Volume 113, Issue 12

Graphite flake/Al composites are promising thermal management materials due to their light weight and excellent thermal properties. The interface structure is a key factor that impacts the thermophysical properties. In this work, prediction models based on the acoustic mismatch model (AMM) and the effective medium approach (EMA) were developed to evaluate the effect of the alloying elements on the interfacial thermal conductance (ITC) and thermal conductivity (TC) of graphite flake/Al composites. With the increase in Si content, the ITC for the graphite flakes/Al composites increases clearly. In contrast, the ITC for the graphite flakes/Al composites decreases with the increase in Mg content. The variation range of ITC of graphite flakes/Al–Mg–Si composites is (2.3 × 10 7 –3.1 × 10 7 ) W m −1  K −1 . The thermal conductivity of the graphite flakes/Al–Mg–Si composites is in the range of (412–476) W m −1  K −1 . With the increase in the volume fraction of graphite flake, the thermal conductivity of the graphite flakes/Al composites is significantly improved.

Friction and wear behaviour of nano-sized silicon nitride in beta phase (β-Si 3 N 4 ) under dry conditions were studied. Flat β-Si 3 N 4 samples were prepared by means of the spark plasma sintering method. Sliding tests were performed using a reciprocating ball-on-flat tribometer against silicon carbide (SiC) ball and silicon nitride (Si 3 N 4 ) ball under various normal loads. The frequency was set at 1 Hz and the sliding distance at 20 mm. The morphology of the worn surfaces was analysed by scanning electron microscopy. Experimental results showed that for normal load ranging from 11 to 57 N the friction coefficient increases from 0.15 to 0.36 for the β-Si 3 N 4 /SiC tribo-pair and from 0.8 to 0.9 for β-Si 3 N 4 /Si 3 N 4 tribo-pair. Whereas, for both tribo-pairs, the specific wear rate decreases with the increase in normal load to reach an asymptotic minimum for high loads whose value is 0.15 × 10 −3  mm 3 N −1  m −1 for β-Si 3 N 4 /SiC and 0.3 × 10 −3  mm 3 N −1  m −1 for β-Si 3 N 4 /Si 3 N 4 . The experimental results show also that depending on the tribo-pair and normal load, soft and hard wear mechanisms are activated.

This purpose of this research work primarily focuses on assessing the contact characteristics of a novel 3D printed flexible poly lactic acid (PLA) fingertip exposed to a normal load ranging from 1–750 N. The 3D printed fingertip is pressed against three different target surfaces having concave, convex and flat profiles to facilitate a rational comparison. The growth of contact area is recorded for a wide range of applied normal force against the fingertip on logging sheets and the same is converted in vector format for facilitating digital measurements. From close examination of the results, it may be noted that the rate of growth of contact area follows the parametric relationship a = cN γ . A weighted least squares fit algorithm is used to formulate the parametric relationship based on experimental data. Further, the contact characteristics of the 3D printed fingertip follows the same pattern of soft neoprene fingertip, and it is well in line with the expected results. Hence, it is evident that 3D printed fingertips could be utilized for handling fragile to hard objects and capable of handling multi-profiled objects in dexterous robotic manipulation. Moreover, complex profiled fingertips can easily be manufactured by 3D printing, and it can be considered as a better alternative for conventionally manufactured anthropomorphic robotic grippers. Practical implications of this research will be highly useful for development of soft-fingered robotic grippers for dexterous robotic manipulations.

Graphite nanopowder was synthesized by mechanical method using ball mill and used as filler in polymer electrolyte film based on Polyvinylidene fluoride (PVDF) for application in natural dye sensitized solar cells (DSSCs). A simple solution cast technique was employed for the preparation of polymer electrolyte film with incorporation of different weight percent (1, 2 and 3) graphite filler along with propylene carbonate and ethylene carbonate as plasticizers. X-ray diffraction and differential scanning calorimetry analysis was carried out to determine the crystallinity of the graphite nanopowder and its glass transition temperature. The film with 2 % weight showed the best ionic conductivity of about 5.63 × 10 −3 S cm −1 . The betacyanin dye from beetroot and chlorophyll dye from spinach leaves was evaluated for the fabrication of dye sensitized solar cell (DSSC). The carboxyl, hydroxyl and porphyrin groups present in these dyes helped in binding the dye with the photoanode of DSSCs.

