IR@CMERI - The Central Mechanical Engineering Research Institute (CSIR)
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Sintering metal injection molding parts of tungsten-based steel using microwave and conventional heating methods
No full textIn recent years, the near net shape metal injection molding process combines desirable features of plastic injection molding and powder metallurgy processes to gain high strength-to-weight ratio for manufacturing complex-shaped parts. The metal injection molding process consists of mixing, molding, debinding, and sintering. Microwave processing has attracted much attention in global research because of its unique features such as its ability to heat and sinter a wide variety of metals and its significant advantages in energy efficiency, processing speed, and compatibility. Also, it presents few environmental risks and can produce refined microstructures. The injected samples to be sintered are composed of fine tool steel metal powder and binders, stearic acid, paraffin wax, low-density polyethylene, and polyethylene glycol (600). In recent years, microwave-assisted post-treatment is considered a novel method for processing green parts. In this work, the green parts are subjected to high-intensity microwave fields which operate at a frequency of 2.45 GHz. Metal injection molding compacts were sintered using multi-mode microwave radiation. The sintering of a metal injection molding compact by microwaves has hardly been reported. The metal injection molding compact showed better results than those produced by sintering with conventional heating. This study evaluates the effect of conventional sintering and microwave sintering on mechanical properties. By optimizing the sintering process, increased sintered hardness, a more homogeneous microstructure, and greater shrinkage were obtained using microwave-assisted sintering
Electrodeposited SiC-graphene oxide composite in nickel matrix for improved tribological applications
No full textElectrodeposited nickel matrix embedded with silicon carbide (SiC) and graphene oxide (GO) particles were prepared through pulsed electro-deposition. Taking advantages of the excellent tribo-mechanical properties of GO and SiC, excellent anti-wear and frictional properties are expected when SiC and GO particles were embedded in the Ni matrix. For this purpose, nano-SiC particles were first grafted within Ni matrix to engineer Ni–SiC coatings. Further GO particles were added to the Ni–SiC bath to prepare Ni–SiC-GO composite coating. The structure, composition, and morphology of the Ni–SiC and Ni–SiC-GO were characterized by Raman spectroscopy, XRD, AFM, FE-SEM, EDS and water contact angle measurements. The results revealed that SiC and GO particles were successfully incorporated in the Ni matrix. Addition of GO to the composite matrix reduced the water contact angle from 69.2° to 58.9°, thereby confirming hydrophilic nature of Ni–SiC-GO due to the presence of polar oxygen functionalities. The tribological tests of the coatings were studied under dry sliding condition using a linear reciprocating ball on plane sliding microtribometer with varying sliding speed and the wear mechanisms of these coatings were also investigated. The addition of SiC into the Ni matrix enhanced its wear resistance with a poor frictional behaviour. However, incorporation of GO into Ni–SiC-GO coatings reduced the coefficient of friction (COF) substantially with an adaptable anti-wear behaviour. Increase in sliding speed was found to have a detrimental effect in the wear and friction behaviour of the coatings. The superior tribological properties of the Ni–SiC-GO were attributed to the synergistic effects of SiC and GO. This work offers a unique methodology to design durable nanocomposite coatings for industrial tribological applications
Experimentation modelling and optimization of electrohydrodynamic inkjet microfabrication approach: a Taguchi regression analysis
No full textElectrohydrodynamic (EHD) inkjet is a modern non-contact printing approach, which uses a direct writing technology of functional materials to achieve micro/nanoscale of printing resolution. As an alternative to conventional inkjet technology, the goal of the EHD inkjet printing is to generate uniformly minimized droplets on a substrate. In this study, the effects of applied voltage, standoff height and ink flow rate on droplet diameter formation in EHD inkjet printing process were analysed using Taguchi methodology and regression analysis. Several experiments were carried out using an L27 (313) orthogonal array. Based on signal to noise (S/N) ratio and mean response, optimal droplet diameter was achieved. The analysis of variance (ANOVA) was used to find the significance and percentage of contribution of each input parameter along with their interaction on the output droplet diameter. Analysis of the results revealed that the ink flow rate was the dominant factor that affected the droplet diameter mostly. The effect of the applied voltage is significant until regular ejection starts. It helps reduce droplet diameter more than five times compared with its initial droplet diameter in the absence of the electric field. A confirmation test was carried out with a 90% confidence level to illustrate the effectiveness of the Taguchi optimization method. Both linear and quadratic regression analysis were applied to predict the output droplet diameter. The predicted result from the model and actual test results are very close to each other, justifying the significance of the models
