Browsing by Author "Rahman, M.R."

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A Flexible and Biodegradable Graphene Oxide Antenna Sensor for Monitoring Subsoil Health
(American Chemical Society, 2024) Singh, V.P.; Kandasamy, K.; Rahman, M.R.
In this paper, a flexible graphene oxide-based antenna sensor is designed on the biodegradable substrate. It resonates at a frequency of 3.92 GHz. The flexible sensor is used in assessing water content in sandy loam subsoil near the Arabian Sea from the Western Ghats in India. The volumetric water content (VWC) of dry soil varies between approximately 0.06 VWC m3 m-3 to 0.7 VWC m3 m-3. The antenna sensor exhibits a linearity of 92.02% and a sensitivity of 402.6 MHz/VWC(m3 m-3). The limit of detection (LOD) and limit of quantification (LOQ) of the antenna sensor are 0.75 VWC and 2.5 VWC m3 m-3. The sensor is beneficial for examining soil water to enhance crop productivity for precision agriculture. © 2024 American Chemical Society.
A single step unique microstructural growth of porous colossal dielectric constant titanium oxide
(Springer Verlag service@springer.de, 2019) Meti, S.; Hosangadi Prutvi, S.P.; Rahman, M.R.; Bhat K, U.K.
New microstructure of TiO 2 grown in hydrothermal process is reported on. The influence of hydrothermal process parameters, such as heating temperature, on growth dynamics is also reported. The improvement in surface area and crystallinity are reached by the hydrothermal process, as compared to other growth techniques. The synthesized TiO 2 is characterized by XRD technique and subjected to Rietveld analysis. The results indicate that the obtained TiO 2 is of tetragonal structure. The results of other characterization techniques such as micrography, Raman spectroscopy and TGA are also reported. The obtained TiO 2 is tested for its electrical properties and it shows good dielectric strength in the flat band region from 40 Hz to 1 MHz. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
A study on magnetorheological and sedimentation properties of soft magnetic Fe58Ni42 particles
(Elsevier B.V., 2022) Aruna, M.N.; Rahman, M.R.; Joladarashi, S.; Kumara, H.; Meena, S.S.; Sarkar, D.; Umesh, C.K.
In this study, the samples with two volume fractions (ϕ) of Fe58Ni42 (permalloy) i.e. (ϕ1 = 25 and ϕ2 = 30 %) were used as magnetic particles, silicone oil as a carrier fluid, and aluminium disterate as an additive. As received Fe58Ni42 particles surface morphology and composition of the Fe58Ni42 were investigated using field emission scanning electron microscopy (FESEM) coupled with energy dispersive spectroscopy (EDS), respectively. The X-ray Diffraction (XRD) structural information analysis confirmed Fe58Ni42 particles have a face-centered cubic phase, corresponding with the result of the high resolution transmission electron microscopy (HRTEM) characterization technique. The magnetorheological properties were tested via rotational rheometer at four different magnetic field strengths. The results show that sample PMRF-30 has a maximum shear stress, shear viscosity, and dynamic modulus greater than the PMRF-25 sample. In addition, experimental shear stress flow curves are well fitted with Herschel-Bulkley rather than Bingham and Casson rheological models. The permalloy based magnetorheological fluid (PMRF) samples were prepared with a 25 % volume fraction and a 30 % volume fraction of permalloy particles with a sample abbreviation of PMRF-25 and PMRF-30, respectively. Furthermore, the sedimentation stability of suspensions of both the samples was observed using visual inspection. This method result shows the sedimentation ratio with respect to time of 72 h was 31 % and 29 %, respectively. © 2022 Elsevier B.V.
A study on solubility of bismuth cations in nickel cobalt ferrite nanoparticles and their influence on dielectric and magnetic properties
(Elsevier Ltd, 2023) Patil, S.; Meti, S.; Kanavi, P.S.; Bhajantri, R.F.; Anandalli, M.; Mondal, R.; Karmakar, S.; Muhiuddin, M.; Rahman, M.R.; Kumar, B.C.; Hegde, B.G.
