Sieving, particle size

Electron microscopy, with its high spatial resolution, plays an important role in the physical characterization of these catalysts. Scanning electron microscopy (SEM) is used to characterize the molecular sieve particle sizes and morphologies as a function of preparation conditions. Transmission electron microscopy (TEM) is used to follow the changes in the microstructure of the iron silicates caused by different growth conditions and subsequent thermal and hydrothermal treatments. 

D-4513 Particle Size Distribution of Catalytic Material by Sieving Particle size distribution of catalyst particles (20 to 420jim) as measured weight of sample passing through calibrated sieves ... 

Solid dispersion particles made by spray-drying dis-ulfiram 1 1 or 1 2 (w/w) with PVP and instilled in the rabbit eye were found to have improved concentrations in the aqueous humor compared to 1 1 solid dispersions made by the evaporation method. In both cases, drug particles were passed through a 75 pm sieve. Particle size of the spray-dried particles had a D o of 3.3 0.04 pm, while those prepared by evaporation had a Dso of 34.3 18pm. ° ... 

The starting material used for the preparation of CMS was coconut shell. It was crushed and sieved (particle size 2-2.8 mm), and washed with deionized water (Series CW) or diluted sulphuric acid (Series CS). After drying in air at room temperature, the material was carbonised under a nitrogen flow (80 cm min ) at 850°C for 2 h, with a heating rate of 2°Cmin-i. The mean yield obtained from this process was 30.1 0.2 %. Activation was carried out with carbon dioxide (120 cm min ) at 750°C during 2-72 h, with a heating rate of 5°Cmin. ... 

Catalyst on sieve particle size Pd>Pt,Ni>Cu Increa qg 3ridd for increased size Increasing M for decreasing partide size Interdeterminate... 

Equations (31) and (32) can be used to analyze impedance spectra without knowledge of structural electrode parameters (thickness, density, etc). However, we need this information in order to transform the ohmic parameters obtained by a fit into specific electrochemical parameters. In particular, this information can be used to calculate the effective surface area of the particles. Particles used in practical batteries can usually be treated either as thin plates (Levi and Aurbach [1997]) or as pseudospherical in shape (Barsoukov [2003]), and have a narrow size distribution due to sieving. Particle size values are provided by material manufacturers. The number of particles in a given volume can be estimated from the ratio of their crystallographic density of particles, Op, to the density of the composite-electrode film, a. This allows one to calculate the electrochemically active surface area for a composite electrode for thin-plate particles as 5 = xAdalUOp] and for spherical particles as 5 = 3xAdal[rCp. Here x is the fraction of active material in the composite A is the geometric area of the electrode d is the thickness of the composite electrode <7 is the density of the composite electrode Op is the true density of particles and I and r are the thickness of the plate and radius of spherical particles, respectively. 

Ore samples are analyzed for %w/w Ni. A jaw crusher is used to break the original ore sample into smaller pieces that are then sieved into 5 size fractions. A portion of each fraction is reduced in size using a disk mill and samples taken for analysis by coning and quartering. The effect of particle size on the determination of %w/w Ni is evaluated. 

Solid samples are separated by particle size using one or more sieves. By selecting several sieves of different mesh size, particulates with a narrow size range can be isolated from the solid matrix. Sieves are available in a variety of mesh sizes, ranging from approximately 25 mm to 40 )j,m. 

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific apphcations (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumna) Carbon, activated carbon Ion exchange Molecular sieves and Silicon compounds, synthetic inorganic silicates). 

Particle Size. Wet sieve analyses are commonly used in the 20 )J.m (using microsieves) to 150 )J.m size range. Sizes in the 1—10 )J.m range are analyzed by light-transmission Hquid-phase sedimentation, laser beam diffraction, or potentiometric variation methods. Electron microscopy is the only rehable procedure for characterizing submicrometer particles. Scanning electron microscopy is useful for characterizing particle shape, and the relation of particle shape to slurry stabiUty. 

Screening. A 100-g sample of mica is usually used for this test, plus a rack of six Tyler sieves and a pan. The stack of sieves containing the sample is rotated, and after screening, the mica remaining on each screen is weighed and the percentage retained is calculated. A combination of wet and dry screening may also be used to determine particle size distribution of fine mica (<0.147 mm ( — 100 mesh)). 

Particle-SiZe Distribution. Particle-size specifications for sugar are not usually a part of the legislated standards, but they are of concern to commercial users and suppHers and are often specified in contracts. Grain-size distribution is determined by using a series of sieves, either hand-sieved or machine-sieved (13). 

In the United States, a number of physical tests are performed on siUcon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettabiUty), friabiUty, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated abrasives and powders. 

The mass transport influence is easy to diagnose experimentally. One measures the rate at various values of the Thiele modulus the modulus is easily changed by variation of R, the particle size. Cmshing and sieving the particles provide catalyst samples for the experiments. If the rate is independent of the particle size, the effectiveness factor is unity for all of them. If the rate is inversely proportional to particle size, the effectiveness factor is less than unity and

experimental points allow triangulation on the curve of Figure 10 and estimation of Tj and ( ). It is also possible to estimate the effective diffusion coefficient and thereby to estimate Tj and ( ) from a single measurement of the rate (48). 

Product particle sizes vary from standard size of 6/14 mesh—U.S. Std. Sieves to mini-size granules of 10/16 mesh—U.S. Std. Sieves for small particle blends, to micro-size granules of 14/35-U.S. Std. Sieves for use on golf course tees and greens. Approximate mm corresponding to mesh sizes are 6 mesh/3.36 mm 10 mesh /2 mm 35 mesh/0.5 mm. 

Particle-Size Distribution This is defined as the relative percentage by weight of grains of each of the different size fractious represented in the sample. It is one of the most important factors in evaluating a screening operation and is best determined by a complete size analysis using testing sieves. 

Unit matrix in mill equations X Particle size or sieve size cm in... 

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