Preparation of TiB<sub>2</sub>-TiN Double Layer Coated Iron Powder by Rotary Powder Bed CVD

Abstract

A composite iron powder coated with TiB2 and TiN double layers was prepared by the continuous rotary powder bed chemical vapor deposition in the reactant systems of TiCl4-B2H6-H2 and TiCl4-N2-H2. TiN was coated on to spherical iron powder with a particle diameter of 70-120μm under the following deposition conditions; temperature: 1000°C, reaction time: 0-120min, flow rate: TiCl4 3ml/min, N2 200ml/min, H2 300ml/min, Ar 20ml/min, and the rotation speed of specimen cell: 90rpm. Crystalline or amorphous TiB2 was subsequently coated on to TiN coated iron powder under the conditions: temperature: 600°-850°C, reaction time: 60-240min, flow rate ratio of B2H6 to TiCl4, R=0.16, H2 300ml/min, Ar 140-300ml/min. The composite iron powder covered with uniform and adherent double layers of TiB2 and TiN was oxidation-resistant up to 700°C in air.