Nanocomposite Surface Layer Research Articles

Development and sensitivity analysis of MWCNTs coated D-shaped plastic optical fiber sensor for the detection of mercury

Heavy metal pollutants in rivers and water catchments are one of the problems faced by many developing countries as they may result in health issues among their people. A proper sensing mechanism is required to ensure the quality of water. In this research, we propose a simple, low cost, and highly sensitive D-shaped plastic optical fiber (POF) sensor layered with functionalized multi-walled carbon nanotubes (MWCNTs) for the detection of mercury in water. The sensor underwent interrogation across a range of mercury concentrations at room temperature. Numerous methods of characterization have been employed to explore the intricate structural attributes of the sensing layer to verify that the nanocomposite surface layer is functionalized with minimal disruption to the nanotubes. The experimental results revealed that the coated sensor displayed swift response and recovery time of 6.3 s and 13 s respectively when tested with the dynamic mercury concentration range (0 to 5 ppm). Moreover, it exhibited a relative absorbance of 7.33 %/ppm, which is approximately four times higher than the plain sensor and a limit of detection (LOD) of 0.1 ppm. The sensor has the potential to be transformed into an on-site, portable, real-time optical sensor for the detection of mercury ions in drinking water, offering high sensitivity and fast data acquisition.

Dependence of the M choice on the properties of Hf(M)SiCN (M = Nb, Ta, Ti, Zr) ceramic coatings: ab-initio and experimental study

The HfMSiCN coatings (M = Nb, Ta, Ti, Zr) are researched using ab-initio theoretical method and double glow plasma surface alloying. The aim is to enhance the high temperature stability and wear resistance of these coatings, alongside optimizing mechanical and thermodynamic properties. Firstly, the calculated mechanical properties for Hf0.5M0.5CN correlate with those experimental measurement for HfMSiCN. Secondly, the thermodynamic parameters exhibit that the Hf0.5Zr0.5CN has the lowest thermal expansion coefficient and higher bulk modulus at high-temperatures. Moreover, the wear rate of HfZrSiCN at 500 ℃ is less than 60% of its wear rate at 300 ℃. The superior wear resistance of HfZrSiCN coating is attributed to a friction-induced composite layer including a dense amorphous nanocomposite surface layer and a nano-friction glaze layer supported by nanograins.

Superior wear resistance in a TaMoNb compositionally complex alloy film via in-situ formation of the amorphous-crystalline nanocomposite layer and gradient nanostructure

Metallic alloys with exceptional wear resistance have long been an attractive prospect for their enhanced safety, reliability, and service duration. Herein, we propose a strategy to achieve superior wear resistance via the in-situ formation of an amorphous-crystalline nanocomposite layer and gradient nanostructure during wear at elevated temperatures. This strategy was demonstrated in a compositionally complex alloy TaMoNb film with a columnar grain structure upon sliding wear at 300 °C. In contrast to the surface layer formed at room temperature (RT), which consists of irregularly shaped TaMoNb nanograins with non-uniform size and distribution in the amorphous oxide matrix, a dense 300 nm-thick nanocomposite layer comprising equiaxed nanograins of only ∼6 nm embedded in the amorphous oxide matrix is formed during wear at 300 °C, below which is a 600 nm-thick plastic-deformation region that exhibits gradient nanostructure. The microstructure induced by wear at 400 °C shows the presence of a 30 nm-thick amorphous layer below the nanocomposite surface layer but no appreciable plastic deformation in the base film. Consequently, the TaMoNb film exhibits a remarkably low wear rate upon wear at 300 °C that is less than 25% of those at RT and 400 °C. Such superior wear resistance is attributed to the specific wear-induced microstructure generated at 300 °C, which has high strength and large homogeneous deformation. Thus, this work offers a new strategy for designing self-adaptive wear-resistant alloys for application in extreme thermo-mechanical service environments.

Reactive wear protection through strong and deformable oxide nanocomposite surfaces

Wear-related energy and material loss cost over 2500 Billion Euro per year. Traditional wisdom suggests that high-strength materials reveal low wear rates, yet, their plastic deformation mechanisms also influence their wear performance. High strength and homogeneous deformation behavior, which allow accommodating plastic strain without cracking or localized brittle fracture, are crucial for developing wear-resistant metals. Here, we present an approach to achieve superior wear resistance via in-situ formation of a strong and deformable oxide nanocomposite surface during wear, by reaction of the metal surface with its oxidative environment, a principle that we refer to as ‘reactive wear protection’. We design a TiNbZr-Ag alloy that forms an amorphous-crystalline oxidic nanocomposite surface layer upon dry sliding. The strong (2.4 GPa yield strength) and deformable (homogeneous deformation to 20% strain) nanocomposite surface reduces the wear rate of the TiNbZr-Ag alloy by an order of magnitude. The reactive wear protection strategy offers a pathway for designing ultra-wear resistant alloys, where otherwise brittle oxides are turned to be strong and deformable for improving wear resistance.

