A study on graphene platelet/zirconia-toughened alumina (GPL/ZTA) composites was carried out to evaluate the potential of the new structural materials GPL–ZrO2–Al2O3 powders were obtained by ball milling of graphene platelets and alumina powders using yttria stabilized ZrO2 balls Samples were sintered at different temperatures using spark plasma sintering Fracture toughness was determined by the single-edge notched beam method The results show that the GPLs are uniformly distributed in the ceramic matrix and have survived high temperature sintering processes Several sintering experiments were carried out It is found that at 1550 °C, GPL/ZTA composites were obtained with nearly full density, maximum hardness and fracture toughness A 40% increase in fracture toughness in the ZTA composite has been achieved by adding graphene platelets The toughening mechanisms, such as pull out, bridging and crack deflection, were observed and are discussed

Toughening of zirconia/alumina composites by the addition of graphene platelets

Composites are, in general, a rapidly evolving and growing technical field with a very wide range of applications across the aerospace, defence, energy, medical and transport sectors as a result of...

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Selection, processing, properties and applications of ultra-high temperature ceramic matrix composites, UHTCMCs – a review

Graphene NanoPlatelets (GNP) reinforced tantalum carbide composites are synthesized by spark plasma sintering (SPS) at processing conditions of 1850 °C and 80–100 MPa. The GNP addition enhances the densification of TaC–GNP composites to 99% theoretical density, while reducing the grain size by over 60% through grain wrapping mechanism. Survival and structure retention of GNP is confirmed through scanning electron microscopy and micro-Raman spectroscopy. Nanoindentation and high load (20–30 N) microindentation are utilized to evaluate elastic modulus and hardness. GNP improves fracture toughness of TaC by up to 99% through toughening mechanisms such as GNP bending, sheet sliding, cracking bridging, and crack deflection.

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Graphene NanoPlatelets reinforced tantalum carbide consolidated by spark plasma sintering

Distribution and stability of carbon nanotubes during multi-pass friction stir processing of carbon nanotube/aluminum composites

Friction stir processing (FSP) is a rapidly emerging newer solid-state technique for composite fabrication. It involves surface modification which in turn enables successful adaptation of surface p...

A Review of Recent Progress in Solid State Fabrication of Composites and Functionally Graded Systems Via Friction Stir Processing

TaC–4 wt.% CNT composites were synthesized using spark plasma sintering. Two kinds of CNTs, having long (10–20 μm) and short (1–3 μm) length, were dispersed by wet chemistry and spray drying techniques respectively. Spark plasma sintering was carried out at 1850 °C at pressures of 100, 255 and 363 MPa. Addition of CNTs leads to an increase in the density of 100 MPa sample from 89% to 95%. Short CNTs are more effective in increasing the density of the composites whereas long CNTs are more effective grain growth inhibitors. The longer CNTs are more effective in increasing the fracture toughness and an increase up to 60% was observed for 363 MPa sample. Hardness and elastic modulus are found to increase by 22% and 18% respectively for 100 MPa samples by addition of long CNTs. Raman spectroscopy, SEM and TEM images indicated that the CNTs were getting transformed into flaky graphitic structures at pressure higher than 100 MPa.

Spark plasma sintered tantalum carbide-carbon nanotube composite: Effect of pressure, carbon nanotube length and dispersion technique on microstructure and mechanical properties

Composite coatings consisting of TiC/SiC/Ti3SiC2 phases have been synthesized using spark plasma sintering (SPS) of Ti/SiC/C powder mixture on titanium substrate. The processing of composite coatings was achieved at 1300 °C and 1400 °C with a uniaxial pressure of 90 MPa and holding time of 8 min. Identification and quantification of the phases have been performed using x-ray diffraction (XRD). X-ray elemental maps obtained using EDS have been used to analyze the evolution of various phases and their distribution in the microstructure. A tentative mechanism for phase evolution based on exothermic reactions between various constituent powders has been proposed. Microhardness of the spark plasma sintered coatings was found to be ~ 3 times that of the Ti substrate resulting in ~ 100 times lower wear weight loss in ball-on-disc wear tests.

David A. Virzi

Papers

Spark plasma sintered tantalum carbide-carbon nanotube composite: Effect of pressure, carbon nanotube length and dispersion technique on microstructure and mechanical properties

In-situ synthesis of TiC/SiC/Ti3SiC2 composite coatings by spark plasma sintering