Development Of Nanocrystalline Materials Research Articles

Preliminary investigation on development of functionally graded cemented tungsten carbide with solid lubricant via ball milling and spark plasma sintering

Functionally graded cemented tungsten carbide belongs to a hybrid Functionally Graded Materials family. However synthesis of functionally graded cemented tungsten carbide is a great challenge due to possibility of “Co migration” and CaF2 vaporization during liquid phase sintering. Hence the present work deals with the development of nanocrystalline materials using ball milling and consolidation of milled material by Spark Plasma Sintering (SPS) for the preparation of functionally graded cemented tungsten carbide. The effects of ball milling and contents of Co, CaF2 and WC on WC/Co/CaF2 powder mixture were analyzed. Grain morphology, particle size, micro-strain, crystallite size, etc. of milled samples were investigated using scanning electron microscopy and X-Ray diffraction techniques. In addition to that, density, microstructure, hardness, fracture toughness and residual stress of consolidated sample are also reported. These tests confirm the formation of nanocrystalline particles and sub-sequent consolidation of functionally graded cemented tungsten carbide with solid lubricant. Hence ball milling with SPS is a prominent and viable process combination for the preparation of functionally graded cemented tungsten carbide.

The Development of Nanocrystalline Materials Prepared by Electrodeposition

The characteristics and the synthesis principle of nanocrystalline materials prepared by electrodeposition are summaried in this paper. The research status of nanocrystalline materials and the common methods preparing nanocrystalline materials are reviewed, such as direct current electrodeposition, pulse electrodeposition, composite electrodeposition and jet electrodeposition. Finally, some prospects on development and applications of nanocrystalline materials in material science are proposed in this paper.

An analysis of creep deformation in nanocrystalline materials

The creep deformation characteristics of crystalline materials with grain sizes of > 1 pm have been studied for over four decades, from both the experimental and theoretical viewpoints. Recently there has been considerable interest in the development of nanocrystalline materials with grain sizes of $< 0.1 \mu m$ in which there is a significant increase in the volume fraction of a material occupied by grain boundaries and other intercrystalline defects such as triple lines and quadruple junctions [l-3].