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Special Issue "Hard Materials: Advances in Synthesis and Understanding"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 May 2011)

Special Issue Editor

Guest Editor
Prof. Dr. Natalia Dubrovinskaia

Laboratory of Crystallography, University of Bayreuth, 95440 Bayreuth, Germany
Fax: 05

Special Issue Information

Dear Colleagues,

The hard materials become key elements in modern technologies, such as energy, medicine, transport, communication and electronics. Due to advanced methods of synthesis and the synergy of physical, chemical and engineering techniques for investigations of materials properties, a number of novel hard and superhard materials have been obtained and characterised in recent decade. Many of novel bulk superhard materials are products of the high pressure - high temperature synthesis. Tuning synthesis parameters provides a great potential to vary technologically important thermoelastic and mechanical properties: hardness, fracture toughness, thermal stability, and wear resistance. The properties of hard materials are not always easy to explain and even less so to predict, so that exploration and development of hard and superhard materials is a highly multidisciplinary scientific field challenging both experimenters and theoreticians. In this special issue we aim at covering recent progress and novel trends in various fields of research on hard materials and invite papers reflecting methodological, practical, theoretical, as well as applied aspects of the research on a wide diversity of materials ranging from thin films and single crystals to nanocrystalline and composite materials with particular properties (with emphasis on superconductivity, magnetic and/or electronic ones). Papers covering development in hardness measurements (microhardness testing and nanoindentation), advanced synthesis techniques, and non-traditional superhard materials are of particular interest.

Prof. Dr. Natalia Dubrovinskaia
Guest Editor

Keywords

  • advanced hard materials
  • synthesis of hard materials
  • ab initio predictions of superhard materials
  • hardness measurements
  • hard thin films
  • hard surface coatings
  • nanoindentation technique
  • diamond borides,
  • nitrides
  • carbides
  • nanocrystalline materials

Published Papers (8 papers)

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Research

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Open AccessArticle Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic
Materials 2011, 4(12), 2061-2072; doi:10.3390/ma4122061
Received: 11 October 2011 / Accepted: 10 November 2011 / Published: 29 November 2011
Cited by 3 | PDF Full-text (584 KB) | HTML Full-text | XML Full-text
Abstract
Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in [...] Read more.
Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination with electron energy loss spectroscopy. Polycrystalline B-C-N materials with a cubic type structure were formed under the applied reaction conditions, but the formation of a ternary cubic diamond-like c-BC2N compound, could not be unambiguously confirmed. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Open AccessArticle Mechanical Properties of Titanium Nitride Nanocomposites Produced by Chemical Precursor Synthesis Followed by High-P,T Treatment
Materials 2011, 4(10), 1747-1762; doi:10.3390/ma4101747
Received: 12 September 2011 / Revised: 27 September 2011 / Accepted: 28 September 2011 / Published: 6 October 2011
Cited by 9 | PDF Full-text (863 KB) | HTML Full-text | XML Full-text
Abstract
We investigated the high-P,T annealing and mechanical properties of nanocomposite materials with a highly nitrided bulk composition close to Ti3N4. Amorphous solids were precipitated from solution by ammonolysis of metal dialkylamide precursors followed by heating at 400–700 °C [...] Read more.
We investigated the high-P,T annealing and mechanical properties of nanocomposite materials with a highly nitrided bulk composition close to Ti3N4. Amorphous solids were precipitated from solution by ammonolysis of metal dialkylamide precursors followed by heating at 400–700 °C in flowing NH3 to produce reddish-brown amorphous/nanocrystalline materials. The precursors were then densified at 2 GPa and 200–700 °C to form monolithic ceramics. There was no evidence for N2 loss during the high-P,T treatment. Micro- and nanoindentation experiments indicate hardness values between 4–20 GPa for loads ranging between 0.005–3 N. Young's modulus values were measured to lie in the range 200–650 GPa. Palmqvist cracks determined from microindentation experiments indicate fracture toughness values between 2–4 MPa·m1/2 similar to Si3N4, SiC and Al2O3. Significant variations in the hardness may be associated with the distribution of amorphous/crystalline regions and the very fine grained nature (~3 nm grain sizes) of the crystalline component in these materials. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Figures

Open AccessArticle Nanohardness and Residual Stress in TiN Coatings
Materials 2011, 4(5), 929-940; doi:10.3390/ma4050929
Received: 29 March 2011 / Revised: 27 April 2011 / Accepted: 13 May 2011 / Published: 17 May 2011
Cited by 7 | PDF Full-text (483 KB) | HTML Full-text | XML Full-text
Abstract
TiN films were prepared by the Cathodic arc evaporation deposition method under different negative substrate bias. AFM image analyses show that the growth mode of biased coatings changes from 3D island to lateral when the negative bias potential is increased. Nanohardness of [...] Read more.
TiN films were prepared by the Cathodic arc evaporation deposition method under different negative substrate bias. AFM image analyses show that the growth mode of biased coatings changes from 3D island to lateral when the negative bias potential is increased. Nanohardness of the thin films was measured by nanoindentation, and residual stress was determined using Grazing incidence X ray diffraction. The maximum value of residual stress is reached at −100 V substrate bias coinciding with the biggest values of adhesion and nanohardness. Nanoindentation measurement proves that the force-depth curve shifts due to residual stress. The experimental results demonstrate that nanohardness is seriously affected by the residual stress. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)