In this work, a low temperature (∼600 °C) solution combustion technique is employed for the synthesis of Ni0.5Co0.5BixFe2-xO4 (NCBFO, where x = 0.0, 0.05, 0.1, 0.15, & 0.2) nanoparticles with crystallite size variation of 17–22 nm. The X-ray diffraction (XRD) technique is used to confirm the formation of cubic spinel phase of Bi3+ doped (for x ≤ 0.05 samples) nickel–cobalt ferrite (NCFO) nanoparticles. The increase in bismuth substitution (x > 0.05) results in the formation of the Bi2O3 along with the NCFO structure, which results in the reduction of binding energy and is confirmed by the XRD and X-ray photoelectron spectroscopy (XPS) techniques. From the Raman spectra, the change in the intensities of the peaks is observed due to the variation of Bi3+ in NCFO matrix. Due to increasing cation concentration and electronegativity, the FTIR absorption band shifts toward the lower wave numbers. Dielectric measurements were carried out to examine the charge transport behavior and electric conduction mechanism. The FESEM images shows the non-magnetic bismuth atoms are diffused into the NCFO nanoparticles. From the vibrating sample magnetometer (VSM) analysis, it is observed that saturation magnetization, remanent magnetization, coercivity and squareness ratio are found to be maximum for x = 0.15 NCBFO sample. The high coercivity (Hc = 916.8 Oe) for the x = 0.15 sample indicates the hard ferromagnetic behaviour of the samples. © 2023 Elsevier B.V.
Assessment of triboelectricity in colossal-surface-area-lanthanum oxide nanocrystals synthesized via low-temperature hydrothermal process
(Springer, 2021) Meti, S.; Hosangadi Prutvi, H.P.; Rahman, M.R.; Bhat, K.U.
Triboelectric nanogenerators (TENGs) have marked their applications in various fields, most importantly, in medical devices. The electrical output of the TENGs mainly concentrated on parameters such as electrode separation distance, applied mechanical pressure, surface charge density, and overlapping surface area. The surface area of the active layer in TENGs plays a crucial role. Given this, the present contribution is the first report on the utilization of lanthanum oxide (La2O3) as an active material with a large surface area (~ 72.33 m2/g) in TENGs. The nanocrystals of La2O3 have been successfully embedded into TENGs architecture through a high-quality screen-printed film with a Teflon-counter surface. The in-house test-rig of TENGs resulted in an output open-circuit voltage of 120 V and a short-circuit current of 23.7 ?A. Further, the maximum power density is 7.125 W/m2 at an external load resistance of 30 M?. These results suggest that La2O3 is a suitable contender in various self-powered devices. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Characterization study and recovery of copper from low grade copper ore through hydrometallurgical route
(Elsevier B.V., 2022) Mohanraj, G.T.; Rahman, M.R.; Arya, S.B.; Barman, R.; Krishnendu, P.; Meena, S.
Characterization studies were conducted on low grade copper ore with the aid of standard approaches. The Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) study specifies the semi-quantitative data of qualitatively analyzed chemical elements present in the ore sample. Optical Microscopy (OM) and X-Ray Diffraction (XRD) endorse the presence of chalcopyrite (CuFeS2) and pyrites along with other different mineral phases in the ore sample. Thermo Gravimetric Analysis (TGA) and Mossbauer spectroscopy studies confirm the formation of CuO and Fe2O3 after roasting at 700 °C. The better copper recovery from low grade copper ore was achieved through optimized leaching parameters. It was found that the particle size of −63+53 µm can be leached up to 94.96 % of copper using a lixiviant reagent mixture (30 vol. % hydrogen peroxide and 0.5 M sulfuric acid) under magnetic stirring for 30 min at a constant speed of 300 rpm, by keeping the liquid/solid (L/S) ratio at 20/2 ml/g. Moreover, the solvent extraction process works well with the pregnant leach solution, whereby, 98.9 % of copper extraction is possible, and the loading time is less than a minute. Meanwhile, 93.91 % of overall copper extraction efficiency was achieved through optimized leaching parameters and solvent extraction method. © 2021
Chemical free synthesis of graphene oxide in the preparation of reduced graphene oxide-zinc oxide nanocomposite with improved photocatalytic properties
(Elsevier B.V., 2018) Meti, S.; Rahman, M.R.; Ahmad, M.I.; Bhat, K.U.
