Boron microstructure

The microstructure of a pure B4C layer of three-layered B4C/B4C-30wt%SiC laminate with 4% porosity is presented in Fig. 7.20. The three-layered B4C/ B4C-30wt%SiC tiles tested as armor material had the same microstructure and porosity level as the material shown in Fig. 7.20. As one can see, the porosity at the grain boundary of the ceramics might be a reason why threelayered laminates have not outperformed the dense monolithic boron carbide tiles. A different set of ballistic experiments are required in which fully... 

These novel microstructures have extraordinary combination of physical and chemical properties [11-13], for this reason they become an important scheme of actually science work. One example of such nanomaterials is boron carbonitride (BNC) with graphite-like structure. Based on theoretical calculations, the existence of nanotube structures of BN was predicted in 1994, which was soon verified by the first synthesis of BN nanotubes in 1995. 

Initial explanations of the extraordinary high-temperature stability of precursor-derived Si-B-C-N ceramics were presented previously by Jalowiecki et al. 13 The authors investigated the microstructure of boron-doped silicon carbonitride composites by HR-TEM and found... 

For a given type and orientation, the etch rate of silicon in alkaline solutions is largely independent of doping concentration up to a concentration of about 1019 cm-3 [33, 80]. At a doping level of about 2 x 1019 cm 3, the etch rate of boron doped silicon drastically decreases with increasing dopant concentration [33, 86,144]. Reduction by as much as 3 orders of magnitude can be obtained by varying the boron concentration from about 1019 to above 102° cm-3. This feature has been widely used as an etch-stop technique for the fabrication of silicon microstructures. 

T. D. Claar, W. B. Johnson, C. A. Andersson, and G. H. Schiroky, Microstructure and properties of platelet reinforced ceramics formed by the directed reaction of zirconium with boron carbide. Ceram. Eng. Sci. Proc. 10(7-8) 599-609 (1989). 

E. Breval and W. B. Johnson, Microstructure of platelet reinforced ceramic prepared by the directed metal reaction of zirconium with boron carbide. J. Amer. Ceram. Soc. 75(8), 2139-2145 (1992). 

Figure 4 shows the microstructures of the specimen containing 90mol% boron before and after annealing at 1673K for 0.5hr. In Fig.4(a) of the as-melted sample, the EPMA... 

BORON DISTRIBUTION AND MICROSTRUCTURE IN MOLYBDENUM-BORON ALLOYS... 

Boron distribution and microstructure in molybdenum-boron alloys 349... 

Specimen surface was polished electrochemically by mixed solution of sulfuric acid and ethyl alcohol (1 3). After polishing, the surface of the specimen was adhered by a film of nitric acid cellulose using acetic acid methyl solution. Specimens were then sealed in the polyethylene sheet and irradiated for 43.2 Ks (12 h) by the atomic reactor in Rikkyo University (thermal neutron = 1.1 x 1010 n/cm2 s) or JRR-4 in JAERI (1.5 x 109 n/cm2 s). After cooling down for 0.61 Ms (7days), the film of nitric acid cellulose was striped off from specimen. Boron distribution in the specimen corresponds to particle-tracks produced on the film of nitric acid cellulose by the interaction between thermal neutron and boron (10B (n,a) 7Li). Using 2.5N-NaOH solution at 303 K, particle-tracks by a-rays produced by thermal neutron with boron were etched for 2.7 ks. Then etched films were washed for 10.8 ks in flowing water. We observed microstructure by optical microscopy and SEM. 

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