Beryllium, measurement

Electron Probe X-Ray Microanalysis (EPMA) is a spatially resolved, quantitative elemental analysis technique based on the generation of characteristic X rays by a focused beam of energetic electrons. EPMA is used to measure the concentrations of elements (beryllium to the actinides) at levels as low as 100 parts per million (ppm) and to determine lateral distributions by mapping. The modern EPMA instrument consists of several key components ... 

Staeking faults and sometimes proper polytypism are found in many inorganic compounds - to pick out just a few, zinc sulphide, zinc oxide, beryllium oxide. Interest in these faults arises from the present-day focus on electron theory of phase stability, and on eomputer simulation of lattice faults of all kinds investigators are attempting to relate staeking-fault concentration on various measurable character-isties of the compounds in question, such as ionicity , and thereby to cast light on the eleetronic strueture and phase stability of the two rival structures that give rise to the faults. 

For the neutron porosity measurement, fast neutrons are emitted from a 7.5-curie (Ci) americium-beryllium (Am-Be) source. The quantities of hydrogen in the formation, in the form of water or oil-filled porosity as well as crystallization water in the rock if any, primarily control the rate at which the neutrons slow down to epithermal and thermal energies. Neutrons are detected in near- and far-spacing detectors, located laterally above the source. Ratio processing is used for borehole compensation. 

Surface condition Machined, abraded and pickled surfaces all exhibit much the same behaviour in water, and after exposure of up to about one year at temperatures less than I00°C average attack measures 0 0025-0 0050mm/y. Almost always, however, corrosion of beryllium in water is accompanied by pitting and, on machined surfaces, pits of as much as 0-25mm have been observed in 0-0005M hydrogen peroxide at 85°C. Under similar conditions, annealed material has been found to be somewhat less resistant to attack than either machined or pickled surfaces. 

Dilute binary alloys of nickel with elements such as aluminium, beryllium and manganese which form more stable sulphides than does nickel, are more resistant to attack by sulphur than nickel itself. Pfeiffer measured the rate of attack in sulphur vapour (13 Pa) at 620°C. Values around 0- 15gm s were reported for Ni and Ni-0-5Fe, compared with about 0-07-0-1 gm s for dilute alloys with 0-05% Be, 0-5% Al or 1-5% Mn. In such alloys a parabolic rate law is obeyed the rate-determining factor is most probably the diffusion of nickel ions, which is impeded by the formation of very thin surface layers of the more stable sulphides of the solute elements. Iron additions have little effect on the resistance to attack of nickel as both metals have similar affinities for sulphur. Alloying with other elements, of which silver is an example, produced decreased resistance to sulphur attack. In the case of dilute chromium additions Mrowec reported that at low levels (<2%) rates of attack were increased, whereas at a level of 4% a reduction in the parabolic rate constant was observed. The increased rates were attributed to Wagner doping effects, while the reduction was believed to result from the... 

Procedure. Transfer the almost neutral sample solution of beryllium (containing 5 to 80jug of the element in a volume of about lOmL) to a 25 mL graduated flask, add 2.8 mL of 2.0M sodium hydroxide (or more if much aluminium is present), 5.0 mL of 0.64M boric acid solution, and 6.0 mL of the dye solution (see Note), dilute to the mark with distilled water, and mix well. Measure the transmittance at 520 nm, or with a green filter preferably using a 2 cm cell. 

Experimentally, Flynn (Ref 73a) has tested plastisol NC composite propints containing beryllium and triaminoguanidinium hydrazinium diazide in a closed bomb and measured the high specific impulses indicated in Table 23... 

It was concluded by Zachariasen [Norsk geol. Tidsskrift, 8, 189 (1925) Z. physik. Chem., 119, 201 (1926)] from the intensities of reflection of x-rays that beryllium oxide does not contain Be++ and O" ions. However, it has since been shown by Claassen [ibid., 124, 139 (1926)] and Zachariasen himself [Z. Physik, 40, 637 (1926)] that if the electron distribution of the ions is taken into account, the x-ray measurements are compatible with an ionic structure. 

