Boundary phenomena

Fig. 3. An overview of atomistic mechanisms involved in electroceramic components and the corresponding uses (a) ferroelectric domains capacitors and piezoelectrics, PTC thermistors (b) electronic conduction NTC thermistor (c) insulators and substrates (d) surface conduction humidity sensors (e) ferrimagnetic domains ferrite hard and soft magnets, magnetic tape (f) metal—semiconductor transition critical temperature NTC thermistor (g) ionic conduction gas sensors and batteries and (h) grain boundary phenomena varistors, boundary layer capacitors, PTC thermistors.

L. M. Levinson, ed., "Grain Boundary Phenomena In Electronic Ceramics," vny dvances in Ceramics Vol. 1, American Ceramic Society, Columbus, Ohio, 1981. 

Kingery, W.D. (1981) in Grain Boundary Phenomena in Electronic Ceramics, ed. Levinson, L.M. (American Ceramic Society, Columbus, OH) p. 1. 

A book edited by Levinson (1981) treated grain-boundary phenomena in electroceramics in depth, including the band theory required to explain the effects. It includes a splendid overview of such phenomena in general by W.D. Kingery, whom we have already met in Chapter I, as well as an overview of varistor developments by the originator, Matsuoka. The book marks a major shift in concern by the community of ceramic researchers, away from topics like porcelain (which is discussed in Chapter 9) Kingery played a major role in bringing this about. 

Sakuma, T., Sheppard, L.M., and Ikuhara, Y., (eds) (2000), Grain Boundary Engineering in Ceramics From Grain Boundary Phenomena to Grain Boundary Quantum Structures, Ceramic Transactions, 118, Westerville, OH, The American Ceramic Society. 

Processes occurring at a crystal surface refer to any boundary phenomena within a zone of unspecified and often indeterminate thickness. Many chemical changes. 

Some authors (7, ) have used measured parameters of solute and solvent transport for calculation of membrane pore size distributions. Difficulties associated with this approach are of both experimental and theoretical nature. The experiments need to be carried out under conditions that minimize or eliminate effects of boundary phenomena (polarization) and of solute adsorption (fouling) on the measured coefficients. This is rarely done. An even more serious obstacle in this approach is the absence of quantitative and valid relations between measured transport parameters and the size parameters of a "representative pore."... 

C.AJ. Fisher and H. Matsubara, Molecular dynamics investigations of grain boundary phenomena in cubic zirconia, Comput. Mater. Sci. 14, 177-184 (1999). 

Kingery, W. D. (1974). Plausible concepts necessary and sufficient for interpretation of ceramic grain-boundary phenomena I, Grain boundary characteristics, structure and electrostatic potential II, Solute segregation, grain-boundary diffusion and general discussion. Journal of the American Ceramic Society, 57, 1-8 and 74-83. 

Den Broeder, F. J. A. Franken, P. E. C. (1981). The microstructure of sintered strontium hexaferrite with silica addition investigated by ESCA and TEM. In Advances in Ceramics, Vol. 1 Grain Boundary Phenomena in Electronic Ceramics. Eds L. M. Levinson and D. C. Hill. American Ceramic Society, Ohio, pp. 494-501. 

The final characteristics of the interface can continue to be driven as additional monolayers are added. Strain fields due to lattice mismatch and grain boundary phenomena can play an important role. Usually, the interface reaches a stable configuration within 3 to 10 monolayers for most metals on semiconductors. Interfaces are often metastable, however, and the interdiffusion is accelerated at increased temperature or under biased conditions. The application of core level photoemission to this problem confirmed what had already been deduced with Auger spectroscopy, but on a finer dimensional scale. An overriding fact of metal-semiconductor interfaces is the intrinsic aspects of interfadal interdiffusion and interaction. These two aspects of the chemistry often tend to overwhelm issues that might be deduced from the clean separate surfaces. The interdiffusion can result in interface layers with radically different characteristics from the supposed components. 

As in their solutions perfect (or nearly perfect) thermod5mamic equilibrium exists, it seems at first glance, that general considerations on phase boundary phenomena, so extensively studied and applied in Volume I, are of no use at all for the contents of the whole of Volume II. 

Though the generalisation from solutions to all study objects will prove to be inadmissable, at least for the solutions themselves the science of phase boundary phenomena has no importance. It is therefore all the more important that other chapters of general physical chemistry should be consulted, vis ., those dealing with solutions, association and, as will be seen below, with other subjects in which equilibria are studied. 

In the non-equilibrum systems c., and presumably also in rf., where the mutual contact area of the phases is very great, phase boundary phenomena do take part in determining their behaviour, and the chapter of physical chemistry rejected for a., b, and e, now gains an importance comparable with those already mentioned. 

In the older literature cases of partial miscibility in particular of solutions of protamines (a class of proteins) have been described without this causing any surprise Other cases of separation into two liquid layers were gradually discovered, but they only began to attract the attention of investigators when the opinion became more and more general that the behaviour of all Colloids depended on boundary phenomena (p. 1 Ch. I la). According to this view a sol had always to be considered as a two-phase system, in which the one phase (the disperse phase) is very finely divided in the bosom of the second (the dispersion medium, the continuous phase). 

In January of 1909, Haber and Klemensiewicz ( ) presented a paper before the Karlsruhe Chemical Society which was published later in the year in the Zeitschrift fur physikalische Chemie under the title "On Electrical Forces at Phase Boundaries." It is important to note that even though Haber is remembered as a physical chemist, in this study of phase boundary potentials he also had an interest in physiology. He felt that phase boundary phenomena might help explain the action of muscles. In this work he studied the systems glass I water, benzene water, toluene I water, and metaxylene water. 

Grain boundary phenomena Varistors, BLCs (Zn,Co)0-Bi203... 

Feldberg SW (1972) Digital simulation of electrochemical boundary phenomena multiple electron transfer and adsorption. 

The SEI on the HOPG and SLX electrodes can be described as non-homogeneous. The true lateral size of the microdomains is about or less than 1 micron. Since the SEI consists of a mosaic of heteropoly-microphases, the contribution of grain boundaries must be considered. The equivalent circuit of the SEI is extremely complex and should be represented by a very large number of series and parallel distributions of RC elements reflecting bulk ionic conductivity and grain-boundary phenomena aside from the Warburg element. 

Feldbetg SW (1972) Digital simulation of electrochemical surface boundary phenomena. Multiple electron transfer and adsorption. In Mattson J, Mark HB Jr, MacDonald HC Jr (eds) Computers in Chemistry and Instrumentation, vol 2. Marcel Dekker, New York, pp 185-215... 

The existence of an additional relaxation mechanism has been noted by several authors for the heterogeneous system of block and graft copolymers and been assigned to a type of grain-boundary phenomena(20), i.e., interfacial... 

Fig. 2 shows the pellet boundary phenomena of narrow MWD PS-118. At the lower molding temperatures, such as shown in Fig. 2a, gross distortions and whole pellets can be seen. At one point (Fig. 2b), an abrupt change in sample distortion is observed for the narrow temperature range between 155.7 and 157.1°C. All samples molded below 157.UC showed some, if not extensive, pellet boundary reformation on reheat while those molded above 155.7 C did not. 

In colloid solutions such as those of metals, AsgS, AgJ and others the colloid particle consists oJ a comparatively large number of molecules and may be considered as a separate phase. The treatment adopted for this type of system is based on our knowledge of phase-boundary phenomena. On the other hand, the colloid solutions... 

---