Particle size studies

Table IV. Test Conditions for Particle Size Study...

For each of the three particles sizes studied, the deposition efficiency in the trachea was much greater than predicted if uniform deposition is assumed. In each data set the ratio at the lower flow rate exceeded that at a higher flow. If the increase results from turbulence introduced by the larynx it might be expected to be more effective at the higher flow rate. The discrepency may result from the jet formed downstream of the larynx. The center line velocity substantially exceeds the mean velocity of the air stream and secondary circulation patterns are set up near the wall which can act as dead zones (Ultman, 1 985) ... 

Table 4.11 Particle size study of aqueous emulsions...

Moss, W.D., Hyatt, E.C. Schulte, H.F. (1961) Particle size studies on plutonium aerosols. Health Physics, 5, 212-18. 

Thus, the mean particle-sizes studied ranged from 180 to less than 5 ju. For most of the magnetites it was found that the Fe3C>4 content did not change much with particle-size. However, definite relationships were found to exist between permeability and particle-size for various field strengths At low field strengths, there was a marked decrease in... 

The heat of wetting has been studied for many materials, with different liquids. Not all the data are accurate, and few even attempt to estimate the relation between the heat generated and particle-size. Studies made in the field of soil physics have provided many interesting results and some of the more important of these are presented here. Table 44... 

Other researchers " " have also reported NIR particle size studies. 

Uchida T, Goto S. Oral delivery of poly(lactide-co-glycolide) microspheres containing ovalbumin as vaccine formulation Particle size study. Biol Pharm Bull 1994 17 1272-1276. 

Tang et al. studied these effects using DFT (with a complementaiy in situ STM study) [95]. They found similar trends for the Pt nanoparticles studied compared to the bulk in relation to metal/hydroxide/oxide stability but found a very strong dependence on particle size. For the smallest particle size studied (radius of 0.25 nm), at low pH, there is a direct dissolution pathway and hydroxides and oxides are not predicted to form prior to dissolution. Consequently, it can be surmised that under fuel cell conditions, there is a crossover in particle size below which the particles do not develop a passivating oxide layer and instead are subject to direct dissolution, thus decreasing their aheady compromised stability. This study again only looks at surface occupation of OH and O without surface/particle reconstruction but provides very useful information for the stability of Pt nanoparticles and the conditions that lead to oxide formation at the nanoscale. In addition, it shows how DFT can not only give information on phase stability but also point to corrosion mechanisms under different conditions. 

Note that the numerical solutions of the exact transport equation, Eq. (160), agree well with the experimental data for the entire range of particle sizes studied. As can be seen in Fig. 46, the position and the depth of the minimum depends strongly on the flow intensity (Re number). Thus, for Re = 30, the particle flux becomes practically independent on particle size larger than... 

Another example of a DMC-catalyzed esterification reaction is the esterification of free fatty acids with glycerol [32]. This reaction again used Zn-Fe(II)-DMC as a catalyst yet the activity of the material could be tuned by varying the synthesis temperature. As such, DMCs with different acidities (as evidenced by NHj-TPD), crystallite sizes (calculated from the Debye-Scherrer equation), particle sizes (studied with scanning electron microscopy (SEM)), and BET (Brunauer, Emmett and Teller) specific surface areas were obtained. The highest catalytic conversions were observed for the catalysts synthesized at elevated temperatures these materials featured both the highest specific surface area and the largest number of acid sites. 

---