Volume fraction

About: Volume fraction is a research topic. Over the lifetime, 16312 publications have been published within this topic receiving 374181 citations.

Fabrication process and electrical behavior of novel pressure-sensitive composites

Abstract: A novel route was developed to fabricate a new pressure-sensitive composite by dispersing homogeneously conductive carbon particles in an insulating silicone rubber matrix. The composites showed a gradual change in electrical resistivity with applied pressure within percolation threshold region at a constant temperature. This type of gradual fall of resistivity with applied pressure is very important to fabricate pressure sensors. Various amounts of carbon particles were dispersed in a rubber matrix to understand the effect of volume fraction of conductive filler with applying external pressure on resistivity. A quantitative general effective media (GEM) theory was used to understand the resistivity of carbon–rubber composites system over a large range of volume fraction of carbon with applied pressure. The use of two different sizes of silicon rubber particles showed a significant effect in gradual fall of resistivity with applied pressure in the narrow range of percolation threshold. However, a large variation in resistivity from 1st measuring to 10th measuring was observed. A significant improvement in successive measuring of resistivity variation from 1st measuring to 10th measuring was observed when composites were fabricated in hexane solvent media. Finally, nano-sized Al2O3 was dispersed to control the resistivity variation upon successive measurement and to improve the mechanical properties of the composites. The material was suggested to use as unique materials as pressure sensors in practical applications mainly for robots.

Development of α-phase morphologies during low temperature isothermal heat treatment of a Ti–5Al–5Mo–5V–3Cr alloy

Abstract: Development of different morphologies of the α-phase and their influence on the mechanical properties during low temperature isothermal aging of the near-β titanium alloy Ti–5Al–5Mo–5V–3Cr (Ti-5553) have been studied. A wide variety of different morphologies of the α-phase resulted from variations of the isothermal temperature and/or time. While after aging at 673 K or higher, a Widmanstatten star-shape was the dominant morphology of the α-phase, aging at lower temperatures resulted in the formation of triangular-shaped precipitate morphology. The first α-phase nucleated after 10 min isothermal holding time at 673 K, and the volume fraction increased to more than 80% after 8 h of holding time. This increase in the volume fraction of the α-phase caused an increase in the micro-hardness of the bulk material. X-ray diffraction and microstructural analyses provided evidence of ω-assisted nucleation of the α-phase. It is proposed that this mechanism by which the α-phase nucleates on pre-existing ω-phase particles account for the formation of the very large number of small α-particles that precipitated in the β-matrix.

Mathematical modeling and experimental studies on ohmic heating of liquid-particle mixtures in a static heater

Abstract: Understanding of the ohmic heating of liquid-particle mixtures requires preliminary study and model development within a static heater. A mathematical (3D finite element) model was developed for prediction of temperatures of mixtures of liquids and multiple particles within a static heater. Experiments were conducted using cubic potato particles within sodium phosphate solutions, for various particle sizes, orientations, concentrations, and liquid conductivities. the mathematical model was found to yield satisfactory prediction of experimental trends. Critical parameters affecting the relative heating rates of particles and liquid were the conductivities of the two phases, and the volume fraction of each phase. Ohmic heating appears most promising with high-solids concentration mixtures.