Rubbing direction

Figure 9-7. Elastic electron-diffraction pattern of a highly textured hcxaphenyl film. The Miller indices arc assigned using the intcrplauar spacings calculated in Kef. 11371. Inset Intensity of the f020) peak as a function of the angle between momentum transfer and the Teflon rubbing direction (see text) - taken from Ref. 138. ...

When surfaces of tribological systems are involved in the mechanical activity of rubbing, direct reactions of surface adsorbed films with solid surfaces take place. The mechanically activated clean surface (nascent surface) of the metals and alloys is extremely reactive. Tribofilm formation is caused by the interaction between the metal (M, substrate) nascent surface under high energy and chemisorbed molecules of additive (adsorbate) (Buckley, 1981). 

The first nematic guest-host prototype nematic guest-host display device contained a nematic liquid crystal (4-butoxybenzoic acid) and a pleochroic dye (methyl red or indophenol blue) sandwiched between two (Nesa) electrodes dTn 12/im) rubbed uniaxially, but with no additional orientation layer, see Figure 3.14. One polariser was fixed to the front substrate surface with its direction of maximum absorption parallel to the rubbing direction and, therefore, the nematic director. 

Schematic diagrams of die cell and apparatus for measuring die temperature dependence of die optical rotation of an aligned nematic liquid crystal cell. The birefringence cell is formed from microscope slides and die lines in the cell denote the rubbing direction for the glass plates and thus the direction for the nematic director n.

The Step 8B film was coated onto the optically anisotropic layer, placed in a thermostatic chamber at 80°C, and heated for 5 minutes 60°. Thereafter the film was cooled at 40° C for 30 seconds in a thermostatic chamber that had an oxygen content of 2% and then irradiated with ultraviolet radiation at 600 nm. The film was next cooled to ambient temperature, and the retardation film was isolated having an optically anisotropic layer thickness of 1.55 pm. The retardation in the direction perpendicular to the face of the retardation film was 150 nm parallel to the rubbing direction. 

FIGURE 10.5. Polarized absorption spectra of aligned (a) glassy PFO film and (b) crystallized PFO films. The spectra were measured for light polarized parallel (solid line) and perpendicular (dashed line) to the rubbing direction. (From Ref. 12.)... 

FIGURE 10.20. EL spectra of a thermally aligned ITO doped-PI PF2/6 Ca LED with the polarizer aligned parallel (filled circles) or perpendicular (open circles) to the rubbing direction. Inset Luminance-voltage characteristics for devices with doped (filled squares) and undoped (open circles) PI layers. (From Ref. 4.)... 

Figure 10.20 shows the polarized EL spectra of an aligned PF2/6 LED device measured parallel and orthogonal to the rubbing direction.4 The parallel EL has peaks at 425, 451, nm 477 nm, with a shoulder at approximately 505 nm. The corresponding spectra for perpendicular detection are blue-shifted by about 5 nm. The most intense peak is at 477 nm and has a polarization ratio of 15, significantly higher than the polarization measured in absorbance. One attractive possibility... 

Fig. 21 Experimental geometry and schematics of the aligned PF2/6 films. Above-. Uniaxi-ally aligned frozen-in nematic PF2/6 microstructures. Below Biaxially aligned hexagonal PF2/6 microstructures with crystallite types I—III. Assuming chain alignment (i.e., the c axis) along the rubbing direction, then the equatorial and meridional directions may be defined by the (xyO) plane and z-axis, respectively. See [114,115] for details...

Fig. 22 Example NEXAFS data from an aligned PF2/6 film spin cast on rubbed PI. Parallel Geometry refers to E-field parallel to the rubbing direction. 0 is the angle between surface normal and electric field vector of the incident light in conjunction with the rubbing direction of the polyimide substrate. See [114] for details...

Fig. 3.85 (a) Schematic of the polyimide rubbing process TM-AFM height images (z-scale 3 nm) of (b) the pristine polyimide film, and (c) and (d) a rubbed film. The rub direction in (c) was from upper left to lower right, in (d) vertical. Reprinted with permission of John Wiley Sons, Inc. from [176]. Copyright 2001. John Wiley Sons, Inc. 

The present chapter deals with frictional behavior when lubricated surfaces rub against each other. In Chapter 7 attention was called to the distinction between viscous loss in a fluid film separating two solid surfaces and the friction of the surfaces rubbing directly against one another. In this chapter we shall discuss the type of lubrication in which the rubbing surfaces that carry the lubricant participate intrinsically in the lubrication process rather than merely as the geometric boundaries of the fluid film. The treatment of lubricated friction here will be mainly descriptive detailed analysis and discussion of theoretical models for lubricated frictional rubbing is reserved for subsequent chapters. 

The reverse contrast, i.e. bright characters on dark, can be achieved by orientating one polarizer parallel to the rubbing direction and the other one perpendicular to it, so that the device is dark in the off state. Backlit versions of this device are used in car dashboard displays [111]. 

Yamamoto et a. [60-62] and Kurata et al [63] prepared polythiophene layers by vacuum evaporation. To ensure the deposition of poly- and not oligothiophenes, they removed low molecular weight material ( < 15-17) by Soxhlet extraction with CHCI3, The evaporated material is assumed to consist of poly-thiophene with a molecular weight of about 1500-2000 and 20-25 thiophene units. The X-ray and electron diffraction data of Yamamoto et al. point to a (partially) crystalline film with the polymer axes oriented perpendicular to a carbon or gold substrate plane if sub = 423 K. At lower substrate temperatures, the orientation and crystallinity are worse. This behaviour is not only true for the first deposited layer, but at least up to 10 layers, i.e, 100 nm. On polyimide substrates, however, the molecules lie on the substrate plane and orient along the rubbing direction of the polyimide [61]. 

Figure 12.11. AFM images of PEO nanocylinders in bulk films of azo LCBCs (3.1 xm X 12.4 Jim). In the left panel, the PEO nanocylinders are aligned parallel to the rubbing direction, whereas the PEO nanocylinders are oriented perpendicular to the substrate in the right panel. Source Reproduced with modifications from Yu et al., 2006b. See color insert.

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