Comparing the mechanical properties, microstructure, texture and in-vitro degradation behavior of TNTZ/nano-fluorapatite composite and TNTZ bioalloy

The present study deals with (i) the fabrication of the composite surface layer of Ti–29Nb–13Ta-4.6Zr/nano-fluorapatite through friction stir processing, (ii) clarifying the correlation of microstructure and texture with in-vitro degradation behavior and bioactivity of fabricated nano-biocomposite, and (iii) comparing the mechanical and functional properties of nano composite whit those obtained for TNTZ bio-alloy. The results indicated that increasing the number of deformation passes effectively refines the microstructure, leading to the average grain sizes of less than 5 μm. The texture of the material was also evolved in the presence of the nano particles where the grains reorient along <111> direction in contrast to the <101>-oriented grains in the starting microstructure. In-vitro bioactivity of the processed samples was measured after being immersed in simulated body fluid solution for various duration up to 30 days. Enhanced corrosion resistance and bio-mineralization of nanocomposite surface layer was discussed relying on the occurrence of grain refinement, substructure development and evolution of texture components along <101> direction. Assessment of the mechanical properties of the fabricated composites and as-received material also indicated the positive effect of the applied processing route and the presence of nano particles.

Strain gauge properties of Pd+-ion-implanted polymer

Pd+ ions (90 keV) were implanted at normal incidence and at room temperature in different highly insulating (&gt;200 GΩ) thermoplastic polymers (poly(methyl methacrylate), polypropylene, polyethylene terephthalate glycol-modified, and polycarbonate). At high fluence and optimized process parameters, the ion implantation gives rise to the formation of a nanocomposite thin surface layer constituted by Pd nanoclusters and carbonaceous material (nanographite/amorphous carbon). The morphological, microstructural, and microanalytical properties of the nanocomposite layers were investigated by He-ion microscopy, glancing incidence X-ray diffraction, and Raman scattering, respectively. The electrical properties were characterized by resistance, van der Pauw, and Hall measurements. We performed accurate simultaneous deformation/bending experiments and electrical resistance measurements. We show that the electrical resistance varies linearly with the mechanical deformation (beam deflection) applied. The experimental results are interpreted by “hopping conductivity” model considering the nanostructure configuration of the nanocomposite layers. A gauge factor in the range between 4 and 8, depending on the ion-implanted polymer, was obtained for prototype strain gauge devices.

Friction stir vibration processing: a new method to improve the microstructure and mechanical properties of Al5052/SiC surface nanocomposite layer

Friction stir processing (FSP) is a surface processing method to modify the microstructure and enhance the mechanical properties of metal surface. This process is also numerated as a method to incorporate second-phase nanoparticles into microstructure and form surface composites. In the current research, the work specimen is vibrated normal to processing line during FSP. Transverse and rotation movements of shoulder are accompanied with vibration motion of specimen. This new process is entitled FSVP (friction stir vibration processing). The effect of FSP and FSVP processes on microstructure and mechanical properties of Al5052 alloy matrix composite incorporated SiC nanoparticles is analyzed. The results show that the presence of vibration during FSP leads to the grain size decrease in the stir zone and it enhances the homogeneity of particle distribution. The results indicate that strength and ductility of friction stir (FS) processed specimens are lower than those processed by FSVP. These are related to increased deformation and strain of soft material in the stir zone as vibration is applied which promotes the dynamic recovery and recrystallization during FSP. The results also imply that the microstructure is refined more and the strength and the hardness of friction stir vibration (FSV) processed specimens increase as vibration frequency enhances.

TEM characterization on microstructure of Ti–6Al–4V/Ag nanocomposite formed by friction stir processing

Friction stir processing (FSP) was successfully employed to produce gradient multi-phase structured Ti–6Al–4V/Ag nanocomposite surface layer. Microstructural evolution of amorphous/nanocrystalline/nano-twin in the surface layer was characterized by TEM in detail. The formation of amorphous phase in the upper surface of stir zone (SZ) was attributed to mechanically driven amorphization caused by dislocation gliding plastic deformation and elements mixing process. The dislocation activities played a dominant role in causing the distortion of lattices and nanocrystallization. The plastic deformation via FSP was responsible for considerable dislocations pile-up and tangle in the potential deformation bands.

