Self-Lubricating, TiN-MoS 2 Composite Coatings Produced by Simultaneous Deposition from Ti ((CH 3 ) 2 N) 4 /NH 3 /MoF 6
- PDF / 878,407 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 48 Downloads / 149 Views
231 Mat. Res. Soc. Symp. Proc. Vol. 363 01995 Materials Research Society
EXPERIMENTAL The CVD reactor used in the present study is described in detail elsewhere. 4 Precursors were composed of Ti((CH3 ) 2N) 4, (99.9 %, Strem Chemicals Inc., Newburyport, MA), MoF 6 (99.9 %, Johnson & Matthey, Wardhill, MA), NH3 (99.95 %, Alphagaz, Morrisville, PA), 150 g of Ti((CH3) 2N) 4 was contained in and H2 S (99.5 %, Alphagaz). a 200-cm3 stainless steel bubbler (Morton international, Danvers, MA) maintained at 313 K by a silicon-oil bath with an immersion circulator. Ultra-high-purity Ar (99.995 %, Alphagaz) at 20 cm3 /min (STP) was passed through the bubbler to carry the vaporized To prevent premature reactions precursor to the reaction zone. among the reagents, gas flows were separated by using a dual-pass, 4 co-axial gas injector so that they mixed at a point -8 cm from the The flow rates of the leading edge of the graphite susceptor. gases were Ar (diluent):700, NH3 : 200, and H2 S: 60 cm3 /min (STP). Deposition was carried out at 1073 K and a system pressure of 1.3 kPa. Graphite substrates were placed on a 13-cm long graphite susceptor which was inductively heated by a radio frequency generator (164 kHz). A K-type thermocouple in contact with the graphite susceptor was used to measure temperatures. Chemical composition and microstructure of the deposits were studied by means of X-ray diffraction (PAD V, Scintag, Sunnyvale, CA), Auger electron spectroscopy (AES) (PHI 660, Perkin Elmer, Eden Prairie, MN), and transmission electron microscopy (TEM) (HF-2000, Hitachi, Tokyo, Japan). Kinetic friction coefficients of the composite coatings were determined by means of a computercontrolled friction microprobe with a type 440C stainless steel slider. The details on the instruments and the measurements of kinetic friction coefficients can be found elsewhere. 5 RESULTS AND DISCUSSIONS Fig. 1 shows the X-ray diffraction pattern of a composite coating containing both TiN and MoS 2 deposited at 1073 K and a The peaks marked with partial pressure of MoF 6 (PMoF6) = 9.6 Pa. asterisks are attributed to the graphite substrate. Peaks arising from both cubic TiN and hexagonal MoS 2 were readily identified. The orientation of MoS 2 crystallites in the coating is such that the (002) planes are aligned parallel to the coating surface which is highly desirable for lubrication. Fig. 2 shows AES spectra of the coating obtained after sputtering for (a) 2, (b) 15, and (c) 40 min with a 3.5-kV Ar+ion beam. Signals corresponding to Mo, S, Ti, and N were detected over the probed area of 1 mm2 . Carbon and oxygen content in the coating The was found to be below the detection limit of the instrument. The carbon peak in Fig. 2(c) is from the graphite substrate. atomic ratio of Ti to N, determined from the peak-to-peak heights, confirmed the formation of stoichiometric TiN. The Mo/S ratio was, however, found to be larger than 0.5, which could be attributed to The the preferential sputtering of S over the heavier Mo atoms. atomic ratio of Mo to Ti was foun
Data Loading...
