1. Neelkanth G. Dhere and Anil Pai
Development of Tribological Coatings for Cryocoolers Task III. 4 Hydrogen Storage for Spaceport and Vehicle Applications
Neelkanth G. Dhere and Anil Pai

2. Titanium Nitride (TiN) Coatings - By RF Magnetron Sputtering
The 6” six-way cross vacuum chamber was tested for vacuum leaks. Leaks were eliminated so as to improve the vacuum from 8x10-5 Torr to 6.1x10-6 Torr.
Initial depositions of TiN (hard coating) were done by reactive magnetron sputtering on glass substrate.
RF cable from the RF tuner to the target was shortened to obtain an impedance matching at the RF frequency of MHz and consequently to minimize the reflected power. As a result thickness of coatings improved.

3. Titanium Nitride (TiN) Coatings - By RF Magnetron Sputtering
Depositions were carried out by varying the proportion of nitrogen to argon sputtering gas and using forward power in the range of watt, reflected power of 1-2 watt.
This resulted in >5000 Å TiN thin films.
Visual inspection and sheet resistance measurements have shown the films to be deficient in nitrogen.

4. Titanium Nitride (TiN) Coatings - By DC Magnetron Sputtering
DC Magnetron Sputtering was used to achieve film thicknesses of > 1 micron
Number of Depositions have been carried out by DC Magnetron Sputtering under varying conditions.
Achieved film thickness of > 1 micron.
Analysis by Energy Dispersive Spectroscopy (EDS) has been carried out for three samples and the results are shown in the following slides.

5. Titanium Nitride (TiN) Coatings
Data showing deposition parameters of samples used for EDS Analysis
Resistivity of Ti * 10-5 Ω -cm
Resistivity of TiN – 2.5 * 10-5 Ω -cm

6. Titanium Nitride (TiN) Coatings
Energy Dispersive Spectroscopy (EDS Analysis)
Films have shown good stoichiometric ratio of Ti & N

7. Titanium Nitride (TiN) Coatings
Results of microhardness measurement carried out with the assistance of Dr. Raj Vaidynathan at UCF
HV –Vicker’s Hardness

8. Titanium Nitride (TiN) Coatings
XRD analysis to be done
TiN-1
TiN-2
Intensity (a.u)
TiN-3
TiN-4
Diffraction Angle (Deg.)
Figure: Extra Slow XRD patterns

9. Titanium Nitride (TiN) Coatings
XRD Analysis would tell us
Orientation of the film – Require (111)
Compound formation and crystallnity of the film – If TiN is fully reacted, peak intensity will be high as in TiN-1
If the grain size is large, peaks will be narrow
There is an optimum grain size for achieving the highest microhardness
XRD equipment at UCF is under repair and so we had to send it to NREL and are awaiting the results

10. Titanium Nitride (TiN) Coatings
Wear and coefficient of friction to be tested at UCF with the assistance of Dr. Chen and his colleagues.
Require deposition of films on a thin glass substrate (1 mm) for the test.
Prepare a silicon sample (1 cm2) with small bumps on the sample by photolithography with the assistance of Dr. Sundaram
TiN coating will be deposited on these bumps to carry out the friction and wear test.
Bumps
Si Sample with
TiNfilm on bump
Sliding
Force
Sliding
Force
TiN Sample

11. Hard Coatings at Cryogenic Temperatures
Literature search of friction behavior and wear resistance of high hardness coatings under cryogenic temperatures
Only diamond-like-carbon (DLC) and nitrides of high-melting metals (e.g. TiN, ZrN) studied
These coatings have shown to have coefficient of friction less than 0.1 at room temperature.

12. Hard Coatings at Cryogenic Temperatures (continued)
Cryogenic environment leads to increase in the coefficient of friction and DLC coatings have lower coefficient of friction and good wear resistance as compared to hard coatings of nitrides.
DLC coatings can be deposited by Microwave assisted plasma chemical vapor deposition system (MWCVD).
A special cryogenic tribometer required for the study.

13. Schedule and Progress Characterization of TiN coatings is being done.
Thru May 31, 2003: Preparation and characterization of TiN, CrN, TiC and MoS2 coatings
Dec 1-Mar 31, 2003: Fabrication and installation of MWCVD
Apr 1 – Aug 31, 2003: Preparation and characterization of DLC coating
Jul 1 – Aug 31, 2003: Improve coatings and prepare report
Characterization of TiN coatings is being done.
Deposition of bilayer coatings of TiN and MoS2 on a glass substrate to be started soon.
Testing of the above film will be carried out for satisfying requirements of good wear resistance and low coefficient of friction coatings.