IR@CMERI - The Central Mechanical Engineering Research Institute (CSIR)
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Evaluation of mechanical and frictional properties of CuO added MgO/ZTA ceramics
No full textThe focus of the present work is to investigate the tribological effect of adding CuO as solid lubricant in MgO/ZTA (Magnesia-Zirconia Toughened Alumina) ceramics. Different wt% of CuO (0–5 wt%) have been added in MgO/ZTA ceramics using powder metallurgy process route to study the change in mechanical properties i.e., hardness, fracture toughness and flexural strength, as well as the tribological properties i.e., coefficient of friction (COF) and wear depth, against corundum alumina balls. The addition of CuO shows significant improvement in tribological properties but a diminishment of the mechanical properties. A significant reduction of 53.45% in COF with minimum wear depth is achieved with the addition of 1.5 wt% CuO inside the MgO/ZTA matrix. The improvement in COF and specific wear rate of the composite is observed with increasing sliding velocity due to the presence of uniform patchy layer along with a glossy surface on the wear track. The formation of patchy layer is enhanced with an increase in sliding velocity due to high squeezing and smearing of wear debris. A significant increment in specific wear rate is observed with increasing load due to the delamination process prevailing at the contact surfaces
In situ growth of Co3O4 nanoflakes on reduced graphene oxide-wrapped Ni-foam as high performance asymmetric supercapacitor
No full textHerein, we report an in situ reduction process of GO to rGO on Ni foam during deposition of Co3O4 nanoflakes via ammonia evaporation technique followed by thermal treatment. The synthesis procedure and the design of electrode make it very promising for supercapacitor application. The characteristic electrochemical properties indicate the ‘battery’ type material and supercapattery performances were investigated thoroughly. The electrode exhibited considerably high specific capacity of 1328 C g−1 at 2 A g−1 current density and showed good stability compared to Co3O4 nanoflakes deposited on bare Ni foam. The performance as asymmetric supercapacitor in a two-electrode configuration of Co3O4-rGO/Ni foam also revealed high specific capacitance of 80 F g−1 at current density of 0.1 A g−1 and excellent stability with 94.5% capacity retention after 10,000 cycles. A considerably high energy density of 20 Wh kg−1 at power density of 1200 W kg−1 was achieved for Co3O4-rGO/Ni foam based asymmetric device, confirming the material as a potential candidate for supercapacitor application
Mitigation of Blast Induced Acceleration using open cell natural rubber and Synthetic Foam
No full textIn addition to high pressure generated by explosion, the induced high acceleration can also cause severe injuries to occupants and structural damage, especially in anti-vehicular land mine blast scenario. This problem has not been studied well and only few techniques to reduce the deadly effect of high acceleration are reported in literature. In the present work, the mitigation of blast induced acceleration using add-on layers of open cell natural rubber and synthetic foam on rigidly fixed composite plate has been studied experimentally under increasing blast wave strengths. The blast wave strength was varied by increasing quantity of plastic explosive from 0.150 kg to 0.550 kg. The induced vibration in the composite plate due to impingement of blast wave was measured in terms of acceleration using piezoelectric accelerometer. It was observed that the sharp rising acceleration signals were transformed into a slowly rising and low amplitude signals with the addition of foam. The mitigation of high frequencies and amplitude of acceleration signals was also verified with the fast Fourier transform study. The rubber foam shows better acceleration mitigation than synthetic foam. This study has suggested that the material like rubber and synthetic foam can be used for mitigating the acceleration resulting from the impact of blast wave
PS-Sim: A framework for scalable data simulation and incentivization in participatory sensing-based smart city applications
No full textThe widespread penetration of smartphone has paved the way for a new paradigm of pervasive computing, known as the participatory sensing (PS). In PS, a human user explicitly performs the tasks of sensing and reporting, typically in lieu of incentives. One major limitation with PS is the sparsity of data owing to the lack of active participation, thus inhibiting large scale real-life experiments for the research community. In our preliminary work (Barnwal et al., 2018), we propose a spatio-temporal event occurrence and report generation based data simulation framework called PS-Sim. This paper extends the PS-Sim framework with a novel budget allocation mechanism for incentivizing participants. The allocation mechanism guarantees the presence of a threshold number of active participants and also ensures the reporting of the significant fraction of events for sustainability of PS applications. The simulation environment provided by the PS-Sim framework replicates real participation and event occurrence behaviors, which is expected to enable the domain experts to investigate and assess the requisites (benefits and challenges) of introducing smart city applications. As a part of the evaluation of the budget allocation mechanism, we study its performance under varying effects of reward and participation, and establish its fairness as far as the remuneration of active participants is concerned
