Carbon nanotube-based hybrid materials integrated with conducting stainless steel mesh is of great importance for developing electrochemically stable and mechanically flexible supercapacitors. We report sweet spot tunable CVD growth of vertically aligned carbon nanotube coated with TiO 2 on stainless steel mesh with remarkable supercapacitor performance. Aligned CNT forest growth is observed at certain distance from the upstream inside the heating zone. We find that residence time of the carbon precursor has significant influence on controlling the density and height of vertically aligned carbon nanotube forest. When the residence time is increased by reducing the carrier gas flow rate from 590 to 300 sccm, vertically aligned carbon nanotube forest height is increased significantly from ∼9 to ∼31 μm on stainless steel mesh. The developed vertically aligned CNT forest on stainless steel mesh found to be suitable for supercapacitor electrode but its superhydrophobic nature limits its energy storage performance. To tune its wettability for further improving the electrode performance, 3 nm TiO 2 conformal coating is introduced on VACNT-SS mesh using atomic layer deposition. TiO 2 −VACNT hybrid shows superhydrophilic nature and able to achieve 16.24 mF/cm 2 specific capacitance in particular current density of 1.67 mA/cm 2 . This CNT−TiO 2 hybrid outperforms other CNT based supercapacitor electrodes and shows high power density of 1.18 mW/cm 2 . Around 99.7% capacitance was retained by the developed hybrid after 5000 charge−discharge cycles. Supercapacitor measurements performed in flexible geometry and after severe ultrasonication to ensure the mechanical stability and flexibility of the developed TiO 2 -coated CNT forest on SS mesh.

The limited thermoelectric performance of p-type Higher Manganese Silicides (HMS) in terms of their low figure-of-merit (ZT), which is far below unity, is the main bottle-neck for realising an efficient HMS based thermoelectric generator, which has been recognized as the most promising material for harnessing waste-heat in the mid-temperature range, owing to its thermal stability, earth-abundant and environmentally friendly nature of its constituent elements. We report a significant enhancement in the thermoelectric performance of nanostructured HMS synthesized using rapid solidification by optimizing the cooling rates during melt-spinning followed by spark plasma sintering of the resulting melt-spun ribbons. By employing this experimental strategy, an unprecedented ZT ∼ 0.82 at 800 K was realized in spark plasma sintered 5 at% Al-doped MnSi HMS, melt spun at an optimized high cooling rate of ∼2 × 10 K s. This enhancement in ZT represents a ∼25% increase over the best reported values thus far for HMS and primarily originates from a nano-crystalline microstructure consisting of a HMS matrix (20-40 nm) with excess Si (3-9 nm) uniformly distributed in it. This nanostructure, resulting from the high cooling rates employed during the melt-spinning of HMS, introduces a high density of nano-crystallite boundaries in a wide spectrum of nano-scale dimensions, which scatter the low-to-mid-wavelength heat-carrying phonons. This abundant phonon scattering results in a significantly reduced thermal conductivity of ∼1.5 W m K at 800 K, which primarily contributes to the enhancement in ZT.

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Boosting the energy density of carbon‐based materials is of great importance for developing supercapacitors with high cyclic stability. Chemical vapor deposition (CVD) growth of vertically aligned carbon nanotube (VACNT) forest is reported with millimeter height on Si/SiO2 substrate and engineer its microstructure and wettability for remarkable supercapacitor performance. A simple method to alter the microstructure of VACNT forest by adding small amount of ethanol in KOH electrolyte is demonstrated. The modified electrolyte facilitates the formation of pores and channels in CNT forest and leads to increased active surface area. Microstructure‐engineered CNT forest is further coated conformally with 3 nm of TiO2 using atomic layer deposition. The developed VACNT‐TiO2 hybrid shows 102‐fold increase in energy density, 20‐fold increase in specific capacitance, and 13‐fold increase in power density along with high capacitive retention as compared to bare VACNT in KOH. This improved performance is correlated to formation of micro channels that enable more accessible surface area for electrolytic ions. The demonstrated simple electrolyte engineering approach with increased energy density of aligned CNT‐TiO2 hybrid is relevant for portable energy storage applications.