Composition plane

One of the most significant recent aircraft is the Rutan Voyager, an all-composite plane in Figure 1-42 which was flown around the world non-stop in 1989. Burt Rutan of the Rutan Aircraft Factory created a seemingly endless line of all-composite aircraft in the 1980s and 1990s. 

Twins are intergrown crystals such that the crystallographic directions in one part are related to those in another part by reflection, rotation, or inversion through a center of symmetry across a twin boundary. Twinned crystals are often prized mineralogical specimens. When twins are in contact across a well-defined plane (which is not always so), the boundary is generally called the composition plane. The only twins that are considered here will be reflection twins, where the two related parts of the crystal are mirror images (Fig. 3.22). The mirror plane that relates the two components is called the twin plane. This is frequently, but not always, identical to the plane along which the two mirror-related parts of the crystal join, that is, the composition plane. Repeated parallel composition planes make up a polysynthetic twin (Fig. 3.23). 

Let us now treat compositional relations in the ternary system Di-An-Ab. Figure 7.14A shows the projection of the liquidus surface of the system onto the compositional plane the locations of cotectic line E -E" and of the isotherms are based on the experiments of Bowen (1913), Osborn and Tait (1952), and Schairer and Yoder (1960). 

Point in the isobaric temperature-composition plane for a binary mixture where the compositions of all coexisting phases become identical. 

In close-packed stmctures or fee crystals, twinning is introduced by stacking faults. In this case, the excess energy at the twin plane ( = composition plane) is small, and so neither generation nor concentration of dislocations is required. In... 

Penetration twins have an irregular composition plane, and the twin plane and the composition plane are not the same. As a representative example, the 111 twin of fluorite, CaF, is shown in Fig. 7.8. 

As already explained in Section 7.2, the re-entrant corner effect in its original sense can be expected only when two individuals are perfect crystals, containing no dislocations either in the individual crystals or in the composition plane. In real crystals, the pseudo re-entrant corner effect, by the mediation of dislocations, creates changes in the morphology of the twinned crystal. 

If two individuals conjugate on an r or a z face, a nucleus of a Japanese twin with 1122 as the composition plane is formed. This indicates that a Japanese twin is not a penetration twin (i.e. not the upper half of an X-shape), but a contact twin (i.e. the upper half of a Y-shape). Horizontal banding in geode agate (see Section 10.9) appears through grain size variation due to gravitational sedimentation, and con-... 

After a series of experiments has been performed as a function of temperature, we can obtain the relation between the composition, equilibrium oxygen pressure, and temperature as shown in Fig. 1.2 (the curves for different temperature never cross on the F,-composition plane). In this case, only phase (I) and (II) are assumed to be existent. Phase (I) is known as a... 

Crystals grown by this technique are in a form called butterfly twins. The twins consist of two isosceles right triangles with a common hypotenuse.2 Normally the composition plane is (111), the crystal faces are 100 and the angle between the wings is approximately 38°. 

Abstract—Pseudo-twinning and mechanical twinning have been observed in a transmission electron microscopy study of TiMNi47Fe3 and Ti49Ni5i alloys which have the B2(CsCI) structure. Observation of twinning in ordered alloys is rare and this is the first observation of twinning reported in a B2 structure. The twin planes are the 112 and 114 planes. For 112 pseudo-twins, the composition plane is not the twin plane and the pseudo-twin does not have the B2 structure. For 114 mechanical twins, the composition plane is the twin plane and the twin does have the B2 structure. It is shown that a shear on the 114 plane plus a shuffle of the atoms results in the ordered B2 structure in the twinned region. 

Figure 1. A nonrelativistic window of the temperature—composition plane, showing electron density (n) and temperature (T). Normal conditions (on earth) for semiconductors and elemental metals and conditions on the Sun, Jupiter, and the White Dwarf are shown. Experimental methods in A, B, C, and D are Tokamak, glow-discharge, laser fusion, and degenerate strongly coupled plasma, respectively. Wigner—Seitz radii, rs, are also shown (adapted from Redmei4).

When a single crystal in the paraelectric state transforms to a ferroelectric state of lower symmetry, stresses induced by dimensional changes can be relieved by domain twinning. For the tetragonal, pseudocubic BaTiOa, there are two possible modes of twinning 180° twins and 90° twins, with (100) and (101) respectively as composition planes. For the highly elongated structures considered in this paper, it may be expected that 180° twins could have (100)ss, (010)ss or (001)Ss as composition planes, but that 90° twins would be restricted to (110)ss as composition plane. 

S Fiber volume fraction in load- E Young s modulus for composite Plane strain Young s modulus... 

Twinning is common in wollastonite (Deer, Howie, and Zussman 1963 Muller and Wenk 1975). The twin axis is 1010] and the composition plane (100). Figure 8.7(c) shows a twin lamella (one unit cell wide) in an untwinned matrix. To eliminate very severe misfit at the composition plane, a relative displacement of R = [OlOJ is necessary. Comparison of Figures... 

Note also that the twin composition planes on each side of the twin lamella are in the center of parawollastonite cells. 

Sanidine is monoclinic (space group C2/m), and there is complete disorder in the occupation of the tetrahedral (T) sites by the A1 and Si atoms. Over geological time, ordering takes place. In low (or maximum) micro-cline, the ordering is complete (all A1 in TiO sites), and the symmetry is reduced to triclinic (CT). There are four main orientational variants in this structure two orientations related by the albite twin law (rotation of 180° about b ) and two orientations related by the pericline twin law (rotation of 180° about b). The composition planes of these two twins are, respectively, (010) and the rhombic section which is parallel to b and approximately normal to (001). Thus, the characteristic cross-hatched pattern observed in (001) sections between crossed-polarizers in the optical microscope has, for many years, been simply interpreted as intersecting sets of albite and pericline twin lamellae formed at the monoclinic-to-triclinic transformation. However, TEM observations indicate that this model is too simple. Because these observations, collectively, also constitute an excellent example of the application of the principal modes of operation of TEM to a specific mineralogical problem, we discuss them in some detail. 

Consider steady one-dimensional beat conduction in a composite plane wall consisting of iwo layers A and B in perfect contact at the interface. The wall involves no heat generation. The nodal network of the medium consisl.s of nodes 0, 1 (at Ihe interface), and 2 with a uniform nodal spacing of A.x. Using the energy balance approach, obtain Ihe finite difference formulation of this problem for the case of insulation at the left... 

Consider one dimensional transient heat conduction in a composite plane wall that consists of two layers A and ft with perfect contact at the interface. The wall involves no heat... 

This spinodal can also be transformed to a phase diagram in the temperature-composition plane by using the experimentally determined X T) via Eq. (4.31) ... 

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