GB/T 16418-2008Particle system - Vocabulary (English PDF)

2.1 Vocabulary of particle

Particle: a discrete unit of any shape and of differing size, which may be solid, liquid or gaseous in state.

Agglomerate: a number of particles stuck to one another.

Powder: an aggregate of dry particles whose particle size is smaller than the value stated in the standard; also called powder material.

Micron particle, sub-micron particle and nanometer particle: solid particles whose particle size falls in the ranges stated in the standard.

Crystalline particle: the whole region in which the atoms are arranged periodically and which is enclosed by grain boundaries.

2.2.1 Particle size

Particle size: the measure of a particulate material.

Particle size distribution: the percentage of particles of each size class in a material. Frequency distribution: the proportion of the total that is made up by the amount of particles (in number, volume or mass) falling in a given size range; also called frequency or number-frequency distribution. Volume, mass, number, length, and surface or projected area distributions are the particle size distributions taken on the basis of particle volume, mass, number, length and surface or projected area respectively.

Median diameter: the particle size corresponding to the point at which the cumulative particle size distribution reaches fifty per cent, written D50. Mode diameter: the particle size corresponding to the highest point of the frequency distribution curve.

Equivalent diameter: the diameter of the sphere equivalent to the particle in a geometric or physical property. Equivalent projected area diameter: the diameter of the circle whose area equals the projected area of the particle. Equivalent surface diameter and equivalent volume diameter: the diameters of the spheres whose surface area, or volume, equals that of the particle. Equivalent Stokes diameter: the diameter of the homogeneous sphere whose free settling velocity in the same fluid under laminar flow equals that of the particle.

Feret's diameter: the distance between the parallel lines tangent to the sides of the projected outline of the particle. Martin's diameter: the length of the chord that divides the projected outline of the particle into two parts of equal area.

Particle hardness: the degree to which a particle resists deformation under a given external force.

2.2.2 Particle shape

Particle shape: the external form of a particle. Spherical particle and non-spherical particle: particles whose external form is, or is not, that of a sphere. Flaky particle: a particle whose external form is flake-like. Granular particle: a particle that approximates a sphere but is irregular in shape. Acicular particle and fibrous particle: particles whose external form is needle-like or fibre-like. Angular particle: a particle with sharp edges or roughly polyhedral in shape. Dendritic particle: a particle whose external form has a branched, tree-like shape.

Shape factor: the degree to which a particle departs from a sphere. Shape index: the external form of a particle expressed by various dimensionless combinations of its dimensions. Aspect ratio: the ratio of two representative diameters in the projected shape of the particle.

Bulkiness factor: the ratio of the projected area of the particle to the area of the smallest circumscribed rectangle. Volume filling factor: the ratio of the volume of the particle to the volume of its circumscribed rectangular solid. Circularity: the degree to which the projection of the particle approaches a circle. Degree of sphericity: the degree to which the particle approaches a sphere.

2.2.3 Pore

Porous solid: a solid having cavities, or having channels that are deeper than they are wide. Void: the gap between particles. Pore size: the width of a pore, for instance the diameter of a cylindrical pore or the distance between the two opposite walls of a slit pore.

Surface area: unless otherwise stated, the sum of the external and the gaseous surface areas. External surface area: the area including the protruding parts of the surface and all the cracks that are wider than they are deep. Internal surface area: the surface area of the walls of the internal pores. Specific surface area: the ratio of the surface area of the particles to their mass (or volume). Pore volume: the volume of the pores as measured by a specified method.

Open pore: a pore connected with the surface of the particle. Closed pore: a pore not connected with the surface of the particle. Blind pore: an open pore closed at the end and connected to the external surface by only one route. Ink bottle pore: an open pore with a narrow neck. Interconnected pore: a pore connected with one or more other pores. Through pore: a pore that passes completely through the sample. Macropore, mesopore and micropore: pores whose pore size lies above, between and below the limits stated in the standard.

Open porosity: the percentage of the total volume of a porous body that is made up by open pores and voids. Porosity: the ratio of the measurable pore and void volume in a given quantity of solid (the open pore volume plus the void volume) to the total volume it occupies. Intraparticle porosity: the ratio of the open pore volume inside the particles to the total volume occupied by the solid. Interparticle porosity: the ratio of the void volume between the particles to the apparent volume of the powder.