To further the exploration of perovskite nanowires, TiO 2 @CH 3 NH 3 PbI 3 (TiO 2 @MAPbI 3 ) core–shell nanowire arrays were successfully prepared via immersion and spin-coating methods. Because the shell thickness has a significant influence on the carrier transport capacity of nanowire arrays, different shell thicknesses were obtained by changing the precursor concentration. Subsequently, the relationship between the precursor concentration and shell thicknesses and the resulting properties of the nanowire arrays were investigated. The X-ray diffraction results showed that the prepared nanowire arrays consisted of only MAPbI 3 , TiO 2 , and fluorine-doped tin oxide phases, with no impurities. From the scanning electron microscopy and energy dispersive X-ray spectroscopy results, the MAPbI 3 shell material was successfully coated onto the core layer of the TiO 2 nanowire arrays. In addition, the average size of the core–shell nanowire arrays and the shell thickness were obtained using scanning electron microscopy and related software analyses. The results showed that the shell thickness was the largest (40 nm) when the precursor concentration was the lowest (0.025 mol L −1 ). Ultraviolet–visible spectroscopy showed that when the precursor concentration was 0.025 mol L −1 and the shell thickness was the largest, the nanowire array exhibited the highest absorbance and the smallest band gap, which is conducive to generating more carriers and improving its photovoltaic performance; the J – V curve showed the highest photoelectric conversion efficiency at this concentration and shell thickness. Therefore, it can be inferred that the shell thickness may affect the optical and photovoltaic properties. The relationship between the precursor concentration and thickness as well as the influence of this relationship on the properties of core–shell nanowire arrays should be further explored, to establish a foundation for the use of perovskite nanowires in the photovoltaic field.

The spinel form of cobalt aluminate (CoAl 2 O 4 ) was synthesized by a hydrothermal method in moderate conditions. The synthesized phases were qualitatively and quantitively identified by means of different characterization techniques. The effects of reaction conditions of Co/Al ratio, pH , stirring time, reaction temperature, reaction time and capping agent addition on the color performance and morphology were studied. The capping agents of n -cetyl- n , n , n trimethylammonium bromide (CTAB), 2-pyrrolidinone (PVP), triethylamine (TEA) and oleic acid (OA) were used. The probable reaction mechanism can be explained with the steps of (i) formation of Co–Al–O complexes and (ii) conversion to Co-spinel. In the reaction mechanism, the addition of capping agents improved the conversion of complexes to Co-spinel. The characteristic band values were observed at 550, 595 and 650 nm in the ultraviolet–visible wavelength range, in UV analyses. The lowest b* and the highest BET surface area were determined in the TEA added sample with values of – 37.4 and 16.02, respectively. Layer shaped particles were obtained in CTAB added samples whereas the angled cubic particles were seen in the TEA and OA added samples. The smallest particles were observed in the use of PVP addition to spinel, and the particle size was around 100 nm. The experimental results proved that characteristic properties of prepared samples can be enhanced by the selection of a suitable capping agent.

Amorphous Co 78 Si 8 B 14 alloy, as a new potential catalyst, has hardly been used in the degradation of organic pollutant activated by peroxymonosulfate (PMS). In the study, the degradation performance of Orange II aqueous solution by PMS activated by amorphous Co 78 Si 8 B 14 alloy in a heterogeneous catalytic process was studied at ambient temperature. The effects of initial solution pH , amorphous Co 78 Si 8 B 14 alloy dosage and PMS concentration on Orange II degradation were examined in batch experiments. The results show that decolorization was strongly influenced by initial solution pH , amorphous Co 78 Si 8 B 14 alloy dosage, and PMS concentration. The decolorization rate increased with the increase in pH value from 3 to 6.45. In contrast, it decreased sharply when the pH value of the solution increased from 6.45 to 11. The decolorization rate increased as the amorphous Co 78 Si 8 B 14 alloy dosage and PMS concentration increased. Finally, the potential mechanism of Orange II removal by amorphous Co 78 Si 8 B 14 alloy/PMS system was proposed systematically by comparing with the Co 2+ /PMS system.

We studied the melting temperatures of bismuth and antimony as a function of pressure in this paper because, unlike other solids, melting temperatures are found to fall with increasing pressure. A phenomenological model is proposed to represent the melting temperature as a function of pressure in both solids using Lindemann’s criterion. The computed results are found to be very close to the experimental data. The average absolute percentage relative deviation ( AARD %) in bismuth is 0.012, 0.038 in antimony (set-1) and 0.128 in antimony (set-2). Furthermore, the minimum condition is obtained, which gives the pressure at the minimum melting temperature.

In this paper an interesting alternative for recycling of Li-ion battery cathode and and improving the corrosion resistance of 430 stainless steel is presented. The spent cathode composition has molecular formula approximately LiCoO 2 . The cobalt electrodeposition onto 430 SS was performed using the cobalt bath obtained by spent LiCoO 2 lixiviation. In air atmosphere and high temperatures the metallic cobalt is transformed into a Co 3 O 4 layer that acts as protection against chromium volatilization. This was confirmed by energy-dispersive X-ray spectroscopy and scanning eletron microscopy measurements. Electrochemical impedance spectroscopy measurements, in 0.5 M H 2 SO 4 after thermal treatment at 600, 700 and 800 °C show that the cobalt electrodeposition is efficient in mitigating the effects of corrosion when 430 stainless steel is subjected to high temperatures.