Mo–Nb–Si–B Alloy: Synthesis, Composition, and Structure

Cast refractory alloys Mo–Nb–Si–B were prepared by centrifugal self-propagating high-temperature synthesis (SHS) from metallothermic mixtures containing MoO3, Nb2O5, Al, Si, and B powders, and additive of Al2O3 as a temperature-moderating and chemically inert agent. Variation in the centrifugal acceleration and amount of the additive affected the composition and structure of cast Mo–Nb–Si–B alloys. In a wide range of values, the combustion temperature was found to exceed 3000 K, and the combustion products were obtained as two-layer ingots of target Mo–Nb–Si–B alloy (lower) and Al2O3 slag (upper).

Evolution of Thermal Microcracking in Refractory ZrO2-SiO2 after Application of External Loads at High Temperatures

Zirconia-based cast refractories are widely used for glass furnace applications. Since they have to withstand harsh chemical as well as thermo-mechanical environments, internal stresses and microcracking are often present in such materials under operating conditions (sometimes in excess of 1700 °C). We studied the evolution of thermal (CTE) and mechanical (Young’s modulus) properties as a function of temperature in a fused-cast refractory containing 94 wt.% of monoclinic ZrO2 and 6 wt.% of a silicate glassy phase. With the aid of X-ray refraction techniques (yielding the internal specific surface in materials), we also monitored the evolution of microcracking as a function of thermal cycles (crossing the martensitic phase transformation around 1000 °C) under externally applied stress. We found that external compressive stress leads to a strong decrease of the internal surface per unit volume, but a tensile load has a similar (though not so strong) effect. In agreement with existing literature on -eucryptite microcracked ceramics, we could explain these phenomena by microcrack closure in the load direction in the compression case, and by microcrack propagation (rather than microcrack nucleation) under tensile conditions.

Selection of refractory materials for vitrification electric furnaces of radioactive waste

It was shown that fused-cast chrome-containing refractories are the most promising as the lining material of designed glass-making electric furnaces and smallsized melters of the next generation. To provide a long (up to 10 years) life of the furnace, its elements that are subject to intensive wear must be made of refractories of HPL-85 type with a high chromium content. The bakor furnace masonry of other elements can be replaced with fused-cast refractory material type HAC-26M with a low content of chromium oxide.Ill.2. Ref. 11. Tab. 5.

The extraction of the associated precious metals out of the construction industry's complex ores

The effective processing methods were investigated for the precious associated components extraction out of the ores by means of the physical and chemical and the chemical and metallurgical enrichment integration. It was established experimentally that the gold's disperse drops melted by means of the external heat source moved to the ore's surface through the pores under the thermocapillary pressure influence. After the enclosing rocks melted the gold drops were floated by the gas bubbles. The pyrometallurgical device was developed to extract the dispersive gold out of the complex ores in the course of the cast refractory materials processing.Ill.3. Ref. 5.