Search

The non-degradable metallic implants, such as bone screws, often act as the source of dysfunction and harmful corrosion products in the aqueous environment inside the human body. Many of these implants are fixed either temporarily or permanently into the human body, and therefore, both need to match tight tolerances with a remarkably finished surface to eradicate burrs or striations. In this regard, the new generation of degradable magnesium (Mg) alloy implants with excellent osseointegration and low elasticity (like that of human bone), minimizing stress shielding, have been identified as potential candidates to challenge surgical procedures reintervention. However, the biological response of an implant toward the cells in vivo can be predominantly regulated by modifying the surface chemistry, morphology, and corrosion characteristics. Powder or abrasive-mixed-micro-electric discharge machining (A-M-µ-EDM) is gaining attention for executing precision machining and achieving a simultaneous surface modification on micro-manufactured surfaces, suitable for clinical applications. Therefore, the present research aimed at improving the surface characteristics of Mg AZ31B alloy via an augmented performance of A-M-µ-EDM by adopting copper and brass-micro-electrodes (C-µ-E and B-µ-E) in association with distinct abrasive particle concentrations (APCs: 0, 1.5, 3, 4.5, and 6 g/l) of bioactive zinc abrasives. To enhance the A-M-µ-EDM capabilities, the experiments were designed with a one-variable-at-a-time (OVAT) strategy, and the trial runs were conducted using different combinations of µ-electrodes and APCs. The superior performance of A-M-µ-EDM was noticed with the fusion of C-µ-E and 3 g/l APC in terms of minimum machining time (MT) and dimensional deviation (DD). The additional outcomes of this work reported favorable improvements in surface morphology, chemistry, topography, wettability, microhardness, and corrosion resistance on the A-M-µ-EDMed sample of interest.

The present study aims to understand the influence of surface mechanical attrition treatment (SMAT) on corrosion, wear, and in vitro cell viability of Ti-6Al-4V alloy. XRD analysis quantified the extent of surface nanocrystallization and the induced strain, which increased from 0.096 ± 0.021 to 0.166 ± 0.039, and so did dislocation density (from 1.55 × 1022 to 4.62 × 1022). TEM analysis advocated for grain refinement and also manifested the occurrence of mechanical twins as well as dislocation walls in the SMATed surface. SMAT processing decreased the corrosion rate in simulated body fluid by ~75%, from 0.167 ± 0.097 mpy to 0.040 ± 0.015 mpy. This was attributed to the nanocrystallization that led to the creation of a stable and insoluble TiO2 passive film at the interface of the surface and electrolyte. Grain refinement of the SMATed surface also derived an improvement in the wear resistance and cell adhesion property.

Current study deals with the effect of carbon nanotube (CNTs) and graphene nanoplatelets (GNPs) reinforcement on the mechanical properties and the adhesion strength of plasma sprayed alumina (Al2O3) single splats, using in-situ picoindentation and nanoscratch test, respectively. The hardness of the Al2O3 splat was measured as 18 ± 5.3 GPa which increased to 34.22 ± 8.44 GPa on 1 wt% CNTs addition and to 42.5 ± 9.06 GPa on 0.5 wt% GNPs addition. Hybrid addition of CNTs and GNPs provided the maximum hardness value of 51.25 ± 8.76 GPa to the Al2O3 splat. Similar trend in the elastic modulus has been reported with a minimum value for Al2O3 splat, i.e. 159 ± 35.40 GPa, and maximum for the Al2O3 splat mixed synergistically with CNTs and GNPs (269 ± 43.12 GPa). Adhesion strength of the Al2O3 splat (0.21 ± 0.11 MPa) also showed a nearly 5-fold increase on hybrid addition of CNTs and GNPs with a maximum value of 1.08 ± 0.38 MPa. This improvement in the properties were due to the extremely high mechanical properties of CNTs and GNPs and better melting of the splats, which not only improved the densification but also provided a better interlocking between the splat and the substrate.

