Coatings particle size

If the adhesion mechanism between particles with different size is mainly subject to this attraction due to the electrostatic interaction, it is deduced that the increase in the ratio of core particle size to the coating particle size is advantageous for the formation of the monolayer particle coated powder. 

Magnesium granules, coated particle size not less than 149 microns 2950... 

Type Name Polymer constituting the coating Particle size (p)... 

The ceramic multi-layer coating effectively confines fission products at 1400°C for a long period and at 1600°C in the course of a few hours. At such temperatures the removal of residual heat can be performed by natural convection, conduction and radiation on a passive basis. Given the characteristic coated particle size (the diameter of 2-4 mm), the heat from coated particle fuel is transferred to the coolant with a delay of only 0.1 s. Therefore, the core of a reactor with boiling water coolant that directly cools such coated fuel particles would provide a very rapid self-compensation of practically any positive reactivity if it is introduced not faster than in 0.1 s. 

A pigaent with unique particle size distribution. Its easy dispersion characteristics have denonstrated its unusual merit as a mix-in type of pigment for a wide variety of applications such as carpet backing, roof compounds, spackles, and coatings. Particle Size Range (micrometers) Up to 44 Mean Particle Size (micrometers) 11.0 Oil Absorption (rub-out) 7-9... 

Liquid Surface Coating Particle Size Range (pm) Spreading Factor... 

Insoluble Ammonium Polyphosphate. When ammonium phosphates are heated ia the presence of urea (qv), or by themselves under ammonia pressure, relatively water-iasoluble ammonium polyphosphate [68333-79-9] is produced (49). There are several crystal forms and the commercial products, avaUable from Monsanto, Albright WUson, or Hoechst-Celanese, differ ia molecular weight, particle size, solubUity, and surface coating. Insoluble ammonium polyphosphate consists of long chains of repeating 0P(0)(0NH units. 

In order to make an efficient Y202 Eu ", it is necessary to start with weU-purifted yttrium and europium oxides or a weU-purifted coprecipitated oxide. Very small amounts of impurity ions, particularly other rare-earth ions, decrease the efficiency of this phosphor. Ce " is one of the most troublesome ions because it competes for the uv absorption and should be present at no more than about one part per million. Once purified, if not already coprecipitated, the oxides are dissolved in hydrochloric or nitric acid and then precipitated with oxaflc acid. This precipitate is then calcined, and fired at around 800°C to decompose the oxalate and form the oxide. EinaHy the oxide is fired usually in air at temperatures of 1500—1550°C in order to produce a good crystal stmcture and an efficient phosphor. This phosphor does not need to be further processed but may be milled for particle size control and/or screened to remove agglomerates which later show up as dark specks in the coating. 

The sol—gel technique has been used mosdy to prepare alumina membranes. Figure 18 shows a cross section of a composite alumina membrane made by sHp coating successive sols with different particle sizes onto a porous ceramic support. SiUca or titanium membranes could also be made by the same principles. Unsupported titanium dioxide membranes with pore sizes of 5 nm or less have been made by the sol—gel process (57). 

The average particle size of coating-grade titanium dioxide is ca 0.3 p.m. Because this size is optimum for maximum hiding power and because of its... 

Phenolic Dispersions. These systems are predominantly resin-in-water systems in which the resin exists as discrete particles. Particle size ranges from 0.1 to 2 p.m for stable dispersions and up to 100 p.m for dispersions requiring constant agitation. Some of the earliest nonaqueous dispersions were developed for coatings appHcations. These systems consist of an oil-modified phenoHc resin complexed with a metal oxide and a weak solvent. 

To achieve the maximum coating opacity the opacifter particle size should be between 0.2 and 0.3 ]lni. A good opacifter should not be soluble in the vitreous system, should have a refractive index substantially different from the refractive index of the system, should be inexpensive, easily milled to a submicrometer particle size, and thermally stable at the film s firing temperature. 

These pigments are sensitive to heat and bleed ia most paint solvents. They are, however, resistant to acids and bases. Their tinctorial strength is considerably greater than that of inorganic yellows but they are weaker than the diaryUde yellows. They are used extensively ia emulsion paints, paper coating compositions, inks (qv), and, depending on particle size, can ia some cases be used outdoors because of excellent lightfastness ia full shades. 

Dispersion at temperatures of 90—110°C is a common final step io European mills processiog wax-coated old cormgated containers. Dispersion temperatures less than 90°C are reported to reduce wax particle size to improve pulp drainage properties on paper machines while improving paper strength (45). Dispersion has been used to reduce hot-melt adhesive, plastic coating, and asphalt particle size. These low density particles can then be removed from the pulp by flotation (46). 

Flame spraying is no longer the most widely used melt-spraying process. In the power-feed method, powders of relatively uniform size (<44 fim (325 mesh)) are fed at a controlled rate into the flame. The torch, which can be held by hand, is aimed a few cm from the surface. The particles remain in the flame envelope until impingement. Particle velocity is typically 46 m/s, and the particles become at least partially molten. Upon impingement, the particles cool rapidly and soHdify to form a relatively porous, but coherent, polycrystalline layer. In the rod-feed system, the flame impinges on the tip of a rod made of the material to be sprayed. As the rod becomes molten, droplets of material leave the rod with the flame. The rod is fed into the flame at a rate commensurate with melt removal. The torch is held at a distance of ca 8 cm from the object to be coated particle velocities are ca 185 m/s. 

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