Calcium carbonate aggregate

Figure 8 Conceptual diagram of a simplified carbonate pump . Some marine organisms form calcareous skeletal material, a portion of which sinks as calcium carbonate aggregates. These aggregates are preserved in shallow ocean sediments or dissolve at greater depths (3000-5000 m), thus increasing DIG concentrations in the deep ocean. The calcium and bicarbonate are returned to the surface ocean through upwelling.

Schilde C, Hanisch C, Naumann D, Beierle T, Kwade A (2013) A novel way to vary the structure of precipitated silica and calcium carbonate aggregates in a wide range by using grinding media during the precipitation process. Chem Eng Sci 94 127-137... 

The simplest, lime-based mortars came into common use in Europe in the first century BC (Stanley 1979). These were made by first calcining limestone at temperatures high enough to produce lime (CaO), and then hydrating it to form portlandite (Ca(OH)2) which would later have become carbonated, i.e. converted to calcium carbonate. Aggregates (mostly of quartz) in these mortars have often been found to be etched and pitted, presumably by the alkaline conditions established by hydration, although it... 

The geometry and surface chemistry of the dendrimer assemblies can be varied through the addition of surfactants. These dendrimer/surfactant aggregates can be tuned to template the formation of the different phases of calcium carbonate [40]. In combination with hexadecyltrimethylammonium bromide (CTAB), small spherical aggregates were formed that induce the formation of vaterite. Over a period of five days, the vaterite was transformed into calcite. The use of the negatively charged surfactant, sodium dodecylsulfonate (SDS), result-... 

We developed another dispersant presenting properties for a special application. In some cases when an ultra fine calcium carbonate slurry is spray dried, a re-agglomeration of the powder often occurs, due to high water adsorption. This powder aggregation is detrimental to the quality of the final product. 

To conclude this brief digression into history, we may point out one more important aspect the high efficiency of the combined shear in molding of filled thermoplastics. One of the first works in this field was 31) which described experiments carried out with polypropylene filled with a disperse aggregate calcium carbonate (chalk) and a short-fiber material-asbestos. 

A complete summary of the work done on the perplexing problem of the origin of particulate material in the sea can be found in Riley s review (69). His review of the work on the bubbling makes it clear that mechanisms other than bubbling can produce particulate material. For example, particles appear to develop more or less spontaneously by aggregation of smaller entities (70) and by the adsorption of dissolved organic material onto calcium carbonate particles (71). 

For smaller I/Iq values, i.e., when rate cf calcareous formation is larger, the d values increase very rapidly. Intuitively, one may suppose that this corresponds to overlapping of calcium carbonate crystals. The dimension d would then give the average distance between areas that remain active, and, therefore, the size o/CaCOa aggregates. However, the corresponding theory is not yet available, and the above interpretation is speculative for the variations of d in the range 0 < Z/Iq < 0.5. 

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