Synthesis of compositionally graded nanocast NiO/NiCo2O4/Co3O4 mesoporous composites with tunable magnetic properties

Abstract

Graphical contents entryMesoporous NiO/NiCo2O4/Co3O4 composites showing variable degrees of order and tunable magnetic properties are achievable by nanocasting using SBA-15 silica as hard templates. The -2 -NiCo2O4-rich powders are magnetic at room temperature and can be easily remotely manipulated using small fields (see Fig.).-3 -A series of mesoporous NiO/NiCo2O4/Co3O4 composites has been synthesized by nanocasting using SBA-15 silica as a hard template. The evaporation method was used as the impregnation step. Nickel and cobalt nitrates in different Ni(II):Co(II) molar ratios were dissolved in ethanol and used as precursors. The composites show variable degrees of order, from randomly organized nanorods to highly ordered hexagonally-packed nanowires as the Ni(II):Co(II) molar ratio decreases. The materials exhibit moderately large surface areas, in the 60-80 m 2 /g range. Their magnetic properties, saturation magnetization (MS) and coercivity (HC), can be easily tuned given the ferrimagnetic (NiCo2O4) and antiferromagnetic (NiO and Co3O4) character of the constituents. Moreover, the NiCo2O4 rich materials are magnetic at room temperature and can consequently be easily manipulated by small magnets. Owing to their appealing combination of properties, the nanocomposites are expected to be attractive for myriad applications.

Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

“…The lattice parameter, phase wt% and crystalline size are obtained from the Rietveld refinement of the XRD patterns, as listed in Table 2. Note that the value of phase wt% is quantitatively estimated using relative peak intensity ratio [36,37]. All the catalysts are classified into three different types of crystal structure according to the major phase in the sample: NiO based type (Nickel oxide and 33:67), NiCo2O4 based type (50:50, 67:33 and 75: 25) and Co3O4 based type (Cobalt oxide).…”

Graphene-nickel cobaltite nanocomposite asymmetrical supercapacitor with commercial level mass loading

“…For the case of GNCC-250, some NiO is also present, which would necessitate the formation of Co 3 O 4 . NiCo 2 O 4 and Co 3 O 4 are isostructural, so it is difficult to distinguish between the two phases based on XRD analysis [47]. Therefore, all three phases may coexist in the GNCC-250 specimen.…”

Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications

“…[ 5 ] The bulk NiCo 2 O 4 , nanorod NiCo 2 O 4 , and 3 wt% NiO/97 wt% NiCo 2 O 4 nanocomposite have been found to exhibit strong magnetization with a high saturation magnetization (M s ) of 29, ≈26, and 24 emu g −1 , respectively. [25][26][27] On account of these intrinsic properties and other advantages such as their low cost, rich abundance, and environmental friendliness, NiCo 2 O 4 materials have been extensively used in the fi elds of photodetection, [ 28 ] photocatalysis, [ 18 ] supercapacitors, [ 29 ] Li-ion batteries [ 30 ] and metal-air batteries, [ 31 ] fuel cells, [ 32 ] magnetic devices, [ 33 ] fl at-panel displays, [ 12 ] ferrofl uid technologies, [ 34 ] drug delivery, [ 35 ] optical limiters and switches, [ 36 ] infrared transparent conducting materials, [ 24 ] heterogeneous catalysis, [ 16 ] and various electrochemical reactions, for example: Cl 2 evolution, [ 37 ] O 2 evolution (OER), [ 38 ] O 2 reduction reaction (ORR), [ 39 ] H 2 O 2 reduction, [ 40 ] methanol oxidation, [ 41 ] and electrochemical sensors. [ 42 ] The extensive applications of NiCo 2 O 4 has encouraged the exploration of precise syntheses of particular NiCo 2 O 4 nanostructures.…”

“…[ 23 ] The magnetic properties and saturation magnetization of NiCo 2 O 4 can also be tuned by annealing, [ 24 ] morphology, [ 25 ] and components. [ 26 ] Iliev and co-workers have reported that epitaxial NiCo 2 O 4 fi lms deposited at temperatures lower than 450 °C are ferrimagnetic, and those grown at elevated temperatures are nonmagnetic. [ 5 ] The bulk NiCo 2 O 4 , nanorod NiCo 2 O 4 , and 3 wt% NiO/97 wt% NiCo 2 O 4 nanocomposite have been found to exhibit strong magnetization with a high saturation magnetization (M s ) of 29, ≈26, and 24 emu g −1 , respectively.…”