Abstract: This disclosure relates to fabrication of quartz hollow cylinder with reduced bubbles using atmospheric control. An example horizontal rotating arc furnace includes a housing, supports, and a rotary union. The housing defines an interior configured to receive silica particles and electrodes that generate a plasma arc and includes a plurality of first ports on an exterior of the housing fluidly connected to the interior and supply pipes fluidly coupled to the first ports. The supports mechanically couple the housing to a drive system to provide rotational motion to the housing. The rotary union is coupled to the housing includes second ports to fluidly connect to a vacuum supply. The second ports are fluidly connected to the first ports via the supply pipes. The horizontal rotating arc furnace is configured to apply a vacuum to the interior of the housing via the first ports when the housing is spinning.

Abstract: Novel boron nitride agglomerated powders are provided having controlled density and fracture strength features. In addition methods for producing same are provided. One method calls for providing a feedstock powder including boron nitride agglomerates, and heat treating the feedstock powder to form a heat treated boron nitride agglomerated powder. In one embodiment the feedstock powder has a controlled crystal size. In another, the feedstock powder is derived from a bulk source.