NiO Particles Research Articles

Combustion of nickel hyperaccumulator plants investigated by experimental and thermodynamic approaches

This work was undertaken to determine whether thermodynamic calculations can predict the amount and composition of ash produced by combustion of nickel hyperaccumulator (HA) plants in the context of agromining. To this end, three HA plants containing about 1wt% of nickel were submitted to isothermal combustion at 550, 815, 900°C and the solid residues were characterized by complementary techniques (TGA, XRD, ICP-OES, ion chromatography, SEM-EDX), while thermodynamic calculations were performed with the FactSage software using the dry biomass composition as input. We present an in-depth evaluation of inorganics behavior based on the combination and comparison of experimental data and calculations: effect of temperature on ash yield, nature of crystallized phases, ash elemental composition and inorganics volatilization. Our work confirms that equilibrium calculation is a powerful method to evaluate the behavior of inorganic elements during thermal treatment of biomass, despite some lacks in the databases. For the nickel HA plants, an innovative result is that, after combustion, nickel is always in the form of NiO particles, that can mix with MgO to form (Ni,Mg)O solid solutions. These results have direct implications for understanding the combustion process and for better design of the following leaching step aiming at Ni recovery.

Multi‐wall carbon nanotubes by catalytic decomposition of carbon monoxide on Ni/MgO

AbstractThe redox behavior of the catalyst and the catalytic decomposition of carbon monoxide (CO) were investigated in the synthesis process of multi‐wall carbon nanotubes (MWCNT) using Ni/MgO catalyst. The surface morphology of the heated Ni layer was observed by TEM to confirm the formation of NiO particles (50 nm or less) and NiO (222). The chemical reaction behavior of the catalyst in CO the atmosphere was displayed via TG‐DSC analysis, and the reduction of NiO was revealed due to the mass decrease of 2.71 wt% and the exothermic peak at around 400°C. The deposition of carbon was identified with an increase in mass and the exothermic peak near 600°C. Ni (111) and carbon (002) facets was taken place in a diffraction pattern of carbon deposited catalyst, indicating the reduction in NiO and the graphitic carbon deposition. The crystallinity of the graphitic carbon was analyzed as the ratios of 0.998 for ID/IG and 0.26 for sp3/sp2 in Raman and photoelectron spectra. The encapsulated Ni in MWCNT was observed through TEM‐EDS, verifying the activation of the catalyst by CO.

Rapid laser fabrication of Nickel oxide nanoparticles for UV detector

In the present work, silicon-based Nickel oxide heterojunction photodetectors was manufactured via two-step. First, the NiO was directly synthesised by laser ablation (Model Nd:YAG with a wavelength of 1064 nm) in the liquid approach of a pure Ni target: typically with various number of pulses at constant laser energy. Second, the prepared NiO colloidal was then deposited on a silicon wafer surface by a dip-coating method. The impacts of laser pulses on the NiO particles properties were in briefly presented. The synthesis of NiO NPs with a good-nanocrystalline structure in deionized water was proved. The dominated shape of the NiO NPs was quasi-spherical and their concentration was observed to be affected by the laser conditions. FTIR spectral results proved the formation of NiO bonds at 526 cm−1and 507 cm−1. The optical energy bandwidth decreases from 3.75 to 3.6 eV as the laser pulses increase. The introduction of the prepared NiO nanoparticles into silicon showed a well-performance for UV detection. The nanostructured NiO/Si heterojunction photodetector exhibited clear rectifying I-V behaviour in the dark condition and showed prominent photovoltaic properties under illumination. The contrast ratio of the fabricated detector increases with an increasing number of laser pulses. It demonstrated a maximum value of the responsivity and detectivity 0.7 A/W, 63 × 1012 cm. Hz1/2. W−1, respectively under 330 nm UV light illumination.

Oxide properties of deformed Alloy 690TT in caustic solution at high temperature

Oxide properties and growth mechanism of deformed Alloy 690 T T SG tube in caustic solution at high temperature were investigated. The results indicated that the oxide film was comprised of the surface oxide layer and the inner oxide layer. The surface oxide layer exhibited a double layer structure with semi-coherent surface Ni-rich phases and subsurface Fe-rich phase. The inner oxide layer exhibited a multilayered structure: outermost large-sized NiO particle layer, transitional mixed Cr-rich spinel, NiO and Ni layer and inner Cr2O3 layer. Furthermore, some preferential oxidation channels extended along the grain boundaries and deformation bands inward respectively.