Tribological Properties of Nano TiB2 particle Reinforced 6061-T6 Aluminum Alloy Surface Composites via Friction stir processing

This research work is emphasized on the fabrication of nano Titanium Boride (TiB2) particle reinforced 6061-T6 Aluminum Alloy surface composites via Friction stir processing (FSP). Influence of volume percentage of nano sized TiB2 (average size is 35 nm) reinforcement particles on tribological properties and microstructural characterization of 6061-T6 Aluminum alloy based surface nano composite fabricated via FSP was studied. The fabricated surface composites have been examined by optical microscope (OM) and scanning electron microscope (SEM) for dispersion of reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and wear morphology. The friction stirred zones were characteristically about the size of the rotating pin that is width and depth of 8 mm and 4 mm respectively.The depth of surface nano composite layer is measured as 3683.82 µm along the cross section of stir zone of surface nano composite normal to the FSP direction. Microstructures of all the surface composites are revealed that the distribution of reinforcement particles in the nugget zone (NZ). It is observed that increase in the volume percentage of TiB2 reinforcement particle, the microhardness was increased up to 132 Hv and this value is higher than the as received Aluminum alloy’s microhardness (104 Hv). It is found that high wear resistance exhibited at 4 volume percentage (vol.%) as compared with the 2 and 8 vol.%. The observed tribological properties were correlated with microstructure and wear morphology.

Nickel‐aluminum‐bronze/Al2O3 surface nanocomposite produced by friction‐stir processing: Corrosion properties and microstructure

In this research, friction stir processing (FSP) was applied for fabricating nanosized particles of Al2O3 as a surface composite layer on nickel‐aluminum bronze alloy. In addition, the effect of nanosized Al2O3 on the microstructure, hardness, and corrosion resistance of the alloy surface was investigated. To study the microstructure of the FSP treated surface, optical and scanning electron microscopy were used. Moreover, the static immersion and electrochemically corrosion tests were employed to investigate the corrosion resistance of the FSP‐treated surface. The results indicated that using nanoparticles of Al2O3 to produce the surface nanocomposite layer led to fewer amounts of β transformation products. Furthermore, dynamic re‐crystallized sub‐grains were formed in α grains in the stir zone during severe plastic deformation. In addition, a significant improvement in the corrosion resistance of the alloy surface was observed in the friction stir processed nanocomposite sample in comparison to the one without nanoparticles.

Preparation of nano surface layer composite (TiB2)p on 6061-T6 Aluminum Alloy via Friction Stir Processing

The current research work is focussed to prepare the nano composite surface layer by reinforcing TiB2 particles on 6061-T6 Aluminum Alloy via Friction Stir Processing (FSP). And also study the influence of nano sized reinforcement particles such as TiB2 (average size is 35 nm) on microstructure and mechanical properties of 6061-T6 Aluminum alloy based surface nano composite fabricated via FSP. The fabricated surface composites have been examined by optical microscope (OM) and scanning electron microscope (SEM) for dispersion of reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The friction stirred zones were characteristically about the size of the rotating pin, namely width and depth of 8 mm and 4 mm respectively.The depth of surface nano composite layer is measured as 3683.82 µm along the cross section of stir zone of surface nano composite normal to the FSP direction. Microstructures of all the surface composites are revealed that the distribution of reinforcement particles in the nugget zone (NZ). It is observed that increase in the volume percentage of TiB2 reinforcement particle, the microhardness was increased up to 132 Hv and this value is higher than the as received Aluminum alloy’s microhardness (104 Hv). It is also observed that at 4 volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol.%. The observed mechanical properties were correlated with microstructure and fracture features.

Influence of volume percentage of NanoTiB 2 particles on tribological &amp; mechanical behaviour of 6061-T6 Al alloy nano-surface composite layer prepared via friction stir process

Abstract The aim of present study is to analyze the influence of volume percentage (vol.%) of nano-sized particles (TiB 2 : average size is 35 nm) on microstructure, mechanical and tribological behavior of 6061-T6 Al alloy surface nano composite prepared via Friction stir process (FSP). The microstructure of the fabricated surface nanocomposites is examined using optical microscopy (OM) and scanning electron microscope (SEM) for distribution of TiB 2 nano reinforcement particles, thickness of nano composite layer formed on the Aluminum alloy substrate and fracture features. The depth of surface nano composite layer is measured as 3683.82 μm along the cross section of stir zone of nano composite perpendicular to FSP. It was observed that increase in volume percentage of TiB 2 particles, the microhardness is increased up to 132 Hv and it is greater than as-received Al alloy's microhardness (104 Hv). It is also observed that at 4 volume percentage higher tensile properties exhibited as compared with the 2 and 8 vol. %. It is found that high wear resistance exhibited at 4 volume percentage as-compared with the 2 and 8 vol. %. The observed wear and mechanical properties are interrelated with microstructure, fractography and worn morphology.

