Titanium dioxide has attracted worldwide attention due to its prominent photocatalytic activity. It is generally accepted that nanoparticulate titanium dioxide with pure anatase structure exhibits high reactivity. Sol-gel is a simple and cost-effective technique capable of synthesizing anatase-phase titanium dioxide with particle sizes in nanometer range. This research aimed at examining effects of ageing periods on compositions and sizes of titanium dioxide synthesized by sol-gel technique. Experimental results revealed that prolonged ageing period demoted formation of anatase phase. Pure anatase phase was observed at ageing period of 1 day, while both anatase and rutile phases were observed at ageing periods of 4 and 7 days. The results also indicated that particle sizes decreased as the ageing periods increased. Nanoparticulate titanium dioxides with average sizes of 71.5, 50.4, and 29.7 nanometer were observed at ageing periods of 1, 4, and 7 days, respectively.
High photocatalytic activity of nanoparticulate titanium dioxide has attracted worldwide attention. Synthesis techniques of the nanoparticles, however, often require high energy supply or costly initial reagents. Solution combustion technique is an energy-effective technique capable of synthesizing nanosized titanium powders. This research aimed at utilizing a less expensive initial reagent in synthesis of nanoparticulate titanium dioxide by the solution combustion technique. The research also examined effects of dissolving agents on chemical composition and particle sizes of the synthesized powders. A low-cost initial reagent, titanium dioxide with average particle size of 154 nanometers, was dissolved in sulfuric acid or dispersed in nitric acid prior to the combustion. Experimental results revealed that the pure anatase phase titanium dioxide was successfully obtained in powders prepared from both sulfuric acid and nitric acid. The average particle size of the powder prepared from sulfuric acid was 77 nanometers, while that of the powder prepared from nitric acid was 117 nanometers. The difference in particle sizes was attributed to solubility of the initial reagent in the acid. Complete solution of initial reagent in sulfuric acid was the main factor attributed to finer particle size.
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