Shapes tetragonal

S-Sy forms block-shaped, tetragonal-bipyramidal and sarcophagus-hke single crystals of the monoclinic space group P2iln-C2] [20, 21,71]. 

Figure 4.6 Transmission electron micrograph (TEM) showing spindle-shaped tetragonal zir-conia precipitates within a monoclinic zirconia matrix phase in Mg-partially stabilised zirco-nia (Birkby and Stevens, 1996). ( With permission by Trans Tech Publ., Millersville, DA, USA.)...

Figure 7.18 Transmission electron microscopy image showing spindle-shaped tetragonal zirconia precipitates within a monoclinic zirconia matrix phase in...

Nucleation and the growth of spindle-shaped tetragonal particles occur that are stable against transformation, even at room temperature. The metastable... 

Polymorphism. Many crystalline polyolefins, particularly polymers of a-olefins with linear alkyl groups, can exist in several polymorphic modifications. The type of polymorph depends on crystallisa tion conditions. Isotactic PB can exist in five crystal forms form I (twinned hexagonal), form II (tetragonal), form III (orthorhombic), form P (untwinned hexagonal), and form IP (37—39). The crystal stmctures and thermal parameters of the first three forms are given in Table 3. Form II is formed when a PB resin crystallises from the melt. Over time, it is spontaneously transformed into the thermodynamically stable form I at room temperature, the transition takes about one week to complete. Forms P, IP, and III of PB are rare they can be formed when the polymer crystallises from solution at low temperature or under pressure (38). Syndiotactic PB exists in two crystalline forms, I and II (35). Form I comes into shape during crystallisation from the melt (very slow process) and form II is produced by stretching form-1 crystalline specimens (35). 

In order to illustrate the general applicability of the methodology we have extended our approach to other large zeolite crystals, such as SAPO-34, SAPO-5 and ZSM-5. Our study on the rhombic SAPO-34 crystals reveals a four-pointed star fluorescence pattern at 445 K, which is transformed into a square-shaped feature at 550 K. This is illustrated in Figure 4a. Confocal fluorescence slices, summarized in Figures 4b-d, recorded at different temperatures show the cubical pattern, which proceed from the exterior of the crystal inwards. Both observations are consistent with a model which involves six components of equal tetragonal pyramids as illustrated in Figure 3b. 

In order to answer this question, it is convenient to choose as a starting point the tetragonally shaped FeS2—m type cell, as defined in (iii) on p. 86. An orthorhombic deformation of this cell in fine with the experimental data would require an increase of a and/or a decrease of c according to... 

White tetragonal crystal density 4.09g/cm3 melts at 1100°C slightly soluble in water insoluble in ethanol and ether dissolves in dilute hydrofluoric acid. Tetrahydrate crystals are hexagonal shape density 2.20g/cm3 decomposes at 100°C. 

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