Attempt to design a strong solid.
TL;DR: In this paper, it was shown that by using alternate layers of materials with high and low elastic constants resolved shearing stresses of the order of ε( √ n ϵ(n 2 ) −1 −1/n −1 )$ will be required in order to drive dislocations through the combination.
Abstract: It is shown that by using alternate layers of materials with high and low elastic constants resolved shearing stresses of the order of $\frac{{\ensuremath{\mu}}_{\mathrm{low}}}{100}$ will be required in order to drive dislocations through the combination. The layers should be so thin that a Frank Read source cannot operate inside one layer. The low-elastic-constant material should be such that perfect dislocations rather than partials occur in bulk specimens of the material. Several possible combinations are suggested.
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TL;DR: In this article, the authors discuss the concept of nanocomposite coatings with high hardness and low elastic modulus, which can exhibit improved toughness, and are therefore better suited for optimising the wear resistance of real industrial substrate materials (i.e., steels and light alloys, with similarly low moduli).
2,252 citations
TL;DR: The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed in this article, where two basic approaches are outlined including the intrinsic superhard material, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure.
Abstract: The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of C3N4 has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nc-TiN/SiNx nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of de...
1,122 citations
TL;DR: In this article, the effects of size on predominantly mechanical properties of materials are reviewed at a first-order level, and important aspects can be understood from the point of view of the interaction of a characteristic length (which may be as diverse as the dislocation radius of curvature at a given stress or the magnetic exchange length) with a size parameter (grain or particle size, or film thickness).
1,068 citations
TL;DR: High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike as discussed by the authors, also known as HIPIMS (high power impulse...
Abstract: High power pulsed magnetron sputtering (HPPMS) is an emerging technology that has gained substantial interest among academics and industrials alike. HPPMS, also known as HIPIMS (high power impulse ...
846 citations
TL;DR: In this paper, a review of the current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings is addressed. And the properties of transition metal nitride nanocrystine films formed by ion beam assisted deposition process.
Abstract: In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of ∼0.1 to 0.3 μm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value (∼10–20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall–Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process.
832 citations