Mechanical Properties and Corrosion Behavior of CeO2 and SiC Incorporated Al5083 Alloy Surface Composites

In this investigation, nano-sized cerium oxide (CeO2) and silicon carbide (SiC) particles were stirred and mixed into the surface of an Al5083 alloy rolled plate using friction stir processing (FSP) to form a surface nano-composite layer. For this purpose, various volume ratios of the reinforcements either separately or in the combined form were packed into a pre-machined groove on the surface of the plate. Microstructural features, mechanical properties, and corrosion behavior of the resultant surface composites were determined. Microstructural analysis, optical microscopy and scanning electron microscopy, showed that reinforcement particles were fairly dispersed inside the stir zone and grain refinement was gained. Compared with the base alloy, all of the FSP composites showed higher hardness and tensile strength values with the maximum being obtained for the composite containing 100% SiC particles, i.e., Al5083/SiC. The corrosion behavior of the samples was studied by conducting potentiodynamic polarization tests and assessed in terms of corrosion potential, pitting potential, and passivation range. The result shows a significant increase in corrosion resistance of the base alloy; i.e., the longest passivation range when CeO2 alone was incorporated into the surface by acting as cathodic inhibitors. Composites reinforced with SiC particles exhibited lower pitting resistance due to the formation of microgalvanic couples between cathodic SiC particles and anodic aluminum matrix. The study was aimed to fabricate metal matrix surface composites with improved hardness, tensile strength, and corrosion resistance by the incorporation of CeO2 and SiC reinforcement particles into the surface of Al5083 base alloy. Optimum mechanical properties and corrosion resistance were obtained for the FSP composite Al5083/(75%CeO2 + 25%SiC). In this particular FSP composite, hardness and tensile strength were increased by 30, and 14%, respectively, and passivation range was increased to 0.19 V/SCE compared to the base alloy with no passivation range.

Wear characteristics of Al–Cr–O surface nano-composite layer fabricated on Al6061 plate by friction stir processing

Al–Cr–O hybrid nano-composites have been fabricated in-situ on the surface of Al6061 plate by friction stir processing (FSP) and their wear resistance has been investigated and compared with Al6061-T6 and friction stir processed (FSPed) Al6061-T6. A new procedure was introduced for applying the reinforcement particles, in which Cr2O3 powder was applied on Al6061 plate by atmosphere plasma spray and then the FSP was performed on the plate. During FSP due to thermomechanical condition, Cr2O3 was reduced with aluminum so pure Cr and Al2O3 were produced and as a result of reaction between Al and Cr, intermetallic compounds including Al13Cr2 and Al11Cr2 appeared. Dry sliding wear tests were applied using a reciprocating wear test. Results showed improved wear resistance in nano-composite samples. Al6061-T6 plate after FSP showed lower wear resistance than Al6061-T6 and nano-composites. This is due to the loss of hardening precipitates as a result of FSP.

Synthesis and Properties of Magnetically Operated Nanocomposites Based on Transition Metals Oxides

Technique for synthesis magnetically operated nanocomposites based on transition metals oxides (MeFe2O4, Me = Fe2+, Ni2+, Co2+) with biologically compatible coating (SiO2)x were developed and optimized. Tetraethoxysilane (TEOS) and sodium silicate were used as precursors for formation of SiO2 onto surface of magnetic component. Content of SiO2 in nanocomposite surface layer were adjusted from 0.1 g to 1.0 g for 1.0 g of magnetic component. Structure of the obtained nanocomposites was studied using XRD method, electron microscopy and IR-Fourier spectroscopy. Influence of adsorbents composition on their magnetic properties was studied using vibration magnetometer. It was shown that values of specific magnetization at saturation for nanocomposites containing 0.2 g of non-magnetic component per 1 g of magnetic component corresponds to the typical values of pure magnetic phase. With increasing of content of non-magnetic components a decrease of specific magnetization at saturation was revealed.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3818

Tribological and corrosion behavior of friction stir processed Ti-CaP nanocomposites in simulated body fluid solution

In the present study, friction stir processing was utilized to incorporate nano-hydroxyapatite particles into Ti–6Al–4V substrates to fabricate Ti-CaP nanocomposite surface layer. Microstructures of the stir zone and the fabricated Ti-CaP nanocomposite layer were analyzed using optical and scanning electron microscopy, respectively. Microhardness profile and AFM analysis of substrates were then studied. The microhardness of Ti-CaP nanocomposite layer was reached about 386 HV due to the grain refinement and the distribution of nano-hydroxyapatite particles. Potentiodynamic polarization studies showed that the Ti-CaP nanocomposite layer protected effectively the Ti–6Al–4V substrates from corroding in simulated body fluid solution. The tribological properties of the samples were studied in both dry and simulated biological conditions. The wear rate and friction coefficient decreased by friction stir processing on Ti–6Al–4V substrates. From the analysis of plotted graphs of weight loss versus sliding distance, a correlation between wear coefficient and microhardness through thickness was established. The wear mechanisms were also investigated through scanning electron microscopy. It was shown that the major mechanism was abrasive wear.

