Molybdenum’s Applications in Various Areas

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Molybdenum has been widely used in all sorts of areas, including not only the steel sector but also plants. Molybdenum is one of essential “trace elements” in plants, accounting for plant dry matter of about 0.5ppm, indispensable and irreplaceable. Ammonium molybdate as a micronutrient fertilizer has been widely used all over the world in recent years; it can significantly improve quality and yield of legumes, forage and other crops, mainly because molybdenum can promote rhizobium and other diazotroph to fix nitrogen in air, and further turn nitrogen into the protein that plants require. Molybdenum can also promote plant uptake of phosphorus and play its role in plants. Molybdenum can accelerate the formation and transformation of carbohydrate in plants, but also improve plants’ chlorophyll content, stability, and vitamin C content. Not only that, molybdenum can also improve plants’ cold resistance, drought resistance and disease resistance. With less dosage, great effect and low cost, molybdenum fertilizer is an important measure to improve agricultural yields especially for soybean harvest. That molybdenum is widely used in agriculture has opened up a new way for the comprehensive utilization of waste water, waste residue and low grade ore from molybdenum production plant in China.

Molybdenum can be applied to oil and gas drilling pipelines, but also combine with diamond and nickel as catalysts for petroleum refining pretreatment, mainly used for the desulfurization of oil, petrochemical products and liquefied coal. In the process of hydrotreating, sulfide reacts with hydrogen on the surface of catalysts, to remove sulfide ions in the form of hydrogen sulfide as well as nitrogen and metal impurities of crude oil, which can reduce other catalysts poisoning by these impurities in petroleum refining, thereby improving product color, odor and stability. After the passivation of molybdenum catalysts, there is a layer of carbon residue on the surface. If burned the carbon layer, catalysts can recover to activated state, with service life of about 1-5 years. Molybdenum is an ideal electron donor and carrier, and plays an important role in petroleum cracking and reforming. Developing sour natural gas, oil field and undersea oil and gas fields in low-lying areas, a large number of H2S gas production and marine corrosion allow the drilling pipeline sulfuration and rapid corrosion. High-strength stainless steel tubes containing molybdenum can effectively resist corrosion of H2S gas and seawater, which significantly saves steel and reduces drilling cost of oil and gas.

With superior electrical conductivity and high-temperature properties, especially thermal expansion coefficient extremely similar to the glass, molybdenum is widely used in the manufacture of core wire, lead wires, hooks, brackets, side lever and other parts of lamp coiled filament; in the production of gate and anode support material in the electron tube; as metal-oxide semiconductor gate in very large scale integrated circuit. Integrated circuit is mounted on the molybdenum, which can eliminate the “bi-metal effect”. Ultra-thin seamless molybdenum tubes (approximately 15μm) can be used as anode bracket of high-definition television picture tube; this television has 1,125 of image scanning lines, twice than the average television. Molybdenum wafer can be applied to heat shield of power transistor and substrates and heat sinks of silicon rectifier.

In addition to the use of pure molybdenum in modern electronics industry, Mo-Re alloy can be used as structural materials for tubes and special lamps. Mo-50Re and TZM alloy can be used as thermionic cathode structure elements for high-power microwave tube and millimeter-wave tube, with working temperature up to 1,200°C and current density up to 10 amperes per square centimeter. Pure molybdenum wire is used as lead with low recrystallization temperature, which is prone to embrittlement at high temperatures, affecting service life. In recent years, it has been developed to add Si, K, and C elements to raise the recrystallization temperature so as to produce “high-temperature molybdenum wire”. Adding rare earth elements such as yttrium, cerium and lanthanum in the production process of molybdenum oxide can more effectively improve the recrystallization temperature, overcoming material embrittlement at high temperatures. Molybdenum wire, containing 0.1-0.3% of zirconium and 0.1% of scandium, allows scandium diffuse throughout the alloy in the process of the nitriding at 1,200°C, finally with tensile strength up to 1.4 billion Pascal at 20°C.

Electric discharging machining has been widely applied with rapid development of mold industry. Molybdenum wire is an ideal electrode wire of wire cut electrical discharge machine, which can cut all kinds of steel and cemented carbide and machine parts with extremely complex shape, but also can effectively improve the accuracy of molds with stable discharge machining. With development and rise of light bulb and mold manufacture, production and consumption of molybdenum wire have been increasing by leaps and bounds. According to the China Lighting Association statistics, the total production of molybdenum wire reaches 3.15 billion meters in 2001, with actual production estimated to 4 billion meters, consuming nearly 800 tons molybdenum. Of which, more than 2 billion meters are used for wire cutting, accounting for more than half of the total molybdenum wire. So market prospects of molybdenum wire are very encouraging.

Tungsten-copper pseudo alloys are widely used as electric spark cutting tool electrode. But in recent years, the study on replacing tungsten by molybdenum as electrode suggests that corrosion resistance of tungsten-based and molybdenum-based electrode varies with copper content (≤50% by weight). When the heating pulse and the mechanical load pulse exist, the corrosion resistance depends on the embrittlement process. With transition temperature of ductile-to-brittle lower than tungsten, molybdenum has small brittleness, but strong corrosion resistance. Molybdenum-copper and molybdenum-silver pseudo alloy, with ablation resistance and excellent electrical conductivity, can be used as air switches, high-voltage switches and contactor contacts. With a large number of discrete molybdenum particles in continuous copper matrix, as well as uniform microstructure, superior thermal conductivity and electrical conductivity, molybdenum-copper composite films can be used as metal core of multilayer circuit board.

Currently, molybdenum trioxide has been developed. This material could change colors in the bright light, and could be easily restored, used as computer optical storage devices and multiple-use copy materials.