Porosity apparent

Material Pyrometer cone equivalent Main crystalline phases Bulk Tme Apparent porosity, %... 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

Type of brick Typical composition Approx. bulk density, Ib/fF Fusion point, F. Cbemical nature Deformation under hot loading Apparent porosity, % Perme- abibty Hot strength Thermal shock resistance Cbemical resistance ... 

Body Tensile strength (MN/m ) Com- pressive strength (MN/m ) Modulus of rupture (MN/m ) Apparent porosity m Thermal Young s conductivity modulus (Wm- K- )(GN/m ) Thermal expansion coefficient 0-500°C (mm/mm°C)... 

Fig. 1.18A shows the pore size distribution for nonporous methacrylate based polymer beads with a mean particle size of about 250 pm [100]. The black hne indicates the vast range of mercury intrusion, starting at 40 pm because interparticle spaces are filled, and down to 0.003 pm at highest pressure. Apparent porosity is revealed below a pore size of 0.1 pm, although the dashed hne derived from nitrogen adsorption shows no porosity at aU. The presence or absence of meso- and micropores is definitely being indicated in the nitrogen sorption experiment. 

Apparent porosity is the ratio of total volume of open pores in a porous body to its bulk volume (BS EN 623-2, 1993). 

Sample Sample code Apparent density (Buoyancy method) (gem 3) Apparent porosity (%) Theoretical porosity (%) True density (Helium pycnometry) (gem 3)... 

These relationships have also been applied to sedimentation where the problem of dealing with particles that are aggregated into sedimentation units with properties similar to floes has been recognized [43]. Such units effectively immobilize a relatively large volume of fluid, thus reducing the apparent porosity. In this situation Scott [44] replaced s in equation (6.94) by an effective porosity. 

The type II isotherm is associated with solids with no apparent porosity or macropores (pore size > 50 nm). The adsorption phenomenon involved is interpreted in terms of single-layer adsorption up to an inversion point B, followed by a multi-layer type adsorption. The type IV isotherm is characteristic of solids with mesopores (2 nm < pore size < 50 nm). It has a hysteresis loop reflecting a capillary condensation type phenomenon. A phase transition occurs during which, under the eflcct of interactions with the surface of the solid, the gas phase abruptly condenses in the pore, accompanied by the formation of a meniscus at the liquid-gas interface. Modelling of this phenomenon, in the form of semi-empirical equations (BJH, Kelvin), can be used to ascertain the pore size distribution (cf. Paragr. 1.1.3.2). 

Such a structure is termed macroporous with a typical average pore diameter of about 150 nm and a pore size range from several tens to several hundred nanometres. By comparison a gel resin is characterized by an apparent porosity of no greater than about 4 nm which represents the average distance of separation of polymer chains. This difference in structural characteristics of gel and macroporous resins is clearly evident when comparing Figures 3.2a and 3.2b. 

Apparent porosity is very important in connection with flux corrosion and with thermal insulation which may be unfavourably affected by permeation of hot gases. The total volume of open pores can be determined, for example, by measuring the amount of absorbed water, but this value provides no information on pore size which is important with respect to these properties. The permeability for gases is therefore measured. The test specimen is fixed in a special vessel so that it allows a gas or air to be driven through. The gas permeation rate and the pressure difference are measured. The permeability coefficient K is then given by the equation... 

FIG, 1S2, The effect of temperature on the sintering of porcelain-type materials. The dashed line indicates the actual porosity, the full line represents apparent porosity. 

ASTM C 948 Test Method for Dry and Wet Bulk Density, Water Absorption, and Apparent Porosity of Thin Sections of Glass-Fiber Reinforced Concrete, The American Society for Testing and Materials, West Conshohocken, PA. 

ASTM C373-88. (2006) Standard Test Method for Water Absorption, Bulk Density, Apparent Porosity, and Apparent Specific Gravity of Fired Whiteware Products, American Society for Testing Materials. 

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