Combustion Synthesis of Large Bulk Nanostructured Ni 65

A large bulk nanostructured Ni65Al21Cr14 alloy with dimensions of Φ 100 mm × 6 mm was produced by combustion synthesis technique followed with rapid solidification. The Ni65Al21Cr14 alloy was composed of γ′-Ni3Al/γ-Ni(Al, Cr) eutectic matrix and γ-Ni(Al, Cr) dendrite. The eutectic matrix consisted of 80–150 nm cuboidal γ′-Ni3Al and 2–5 nm γ-Ni(Al, Cr) boundary. The dentrite was comprised of high-density growth twins with about 3–20 nm in width. The nanostructured Ni65Al21Cr14 alloy exhibited simultaneously high fracture strength of 2200 MPa and good ductility of 26% in compression test

Facile synthesis of iron-based oxide from natural ilmenite with morphology controlled adsorption performance for Congo red

Three different morphologies of FeTiOx materials (microcubes, etched-microcubes and microspheres) were prepared by a facile method using acid leachate of ilmenite as the precursor. The three FeTiOx materials exhibited different adsorption performance for Congo red (CR). Among them, the FeTiOx microspheres showed the highest adsorption capacity (723.8 mg/g) for CR, followed by the FeTiOx etched-microcubes (617.8 mg/g) and the FeTiOx microcubes (296.5 mg/g). Characterization results showed that the three FeTiOx materials had distinctive phase composition, pore structure and surface functional group, which ultimately lead to their difference in adsorption performance. The adsorption mechanism of the three FeTiOx materials mainly includes ion exchange, electrostatic adsorption and mesopore filling, but the contribution of each type is different

Calcined ZnNiAl hydrotalcite-like compounds as bifunctional catalysts for carbonyl sulfide removal

The demand for a healthy environment and clean energy has been triggering the study on the preparation of excellent catalysts for the removal of sulfur-containing compounds. In this work, the removal of carbonyl sulfide (COS) from gas streams using Zn/Ni/Al hydrotalcite-derived oxide (HTO) was investigated. In particular, the structure, acid-base properties, and catalytic activity of catalysts prepared under different conditions were measured. A combination of experimental and theoretical methods, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), CO2 temperature programmed desorption (TPD), N-2 adsorption-desorption techniques, and density functional theory calculations, were used to elucidate the removal of COS use Zn/Ni/Al HTO. Experimental results indicated that Zn/Ni/Al HTO had relatively high activity for the removal of COS. The density functional theory calculations revealed that "many defects" existed on the Ni3AlO4 (001) plane of crystal, which brought more active centers for the chemical adsorption and hydrolysis of COS. Elemental sulfur, metal sulfide, and sulfate were the final product of COS removal. The consumption of basic sites, as well as the blocking of pores, was considered as the main reason for catalyst deactivation

Removal of volatile odorous organic compounds over NiAl mixed oxides at low temperature

In this paper, a series of NiAl hydrotalcite-like compounds (HTLCs) were prepared by the urea-decomposition method. Removal of carbonyl sulfide (COS) and methyl mercaptan (CH4S) over the hydrotalcite-derived oxides (HTO) at low temperature was studied. The Ni3Al-HTO exhibited higher catalytic activities than Ni3Al mixed oxides prepared by physical mixing method (Ni3Al-PM) or impregnation/calcination method (Ni3Al-IC). Based on the characterization, it was found that desulfurization activities are closely tied to the surface acid-base properties of catalysts. CO2-TPD indicates that the basic characteristic of the Ni3Al-HTO is prominent. XPS results showed that there was a strong interaction between Ni and Al element on Ni3Al-HTO. The first principle calculation based on density function theory was applied with the aim to study the change of basic sites. The results showed that Ni3Al-HTO presents a half-metallic characteristic. Electron transfer from the Al and O atom to the Ni atom was observed, which is helpful for the transfer of electrons from the surface and improves the catalytic activity. Analysis of the DRIFT spectra suggests that sulfate species was formed by the action of surface basic sites, resulting in the formation of H2O on the surface. (C) 2017 Elsevier B.V. All rights reserved.</p

