Superior Wear Resistance of Aggregated Diamond Nanorods

Abstract

The hardness of single-crystal diamond is superior to all other known materials, but its performance as a superabrasive is limited because of its low wear resistance. This is the consequence of diamond's low thermal stability (it graphitizes at elevated temperature), low fracture toughness (it tends to cleave preferentially along the octahedral (111) crystal plains), and large directional effect in polishing (some directions appear to be "soft", i.e., easy to abrade, because diamond is anisotropic in many of its physical properties). Here we report the results of measurements of mechanical properties (hardness, fracture toughness, and Young's modulus) of aggregated diamond nanorods (ADNRs) synthesized as a bulk sample. Our investigation has shown that this nanocrystalline material has the fracture toughness 11.1 +/- 1.2 MPa.m(0.5), which exceeds that of natural and synthetic diamond (that varies from 3.4 to 5.0 MPa.m(0.5)) by 2-3 times. At the same time, having a hardness and Young's modulus comparable to that of natural diamond and suppressed because of the random orientation of nanorods "soft" directions, ADNR samples show the enhancement of wear resistance up to 300% in comparison with commercially available polycrystalline diamonds (PCDs). This makes ADNRs extremely prospective materials for applications as superabrasives.

Submicron cubic boron nitride as hard as diamond

“…4 However, the hardness of cBN is much lower than that of diamond (the single crystal cBN has Vickers hardness (Hv) of about 50 GPa, while for single crystal diamond this value is about 60-120 GPa; corresponding values are lower for commercially used polycrystalline cBN and diamond (PCD)). [5][6][7] For decades, various ways have been designed to increase the hardness of polycrystalline cBN, and the synthesis of nanocrystalline cBN seems to be the most effective way. [8][9][10] In polycrystalline materials, grain boundaries can effectively hinder the movements of dislocations and improve the strength, thereby enhance the hardness of polycrystalline aggregates.…”

Evaluating the Wear of Polycrystalline Diamond Compact Drill Bit Cutters using Indentation and Scratch Tests

“…The previous reported value of the hardness and Young's modulus of PDC was within the range 50-60 GPa and 776-925 GPa, respectively, depending on the diamond grain size and the percentage of the cobalt binder which varied from 5% to 20% (Dubrovinskaia, 2006), (Osipov, et al, 2010), and Ndlovu (2009). To prevent large fluctuation in the measurement of material properties, microindentation experiments were carried out.…”

Nucleation and growth of diamond on titanium silicon carbide by microwave plasma-enhanced chemical vapor deposition

“…7a), indicating that the film on Ti 3 SiC 2 has higher fracture toughness [41], which is likely a result of its smaller grain size and non-columnar morphology (Fig. 6) [42]. There is no flaking and film spallation occurred in the film on Ti 3 SiC 2 (Fig.…”