Room-Temperature Mechanochemical Synthesis of W 2 B 5 Powders
- PDF / 774,419 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 87 Downloads / 247 Views
ION
TUNGSTEN borides have promising characteristics like a high melting point, high hardness values (>9 Mohs), high abrasion resistance, chemical inertness, magnetic properties, and metal-like electronic conductivity.[1] These characteristics have made tungsten borides interesting candidates for industrial applications at extreme environmental conditions, which demand abrasive, corrosion-resistant, and electrode materials.[1–8] Tungsten borides are resistant to thermal shock and are also good thermal conductors.[9] They are used in high-temperature applications such as crucibles and ingot molds for precision metallurgy.[9,10] Moreover, tungsten boride powders are used in the fabrication of various composite materials, including metal–boride alloys for fillers (borolites).[11] Currently, various kinds of tungsten borides such as W2B, WB, WB2, W2B5, WB4, and WB12 are known to exist in the W–B system.[1,5,12] Among these, W2B5 comes into prominence since it combines the high hardness (2700 kg/mm2) and modulus of elasticity (755 GPa) values with the low electrical resistivity (19 lX9cm) and density (13.1 g/cm3) values.[1,13] W2B5 phase has lately been used to improve the thermoelectric SELIM COS¸KUN, Postdoctoral Research Associate, is with the Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, U.K., and also with the Department of Metallurgy and Materials Engineering, Particulate Materials Laboratories, Istanbul Technical University, ITU Ayazaga Kampusu Maslak, 34469 Maslak, Istanbul, Turkey. Contact e-mail: [email protected] M. LU¨TFI O¨VEC¸OG˘LU, Professor, is with the Department of Metallurgy and Materials Engineering, Particulate Materials Laboratories, Istanbul Technical University. Manuscript submitted May 23, 2012. Article published online December 11, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
properties of B4C ceramics[3] and to improve the electrical conductivity, wear and oxidation resistance, flexural strength, and fracture toughness of carbon composites.[6,7] Recently, W2B5 has been used to increase the wear resistance of carbon composites against steel bearings.[14] Researchers are specifically interested in problems related to tungsten borides because their production is difficult owing to the use of high-temperature equipment and, in some degree, does not meet the practical needs simultaneously.[11] Tungsten borides have been synthesized by solid-state reactions, reduction of oxides by carbon, borothermal reduction of metal oxide, molten salt electrolysis, and chemical vapor deposition.[1,11,15] Fusion processes, such as metallothermy and selfpropagating high-temperature synthesis, are also used in the production of borides by reduction of metal (including tungsten and boron) oxides with aluminum, magnesium, or calcium.[11] Needless to mention that these processes are generally carried out at elevated temperatures and require technically complex and expensive experimental setup. In addition to the above-mentioned processes, there have been several studies on different tran
Data Loading...
