Fine-grained dust

The presence of rims of fine-grained material (e.g. Figure 7.4a) on chondrules in many chondrites provides useful constraints on when coagulation of fine-grained dust into larger aggregates occurred. Several models for the origin of these rims have been presented in the literature. Most models support formation of the rims by accretionary processes in the solar nebula (e.g. Metzler et al. 1992), but there are... 

Although chondrules have diverse chemical compositions, their sizes are narrowly sorted (Grossman et al. 1988 Brearley Jones 1996). Such a narrow size distribution may be explained by aerodynamic sorting provided by turbulence in the proto-solar disk, i.e. in the presence of disk gas. A correlation was found between the volume of the chondrule and the volume of the accretionary fine-grained dust rim on chondrules in the Allende meteorite (Paque Cuzzi 1997). These results could also be explained in terms of aerodynamic sorting in the gaseous disk. 

Fine dust 2 Fine-grained dust rims on dated chondrules... 

With the exception of these small amounts of meteoritic matter, the lunar soil is derived from igneous rocks disrupted by impacts and gradually reduced to fine-grained dust. On all landing sites, the soil is much more abundant than rocks or breccias. Except on steep slopes, the whole Moon is covered with a layer dust of at least 5 m thick. The rock samples brought back are separate fragments embedded in the soil once part of the underlying bedrock, they were excavated by the impact of meteorites. 

Martian crustal materials Ubiquitous, fine grained dust found on the surface of Mars believed to consist of silicates, iron oxide, carbonates and clays MAS-NMR Magic angle spinning-nuclear magnetic resonance... 

Wear-resistant linings may take the form of wearing plates or ceramic materials, but must not adversely affect the gas flow pattern in the cyclone. Fine-grained dust, especially if it has a high alkali content, is prone to cause caking and choking. 

Fine-grained dust from clay dryers and scmbbers also contains barite. Enrichment in... 

In addition, a significant amount of fine catalyst dust is produced in FCCUs as a result of the constant movement of the catalyst grains against each other. Much of this dust, consisting primarily of alumina and relatively small amounts of nickel, is carried with the carbon monoxide strewn to the carbon monoxide burner. 

Spent foundry sand is thought of as a beneficial substitute for fine sand for use in portland cement concrete. Prior to acceptance of inclusion, test standards applied on conventional fine sand shall be referred to as the standards for spent foundry sand to compare the physical properties of conventional sand and spent foundry sand. The most important parameters are particle size distribution, fineness modulus, dust content, density, organics content, deleterious materials content, and grain shape. Although no spent foundry sand satisfies all of the specifications, foundry sand can be blended with conventional sand to be incorporated into the concrete matrix. The replacing ratio normally starts at one-third. 

In recent years, a new source of information about stellar nucleosynthesis and the history of the elements between their ejection from stars and their incorporation into the solar system has become available. This source is the tiny dust grains that condensed from gas ejected from stars at the end of their lives and that survived unaltered to be incorporated into solar system materials. These presolar grains (Fig. 5.1) originated before the solar system formed and were part of the raw materials for the Sun, the planets, and other solar-system objects. They survived the collapse of the Sun s parent molecular cloud and the formation of the accretion disk and were incorporated essentially unchanged into the parent bodies of the chondritic meteorites. They are found in the fine-grained matrix of the least metamorphosed chondrites and in interplanetary dust particles (IDPs), materials that were not processed by high-temperature events in the solar system. 

The origin of Aeolian dust from Chinese desert to Japanese islands was studied with ESR of dust, mostly fine grains of quartz.132 Suspended particulate matter (SPM) collected by environmental protection agency was measured with ESR.133 Dust soot of automobiles was also measured to check the motor combustion rate. Adsorption of NO, Mn2+ and Gd3 on clay minerals, bentonite and se-piolite134 has been studied using paramagnetic ions as tracers for radioactive elements. And studies have been carried out on how divalent and trivalent cations diffuse and blocked by surrounding clay minerals, in the context of their leak from nuclear waste repository to the environment.135... 

Some very fine-grained atmospheric dust is capable of crossing oceans and accumulating on different continents. Dust samples from the Sahara Desert of North Africa (Mali) are known to contain at least 17 mg kg-1 of arsenic and may be responsible for contaminating cisterns as far west as the Caribbean and eastern USA ((Holmes and Miller, 2002 Shinn, 2001) Table 3.17). Dust in one cistern from St. John, US Virgin Islands, contained about 38 mg kg-1 of arsenic ((Holmes and Miller, 2002) Table 3.17). Arsenic from Sahara Desert dust may also accumulate in soils, sediments, water, and plants in Florida and surrounding areas (Holmes and Miller, 2002). 

In the Solar System the bulk elemental composition of the most volatile-rich Cl chondrites resembles closely that of the solar photosphere. Indeed, models that follow the condensation of a solar-composition hot gas reproduce many of the minerals and abundance trends observed in the Solar System. These are also consistent with some of the astronomical observations of dust in protoplanetary disks. Stardust grains also show approximately solar bulk composition in the measurable elements, albeit with some variations (Flynn et al 2006). Some IDPs -mainly the fine-grained, porous, and anhydrous particles - match the solar elemental... 

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