Thermoanalytical and dilatometric studies of the Al2O3–Cu–Mo hybrid composite

Abstract

The present research is focused on the characterization of the composites from Al 2 O 3-Cu-Mo system. The composites were prepared by slip casting method and subsequent sintering of green bodies in a reduced atmosphere. Two series of samples with different volume content of metallic powders were produced in the work: 10 vol% and 15 vol% of metal content with respect to the total solid-phase content. The sintering process of the composites was analyzed in detail. The linear shrinkage of the composites was measured. The shrinkage curves were obtained by dilatometry test in a heating mode. The composites were characterized by DTA/TG analyses and thermal conductivity. The composites were characterized by XRD, SEM, and EDX. The hardness was measured by Vickers hardness tester. Moreover, the Brazilian test was performed to determine the tensile mechanical properties of the composites. Fractography investigation was carried out as well. Dilatometric tests showed that the increase of the metallic phase volume in the ceramic matrix causes a decrease in the starting temperature of densification. Simultaneously, dilatometric experiments indicated that an increasing amount of metallic particles into the ceramic matrix increases the temperature of maximum densification and decreases the total shrinkage of the composites during sintering. The DTA/TG showed the characteristics of the dispersant decomposition to the atmosphere during thermal treatment and increase of mass connected with the oxidation of metals. Fractography results revealed good adhesion between Al 2 O 3 matrix and the metallic phase. The observation allowed to conclude that the Al 2 O 3 matrix surface is characterized by the brittle fracture mechanism.

Novel Functionally Gradient Composites Al2O3-Cu-Mo Obtained via Centrifugal Slip Casting

“…The above sintering curve profile was applied based on previous study findings for this system. [28] III. RESULTS…”

“…The authors' previous research shows that to obtain an effective composite molding process and to produce specimens with the appropriate properties, the suspension must be dispersed and stable over time. [28] Studies have shown that suspensions containing 50 vol pct solid content with 10 vol pct and 15 vol pct of metal particles (Cu and Mo) with respect to the total solid-phase content were stable for 24 h from the moment of mass preparation. [28] In this investigation, the sedimentation studies were extended to include another slurry that contained 5 vol pct metallic phase.…”

“…[28] Studies have shown that suspensions containing 50 vol pct solid content with 10 vol pct and 15 vol pct of metal particles (Cu and Mo) with respect to the total solid-phase content were stable for 24 h from the moment of mass preparation. [28] In this investigation, the sedimentation studies were extended to include another slurry that contained 5 vol pct metallic phase. To determine the stability of the slurries over time, a sedimentation test was performed for three suspensions with different metallic phase contents (5 vol pct, 10 vol pct, 15 vol pct).…”

“…These results are consistent with the literature data presented in previous works. [28,40,41] K. Microhardness Test Figure 15 shows the results of the microhardness test. The results revealed a nonhomogeneous distribution of hardness along the radial direction of the samples.…”

“…[25] The results of our research conducted on composites obtained by slip casting and centrifugal slip casting allowed us to conclude that the addition of the second metallic component, in this case, molybdenum, prevents or limits the escape of liquid copper and may provide better properties of the manufactured composites. [26,27] Thermal analysis and dilatometric research results of the Al 2 O 3 -Cu-Mo composite presented in [28] revealed decomposition and mass were increasing above the temperature of 600°C, which is connected with Cu and Mo oxidation. Higher growth of mass is observed in composites with higher content of the metallic phase.…”