Comparative study of microcrystalline diamond

Obraztsov, A. N.; Timofeyev, M. A.; Гусева, М. Б.; Babaev, V. G.; Valiullova, Z.Kh.; Babina, V. M.

doi:10.1016/0925-9635(94)00264-9

Cited by 23 publications

(12 citation statements)

References 8 publications

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“…The graphiticlike bands in nanocrystalline diamond, on the other hand, have been attributed to the relative increase of the surface sp 2 -bond contributions with decreasing crystallite sizes. 29,43 Our measurements indicate, however, that microstructural variations resulting from different formation conditions are the dominant factor affecting the sp 2 -bond contributions to the Raman spectra over the size range that we measured. For crystallites 250 nm or larger, the STAT DIAM samples ex- 29 studied the influence of the preparation conditions on the Raman characteristics of micrometer-sized diamond crystallites.…”

Section: Discussionmentioning

confidence: 65%

“…29,43 Our measurements indicate, however, that microstructural variations resulting from different formation conditions are the dominant factor affecting the sp 2 -bond contributions to the Raman spectra over the size range that we measured. For crystallites 250 nm or larger, the STAT DIAM samples ex- 29 studied the influence of the preparation conditions on the Raman characteristics of micrometer-sized diamond crystallites. They demonstrated that the Raman signal character was a strong function of the annealing temperature, suggesting Raman sensitivity to structural differences.…”

Section: Discussionmentioning

confidence: 65%

“…Recently, the same authors succeeded in measuring diamond particles of ϳ4.3 nm and observed a shift of about Ϫ11 cm Ϫ1 . 28 Obratzsov et al 29 measured Raman signals from diamond powders with crystallite sizes from 5 nm to 4 m. They reported no significant deviations from bulk Raman spectra, except for the smallest samples which exhibit spectral changes similar to those obtained by Yoshikawa et al 28 The Raman diamond phonons are also affected by stress. Unfortunately, the peak frequencies increase with pressure, opposite to the direction induced by finite-size effects, thus seriously complicating the interpretation of data.…”

Section: Introductionmentioning

confidence: 93%

“…8,24,25,[27][28][29] Namba et al 8 studied diamond particles sized between 120 nm and 14 m and found that as the crystallite size decreases to several thousands of angstroms, the Raman phonon peak broadens asymmetrically, shifts to lower frequencies, and loses intensity. The results from this latter study deviate markedly from the predictions of phonon confinement models, suggesting an incomplete understanding of the relevant physics.…”

Section: Introductionmentioning

confidence: 99%

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Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

et al. 1997

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Micro-and nanocrystalline systems exhibit properties that differ markedly from bulk systems. Diamond, a prototypical system, demonstrates a broadening, shift, and emergence of Raman phonon modes that are believed to originate from finite-size effects. Such information should be useful in constraining confinement models developed to describe the state of these mesoscopic systems. For example, previous investigations have analyzed crystallite size and stresses in scientifically and technologically relevant environments, including chemical-vapor-deposition diamond films and diamond nanocomposites. We have experimentally measured the effect on the diamond Raman phonon modes due to confinement, pressure, and heating effects. At ambient pressure, we present Raman measurements for diamond crystallites ranging from 6 nm to 10 m, which were synthesized by both static and dynamic techniques. The Raman spectra obtained from the statically synthesized samples exhibit a characteristic strong and narrow diamond band, while those dynamically synthesized exhibit both diamond and graphiticlike features. A redshift of the diamond Raman band is observed for decreasing particle size. However, the pressure dependence of the phonon is about the same as that for the bulk system up to 30 kbar for crystallite sizes between 6 and 10 nm. Our measurements also indicate that heating effects from the incident laser dramatically affect the measured Raman spectra. This result leads us to an explanation for discrepancies among previously published results. We show that crystallite size and stress information cannot be determined without compensating for heating effects. Lastly, the phonon confinement model is able to explain the shifts of the Raman modes with size.

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Section: Discussionmentioning

confidence: 65%

Section: Discussionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

et al. 1997

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“…3(a) and 3(b), weak Raman shifts occurred in the cBN (1059 cm −1 and 1310 cm −1 ). Nanophase graphite and amorphous carbon (peak of 1357 cm −1 ) were also found within the samples, [29,30] possibly from the decomposition of B 4 C at HPHT rather than the graphitization of diamond. The peaks of 1583 cm −1 and 1622 cm −1 also indicate that the original C from B 4 C had changed, forming the graphite and amorphous carbon.…”

Section: Phase Structure Characterization By Raman Spectroscopymentioning

confidence: 91%

High thermal stability of diamond–cBN–B₄C–Si composites

et al. 2017

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Improving the thermal stability of diamond and other superhard materials has great significance in various applications. Here, we report the synthesis and characterization of bulk diamond-cBN-B 4 C-Si composites sintered at high pressure and high temperature (HPHT, 5.2 GPa, 1620-1680 K for 3-5 min). The results show that the diamond, cBN, B 4 C, B x SiC, SiO 2 and amorphous carbon or a little surplus Si are present in the sintered samples. The onset oxidation temperature of 1673 K in the as-synthesized sample is much higher than that of diamond, cBN, and B 4 C. The high thermal stability is ascribed to the covalent bonds of B-C, C-N, and the solid-solution of B x SiC formed during the sintering process. The results obtained in this work may be useful in preparing superhard materials with high thermal stability.

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Thin Film Carbon Nanotube Cathodes for Field Emission Flat Panel Display and Light Source Application

Obraztsov

Perspectives of Fullerene Nanotechnology

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The basic and applied aspects of field emission from carbon materials are considered in the example of thin film materials fabricated by using chemical vapor deposition in a plasmaactivated hydrogen-methane gas mixture. The excellent field emission properties were found for the carbon films composed of nanostructured graphite-like material in the shape of nanotubes and nanocrystallites with the predominantly perpendicular orientation of their graphene sheets to the film surface. The threshold values of the macroscopic electric field are less than the emission current densities reach and the emission site density is greater than These properties are analyzed and discussed on the basis of the investigation of the film structure and electronic characteristics by using Raman spectroscopy, electron microscopy, cathodoluminescent technique, photoelectron, and secondary electron spectroscopy. The conclusion about the common nature of low-field electron emission from various carbon materials is made. The model of field emission site and the mechanism of field emission for nanostructured carbon are proposed. The device applicability of the carbon field cathodes is tested. The prototypes of the sealed diode flat-panel display and the triode light source are presented.

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Comparative study of microcrystalline diamond

Cited by 23 publications

References 8 publications

Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

High thermal stability of diamond–cBN–B₄C–Si composites

Thin Film Carbon Nanotube Cathodes for Field Emission Flat Panel Display and Light Source Application

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Comparative study of microcrystalline diamond

Cited by 23 publications

References 8 publications

Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

Nanocrystalline diamond: Effect of confinement, pressure, and heating on phonon modes

High thermal stability of diamond–cBN–B4C–Si composites

Thin Film Carbon Nanotube Cathodes for Field Emission Flat Panel Display and Light Source Application

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High thermal stability of diamond–cBN–B₄C–Si composites