Boron wheel

FIGURE 10.6 (See color insert following page 202.) Optimized geometries of planar boron wheels containing a planar hypercoordinate group 14 element. 

Stabilizing these molecules. These results are in complete agreement with the conclusions drawn from the MO and B analysis, showing that extensive delocalization is a key factor for the stabilization of the boron wheels containing a hypercoordinate group 14 element. 

Uses. Apphcations for boron carbide relate either to its hardness or its high neutron absorptivity ( B isotope). Hot-pressed boron carbide finds use as wear parts, sandblast no22les, seals, and ceramic armor plates but in spite of its hardness, it finds Httie use as an abrasive. However, this property makes it particulady usehil for dressing grinding wheels. 

The greatest use of cubic boron nitride is as an abrasive under the name Bora2on, in the form of small crystals, 1—500 p.m in si2e. Usually these crystals are incorporated in abrasive wheels and used to grind hard ferrous and nickel-based alloys, ranging from high speed steel tools and chilled cast-iron to gas turbine parts. The extreme hardness of the crystals and their resistance to attack by air and hot metal make the wheels very durable, and close tolerances can be maintained on the workpieces. 

Cubed compound, in PVC siding manufacture, 25 685 Cube lattice, 8 114t Cubic boron nitride, 1 8 4 654 grinding wheels, 1 21 hardness in various scales, l 3t physical properties of, 4 653t Cubic close-packed (CCP) structure, of spinel ferrites, 11 60 Cubic ferrites, 11 55-57 Cubic geometry, for metal coordination numbers, 7 574, 575t. See also Cubic structure Cubic symmetry Cubic silsesquioxanes (CSS), 13 539 Cubic structure, of ferroelectric crystals, 11 94-95, 96 Cubic symmetry, 8 114t Cubitron sol-gel abrasives, 1 7 Cucurbituril inclusion compounds,... 

Boron carbide is used in sandblast nozzles, ceramic armor plates and abrasive powder grinding wheels. Because of its high neutron absorptivity and... 

Superabrasive wheels include diamond wheels and cubic boron nitride (CBN wheels. 

Boron carbide is a relatively inexpensive hard material, which is used for its mechanical properties of strength and extreme hardness in armor-plates for body protection, in sandblast nozzles, and as an abrasive for grinding and cutoff wheels. In nuclear plants, boron carbide is used as the neutron absorbing material of the control rods. 

SAFETY PROFILE Poison by intraperitoneal route. When heated to decomposition it emits very toxic fumes of F", K2O, and BOx. Used in sand casting of aluminum and magnesium, grinding, and in resinoid grinding wheels. See also FLUORIDES and BORON COMPOUNDS. 

Notice the three single bonds around the central boron atom. Like three spokes of a wheel, these shared pairs of electrons extend from the central boron atom. The three F atoms, each of which has three unshared pairs, will repel each other and will be at a maximum distance apart. This molecular shape is known as trigonal planar, as shown in Figure 16. 

The main source of boron is a complex compound of boron called borax. About half of the world supply of borax comes from a large deposit in California s Mojave Desert. Borax is used as a cleaning agent and as fireproof insulation. Another compound of boron, boric acid, is used as a disinfectant and as an eye wash. A form of boron nitride is the second hardest known material only diamond is harder. These materials are classified as superabrasives. They are used in grinding wheels, which shape manufactured parts and tools. 

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