Agglomerate count

The instrument has been evaluated by Luster, Whitman, and Fauth (Ref 20). They selected atomized Al, AP and NGu as materials for study that would be representative of proplnt ingredients. They found that only 2000 particles could be counted in 2 hours, a time arbitrarily chosen as feasible for control work. This number is not considered sufficient, as 18,000 particles are required for a 95% confidence level. Statistical analysis of results obtained for AP was impossible because of discrepancies In the data resulting from crystal growth and particle agglomeration. The sample of NGu could not be handled by the instrument because it consisted of a mixt of needles and chunky particles. They concluded that for dimensionally stable materials such as Al or carborundum, excellent agreement was found with other methods such as the Micromerograph or visual microscopic count. But because of the properties peculiar to AP and NGu, the Flying Spot Particle Resolver was not believed suitable for process control of these materials... 

Particle characteristics Size, size distribution, shape, mechanical properties, surface chemistry, dispersion stability, concentration, agglomeration, and oversize particle count... 

An alternative method to filtration has been considered in order to reduce the large particles and agglomerates. Li and co-workers [41] investigated a novel slurry conditioner to reduce the oversized particle count present in CMP slurries. This study focused on the correlation between the oversized particle counts in STI CMP slurries and their influence on the wafers after polishing. A representative oversized particle count reduction after the treatment with the conditioner is shown in Fig. 13.30. 

Semi-automatic aids to counting and sizing have been developed to speed up analyses and reduce the tedium of wholly manual methods. The advantage of these aids over fully automatic systems was that human judgment was retained. The operator could select or reject particles, separate out agglomerates, and discriminate over the choice of fields of view. Many such aids were developed and these differed widely over the degree of sophistication, price, ease of use, mode and speed of operation they have however been supplanted by quantitative image analyzers. 

Various dry powder attributes are assessed at release and on stability. These include physical characteristics such as powder appearance, content uniformity, delivered dose uniformity, and particle size distribution. Chemical attributes that may be assessed include drug content, purity, and identity as well as the water content of a powder. Dry powders may also undergo microscopic evaluation for foreign particulate matter, unusual agglomeration, and particle size. Microbial limits also should be examined, including the total aerobic, yeast, and mold counts. The presence of specific pathogens should be ruled out. The dry powders also may be dissolved to test for pH level. In addition, certain compendial requirements for content and delivered-dose uniformity should also be measured. 

Another problem in PSD measurement is caused by particle agglomerates. A single large agglomerate may contain multiple small crystals. But this agglomerate will be counted as one large particle if it is not dispersed during measurement. Therefore, it is always... 

During particle size analysis, in addition to screening, sifting, and counting, sedimentation techniques are often used which produce unequivocal results only if the individual particles can move without influencing each other. For that reason, very dilute suspensions are used. Nevertheless, it is possible that agglomerates form or already... 

Wash the centrifuge tube with 5-10 drops of distilled water and transfer the washings and the residual precipitate to the counting tray. Spread the slurry evenly over the tray within the cellulose lacquer ring and break up agglomerations of solid matter with additional drops of water where necessary. 

After 42 m of exposure at PI, morphology of MS is layered and chunky as per Fig. 3.36a. For WS it is an agglomeration of smaller oxides and shows relief effect with very fine network of cracks on the oxide film as per Fig. 3.36b. Line scans as shown in Figs. 3.40a and b for WS and Figs. 3.39a and b for MS show identical O2 count. SEM and EDX line scan, thus, justifies the identical corrosion rate of both MS and WS as reported in Table 2.8. 

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