A vertical apparatus for hot-filament-assisted CVD deposition was used. Multiple small molybdenum rods of 1.0 mm diameter in vertical position were used as substrates. The top flat surfaces of the rods were polished, forming a right-angle relative to the rod longitudinal axis. Scratching with alumina powder of 9 micro meter particle size was used to enhance the nucleation. Tungsten wire of 0.2 mm diameter with several turns was used as the hot filament. The temperature of the hot filament and the temperature of the substrate holder were maintained at about 2500 K and 1000 K, respectively. A diluted gas mixture of CH4(methane) and hydrogen was used, at a typical pressure of 50 Torr.
Advantages and Appilications
The new diamond coated burs obtained by this process are adaptable to the handpiece of any ultrasonic instrument commonly used in dental offices for calculus removal.
The new dental diamond bur consists of a continuous film of diamond without a metallic binder between crystals, preventing the contamination of the tooth by metal ions usu- ally present in the binder matrix of conventional burs.
The CVD burs are also highly resistant to cutting and demonstrate efficient cutting ability and longevity. Some researchers demonstrated that CVD diamond burs used for cavity preparation .
REF: Braz Oral Res 2006;20(2)
Diamond and Related Materials 5(1996)857- 860
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