Conroy and Perlow [235] have measured the Debye-Waller factor for W in the sodium tungsten bronze Nao.gWOs. They derived a value of/= 0.18 0.01 which corresponds to a zero-point vibrational amplitude of R = 0.044 A. This amplitude is small as compared to that of beryllium atoms in metallic beryllium (0.098 A) or to that of carbon atoms in diamond (0.064 A). The authors conclude that atoms substituting tungsten in bronze may well be expected to have a high recoilless fraction. 

Iversen et al, in their study of crystalline beryllium [32], were the first to make use of NUP distributions calculated by superposition of thermally-smeared spherical atoms. More recently, a superposition of thermally-smeared spherical atoms was used as NUP in model studies on noise-free structure factor amplitudes for crystalline silicon and beryllium by de Vries et al. [38]. The artefacts present in the densities computed with a uniform prior-prejudice distributions have been shown to disappear upon introduction of the NUP. No quantitative measure of the residual errors were given. 

We originally proposed NNM to be present in metallic beryllium [30] based on analysis of the X-ray diffraction data measured by Larsen and Hansen [24], Based on Fourier maps and elaborate multipole least-squares modeling, indisputable evidence... 

The theory described in the previous section is now applied to beryllium metal. Accurate low temperature data was taken from the paper of Larsen and Hansen [20]. (But note that in (20) I used the structure factors multiplied by 1000, as given in then-paper.) For the orthogonalisation, all nearest neighbours we included within the first shell. There were 12 atoms. A triple zeta basis set from Ref. [21] was used. There are 182 basis functions and 361 independent parameters in the wave function, whereas there are 58 experimental measurements. Figure 1 shows a plot of the x2 agreement statistic as a function of the parameter X for k = 0.2. Larger values of k caused... 

Techniques for the Direct Measurement of Natural Beryllium-10 and Carbon-14 with a Tandem Accelerator... 

The combination of toxic hazard and high price (itself in part due to the extra measures needed in production processes to ensure the workers safety) has been an effective brake on commercial development of beryllium chemistry. Where possible substitute, albeit less effective, materials are often used titanium as an alternate lightweight metal or carbon fiber composites, phosphor-bronzes in place of beryllium alloys, aluminum nitride in place of BeO (1). 

Carell and Olin (58) were the first to derive thermodynamic functions relating to beryllium hydrolysis. They determined the enthalpy and entropy of formation of the species Be2(OH)3+ and Be3(OH)3+. Subsequently, Mesmer and Baes determined the enthalpies for these two species from the temperature variation of the respective equilibrium constants. They also determined a value for the species Be5(OH) + (66). Ishiguro and Ohtaki measured the enthalpies of formation of Be2(OH)3+ and Be3(OH)3+ calorimetrically in solution in water and water/dioxan mixtures (99). The agreement between the values is satisfactory considering the fact that they were obtained with different chemical models and ionic media. 

Many of the results reported are of a dubious nature. For example, Perkins (219, 222) assumed that complexes of the type ML2 were formed and quoted log /32 values between 9.8 and 14.2. Not only was the possible formation of a simple complex of the type ML excluded (not to mention any other complexes), but the effects of hydrolysis (which, to be fair, were poorly understood at the time) were completely ignored. The high stability of amino acid complexes was put in doubt in successive publications (220, 229, 232, 233). It has even been suggested, on the basis of Raman spectra, that the amino group does not coordinate to the beryllium atom (232). Unfortunately the opposite conclusion was reached on the basis of IR measurements, namely that only the amino group was coordinated (234). 

The predictions of this model (normalized to meteoritic abundance for solar metallicity) are illustrated in Fig. 9.6 and compared with observational data for beryllium in stars, based on ground-based measurements of the near-UV Be II doublet A 3130. Assuming that surface Be can suffer some destruction in some of the metal-rich disk stars, there is fair agreement down to about 0.1 of solar abundance, but the secondary trend predicted at still lower metallicities is too steep. 

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