Transfer film vacuum

Desorption can proceed via several mechanisms. For solids with a negative electron alSnity such as Ar [49,149-151] and N2 [153], the extended electron cloud around a metastable center will interact repulsively with the surrounding medium and metastables formed at the film-vacuum interface will be expelled into vacuum (the so-called cavity expulsion mechanism [161]). Also permitted in solids with positive electron affinities (e.g., CO) is the transfer of energy intramolecular vibration to the molecule-surface bond with the resulting desorption of a molecule in lower vibrational level [153,155,158-160]. Desorption of metastables via the excitation of dissociative molecular (or excimer) electronic states is also possible [49,149-151,154,156,157]. A concise review of the topic can be found in Ref. 162. 

Because of this ready adherence to a substrate, molybdenum disulphide films can be produced in a wide variety of different ways, including flotation from the surface of a liquid, spraying, brushing or dipping in a volatile dispersant, bonding with adhesive or polymeric compounds, rubbing with powder, transfer, and vacuum sputtering. The nature of the initial film produced depends on the way in which it is applied, and all the important types will be discussed in subsequent chapters. 

One factor which may be partly responsible for longer film life in inert gas or vacuum is an improvement in the formation of a transfer film on the sliding counterface as described by Fayeulle et al . Formation of an effective transfer film on the counterface can have a significant effect in reducing wear of the primary film. 

According to the published reports the tests were generally satisfactory, but there appear to have been no operational uses of the technique, and little or no further testing in the intervening forty years. This may be partly due to the complication of arranging a suitable feed system, and partly to the satisfactory development of alternative techniques such as composite retainers and transfer films, and lead lubrication for rolling bearings in vacuum ... 

In contrast with their exceptionally good performance in vacuum, the performance of Type I coatings in air is generally poor. The friction level in air shown in Table 10.2 is fairly typical, and life in air is also poor. In this context it is interesting that Fayeulle et al found that the transfer films formed from Type I coatings in air were highly oxidised, although still basally-oriented. 

Following transfer, film samples were placed in a high vacuum and were shadowcast with germanium at an angle of approximately 10°. The samples were then examined at a direct magnification of at least 5000 times in a modified JEM-Type 7 electron microscope. 

Fig. 5. - Fluorine auger electron spectra from PTFE transfer film (on clean nickel in vacuum) and from bulk PTFE. Load. 2 newtons sliding speed. 0.94 millimeter per second. (To account for charging, the upper peak Is shifted horizontally so that the spectra coincide.)...

Fig. 6. - F(ls) XPS peak from PTFE transfer film on clean nickel in vacuum. Load. 2 newtons sliding speed.

Fig. 7. - Average thickness of PTFE transfer film on nickel at various sliding speeds in vacuum. Load, 2 newtons temperature, 24 to 27° C.

Film Applications PVOH films are used for hospital laundry bags that are added directly to the washing machine without the need for handling the contents. Other PVOH film applications include water-soluble packaging, release films, vacuum bagging, transfer printing, and water-soluble labels. 

Figure 5.2. Two of the more common types of low pressure CVD reactor, (a) Hot Filament Reactor - these utilise a continually pumped vacuum chamber, while process gases are metered in at carefully controlled rates (typically a total flow rate of a few hundred cubic centimetres per minute). Throttle valves maintain the pressure in the chamber at typically 20-30 torr, while a heater is used to bring the substrate up to a temperature of 700-900°C. The substrate to be coated - e.g. a piece of silicon or molybdenum - sits on the heater, a few millimetres beneath a tungsten filament, which is electrically heated to temperatures in excess of 2200 °C. (b) Microwave Plasma Reactor - in these systems, microwave power is coupled into the process gases via an antenna pointing into the chamber. The size of the chamber is altered by a sliding barrier to achieve maximum microwave power transfer, which results in a ball of hot, ionised gas (a plasma ball) sitting on top of the heated substrate, onto which the diamond film is deposited.

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