Unusual tubes emerge from boron nitride.Chemists seeking an alternative method for making boron nitride Boron nitride (BN) is a binary chemical compound, consisting of equal proportions of boron and nitrogen. The empirical formula is therefore BN. Boron nitride is isoelectronic to the elemental forms of carbon and isomorphism occurs between the two species. - a substance used to create hard, diamond-like materials, face powders, and fibers for composite materials - have discovered a new form of the material: microscopic tubes. "At this point, I think the tubular form is a curiosity," says Sheldon G. Shore, one of the group of chemists at Ohio State University Ohio State University, main campus at Columbus; land-grant and state supported; coeducational; chartered 1870, opened 1873 as Ohio Agricultural and Mechanical College, renamed 1878. There are also campuses at Lima, Mansfield, Marion, and Newark. in Columbus who found the tubules. "But it does suggest the possibility that carbon is not the only element that can be made into tubes." Scientists aiming ultimately to make microscopically thin wires succeeded recently in making superstrong nanometer-size tubes from carbon (SN: 4/3/93, p. 214). Boron boron (bōr`ŏn) [New Gr. from borax], chemical element; symbol B; at. no. 5; at. wt. 10.81; m.p. about 2,300°C;; sublimation point about 2,550°C;; sp. gr. 2.3 at 25°C;; valence +3. compounds often resemble those made of carbon (SN: 6/20/92, p.406). Shore and his co-workers were surprised to see these boron nitride tubes, for two reasons. First, the tubes emerged out of boron nitride's amorphous phase in an ordered, parallel alignment. Second, the boron nitride tubes were about 100 times larger than their carbon counterparts and, unlike them, apparently formed without the aid of a catalyst. The formation mechanism of these unusual tubes, which lack the layered crystalline structure of graphite carbon, continues to puzzle the researchers, Shore says. In the April 30 SCIENCE, Shore and his colleagues describe how they synthesized amorphous boron nitride with a new procedure involving an explosive reaction between B-trichloroborazine and cesium cesium (sē`zēəm) [Lat.,=bluish gray], a metallic chemical element; symbol Cs; at. no. 55; at. wt. 132.9054; m.p. 28.4°C;; b.p. 669.3°C;; sp. gr. 1.873 at 20°C;; valence +1. metal at 125 degrees C. They then heated this material to 1,100 degrees C for 24 hours Adv. 1. for 24 hours - without stopping; "she worked around the clock" around the clock, round the clock . The tubes were revealed by scanning electron microscopy electron microscopy Technique that allows examination of samples too small to be seen with a light microscope. Electron beams have much smaller wavelengths than visible light and hence higher resolving power. (SEM). Robert T. Paine of the University of New Mexico The University of New Mexico (UNM) is a public university in Albuquerque, New Mexico. It was founded in 1889. It also offers multiple bachelor's, master's, doctoral, and professional degree programs in all areas of the arts, sciences, and engineering. in Albuquerque says the team made a "fundamentally interesting observation." But, he adds, "This is an unusual form of the material, and its utility remains to be seen." Indeed, Shore's group now intends to study the tubes' physical properties. They also plan to try heating the amorphous boron nitride further--to 1,400 degrees C-to see if they can create highly ordered, graphite-like tubes. |
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