Tungsten core

Boron has a density of 2.34gcm (about 15% less than that of Al). Boron fibers with tungsten core have a density of 2.6gcm for a fiber of 100 p,m diameter. Its melting point is 2040 C and it has a thermal expansion coefficient of 4.86xlO- K- upto3l5 C. 

Flexible Kevlar body armor, even with dual pads and metal inserts, will not stop some high power rifle bullets. The three most difficult rounds to stop are tungsten cored 308 NATO and 223 NATO AP and the 7.52 Soviet AP Incendiary. 

The Pyrex thermal decomposition flask is shown in Fig. 291. The tungsten bus bars a, b and c (diameter of each 6 mm.) are arranged in a triangular pattern and sealed into the glass. The Ti deposits on drawn tungsten core wires (d, and d2), each 0.04 mm. thick and 400 mm. long. 

Boron Elemental boron may be grown over a tungsten core into long, relatively thick fibres that may be used as reinforcing material. The fibres are extremely stiff, but their very high cost rules them out for most applications outside ntiUtary aerospace projects. 

Figure 103. Boron fibers in an aluminum alloy, electrolytically etched, BF. The boron fibers have a bright tungsten core.

Pure boron (99.999 %) [20], as-manufactured (referred to as virgin") BF with tungsten core shielded [20,2/], virgin BF with tungsten core exposed [2/], and BF extracted from aluminum matrices (not specified if tungsten core exposed)... 

TEXTRON boron fiber with tungsten core 100 and 140 3600 400 2.57... 

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