A typical preparation of MxOy/SiO2 oxide nanocomposites (where M is Cu, Mg, Mn, Ni and Zn) consists of three steps. In the first step, the homogeneous dispersion of silicon dioxide was prepared in the aqueous solution of the corresponding metal acetate, with an estimated ratio of the components under stirring at room temperature. The content of the metals was 3.0 mmol/g SiO2. In the second stage, the dispersions were dried at a layer thickness of 4–7 mm at 130 °C for 5 h, then ground in a mortar and sieved through a sieve with a mesh size of 0.5 mm. In the third and final stage, all the powders obtained were calcined in air at 600 °C for 2 h. The reference sample of fumed silica was treated in the same three steps: homogenization of the aqueous dispersion, drying, grinding, sieving and calcination at the same temperature.
The modification of resorcinol–formaldehyde (RF) polymers by oxide nanocomposites was carried out by an in situ method by mixing resorcinol, formaldehyde and MxOy/SiO2 nanocomposites or pristine SiO2 at a weight ratio of 1:2:1 with stirring at room temperature. The unfilled resorcinol–formaldehyde control sample (RFR) was prepared by stirring resorcinol with formaldehyde at the same 1:2 weight ratio. All mixtures were hermetically sealed, placed in a thermostatic oven and treated at 50 °C for 4 days for complete curing and maturation of the RF resin. After gelling, a brown, solid polymer composite was obtained, which was dried at the same temperature for 18 h. All polymer composites were crushed and sieved to obtain a fraction of 0.2 to 0.5 mm. The polymer composites were labeled as RF/SiO2, RF/Cu/SiO2, RF/Mg/SiO2, RF/Mn/SiO2, RF/Ni/SiO2, RF/Zn/SiO2 and RF/Zn/SiO2.
The carbonization of the samples was carried out in a tubular furnace under a nitrogen atmosphere (with a flow rate of 100 mL/min) by heating from room temperature to 800 °C at a heating rate of 5 °C/min and holding at the maximum temperature for 2 h. As-synthesized composites were designated as C/SiO2, C/Cu/SiO2, C/Mg/SiO2, C/Mn/SiO2, C/Ni/SiO2 and C/Zn/SiO2.
The modification of resorcinol–formaldehyde (RF) polymers by oxide nanocomposites was carried out by an in situ method by mixing resorcinol, formaldehyde and MxOy/SiO2 nanocomposites or pristine SiO2 at a weight ratio of 1:2:1 with stirring at room temperature. The unfilled resorcinol–formaldehyde control sample (RFR) was prepared by stirring resorcinol with formaldehyde at the same 1:2 weight ratio. All mixtures were hermetically sealed, placed in a thermostatic oven and treated at 50 °C for 4 days for complete curing and maturation of the RF resin. After gelling, a brown, solid polymer composite was obtained, which was dried at the same temperature for 18 h. All polymer composites were crushed and sieved to obtain a fraction of 0.2 to 0.5 mm. The polymer composites were labeled as RF/SiO2, RF/Cu/SiO2, RF/Mg/SiO2, RF/Mn/SiO2, RF/Ni/SiO2, RF/Zn/SiO2 and RF/Zn/SiO2.
The carbonization of the samples was carried out in a tubular furnace under a nitrogen atmosphere (with a flow rate of 100 mL/min) by heating from room temperature to 800 °C at a heating rate of 5 °C/min and holding at the maximum temperature for 2 h. As-synthesized composites were designated as C/SiO2, C/Cu/SiO2, C/Mg/SiO2, C/Mn/SiO2, C/Ni/SiO2 and C/Zn/SiO2.
Free full text: Click here