Mechanism of activity enhancement of the Ni based hydrotalcite-derived materials in carbonyl sulfide removal

In this paper, a series of Ni based hydrotalcite-like compounds (HTLCs) were prepared by co-precipitation method. Carbonyl sulfide (COS) removal was investigated over the hydrotalcite-derived oxides (HTO). The properties of desulfurizer and its changes in the desulfurization process were systematically characterized by XRD, SEM, FTIR, CO2-TPD, XPS, XAFS and In-situ DRIFTS. The results showed that the activity series for removal of COS decrease in the following sequence: Ni3A1-HTO &gt; Ni3Fe-HTO &gt; Ni3Cr-HTO. In situ DRIFTS and quantum chemistry study implied that carbonate and sulfate was formed on the desulfurizer surface. Lewis basic sites and hydroxyl was determined to play a pivotal role for the COS removal. The enhanced activity after trivalent cations substitution is attributed to their high ability to provide electrons as evidenced by results of CO2-TPD, XPS and XAFS. This work is useful to explore feasible routes to improve the performance of desulfurization material for the feed gas purification. (C) 2017 Elsevier B.V. All rights reserved

Calcined ZnNiAl hydrotalcite-like compounds as bifunctional catalysts for carbonyl sulfide removal

The demand for a healthy environment and clean energy has been triggering the study on the preparation of excellent catalysts for the removal of sulfur-containing compounds. In this work, the removal of carbonyl sulfide (COS) from gas streams using Zn/Ni/Al hydrotalcite-derived oxide (HTO) was investigated. In particular, the structure, acid-base properties, and catalytic activity of catalysts prepared under different conditions were measured. A combination of experimental and theoretical methods, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), CO2 temperature programmed desorption (TPD), N-2 adsorption-desorption techniques, and density functional theory calculations, were used to elucidate the removal of COS use Zn/Ni/Al HTO. Experimental results indicated that Zn/Ni/Al HTO had relatively high activity for the removal of COS. The density functional theory calculations revealed that "many defects" existed on the Ni3AlO4 (001) plane of crystal, which brought more active centers for the chemical adsorption and hydrolysis of COS. Elemental sulfur, metal sulfide, and sulfate were the final product of COS removal. The consumption of basic sites, as well as the blocking of pores, was considered as the main reason for catalyst deactivation

Hierarchical Nanoassembly of MoS2/Co9S8/Ni3S2/Ni as a Highly Efficient Electrocatalyst for Overall Water Splitting in a Wide pH Range

The design of low-cost yet high-efficiency electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) over a wide pH range is highly challenging. We now report a hierarchical co-assembly of interacting MoS2 and Co9S8 nanosheets attached on Ni3S2 nanorod arrays which are supported on nickel foam (NF). This tiered structure endows high performance toward HER and OER over a very broad pH range. By adjusting the molar ratio of the Co:Mo precursors, we have created CoMoNiS-NF-xy composites (x:y means Co:Mo molar ratios ranging from 5:1 to 1:3) with controllable morphology and composition. The three-dimensional composites have an abundance of active sites capable of universal pH catalytic HER and OER activity. The CoMoNiS-NF-31 demonstrates the best electrocatalytic activity, giving ultralow overpotentials (113, 103, and 117 mV for HER and 166, 228, and 405 mV for OER) to achieve a current density of 10 mA cm–2 in alkaline, acidic, and neutral electrolytes, respectively. It also shows a remarkable balance between electrocatalytic activity and stability. Based on the distinguished catalytic performance of CoMoNiS-NF-31 toward HER and OER, we demonstrate a two-electrode electrolyzer performing water electrolysis over a wide pH range, with low cell voltages of 1.54, 1.45, and 1.80 V at 10 mA cm–2 in alkaline, acidic, and neutral media, respectively. First-principles calculations suggest that the high OER activity arises from electron transfer from Co9S8 to MoS2 at the interface, which alters the binding energies of adsorbed species and decreases overpotentials. Our results demonstrate that hierarchical metal sulfides can serve as highly efficient all-pH (pH = 0–14) electrocatalysts for overall water splitting