Low pH treatment of starch industry effluent with bacteria from leaf debris for methane production
No full textCornstarch industry generates a huge amount of acidic effluent, that is, 5-11 M3 /Mt grinding, with a high load of chemical oxygen demand, 6000-19000 mg/L. The acidic effluent requires neutralization making the treatment process expensive. Methanogenesis under the acidic environment (pH 5-5.5) can reduce the cost of operation as well as treatment time. This research focuses on the evaluation of the optimum condition of COD reduction and methane generation simultaneously from leaf debris sludge using Box-Behnken model. Three 1 L bioreactors were seeded with 5000-10000 mg/L inoculum and operated at different pH 4.0-7.0 for 72 hr up to 10 cycles. The production of methane was found maximum 2980 ml after treating the wastewater from the starch industry at pH 5.57 and 9612.9 mg biomass load at 62.4 hr. The high reduction rate of around 97% shows there is ample opportunity for further research on low pH treatment of waste along with recovery as methane. PRACTITIONER POINTS: The low pH tolerant methanogenic bacteria are promising and are isolable from various natural resources. The low pH tolerant methanogens was able to remove 97% COD from starch industry effluent at pH 5.57. The recovery of methane was 2980 ml from 9612 mg/L COD which is at per with present treatment system thus provides cost effective alternatives
Sensitive and Selective in Vitro Recognition of Biologically Toxic As(III) by Rhodamine Based Chemoreceptor
No full textArsenic induced cleavage of the spirolactam ring of a cleft shaped electronically enriched rhodamine based chemoreceptor molecule 3′,6′-bis(ethylamino)-2-((2-hydroxy-5-methylbenzylidene)amino)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one (PBCMERI-23) has been reported in the present work. The developed easy, instant and economic luminescent probe instigate toward unlocking the selectivity for a specific lethal water contaminant such as As(III) from aqueous media up to a level of 0.164 ppb (beyond the critical limit of the World Health Organization). PBCMERI-23 displays a 2-fold optical response (chromogenic, colorless to reddish pink; fluorogenic, non-blooming fluorescence to yellow emission) via the ring opening phenomenon of the developed chemoreceptor. Owing to the remarkable photophysical and structural properties of the synthesized probe, the recognition event has been turned on in the low energy region. Detailed experimental techniques further supported by theoretical evidence establishes the plausible mechanistic course of the host:guest interaction. The spectrophotometric response of the developed chemoreceptor PBCMERI-23 turns out to be reversible with incremental addition of a stoichiometric amount of I–. The optical recognition phenomenon has been further synchronized and interfaced with molecular logic gate to molecular electronics. To explicate the bioapplicability of PBCMERI-23, varying cell lines, viz., pollen grains of Allamanda puberula (Aapocynaceae), radiator plant (Peperomia pellucida), Poecilia reticulata, Danio rerio, and squamous epithelial cells have been monitored. The probe displays sparkling yellow illumination when the cells were visualized under fluorescence microscope, which confirms its cell permeability and is a biomarker toward intracellular investigation and bio-imaging of As(III). Furthermore, the chemoreceptor has enormous capability in detecting As(III) from a series of wastewater specimens with varying pH, which makes the present chemoreceptor PBCMERI-23 unique of its kind
Effect of processing routes on structure-property correlationship of ADC 12 Al alloy
No full textThe present work focuses primarily on the effect of processing routes on structure-property correlationship of ADC 12 Al alloy. Both conventional processing (Gravity cast and pressure die cast) and Semi Solid processing techniques (cooling slope and Rheo-Pressure Die Cast; RPDC) were attempted to bring out the correlationship between their microstructures and mechanical properties of ADC 12 Al alloy. Gravity cast experiment was done on ingots of ADC12 Al melted in an resistance furnace and poured at temperature 585 °C in a copper mould. In the Pressure Die-Casting process, ingots of ADC12 Al alloy were melted in an resistance furnace and the liquid metal was poured in the mould of the pressure die casting system. Semi-solid metal processing was carried out using cooling slope experiments in a developed in-house set up and effect of rheocasting on the semi solid microstructure was studied. Rheo pressure die cast experiments were carried out in an integrated set-up of cooling slope and pressure die-cast system. The obtained result of gravity cast material reveals dendritic morphology of primary Al phase and elongated eutectic phase; upon using pressure in a pressure die cast system, the structure of primary Al phase changes to large size dendrites along with rosette shaped morphology. The cooling slope technique to generate semi-solid structure yields nearly globular and fine grains; whereas the rheo pressure die casting experiments reveal nearly globular shape primary Al exhibit that distribute relatively uniformly in the matrix compared to the all three above the processing routes. From The best mechanical properties are also obtained in Rheo-pressure die cast system with tensile strength (223 MPa), elongation (6.5%), and hardness (87 VH) compared to all other processing routes. Explanations of fracture micro mechanisms are supplement to the investigation
