Ordered films

The capacity of the ordered film for supporting loads is between that of the static film and that of the dynamic fluid film. The orientation property of the ordered layer gradually becomes weak with the distance apart from the metal surface. The transition occurs as the ordered film appears more important between the two solid surfaces. The thickness of the ordered film is related to the initial viscosity or molecular size of the lubricant, as shown in Fig. 13, so that we can generally write the critical film thickness as follows ... 

The relationship between film thickness of hexadecane with the addition of cholesteryl LCs and rolling speed under different pressures is shown in Fig. 25 [50], where the straight line is the theoretic film thickness calculated from the Hamrock-Dowson formula based on the bulk viscosity under the pressure of 0.174 GPa. It can be seen that for all lubricants, when speed is high, it is in the EHL regime and a speed index 4> about 0.67 is produced. When the rolling speed decreases and the film thickness falls to about 30 nm, the static adsorption film and ordered fluid film cannot be negligible, and the gradient reduces to less than 0.67 and the transition from EHL to TFL occurs. For pure hexadecane, due to the weak interaction between hexadecane molecules and metal surfaces, the static and ordered films are very thin. EHL... 

Boundary lubrication (BL) can also evolve into TFL in a bottom-up way [11]. Compared to BL, TFL has a thicker film. In the vicinity of solid walls, the liquid molecules take the states of that of the boundary film, the ordered one, and the disordered one, from the wall surfaces to the center of the gap. From a mechanical point of view, the existence of an ordered film makes the lubricant film differ strongly from the boundary film, which can form a glassy state or solid-like... 

Further perfection of the mathematical model based on the ordered film ... 

In order to study microscale friction and wear, scientists have developed the friction force microscope (FFM), nanoindentation and nanoscratch tester which serve as excellent tools in micro tribological research [1,6-9]. In this chapter, we first compare the differences between macro and micro friction and wear, and then introduce some results of our research group on microscale friction and wear of ordered films, thin solid films, and multilayers. 

Fig. 9 EPR spectra of color center in MgCl2 films for two different preparation conditions a film grown at lower temperature b initially well-ordered film after bombardment with electrons and argon ions...

Fabrication of composite colloidal spheres involves two steps submicron particles are fabricated from a material preferentially responsive to one class of chemicals followed by a step in which the submicron spheres are coated with a shell that is preferentially responsive to another class of chemicals. A colloidal crystal array is subsequently self-assembled into a 3D ordered film. 

In this paper we describe the preparation of thin polymer films by surface catalysis and anodic deposition. The results indicate that both synthesis routes produce orientationally ordered films that have similar infrared spectra. It is also shown that thin ordered films of poly(thiophene) have different electrochemical behavior than the fibrous films that are electrically conducting. 

As was noted above, the structure and behavior of Nation polymers were intensively investigated and structural models were suggested. It is obvious that during the transformation from precursor (nonionic form) to ionic form the internal structure of the polymer is reorganized into the ordered type. But this order has a random nature, and all earlier investigations were peformed with such randomly ordered films. 

Ordered overlayers are not achieved in all systems, however, and it appears that certain criteria need to be met to form well-ordered films. Although cyclopentene and 1,5-cyclooctadiene could be used to produce ordered monolayer films through [2 + 2] attachment [221], a number of other alkenes investigated did not adsorb... 

The biotin-streptavidin affinity has been made use of by biochemists for some years but has only been used recently for the formation of ordered films. There exist two closely related proteins, avidin and streptavidin,... 

A general characteristic of all the data shown in Figures 4 and 5 is the relatively slow initial response time and even slower return to baseline as the concentration of the test vapor was reduced. Because of the exponential dilution of vapor flowing to the sensor, the concentration dropped to 8.5% of its initial value after 25 minutes and to 0.3% of the initial value by the end of an hour. The sublimed films obviously do not equilibrate rapidly with the test vapors. This is a major reason for the interest in being able to deposit ultra-thin, ordered films reproducibly by the L-B technique. 

Wargacki SP, Pate B, Vaia RA (2008) Fabrication of 2D ordered films of tobacco mosaic virus (TMV) processing morphology correlations for convective assembly. Langmuir 24 5439-5444... 

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