Competition and Cooperation between Fluorine and Oxygen in SnO2:F Films

The interaction of oxygen and fluorine (F&O) in an F-doped SnO2 film, prepared by regulating oxygen partial pressure and the content of doped fluorine from 2.5 at% to 10 at%, was investigated in the large perspective through characterization methods including XRD, Raman spectroscopy, photoluminescence spectroscopy, wettability measurement and a Hall effect test system. The results show that F&O’s competitive and cooperative relationship would be reflected in the structure and electrical characteristics of SnO2 films. The oxygen action is overwhelming and restricts fluorine, so a growing number of F atoms occupy the position by the order of co-edge oxygen of tin–oxygen octahedron chains > oxygen vacancies > segregation, which leads to that carrier concentration modestly increasing from ~1015 to ~1017/cm−3. As oxygen action is inadequate to restrain fluorine, more F atoms are likely to enter the SnO2 lattice in a solid-solution way to replace the O atoms at the co-edge position of the octahedron chains, causing a dramatic increase in carrier concentration from ~1016 to ~1019/cm−3. Furthermore, by continuing to weaken oxygen action, only 2.5 at% of fluorine content could bring about a carrier concentration augment from ~1016/cm−3 to ~1018/cm−3, then going up to ~1021/cm−3 by post-annealing. However, the impairment of oxygen action contributes to a more effective doping of fluorine on SnO2 film. Such mutual action between fluorine and oxygen provides a direction for highly efficient production and tunable regulation of SnO2 film on demand.

Microfluidic Devices: Applications and Role of Surface Wettability in Its Fabrication

Microfluidic devices are based upon the behavior of fluids at the microenvironment level. They offer innumerable applications in the field of science and technology. Their scope is not limited to single field and now have applications in various fields such as biomedical, energy, chemicals and environment as well. Their major advantages are low experiment to cost ratio, and fast response time. Surface wettability is one of the factors contributing to the working of microfluidic devices. Surface wettability measurement is a very critical technique to measure the flow of micro fluids in microfluidic applications. In microfluidic devices the detection of small volume change with change in fluid properties is very minor because of the micrometer range. In order to detect this small change in micrometer range, an in situ wetting measurement is required. In this chapter, we have discussed about types of taxis, microfluidic devices: an application of taxis, microfluidic applications and role of surface wettability in microfluidic devices.

PLASMA MODIFICATION OF POLYVINYL ALCOHOL MICROFIBERS TO IMPROVE COHESION WITH CEMENT MATRIX

The article describes plasma modifications of the surface of polyvinyl alcohol (PVA) microfibers using oxygen and hydrogen plasma in order to improve the properties of the composite material containing modified microfibers, cement and recyclate. Five different modification times 30, 60, 120, 240 and 480 seconds were applied. Changes on fiber surface were detected by SEM analysis, packed cell wettability measurement, and weight loss during modification. The selected durations of plasma treatment were chosen to produce test samples on which the modulus of elasticity was continuously measured and then bending and compression tests were performed. The measured values were compared with the reference samples. Oxygen modified fibers behavior is more hydrophilic compare with reference fibers, but hydrogen modified fibres behave more hydrophobic than reference fibers.