Spark Plasma Synthesis Research Articles

Influence of Synthesis Temperature on the Defect Structure of Boron Carbide: Experimental and Modeling Studies

Boron carbide (B4C) was synthesized from the elements at temperatures ranging from 1300° to 2100°C using the spark plasma synthesis method. Significant densification commenced at about 1500°C and was accompanied by a corresponding decrease in the defect structure of this carbide. Changes in the X‐ray diffraction patterns were in agreement with predictions of simulation studies based on the presence of twins. Transmission electron microscopy observations were consistent with the experimental observations and the modeling predictions.

Simultaneous spark plasma synthesis and consolidation of WC/Co composites

The single-step synthesis and densification of the WC–6Co cemented carbide starting from elemental powders was obtained by the spark plasma sintering (SPS) technique. The operating conditions that guarantee the complete conversion of the reactants to the desired full dense material have been identified. Specifically, under the application of 800 A and a mechanical pressure of 40 MPa for about 200 s, a product with relative density higher than 99%, hardness of 14.97 ± 0.35 GPa, and 12.5 ± 1.0 MPa m0.5 fracture toughness was obtained. A kinetic investigation of the SPS process was also performed. It revealed that an intermediate phase, i.e., W2C, is the first carbide formed during the carburization process. It was observed that the synthesis and sintering stages take place simultaneously. It was also found that as the applied pulsed current intensity was augmented, the synthesis/sintering time required decreased significantly.

Spark plasma synthesis from mechanically activated powders: a versatile route for producing dense nanostructured iron aluminides

The possibility of mechanically activated spark plasma sintering (MASPS) to perform simultaneously within a very short period of time the synthesis and the consolidation of nanophase iron aluminide from mechanically activated powders of Fe and Al in two different ratio (Fe53 at.% and Fe60 at.%) were confirmed in this work.

A kinetic model for the field-activated synthesis of MoSi 2/SiC composites: simulation of SPS conditions

A modeling study was carried out to simulate the direct synthesis of MoSi 2–SiC composites from the elements using field activation. The study was made to simulate the experimental process of spark plasma synthesis (SPS), which has been utilized previously to simultaneously synthesize and densify materials, including nanophases. The results show a temporal dependence for the formation of the two products. The dependence of the reaction wave dynamics on composition was also investigated. A transition from volume combustion, in which the reactants are converted instantly to the products throughout the entire sample, to a wavelike reaction, in which the conversion front traverses the sample in a finite time, is shown to depend on sample size and product. Conversion fronts traverse the sample as concentric waves propagating outward or inward depending on the composition of the composite and on the die conductivity.

Synthesis of Dense TiB2‐TiN Nanocrystalline Composites through Mechanical and Field Activation

The synthesis of dense nanometric composites of TiN‐TiB2 by mechanical and field activation was investigated. Powder mixtures of Ti, BN, and B were mechanically activated through ball milling. Some powders were milled to reduce crystallite size but to avoid initiating a reaction. In other cases powders were milled and allowed to partially react. All these were subsequently reacted in a spark plasma synthesis (SPS) apparatus. The products were composites with equimolar nitride and boride components with relative densities ranging from 90.1% to 97.2%. Crystallite size analyses using the XRD treatments of Williamson‐Hall and Halder‐Wagner gave crystallite sizes for the TiN and TiB2 components in the range 38.5–62.5 and 31.2–58.8 nm, respectively. Vickers microhardness measurements (at 2 N force) on the dense samples gave values ranging from 14.8 to 21.8 GPa and fracture toughness determinations (at 20 N) resulted in values ranging from 3.32 to 6.50 MPa·m1/2.

Synthesis of dense nanometric MoSi2 through mechanical and field activation

The effect of mechanical and field activation on the synthesis of dense nanometric MoSi2 was investigated. Powders of Mo and Si, milled separately or comilled in a planetary ball mill, were reacted in a spark plasma synthesis (SPS) apparatus under different electric current conditions. Milled powders reacted faster and required less current than unmilled powders. Mixtures of powders which were milled separately (to nanometric size) reacted in the SPS to produce micrometric α–MoSi2. Similar results were obtained for samples comilled to produce nanometric reactants which did not contain detectable amounts of the product phase. When products form during milling, they contain both the α and β modifications of MoSi2. The product after the SPS reaction was nanometric MoSi2 with a crystallite size of 140 nm.