Machinable nanocomposites

Because nanocomposites are made from different phases with different thermal expansion coefficients and elastic moduli, they inevitably develop residual thermal stress during cooling after sintering. Assuming the dispersion phase is spherical particulate in the matrix material, residual stresses can be developed due to differences in the thermal expansion and elastic constants between the matrix and the particles [23]  

Design and fabrication of strong machinable ceramics is emerging as an inevitable requirement for flexible use of advanced ceramics, especially for 

15 Schematic and TEM image of crack pinning by a nanoparticle and transgranular fracture induced by intragranular particle. 

Niihara, K., New design concept of structural ceramics - ceramic nanocomposites, J. Ceram. Soc. Jap., 99(10) 974-982 (1991). 

Parthasarathy, T.A., Boakye, E., Cinibulk, M.K., and Perry, M.D., Fabrication and testing of oxide/oxide microcomposites with monazite and hibonite as interlayers, J. Am. Ceram. Soc., 82(12) 3575-3583 (1999). 

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Uno T, Kasuga T, Nakayama S., and Ikushima A., "Microstructure of Machinable Nanocomposite Glass-Ceramic,"/. Jpn. Powder Powder MetalL, 39, 1067-71 (1992). 

Si3N4/BN Wear behaviour and machine stability, resistance against metals, high thermal shock resistance. Hot pressed nanocomposite with high strength and improved machinability BN retard the sintering, materials with higher BN content are difficult to sinter [553-556] [366]... 

Wu, H.Z., Roberts, S.G. and Derby, B. Residual stress and subsurface damage in machined alumina and alumina/silicon carbide nanocomposite ceramics , Acta Mater. 49 (2001) 507-517. 

The super-fine dispersoids with laminar structure and a low modulus could be expected to play a crucial role in improving the machinability of ceramics and their mechanical properties. Among the various nanocomposites, h-BN reinforced composites showed excellent corrosion resistance to molten metal... 

T.Kusunose, T.Sekino, Y.H. Choa, and K. Niihara, Machinability of Silicon Nitride/Boron Nitride Nanocomposites, J. Am. Ceram. Soc., 85, 2689-95(2002). 

J. Fischer and B. Stawarczyk. Compatibility of machined Ce-TZP/Al203 nanocomposite and a veneering ceramic. Dent. Mater., 23, 1500-05 (2007),... 

HDPE-CaC03 nanocomposites were prepared by mixing (melting) the individual components in a twin-screw extruder. Mixing was performed at a temperature of 210-220 °C with a screw speed of 15-25 rpm over 5 min. Test samples were obtained using a casting under pressure method on casting machine at 200°C and a pressure of 8 MPa. 

The nanocomposite EP/MMT samples were prepared in three stages. The samples were first cured isothermally for up to 8 h at temperatures of 80, 100, 120 and 140°C, followed by 8 h at 180°C and finally 12 h at 220°C under vacuum. The samples were cooled down at a rate of 1-2 C/ min and 20 5 1 mm pieces were machined for dynamic spectroscopy measurements. MMT contents in the studied nanocomposites were 2, 5, 10 or 15 mass%. 

It was seen in figure 18 of PLM picture, the distribution of RSF in the RSF/PP nanocomposite was good, which indicated the minilab extruder with a cycle system was a suitable machine to compound the polymer and cellulose fibrils. 

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