Powder deposition

Slip casting of metal powders closely follows ceramic slip casting techniques (see Ceramics). SHp, which is a viscous Hquid containing finely divided metal particles in a stable suspension, is poured into a plaster-of-Paris mold of the shape desired. As the Hquid is absorbed by the mold, the metal particles are carried to the wall and deposited there. This occurs equally in all directions and equally for metal particles of all sizes which gives a uniformly thick layer of powder deposited at the mold wall. 

Mist and spray humidifiers, unless the water is pure, will leave a powder deposit of these salts in the conditioned space. 

The existence of materials now included among the conducting polymers has long been known. The first electrochemical syntheses and their characterization as insoluble systems took place well over a century ago. In 1862 Letheby reported the anodic oxidation of aniline in a solution of diluted sulphuric acid, and that the blue-black, shiny powder deposited on a platinum electrode was insoluble in HjO, alcohol, and other organic solvents. Further experiments, including analytical studies, led Goppelsroeder to postulate in 1876 that oligomers were formed by the oxidation of aniline. 

Rhodium and platinum metals can be more conveniently vaporized with electron-beam vaporization source, in a stainless steel reactor, starting from metal powders deposited into a graphite crucible. 

Continuous Processes Based on Electrostatic Powder Deposition... 

The devices are further claimed to ensure that magnetically treated water keeps minerals in a soft amorphous powder form instead of the usual hard crystalline structure. This amorphous powder deposits a thin film of aragonite talc on the inside of pipes and the waterside of condensers which prevents free oxygen in the water from attacking the metal surfaces. ... 

Inhalation and direct skin contact are the most common routes of chemical exposure. The greatest exposure risk in handling potent compounds in an analytical laboratory therefore occurs when handling solid materials due to the potential to generate and inhale airborne dust particles of the compound. Once the potent material has been placed into solution, the airborne exposure risk is reduced and solutions of potent compounds may be handled in a manner similar to other nonpotent pharmaceutical compounds, assuming good laboratory practices are followed. Caution should be taken not to aerosolize the solutions since this could create an inhalation hazard. In addition, any sample solution spills should be adequately cleaned to prevent powder deposits of the compound from forming, which could potentially become airborne after the liquid has dried. 

An additional consideration is the use of absorbent, plastic-backed paper on laboratory benches or work surfaces. These papers can absorb any spills, minimizing the risk of forming powder deposits of the potent compound after the spill has dried. 

Tissue deposits are less available to bark beetle predators and parasites searching the bark surface for their host. Therefore, they offer more specificity toward the target insect. Further, tissue deposits may be easier to reproduce consistently. Unless we acquire better understanding of the factors that control crystallization, we will find it difficult to control the character of surface deposits obtained from solution. On the other hand, the character of wettable powder deposits seems to be more easily controlled (particle size, density). 

Uda, M. Trans. Nat. Res. Inst. Metals 1982, 24, 218 (nickel powder deposited from its vapor). 

The solution decomposes on warming, the tetroxide being produced and a black powder deposited. 

The sulphide is a pure white powder, deposited when a rapid stream of hydrogen sulphide is passed into a pyridine solution of the bromide at —10° C. If left in a moist state it soon decomposes. 

Excess solution (Fp < Vg) is used for synthesis of powdered and granulated supported catalysts, if the adsorption is very intense, as well as for the preparation of powdered deposited catalysts. 

The grain refinement is achieved by an increase in the nucleation rate. The first four deposit types are seen with two-dimensional nucleation, but UD type requires three-dimensional or secondary nucleation. The nucleation intensity increases with increasing inhibition and deposition current density. The FI type of crystals is usually seen at low inhibition. With increasing current density, the deposit form changes from whiskers to prismatic crystals, dendrites, and finally powder deposits. The BR type is seen at moderate inhibition level and the deposit follows the structure of the base material. 

Figure 45. SEM photomicrographs of the copper powder deposits obtained by electrodeposition at an overpotential of 650 mV from (a) 0.075 M CUSO4 in 0.50 M H2SO4 (b, c) 0.30 M CUSO4 in 0.50 M H2SO4. (Reprinted from Ref.80 with permission from Elsevier).

To examine the adhesion of copper deposits to barrier layers, direct plating on barrier layer was compared between ECD seed bath and an acid copper sulfate bath. The acid copper sulfate bath normally produces powdered deposit with poor adhesion that can be easily washed off with water. ECD seed bath provides a continuous, smooth copper deposit with much better adhesion to barrier layers such as TiN, TaN, and WNx. Table 1... 

A visually graphic display of this mechanism is illustrated in Figure 5.15. An insoluble colored powder, deposited on the face of an interfacial polyamide film, becomes incorporated into the polyamide film if the powder is introduced on the organic phase side. However, if the powder is deposited on the aqueous phase side of the growing interfacial film, it remains loose and unattached. 

Laser sintering of ceramic fine powders deposited onto ceramic substrates is show to be an appropriate technique to fabricate micro- and nanoporous ceramic filters. The requirements to the filter materials are discussed. 

The weight of the sample powders deposited by EPD tended to increase as the migration time was longer, regardless of the calcination temperature at which the sample powders were prepared. The maximum deposit weight was 115.2 m cm, with the sample prepared at a calcination temperature of 1200 °C, followed by 70.0 mg/cm with the sample powder prepared at 1300 °C, and 66.6... 

Toner is a complex powder deposited by a laser printer to form an image (in our case the channel walls). Laser printers force toner powder to form the desired image on the polyester film and as... 

S. Rosi, M. Fedel, F. Deflorian, S. Zanol, Influence of different color pigments on the properties of powder deposited organic coatings, Mater. Des. 50 (2013) 332—341. 

---