In Situ Formation of Nickel Nanoparticles from Nickel Formate for Preparation of Straight Silicon Nanowires by Molten Salt Electrolysis

AbstractWater‐soluble nickel formate (Ni(HCOO)2), which can be dispersed uniformly in silica (SiO2), was used as the catalyst precursor for producing silicon nanowires (SiNWs) by molten salt electrolysis in this work. Ni(HCOO)2/SiO2 pellets were decomposed into Ni/SiO2 and NiO/SiO2 pellets in N2 and air atmosphere, respectively. The NiO particles could retain the initial size in molten salt due to their high melting point, while the Ni particles were always aggregated. Thus the NiO particles possessed a larger catalytic surface area than the Ni particles. After long time electrolysis of NiO/SiO2 pellets in a pilot‐plant, the obtained silicon presented a smooth and straight nanowire morphology and offered a delithiation capacity of 1995.5 mAh/g after 100 cycles when used as negative electrode material. These findings may have an important significance in mass production of straight SiNWs for lithium ion batteries.

NiO/Carbon Aerogel Microspheres with Plum-Pudding Structure as Anode Materials for Lithium Ion Batteries.

To enhance the electrochemical performance of nickel oxide as anode materials for lithium ion batteries, NiO/carbon aerogel microspheres with a plum-pudding structure were designed and prepared by a sol-gel technique followed by two calcination processes under different atmospheres. Carbon aerogel microspheres (pudding) can act as a buffering and conductive matrix to enhance the structural stability and conductivity of the embedded NiO particles (plums), which are quite advantageous to the cycling performance and rate capability. Consequently, NiO/carbon aerogel microspheres with a plum-pudding structure deliver an initial charge capacity of 808 mAh g−1 and a reversible capacity retention of 85% after 100 cycles. The enhancement in electrochemical performance relative to pure NiO microspheres suggests that the design of a plum-pudding structure is quite effective.

Synthesis of NiO Crystals Exposing Stable High‐Index Facets

AbstractMetal oxides exposing high‐index facets are potentially impactful in catalysis and adsorption processes owing to under‐coordinated ions and polarities that alter their interfacial properties compared to low‐index facets. Here, we report molten‐salt syntheses of NiO particles exposing a variety of crystal facets. We show that for a given anion (nitrate or chloride), the alkali cation has a notable impact on the formation of crystals exposing {311}, {611}, {100}, and {111} faces. Based on a parametric analysis of synthesis conditions, we postulate that the crystallization mechanism is governed by the formation of growth units consisting of NiII complexes whose coordination numbers are determined by temperature and the selection of anion (associated to the coordination sphere) and alkali cation (associated with the outer coordination sphere). Notably, our findings reveal that high‐index facets are particularly favored in chloride media and are stable under prolonged periods of catalysis and steaming.

Synthesis of NiO Crystals Exposing Stable High-Index Facets.

Metal oxides exposing high-index facets are potentially impactful in catalysis and adsorption processes owing to under-coordinated ions and polarities that alter their interfacial properties compared to low-index facets. Here, we report molten-salt syntheses of NiO particles exposing a variety of crystal facets. We show that for a given anion (nitrate or chloride), the alkali cation has a notable impact on the formation of crystals exposing {311}, {611}, {100}, and {111} faces. Based on a parametric analysis of synthesis conditions, we postulate that the crystallization mechanism is governed by the formation of growth units consisting of NiII complexes whose coordination numbers are determined by temperature and the selection of anion (associated to the coordination sphere) and alkali cation (associated with the outer coordination sphere). Notably, our findings reveal that high-index facets are particularly favored in chloride media and are stable under prolonged periods of catalysis and steaming.

Effects of CaO addition on Ni/CeO2–ZrO2–Al2O3 coated monolith catalysts for steam reforming of N-decane

A series of 10 wt%Ni/CeO2–ZrO2–Al2O3 (10%Ni/CZA) coated monolith catalysts modified by CaO with the addition amount of 1 wt%~7 wt% are prepared by incipient-wetness co-impregnation method. Effects of CaO promoter on the catalytic activity and anti-coking ability of 10%Ni/CZA for steam reforming of n-decane are investigated. The catalysts are characterized by N2 adsorption-desorption, XRD, SEM-EDS, TEM, NH3-TPD, XPS, H2-TPR and Raman. The results show that specific surface area and pore volume of as-prepared catalysts decrease to some extent with the increasing addition of CaO. However, the proper amounts of CaO (≤3 wt%) significantly enhance the catalytic activity in terms of n-decane conversion and H2 selectivity mainly due to the improved dispersion of NiO particles (precursor of Ni particles). As for anti-coking performance, reducibility of CeO2 in composite oxide support CZA is promoted by CaO resulting in providing more lattice oxygen, which favors suppressing coke formation. Moreover, the addition of CaO reduces the acidity of 10%Ni/CZA, especially the medium and strong acidity. But far more importantly, a better dispersion of NiO particles obtained by proper amounts of CaO addition is dominant for the lower carbon formation, as well as the higher catalytic activity. For the spent catalysts, amorphous carbon is the main type of coke over 10%Ni–3%CaO/CZA, while abundant filamentous carbon is found over the others.

