Preparation And Characterization Of Bulk Porous Nanosolids

Using TiO₂ nanoparticles as the starting material, PMMA/TiO₂ composite porous nanosolids have been prepared by a novel solvothermal hot-press (STHP) method for the first time. TiO₂ bulk porous nanosolids were prepared from the above composite materials, from which PMMA is removed by calcination. In addition, polymer gel was introduced template as to improve the pore diameter uniformity of the TiO₂ bulk porous nanosolid. TiO₂ and ZnO bulk porous nanosolids were prepared by STHP method using TiO₂ or ZnO nanoparticles with polyvinyl pyrrolidone (PVP-K30) water solution as pore-forming agents. Besides, the properties of these composite materials have been characterized.Firstly, PMMA/TiO₂ composite porous nanosolids have been prepared by polymerization of methyl methacrylate with deionized water as pore-forming agents, and the properties of these composite materials are investigated. The results indicate that, with the increasing amount of MMA, the main pore diameter of the composite materials distributes in the reigon of 5-25 nm, but their pore uniformity, specific surface area and pore volume changed obviously. While the weight ratio of MMA to TiO₂ nanoparticles is 1:19, the specific surface area and pore volume of the PMMA/TiO₂ composite materials are 127.20 m²/g and 0.27 cm³/g, respectively.PMMA/TiO₂ composite porous nanosolids have also been prepared using polymethyl methacrylate as raw material, and the properties of these composite materials are characterized. The results indicate that, the average pore diameter, specific surface area and pore volume of these composite materials can be adjusted by changing the amount of PMMA. The average pore diameter of PMMA/TiO₂ composite porous nanosolids is 8.77 nm and obviously decreases when the weight ratio of PMMA to TiO₂ nanoparticles is 1:9. The average pore diameter, specific surface area and pore volume of PMMA/TiO₂ composite are all zero when the weight ratio of PMMA to TiO₂ nanoparticles is 2:3. The specific surface area and pore volume of these composite materials decrease gradually with the increasing weight ratio of PMMA to TiO₂ nanoparticles. All these PMMA/TiO₂ composite porous nanosolids have high compressive strength, and the dielectric constant of PMMA/TiO₂ composite porous nanosolids also changes obviously with different weight ratio of PMMA to TiO₂ nanoparticles. When the weight ratio of PMMA to TiO₂ nanoparticles is 1:19, the dielectric constant of PMMA/TiO₂ composite porous nanosolids reaches the maximum value, i.e. 11.44 and then decreases gradually with the increasing weight ratio of PMMA to TiO₂ nanoparticles.In order to improve the uniforminty of pore diameter, TiO₂ bulk porous nanosolids were prepared from the above composite materials by removing PMMA through a calcination process. The results indicate that, TiO₂ nanoparticles have not undergone any phase transformation or changing in particle size during the process of calcinations and PMMA has been removed completely from the pore or channels. At the same time, TiO₂ bulk porous nanosolids have high thermal stability both in N₂ and air. The average pore diameter, specific surface area and pore volume of TiO₂ bulk porous nanosolids varies slightly with the increasing weight ratio of PMMA to TiO₂ nanoparticles. When the weight ratio of PMMA to TiO₂ nanoparticles is 1:9, TiO₂ bulk porous nanosolids have the widest pore diameter and the lowest specific surface area, namely, 10.44 nm and 51.1720 m²/g, respectively. Compared with TiO₂ bulk porous nanosolids prepared without PMMA, the pore volume of TiO₂ bulky porous nanosolids decreases in various grades. With the increasing weight ratio of PMMA to TiO₂ nanoparticles, the compressive strength of TiO₂ porous nanosolids increases at the beginning and reaches the maximum value, 242.8 MPa, which is much higher than that of TiO₂/PMMA composite porous nanosolids while the weight ratio of PMMA to TiO₂ nanoparticles is 1:9, then decreases gradually. With the increasing weight ratio of PMMA to TiO₂ nanoparticles, dielectric constant of TiO₂ porous nanosolids increases at the beginning and reaches the maximum value, 14.08 when the weight ratio of PMMA to TiO₂ nanoparticles is 1:4, then decreases gradually. Therefore, the average pore diameter, specific surface area, pore volume, compressive strength and dielectric constant of TiO₂ porous nanosolids could be adjusted by changing the weight ratio of PMMA to TiO₂ nanoparticles.In order to further improve the uniformity of the pores, polymer is used as the template to prepare TiO₂ bulk porous nanosolid. Butyl acrylate (BA) and styrene reacts to form polymer using ammonium persulfate as initiator. TiO₂ bulk porous nanosolid has been prepared using the polymer as template by the STHP method. The main pore size of these nanosolids is 5-35 nm although the weight ratio of monomer to TiO₂ nanoparticles is different, but their pore uniformity, surface area and pore volume changes in various grades. The results indicate that when the weight ratio of BA monomer to TiO₂ nanoparticles is 1:9, the TiO₂ porous nanosolid is obtained with good pore diameter uniformity, its pore volume is 0.32 cm³/g, and surface area reaches the maximum value, 87.94 m²/g. When the weight ratio of styrene monomer to TiO₂ nanoparticles is 1:9, the TiO₂ porous nanosolid is prepared with the highest surface area, namely, 174.17 m²/g, and its pore volume is 0.34 cm³/g.Non-ionic surfactant PVP-K30 solution was used as pore-forming agent to prepare TiO₂ and ZnO bulky porous nanosolids. The pore structure of the TiO₂ and ZnO bulk porous nanosolid is different while the PVP-K30 solution concentration varies. The results indicate that, compared with deionized water, the average pore diameter is obviously enlarged when PVP-K30 solution is used as pore-forming agent. TiO₂ and ZnO bulk porous nanosolids with good pore diameter uniformity, high surface area and pore volume have been successfully prepared by controlling the PVP-K30 solution concentration. With the increase of the amount of PVP-K30, the average pore diameter and pore volume decrease correspondingly. Part of PVP-K30 residue in the channels of TiO₂ porous nanosolids, and they can be removed by heat-treatment. The average pore diameter and pore volume increase obviously and the specific surface area changes very little when the materials have been treated at high temperature. When the weight ratio of PVP-K30 to TiO₂ nanoparticles is 1:9, the average pore diameter and pore volume of TiO₂ porous nanosolids is 14.20 nm, 0.23 cm³/g, respectively.