Superhard Rhenium Diboride Films: Preparation and Characterization

Latini, Alessandro; Rau, Julietta V.; Ferro, D.; Teghil, R.; Albertini, V. Rossi; Баринов, С. М.

doi:10.1021/cm800398s

Cited by 68 publications

(63 citation statements)

References 19 publications

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“…[7,8] In fact, this is what was observed in our previously published reports on arc-melted ReB 2 [2,3,5] and recently confirmed by others using superhard thin films of ReB 2 (H v ¼ 52 GPa) grown by a pulsed laser deposition technique. [2,3,5,17] So why does the material synthesized by Qin et al exhibit such large discrepancies in properties compared to our past and present work? The answer likely lies in understanding their synthetic process.…”

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confidence: 53%

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Shear Modulus of Polycrystalline Rhenium Diboride Determined from Surface Brillouin Spectroscopy

et al. 2009

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The critical use of superhard materials in modern industry ranges from polishing and cutting tools to wear-resistant coatings. This emphasizes one of the most challenging problems in materials science, especially in the field of superhard materials, which is the accurate characterization of a material's mechanical and elastic properties. Recently, Qin et al. synthesized ReB 2 compacts under high pressure/high temperature (HPHT) conditions and measured the elastic constants via an ultrasonic method.[1] They reported values for the Vickers hardness and elastic moduli well below the previously published theoretical and experimental data and therefore claim that ReB 2 does not belong in the class of superhard materials. [2][3][4][5] Due to existing doubts regarding the mechanical robustness of ReB 2 we have synthesized powder compacts of ReB 2 by spark plasma sintering (Fig. 1) to perform independent studies of the elastic moduli. [6] The present study will demonstrate that the shear modulus, which is an excellent predictor of hardness, [7,8] of the recovered polycrystalline sample, is significantly higher than the value reported by Qin et al. Surface Brillouin spectroscopy (SBS), an experimental technique that is based on the inelastic scattering of light, is utilized in this study. Additionally, some of the more subtle differences between the work performed by Qin et al. and ours will be discussed in an effort to elucidate the origin of the drastically different results reported by each group.The nondestructive characterization of materials by SBS has been successfully used to constrain the elastic parameters of a broad range of systems from polymers to superhard materials. [9,10] The details of the experimental setup, the principles of how this works, and the technical characteristics can be found elsewhere.[11] Briefly, a diode pumped laser (Coherent Verdi-2) with l ¼ 532.1 nm wavelength light was focused on the sample surface and a six-pass tandem Fabry-Perot interferometer (Sandercock model) was used for the spectral measurements. The Brillouin spectra were measured in back-scattering geometry.Typical Brillouin spectra of a compacted ReB 2 pellet are shown in Figure 2. The strongest symmetric peaks are related to inelastic scattering of photons on surface acoustic Rayleigh wave phonons and provide the Rayleigh wave velocity (V RW ) through the relation:where n is the Brillouin shift associated with the peak position of the strongest symmetric peaks, and u is the scattering angle. Equation 1 can also be used to estimate the longitudinal sound velocity (V L ) in the sample using the weaker Brillouin peaks (at higher frequencies, Fig. 2) that result from the propagation of the longitudinal lateral leaky wave in the bulk material.[12] Each spectrum, which consists of the sum of individual spectra that were collected for approximately one hour, was accumulated over 10 and 20 hours in total to improve the very low signal-to-noise ratio of the Brillouin peaks associated with the longitudinal lateral leaky wave in indi...

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confidence: 53%

“…We do not doubt that a densified compact of (ReB 2 þ 0.5B) has a Vickers hardness of %20 GPa and a shear modulus of 169 GPa, however, it is misleading to suggest that this material is the same as the ReB 2 previously reported. [2,3,5,17,21] Further work is now in progress to characterize the elastic parameters of ReB 2 using single crystals.…”

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confidence: 99%

Shear Modulus of Polycrystalline Rhenium Diboride Determined from Surface Brillouin Spectroscopy

et al. 2009

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“…[102] An initial target was synthesized by melting rhenium and boron powder to form ReB 2 . Pulsed laser deposition was used to evaporate the target and collect the material on a SiO 2 substrate.…”

Section: The Future Of Superhard Metal Boridesmentioning

confidence: 99%

“…[103][104][105][106] The intrinsic hardness for the deposited ReB 2 film was (52 AE 6) GPa, exceeding the hardness of any other metal diboride coating and in good agreement with the bulk samples prepared by arc-melting. [62,102] Pulsed laser deposition has also been used to prepare superhard ruthenium boride films. [107] Starting from a pure RuB 2 target, a biphasic ruthenium boride film composed of RuB 2 and Ru 2 B 3 was deposited on an SiO 2 substrate with an average thickness of (0.7 AE 0.1) mm.…”

Section: The Future Of Superhard Metal Boridesmentioning

confidence: 99%

Advancements in the Search for Superhard Ultra‐Incompressible Metal Borides

Levine

Tolbert

Kaner

2009

Adv Funct Materials

336

232

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Dense transition metal borides have recently been identified as superhard materials that offer the possibility of ambient pressure synthesis compared to the conventional high pressure, high temperature approach. This feature article begins with a discussion of the relevant physical properties for this class of compounds, followed by a summary of the synthesis and properties of several transition metal borides. A strong emphasis is placed on correlating mechanical properties with electronic and atomic structure of these materials in an effort to better predict new superhard compounds. It concludes with a perspective of future research directions, highlighting some recent results and presenting several new ideas that remain to be tested.

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“…To overcome these problems, study on other super-hard materials continues vigorously. In 2007 a material, which does not present chemical reactivity problems toward ferrous alloys and have very high hardness -rhenium diboride (ReB 2 ) [14,15], was proposed. The same advantages due to the high valence electron density and bond covalence should manifest tungsten tetra-boride WB 4 [10].…”

Section: Introductionmentioning

confidence: 99%