Nanocrystalline Processing and Interface Engineering of Si3N4-Based Ceramics

摘要

Construction and modification of the novel tubular flow reactor for the synthesisof nanocrystalline materials by thermal evaporation in a forced flux of gas has been an ongoing process over the past year. The first version of the reactor was used to synthesize nanocrystalline silicon (Si). The incoming gas flow rate is set with a mass flow controller. Helium (He) enters at one end of the reactor and flows over the resistively heated crucible where Si is evaporating. The silicon supply is continually replenished with a magnetically coupled loader. An IR pyrometer is used for temperature monitoring and control of the evaporation crucible. A pumping system consisting of a roots blower (booster pump) backed by a single-stage mechanical pump continuously removes the Si particles in the He gas stream from the growth zone over the evaporation source. The pressure in the reactor is controlled by a throttle valve with a capacitance manometer input. The particles entrained in the gas stream flow down the glass tube and are deposited on a liquid nitrogen cooled disc mounted parallel to the gas flow in the center of the collection chamber. jg p.1.