Effects of substrate temperature on the growth rate and morphology of diamond films synthesized by the flame CVD has been investigated. Experiments have been conducted with the flat premixed acetylene/hydrogen/oxygen flames of the velocity gradient of 3500 s^-1 and the equivalence ratio of 2.35, 2.40 and 2.45. The nucleus growth rate of diamond at high substrate temperature is higher than that at low substrate temperature. The growth rate of diamond films is found to be sensitive to the substrate temperature when the equivalence ratio is 2.45 and found to become higher with the substrate temperature. On the other hand, crystallites come to contain many “reentry grooves” that can be the sites of secondary nucleation, yielding deterioration of the film quality, at substrate temperatures higher than about 1200 K. When the equivalence ratio is 2.40 or lower, the growth rate is found to decrease in the temperature range 1100-1200 K of the substrate. In addition, it is further observed that crystallites with {111} facets are dominant at temperatures lower than 1200 K, while some crystallites with {100} facets are observed at temperatures higher than 1200 K. These experimental observations strongly suggest that the growth mechanism of the diamond film changes at the substrate temperature around 1200 K according to the change of precursors and the enhancement of etching of sp³ diamond.

Fire extinguishment by water mist has been researched because it doesn't damage electronic equipments like sprinkler and water doesn't harm the environment like Halons. First, we researched the flow field and motion of water mist without pool fire. From the results, we found that water mist spread horizontally by vortex induced by drag force between water mist and ambient gas. Next, we researched motion of single droplet and motion of water mist and a contribution to fire extinguishment in the flow field with pool fire. Water mist must reach a base of flame before evaporating in order to extinguish fire so that single water droplet and water mist were set away from a flame axis in order to avoid the effect of updraft induced by pool fire. The results revealed that motion of single water droplet differs from that of water mist and the effect of fire extinguishment depends on the initial location of water mist. The farther from a flame axis the initial location is, the weaker the effect of fire extinguishment is.