Transition Metals Modified Ni−M (M=Fe, Co, Cr and Mn) Catalysts Supported on Al2O3−ZrO2 for Low‐Temperature CO2 Methanation

AbstractAlthough considerable efforts have been made in transforming carbon dioxide into high value‐added products, it still remains a big challenge to convert CO2 to CH4 directly at low temperature. Here, we report transition metals (including Fe, Co, Cr and Mn) modified Ni catalysts supported on Al2O3−ZrO2 via a single‐step sol‐gel method for low temperature CO2 methanation. Specially, incorporation of Mn metal into the Ni/Al2O3−ZrO2 catalyst was the most beneficial to the reduction and dispersion of NiO particles on the surface of Al2O3−ZrO2 composite support in comparison to other transition metals such as Fe, Co and Cr, which promoted the formation of active metallic Ni sites. Furthermore, the addition of Mn promoter facilitated the formation of surface oxygen vacancies, which combined with more metallic Ni active sites, thus improving the low‐temperature CO2 methanation performance significantly. An optimized Ni−Mn/Al2O3−ZrO2‐1 catalyst exhibited a superior CO2 conversion of 78 % with CH4 selectivity almost 100 % at a lower temperature of 300 °C without any deactivation in the long term 100 h reaction, which presented a potential industrial application for CO2 methanation.

Influence of nickel precursors on the properties and performance of Ni impregnated zeolite 5A and 13X catalysts in CO2 methanation

Zeolite 13X and 5A supported Ni catalysts were synthesized for CO2 methanation using the evaporation impregnation method. The influence of using different Ni precursors (nitrate, citrate, and acetate) as well as calcination temperatures on the catalyst properties and performance were investigated. XRD, SEM-EDX, TEM, STEM-EDX, N2 physisorption, H2-TPR, TPD-NH3 and TG/DTA were used for detailed characterization of the catalysts. The parent structure of the zeolites did not change during catalyst synthesis. Using nickel citrate and acetate resulted in smaller NiO particle size compared to nitrate. STEM-EDX results showed that all the Ni-precursor complexes entered more efficiently the 13X zeolite structure, which is mainly due to steric hindrance resulting from the smaller pore size of 5A. Methanation experiments revealed that the 13X catalysts synthesized using nickel citrate (5% Ni) displayed clearly higher activity, compared to the catalysts synthesized using nickel nitrate or nickel acetate. A 79% conversion at 320 °C was obtained with 100% selectivity towards CH4 and the catalyst showed excellent stability during 200 h testing. Overall, it can be concluded that the Ni precursor significantly influences the physico-chemical characteristics and catalytic properties of Ni 13X and Ni 5A zeolite catalysts in CO2 methanation: complex size and pore size matter.

Microstructure control of NiO-based ion storage layer with various sized NiO particles to evaluate the electrochromic performance

We have investigated the relationship between the crystalline size of the ion storage layer and the electrochromic performance. The electrochromic device was fabricated with a WO3 thin film and NiO-based ion storage layer. The electrochromic performance of the device was evaluated for various morphologies of the ion storage layer, with varying size of NiO powders using a kinetically sprayed process. The ion storage layer having the smallest crystalline size using micron-sized NiO powder, had improved initial transmittance and electrochemical reaction of electrochromic performance; this was attributed to its low charge transfer resistance and high diffusion rate of Li+ ion in the electrolyte. In particular, the electrochromic device using micron-sized NiO film exhibited an improvement of up to 65% in optical transmittance, with minimum haze. Therefore, we have proven that the electrochromic performance using the optimized microstructure of NiO ion storage layer can be improved by controlling the crystalline size of thin films deposited by the kinetically sprayed process.

