No abstract

We report on the synthesis and characterization of CsSnI3 perovskite semiconductor thin films deposited on inexpensive substrates such as glass and ceramics. These films contained polycrystalline domains with typical size of 300 nm. It is confirmed experimentally that CsSnI3 compound in its black phase is a direct band-gap semiconductor, consistent with the calculated band structure from the first principles. The band gap is determined to be ∼1.3 eV at Γ point at room temperature.

No abstract

A study has been made of the wear of various hard steels sliding unlubricated in dry air and in dry carbon dioxide at temperatures up to 500°C. Over the range of loads and speeds employed the wear is of a mild character and the wear debris is of oxide particles, no metallic debris being formed. The characteristics of the wear process depend on the type of oxide formed under the particular conditions of specimen temperature and surrounding atmosphere. In dry air, the wear rate increases with temperature to a maximum which depends on the type of steel, and then decreases at higher temperatures. Below the maximum, α-Fe2O3 is formed and is swept clean of the surface by the sliding process. The oxidation rate determines the wear rate which is independent of the load at constant specimen temperature. Above the maximum the spinel (Fe3O4) type oxide is formed which is adherent and wear protective. In dry carbon dioxide, spinel oxide is formed at all temperatures in the range 20–500°C and the wear rate is low, except at high temperatures when the steel becomes too soft to support the protective layer.

No abstract