Effects of thermal conditions on microstructure in nanocomposite of Al/Si3N4 produced by friction stir processing

A novel surface modifying technique has been used for fabrication of surface nanocomposite layer of Al5754/Si3N4. The effect of traverse and rotational speed on peak temperature was investigated. With the decrease of traverse speed the peak temperature was increased. Furthermore with increase of rotational speed the peak temperature was increased but in high rotational speed the variation of peak temperature was slight. Also the effect of traverse and rotational speed on stirred zone area was surveyed. The results showed that rotational speed is more effective on stirred zone area than traverse speed. The effect of rotational and traverse speed on grain size was also investigated. It was observed that with increasing the traverse speed to rotational speed ratio the grain size was increased with the exception of some rotational speed such as 1800rpm. The Si3N4 particles were uniformly distributed in the aluminum matrix. Also the effect of shoulder penetration on fabrication of surface nanocomposite layer was examined. It was observed that under special penetration shoulder, surface nanocomposite layer can be produced. The microhardness of surface nanocomposites produced under different rotational and traverse speed was also evaluated.

Microstructure and mechanical properties of steel/TiC nano-composite surface layer produced by friction stir processing

A steel/TiC nano-composite surface layer with ultra fine grains of less than 600nm was fabricated on mild steel substrate by introduction of nano-sized TiC powder into the stir zone employing four passes of friction stir processing. TiC clusters were formed after the first pass. Sequential break-up of clusters and refinement of matrix grains were caused by subsequent FSP passes. A near uniform dispersion of nano-sized TiC particles was achieved after the fourth pass. The fabricated nano-composite layer exhibited a maximum micro hardness value of ~450HV; this is much greater than 185 and 130HV of the friction stir processed layer without introduction of TiC powder and as-received substrates, respectively. Moreover, a significant improvement in wear resistance of the nano-composite layer was observed as compared with that of the as-received substrate. The enhanced properties are attributed to the uniform dispersion of hard nano-sized TiC reinforcements in a matrix of ultra fine dynamically recrystallized grains.

An innovative fabrication of nano-HA coatings on Ti-CaP nanocomposite layer using a combination of friction stir processing and electrophoretic deposition

In the present study, a combination of friction stir processing and electrophoretic deposition was used to fabricate nano-hydroxyapatite coatings on the Ti-CaP nanocomposite surface layer. A constant tool rotation rate of 250rpm, travel speed of 16mm/min and plunge depth of 1.2mm with a tool tilt angle of 3° were used to incorporate nano-hydroxyapatite particles into Ti–6Al–4V substrates. Microstructure of the stir zone was analyzed using optical and scanning electron microscopy. Microhardness profile and AFM analysis of substrates were then studied. The electrophoretic deposition of nano-HA particles was carried out at constant voltage of 30V after 60s. The as-deposited nano-HA coating was characterized employing scanning electron microscope and X-ray diffraction. The results of adhesion test and potentiodynamic polarization measurements showed that Ti-CaP nanocomposite layer could effectively increase the bonding strength between coating and substrate as well as corrosion resistance.

Predicting the grain size and hardness of AZ91/SiC nanocomposite by artificial neural networks

In the present study, SiC nanoparticles were added to as-cast AZ91 magnesium alloy through friction stir processing (FSP) and an AZ91/SiC surface nanocomposite layer was produced. A relation between the FSP parameters and grain size and hardness of nanocomposite using artificial neural network (ANN) was established. Experimental results showed that distribution of nanoparticles in the stirred zone (SZ) was not uniform and SZ was divided into two regions. In the ANN modeling, the inputs included traverse speed, rotational speed, and region types. Outputs were hardness and grain size. The model can be used to predict hardness and grain size as functions of rotational and traverse speeds and region types. To check the adequacy of the ANN model, the linear regression analyses were carried out to compute the correlation coefficients. The calculated results were in good agreement with experimental data. Additionally, a sensitivity analysis was conducted to determine the parametric impact on the model outputs.