Toxic organic solvent adsorption by a hydrophobic covalent polymer
No full textA low cost easy to construct imine-based covalent polymer (CPCMERI-1) has been successfully prepared via a room temperature Schiff-base condensation reaction. Purposeful use of an electron rich naphthalene moiety as a skeletal unit implants hydrophobicity in the polymer. The contact angle of the hydrophobic covalent polymer coated surface has been found to be as high as 128°. The newly developed CPCMERI-1 has high thermal as well as chemical stability due to the presence of extended π–π conjugation of naphthalene and phenyl rings linked through –CH[double bond, length as m-dash]N– bonds. Taking advantage of the high stability factor and hydrophobicities of the covalent polymer, we have performed liquid phase adsorption of benzene and its electron rich, and electron deficient substituents like toluene and nitrobenzene, respectively. CPCMERI-1 selectively adsorbs benzene although it possesses adsorption affinity towards nitrobenzene and toluene. The strong π–π interaction between the benzene and naphthalene moiety of the polymer is responsible for the adsorption. Surface analysis of CPCMERI-1 before and after adsorption of benzene has been investigated which depicts the surface adsorption phenomena of the analyte. The interaction has been further examined by using DFT-D3 study which reveals that benzene interacts with the host napthalene moiety through π–π interaction. Precise experimentation reveals that CPCMERI-1 exhibits better performance than commercially available activated carbon and some recently reported materials towards adsorption of organic solvents like benzene, toluene, nitrobenzene etc. We expect that our work presented here will herald a new type of polymer as CPCMERI-1 may be a useful adsorbent for removing organic pollutants
Water desalination using graphene oxide-embedded paper microfluidics
No full textThe need for the removal of salt constituents is very critical in several downstream processes of biological materials and saltwater purification. Substantial efforts to drive low cost-effective techniques for desalination are ongoing, and it is hopeful that novel nanomaterials could provide useful insight to a new paradigm in salt capturing both in biogenic fluids and complex solutions like seawater. In this report, we demonstrate a microfluidic proof-of-concept for a desalination system, in which graphene oxide deposited on the paper substrate was used to remove salt-ion concentration. Our investigation suggests that the optimal modification of paper with the five-time deposition of graphene oxide (paper@5GO) shows the best salt removal performance with the salt-rejection efficiency of ~ 97.0%. The salt rejection occurs by the phenomenon of surface adsorption on the GO-modified paper membrane which is confirmed by the detailed analytical studies of pre- and post-treatment. The system presented does not require additional energy input in the process and thus would become cost-effective and scalable with high salt removal efficiency which may be useful in bioanalysis and saltwater purification for sustainable development
Effect of Fe3O4‐Decorated N‐Doped Reduced Graphene Oxide Nanohybrid on the Anticorrosion Performance of Epoxy Composite Coating
No full textThe present study explores the synergistic effect of Fe3O4 and heteroatom doped reduced graphene oxide (rGO) nanohybrid on anti‐corrosion performance of epoxy composite coating. In this connection, Fe3O4 nanoparticles were decorated over nitrogen doped rGO (Fe3O4‐NRG) and characterized by Fourier transform infrared spectroscopy (FT‐IR), Raman spectroscopy, X‐ray diffraction (XRD), X‐ray Photoelectron spectroscopy (XPS), and Thermogravimetric analysis (TGA). This approach to modulating the surface properties of graphene and hence the interaction with polymer matrix were quite distinct from traditional surface functionlization or decoration in a sense that the doped nitrogen atom facilitate the growth of Fe3O4 particles and at the same time augmented the interaction of rGO with polymer matrix. The prepared nanohybrid was dispersed in epoxy matrix through mechanical mixing and coated over mild steel surface via spin coating technique. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) study revealed superior anti‐corrosion performance of Fe3O4‐NRG/epoxy coating in 3.5 wt% NaCl solution. The corrosion inhibition was found to improve by ∼ 98.5% with 0.5 wt% loading of Fe3O4‐NRG. We believe that this simple solvent free approach to prepare composite coating can be exploit for practical application and thus deserves special attention.