Adsorption: the enrichment of an adsorbed gas on the external surface, and on the accessible internal surface, of a solid material. Physisorption: an adsorption process in which the bond between adsorbate and adsorbent is not chemical; the process is reversible, non-specific and may be multilayer, and desorption occurs as the pressure falls or the temperature rises. Chemisorption: an adsorption process in which the bond between adsorbate and adsorbent is a chemical bond; the process is irreversible and specific, can only be monolayer, and a higher temperature has to be supplied to break the chemical bond before desorption occurs.

Adsorbate, adsorbent and adsorptive: respectively the substance that is adsorbed, the solid material on which adsorption takes place, and the gas or vapour that can be adsorbed. Adsorbed amount, volume adsorbed, adsorption isotherm, equilibrium adsorption pressure, monolayer adsorption amount, monolayer adsorption capacity, relative pressure and saturation vapour pressure complete the group.

2.2.4 Density

True density: the mass of the particles divided by the volume of the particles not including the closed and open pores. Skeletal density: the mass of the particles divided by the total volume of the sample including the closed pores but not the open pore volume. Effective density: the mass of the particles divided by the total volume of the sample including the closed pores and the pore volume that a specified method finds inaccessible.

Apparent volume: the total volume of the solid material of the particles including the open pores, the closed pores and the gaps. Apparent specific volume: the ratio of the volume occupied by the particles to their mass. Apparent density: the density obtained by dividing the mass of the particles by the apparent volume.

Bulk density: the mass of the particles, filled into a container of known volume by a natural method, divided by the capacity of that container. Tap density: the mass of the particles in a container, filled by a given method and then vibrated according to a given regime, divided by the apparent volume of the particles after vibration.

2.2.5 Other properties

Flowability: the property of a powder to change position under an external force. Flow factor: an important parameter characterizing the flowability of a powder. Carr flow index: a parameter that takes the various factors affecting the flowability of a powder together and is used to judge it.

Angle of repose: the maximum angle formed with the horizontal plane by the free surface of a heap of powder in a static state of equilibrium; also called the static angle or the angle of rest. Angle of internal friction: a parameter expressing the frictional characteristics between the layers of particles. Angle of wall friction: a parameter expressing the frictional characteristics with the container. Angle of slide: the angle between the horizontal plane and the plane on which stationary particles begin to slide under gravity. Contact angle: the triple interface formed by a liquid on a solid material.

Surface tension: the force that, per unit length perpendicular through the surface of a liquid (or solid) body, contracts the surface in the direction tangential to the liquid (or solid) surface. Permeability: the degree of ease with which a powder bed allows a fluid to pass through it.

Compression ratio: the ratio of the volume occupied by a powder in the loosely packed state to that occupied in the closely packed state. Compressibility: the ability of a powder to be compressed, expressed by the compression ratio obtained under given test conditions. Friability: the degree to which particles break up and become smaller under conditions of little external force during storage and handling. Grindability: the degree of ease with which particles can be ground up by mechanical means under given conditions.

2.3 Analysis method

Diffraction of light method: an analysis method that obtains the particle size and the distribution by measuring the diffracted light intensity distribution of a dispersed particle system; also called the light scattering method. Photon correlation spectroscopy (PCS): the measurement of the change with time of the scattered light intensity at a given angle caused by the Brownian motion of the particles in a liquid, the particle size and the distribution being obtained by correlation function analysis.

Microscopy-image analysis: an analysis method that measures the morphology and the particle size distribution of a powder using microscope imaging combined with an image analysis system; it includes static and dynamic image methods. X-ray diffractometry line broadening method (XRD-LB): an analysis method that determines the crystallite size and the degree of lattice distortion from the broadening of the diffraction lines caused by the refinement of the crystallites and by lattice distortion. Small angle X-ray scattering (SAXS): the particle size distribution obtained by measuring the scattered intensity angle by angle when X-rays passing through ultrafine particles are scattered through small angles by the electrons in them.

Resistive of light method: the particle size and number obtained from the weakening of the light received by the photoelectric receiver when a particle passing through the detection zone blocks part of the light; also called the light obscuration method. Light extinction: the particle size and distribution obtained from the weakened light distribution, according to light scattering theory, when a particle passing through the detection zone absorbs and scatters part of the incident light.

Coulter method: the particle size and number obtained by measuring in turn the change in resistance caused by each single particle as it passes through the resistance sensing zone and increases the resistance there; also called the electrical resistance method. Ultrasonic method: the particle size and distribution obtained from the sound velocity spectrum or the attenuation spectrum of an ultrasonic wave passing through a particle system dispersed in a medium.