Investigation of structural and optical properties of NiO nanoparticles mediated by Plectranthus amboinicus leaf extract

Nickel oxide nanoparticles were successfully synthesized by biogenic synthesis method using nickel nitrate as the precursor, mediated by Plectranthus amboinicus leaf extract. The structure of the sample was identified using XRD and confirmed that the particles are with good crystalline nature with an average size is around 100 nm. The morphological and Elemental composition was analysed with SEM and EDAX analysis. There are some agglomerates because of bio molecules present in the leaf extract. The functional groups were identified using FTIR spectroscopy and the strong absorption peak at 452 cm−1 confirms the presence of Ni-O vibration. The bandgap of the synthesized NiO particles was calculated from the Tauc plot based on UV–Vis spectroscopy and found that the value of the energy gap is 3.6 eV. The dielectric constant and dielectric loss concerning various temperatures was calculated and the sample was tested for its antibacterial and antifungal activities. It showed a moderate positive effect in antibacterial test and a positive reaction in the antifungal activity against the fungal strain Candida.

Role of wide particle size distribution on magnetization

Role of particle size distribution on magnetization of two polydispersed samples of antiferromagnetic NiO particles is investigated. Zero field-cooled and field-cooled susceptibility as a function of temperature (10–350 K) data indicate that samples are superparamagnetic. This behavior is again confirmed from M–H loops (up to $${\pm }\,70$$ kG) at 10 and 350 K. The magnetization as a function of applied magnetic field data at 350 K is analyzed considering a lognormal distribution in particle size. The estimated particle size distributions are compared with those determined from transmission electron micrographs. We find that the particle size distribution is overestimated if magnetic anisotropy is ignored while analyzing the magnetization data.

Synthesis and electrochemical performance of NiO/Fe3O4/rGO as anode material for lithium ion battery

NiO/Fe3O4/rGO composite materials were successfully obtained via a solvothermal route and characterized by charge/discharge test, TEM, XRD, SEM, EIS, HRTEM, XPS, CV, etc. The results showed that the Fe3O4 nanospheres have an average size around 150 nm, NiO is relatively larger (about 300 nm) and agglomerated by rod-shaped particles. The nanospheres of Fe3O4 and rod-shaped NiO particles were distributed on the surface of reduced grapheme oxide. The BET specific surface and BJH desorption average pore diameter of NiO/Fe3O4/rGO are 497.26 m2 g−1 and 1.23 nm, respectively, so it improves the contact area between electrode materials and electrolyte, make ion diffusion path shorter and facilitates ion insertion/desertion. Discharge capacity was 841 mAh g−1 at the first cycle and maintain 647 mAh g−1 after 200 cycles at the current density of 500 mA g−1, and even at the current density of 1000 mA g−1, the discharge capacity can keep 582 mAh g−1 after 200 cycles with a well Coulombic efficiency and retention. And electrochemical impedance of NiO/Fe3O4 and NiO/Fe3O4/rGO is 110 Ω and 75 Ω, respectively, indicating that the material has a good ionic conductivity.

Synergy between oxides of Ni and Ca for selective catalytic lactic acid synthesis from glycerol in a single step process

Single-step selective catalytic dehydrogenation of glycerol to lactic acid requires a catalyst with strong dehydrogenation and hydration capabilities. A multi-component catalyst consisting of an alkaline earth metal and assisted by a transition metal is deemed essential to achieve yield lactic acid in this multi-step reaction. A series of NiO/CaO catalysts with different Ni/Ca ratios were synthesized via a co-precipitation method and tested for their catalytic activity. The physicochemical properties of the catalysts were studied through TGA, SEM, N2-adsorption, CO2-TPD and XRD analyses. The NiO particles were relatively smaller than those of CaO to enable their deposition on the surface of the latter. High amounts of basic sites of more than 4.84mmol/gcat were detected on the NiO/CaO catalysts. The lactic acid yield was strongly influenced by the molar ratio of the NiO/CaO catalysts due to their improved dehydrogenation and hydration capabilities. The synergy between NiO with CaO in the catalyst was also elucidated. The 0.43NiO/CaO catalyst exhibited desirable activity with 41.4% lactic acid yield at 89.3% glycerol conversion. A catalyst loading of 15wt. %, a reaction temperature of 290°C and 1.5h of reaction time were needed to achieve this conversion. Thus, the combination of NiO/CaO resulted in the synergy towards achieving better lactic acid yield in this selective conversion to lactic acid. However, accurate control of the reaction was critical as the intermediates and lactic acid were highly reactive to participate in other side-reactions.

