Studies on electrochemical dissolution of sintered molybdenum discs as a potential method for targets dissolution in 99mTc production

Electrochemical dissolution of pressed into discs and sintered metallic molybdenum powder with the mass of 712 ± 10 mg (n = 15) in potassium hydroxide solution was studied in detail. The technique was considered to apply for dissolution of irradiated 100Mo target in the 99mTc production. The effect of various parameters, e.g., the concentration of the electrolyte solution, temperature, current density, and surface area of the platinum cathode, was investigated. The shortest time for total dissolution of molybdenum target was 70 min. This result was achieved using an electrolyte solution of 5 M KOH, temperature 55 °C and the current density of 365 mA/cm2.

STUDY OF PROPERTIES OF DIFFUSION-HARDENING COMPOSITE SOLDER GASN-CUSN-MO

В статье обсуждается возможность регулирования свойств диффузионнотвердеющего припоя (ДТП) на основе легкоплавкого сплава галлий-олово и твердой компоненты состоящей из порошка сплава медь-олово посредством введения инертного порошка металлического молибдена и термической обработки. Оценена микротвердость и термическая устойчивость композиционных диффузионнотвердеющих припоев. Показано, что повторная термическая обработка при высоких температурах способствует переходу припоя в равновесное состояние, при этом происходит резкое увеличение твердости, почти на порядок. Подтверждено, что инертные наполнители снижают механическую прочность относительно начального диффузионно-твердеющего припоя, даже те, которые хорошо смачиваются галлием, однако существует некий диапазон, содержащий определенное количество инертного компонента, у порошка молибдена это 15 %, при котором микротвердость композиционного припоя выходит на максимум. The article discusses the possibility of regulating the properties of a diffusion-hardening solder based on a low-melting gallium-tin alloy and a solid component consisting of a copper-tin alloy powder by introducing an inert metal molybdenum powder and heat treatment. The microhardness and thermal stability of composite diffusion-hardening solders were evaluated. It is shown that repeated heat treatment at high temperatures contributes to the transition of the solder to an equilibrium state, with a sharp increase in hardness, almost by an order of magnitude. It is confirmed that inert fillers reduce the mechanical strength relative to the initial diffusion-hardening solder, even those that are well wetted with gallium, but there is a certain range containing a certain amount of the inert component, for molybdenum powder it is 15 %, at which the microhardness of the composite solder reaches the maximum.

Effect of Potassium Element Content and Crystal Form of Ammonium Tetramolybdate and Reduction Conditions on Properties of Molybdenum Powder

As the raw material for producing molybdenum products, the quality of molybdenum powder such as purity, microstructure, particle size and distribution, has great influence on the microstructure of molybdenum products, which will affect its performance. In this study, the effect of potassium element content and crystal form of ammonium tetramolybdate and reduction conditions on the properties of molybdenum powder was studied. The results show that under the same reduction conditions, the particle size of molybdenum powder obtained by the reduction of high potassium ammonium tetramebolybdate is larger than that obtained by the reduction of low potassium ammonium tetramebolybdate. The particle size distribution of molybdenum powder obtained by the reduction of ammonium tetramebolybdate with mixed crystal form (α-type and β-type) is wider, while that obtained by the reduction of ammonium tetramebolybdate with single crystal form (β-type) is narrower and the particle size is more uniform. The higher the reduction temperature is and the lower the hydrogen flow rate is, the larger the particle size of molybdenum powder will be. The agglomeration degree of molybdenum prepared by β-type ammonium tetramolybdate is lighter than that prepared by ammonium tetramolybdate with mixed crystal form (α-type and β-type), and its sieving rate is higher.

Preparation and Properties of Spherical Mo Powders by Plasma Rotating Electrode Process for Additive Manufacturing

Since molybdenum has very high melting point of 2620 °C, there are many difficulties in its forming and post-processing, especially for deep processing. Furthermore as molybdenum is expensive, the utilization rate is important for the molybdenum processing. Additive manufacturing can directly manufacture the parts without mold and increase the utilization rate, and brings an opportunities for the new direction of deep processing for molybdenum. Due to the high quality requirements of molybdenum powder in additive manufacturing technology, the high-quality spherical molybdenum powder was prepared by plasma rotating electrode process method in the present study. The morphology, particle size and particle size distribution, chemical and physical properties were investigated. The molybdenum powder prepared by plasma rotating electrode process method showed to have high purity, high sphericity, good fluidity and high bulk density, proper particle size distribution and low gap element within the powder. The microstructure of the powder was a mixed structure of dendrites and cell crystals formed by rapid solidification, and as the particle size of the powder gradually decreased, the microstructure of the powder surface was remarkably refined. Within a certain range, the molybdenum powder with a wide particle size distribution had better fluidity and higher bulk density. The high-quality spherical molybdenum powder was prepared by plasma rotating electrode process method, which can meet the requirements of additive manufacturing technology for powder material performance.