Gas sorption: a method that obtains the adsorption-desorption isotherm at constant temperature by measuring the saturated adsorption amount of the adsorbed gas on the sample at a series of partial pressures, from which the specific surface area and the pore size distribution of the sample are obtained. BET theories: the multi-molecular-layer adsorption theory of porous substances, built on the Langmuir equation and correcting it, and the most widely used theory for calculating specific surface area. Mercury porosimetry: a method that makes use of the non-wetting property of mercury on a solid surface, pressing mercury into the pores of a porous body and obtaining the pore size distribution and the related characteristics of the porous material from the inverse relationship between the total pressure of the mercury forced into the pores and the pore size.

2.4 Application of particle system

Classification: the process of separating particles into different particle size classes. Static electricity classification: a method of classifying particles by means of an electric field, the particles having been given a charge. Elutriation: a classification process brought about by the motion associated with a rising fluid. Sedimentation: the process in which solid particles suspended in a fluid medium fall under the action of an external force; it includes gravity sedimentation and centrifugal sedimentation. Filtering: the process of classifying particles by passing an aerosol or a suspension through filter materials of different pore size. Hydrodynamic chromatography: the separation of particles of different size along a chromatographic column packed with spherical supports, making use of the relationship between migration rate and particle size.

Dispersion: the process of distributing a powder as uniformly as possible, and as far as possible as single particles, in another medium. Dispersant (dispersing agent): an additive that prevents particles from agglomerating and disperses them into single particles. Dispersion medium: the continuous phase in a dispersed system, which may be a gas, a liquid or a solid. Surface treatment: the collective name for the processes of surface shaping, surface modification and surface coating.

Mixing: the process of making a particle system of differing chemical composition or differing particle size into a more uniform system. Mixing index: the ratio of the standard deviation to the mean value obtained when the degree of mixing uniformity is tested.

Fluidization: the operation in which solid particles are held up by a fluid so that the whole system shows some of the characteristics of a fluid. Particulate fluidization: the smoother kind of fluidization; liquid-solid fluidization is generally particulate. Aggregative fluidization: the more violent kind of fluidization; gas-solid fluidization is generally aggregative.

Drying: the operation of removing the liquid contained in a solid by evaporation. Dedusting: a method of reducing the dust content of the working space and the pollution of the environment.

Pressing: the process of compressing a powder under pressure in a die. Cold pressing, warm pressing and hot pressing: pressing carried out at or below room temperature, above room temperature but below the sintering temperature, and simultaneously with sintering. Compact: a dense block formed by compressing a powder in a die. Green compact: a compact prepared for sintering or for other treatment. Sintering: the process of heating loose powder or a compact so that the particles bond together. Sintered compact: a compact that has been sintered. Green density and pressed density: the apparent density of a green compact that has not been sintered, and the apparent density of a compact obtained by pressing a powder.

2.5 Sieving

As specified in GB/T 5329.

2.6 Preparation

Natural powder: a powder formed naturally. Milled powder: a powder obtained by deformation or mixing in a mill. Atomized powder: a powder obtained by atomizing a molten metal or other substance under given conditions and then letting it solidify. Fumed powder: a powder obtained from fumes. Calcined powder: a powder produced or modified by calcination. Carbonyl powder: a metal powder obtained by the thermal decomposition of a metal carbonyl compound. Electrolytic powder: a powder obtained by electrolytic deposition, or by crushing the deposit. Hydrogen reduced powder: a powder obtained by the hydrogen reduction of a metal oxide or other compound. Precipitated powder: a powder obtained by chemical precipitation.

2.7 Others

Bubble: made up of discrete gas dispersed in a solid or a liquid. Droplet: made up of discrete liquid dispersed in a gas or another fluid. Foam: a system made up of bubbles dispersed in a liquid.

Dust: made up of particulate matter in air whose particle size is smaller than the value stated in the standard. Aerosol: a stable system made up of solid and/or liquid particles suspended in a gaseous carrier, the particle size lying in the range stated in the standard. Colloid: a stable system made up of nanometer particles uniformly dispersed in a liquid.

Fog: minute droplets suspended in air. Smoke: minute solid particles suspended in air whose particle size is smaller than the value stated in the standard. Haze: solid or mixed solid-liquid particles suspended in air whose particle size is smaller than the value stated in the standard.