Preparation and Mechanical Characterization of Amorphous B-C Films

Abstract

This study has demonstrated that trimethylboron, B(CH3)3 is a suitable boron source material for the fabrication amorphous boron carbide (a-BC:H) films. a-BC:H films were deposited by pluse plasma chemical vapor deposition on a silicon substrate (100) with different gas pressures and gas flow rates at constant voltage, -5 kV . The grown a-BC:H films were found to be porous surface and their thickness were in the range of 0.95 to 1.56 μm for 3 h of deposition time. Results indicated that the boron contents, morphologies and mechanical properties of the a-BC:H films were dependent on the gas pressures and gas flow rate. The increased of boron content will introduce more porous film surface. The effect of boron content on the mechanical properties such as hardness, Youngs modulus, and wear resistance were discussed. The good quality film is obtained from B(CH3)3 at 5 Pa and gas flow rate of 15 cm3/min which boron to carbon atomic ratio is 0.43. This film has lower friction coefficient (0.3) sliding against stainless steel ball, high hardness (8.1 GPa) and Youngs modulus (62.2 GPa).

Tribological and thermal stability study of nanoporous amorphous boron carbide films prepared by pulsed plasma chemical vapor deposition

“…Under 20 000 sliding cycles, the friction coefficient of a -BC:H film is low ( μ : 0.2); this result is consistent with our previous findings in sliding tests of a -BC:H films coated on (100) silicon substrate without any interlayer [16], where the friction coefficient was also 0.2. At low cycles (<20 000), the loose rounded coarse particles or debris are present on the sliding contact of a -BC:H worn surface film, which attach to the steel counter face, creating a transfer layer resulting in the low COF.…”

“…The pore formation on the film surface may be attributed to the oxidation process, which generally occurs during the deposition or post deposition [16, 21, 27]. The black surface area is identified as porous area on the film surface.…”

“…The oxidation process can be divided into three stages. The first one is a pre-oxidation stage, where the deposited a -BC:H film surface shows initial nanopores as a result of the ambient oxygen adsorption [16, 21, 27]. Figure 9 shows the bonding configuration obtained by Gaussian–Lorentzian fitting on the C1s and B1s spectral region in the XPS analysis.…”

“…DLC performance can be improved by alloying it with other elements such as boron, giving rise to a range of attractive physical and mechanical properties as a wear-resistant coating for mechanical systems [12–16]. Furthermore, the doped boron was found to improve the thermal performance of graphite [17], carbon/carbon composites [18] and other forms of carbon materials [19, 20].…”