Material-to-void ratio

The amount of material in a mill can be expressed conveniently as the ratio of its volume to that of the voids in the ball load. This is known as the material-to-void ratio. If the solid material and its suspending medium (water, air, etc.) just fill the ball voids, the ratio is 1, for example. Grinding-media loads vary from 20 to 50 percent in practice, and ratios are usually near 1. 

A high volume of powder feed produces a cushioning effect whereas small sample volumes cause a loss of efficiency and abrasive wear of the mill parts. The amount of material to be milled in a ball mill may be expressed as a material-to-void ratio (ratio of the volume of material to that of the void in the ball charge). As the amount of material is increased, the efficiency of a ball mill is increased until the void space in the bulk volume of ball charge is filled then, the efficiency of milling is decreased by further addition of material. 

The grinding media charge can be expressed as a percentage of the mill volume, that is, a mill half-full of media contains a 50% charge. The void space present between a static ball charge is approximately 41%. The quantity of material in a mill can be expressed as the ratio of mill volume to the volume of the voids in the ball load, otherwise known as the material-to-void ratio (M/Vratio). In practice, the M/Vratio is kept close to 1, while grinding media charging varies from 20 to 50%. 

Density, bulk Ratio of weight to volume of a solid material including voids but more often refers to loose form (bulk) material such as pellets, powders, flakes, compounded molding material, etc. 

On the other hand, if no data processing is involved and one is seeking a very weak signal, the absorbance scale can be expanded to 1/3 the signal-to-noise ratio rather than the highest signal. Of course, a linear optical signal requires that the infrared sample have no residual orientation, no voids or holes, and a uniform distribution of material. Careful control of the sample preparation procedure must be achieved in order that reproducible samples are obtained for the infrared examination. 

Biocompatibility and Hemocompatibility Strength of Material Pore Size and Structure Surface-to-Volume Ratio Mass Transport through Device High Degree of Interconnected Cells Void Volume... 

After an extensive review of possible new materials, the team found a material that had a surface-to-volume ratio closer to 1000 M /M and a void volume up to 98%. A hydrophilic coating could be grafted to its surface to provide a reservoir capacity to release nutrients in a controlled manner. Lastly, the hydrophilic coating could be copolymerized with certain bioactive polymers and ligands that improve cell adhesion dramatically. 

The modulus is also said to be a measure of the voids ratio. It has a maximum value of 1 for uniform material, and smaller values if finer or coarser materials are added. When the voids between the large particles are filled with smaller particles the modulus decreases. However, it is hard to conceive that Kramer s modulus is any more suited to such representation than the standard deviation. 

Apparent density ratio of the mass of a solid to the material and void volume. 

Heat conductivity of composite materials are severely and adversely affected by structural defects in the material. These defects are due to voids, uneven distribution of filler, agglomerates of some materials, unwetted particles, etc. Figure 15.18 shows the effect of filler concentration on thermal conductivity of polyethylene. Graphite, which is a heat conductive material, increases conductivity at a substantially lower concentration than does quartz. These data agree with the theoretical predictions of model. Figure 15.19 shows the effect of volume content and aspect ratio of carbon fiber on thermal conductivity. This figure should be compared with Figure 15.17 to see that, unlike electric conductivity which does depend on the aspect ratio of the carbon fiber, the thermal conductivity is only dependent on fiber concentration and increases as it increases. 

POROSITY The ratio of the volume of voids in a material to the total volume of the material including the voids, usually expressed as a percentage. 

The tan

void ratio. The results of the work of Casagrande and Taylor and other facts and relationships known for sands of relatively narrow particle size range were coordinated by Winterkorn into the theory of the solid and liquid states of large-particle (macromeritic) systems. This theory made use of the following long known facts ... 

The concept of the same tan cp value for corresponding void ratios in the case of various gradation ranges of particles possessing the same degree of sphericity and the same coefficient of material friction appears to be quite well justified by experience with Portland cement concrete but appears to be contrary to experience in soil stabilization. The difference lies in the different... 

Materials made of finely divided particles exhibit much higher surface area than bulk materials. Clearly, smaller particles result in an increased dispersion, that is, a higher surface to volume ratio. For pores, the situation is similar, except for the opposite curvature, which is usually negative (concave) for pores, whereas the surface curvature may be seen as mainly positive in the case of nanoparticles. A nanoporous solid is also finely divided but in terms of numbers of cavities or voids. The resulting areas of the exposed surfaces are greatly increased. 

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