China
Africa
Explore chapters and articles related to this topic
Pore defects and process control of pure molybdenum using wire arc additive manufacturing
Published in Domenico Lombardo, Ke Wang, Advances in Materials Science and Engineering, 2021
Y.A. Qiao, J.C. Wang, S.Y. Tang, C.M. Liu
Molybdenum (Mo) is a refractory metal, and it is widely used in aerospace[1,2], nuclear [3–6], electronics industry [7], and other industry fields because of its high melting point, good mechanical properties, good thermal and electrical conductivity, and low coefficient of linear expansion[8,9]. However, Mo and its alloys have poor processing properties due to their high melting point and low plastic-brittle transition temperature, limiting the applications. Additive manufacturing (AM) provides a new method to fabricate molybdenum, but there are many defects and cracks in samples fabricated by AM [10]. This paper analyzes the mechanism of pore defects development in pure Mo fabricated by wire arc additive manufacturing (WAAM).
Sulphide Ores
Published in Earle A. Ripley, E. Robert Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, L. Moira Jackson, Environmental Effects of Mining, 2018
A. Ripley Earle, Robert E. Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, Earle A. Ripley, E. Robert Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, L. Moira Jackson
Molybdenum is mined for itself, as well as being a by-product or co-product of other sulphide ores. Canada is one of the world’s main producers (Table 5.1). The most common ore is molybdenite; the mineral is currently mined only in British Columbia. Molybdenum is used both in its pure metal form and, in other forms, as an alloy additive, as a lubricant, and as a component of chemicals used for such diverse purposes as reagents, pigments, glazes and enamels, fertilizers, and electroplating compounds.
Properties and Applications of Molybdenum
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
Among the materials which have a potential for sustained service at high temperatures, molybdenum appears to be the most promising one for general use in view of its high strength at elevated temperatures, high melting point, and high modulus of elasticity. Again, the low expansion, low specific heat, and high thermal conductivity combination imparts to the metal good thermal shock resistance, heat transfer, and fatigue properties. For these reasons, molybdenum and its alloys are well suited for some of the current and future applications involving missile and power plant components operating at temperatures over 1000°C.
Influence of processing conditions on the properties of thermal sprayed coating: a review
Published in Surface Engineering, 2021
Molybdenum (Mo) is principally utilised as an alloying element to steel to enhance the mechanical characteristics such as strength, creep resistance, fracture toughness, etc., by the development of dispersed carbides. However, Mo begins to oxidise significantly in an air environment at a temperature of 300°C. Oxidation becomes quick at a temperature of 500°C and the rate of attack becomes very rapid when the temperature reaches about 1200°C [162]. At a temperature less than 400°C an adherent relatively stable MoO2 scale is developed and oxidation takes place as per the parabolic law under diffusion-controlled transport through the growing scale. But, molybdenum dioxide (MoO2) is unstable to further oxidation to molybdenum trioxide (MoO3), which has a significant vapour pressure. However, the vapour pressure of MoO3 becomes progressively significant at a temperature above 500°C, based upon on the total partial pressure of oxygen [163].
Multiscale Simulations of Thermal Transport in W-UO2 CERMET Fuel for Nuclear Thermal Propulsion
Published in Nuclear Technology, 2021
Marina Sessim, Michael R. Tonks
One fuel type being considered for NTP reactors is a ceramic-metal composite (CERMET). The CERMET fuel is composed of ceramic fuel particles embedded in a metal matrix. Uranium dioxide (UO2), uranium carbide (UC), and uranium nitride (UN) are possible uranium-bearing materials with a high enough melting temperature to withstand the conditions during the propulsion cycles. The metal matrix must also have a high enough melting temperature to withstand the propulsion cycles and a higher thermal conductivity than the fuel. Thus, refractory metals such as tungsten (W) or molybdenum (Mo) are the primary candidates. In addition, the neutron absorption cross section of the metal should be as low as possible, as any neutron absorption in the metal matrix will lower the efficiency of the CERMET fuel. Early NTP CERMET fuel designs used highly enriched UO2 as the fuel particle and W as the metal matrix material.7 However, there is now a move to low enrichment, so fuel materials with a higher uranium density than UO2, such as UN, are being considered.9 Molybdenum or a W-Mo alloy is being considered for the matrix, as Mo has a lower neutron absorption cross section than W. Many fuel element designs also include cladding of the fuel element outer surface and the subchannel surfaces. This cladding is often composed of the same material as the metal matrix.
Optimization of a solvent extraction route for the recovery of Mo from petroleum refinery spent catalyst using Cyphos IL 102
Published in Solvent Extraction and Ion Exchange, 2018
Rashmi Singh, Harshit Mahandra, Bina Gupta
Molybdenum is a strategic metal and extensively used in X-ray tubes, petroleum refining, thermocouples, and in steel alloys due to its high tensile strength and melting temperature.[1,2] According to IMOA (International molybdenum association) global consumption of molybdenum in 2016 was around 512 million lbs which rose to 558 million lbs in 2017.[3] The increasing demand of molybdenum and rapid depletion of its primary sources make it important to recover molybdenum from its secondary sources. Molybdenum catalysts are major secondary sources of Mo, which are used for hydrodesulphurization (HDS) process in petrochemical refineries. These catalysts during desulphurization process are contaminated and deactivated by toxic materials and discarded as waste leading to environmental risks. The spent HDS contains valuable metals, such as Mo, Co, Ni, Al, and V. Global generation of such spent hydro processing catalysts is estimated to be 150,000–170,000 tonnes per year.[4] In this context, molybdenum recovery from spent catalysts is important economically as well as environmentally.