Fabrication of SiO2 hollow fibers

In this paper, we have used cotton template for fabrication of SiO2 hollow fibers. At first a suspension of SiO2 powder with DI water is prepared and some pieces of cotton inserted to the suspension to get wet and then are dried. At final step, samples are calcinated in high temperatures to burn cotton. For morphology study of hollow fibers, four different experiments have been designed. In first experiment, three samples are dried at 40 0C for 1 h and finally calcinated at 500, 600 and 700 0C for 6 h. In second experiment, samples are dried at 40, 50 and 60 0C and finally calcinated at 600 0C. In third experiment, the SiO2 powder have grinded in two times, 1 h and 30 min and dried at 50 0C and calcinated at 600 0C. In forth experiment, the weight ratio of SiO2 powder and DI water is changed and dried at 50 0C and calcinated at 600 0C. Study of morphology of fabricated samples showed that a sample which is prepared with weight ratio of 1:100, dried at 50 0C, and calcinated at 600 0C is optimum sample.  Fibers which are prepared by this method keep the structure of cotton and have high porosity and surface area. At optimum conditions; hollow fibers with 30 μm length, 3 μm diameter, and 300 nm tube thickness is obtained. Finally, the suspension is made with alcohol instead of DI water. Our results showed that alcohol helps to separate the cotton fibers and fabricated hollow fibers is obtained even with several centimeters length, 3.5 μm diameter, and 200 nm tube thickness and some fibers are seen twist which exist naturally in the cotton fibers