In the present investigation, the reduced graphene oxide – zinc oxide (rGO-ZnO) was prepared by rapid microwave-assisted hydrothermal technique. The chemical free graphene oxide (GO), synthesized by Tang Lau technique, was used in the preparation of rGO-ZnO nanocomposite. The GO gets reduced to rGO during microwave irradiation and provides the necessary nucleation site for the ZnO nanorods to grow in [0 0 0 1] direction. These ZnO nanorods were completely wrapped with rGO sheets, confirmed by the synchrotron XRD and TEM techniques. The phases and cell parameters were calculated by Rietveld method. The prepared composite was used for the photodegradation of methyl orange (MO) dye from water under UV light. Investigation revealed that the incorporation of rGO into the ZnO increased the photodegradation ability of the bare ZnO. The performance of the composite is also compared with the rGO-ZnO nanocomposite, where rGO was prepared by Hummer's method. rGO obtained from Tang Lau method formed stable and efficient composite with ZnO and exhibited higher activity compared to the composite, wherein rGO was prepared from conventional Hummer's method. Under UV light, the ZnO liberates photoelectrons which reacts with surface oxygen to form superoxide radicals (O ? 2 ) and (OH ? ) in the water medium. The rGO nanosheets could reduce the charge recombination during the reaction. The active species adsorbs the MO molecules and degrades into CO 2 , H 2 O and other byproducts. More than 3.5 times increase in the rate constant was observed for rGO-ZnO compared to the bare ZnO. © 2018 Elsevier B.V.
Colossal dielectric permittivity of Nylon-6 matrix-based composites with nano-TiO2 fillers
(Springer, 2020) Meti, S.; Bhat K, U.K.; Rahman, M.R.
Herein, the nanocomposite films of Nylon-6 with reinforced nano-TiO2 were explored for their charge storage capacity. The high dielectric constant (?) of TiO2, along with its compatibility with Nylon-6, formed the basis for the present study. TiO2 nanoparticles were synthesized initially using hydrothermal technique. The microscopic uniformity and anatase-phase purity of the TiO2 nanoparticles were confirmed with the help of morphological and structural investigations. The effect of weight fraction of TiO2 in Nylon-6 was investigated to understand the robustness of the fabricated nanocomposites. The composite films with 5, 10 and 20 wt% of TiO2 in Nylon-6 matrix were prepared, and their dielectric behavior was explored by fabricating capacitors with parallel plate architecture. The composite film with 20 wt% TiO2 showed the highest dielectric parameters. The nanocomposite films have the exceptional dielectric quality with ? ~ 124 and low dielectric loss of 0.51 at 1 kHz. The colossal dielectric nature along with minimum sophistication in the film fabrication process makes the present nanocomposite to be a potential candidate for the various electronic devices. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Complex impedance spectroscopy properties of Fe3BO6 nanocrystallites prepared by combustion method
(2019) Kumari, K.; Ramteke, R.; Rahman, M.R.
In this investigation, we report a part of our work on Impedance spectroscopy of Fe3BO6 nanoceramics prepared by a selfcombustion of a solid precursor mixture of 60Fe2O3-40B2O3 using camphor as a fuel in ambient air. A single phase compound Fe3BO6 of an orthorhombic crystal structure with Pnma space group and average crystallites size D = 42 nm is analyzed from the X-ray diffractogram. The Z?-value decreases with a shift in the peak frequency towards the higher side with rise in temperature arises possibly due to the presence of dipolar response in the material, which is in good agreement with the observation of complex impedance data. Temperature dependent impedance describes Fe3BO6 to be an ionic conductor; with activation energy (Ea) value0.73 eV. The Ea-values so obtained for the dielectric relaxation from the tp-values suggests a conduction mechanism involving the polaron hopping. � 2019 Elsevier Ltd. All rights reserved.
Complex impedance spectroscopy properties of Fe3BO6 nanocrystallites prepared by combustion method
(Elsevier Ltd, 2019) Kumari, K.; Ramteke, R.; Rahman, M.R.
In this investigation, we report a part of our work on Impedance spectroscopy of Fe3BO6 nanoceramics prepared by a selfcombustion of a solid precursor mixture of 60Fe2O3-40B2O3 using camphor as a fuel in ambient air. A single phase compound Fe3BO6 of an orthorhombic crystal structure with Pnma space group and average crystallites size D = 42 nm is analyzed from the X-ray diffractogram. The Z?-value decreases with a shift in the peak frequency towards the higher side with rise in temperature arises possibly due to the presence of dipolar response in the material, which is in good agreement with the observation of complex impedance data. Temperature dependent impedance describes Fe3BO6 to be an ionic conductor; with activation energy (Ea) value0.73 eV. The Ea-values so obtained for the dielectric relaxation from the tp-values suggests a conduction mechanism involving the polaron hopping. Â© 2019 Elsevier Ltd. All rights reserved.