Modification of Ni/Al2O3 catalyst with Pd nanoparticles for selective phenylacetylene semihydrodenation

NiPd/Al2O3 (4.9 wt% of Ni–0.1 wt% of Pd), Ni/Al2O3 (5 wt% of Ni) and Pd/Al2O3 (0.1 wt% of Pd) catalysts were tested in the liquid-phase semihydrogenation of phenylacetylene in batch- and flow-type reactors. Catalysts were characterized by temperature-programmed reduction, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Differences in the formation of palladium particles during deposition of metals on the surface of the alumina were revealed. Relatively large Pd particles observed in Pd/Al2O3 transformed to β-PdHx phase in a hydrogen atmosphere. When Pd and Ni are co-supported, no monometallic palladium particles were detected. Pd was apparently atomically distributed in the close vicinity of some NiO particles. As a result, there were two types of NiO particles in NiPd/Al2O3: NiO particles isolated from Pd species and those in close contact with atomically dispersed palladium. This distribution of metals provided the formation of activated hydrogen, which, in turn, led to an increase in the phenylacetylene conversion compared to monometallic Ni/Al2O3, while maintaining high selectivity of styrene formation. The close interaction of metals and their co-action in the hydrogenation of phenylacetylene was confirmed by the kinetic data obtained in a batch-type reactor. These data showed the difference in the reaction mechanisms on Ni/Al2O3 and NiPd/Al2O3.

Oxidation behavior of a novel nickel-based single crystal superalloy at elevated temperature

The oxidation behavior of a novel low-cost single crystal superalloy was thoroughly studied at high temperature. Three distinctive stages were observed in the oxidation kinetics curve, which corresponded to the different oxide film structures and oxidation mechanisms. The outer NiO grains, several spinels as well as inner Al2O3 layer took shape at first stage while the oxidation dynamics obeyed cubic law. However, the NiO particles began to spall off the specimen surface and the continuity of Al2O3 layer was partly destroyed in the next several hours. The alloy went through severe oxidation weight gaining at second stage which could be rationalized by the severe oxidation of W and Mo. The non-protective NiWO4 and NiMoO4 spinels were surprisingly found and the Al2O3 particles demonstrated the rod-like morphology during this period. The re-formation of dense Al2O3 layer and the volatilization of MoO3 gave rise to the reduction of mass gaining rate in the final stage, additionally, the oxidation kinetics transformed to subparabolic characteristic. Moreover, the experimental alloy exhibited good microstructural stability at elevated temperature, however, the microstructure degradation was considerably serious. The entire thickness of γ′-free layers had exceeded 0.1 mm on the alloy surface after 200 h oxidation at 1120 °C.

Study on the Mechanical and Tribological Properties and the Mechanisms of Cr-Free Ni-Based Self-Lubricating Composites at a Wide Temperature Range

A Cr-free Ni-based self-lubricating composites with MoS2 and Ag as lubricants were fabricated by the powder metallurgy method. The microstructures were examined. The mechanical properties and tribological behaviors of the composites were evaluated from room temperature to 800 °C. The fractography was observed and the fracture mechanisms were analyzed. The morphologies and the phase compositions of worn surfaces were determined and the wear mechanisms were elaborated. The results indicate that MoS2 did not completely decompose after sintering, and the NiMoAl-MoS2-Ag composite has the best tribological properties (0.22, 1.68 × 10−5) at 800 °C. The main wear mechanisms are micro-ploughing and plastic deformation. The improvement of tribological properties was attributed to the formation of the lubricating film consisting of NiO, Mo oxides, various molybdates, and Ag particles. The reactions resulting in these compositions are proposed. The mechanical properties degrade with the rise of temperature and the addition of lubricants. Both NiMoAl and NiMoAlAg alloys exhibit micro-void accumulation fracture while the composites with MoS2 reveal intergranular fracture.

Development of Cu-doped NiO nanoscale material as efficient photocatalyst for visible light dye degradation

We report herein the synthesis and characterization of Cu-doped NiO nanoparticles having new morphology with tuned band gap as an efficient photocatalyst using visible light for the removal of alizarin red dye from aqueous solutions. Composites were prepared using different Cu doping ratios via co-precipitation method followed by calcination at two different temperatures. SEM image of Cu-doped NiO (20% Cu doping) is interestingly different from the NiO particles, and different calcination temperatures (400 and 600 °C) greatly affected the morphology of NPs. Lower calcination temperature yielded nanocapsules, whereas the higher calcination produced hexagonal shaped slightly bigger NPs.