The non-degradable metallic implants, such as bone screws, often act as the source of dysfunction and harmful corrosion products in the aqueous environment inside the human body. Many of these implants are fixed either temporarily or permanently into the human body, and therefore, both need to match tight tolerances with a remarkably finished surface to eradicate burrs or striations. In this regard, the new generation of degradable magnesium (Mg) alloy implants with excellent osseointegration and low elasticity (like that of human bone), minimizing stress shielding, have been identified as potential candidates to challenge surgical procedures reintervention. However, the biological response of an implant toward the cells in vivo can be predominantly regulated by modifying the surface chemistry, morphology, and corrosion characteristics. Powder or abrasive-mixed-micro-electric discharge machining (A-M

Various hydroxyapatite (HA) powders synthesized at different temperatures are deposited on titanium alloy by using an atmospheric plasma spray process. These different HA powders were synthesized from Indian clam seashells through the hydrothermal technique at varying temperatures from 700 to 1000 °C for a 2 h time duration in our previous study. The synthesized HA powders are spray-dried to obtain agglomerated powders suitable for spraying during the coating application. Crystallite size, Ca/P ratio, and crystallinity of agglomerated HA powders and their respective coatings are estimated by standard methods. The microstructure and phases of the feedstock and coating materials are investigated by using a field-emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD), respectively. Further, the HA coatings are characterized in terms of surface roughness, microhardness, porosity, adhesion strength, and wear resistance through the stylus profilometer, Vickers micro-hardness tester, image analysis technique, scratch tester, and ball-on-disc tribometer, respectively. The average surface roughness (R

Recently, multifunctional coatings offering simultaneous tribological benefits and protection from adverse environments are gaining widespread attention. While, metallic coatings offer excellent durability, their performance is limited to ambient temperature. In this study, it is shown that plasma sprayed Graphene nanoplatelates (GNPs) reinforced CeO2 (CG) coatings offer excellent tribological properties both at room and high temperature. Interestingly, unlike conventional coatings where wear property degrades at high temperature, the wear properties of CG keeps on improving from RT to 873 K. Maximum reduction in wear rate (260%) and COF (26%) was observed at 873 K. It is believed that this coating could pave the path for designing coatings operating at high temperature.

Boron Nitride Nanotube (BNNT) has emerged as a potential reinforcement for ceramic and metal matrices due to its excellent mechanical, chemical, and thermal properties. We have reinforced 5 vol % BNNT into the alumina (Al2O3) matrix using the atmospheric plasma spraying technique in the present study. BNNTs have been successfully retained after experiencing extreme temperatures of the plasma plume. Reinforcement of BNNTs has improved the relative density of pure Al2O3 coating from 90% to 94%, whereas the hardness, elastic modulus, and fracture toughness enhanced by 117%, 35% and 51%, respectively for the BNNTs reinforced coatings. The critical energy release rate increased from 3.90 ± 1.18 J/m2 to 6.50 ± 1.22 J/m2 with BNNT addition. The property enhancement reasons are attributed to improved densification, uniform distribution of BNNTs into the matrix, and toughening mechanisms, such as BNNT truss, nanotube pull-out, and crack bridging. This BNNT strengthened Al2O3 coating could be a successful candidate for highly durable and strong structural material for automobile and aviation sector, high speed cutting tools and in bioimplant sectors.

As graphene penetrates into industries, it is essential to mass produce high quality graphene sheets. New discoveries face formidable challenges in the marketplace due to the lack of proficient protocols to produce graphene on a commercial scale while maintaining its quality. Here, we present a conspicuous protocol for ultrafast exfoliation of graphite into high quality graphene on the sub-kilogram scale without the use of any intercalants, chemicals, or solvent. We show that graphite can be exfoliated using a plasma spray technique with high single-layer selectivity (∼85%) at a very high production rate (48 g/h). This is possible because of the inherent characteristics of the protocol which provides sudden thermal shock followed by two-stage shear. The exfoliated graphene shows almost no basal defect (Id/Ig: 0) and possesses high quality (C/O ratio: 21.2, sp2 %: ∼95%), an indication of negligible structural deterioration. The results were reproducible indicating the adeptness of the protocol. We provided several proofs-of-concept of plasma spray exfoliated graphene to demonstrate its utility in applications such as mechanical reinforcements; frictionless, transparent conductive coatings; and energy storage devices.