Cost effective synthesis of sulfur and nitrogen co-doped graphene aerogel and application in binder free supercapacitor
(American Institute of Physics, 2024) Muhiuddin, M.; Khan, A.Z.; Devi, N.A.; Bharadishettar, N.; Meti, S.; Siddique, A.B.; Bhat K, U.; Akhtar, W.; Rahman, M.R.
Incorporating heteroatoms into graphene lattice results in enhanced electrical conductivity and electrochemically active sites and has significant importance in developing high-performance supercapacitors. In this study, sulfur and nitrogen co-doped graphene aerogel is synthesized via hydrothermal technique followed by a simple but effective freeze-thawing and ambient pressure drying process (referred to as SN-GA). The process requires low-cost raw materials and cost-effective equipment without the utilization of any special instrument that operates at ultra-low temperatures, under high pressure, or vacuum environment. Ammonium sulfate [(NH4)2SO4] and ethylenediamine are used as a source of sulfur and nitrogen and as a reducing agent. (NH4)2SO4 with different molarities (0, 12, 24, and 36 mM) are used to synthesize four different aerogel samples marked as GA, SN-GA1, SN-GA2, and SN-GA3. The electrode is prepared using an SN-GA2 sample, exhibiting an outstanding specific capacitance of 244 F g−1 at an applied current density of 1 A g−1 with almost 98.5% Coulomb efficiency. Furthermore, based on the SN-GA2 sample, the symmetrical supercapacitor is fabricated, displaying an energy density of 18.14 Wh kg−1 at a power density of 498.4 W kg−1. Hence, SN-GA2 renders a promising material for supercapacitor applications. © 2024 Author(s).
Design and fabrication of optimized magnetic roller for permanent roll magnetic separator (PRMS): Finite element method magnetics (FEMM) approach
(Elsevier B.V., 2021) Mohanraj, G.T.; Rahman, M.R.; Joladarashi, S.; Hanumanthappa, H.; Shanmugam, B.K.; Vardhan, H.; Rabbani, S.A.
In the present work, an attempt has been made to develop a PRMS in a cost effective and environmental friendly way through FEMM analysis of magnetic roller (active part of PRMS). The FEMM analysis indicates that, the optimized magnetic roller having magnet-to-steel disk thickness ratio of 5 mm: 2.5 mm was proved to be gainful in beneficiating paramagnetic minerals due to the best magnetic field value from the roller surface that is, 0.89 to 2.59 T. Prediction analysis was performed on FEMM data using artificial neural network (ANN) modelling technique. Further, the design calculations of lab scale PRMS in terms of power requirements and belt tensions were addressed. The fabricated PRMS was tested on paramagnetic mineral (hematite ore) assayed 51.24% of Fe, 10.20% of SiO2, and 2.98% of Al2O3 for different roller speeds and the belt thickness. The result showed that, at 0.5 mm belt thickness with 180 rpm roller speed the fabricated lab scale PRMS works well in terms of improvement in the Fe content up to 59.5% at the concentrate along with the Fe recovery of 71.41%. The obtained results suggest that, the FEMM analysis is more suitable to optimize the effective magnetic roller for the PRMS. © 2021 The Society of Powder Technology Japan
Development and characterization of Cu/MWCNT composite prepared by electrodeposition technique
(American Institute of Physics Inc. subs@aip.org, 2020) Bharathi, K.D.; Rahman, M.R.; Choudhary, S.; Arya, S.B.
Multi walled carbon nanotube (MWCNT) reinforced copper matrix (Cu/MWCNTs) nanocomposites were successfully fabricated by electrodeposition technique using DC-Power source. With various concentrations of CNT, microstructural, micro hardness, tensile stress, and Electrochemical studies were done. The Cu/MWCNT nanocomposites at the highest concentration of 450mg/l exhibited âˆ¼25% and 47% higher tensile strength and Vickers microhardness respectively than that of the pure Cu. Electrochemical AC-impedance and Tafel polarisation analyses confirmed that the corrosion potential (Ecorr) and corrosion current density (icorr) of nanocomposites at 450 Â«mg/l obtained about 190 Â»mV SCE and 1.09 Î¼ A/cm2 respectively in 3.5 wt.% NaCl solution. Â© 2020 Author(s).
Diluted magnetism in Mn-doped SrZnO2 single crystals
(American Institute of Physics Inc., 2013) Rahman, M.R.; Koteswararao, B.; Huang, S.H.; Kim, K.; Chou, F.C.
