fuels in terms of price and environmental protection necessitate the development of alternate energy sources. Ethanol reforming, as a non-fossil-originated hydrogen production process, has become an industrially promising reaction. In this work, perovskite titanate (La0.5Ca0.5)(1-α)Ni0.06Ti0.94O3-δ with different A-site deficiency was synthesized via a modified Pechini method. Orthorhombic titanates with grain size of 200 to 500 nm were obtained with nickel cooperated into the frameworks. The extent of A-site deficiency influences the size and population of exsolved nickel particles. Higher A-site defects would greatly induce the exsolution of nickel, thus promoting the catalytic activity in ethanol steam reforming reaction. La0.4Ca0.4Ni0.06Ti0.94O3-δ sample showed an outlet composition that was closed to thermodynamic equilibrium under S/C = 3 and WHSV = 8.8 gethanol/(gcat·h). The metal agglomeration was inhibited during 8-hour reforming at high temperatures, while the deactivation during the stability test was mainly due to the formation of graphite carbon.

Effect of Surface Activation on the Microstructure and Corrosion Resistance of MAO/Ni-P Composite Coating on AZ91D Magnesium Alloy.

The purpose of this study is to improve the number and distribution of active particles on the MAO layer by changing the activation method, thus improving the corrosion resistance of the coating. The structure of the coatings was characterized by SEM, XRD, XPS, and AFM, as well as the corrosion resistance of the coatings by polarization curves, EIS tests, immersion tests, and salt spray tests. The conductive resistance and adhesion of different composite coatings were compared. The results demonstrate that the properties of the composite coating are significantly affected by different activation methods, and the Ni-P coating prepared with more active particles offers superior corrosion protection to the inner layer. The quantity and distribution of active particles affect the compactness of the coating by influencing the initial deposition process. The size of nickel particles is larger and the inter-grain porosity increases in the case of fewer active sites, and as the number of active sites increases, the size of nickel particles decreases, and the coating compactness increases. The mechanism of the effect of the number of active particles on the deposition process of electroless Ni-P coating was proposed.

Magnetoelectric Composites: Engineering for Tunable Filters and Energy Harvesting Applications

Multiferroic ceramic composites have been engineered to incorporate multiple desired physical properties within a single ceramic component. The objective of this study was to create such composites through pressure less sintering ferroelectric-doped PZT and nickel–zinc ferrite at a temperature of 1250 °C. The growth of ferrite grains was found to be influenced by the concentration of the ferroelectric PZT phase. Consequently, an increase in the ferrite content decreased the average particle size of nickel–zinc ferrite by a factor of 1.8. After impedance spectroscopy, the multiferroic ceramic composites can be categorized into two groups: those with low ferrite content (<20%) and those with a high ferrite content (>20%). Composites with a high ferrite content are suitable for dual-band filters or shield applications. The impedance spectroscopy analysis revealed that the resonance frequency can be shifted to higher frequency ranges. Therefore, it was demonstrated that modifying the composition of the multiferroic composite allows for tailoring the impedance behavior to shield living and working spaces against such radiation to meet the demands of the 21st century.

Performance estimation by multiphase-field simulations and transmission-line modeling of nickel coarsening in FIB-SEM reconstructed Ni-YSZ SOFC anodes I: Influence of wetting angle

FIB-SEM measurements of as-processed Ni-YSZ solid oxide fuel cell (SOFC) anodes are conducted. Based on the reconstructed volume as initial condition, multiphase-field simulations of nickel coarsening are performed to investigate the microstructure under operating conditions. The effect of the wettability of nickel on YSZ is discussed to span a possible range of different operating conditions. Effective properties including nickel particle size distributions, mean particle diameters, tortuosities and triple-phase boundary lengths (TPBL) serve as quantitative indicators for possible degradation and failure. The resulting data is used in a transmission-line model (TLM) to estimate anode performance and long-term stability. Generally, the simulations show that Ni coarsening at 750°C takes place mainly in the first 100 hours. It is found that nickel coarsening is enhanced when nickel shows dewetting on YSZ. Among other findings, the TPBL decreases significantly during the simulations for all parameter sets and is insusceptible to variations in wetting angle. The TLM considers the reduction of TPBL as the main factor for degradation. Loss of nickel connectivity can lead to a further significant drop in anode performance occurring predominantly for low wettability of nickel on YSZ.