We report fabrication of a novel sticky parahydrophobic cerium oxide (CeO2) coating using a facile and industrially viable plasma spray technique, which has prospective applications in microfluidic chips, no loss microdroplet transportation and chemical microreactors. Our coating displays significantly high water contact angle (∼159.02˚) along with high contact angle hysteresis (CAH≥90˚), very much similar to a ‘Rose petal’. This is further strengthened by the fact that the coating displayed remarkable adhesion even with large inverted water droplets of 70 μL, which is significantly higher than the reported values of 18 μL for polymer and 20 μL for drop casted CeO2 nanotubes. We also present systematic characterization results to clarify the ongoing confusion regarding the hydrophobicity of CeO2 coatings often reported in literature. Meanwhile, our parahydrophobic coating also showed remarkable thermal and mechanical stability even at a significantly high temperature of 200 °C for 14 h and with 50 g abrasive paper.

Splats are the most fundamental and paramount unit of any plasma sprayed coating and splats are having the potential to manipulate the overall property of the same. Current study shows the insulator-conductor transition of alumina (Al2O3) splat by the hybrid addition of carbonaceous nanofillers, namely carbon nanotubes (CNTs) and Graphene nanoplatelets (GNPs) into it. Reinforcement of CNTs and GNPs changed the splat shape from fragmented to nearly disk shaped as well as from porous splat to densified one upon the reinforcement. Further, Current mapping over the splats were carried out using conductive atomic force microscopy (cAFM). Current map for Al2O3 splat showed fully black region, evincing its insulating nature; whereas hybrid addition of CNTs and GNPs into the splat dramatically improved the electrical conductivity of Al2O3 splat, coining its non-conductive map to conductive one. This transition was attributed to electron tunneling mechanism, which is a function of electron hopping distance of these conductive nanofillers. The electron hopping distance of the matrix got minimized when CNTs and GNPs were simultaneously added to Al2O3 splat, due to their higher aspect ratio. This led to the formation of a 3-dimensional conductive channels for the electron transport in the matrix, converting the whole splat as conductive.

Hydroxyapatite (HA) coatings, reinforced with varied concentration (0–2 wt%) of Graphene nanoplatelets (GNPs) have been deposited on titanium alloys (Ti–6Al–4V) substrate using atmospheric plasma spraying. Present work studies the effect of GNP concentration on the electrochemical behaviour of the HA coatings in simulated body fluid (SBF). The HA coating exhibited 15% porosity, whereas reinforcement of 1 wt% GNPs in HA (HA-1G) shows 13% porosity, further addition of 2 wt% GNPs in HA reduced the porosity to 10%. Reduction in porosity was achieved as GNPs easily accessed the inter-lamellae to fill the gaps at inter splat region and minimized the occurrence of post-plasma spray defects such as porosity, voids, microcracks etc. These consequences nextward resulted in the significant enhancement in corrosion resistance of the matrix. HA-1G displayed a significant reduction by 67% in the corrosion rate in SBF solution, while this reduction came to 87% for HA-2G coatings. Randomly oriented wrinkles in the GNPs after corrosion process and their hydrophobic nature effectively hindered the SBF infiltration into the coating and resisted their movement towards the underlying substrate. This in turn improved the overall corrosion resistance of the system.

Hydroxyapatite coating have been deposited on titanium alloys (Ti–6Al–4V) substrate by varying plasma power from 20 to 35 kW using atmospheric plasma spraying. Effect of plasma power variation on the microstructure as well as corrosion behaviour of the coatings has studied exhaustibly in simulated body fluid (SBF). Microstructural analysis revealed that increasing the plasma power from 20 to 35 kW has led to a more densified coating by minimizing the level of porosity and partially melted region as well. This enhanced property is attributed to the higher velocity of the in-flight particles with their shorter residence time at 35 kW. The molten particles strike the substrate without losing much of its energy during its flight, which further boosted the closed packing of the coating layers ensuing a reduced inter-splat region. These improved microstructural properties also escorted to enhancement in corrosion resistance with increase in the plasma power. This enhancement in corrosion behaviour at higher power is attributed to reduction in pores and voids in the coatings which hindered the penetration of SBF solution into the coatings.

In the present study, graphene nanoplatelets (GNPs: 1–2 wt. %) reinforced TiN coating were successfully fabricated over titanium alloy using a reactive shroud plasma spraying technique. All coatings were completely oxide free, while the addition of GNPs suppressed the non-stoichiometric TiN0.3 phase. Improvement of 19%, 18% and 300% in hardness, elastic modulus and fracture toughness was achieved by mere addition of 2 wt. % GNP. The addition of GNP in TiN also reduced the wear volume loss and the wear rate of the coatings for the entire range of temperature (293–873 K). Moreover, GNPs also manifested the coefficient of friction (COF) of the coating. Post wear characterization revealed that the presence of GNP throughout the wear track even at 873 K. The multi-layer structure of GNPs assisted in long term lubricity to the surface and increased the wear resistance of the coating.