We have investigated the magnetic properties of Mn- and Cu-substituted SrZnO2 single crystals (SrZn1-xMnxO2 and SrZn1-xCuxO2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the low-percentage (x = 0.01) of Mn-substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab-plane yield anisotropic behavior with Curie-Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn at high temperatures, similar to the Mn-doped ZnO and Fe-doped BaTiO3. In contrast, the SrZn0.99Cu0.01O 2 crystal shows paramagnetic behavior down to 2 K. © 2013 AIP Publishing LLC.
Effect of temperature on wear and friction performance of WC-Co and Cr3C2 reinforced with 17-4PH Fe-based composite coatings
(Springer Science and Business Media Deutschland GmbH, 2024) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.; Rahman, M.R.
Surface protection is crucial in industrial equipment and tools to prevent wear and friction in harsh environments, particularly at high temperatures, where anti-friction coatings are essential for optimal performance. The present research investigates the tribological properties of high-velocity oxy-fuel sprayed coatings of 17-4PH stainless steel reinforced with tungsten carbide and chromium carbide powders. The coatings are deposited onto a maraging steel substrate. A dry sliding wear test was performed using an alumina ball as a counter body under various test temperatures (25 °C, 300 °C, and 600 °C) and loads (10 N and 30 N). The coating is characterized by employing SEM, XRD, micro-hardness tester, particle analyzer, and bond strength tester, and the mechanism of wear reduction was discussed. The post-wear analysis was carried out on the wear track using SEM/EDS and 3D non-contact optical profilometers. The micro-hardness and bond strength of both (17-4PH-30%WC-Co and 17-4PH-30%Cr3C2) coatings are compared. The test results revealed that at all temperatures and loads, 17-4PH-30%WC-Co coating shows better wear resistance and lower friction coefficient than the 17-4PH-30%Cr3C2 coating. The significant influence of the tribo-oxide layer at high temperatures, which contributed to decreasing wear rate and coefficient of friction, was premeditated. © 2023, International Institute of Welding.
Effect of Zinc and Bio-Glass Addition on Mechanical Properties and Corrosion Behavior of Magnesium-Based Composites for Orthopedic Application: A Preliminary Study
(Springer, 2022) Moudgalya, K.V.S.; Sekar, P.; Hebbar, H.S.; Rahman, M.R.
Magnesium is extensively researched as a biodegradable implant material. However, achieving a combination of biomechanical properties viz., controlled degradation, bio-transformability and osteoconductivity is highly challenging. Indeed, bio-composites developed by reinforcing bio-ceramics with metals are gaining research interest. In this current work, the suitability of a bio-composite developed by reinforcing 5, 10 and 15% of bioglass (BG) in Mg and Mg-3 wt.% Zn metal matrix is investigated. The bio-composites containing Mg, Mg-BG and Mg-Zn-BG are processed by vacuum sintering and tested for important mechanical and corrosion properties. Particle size analysis revealed that magnesium exhibited a larger mean particle size while zinc evinced the lowest average particle size. The density-porosity analysis showed that porosity was found to increase linearly with the addition of BG. In contrast, the compressive strength of Mg-BG and Mg-Zn-BG composites increased up to 10 wt.% BG and decreased drastically for 15 wt.% BG reinforcement. The addition of Zn and BG significantly enhanced the Vickers hardness, showing an increasing trend with the increase in BG reinforcement content. Immersion corrosion study in phosphate buffered saline revealed that 10 wt.% BG reinforced composite exhibited the least corrosion rate. Thus, composites developed by reinforcing BG in Mg-3Zn metal matrix showed enhanced mechanical and corrosion properties in the physiological environment. The possible corrosion mechanism of Mg, Mg-Zn and Mg-Zn-BG composites is also proposed and compared. © 2022, ASM International.
Efficiency enhancement in dye-sensitized solar cells through neodymium-doped graphene quantum dot-modified TiO? photoanodes
(Elsevier B.V., 2025) Senadeera, G.K.R.; Weerasekara, W.M.S.K.; Jaseetharan, T.; Sandunika, P.U.; Kumari, J.M.K.W.; Dissanayake, M.A.K.L.; Muhiuddin, M.; Rahman, M.R.; Bhat K, U.; Akhtar, M.W.; Udayakumar, U.; Siddique, A.B.; Ekanayake, P.
