Grain phases

Fused-cast refractory is very dense but may contain a system of closed pores and large, highly oriented grains may exist in a particular casting. The size and distribution of the pore and grain phases must be controlled. 

The characterisation of materials is a central necessity of modern materials science. Effectively, it signifies making precise distinctions between different specimens of what is nominally the same material. The concept covers qualitative and quantitative analysis of chemical composition and its variation between phases the examination of the spatial distribution of grains, phases and of minor constituents the crystal structures present and the extent, nature and distribution of structural imperfections (including the stereological analysis outlined in Chapter 5). 

Recently, it has been shown [1071] that CoC204 2 H20 exists in two crystalline modifications, a and 3. Taskinen et al. [1072] prepared anhydrous cobalt oxalate of different particle sizes by dehydration of the (3 (coarser grained) phase and the a/(3 mixture (finer grained). The coarser grained preparation decomposed at 590—700 K with a sigmoid a—time curve fitted by the Avrami—Erofe ev equation [eqn. (6), n = 2] and below and above 625 K, E values were 150 and 57 kJ mole-1, respectively. Reaction of the fine preparation obeyed eqn. (6) (n = 3) and below and above 665 K, values of E were 120 and 59 kJ mole-1, respectively. Catalytic properties of the products of decomposition of cobalt oxalate have been investigated [1073]. 

Table 1 of a paper by Murr (2) lists problems and/or concerns related to specific interface materials and specific components of SECS. In Table 2 of the same work, he related topical study areas and/or research problems to S/S, S/L, S/G, L/L, and L/G interfaces. It is also useful to divide interface science into specific topical areas of study and consider how these will apply to interfaces in solar materials. These study areas are thin films grain, phase, and interfacial boundaries oxidation and corrosion adhesion semiconductors surface processes, chemisorption, and catalysis abrasion and erosion photon-assisted surface reactions and photoelectrochemistry and interface characterization methods. The actual or potential solar applications, research issues and/or concerns, and needs and opportunities are presented in the proceedings of a recent Workshop (4) and summarized in a recent review (3). 

Forsterite Possibly the most common coarse-grained phase present in all carbonaceous and unequilibrated ordinary chondrites, as well as a minor phase in enstatite chondrites and achondrites, is olivine ((Mg,Fe)2Si04). Most olivine contains significant Fe and does not show CL however a small fraction of the olivine is Mg-rich (forsterite) and shows brilliant CL. This same phase is present in... 

Toughening of the ceramic matrix (phase A) by whiskers or whiskerlike grains (phase B) produced in situ during densification ... 

Sample Flaky crust Dense crust underneath the flaky crust From points straddled between a crust and y-grain surface and from points straddled between sintering agents and a grain surface From points in y-grain phase but not deeper than 10 fan... 

Smith CS (1948) Grains, phases, and interfaces—an interpretation of microstructure. Trans Am Inst Min Metall Eng 175 15-51... 

Smith, C. S., Grains, phases and interfaces an interpretation of microstructure, Trans., AIME, 175, 15-51, 1948. 

Sarpoolaky H, Zhang S, Argent BB, Lee WE. Influence of grain phase on slag corrosion of low-cement castable refractories. J Am Ceram Soc 2001 84(2) 426-434. 

Fig. 5.34 The morphology of an inclusion as a function of the interfacial tension between the grain phase and the phase in the triple-grain junction. It can be characterized by rnesms of the dihedral angle. This is defined by the internal angle of the tangents to the a-0 boimdaries at the point of intersection and varies between 180 and 0 (cf also Fig. 5.33c). Diagrams a to f illustrate the characteristic morphologies corresponding to angles of 180 (a), 135° (b), 90° (c), 60° (d), 30 (e) and 0° (f). Prom Ref [165].

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