Spray-deposition

The process of spray deposition presents a convenient technological method for fabrication of low cost solar cells. The spray solution containing f.i. cadmium chloride and thiourea (or other Cd and S compounds respectively) at low concentration is sprayed at rates of about 15-30 cm /min on a substrate heated up to temperatures between 300 and 400 °C. There exists a large variety of starting materials, which have to satisfy the condition a) that they must be soluble in the liquid which may contain the dopants as well and b) that the remainder must be completely volatilized. 

The crystallinity is strongly influenced by the substrate temperature. The size of crystallites can be increased by heat treatment in an inert atmosphere. The following reactions lead to the formation of a crystalline film  

The airanonium salts decompose at elevated substrate temperatures. By appropriate use and composition of the starting materials for the base materials for thin film solar cells, namely CdS and Cd Znj j S, have been prepared by different authors /11,12,13/. 

In some cases AICI3 is added to the spray solution to prevent Cu diffusion along the grain boundaries during Cu S formation process /14/. 

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Material Density (g/cm 1 Coating weight (kg/m ) 0-025 mm thickness Brinell hardness Ratio of contraction stresses in sprayed deposits 0-51 mm thick Compressive strength (stress to collapse) (MN/m )... 

Spraying conditions make hardness values so variable that unless they are accurately known no comparisons are possible. Brinell hardness figures for sprayed molybdenum vary from 350 when produced with a reducing flame to 725 with an oxidising flame, and while a thick sprayed deposit of 0-8% carbon steel can give a figure of 330, the hardness of a particle obtained by micro hardness methods will be about 550. 

Thin zinc sprayed deposits of 0 05 mm in thickness are used as a base for stove enamelled finishes on such structures as radar cabinets. 

The major advance in the way in which column eluate is deposited on the belt was the introduction of spray deposition devices to replace the original method which was simply to drop liquid onto the belt via a capillary tube connected directly to the outlet of the HPLC column. These devices, based on the gas-assisted nebulizer [5], have high deposition efficiencies, transfer of sample can approach 100% with mobile phases containing up to 90% water, and give constant sample deposition with little band broadening. 

The use of spray deposition increases the range of solvents which can be used in moving-belt LC-MS and the range of solutes that can be studied by this technique. Since less heat is required to remove the solvent, it is less likely that the solute will be inadvertently removed from the belt or undergo thermal degradation. It is not, however, unknown for particularly volatile and labile analytes to be lost when using spray deposition. 

The interface can be used with a wide range of HPLC conditions, flow rates and mobile phases, both normal and reverse phase, particularly if spray deposition is employed. 

Spray deposition A method used to apply HPLC eluate in later versions of the moving-belt interface to provide a uniform layer of mobile phase on the belt and thus minimize the production of droplets. 

Application verification (AV) monitors are devices that are placed within test plots to measure actual spray deposition that occurred during application. The main function of AV monitors is to show whether or not the intended amount of test material was actually deposited on the soil surface. Application monitors consisting of soil-filled containers, paper disks, polyurethane foam plugs, and glass Petri dishes have all been used successfully for this purpose. Prior to using a monitor in the field, it is important to determine that the test substance can indeed be successfully extracted from the monitor and that the compound will be stable on the monitor under field conditions... 

Colored and fluorescent dyes have the advantage of being relatively cheap and easy to use. Standard procedures are available for detection of the dyes using colorimeters and fluorimeters. Some of these instruments can be used in the field to analyze samples as they are collected following exposure to the dyes. Fluorescein has been widely used for studying spray deposition within and outside canopies. ... 

The layout of a field study site needs to be established based on the study objectives. Typically, several lines of sample will be laid out in the downwind direction from the application area, perpendicular to the sprayer travel direction assuming a cross-wind normal to the application direction. Three or more parallel lines will provide useful information on spray deposition in the sampling area. If wind directions may be variable, these lines can be set up in various directions radiating outwards from the application area. 

Other paper collectors that have been used to assess droplet size and distribution patterns include cards such as Kromekote. This was one of several types of collector that provided information on spray deposition in the held, a-Cellulose samplers are fibrous in nature, and include a vertical component to their aspect. This type of collector, along with Mylar cards and other types of card samplers, are often used to provide information on spray coverage as amount of material per unit surface area. 

A.J. Hewitt, Methodologies for the Quantification of Spray Deposition and Drift in Field Applications, ASAE Paper No. 001028, American Society of Agricultural Engineers, Milwaukee, WI (2000). 

Any possible risk to users while spraying plant-protection products must be evaluated before its authorization. When it is necessary for workers to reenter crops shortly after their treatment, they may be exposed to the plant-protection product through contact with the spray deposit therefore, this possible means of exposure must be evaluated when a plant-protection product is to be used. This chapter discusses the procedure for and some examples of the assessment of re-entry exposure and provides instructions for placing protective measures on product labels if dermal and inhalative exposure is relevant. 

Do not re-enter treated areas/crops before the spray deposit is completely dry. 

Particularly desirable among film deposition processes are solution-based techniques, because of the relative simplicity and potential economy of these approaches. However, the covalent character of the metal chalcogenides, which provides the benefit of the desired electronic properties (e.g., high electrical mobility), represents an important barrier for solution processing. Several methods have been developed to overcome the solubility problem, including spray deposition, bath-based techniques, and electrochemical routes, each of which will be discussed in later chapters. In this chapter, a very simple dimensional reduction approach will be considered as a means of achieving a convenient solution-based route to film deposition. 

Figure 14.2. Ultrasonic spray deposited CuInSe2 film for photovoltaic applications using mixed-metal organic precursors. XRD shows (left) the growth of nearly phase pure CuInSe2, and optical micrographs show reasonable morphologies (right).

FIGURE 6.13 Schematic diagram of plasma spray deposition processing, (a) Radial injection of feedstock into plasma torch, showing partial entrainment of feed particles into the plasma jet and (b) axial injection of feedstock into plasma torch, showing more complete entrainment of feed particles into the plasma jet. 

Spray cleaning, of metal surfaces, 16 213 Spray coating processes, 7 23, 68-76 economic aspects, 7 75-76 Spray column absorbers, 1 27 Spray cone angle, 23 187 Spray correlations, 23 189-192 Spray deposition, of metal-matrix composites, 16 173 Spray-dried products, 11 542-543 Spray-dried resins, production of,... 

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