Crystal thin plates

Figure H.4. The crystals are manipulated by scooping them up with a small loop of nylon that is glued to the end of a pin. Surface tension firom the liquid will hold the crystal in the loop, but the crystal can also be held by using a loop that is smaller in size than the crystal of interest. This technique will work particularly well with fragile crystals, thin plates for example, that would normally fall apart in a capillary mount. Once the crystal is frozen, it is placed on an axis in line of both an X-ray source and a stream of nitrogen set to about 100,000to keep the crystal frozen. The crystal is rotated in increments during the data collection procedure to collect a full data set (typically one or two degrees per frame, depending on the resolution limits, mosaicity of the crystal, unit cell lengths, etc.).

Polymers crystallize in the form of thin plates or lamellae. The thickness of each of these lamellae is on the order of 10 nm. 

Theories of the oxidation of tantalum in the presence of suboxide have been developed by Stringer. By means of single-crystal studies he has been able to show that a rate anisotropy stems from the orientation of the suboxide which is precipitated in the form of thin plates. Their influence on the oxidation rate is least when they lie parallel to the metal interface, since the stresses set up by their oxidation to the pentoxide are most easily accommodated. By contrast, when the plates are at 45° to the surface, complex stresses are established which create characteristic chevron markings and cracks in the oxide. The cracks in this case follow lines of pores generated by oxidation of the plates. This behaviour is also found with niobium, but surprisingly, these pores are not formed when Ta-Nb alloys are oxidised, and the rate anisotropy disappears. However, the rate remains linear it seems that this is another case in which molecular oxygen travels by sub-microscopic routes. 

Isothermal a—time curves for the decomposition of U02(CH3C02)2 in air (513—573 K) [1018] showed two approximately linear regions, 0.0 < a < 0.2 and 0.2 < a < 0.9, for which the values of E were 107 and 165 kJ mole-1, respectively. In nitrogen, the earlier portion of the curve was not linear and E = 151 kJ mole-1 for the later interval. The zero-order kinetic behaviour was explained by growth of nuclei in thin, plate-like crystals, which were shown by microscopic and surface area measurements to fragment when a > 0.85. The proposed initial step in the decomposition was fission of bonds between the U02+ and the (OCO CH3) species [1018]. 

Dobutamine hydrochloride generally crystallizes in a random manner usually from an oil (1). This results in a nondescript crystalline formation. In only few cases does the drug exhibit any crystalline habit of interest. Upon careful and patient crystallization small thin plates and/ or small needles are formed. 

TeF4 dissolves in excess SbF by warming to 100°C. From the white residue, after removal of the excess SbF5 under vacuum at room temperature, two types of crystals could be grown. The bulk of the material consisted of very thin plates, unsuitable for crystallographic investiga-... 

In the following we shall describe the crystals as if they were spheres with the volumes of the actual crystals. This will facilitate the calculation considerably. In this way each particle is ascribed a well-defined radius even if it is not spherical. The approximation of spheres will be sufficient for our purposes unless the particles are needles, thin plates or similar extremely non-spherical objects. 

The best formed plate textures are found in crystals with a layer lattice, and generally in all crystals having the form of thin plates. Diffraction pattern (Fig.7) indicates a texture of this type, and was obtained from crystals in the shape of thin hexagonal plates. The specific role of the oblique-texture type electron diffraction patterns have in the study of clay minerals having layer structures (B.B.Zviagin, 1964, 1967). 

Crystalline clumps in suspension are ultra-sonicated into thin plates/fragments suitable for TEM investigation [10], but such ultra-sonication may damage the polymer single crystals. 

Figure 2.30 View showing 12-ring pockets thought to be present at the surface of MWW samples which crystallize as very thin plates.

FeOOH precipitates as platy crystals. When formed by fast oxidation of Fe(OH)2 at pH 12 well formed hexagonal plates result, whereas simultaneous precipitation/oxi-dation gives thin plates which are often rolled up (Feitknecht, 1959). Feroxyhyte (5 -FeOOH) produced by rapid oxidation (e.g. with H2O2) of FeQ2 solution at pH 8 also forms thin platy crystals around 100 nm in size (Fig. 4.27, upper). As the pH is lowered, the crystals become smaller and develop a grassy appearance (Carlson Schwertmann, 1980). Natural feroxyhyte from the Clara Mine in the Black Forest occurred as vermiform aggregates (Fig. 4.27, lower) (Walenta, 1997). 

Later on, advantage was taken of the delicate equilibrium of mono- and divalent ions needed for the growth of halobacteria. Crystals then grew at the minimum concentration of salts needed for storage without activity loss. They appeared as thin plates with dimensions of about 0.4 x 0.4 x 0.1 mm at 19 °C, but tended to fonn multilayer aggreptes (Fig. 6). Their X-ray diffraction patterns extended to about 13 A resolution. 

Piezoelectric microbalance The piezoelectric microbalance is a resonant frequency device. The piezoelectric effect is the development of a charge on some crystals such as quartz when a stress is applied the stress may be mechanical (e.g., added weight) or electrical. Such crystals may be used as part of a resonance circuit to provide very stable, narrow-band frequencies the quartz crystal is plated on two sides with a thin conducting layer and leads are connected to the resonance circuit so the crystal replaces an LC network. The obtained frequency of vibration (pu) depends on a number of parameters of the crystal but is usually 5-10 MHz. However, if a mass (Am) becomes attached to one side of the crystal, it changes the resonant frequency by an amount At , such that... 

Composition. Crystals deposited from ethanol solution as well-formed thin plates. The fatty acid content of the crystals is given in Table I. For all chain lengths the acid content approximates closely that required for 1 to 1 stoichiometry. This is also the case for most of the acid-soaps prepared by the petroleum ether route the low values of titratable acid in some instances are ascribable to the presence of free soap. 

An alternative hypothesis, developed from studies of the synthesis of Linde A zeolite carried out by Kerr (5) and Ciric (6), pointed to growth occurring from solution. The gel was believed to be at least partially dissolved in solution, forming active aluminosilicate species as well as silicate and aluminate ions. These species linked to form the basic building blocks of the zeolite structure and returned to the solid phase. Aiello et al. (7) followed the synthesis from a highly alkaline clear aluminosilicate solution by electron microscopy, electron diffraction, and x-ray diffraction. These authors observed the formation of thin plates (lamellae) of amorphous aluminosilicates prior to actual crystal formation. 

In a typical quartz gage, a thin plate (lamina) is cut from a crystal in such a man-net that the flat, parallel faces of lamina are perpendicular to one of the three electric axes of quartz. When subjected to a compressional force transmitted by means of a piston (or a diaphragm), the lamina. presses against an anvil and as result of this action, very weak electric charges of opposite sign are devel-... 

E.Berglundprepared thin plates of calcium amidos phonate,Ca(NH2S03)2.4H20, which were very soluble in water also prismatic crystals of strontium amidosul phonate, Sr(NH2S03)2.4H20, more soluble than the barium salt and acicular... 

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