Wide size range

Pressure Volume intruded Pore radius Mean pore I US Specific surface Relative volume AV Relative surface AS 

---

There are many techniques available for measuring the particle-size distribution of powders. The wide size range covered, from nanometers to millimeters, cannot be analyzed using a single measurement principle. Added to this are the usual constraints of capital costs versus running costs, speed of operation, degree of skill required, and, most important, the end-use requirement. 

Thermoformed (3-D shape) plastics provide a great variety and quantities of marketable products, in a wide size range from millions of drinking cups or containers (each... 

A combination of graded calcium carbonate particle sizes, a nonionic polysaccharide of the scleroglucan type, and a modified starch, has been claimed for use as a fluid loss formulations [915]. It is important that the calcium carbonate particles are distributed across a wide size range to prevent filtration... 

Hierarchical structures with pore—solid features that cover a wide size range within one structure, as seen in Figure 15, are achieved by carefully combin-... 

The experimental results reported in this paper demonstrate the ability of a flat-bottom hydrocyclone to separate the coarse fraction of ammonium sulfate crystals from a slurry which contains crystals of a wide size range. It appears that the grade efficiency curve, which predicts the probability of a particle reporting to the underflow of the cyclone as a function of size, can be adjusted by a change in the underflow diameter of the hydrocyclone. These two observations lead to the suggestion to use hydrocyclone separation to reduce the crystal size distribution which is produced in crystallisers, whilst using a variable underflow diameter as an additional input for process control. 

Although the results were not definitive, it is clear that substantial amounts of NG passed through both the 1.2- and 0.8-pm filters, although the initial filter retained the bulk in each test. (There were no membrane filters with a pore size less than 0.45 pm in the laboratory at the time of the test. It would have been interesting to repeat the experiment incorporating the smaller pore size filters, such as 0.2 pm.) It is suspected that NG is present as both vapor and particulate matter, the particulate matter having a wide size range. 

Acoustic methods offer several advantages when compared to other comparable techniques (1) applicable to concentrated suspensions (2) less sensitive to particulate contamination (3) better suited to polydisperse suspensions (4) applicable to a wide size range (5) well suited to automated potentiometric titrations and analysis... 

The standard deviation and geometric standard deviation are statistical measures of spread. The former is more commonly used with powders having a narrow size range and is the difference between the 50% and the (50 I6)% sizes. The latter is more commonly used with powders having a wide size range and is the ratio of the 50% and the non-fractional (50 16)%sizes. The standard deviation is defined as ... 

For narrow size distributions it is usually preferable to use an arithmetic size progression (as in Table 2.8) and present the frequency data in the manner given in column 5. For wide size ranges a geometric size... 

Number distributions, for powders having a wide size range, should never be converted into volume distributions unless a statistically acceptable number of particles in the largest size category have been counted. For a microscope count, the correct procedure for carrying out a size distribution by weight should be followed. 

Muta and Watanabe [13] examined samples extracted during Andreasen analyses and detected particles of 1 pm, for example, when Stokes equation predicted a maximum size of 0.89 pm. They concluded that gravitational Andreasen sedimentation analysis was unsuitable for powders of wide size range containing sub-micron particles. They surmised that this might be due to re-distribution of fine particles caused by disturbance to the suspension in the course of long-term sedimentation. 

Davies and Kaye [60] used a Cahn sedimentation balance to investigate cluster formation and found that, for a powder having a narrow size range, cluster formation was not eliminated at volume concentrations as low as 0.47% for a powder having a wide size range it was not important at volume concentrations as high as 0.414%. 

Multiple aperture method for powders having a wide size range (a) General... 

The most common method is direct photography [202-205]. The method is simple, easy and accurate and covers a wide size range, controlled by microscope magnification, from a lower limit of 1 pm. The technique is only suitable for low concentration systems, particularly in the case of high opacity continuous phases. The procedure requires many pictures and lengthy analysis times. Direct image analysis of the data has met with limited success. 

ASTM F751 -83 (1997), Measuring particle size of wide-size range dry toners, 450... 

Turbidity has been widely used for determining the particle size distribution (PSD) of particles in suspension, since it is experimentally simple, can be used over a wide size range and does not disturb the system under investigation. It is also fast, reproducible and inexpensive. 

Cilas 1064 has high resolution, giving information over the size range 0.04 to 500 pm for suspensions and 0.3 to 500 pm for dry powders in one shot, due to a double sequenced laser system (two lasers at different incident angles) and 64 separate silicon detectors to give 100 size channels of data. The benefits of such a system include coverage of a wide size range with a small optical bench structure. The diffraction pattern is compared to a known powder and the size distribution calculated. 

Malvern Mastersizer is a fixed configuration model to lower cost. A range of small volume accessories are available along with the standard Mastersizer E tank that is suitable for volumes of 1 liter. The wide size range of 0.1 pm to 600 pm makes it ideal for routine analysis and quality control. 

Malvern Mastersizer S uses Mie theory to cover the size range 0.05 to 900 pm using a single lens, and up to 3500 pm with an extended range system. Scattering angles from 0.01 ° to 150° are detected in order to cover this wide size range. The system handles measurements of particles, droplets or gas bubbles. 

---