Apparent density porosity

Apparent Density, Porosity, and Water Contact Angle of PLGA, n-HA/PLGA, and AMX/n-HA/... 

DRI can be produced in pellet, lump, or briquette form. When produced in pellets or lumps, DRI retains the shape and form of the iron oxide material fed to the DR process. The removal of oxygen from the iron oxide during direct reduction leaves voids, giving the DRI a spongy appearance when viewed through a microscope. Thus, DRI in these forms tends to have lower apparent density, greater porosity, and more specific surface area than iron ore. In the hot briquetted form it is known as hot briquetted iron (HBI). Typical physical properties of DRI forms are shown in Table 1. 

Bulk density is easily measured from the volume occupied by the bulk solid and is a strong func tion of sample preparation. True density is measured by standard techniques using liquid or gas picnometry Apparent (agglomerate) density is difficult to measure directly. Hink-ley et al. [Int. ]. Min. Proc., 41, 53-69 (1994)] describe a method for measuring the apparent density of wet granules by kerosene displacement. Agglomerate density may also be inferred from direcl measurement of true density and porosity using Eq. (20-42). 

LP linear polystyrene d diameter S specific surface area Vp specific volume 4> porosity p apparent density. Source Ref. 125. Reproduced with the permission of John Wiley Sons, Inc. 

Density Owing to the variable degree of porosity of the anodic film, it is only possible to determine the apparent density, which varies with the anodising conditions and also with the film thickness. 

They are highly porous conglomerates and, because of their large porosity, the nodules are very light, with an apparent density of only about 1.4 g ml-1. 

The apparent density 5 (g/cm3) is usually measured using mercury as a pycnometric fluid. Mercury does not wet most of the solids and, thus, does not penetrate pores until pressure is applied. Mercury is not the only choice highly dispersed powders can serve as a guest fluid with the same penetration properties as well [55], Reciprocal to S is the specific apparent volume of PS, which is equal to the sum of the volumes of the pores and solid phase (e.g., the total volume of a granule shown in Figure 9.17a), and is obviously related to the mass of a PS. Relation between true and apparent density and porosity was considered in Problem 4. 

Bulk density, or the apparent density, is the total mass per unit of total volume. It is not an intrinsic property of a material since it varies with the size distribution of the particles and their environment. The porosity of the solid and the material with which the pores, or voids, are filled also affect the bulk density. For a single nonporous particle, the true density equals the bulk density. 

The density-pressure relationship for powder compaction at room temperature typically increases from the apparent density at zero pressnre to values that approach the theoretical density at high pressures, as illustrated in Figure 7.16. A compact with 100% theoretical density would indicate that it contains no porosity. Soft powders are more easily densified than hard powders at a given pressnre, and irregularly shaped powders have lower densities than spherical powders in the low-pressure regime. 

Insulation materials contain more air and have an lower apparent density than ordinary refractory materials. In the case of insulation bricks the desired porosity is obtained by making use of additives which produce gases when heated (e.g. calcium carbonate), or of porous raw materials. In figure 11.3. 2 the effect of the appplication of insulation bricks is represented. 

Physical properties Density Specific gravity Pore structure True density as measured by helium displacement Apparent density Specification of the porosity or ultrafine structure of coals and nature of pore structure between macro, micro, and transitional pores... 

Thermal conductivity increases with increasing apparent density, volatile matter, ash, and mineral matter content. Due to the high porosity of coal, thermal conductivity is also strongly dependent on the nature of gas, vapor, or fluid in the pores, even for monolithic samples (van Krevelen, 1961). Moisture has a similar effect and increases the thermal conductivity of coal since its thermal conductivity value is approximately three times higher than that of dry coal (Speight, 1994, and references cited therein). However, the thermal diffusivity of coal is practically unaffected by moisture since the /Cp value is not essentially changed by moisture. 

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

In eq 1 the porosity e of the fluidized bed is the void volume of the fluidized bed (volume of interstices between grains, not including any pore volume in the interior of the particles) divided by the total bed volume, ps is the apparent density of the solid, and H is the height of the fluidized bed. 

The material used for the sintering of the support was polymethyl methacrylate (PPM) made by 0SW1 CIM . The sintering procedure was carried out for 3 h at 445 K in a brass form which was 1.0 m long and had an internal diameter of 9.0 mm. The sinters displayed an apparent density of 800 kg/m, a porosity of 0.300, and an average pore size of 26 gim. The bars were cut into 25 cm long specimens which were used as a membrane supports. 

The apparent density is used (a) in case of deagglomerated powders for a rough and simple grain-size estimation (b) in case of compacts (green density) or sintered specimens to determine the residual porosity. 

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