“Naked-eye” detection of CN− from aqueous phase and other extracellular matrices: an experimental and theoretical approach mimicking the logic gate concept
No full textHerein, a naphthaldehyde-hydrazine-based colorimetric chemosensor (NDNPH) ((E)-1-((2-(2,4-dinitrophenyl)hydrazono)methyl)naphthalen-2-ol) was designed, synthesised and evaluated for target-specific anion detection through the H-bonding mechanism. The chemosensor exhibited high selectivity towards lethal anions, such as CN−, with a 1 : 1 binding stoichiometry and a 1.2 × 107 M−1 binding constant. The NDNPH sensor showed high selectivity towards CN− with a distinct naked eye colour change from light yellow to purple. The detection limit in the aqueous phase was calculated to be as low as 1.26 μM, which was much lower than the permissible limit. The NDNPH sensor was equally responsive in different biological matrices such as fresh bovine serum and human blood plasma. This shows the bioapplicability of the chemosensor, which is of immense importance in analytical domains in the modern era. In addition to several spectroscopic studies, the DFT studies together with the electrostatic potential surface analysis and Loewdin spin population calculation confirmed the binding behaviour of the sensor molecule with the targeted analyte. Furthermore, the reversible UV-vis responses of the synthesized chemosensor NDNPH towards CN− and Cu2+ could mimic several molecular logic functions and hence were used to fabricate several complex electronic circuitries based on Boolean Algebra. Moreover, “test strips” based on the NDNPH sensor were fabricated, which might act as a conventional and efficient cyanide detection kit for real-field detection without the need for additional instruments by virtue of the “Dip-Stick” approach. In summary, this simple, cost-effective, azomethine-based simple Schiff base molecule detects biologically lethal anions (CN−) in various biological matrices with real-field application in analytical and engineering sciences
3D Printed Sensors for Biomedical Applications: A Review
No full textThis paper showcases a substantial review on some of the significant work done on 3D printing of sensors for biomedical applications. The importance of 3D printing techniques has bloomed in the sensing world due to their essential advantages of quick fabrication, easy accessibility, processing of varied materials and sustainability. Along with the introduction of the necessity and influence of 3D printing techniques for the fabrication of sensors for different healthcare applications, the paper explains the individual methodologies used to develop sensing prototypes. Six different 3D printing techniques have been explained in the manuscript, followed by drawing a comparison between them in terms of their advantages, disadvantages, materials being processed, resolution, repeatability, accuracy and applications. Finally, a conclusion of the paper is provided with some of the challenges of the current 3D printing techniques about the developed sensing prototypes, their corresponding remedial solutions and a market survey determining the expenditure on 3D printing for biomedical sensing prototypes
A Generalized Discontinuous PWM Scheme for Three-Level NPC Traction Inverter With Minimum Switching Loss for Electric Vehicles
No full textA discontinuous pulsewidth modulation (DPWM) strategy for three-level neutral-point-clamped (NPC) traction inverter drive for electric vehicles (EVs) with minimum switching loss for the full power factor (PF) range is developed and presented in this paper. Considering the dynamic loading conditions in an EV propelled by an induction motor (IM), the discontinuous modulation strategy is generalized to obtain minimum switching loss for a wide variations in load PF and modulation depth. The dynamic operating conditions in EV may render frequent unbalances in dc-link capacitor voltages in NPC inverter. It is demonstrated that the addition of an appropriate offset signal with the reference discontinuous signals generates compensating neutral current in the right direction, which can be used to mitigate existing unbalance in two dc-link capacitor voltages. Minimum switching loss at variable PF is attained by positioning the nonswitching clamped regions of the reference auxiliary signals according to the load PF. The effectiveness of the proposed scheme for a wide range of torque/speed variations is studied through simulation by developing a MATLAB/SIMULINK model of an IM traction inverter drive with field-oriented control strategy for closed loop control. Finally, the modulation scheme is validated through experimentation in a small-scale prototype NPC inverter with motor loads
All-circular hole microstructured fiber with high birefringence and low confinement loss
No full textAn air–silica microstructure optical fiber of ultrahigh birefringence of the order ∼10−2 and low confinement loss is proposed. The birefringence is achieved by axial anisotropy introduced in the fiber geometry by the preferred arrangement of circular air holes of different sizes in the cladding structure. Vital properties of the microstructure fiber, e.g., birefringence, confinement loss, dispersion, and walk-off, have been studied by employing numerical solutions through the finite element method. These findings should be useful for the fabrication of the proposed microstructure optical fiber