Direct Evaporation

In direction evaporation, the evaporant is the refractory compound itself, whereas in reactive or activated reactive evaporation (ARE), a metal or a low valency metal compound is evaporated in the presence of a partial pressure of a reactive gas to form a compound deposit, eg, Ti is evaporated in the presence of N2 to form TiN, or Si or SiO is evaporated in the presence of O2 to form Si02. 

Fig. 6-11. Schematic diagram of the kraft pulping process (6). 1, digester 2, blow tank 3, blow heat recovery 4, washers 5, screens 6, dryers 7, oxidation tower 8, foam tank 9, multiple effect evaporator 10, direct evaporator 11, recovery furnace 12, electrostatic precipitator 13, dissolver, 14, causticizer 15, mud filter 16, lime khn 17, slaker 18, sewer.

By assuming a balhstic delivery of material (e.g., from the vapor phase or through directed evaporation) we obtain at least a qualitative picture for the various growth forms of a faceted crystal surface. We assume that the adsorbed material ( A ) behaves differently from the crystalline substrate ( S ). 

In a boiler, with the continued application of heat, steam under pressure is produced via a combination of steam bubble formation (nucleate boiling) and direct evaporation at the steam-water interface (convective boiling), as shown in the sketch of different generated steam flow forms in Figure 1.1. 

Evapotranspiration (ET) is the collective term for land surface evaporation and plant transpiration, which are difficult to isolate in practice. Transpiration refers to the process in which water is transported through plants and returned to the atmosphere through pores in the leaves called stomata, and is distinct from direct evaporation of intercepted precipitation from leaf surfaces. Some land surface processes and the roles of vegetation in the water and energy balances are illustrated in Fig. 6-5. Due to... 

Electrolyte loss occurring in long-term operation of MCFC is another problem to be solved for practical application of MCFC. For commercialization, the MCFC should show stable performance over 40,000 hours. Electrolyte loss in MCFC is caused by various factors, e.g., corrosion of components, creepage, reaction with cell components and direct evaporation. These... 

These workers observed that during Curie Point flash pyrolysis compounds which are reasonably volatile at elevated temperatures do not fragment on the pyrolyser wire but simply evaporate from it. Thus it appeared possible for them that the organic matter present in soils can be characterized and identified very rapidly without any sample pretreatment by direct evaporation/pyrolysis of whole samples. 

Evapotranspiration is a combination of two processes evaporation und transpiration Evaporation covers all water which is directly evaporated from open water surfaces (lakes, rivers, and streams etc.) or wet surfaces (roads, wet vegetation etc.) or sublimated from snow and ice cover. Transpiration covers water which is transported by root plants from the ground to their leaves, and from there is transferred to the atmosphere by the stomata. 

Direct Evaporation. Evaporation can occur with or without dissociation of the compound into fragments. The observed vapor species show that very few compounds evaporate without dissociation. Examples are MgF2, B203, CaF2, SiO, and other Group 14 (IV) divalent oxides, eg, SiO homologues such as GeO and SnO. 

Propane is available in ample quantities and can be produced as a liquid in most refineries. Propane is a highly satisfactory refrigerant and in dewaxing the principle of direct evaporative cooling is employed advantageously. Propane also is cheap, stable, noncorrosive, and nontoxic. 

It is evident that if other substances are present than those indicated, the results obtained by the foregoing motkod will bo to that extent inaccurate. In such cases the other method must bo pursued, and if it is desired to estimate also the proportion of fatty acide and of alkali, special examinations must be made as will bo explained presently. Whenever the object is solely the determination of tho amount of water, the method by direct evaporation is tho simplest and best. To ascertain the proportion of oil or fat in a given sample of soap, tha following process is recommended by Domab —... 

The tear film leaves the surface of the globe and eyelids, enters the upper and the lower punctum at the medial aspect of the lid margin, and enters the lacrimal sac before drainage to the nasolacrimal duct and the nasal cavity. However, much of the tear film is eliminated by direct evaporation or by absorption at the level of the lacrimal sac. The lacrimal outflow system is based on an active and dynamic pumping mechanism. Blinking cycle leads to changes in the drainage canaliculi that activate a pump mechanism that drains tears even with the head held in an inverted position. When the palpebral blink mechanism is impaired, tears accumulation leads to spillover to the skin of the lids and cheek [4],... 

Fig. 6.2. The LP-CVD system for ZnO B deposition, as developed at IMT Neuchatel. DEZ and water vapors are used as precursors, and directly evaporated in the system. In this case, the vapors are not diluted in a carrier gas. Diborane (B2H6) is used as doping gas, 1% diluted in Argon. The total pressure is set to 0.5mbar ( 0.37 Torr), and the substrate is heated to 155°C...

Pesticides are subject to considerable loss by evaporation when they are thinly spread over large areas of crop exposed to moving air. In this situation they are subject also to biochemical, photochemical, and solution losses which make it difficult to assess directly evaporation under field conditions. The rate of evaporation of water is easily determined and has been the subject of much experiment. The relationship of loss of pesticide to loss of water from the same surface can be verified by laboratory experiments. Crystallization and solution in leaf substances exert some effect also. When the pesticide is distributed in the soil, evaporation of water can accelerate that of the water-soluble pesticide the mechanism lies in capillary flow of solution and not in the evaporation process itself. 

The ether is directly evaporated under vacuum without separation of the excess Li and LiBr precipitate. The six-membered ring (me2Si—CH2)3 is partly evaporated with the ether from which it has to be recovered. In the other cases the cyclic compounds can be distilled from the crude product. 

Two methods could be used to prepare the disk samples. One is spin coating. Compound 96 and poly (methyl methacrylate) (PMMA) were dissolved in cyclohexanone and the solution spun coated onto the disk substrate to prepare a photosensitive PMMA thin film on the disk doped with compound 96. The second method is direct evaporation of pure compound 96 to the disk under high vacuum conditions. The structure of the photochromic optical disk sample is shown in Figure 4.3. 

---