Transmission electron microscopy (TEM) of a perovskite Ba0.5Sr0.5TiO3 thin film, grown on a (001) LaAlO3 substrate by pulsed-laser ablation, reveals that the film of single-crystal quality has an unusually distorted lattice with lattice parameters a and b (parallel to the interface) larger than c (perpendicular to the interface) by 1.4%. There is evidence that the as-examined Ba0.5Sr0.5TiO3 film is a variant of its high-temperature cubic phase due to its anisotropic thermal contraction during cooling. A large lattice mismatch value of 5.7% (to be compared to the normal value of 4.13%) is observed from selected area electron diffraction patterns and high-resolution TEM images of cross-sectional specimens, which suggests that the growing high-temperature film under the film growth condition may have a larger lattice constant and a different thermal expansion behavior with respect to the bulk material.
The effects of some of the factors which influence fatigue strength of molybdenum disulphide (MoS2) filled cast nylon (type 6) gears such as diametral pitch, pressure angle, pitch line velocity, stress level, and lubrication were investigated. It was found that nylon gears, when properly designed and installed, are subject to minimal wear. Premature failures do occur through tooth interference caused by thermal expansion, tooth deflection and creep of the material. The importance of a proper backlash is discussed. Design capacities of nylon gears using formula and tables are presented.
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