In the midst of a huge demand for high-precision miniaturized medical implants made up of potential biomaterials, the biomedical Ti-6Al-4V alloy meets the uncompromising standards for longevity, biocompatibility, and sterilizability required to interact with living cells in medical settings. This research tailored the existing capabilities of a traditional micro-electric discharge machining (µ-EDM) setup by adding 0, 2, 4, 6, 8, and 10 g/l bioactive zinc powder particle concentrations (PPCs) to the dielectric. A copper and brass micro-tool electrode (C-µ-TE and B-µ-TE) was employed in association with each PPC. Experiments were executed using the one-variable-at-a-time (OVAT) approach. Machining time and dimensional deviation were chosen as the response variables of Zn powder mixed-micro-EDM (Zn-PM-µ-EDM). According to the analytical findings, the combination of C-µ-TE and 6 g/l Zn PPC achieved 23.52%, 3.29%, and 17.96% lesser machining time, dimensional deviation, and recast layer thickness, respectively, compared to the B-µ-TE. The detailed study of this surface endorsed a significant modification in terms of improved recast layer thickness (26.44 µm), topography (Ra = 743.65 nm), and wettability (contact angle < 90 deg), suggesting its dental application. In addition, the observation of ZnO and TiO in X-ray diffraction and appealing in vitro cytocompatibility encourage the subsequent biological and therapeutic studies to validate the anticipated antiviral activity of the modified Ti-6Al-4V alloy surface against coronavirus (COVID-19).

In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.

Deposition of graphene as a coating material over large-scale areas is an intense topic of research because of complexities involved in the existing deposition techniques. Higher defects and compromised properties restricted in realizing the full potential of graphene coating. This work aims to deposit graphene coatings by adopting a traditional technique, that is, plasma spraying, which has inherent merits of extremely high cooling rate (∼106 K/s) and low plasma exposure time (∼0.1-10 μs). Graphene nanoplatelets (GNPs) were spray-dried into spherical agglomerates (∼60 μm dia.) and coatings were deposited over a wide range of surfaces. Continuous monitoring of temperature and velocity of in-flight GNPs was done using a diagnostic sensor. Deposition of GNP coatings was the result of striking of quasi-2D melted GNPs with higher velocity (∼197 m/s) toward the substrate. Postcharacterizations confirmed that GNPs did not collapse even after being exposed to harsh environments in plasma. Instead, high temperatures proved to be beneficial in purifying the commercial GNPs. The coatings were transparent even in the short-wavelength infrared region and remained electrically conductive. A proof-of-concept was established by carrying out preliminary corrosion and antifriction tests. Outstanding reduction of ∼3.5 times in corrosion rate and 3 times in coefficient of friction was observed in GNP-deposited coating. It is envisaged that graphene coating by plasma spraying can bring a revolution in commercial sectors.

We report in situ fabrication of oxide-free titanium nitride (TiN) coating by conventional plasma spraying technique. Complete oxide free TiN coating without using low pressure or vacuum environment was achieved by using the N2 shroud with plasma spraying. X-Ray diffraction and Transmission electron microscope confirmed the absence of any traces of oxide in the coating. Coating showed exceptionally higher mechanical properties (H: ∼18 GPa; E: ∼317 GPa). Outstanding reduction of ∼15 times in wear rate and ∼4 times in corrosion rate was observed compared to bare substrate (i.e. Ti-6Al-4V).

Addition of 0.5 wt% of graphene nanoplatelates (GNPs) and 1 wt% carbonnanotube (CNTs) in plasma sprayed Al2O3 coating showed the reduction of 93.25% in wear volume loss and 90.94% in wear rate. This could be attributed to the simultaneous effect of enhanced densification, presence of the transferred layer from the counterpart, strong interface between Al2O3, GNP and CNTs and toughening offered by the GNPs and CNTs. The lowest COF value of 0.27 was recorded on addition of 0.5 wt% of GNP in Al2O3 coating, which could be attributed to the graphitic lubrication on the worn track during the wear.

