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Spark plasma sintering (SPS) technique was used to consolidate spray dried (SD) powder of TiC (T-SD), TiC-3.5 wt% WC (TW-SD) and TiC-3.5 wt% WC-2 wt% CNT (TWC-SD) at 1600 °C and 50 MPa pressure. Another, similar composition of ball milled (BM) powder of TiC-3.5 wt% WC-2 wt% CNT (TWC-BM) was consolidated by SPS technique at similar parameters, in which in-situ formation of 2-D graphene nanoribbons (GNR) was observed. High temperature plastic deformation (HTPD) behaviours of these four pellets were characterized by in-situ high temperature nanoindentation technique from RT to 650 °C in controlled atmosphere. Occurrence of HTPD was confirmed by analyzing the mechanical properties, plasticity index and plastic deformation zone radius of all four pellets from RT to 650 °C. The structural stability of 1-D CNTs in TWC-SD and 2-D in-situ formed GNRs in TWC-BM pellets was examined by Raman spectra after the HTPD at 650 °C. HR-TEM micrograph has inferred the collapse of CNT edges in TWC-SD pellet and the peeling of GNR layers in TWC-BM pellet after HTPD. However, the CNTs in TWC-SD pellet was able to lower down the plastic deformation zone radius formed due to HTPD by ~60%, while it was only ~20% by in-situ formed GNR in TWC-BM pellet. This was majorly attributed to the difference in stress dissipation mechanisms between CNTs and GNRs. The 1-D CNTs in TWC-SD was found to have axial stress dissipation, while the in-situ formed GNRs in TWC-BM pellet has dissipated the stresses in axial as well as transverse directions because of its 2-D nature. [ABSTRACT FROM AUTHOR]

Titanium carbide (TiC) is reinforced with 3.5 wt% of tungsten carbide (WC) and 2 wt% of carbon nanotubes (CNTs) in order to improve its thermal shock resistance and mechanical integrity of oxide layer. Three pellets namely, TiC (T-SD), TiC-3.5 wt% WC (TW-SD) and TiC-3.5 wt% WC-2 wt% CNT (TWC-SD) were thermally shocked at 1700 °C in an open atmosphere for 10 numbers of thermal cycles. Raman spectra confirmed the retention of CNTs after thermal cycling, which could be attributed to the thermal shielding offered by the molten TiC to CNTs. HR-TEM image infers the collapse of some of the CNTs into carbon structure after the thermal shocks. The mass loss % of T-SD, TW-SD and TWC-SD pellets were found to be 41.5%, 33.3% and 15.13%, respectively after the 10 numbers of thermal cycles. The rate of mass change in T-SD sintered pellet was found to be ~1.4 × 10 −3 g/min., which got reduced to ~0.4 × 10 −3 g/min. on addition of 3.5 wt% of WC and 2 wt% of CNT. Furthermore, reinforcement of 3.5 wt% WC and 2 wt% CNTs in TiC matrix showed the dramatic increase of 89% in thermal shock resistance parameter (R st ) compared to T-SD pellet. This significant improvement in thermal shock resistance of TWC-SD pellet is mainly attributed to the following three factors viz. (i) higher fracture toughness (ii) higher density and (iii) homogeneous dispersion of CNTs, which hinders the movement of oxygen atoms along the grain boundaries. Hardness of the thermally shocked TWC-SD pellet was found to be 5.1 GPa, which was 1.3 GPa i.e. ~74% higher compared to thermally shocked T-SD pellet. This increased hardness of thermally shocked TiC matrix has been shown to suppress the crack formation and restrict oxidation. [ABSTRACT FROM AUTHOR]

Al 2 O 3 , Al 2 O 3 -1 wt% Carbon Nanotube (CNT) and Al 2 O 3 -1 wt% CNT-0.5 wt% Graphene Nanoplatelets (GNP) were consolidated by spark plasma sintering at a temperature of 1500 °C. Spray drying technique was used for uniformly distributing the CNTs and GNPs. Fracture toughness of Al 2 O 3 pellet drastically increased to 168% on addition of CNTs, while substantial improvement of 250% was seen on the addition of both CNTs and GNPs. Interfacial shear stress for Al 2 O 3 -CNT-GNP was found to be 350–1100 MPa. Novel toughening mechanisms such as CNT yarning and CNT embedded graphene was found responsible for the drastic improvement in toughness. [ABSTRACT FROM AUTHOR]

CNTs (2 wt%) reinforced TiC composite with WC (3.5 wt%) as sintering aid was densified using SPS technique at 1600 °C. In-situ formation of wide GNRs (Graphene nanoribbon) was observed due to CNT unzipping in TiC-WC-CNT (TWC) pellet. A phenomenal increase in fracture toughness (∼118%) was observed in TWC pellet compared to TiC. This significant improvement was due to novel toughening mechanisms like GNR grain wrapping, GNR crack bridging and crack bifurcation. Further, TWC pellet showed ∼48% improved thermal shock resistance compared to TiC, which could be due to the suppressed large thermal cracks by CNT and in-situ formed GNR. [ABSTRACT FROM AUTHOR]

This article reports the effect of hybrid reinforcement of carbon nanotubes (CNTs) (1 wt%) and graphene nanoplatelets (GNPs) (0.5 wt%) on electrical conductivity of atmospheric plasma sprayed alumina (Al 2 O 3 ) coating. The uniform dispersion of CNTs and GNPs were observed over Al 2 O 3 matrix. Scratch test revealed the improved inter-splat bonding strength with addition of CNTs and GNPs, which could lead to improved electrical conductivity of Al 2 O 3 coating. The electrical conductivity increased from ~5 × 10 –12 to ~0.7 S/m, by the addition of CNTs (1 wt%) and GNPs (0.5 wt%) in Al 2 O 3 coating. A drastic improvement of ~ 12 orders of magnitude in electrical conductivity was observed in Al 2 O 3 − 1 wt% CNT- 0.5 wt% GNP coatings. This improvement in electrical conductivity was majorly attributed to the lower porosity and strong inter-splat bonding. In addition, availability of more numbers of conductive channels as a result of homogeneous distribution of CNTs/GNPs and clean interface with Al 2 O 3 has played the significant role in enhancement of electrical conductivity. [ABSTRACT FROM AUTHOR]

Several physicochemical properties can be tailored by tuning the lattice strain of the crystal. Here, we report the effect of lattice strain on oxygen ion conduction of oriented samarium doped ceria (SDC) films deposited over an amorphous quartz substrate. Lattice distortion was induced by varying the deposition rate in electron beam deposition technique (EB-PVD). Texture coefficient calculation and pole figure analysis confirms the (111) orientation in out‐off plane direction. Stress state was monitored using sin 2 Ψ method in tri-axial direction and the results indicate a reduction in compressive stress with an increase in deposition rate. A difference in the mean free path of adatom influences the surface morphology of SDC films with compressive stress leading to a significant impact on conductivity. Compared to higher compressive stress, thin film containing lower stress along (111) orientation exhibited a two order enhancement in conductivity. The faster ionic conductivity arises from the ease of oxygen ion hopping through the expanded lattice as compared to the highly-stressed crystal structure. Thus, the deposition rate in EB-PVD provides a valuable technique for engineering the strain to realize the potential enhancement in the efficiency of electrolyte for ITSOFC application. [ABSTRACT FROM AUTHOR]