Removal of material

Diflfiision, convection and migration are the fonns of mass transport that contribute to the essential supply and removal of material to and from the electrode surface [1, 2, 3 and 4],... 

Heat Transfer Pastes are often heated or cooled by heat transfer through the walls of the container or hollow mixing arms. Good agitation, a large ratio of transfer surface to mixer volume, and frequent removal of material from the surface are essential for high rates of heat transfer. Sometimes evaporation of part of the mix is used for cooling. 

Chemical cleaning implies the removal of material from the surface of the specimen by dissolution in an appropriate chemical agent. Solvents such as acetone, carbon tetrachloride, and alcohol are used to remove oil, grease, or resin and are usually apphed prior to other methods of cleaning. Various chemicals are chosen for appheation to specific materials some of these treatments in general use are outlined in the NACE standard. 

If a sample of polycrystalline material is rotated during the sputtering process, the individual grains will be sputtered from multiple directions and nonuniform removal of material can be prevented. This technique has been successfully used in AES analysis to characterize several materials, including metal films. Figure 9 indicates the improvement in depth resolution obtained in an AES profile of five cycles of nickel and chromium layers on silicon. Each layer is about 50 nm thick, except for a thinner nickel layer at the surface, and the total structure thickness is about 0.5 pm. There can be a problem if the surface is rough and the analysis area is small (less than 0.1-pm diameter), as is typical for AES. In this case the area of interest can rotate on and off of a specific feature and the profile will be jagged. 

Selection of the off-take position is important from the standpoint of the amount of material removed. Locating the off-take in the proximity of the material stream or at points of splash will result in greater removal of materials. This positioning may be desirable as a means to control splash effects provided that the off-take velocity is kept low. 

Fretting in air-saturated aqueous electrolytes, such as seawater or body fluids , produces enhanced removal of material by stimulation of electrochemical reactions, increasing the reaction rates by factors of 10 to 200 compared with air, depending on the frequency. The importance of the chemical... 

Though short fiber-reinforced mbber composites find application in hose, belt, tires, and automotives [57,98,133,164] recent attention has been focused on the suitability of such composites in high-performance applications. One of the most important recent applications of short fiber-mbber composite is as thermal insulators where the material will protect the metallic casing by undergoing a process called ablation, which is described in a broad sense as the sacrificial removal of material to protect stmcrnres subjected to high rates of heat transfer [190]. Fiber-reinforced polymer composites are potential ablative materials because of their high specific heat, low thermal conductivity, and ability of the fiber to retain the char formed during ablation [191-194]. 

Purification of biopharmaceuticals often involves the removal of materials with physical characteristics very similar to the desired product, such as failure sequences from DNA synthesis or misfolded proteins from bacterial fermentations. The contaminants, however, may have biological characteristics very different from the desired product, including different antigenicities, bioactivities, and specificities. There are even systems in which the... 

Optimization of reactor geometry in terms of charging and removal of materials... 

The amount of exogenous drug is difficult to determine. Before conducting release experiments, loaded halloysite was always washed with a large amount of water during a 5 minute rinse to ensure removal of material from the surface. However, we cannot exclude some of the active agent being attached to the outer surface of the halloysite, especially in the natural gap-defects on the cylinder surface at the end of the rolled clay sheet (it is a natural pocket on the tubule surface). The typical 5-10 % initial release burst we observed may be related to dissolution of this material. 

Cyclone filters are effective at removing larger particles and can operate over a wide range of temperatures, limited primarily by the material of construction. Cyclone filters are often designed as multiple units in series (multi-clones). They can remove >90% of particulates above about 5 microns in diameter at minimal pressure drops of 0.01 atm. Partial removal of material in the 1.5 micron range is also possible, but cyclonic filters become ineffective with sub-micron particles. 

The process involves removal of materials less dense than water (such as oil) and suspended materials that are more dense than water by settling. The API separator does not separate substances in solution, nor does it break emulsions. The effectiveness of a separator depends on the temperature of the water, the density and size of the oil globules, and the amounts and characteristics of the suspended materials. The susceptibility to separation (STS) test is normally used as a guide to determine what portion of the influent to a separator is amenable to gravity separation [38]. In terms of globule size, an API separator is effective down to globule diameters of 0.015 cm (15 microns). 

For the polishing behavior of trench features, removal of material at the top and bottom of the trench is proportional to the fraction of the area in asperity contact. From Eq. (3), the reduction in step height dh/dt could then be expressed as... 

We consider conditions where there is no significant island or void nucleation on the terraces, and surface mass transport is associated with the addition and removal of material from the preexisting surface steps. This provides an important simplification since the number of steps is now a conserved quantity and we do not have to deal with problems arising from the annihilation of steps of different sign. 

However, one anomalous feature of this technique is that there occurs an apparent rapid removal of material from the concentration gradient at the boundary, as evidenced by a reduction in the area under the Schlieren curve. For the standard PVP/dextran T10 system, we observed a reduction of 20 % during the 10 min after the formation of the initial boundary no further changes in the area occurred after this initial event. This reduction in area is not accompanied by the appearance of refractive index gradients elsewhere in the cell47 . The redistribution of material within the cell has been shown to occur by monitoring PVP 360 directly using absorption optics at 237 nm. 

The most successful uses of surfactants to accelerate desorption and enhanced biodegradation has clearly been associated with the soil-washing industry (U.S. EPA, 1989) and bioslurry reactors (Oberbremer et al., 1990 Mueller et al.y 1991b,c). Here too, however, problems have been encountered at the bench-, pilot-, and full-scale levels with inefficient removal of materials from soils and sediments containing appreciable amounts of clay (c. >25%) or organic matter (c. >10%). 

Ablation means removal of material from the surface of an object by vaporization, chipping, or other erosive processes. The term occurs in Space Physics [5]. In space vehicle design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. A low-density EPDM rubber is a fire stopping and fire proofing product that can be ablative in nature. 

ABLATION- The removal of surface material from a body by vaporization, melting, chipping, or other erosive process specifically, the intentional removal of material from a nose cone or spacecraft during high-speed... 

In this chapter we discuss how solid surfaces can be modified. Surface modification is essential for many applications, for example, to reduce friction and wear, to make implants biocompatible, or to coat sensors [405,406], Solid surfaces can be changed by various means such as adsorption, thin film deposition, chemical reactions, or removal of material. Some of these topics have already been discussed, for example in the chapter on adsorption. Therefore, we focus on the remaining methods. Even then we can only give examples because there are so many different techniques reflecting diverse applications in different communities. 

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