An optimized process for in situ formation of multi-walled carbon nanotubes in templated pores of polymer-derived silicon oxycarbide

Abstract

A reliable and optimized process to grow carbon nanotubes (CNTs) in templated pores of polymer derived ceramic (PDC) matrixwas developed. It is realized through the pyrolysis of a preceramic polymer,i.e., poly (methyl-phenyl-silsesquioxane) (denoted as PMPS), in argon atmosphere at 1000°Ctogether with nickel-catalyst-coatedpoly-methyl-methacrylate (PMMA) microbeads (denoted as PMMA-Ni). PMPS served as both a precursor for the ceramic matrix and a carbon source for the CNT growth. PMMA microbeads were used as sacrificial pore formers and coated with nickel via an electroless plating method, which provides much betteran improved control of particle size of the catalyst and its distribution in the material. The influence of PMMA-Ni loading on the in situ growth of CNTs and the properties of CNTs/SiOCnanocomposites were studied through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and density/porosity measurements. Under optimized conditions, uniform distribution of in situ grown CNTs was observed within the templated pores of the SiOC matrix.The optimized process leads to reproducible high yield of CNTs in the pores.The development of such novelCNT/cellular ceramicnanocomposite materials is of significant interest for a variety of sensor applications.

Metal-Containing Ceramic Composite with in Situ Grown Carbon Nanotube as a Cathode Catalyst for Anion Exchange Membrane Fuel Cell and Rechargeable Zinc–Air Battery

“…The formation of CNTs in Ni/Co containing PDC is facilitated by various factors: , (i) the metal-containing ceramics show a decrease in activation energy for soot oxidation as a result of metal (intermediate oxide) transferring oxygen to soot particles; (ii) the electronic interaction between π state of carbon atoms (sp 2 ) with the metal or metal oxide leads to a less delocalized electronic state of carbon atoms due to higher electronegativity of carbon (2.55) compared with transition metal (Ni (1.91), Co (1.88)); (iii) the addition of Ni/Co based catalyst facilitates the dehydrogenation reaction that involves the removal of hydrogen from a PDC. These possible mechanisms for the formation of CNTs in metal-containing PDC have been presumed from similar material described in various literature. ,,, Moreover, the reaction starting at gas phase promotes the in situ growth of CNTs, whereas that in the solid matrix results in turbostratic carbon . The grown CNTs show at least 13–15 layers (MWCNTs) with inner and outer diameters of 10–15 and 30–60 nm, respectively, with a length of a few micrometers (Figures –).…”

“…These tentative hypotheses have been deduced from previous studies of Ni/Co-containing PDC materials. 15,16,50,51 It is believed that further studies are necessary to explain the role of Overall, the surface morphology analysis confirms that with the existence of pores in PDC the addition of Ni and Co was beneficial for an in situ growth of CNTs. Moreover, the thermal stability of the metal-containing ceramics is slightly better than that of bare H.A as a result of in situ grown CNT, which improves the overall thermal stability of the ceramic composite (Figure S4).…”

“…The possible reasons for hampering CNT formation in Pt-based precursors at 1000 °C are (i) the higher activation energy for soot oxidation is a result of limited interaction of Pt with subsurface “oxide” formation at this temperature and there is no oxygen transfers to soot particles and (ii) the electronegativity of Pt (2.28) is very similar to carbon atoms (2.55), which affects the delocalized electronic state of carbon atoms. These tentative hypotheses have been deduced from previous studies of Ni/Co-containing PDC materials. ,,, It is believed that further studies are necessary to explain the role of Pt catalyst in the oxidation process. Interestingly, the Ni–Pt (H.A.Ni.Pt) and Co–Pt (H.A.Co.Pt) containing ceramics possess a jellyfish-like morphology (Figure c–f).…”

“…These possible mechanisms for the formation of CNTs in metal-containing PDC have been presumed from similar material described in various literature. 15,16,50,51 Moreover, the reaction starting at gas phase promotes the in situ growth of CNTs, whereas that in the solid matrix results in turbostratic carbon. 43 The grown CNTs show at least 13−15 layers (MWCNTs) with inner and outer diameters of 10−15 and 30−60 nm, respectively, with a length of a few micrometers (Figures 2−4).…”

Ceramic Foams with Controlled Geometries Through 3D‐Printed Sacrificial Templates

“…[48,49] In addition, microscale pores have been successfully fabricated using packed PMMA beads (5-800 μm) as pore-forming agents, resulting in porosities ranging from 7% to 80%. [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] Porous SiOC-bonded SiC ceramics with apparent porosity between 17% and 58% were produced using silicon resin and PMMA microbeads (40-60 μm) as porogens for high-temperature gas filtration. [66] Furthermore, porous yttria-stabilized zirconia (YSZ) ceramics (%45%-72% porosity) were produced using monodispersed PMMA microbeads (%18 μm) as sacrificial pore-forming agent.…”