Lanthanum zirconate (La2Zr2O7), an emerging candidate for TBC system, faces stringent concern owing to poor fracture toughness. We report an exceptionally high fracture toughness (5.3 ± 0.4 MPa m0.5) value for a La2Zr2O7 coating prepared by atmospheric plasma spray technique reinforced by carbon nanotubes (2 wt %); the enhancement in fracture toughness was noted to be more than 300% compared to all previous works. Several factors, viz. increased density, uniform distribution of CNTs in La2Zr2O7 matrix, stabilization of pyrochlore La2Zr2O7 phase and various associated toughening mechanism offered by CNTs (e.g., CNT pull out, CNT bridging and crack arresting etc.) was attributed for this surprising enhancement. In addition, splat sandwiching and nanomechanical interlocking between CNT and La2Zr2O7 was found to be unique toughening mechanism. Apart from it, thermal shock resistance of LZC-SD coating performed at 1300 °C, showed the 145 numbers of cycle before the partial delamination of the coating. While, it was only 87 numbers of cycle for LZ-SD coating. The density, hardness, elastic modulus values also depicted a suitable increase. The introduction of CNTs in the La2Zr2O7 matrix did not alter/affect any of the physical properties (phase purity, compositional integrity etc.) of the pristine La2Zr2O7 system.

We present a simple, direct, one-step, scalable technique for instant tuning of all the different states of wetting characteristics using atmospheric plasma spray (APS) technique. We observed that, just by changing the process parameters in the APS technique, the wetting characteristics of an intrinsically hydrophilic aluminum metallic surface can be tuned to superhydrophilic (contact angle (CA): 0°), hydrophilic (CA: 19.6°), hydrophobic (CA: 97.6°), and superhydrophobic (CA: 156.5°) surfaces. Also, tuned superhydrophobic surface showed an excellent self-cleaning property. Further, we demonstrated that these surfaces retain their superhydrophobic nature even after exposure at elevated temperatures (up to 773 K) and on application of mechanical abrasion. Manipulation in different wetting behavior was possible mainly due to the presence of varying degrees of smooth surface as well as micropillars, which incorporated the multiscale roughness to the surface. "Re-entrant"-like microstructures such as mushroom, cauliflower, and cornet microstructures were observed in the case of tuned superhydrophobic surface, which is well-known for achieving the excellent water repellency over the hydrophilic surface.

Yttria stabilized Zirconia thermal barrier coatings with around 200 μm overlay of Al2O3 and CeO2 were deposited on Inconel substrate using atmospheric plasma spray technique. Hot corrosion tests were carried out on the thermal barrier coating in molten salt mixtures (45 wt% Na2SO4 + 55 wt% V2O5) at 1150 °C for 30 h. Although the YSZ and Al2O3/YSZ coatings were gradually degraded by the infiltration of the molten salt, the CeO2/YSZ coatings remarkably restrained the infiltration of the molten salt into the YSZ coating. For the YSZ coating without any overlay, the YSZ reacted with V2O5 to form YVO4 during exposure to the molten salt, leading to the formation of a large amount of monoclinic phase of ZrO2 due to the leaching of Y2O3 from YSZ. For the Al2O3/YSZ coating, the Al2O3 overlay reduced the rigorous infiltration of the molten salt, which caused in lesser amount of leaching of Y2O3 from YSZ. However, for the CeO2/YSZ coatings, CeO2 not only physically prevented the molten salt infiltration, but also completely reacted with V2O5 to form CeVO4 and completely restrained the infiltration of the molten salt into the YSZ coating. Additionally, the Al2O3/YSZ and CeO2/YSZ showed 17% and 52% increase in thermal shock resistance respectively compared to YSZ coating.

This paper describes about smart racking and retailing using IOT. Hence, it focuses on retailers to understand their challenges and the way IOT can help them overcome these challenges. Nowadays, we find that inventory management has become a very complex problem. Not only the store owner as well as the customer sometimes faces a lot of problems in searching products in store. To solve this problem, we use IOT technology which will resolve both the retailer’s and customer’s problem. With the help of this system, the owner can maintain inventory information smartly. The system will also be helpful for the customers to search products easily in store and may know the details of the product such as product’s availability in store, its price, and similar items. Hence, this will increase more and more customer to the store owner.

The higher grain boundary resistance in the proton-conducting yttrium-doped barium zirconate is one of the major issues to be solved. A new strategy has been experimentally studied on the basis of ...