Review

Jump to: Research

Open AccessReview Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations
Materials 2011, 4(10), 1648-1692; doi:10.3390/ma4101648
Received: 15 August 2011 / Revised: 13 September 2011 / Accepted: 16 September 2011 / Published: 28 September 2011
Cited by 28 | PDF Full-text (4523 KB) | HTML Full-text | XML Full-text
Abstract
Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of [...] Read more.
Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T) stability, compressibility and hardness is described as obtained from experiments. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Open AccessReview Phase Stability and Elasticity of TiAlN
Materials 2011, 4(9), 1599-1618; doi:10.3390/ma4091599
Received: 11 July 2011 / Revised: 29 August 2011 / Accepted: 31 August 2011 / Published: 15 September 2011
Cited by 23 | PDF Full-text (777 KB) | HTML Full-text | XML Full-text
Abstract
We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient [...] Read more.
We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Open AccessReview The Hardness and Strength Properties of WC-Co Composites
Materials 2011, 4(7), 1287-1308; doi:10.3390/ma4071287
Received: 8 June 2011 / Revised: 4 July 2011 / Accepted: 6 July 2011 / Published: 14 July 2011
Cited by 21 | PDF Full-text (1220 KB) | HTML Full-text | XML Full-text
Abstract
The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, [...] Read more.
The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here between the composite material properties, especially including the material fracture toughness, and the several materials-type considerations of: (1) related hardness stress-strain behaviors; (2) dislocation (viscoplastic) thermal activation characterizations; (3) Hall-Petch type reciprocal square root of particle or grain size dependencies; and (4) indentation and conventional fracture mechanics results. Related behaviors of MgO and Al2O3 crystal and polycrystal materials are also described for the purpose of making comparisons. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Open AccessReview Delocalization of Electrons in Strong Insulators at High Dynamic Pressures
Materials 2011, 4(6), 1168-1181; doi:10.3390/ma4061168
Received: 28 May 2011 / Accepted: 13 June 2011 / Published: 21 June 2011
Cited by 3 | PDF Full-text (254 KB) | HTML Full-text | XML Full-text
Abstract
Systematics of material responses to shock flows at high dynamic pressures are discussed. Dissipation in shock flows drives structural and electronic transitions or crossovers, such as used to synthesize metallic liquid hydrogen and most probably Al2O3 metallic glass. The [...] Read more.
Systematics of material responses to shock flows at high dynamic pressures are discussed. Dissipation in shock flows drives structural and electronic transitions or crossovers, such as used to synthesize metallic liquid hydrogen and most probably Al2O3 metallic glass. The term “metal” here means electrical conduction in a degenerate system, which occurs by band overlap in degenerate condensed matter, rather than by thermal ionization in a non-degenerate plasma. Since H2 and probably disordered Al2O3 become poor metals with minimum metallic conductivity (MMC) virtually all insulators with intermediate strengths do so as well under dynamic compression. That is, the magnitude of strength determines the split between thermal energy and disorder, which determines material response. These crossovers occur via a transition from insulators with electrons localized in chemical bonds to poor metals with electron energy bands. For example, radial extents of outermost electrons of Al and O atoms are 7 a0 and 4 a0, respectively, much greater than 1.7 a0 needed for onset of hybridization at 300 GPa. All such insulators are Mott insulators, provided the term “correlated electrons” includes chemical bonds. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Figures

Open AccessReview The Role Played by Computation in Understanding Hard Materials
Materials 2011, 4(6), 1104-1116; doi:10.3390/ma4061104
Received: 11 May 2011 / Revised: 2 June 2011 / Accepted: 8 June 2011 / Published: 14 June 2011
Cited by 6 | PDF Full-text (517 KB) | HTML Full-text | XML Full-text
Abstract
In the last decade, computation has played a valuable role in the understanding of materials. Hard materials, in particular, are only part of the application. Although materials involving B, C, N or O remain the most valued atomic component of hard materials, [...] Read more.
In the last decade, computation has played a valuable role in the understanding of materials. Hard materials, in particular, are only part of the application. Although materials involving B, C, N or O remain the most valued atomic component of hard materials, with diamond retaining its distinct superiority as the hardest, other materials involving a wide variety of metals are proving important. In the present work the importance of both ab-initio approaches and molecular dynamics aspects will be discussed with application to quite different systems. On one hand, ab-initio methods are applied to lightweight systems and advanced nitrides. Following, the use of molecular dynamics will be considered with application to strong metals that are used for high temperature applications. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)

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