Preparation of Porous Alumina/Nano-Nickel Composite by Gel Casting and Carbothermic Reduction

Abstract

Effects of dispersant (Tri polyphosphate sodium) amount on gel viscosity, mechanical activation of raw materials, raw materials mixture composition, and reduction atmosphere on the prepared composites and NiO reduction mechanism were investigated. It was found that 2.5 wt % dispersant is an optimum amount for a gel suspension with 50 V% of solid consisting of alumina, graphite, and nickel oxide. XRD results of reduced and sintered product (at 1200-1500 °C) showed that alumina, nickel, and nickel aluminate spinel are present in the prepared composite. The porosity of the composite made with 12 h ball milledalumina was 48%, while it was 64 % in the sample made with 20 min ball-milled alumina. The results of TG-DTA analyses showed that the reduction temperature and mechanism are dependent on the raw materials' ball milling time. Thermal analyses revealed that mechanical activation of raw materials decreases the NiO reduction temperature and increases the metallic Ni production.

Effect of Graphite Addition on the Microstructure, Mechanical Properties and Oxidation Resistance of HfB2-SiC Composites Prepared by the SPS Method

“…In addition, microcracks were observed in HfB2 (white arrow) particles. Differences in the thermal expansion coefficients of these two phases could lead to compressive or tensile residual stresses in the deboride matrix, eventually creating micro-cracks [36,37]. The mean grain size curve of HfB2-SiC composites after the sintering process is shown in Figure 6.…”

NiO-Ni-Al2O3(γ) Nanocatalyst by Pulse Electrocodeposition Over Ni Open-cell Foam for Methane Reforming

“…Usually, combining transition and/or noble metals catalysts on stabilized supports (alumina, ceria, ceria promoted alumina, zeolite, etc. in catalysts have been frequently used [3][4][5]. However, nickel was the most common catalyst for being cheap, active, and selective in MSR [6,7].…”