High-Temperature Stability and Saturation Magnetization of Superparamagnetic Nickel Nanoparticles in Microporous Polysilazane-Derived Ceramics and their Gas Permeation Properties

Abstract

Superparamagnetic Ni nanoparticles with diameters of about 3 nm are formed in situ at room temperature in a polysilazane matrix, forming Ni/polysilazane nanocomposite, in the reaction between a polysilazane and trans-bis(aceto-kO)bis(2-aminoethanol-k(2)N,O)nickel(II). The thermolysis of the Ni/polysilazane nanocomposite at 700 °C in an argon atmosphere results in a microporous superparamagnetic Ni/silicon oxycarbonitride (Ni/SiCNO) ceramic nanocomposite. The growth of Ni nanoparticles in Ni/SiCNO ceramic nanocomposite is totally suppressed even after thermolysis at 700 °C, as confirmed by HRTEM and SQUID characterizations. The analysis of saturation magnetization of Ni nanoparticles in Ni/polysilazane and Ni/SiCNO nanocomposites indicates that the saturation magnetization of Ni nanoparticles is higher than expected values and infers that the surfaces of Ni nanoparticles are not oxidized. The microporous superparamagnetic Ni/SiCNO nanocomposite is shaped as a free-standing monolith and foam. In addition, Ni/SiCNO membranes are fabricated by the dip-coating of a tubular alumina substrate in a dispersion of Ni/polysilazane in THF followed by a thermolysis at 700 °C under an argon atmosphere. The gas separation performance of Ni/SiCNO membranes at 25 and 300 °C is assessed by the single gas permeance (pressure rise technique) using He, H2, CO2, N2, CH4, n-propene, n-propane, n-butene, n-butane, and SF6 as probe molecules. After hydrothermal treatment, the higher increase in the hydrogen permeance compared to the permeance of other gases as a function of temperature indicates that the hydrogen affinity of Ni nanoparticles influences the transport of hydrogen in the Ni/SiCNO membrane and Ni nanoparticles stabilize the structure against hydrothermal corrosion.

Synthesis of Novel Cobalt-Containing Polysilazane Nanofibers with Fluorescence by Electrospinning

“…Novel cobalt-containing polymeric precursors for the polymer fibers were successfully prepared from a polysilazane (PSN) containing Si–H bonds and vinyl groups [34,35]. Spectroscopy was used to characterize the polymer, which has verified the structure and chemical connectivities as schematically shown in Scheme 1.…”

“…The synthesis of the polymer was carried out using the standard Schlenk technique under Ar. The reaction between the Co(II) complex and PSN causes the release of some polysilazane fragments in the form of ammonia (see Figure 1) [34]. The polycobaltsilazane used here is the result of the reaction between 15 wt % Co(II) complex and the polysilazane in DMF.…”

Ceramic Nanocomposites from Tailor-Made Preceramic Polymers

“…In order to enhance the hydrothermal stability of the PDC-NCs gas separation membranes, single-source precursors based on metal-modified preceramic polymers were used, as for the case of Ni/SiCNO, WC(O)/SiOC or WN/SiOCN nanocomposites. The in situ precipitation of the metallic or ceramic nano-particles within the SiOC/SiOCN matrix was found to be responsible for the improved stability of the ceramic membranes in aggressive environments [ 395 , 396 ].…”

Porous Silicon Oxycarbonitride Ceramics with Palladium and Pd2Si Nanoparticles for Dry Reforming of Methane

“…Moreover, the well-controlled pyrolysis of preceramic precursors at intermediate temperatures under inert atmospheres is decisive in developing micro-and mesoporous components with high surface area [4][5][6][7][8]. Owing to these unique properties, PDCs have been extensively studied for various engineering applications, such as coatings [9], sensors [10], battery anodes [11][12][13], and membranes [14]. In addition, micro-mesoporous PDCs with high surface areas have been reported as promising catalytic supports for several metal catalysts [15][16][17][18].…”