Molybdenum, valued for its high melting point and exceptional physical and chemical properties, is studied in diverse fields such as electronics, petrochemicals, and aviation. Among molybdenum oxides, molybdenum dioxide stands out for its higher electrical conductivity than other transition metal oxides due to its structural characteristics, exhibiting metallic properties. It is applied as pellets to gas sensors, semiconductors, and secondary batteries for its properties. Thus, research on molybdenum dioxide compaction and pressureless sintering is necessary, yet research on pressureless sintering is currently insufficient. This study synthesized MoO₃ powder via solution combustion synthesis and reduced it using the 3% hydrogen/argon gas mixture to investigate the effect of reduction temperature on the powder. Additionally, the reduced powder was compacted and subjected to pressureless sintering with temperature as a variable. The density and the microstructure of brown parts were analyzed and discussed.

In this study, lanthanum oxide (La2O3) dispersed molybdenum (Mo–La2O3) alloys are fabricated using lanthanum nitrate solution and nanosized Mo particles produced by hydrogen reduction of molybdenum oxide. The effect of La2O3 dispersion in a Mo matrix on the fracture toughness at room temperature is demonstrated through the formation behavior of La2O3 from the precursor and three-point bending test using a single-edge notched bend specimen. The relative density of the Mo–0.3La2O3 specimen sintered by pressureless sintering is approximately 99%, and La2O3 with a size of hundreds of nanometers is uniformly distributed in the Mo matrix. It is also confirmed that the fracture toughness is 19.46 MPa·m1/2, an improvement of approximately 40% over the fracture toughness of 13.50 MPa·m1/2 on a pure-Mo specimen without La2O3, and this difference in the fracture toughness occurs because of the changes in fracture mode of the Mo matrix caused by the dispersion of La2O3.

The effect of Cu on the hydrogen reduction of powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of , which comprised the contained chemical vapor transport of . This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of to particles from or . Such an activated reduction process results in the deposition of Mo and particles on the surface of the Cu.