BS ISO 15901-2-2022 pdf free download.Pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption Part 2: Analysis of nanopores by gas adsorption.
This document describes a method for the evaluation of porosity and pore size distribution by physical adsorption (or physisorption). The method is limited to the determination of the quantity of a gas adsorbed per unit mass of sample as a function of pressure at a controlled, constant temperature [1]-[9] . Commonly used adsorptive gases for physical adsorption characterization include nitrogen, argon, krypton at the temperatures of liquid nitrogen and argon (77 K and 87 K respectively) as well as CO 2 (at 273 K). Traditionally, nitrogen and argon adsorption at 77 K and 87 K, respectively, allows one to assess pores in the approximate range of widths 0,45 nm to 50 nm, although improvements in temperature control and pressure measurement allow larger pore widths to be evaluated. CO 2 adsorption at 273 K – 293 K can be applied for the microporous carbon materials exhibiting ultramicropores. Krypton adsorption at 77 K and 87 K is used to determine the surface area or porosity of materials with small surface area or for the analysis of thin porous films.
The method described is suitable for a wide range of porous materials. This document focuses on the determination of pore size distribution from as low as 0,4 nm up to approximately 100 nm. The determination of surface area is described in ISO 9277. The procedures which have been devised for the determination of the amount of gas adsorbed may be divided into two groups:
— those which depend on the measurement of the amount of gas removed from the gas phase, i.e. manometric (volumetric) methods;
— those which involve the measurement of the uptake of the gas by the adsorbent (i.e. direct determination of increase in mass by gravimetric methods).
In practice, static or dynamic techniques can be used to determine the amount of gas adsorbed. However, the static manometric method is generally considered the most suitable technique for undertaking physisorption measurements with nitrogen, argon and krypton at cryogenic temperatures (i.e. 77 K and 87 K, the boiling temperature of nitrogen and argon, respectively) with the goal of obtaining pore volume and pore size information. This document focuses only on the application of the manometric method.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling ISO 8213, Chemical products for industrial use — Sampling techniques — Solid chemical products in the form of particles varying from powders to coarse lumps
ISO 9277, Determination of the specific surface area of solids by gas adsorption — BET method
ISO 14488, Particulate materials — Sampling and sample splitting for the determination of particulate properties
3? Terms? and? definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
adsorbate
adsorbed gas
3.2
adsorption
enrichment of the adsorptive at the external and accessible internal surfaces of a solid
3.3
adsorptive
gas or vapour to be adsorbed
3.4
adsorbent
solid material on which adsorption occurs
3.5
adsorption isotherm
relationship between the amount of gas adsorbed and the equilibrium pressure of the gas at constant
temperature
3.6
adsorbed amount
amount of gas adsorbed at a given pressure, p, and temperature, T
3.7
equilibrium adsorption pressure
pressure of the adsorptive in equilibrium with the adsorbate
3.8
monolayer amount
amount of the adsorbate that forms a monomolecular layer over the surface of the adsorbent
3.9
monolayer capacity
volumetric equivalent of monolayer amount expressed as gas at standard conditions of temperature and pressure (STP)
3.10
nanopore
pore with width of 100 nm or less
3.11
macropore
pore with width greater than about 50 nm
3.12
mesopore
pore with width between approximately 2 nm and 50 nm
3.13
micropore
pore with width of about 2 nm or less
3.14
supermicropore
pore with width between approximately 0,7 nm and 2 nm
3.15
ultramicropore
pore with width of approximately < 0,7 nm
3.16
physisorption
weak bonding of the adsorbate, reversible by small changes in pressure or temperature
3.17
pore size
pore width, i.e. diameter of cylindrical pore or distance between opposite walls of slit
3.18
pore volume
volume of pores as determined by stated method
3.19
relative pressure
ratio of the equilibrium adsorption pressure, p, to the saturation vapour pressure, p 0 , at analysis temperature
3.20
saturation vapour pressure
vapour pressure of the bulk liquefied adsorptive at the temperature of adsorption
3.21
volume adsorbed
volumetric equivalent of the amount adsorbed, expressed as gas at standard conditions of temperature and pressure (STP), or expressed as the adsorbed liquid volume of the adsorbate
4 Symbols
For the purposes of this document, the following symbols apply, together with their units. All specific dimensions are related to sample mass, in grams.BS ISO 15901-2 pdf download.