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Experimental methods, hard solids

Our technique is the first new experimental method for investigating nucleation in 50 years. So we evolved into a new field. We have obtained results both for the freezing of liquids and for certain solid state transitions. It is satisfying but it is also hard work. [Pg.76]

The two basic types of mechanical deformation, from a physical and molecular standpoint, are shear and dilatation. The experimental methods described in the preceding three chapters yield information primarily about shear only in extension measurements on hard solids does a perceptible volume change influence the results. By combining shear and extension measurements, the bulk properties can be calculated by difference, as for example in creep by equation 55 of Chapter 1, but the subtraction is unfavorable for achieving a precise result. Alternatively, bulk properties can be measured directly, or they can be obtained by combining data on shear and bulk longitudinal def ormations (corresponding to the modulus M discussed in Chapter 1), where the subtraction does not involve such a loss of precision. Methods for such measurements will now be described. They have been reviewed in more detail by Marvin and McKinney. ... [Pg.168]

The last state in Fig. 11.1 that has not yet been discussed is the state of the neat liquid compound X. For liquid compounds this is the relevant initial state for solubility, but almost aU drug-Uke compounds are solid at room temperature. In this case the neat liquid is a virtual state of a supercooled liquid which can hardly be accessed experimentally. However, it is an interesting intermediate state because it allows us to split the calculation of solubility into two separate steps, which are conceptually and for some methods computationally easier to handle than the complete step from the crystaUine state of the drug to the liquid state of the drug dissolved in water. In the first step we only have to transfer the compound from its neat crystalline state to its neat liquid state. The free energy of this fusion transfer is usually called AG s (or if considered in the opposite direction). [Pg.289]

Chemical vapor deposition (CVD) is an atomistic surface modification process where a thin solid coating is deposited on an underlying heated substrate via a chemical reaction from the vapor or gas phase. The occurrence of this chemical reaction is an essential characteristic of the CVD method. The chemical reaction is generally activated thermally by resistance heat, RF, plasma and laser. Furthermore, the effects of the process variables such as temperature, pressure, flow rates, and input concentrations on these reactions must be understood. With proper selection of process parameters, the coating structure/properties such as hardness, toughness, elastic modulus, adhesion, thermal shock resistance and corrosion, wear and oxidation resistance can be controlled or tailored for a variety of applications. The optimum experimental parameters and the level to which... [Pg.23]

The EEM formalism represents a comprehensive and internally consistent framework for the quantitative as well as qualitative understanding and computation of atom-in-a-molecule sensitivities. The method is direct, due to an adequate separation of the variables, allowed by a spherical-atom approximation. The potential for studying molecules, (ionic) solids and molecule-surface interactions has been fully demonstrated. There are several parameterizations possible, all of them relying on quantum-mechanical calculations for estimating atomic electronegativities and hardnesses. At present, the numerical results are conform with a Mulliken population analysis on STO-3G wavefunctions, but there is no reason why other more sophistieated approaches could not be used. Its simplicity forms a powerful tool for the experimental chemist, who is advised to include the environment into the models, avoiding isolated-atom approaches whenever possible. [Pg.225]


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See also in sourсe #XX -- [ Pg.167 ]




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