Effects of Metal-Support Interactions and Interfaces on Catalytic Performance over M2O3- ( M = La , Al-) Supported Ni Catalysts

The metal-support interactions and their interfaces have showed great influence on catalytic activity and stability. Herein, different support of M2O3- ( M = La , Al-) supported Ni catalysts was prepared by a citric acid-assisted sol-gel method. The physical structure and chemical properties of the As-prepared catalysts were systematically characterized by various technologies. The catalytic performance was evaluated for hydrogen or syngas production by ethanol steam reforming and methane dry (CO2) reforming, respectively. The results showed that compared with Al2O3 support, the nickel supported on La2O3 possessed a smaller particle size of nickel even after high-temperature reduction. In addition, the La2O3-supported nickel catalyst had stronger metal-support interaction and higher nickel electron density as a result of higher ethanol conversion activity and stability. The ethanol conversion was maintained at 87.8% after a 3000-minute test, and the hydrogen production was as high as 6500 μmol/min. Moreover, the Ni-La2O3 catalyst also showed good activity for methane dry reforming. The initial conversion of methane and carbon dioxide was close to 90%, and the ratio of H2/CO reached 0.94. The better catalytic performance of the Ni-La2O3 catalyst was ascribed to smaller particle size of Ni, rich metal-support interfaces, more nickel electron densities, abundant strong basic sites, and strong metal-support interactions.

UiO-66-derived Ce/Ni-ZrO2 nano-catalysts with a large nickel surface area for the highly efficient CO2 methanation under high GHSVs

In this work, a new preparation method is developed for the preparation of Ce/Ni-ZrO2 nano-catalyst (Ce/Ni-ZrO2-N). Although similar catalytic systems have been studied by many others, there is still a need for improvement in terms of nickel surface area, catalytic efficiency, and insights of the mechanism. The Ce/Ni-ZrO2-N developed in this study exhibits a large nickel surface area (50.6 m2∙g−1) and a small nickel particle size (∼5.1 nm). During the preparation of such a catalyst, UiO-66 is used not only as a precursor for the preparation of ZrO2 with a large surface area but also as a dispersant for confining nickel nanoparticles. The catalyst demonstrates an excellent catalytic performance at high GHSVs. With a 16-fold increase in GHSVs, the CO2 conversion of Ce/Ni-ZrO2-N only decreases by 32.1 %, whereas that of the control group drops by 50.3 %. This is attributed to the high nickel surface area and relatively low activation energy. Moreover, the characterization and Density Functional Theory (DFT) studies reveal that electron transfer from Ce to Ni enhances the activation of CO2 on the Ni sites, which subsequently contributes to a better catalytic performance. In addition, the catalyst shows excellent anti-coking ability during the 40 h's testing, which, according to DFT calculations, is attributed to the high energy barrier for coke formation on the active sites.

The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane‐Derived Silicon Oxycarbide

A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer‐derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero‐field‐cooled (ZFC) and field‐cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single‐domain NP for ceramic materials.

Sinter‐Resistant Nickel Catalyst for Lignin Hydrogenolysis Achieved by Liquid Phase Atomic Layer Deposition of Alumina

AbstractLignin hydrogenolysis is a key step in the sustainable production of renewable bio‐based chemicals and fuels. Heterogeneous metal catalysts have led to high yields but they rapidly deactivate, notably due to nanoparticle sintering and carbonaceous deposit formation. While these deposits can be removed by regeneration, sintering is irreversible and a significant barrier to commercialization. Here, simple liquid phase atomic layer deposition is used to deposit an alumina layer to protect nickel particles from sintering. In the gas phase, it is proved that alumina can prevent sintering during reduction up to 600 °C. This catalyst for hydrogenolysis of extracted lignin in batch and continuous operation is used. In batch, the overcoated catalyst maintains high monomer yields with little sintering over four cycles of reuse while the yield obtained with the catalyst without an overcoat reduces to half and severe sintering occurs. In a continuous flow reactor, deactivation rates are three times lower for the catalyst with the alumina overcoat. Microscopy images confirm that the alumina overcoat largely preserves nickel particle sizes after ten days of operation. The results demonstrate that catalyst overcoating with metal oxides substantially slows irreversible deactivation during lignin hydrogenolysis, which could facilitate the development of continuous lignin upgrading.