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Fine Microstructure (fine + microstructure)
Selected AbstractsEffect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001Tohru S. Suzuki To obtain dense, fine-grained ceramics, fine particles and advanced powder processing, such as colloidal processing, are needed. Al2O3 and ZrO2 particles are dispersed in colloidal suspensions by electrosteric repulsion because of polyelectrolyte absorbed on their surfaces. However, additional redispersion treatment such as ultrasonication is required to obtain dispersed suspensions because fine particles tend to agglomerate. The results demonstrate that ultrasonication is effective in improving particle dispersion in suspensions and producing a homogeneous fine microstructure of sintered materials. Superplastic tensile ductility is improved by ultrasonication in preparing suspensions because of the dense and homogeneous fine microstructure. [source] Further Improvement in Mechanical Properties of Highly Anisotropic Silicon Nitride CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2000Hisayuki Imamura Si3N4ceramics were fabricated by tape casting of a raw-powder slurry seeded with three types of rodlike ,-Si3N4particles. The effects of seed size on the microstructure and mechanical properties of the sintered specimens were investigated. All the seeded and tape-cast silicon nitrides presented an anisotropic microstructure, where the elongated grains grown from seeds were preferentially oriented parallel to the casting direction. The orientation degree of these grains, f0, was affected by seed size, and small-seed addition led to the highest f0value. This material exhibited high bending strength (,1.4 GPa) and high fracture toughness (,12 MPa.m1/2) in the direction normal to the grain alignment, which were attributed to the highly anisotropic and fine microstructure. [source] Mechanochemical Formation of Metal,Ceramic CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2000Nicholas J. Welham A mechanical activation technique has been used to form composites of alumina with titanium carbide, nitride, or carbonitride, both with and without elemental iron. The composites were formed by reacting elemental aluminum with either ilmenite (FeTiO3) or rutile (TiO2) concentrates in the presence of carbon and/or nitrogen in a ball-mill at ambient temperature. The reaction was complete for the ilmenite samples after milling but was completed only for rutile under hot pressing conditions. Microhardness measurements indicated that the composites had hardnesses in the range 19,30 GPa (1740,2750 VHN), with only a small variation within each sample. Elemental mapping of the pressed pellets indicated that titanium and aluminum were evenly distributed on a submicrometer level whereas iron tended to coalesce into <20 ,m particles in the presence of TiC. The coalescence decreased with the carbon content of the hard material until iron was evenly distributed with TiN. A superstoichiometric amount of aluminum led to the formation of iron,aluminum phases which decreased the iron coalescence. The XRD crystallite size of the alumina was 30,50 nm and was 25,50 nm for the titanium phases, confirming the extremely fine microstructure. [source] Microstructure and Properties of Pressureless Sintered HfB2 -Based Composites with Additions of ZrB2 or HfC,ADVANCED ENGINEERING MATERIALS, Issue 10 2007L. Silvestroni Ternary HfB2 -ZrB2 and HfB2 -HfC composites (see figure) with 20,vol.-% MoSi2 were produced from commercial powder and densified through pressureless sintering. Dense materials with fine microstructures were obtained at 1900,1950,°C. Flexural strength at 1500,°C confirmed the excellent stability of the composites at high temperature. [source] Microstructural characterization of laser surface melted AISI M2 tool steelJOURNAL OF MICROSCOPY, Issue 3 2010J. ARIAS Summary We describe the microstructure of Nd:YAG continuous wave laser surface melted high-speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X-ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M2C carbides with different morphologies were identified in the resolidified surface layer after laser melting. [source] | ||||||||||