Scratch, scratches

The degradation of surface appearance is generally connected with wear, but in the case of textiles it has also secondary effects like "fluffing" and "pilling". In plastics the surface appearance is mainly determined by scratching. Scratch hardness is the main parameter. In textiles the coefficient of friction is the main factor. 

Fig. 60. The AFM image of the scratch produced on Si by the spherical tool. Microridges 3 and 4 were formed between ridges 1 and 2. The orientation and number of ridges change along the scratch. Scratching direction from bottom to top.

The scratch repassivation technique discussed above may be more useful for studying SCC than pitting [107]. This is because natural pitting is often initiated at defect sites in the passive film that are electronic or chemical in nature. Such sites are not necessarily probed by a mech inical scratch. Scratching can simulate SCC where mechanical film rupture processes are operative and anodic dissolution controls the SCC process. In general, once the passive film is mechanically disturbed at some potential, an electrochemical current can be measured that will decay back to a low level when repassivation has occurred. A measure of the crack growth rate, V, (cm/s) can be obtained from these data... 

Overall, use of learning systems has two main advantages. First, the construction cost may be lower, certainly if the system is not construeted from scratch but uses existing software tools and components. Second, a learning system is able to adapt to changing conditions, though not always on-line. 

Qualitative examples abound. Perfect crystals of sodium carbonate, sulfate, or phosphate may be kept for years without efflorescing, although if scratched, they begin to do so immediately. Too strongly heated or burned lime or plaster of Paris takes up the first traces of water only with difficulty. Reactions of this type tend to be autocat-alytic. The initial rate is slow, due to the absence of the necessary linear interface, but the rate accelerates as more and more product is formed. See Refs. 147-153 for other examples. Ruckenstein [154] has discussed a kinetic model based on nucleation theory. There is certainly evidence that patches of product may be present, as in the oxidation of Mo(lOO) surfaces [155], and that surface defects are important [156]. There may be catalysis thus reaction VII-27 is catalyzed by water vapor [157]. A topotactic reaction is one where the product or products retain the external crystalline shape of the reactant crystal [158]. More often, however, there is a complicated morphology with pitting, cracking, and pore formation, as with calcium carbonate [159]. 

Finally, we consider the complete molecular Hamiltonian which contains not only temis depending on the electron spin, but also temis depending on the nuclear spin / (see chapter 7 of [1]). This Hamiltonian conmiutes with the components of Pgiven in (equation Al.4,1). The diagonalization of the matrix representation of the complete molecular Hamiltonian proceeds as described in section Al.4,1.1. The theory of rotational synnnetry is an extensive subject and we have only scratched the surface here. A relatively new book, which is concemed with molecules, is by Zare [6] (see [7] for the solutions to all the problems in [6] and a list of the errors). This book describes, for example, the method for obtaining the fimctioiis ... 

Carpick R W and Saimeron M 1997 Scratching the surface fundamentai investigations of triboiogy with atomic force microscopy Chem. Rev. 97 1163-94... 

Concentrated nitric acid renders the metal passive , i.e. chemically unreactive, due to formation of a thin oxide surface film (which can be removed by scratching or heating in hydrogen). 

Cillan M J 1991. Calculating the Properties of Materials from Scratch, In Meyer M and V Pontikis (Editors). Computer Simulation, NATO ASI Series E 205 (Computer Simulations in Materials Science) pp. 257-281. 

If the solid does not dissolve in the cold solvent gently heat the mixture over a micro-Bunsen burner or in a small water-ba until the liquid boils. Continue to add o-i ml. portions of solvent until the solid dissolves. [If more than about i ml. of solvent is required, the solvent is considered unsatisfactory.] If a clear solution is obtained, cool the tube and scratch it below the surface of the solution with a very fine glass rod and proceed as suggested on p. 16. In general, the products from the choice of solvent investigation are not discarded but added to the main bulk of the crude product for recrystallisation. 

