Role of microstructure and structural disorder on tribological properties of polycrystalline diamond films

Ajikumar, P.K.; Ganesan, K.; Kumar, N.; Ravindran, T. R.; Kalavathi, S.; Kamruddin, M.

doi:10.1016/j.apsusc.2018.10.265

Cited by 29 publications

(15 citation statements)

References 36 publications

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“…This results in the removal of tribofilms in the wear track leading to a significant wear rate on both the films. However, the higher wear rate in UNCDN films than that of the UNCDAr films, can be associated with the tribofilms with higher sp 2 content which are easily moved out of the track due to the roughness of the counter body [3,6].…”

Section: Discussionmentioning

confidence: 99%

“…The most acceptable postulates on ultralow friction and wear in UNCD and DLC are either due to surface passivation or rehybridization. Of them, the surface passivation is reasonably explained on the superlubricity in UNCD and DLC films based on tribotests at different environments [3][4][5]21,22]. On the other hand the surface rehybridization, which occurs through the shear pressure leading to either amorphization or graphitization, is a complex phenomenon at atomic-scale with bond breaking and re-bonding at the sliding interface.…”

Section: Introductionmentioning

confidence: 99%

“…The materials with anti-wear and ultralow friction characteristics are the most desirable in mechanical engineering applications where the carbon based materials have potentials to play a major role. Since ultralow friction and negligible wear are demonstrated in ultrananocrystalline diamond (UNCD) and diamond-like carbon (DLC) films at ambient conditions, the research interest is ever increasing drastically over the recent past years [1,2,[11][12][13][14][15][16][17][18][19][20]3,[21][22][23][24][25][26][27][28][29][30]4,[31][32][33][34][5][6][7][8][9][10]. The formation of tribofilms which occurs due to the shear induced graphitization is one of the crucial factors for achieving ultralow friction in carbon materials [5,10,[20][21][22][23][24][25][26]35].…”

Section: Introductionmentioning

confidence: 99%

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Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

et al. 2021

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The origin of ultralow friction and high wear resistance in ultrananocrystalline diamond (UNCD) films is still under active debate because of the perplexed tribochemistry at the sliding interface. Herein, we report a comparative study on surface topography and nanoscale friction of tribofilms, in wear tracks of two sets of UNCD films having different structural characteristics.Despite both the films display ultralow coefficient of friction, the UNCD films grown under Ar atmosphere (UNCDAr) exhibit a high wear resistance while the wear rate is higher for the films grown in N2 (UNCDN). Frictional force microscopic (FFM) investigations clearly reveal the manifestation of shear induced graphitization on both the films. However, the wear track of UNCDAr films have a large network of a few layer graphene (FLG) structures over the amorphous carbon tribofilms while only isolated clusters of FLG structures are present in the wear track of UNCDN films. Here, we demonstrate the direct micro-/nanoscopic evidence for the formation of large network of ~ 0.8 -6 nm thick FLG structures, as a consequence of shear induced graphitization and discuss their decisive role in ultralow friction and wear.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

et al. 2021

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“…Nitrogen doped diamond films were grown by a custom designed HFCVD system and the details could be found elsewhere [31,32]. The diamond films are grown on Si (111) and the substrates were chemo-mechanically polished with micron level diamond paste prior to growth.…”

Section: Experimental Methodsmentioning

confidence: 99%

Structural, Raman and photoluminescence studies on nanocrystalline diamond films: Effects of ammonia in feedstock

Ganesan¹,

Ajikumar²,

Srivastava³

et al. 2020

Diamond and Related Materials

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Herein, we report on the improvement of structural quality and enhancement of photoluminescence (PL) emission for an optimally N doped nanocrystalline diamond (NCD) film.Pure and N doped nanocrystalline diamond films are synthesized on Si by hot filament chemical vapour deposition using NH3:CH4:H2 at different nominal N/C ratios viz. 0, 0.13, 0.35, 0.50 and 0.75 in feedstock. X-ray diffraction analysis reveal a systematic initial increase and then a decrease in crystallite size with N/C ratio in feedstock. Further, a monotonic increase in Raman line width and peak position of diamond band indicates that the compressive strain in diamond lattice increases as a function of N/C ratio upto 0.50. However, at higher N/C ratio of 0.75, the compressive strain gets relaxed a little and produces a lower strain. Furthermore, a unique Raman mode at 1195 cm -1 is observed corresponding to the C=N-H vibrations indicating a significant N concentration in the NCD films. In addition, visible and UV PL studies reveal the presence of several N-related colour centres with multiple emission lines in the range of 380 -700 nm. An optimally N doped diamond film grown at N/C ratio of 0.35 in feedstock shows a significant enhancement in room temperature PL emission at ~ 505 and 700 nm. This PL enhancement is attributed to H3 and other aggregates of N related defect centres, under 355 and 532 nm laser excitations respectively.

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“…To this end, we have synthesized NCD films by a custom designed hot filament chemical vapor deposition and details pertaining to the deposition system are reported elsewhere. 30 Mechanically scratched Si(111) wafer with micron level diamond paste was used as the substrate. CH4 and H2 were used as feedstock gases in the ratio of 3:100 whereas substrate and filament temperature were at ~ 800 and 2000 o C, respectively.…”

Section: Synthesismentioning

confidence: 99%

Si and N - Vacancy color centers in discrete diamond nanoparticles: Raman and fluorescence spectroscopic studies

Ganesan

Ajikumar

Ilango

et al. 2019

Diamond and Related Materials

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The present study reports on an innovative method to prepare discrete diamond nanoparticles or nanodiamonds (NDs) with high structural and optical quality through top-down approach by controlled oxidation of pre-synthesized nanocrystalline diamond (NCD) film. These NDs are studied for their structural and optical properties using atomic force microscopy (AFM), Raman and fluorescence (FL) spectroscopy. While AFM analysis confirms uniform distribution of discrete NDs with different sizes varying from a few tens of nanometers to about a micron, spectroscopic investigations reveal the presence of impurity -vacancy related color centers exhibiting FL at 637 and 738 nm as a function of particle size. In addition, an intense emission originating from vacancy centers associated with N and Si (SiVˉ) is observed for all NDs at the temperature close to liquid nitrogen. A detailed spectral analysis is carried out on the structural defects in these NDs. The full width at half maximum of diamond Raman band ( ~ 1332 cm -1 ) is found to be as narrow as 1.5 cm -1 which reveals the superior structural quality of these NDs.Further, mapping of diamond Raman and FL spectra of SiVˉ confirm the uniform distribution of NDs throughout the substrate. The narrow line widths and a minimal shift in peak positions of Raman and FL spectra endorse this aspect.

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Role of microstructure and structural disorder on tribological properties of polycrystalline diamond films

Cited by 29 publications

References 36 publications

Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

Structural, Raman and photoluminescence studies on nanocrystalline diamond films: Effects of ammonia in feedstock

Si and N - Vacancy color centers in discrete diamond nanoparticles: Raman and fluorescence spectroscopic studies

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