Mechanical Properties of Diamond Films

Diamond has been well-known for long for its outstanding mechanical properties like great hardness and low frictional coeffident Therefore, it was self-suggesting to examine the respective characteristics of diamond films as well. Actually the results are found to vary depending on the morphology of the film and, for polycrystalline materials, on the particle size. 

Like in any material, the mechanical properties of diamond films have chemical reasons. The basic effect underlying friction is the making and breaking of 

Measuring the tribological properties of diamond films turns out to be rather complicated for several reasons. For running such an experiment between two diamond objects, the tip or ball of the tribometer has to be coated with diamond too, which constitutes a technological challenge. Using softer tips instead may in some cases lead to a material transfer from the tip to the diamond surface under test, resulting in a modified surface with altered mechanical properties. The surface coarseness is also complicated to measure and hard to adjust Finally, problems in the diamond film s adhesion to the substrate constitute another parameter to be controlled. 

The reconstruchon of the surface plays an important role especially for monocrystalline diamond films, but polycrystalline materials are affected too. The it-bonds aheady existing on such diamond faces largely fadhtate a graphitization, which manifests in a strong reduction of the friction coefficient at very high temperatures (when graphitization assumes a significant extent). 

The attrition of a diamond film is promoted by a high portion of sp -material. The grain boundaries in UNCD represent predetermined breaking points and facilitate fracture of the film. The comparatively low elasticity of diamond contributes to its friability as well. Furthermore, sp -carbon atoms are more easily oxidized at contact with air, leading to material losses of the film which thus might become porous upon strong wear. 

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Catledge, S., and Vohra, Y., Effect of nitrogen addition on the microstructure and mechanical properties of diamond films grown using high-methane concentrations. /. App. Phys. 86 (1), 698-700 (1999). 

These defects are generally detrimental to electronic, thermal and mechanical properties of diamond films, although in some cases they may be neutral or beneficial. The frequently occurring defects appear to be stacking faults (twinned clusters with many re-entrant surfaces/comers), which are deemed to play a major role in enhancing diamond growth rates.t ... 

K. Baba, and Y. Aikawa, Mechanical properties of diamond films by a filament assisted chemical vapor deposition, NEC Research and Development, 34 (2) 176-182 (1993)... 

Mechanical properties of diamond-like carbon (DLC)thin films... 

Gielisse, P.J. (1998). Mechanical properties of diamond, diamond films, diamondlike carbon and like-diamond materials. In Handbook of Industrial Diamonds and Diamond Films (M.A. Prelas, G. Popovici, and L.K. Bigelow, eds). Marcel Dekker, Chapter 3, pp. 49—88. 

C.J. McHargue. Mechanical Properties of Diamond and Diamond-Like Films. In Y. Tzeng, M. Yoshikawa, M. Murakawa, and A. Feldman, editors, Applications of Diamond Films and Related Materials. Materials Science Monographs, Volume 73. Elsevier, New York, 1991, p. 113. 

A.H. Deutchman and R.J. Partyka (Beam Alloy Corporation observe, "Characterization and classification of thin diamond films depend both on advanced surface-analysis techniques capable of analyzing elemental composition and microstructure (morphology and crystallinity), and on measurement of macroscopic mechanical, electrical, optical and thermal properties. Because diamond films are very thin (I to 2 micrometers or less) and grain and crystal sizes are very small, scanning electron microscopy... 

The excellent properties of the diamond like materials combined with the low deposition temperature and high deposition rate, make these coatings very promising materials for the future. They have many potential applications as protective coatings for industrial products. Of course the properties of diamond like films never match those of diamond. The films are intrinsically smooth and amorphous, and can be used in coating applications where a plane, mechanically hard and wear/corrosion resistant surface is desirable. 

Owing to remarkable mechanical properties Hke great hardness, scratch resistance and a low frictional coefficient in combination with a high tolerance for aggressive environmental conditions, diamond-coated objects have been developed soon after the first preparation of diamond films. Today the respective products are employed in many technical apphcations. 

GPa and from 70 to 30 GPa, respectively. The hardness values obtained for the diamond/p-SiC composite fdms at lower and moderate TMS flow rates can be directly related to the high density of the interfaces or grain boundaries present in the fdms owing to the nanocrystallinity of both the phases. Frictional and mechanical properties of the diamond/p-SiC nanocomposite fdms clearly indicate that p-SiC volume fraction can be considered as an important compositional factor to determine any physical properties of the nanocomposite film system. 

Dynamic mechanical analyzer n. An instrument that can test in an oscillating-flexural mode over a range of temperature and frequency to provide estimates of the real , i.e., in-phase, and imaginary , i.e., out-of-phase parts of the complex modulus. The real part is the elastic component, the imaginary part is the loss component. The square root of the sum of their squares is the complex modulus. With polymers, the components and the modulus are usually dependent on both temperature and frequency. ASTM D 4065 spells out the standard practice for reporting dynamic mechanical properties of plastics. An example of a DMA thermogram of different Perkin-Elmer Inc., manufactures the Diamond DMA instrument. Polymer films is shown. Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York. 

Hoffman, A., Mechanism and properties of nanodiamond films deposited by the DC-GD-CVD process, in Synthesis, Properties and Applications of Ultrananocrystalline Diamond, Gruen, D., Shenderova, O., VuT A.Ya., eds., NATO Science Series II Mathematics, Physics and Chemistry. Springer, Dordrecht, 192, 125, 2005. 

The determination of mechanical properties of periodically re-crystallized Pt thin films has been performed using a nanoindentation test. The sample surface was subjected to a loading — unloading cycle with a Berkovich diamond tip. Using the calculation method developed by Oliver and Pharr,local measurements of both hardness H) and Young modulus E) of the thin Pt films have been carried out. 

Diamond and Refractory Ceramic Semiconductors. Ceramic thin films of diamond, sihcon carbide, and other refractory semiconductors (qv), eg, cubic BN and BP and GaN and GaAlN, are of interest because of the special combination of thermal, mechanical, and electronic properties (see Refractories). The majority of the research effort has focused on SiC and diamond, because these materials have much greater figures of merit for transistor power and frequency performance than Si, GaAs, and InP (13). Compared to typical semiconductors such as Si and GaAs, these materials also offer the possibiUty of device operation at considerably higher temperatures. For example, operation of a siUcon carbide MOSFET at temperatures above 900 K has been demonstrated. These devices have not yet been commercialized, however. 

H. Nakazawa, A. Sudoh, M. Suemitsu, K. Yasui, T. ltoh,T. Endoh, Y. Narita, M. Mashita, Mechanical and tribological properties of boron, nitrogen-coincorporated diamond-like carbon films prepared by reactive radio-frequency magnetron sputtering., Diamond and Related Materials, vol. 19, pp. 503-506, 2010. 

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