Naphthyl Acetate. CHgCOOCi H,. Dissolve 1 g. of pure 2-naphtnol in 5 ml. (r8 mols.) of 10% sodium hydroxide solution as before, add 10 g. of crushed ice, and i-i ml. (1-14 g., 1 5 mols.) of acetic anhydride. Shake the mixture vigorously for about 10-15 minutes the 2-naphthyl acetate separates as colourless crystals. Filter at the pump, wash with water, drain, and dry thoroughly. Yield of crude material, 1-4 g. (theoretical). Recrystallise from petroleum (b.p. 60-80 ), from which, on cooling and scratching, the 2-naphthyl acetate separates as colourless crystals, m.p, 71 yield, 10 g. 

If difficulty is experienced in inducing the first crude crop of the a-glucoside to ciystallise, place a few drops of the solution on a watch glass and expose freely to the air, with occasional scratching meanwhile keep the main volume of the solution securely corked in the conical flask. After an interval of varying length (possibly several days), partial crystallisation occurs in the material on the watch-glass. Then seed the solution with this material crystallisation of the first main crop will rapidly follow. 

Use. If the substance under investigation is soluble in water, dissolve about 0 1 g. in 1-2 ml. of water, and add 5-10 ml. of Reagent A. On shaking for a few minutes, with scratching if necessary, the yellowish-orange hydrazone will usually separate if this does not occur, warm the solution gently in a hot water-bath for 5-10 minutes. 

To 2 ml. of the ester in a test-tube add slightly more than the same volume of a cold saturated aqueous copper acetate solution. The blue colour of the latter turns immediately to a pale green. Now shake the tube vigorously in order to produce an emulsion of the ester in the aqueous layer. Scratch the sides of the tube with a rod, and shake vigorously as before. Crystallisation may be delayed for about 5 minutes, but, when once started, rapidly gives a copious precipitate... 

Undergoes Cannizzaro s reaction, giving benzyl alcohol and benzoic acid (p. 229). Warm gently for several minutes, cool, add a few ml. of water and then cone. HCl, and cool again. Crystals of benzoic acid separate out on scratching the sides of the tube with a glass rod. 

Then add 3 drops of acetophenone (or about 0 3 g. of powdered benzo-phenone dissolved in 1 ml. of acetic acid) and shake the mixture. A precipitate of the phenylhydrazone is produced on scratching. 

Dibromide formation. Dissolve 0 2 ml. of styrene in 0 5 ml. of CCI4 in a test-tube. Add slowly, drop by drop, a 10% solution of bromine in CCI4. Note the decolorisation of the bromine and absence of HBr fumes (therefore reaction by addition and not by substitution). Continue to add the bromine solution until a faint brown colour persists. Scratch the sides of the tube and cool it in ice-water. Filter off the crystals that separate and recrystallise the styrene dibromide from methanol m.p. 72 . 

Add dil. H2SO4 until the solution is acid to litmus. Cool, and scratch the sides of the vessel with a glass rod a white precipitate indicates an aromatic carboxylic acid or uric acid, or a solid phenol insoluble in water (e.g., i- or 2-naphthol). If a precipitate is obtained, filter off through a Buchner funnel, wash with water, recrystallise if necessary and identify. 

Now roll up the Carius tube (while still in a vertical position) in a strip of ordinary thick drying paper, and then place it in the heavy iron protector tube if the Carius tube is too short and tends to disappear within the iron tube, a short section of old glass tubing should first be placed in the iron tube so that the capillary of the Carius tube just projects. The function of the paper is to protect the Carius tubing from being scratched, and also (more important) to prevent the local overheating which would otherwise occur at places where the Carius tube is in direct contact with the iron tube. The sealed tube, throughout its manipulation, should be left as nearly vertical as possible, so that the contents do not leave the rounded end. 

Opens formatted file channels for input and output and the scratch files that are required during the calculations. 

I STORES SHAPE FUNCTIONS AND THEIR DERIVATIVES AT REDUCED INTEGRATION POINTS(SCRATCH FILE)... 

Write and run an MM3 input file for methane from scratch, that is, open an empty file and put in all the necessary infomiation to do the MM3 calculation on CH4. What is the enthalpy of formation of CH4 What are the C—H bond lengths and angles ... 

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