This study explored the effects of Neodymium-doped graphene quantum dots (NdGQDs) on improving the performance efficiency of TiO2 based dye-sensitized solar cells (DSSCs). By employing in-situ physical assisted mixing, DSSCs with optimized NdGQDs in TiO2 photoanodes showed a power conversion efficiency of 8.76 %, a significant improvement compared to the 6.01 % efficiency of pristine TiO2-based DSSCs under 100 mW cm?2 illumination (AM 1.5). Notably, the short-circuit current density increased by 74 %. HRTEM analysis revealed that the NdGQDs have a size range of approximately 7–9 nm. UV–visible spectroscopy and Mott-Schottky analysis revealed a positive shift in the Fermi level, promoting better electron transfer and increased photocurrent density at the expenses of the open circuit voltage. Electrochemical impedance spectroscopy characterization of DSSCs incorporating NdGQD-modified photoanodes revealed a reduction in electron transfer resistance at the photoanode|dye|electrolyte interface, accompanied by an increase in recombination resistance within the device suppressing the electron recombination rate. © 2024 Elsevier B.V.
Electronic band structure and photoemission spectra of graphene on silicon substrate
(2014) Javvaji, B.; Ravikumar, A.; Shenoy, B.M.; Roy, Mahapatra, D.; Rahman, M.R.; Hegde, G.M.
Synergizing graphene on silicon based nanostructures is pivotal in advancing nano-electronic device technology. A combination of molecular dynamics and density functional theory has been used to predict the electronic energy band structure and photo-emission spectrum for graphene-Si system with silicon as a substrate for graphene. The equilibrium geometry of the system after energy minimization is obtained from molecular dynamics simulations. For the stable geometry obtained, density functional theory calculations are employed to determine the energy band structure and dielectric constant of the system. Further the work function of the system which is a direct consequence of photoemission spectrum is calculated from the energy band structure using random phase approximations. � 2014 SPIE.
Electronic band structure and photoemission spectra of graphene on silicon substrate
(SPIE spie@spie.org, 2014) Javvaji, B.; Ravikumar, A.; Shenoy, B.M.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.
Synergizing graphene on silicon based nanostructures is pivotal in advancing nano-electronic device technology. A combination of molecular dynamics and density functional theory has been used to predict the electronic energy band structure and photo-emission spectrum for graphene-Si system with silicon as a substrate for graphene. The equilibrium geometry of the system after energy minimization is obtained from molecular dynamics simulations. For the stable geometry obtained, density functional theory calculations are employed to determine the energy band structure and dielectric constant of the system. Further the work function of the system which is a direct consequence of photoemission spectrum is calculated from the energy band structure using random phase approximations. Â© 2014 SPIE.
Elevated temperature wear and friction performance of WC-CoCr/Mo and WC-Co/NiCr/Mo coated Ti-6Al-4V alloy
(Elsevier Inc., 2024) Behera, N.; Ramesh, M.R.; Rahman, M.R.
The effect of adding Mo to WC-based coatings on the microstructure and dry sliding wear performance at elevated temperatures is investigated. The WC-based coatings are deposited using a high-velocity oxy-fuel process on the titanium-31 substrate. The coating was characterized by microstructure, microhardness, porosity, surface roughness, density, and bond strength. The wear and friction behavior of coatings was evaluated using a ball-on disc tribometer at temperatures of 200, 400, 600, and 800 °C and loads of 20 and 30 N. SEM-EDS and an optical profilometer were utilized to evaluate the wear rate and mechanism. The microhardness and bond strength of WC-CoCr/10%Mo coating is more than that of WC-Co/20%NiCr/10%Mo coatings. The WC-CoCr, WC-CoCr/10%Mo, and WC-Co/20%NiCr/10%Mo coatings exhibited decreasing wear rates up to 600 °C, transitioning to an increase at 800 °C. The oxide phases of CoWO4 WO3 MoO3, CoMoO4, and NiMoO4, formed at 600 °C, aid in reducing the rate of wear and friction coefficient. However, the wear rate slightly increased at 800 °C due to vigorous oxidation and softness of coatings. The friction coefficient of WC-CoCr, WC-CoCr/10%Mo, and WC-Co/20%NiCr/10%Mo coating decreases with increasing temperatures due to the lubricating properties of oxide phases on the worn surface. The WC-CoCr/10%Mo coating demonstrates a lower friction and wear rate than the WC-CoCr and WC-Co/20%NiCr/10%Mo coating. At 200 °C, the predominant wear mechanisms were abrasive and fatigue wear, while at 800 °C, oxidative wear, abrasive wear, and adhesive wear were observed. © 2024