Effect of thermal annealing on the physico-chemical and tribological performance of hydrophobic alkylated graphene sheets
No full textThere has been increasing interest in modification of graphene for application in the field of lubrication to reduce friction and wear on moving mechanical assemblies. In this work, a facile and effective surface modification approach of graphene oxide (GO) sheets by octadecyl amine followed by annealing at 150 °C to form superhydrophobic functionalized GO (f-GO) has been demonstrated. We also validated the effect of temperature on the structural and wetting behaviour of alkylated sheets with increase in annealing temperature (450 °C). The restoration of graphitic conjugated nanosheets of f-GO and emergence of superhydrophobicity in modified graphene (f-GO150) and structural alteration in f-GO450 after thermal treatment were confirmed by UV-Vis, FT-IR, and Raman spectroscopy, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) analysis and water contact angle (WCA) measurements. The thermal annealing at 150 °C distorted the long hydrocarbon chains on f-GO that reduced the surface energy and increased the surface roughness, and f-GO exhibited a high WCA of ∼158.8°. A further increase in annealing temperature to 450 °C reduced the hydrophobicity (WCA ∼ 92.8°) as most of the attached carbon chains were removed from the graphitic sheets. The dynamic light scattering technique was used to measure the particle size in an oil suspension and the particle size distribution was found to be in correlation with the wetting behaviour of the particles and also suitable for the effective control of tribological behaviour in sliding lubrication. We investigated the load bearing ability of pristine and annealed f-GO under both ambient and lubricated conditions in varying pressure regimes with a pin/ball-on-disc tribometer. The superhydrophobic f-GO150 was found to decrease friction and wear in dry/lubricated contacts by forming a thicker and continuous film on the sliding interface, which is supported by FESEM/EDX and corresponding Raman analysis
Cd(II) Based Coordination Polymer Series: Fascinating Structures, Efficient Semiconductors, and Promising Nitro Aromatic Sensing
No full textThree Cd(II) based coordination polymers (CPs) (1–3) are designed using 3-aminoquinoline and 5-aminoquinoline based Schiff base ligands and thiocyanate and dicyanamide as bridging ligands. Pseudohalide linkers play a crucial role in the architecture of the CPs. These compounds are prepared under an ambient condition with high yield. The I–V characteristics of the 1–3 based thin film devices (Al/complex interface) under dark and illumination conditions are nonlinear rectifying nature, which is the signature of a Schottky barrier diode (SBD). The rectification ratio (Ion/Ioff) of the SBDs under dark condition at ±2 V has been obtained as 16.41, 15.48, and 14.73 and under illumination conditions; the same has been evaluated as 67.18, 46.23, and 37.69 for 1, 2, and 3, respectively. The photoresponsivity of the device is found to be 5.52, 2.89, and 2.54 for 1, 2, and 3 based SBDs, respectively. The enhancement of conductivity under photoilluminated conditions depends on π-electron donor capacity of Schiff base ligands and the length of pseudohalide linkers of 1–3. Again, depending on the binding fashion of the coordinating ligands, three CPs (1–3) exhibit different selectivity toward nitroaromatic sensing. In 2,4,6-trinitrophenol (TNP) sensing, CPs follow the order 3 > 2 > 1. CP 3 has the highest quenching constant among the other two CPs along with a prominent selectivity and lowest detection limit in response to TNP
Estimation of dilution in laser cladding based on energy balance approach using regression analysis
No full textLaser cladding is a complex manufacturing process involving more than 19 variables related to laser source, workpiece movement, powder-substrate material combinations, clad geometry, powder flow dynamics, shrouding gas flow and so on. Significant research efforts have been directed to analytical-numerical-empirical modelling of laser cladding and also in-process monitoring and control of the process. Still, due to complicated physics there is a dearth of simple analytical model for estimation of dilution in laser cladding. Its experimental measurement requires suitable micrographs of the clad cross section perpendicular to the clad path. This is a time-consuming and destructive way of measurement. Numerical models are time consuming to evaluate and hence not suitable for fast decision making or real-time control implementation. The analytical models available, despite having many approximations, are a little complicated, require fair amount computer programming and often need suitable prior guessing of range of output parameters for adjustment of constant values in the models. This poses some challenges for use and having an intuitive guidance, for a beginner/unskilled operator. Besides, their complexity may erect barrier in the way of their implementation for real time monitoring and control. This work proposes a simple linear regression model, formed based on energy balance approach, to estimate dilution in laser cladding. After fitting to a set of data, within a suitable process parameter-window, for a particular clad-substrate material combination, this model can estimate dilution as a function of input/easily measureable parameters, viz. laser power, scan speed, clad width and clad height. The model fitted well to the experimental data taken from literature