Silicon Nitride Nanoparticles Research Articles

In-Situ Convertible Amorphous Silicon Nitride (SiNx) Anode: Resolving the Long-Term Cyclic Instability of Silicon

Silicon (Si) has shown its promises as anode material for next-generation high-energy lithium-ion batteries (LIBs) due to its high theoretical capacity1. However, its practical application has been impeded by the severe cyclic instability caused by a large volume change during (de) lithiation. Recently, a new family of silicon-based anode materials called “in-situ convertible-type anode materials” has emerged to resolve the cyclic instability of silicon.2,3 This family includes sub-stoichiometric oxides, nitrides, and carbides of silicon (SiAx, where A = N, C, O). The working principle of these materials follow two mechanisms: (1) irreversible conversion and (2) reversible alloying/dealloying. During initial lithiation, the conversion reaction occurs, forming Si-Li nanodomains inside a stable Li-conductive matrix denoted as LiySixA (A=N, C, O). In the subsequent cycles, the Si-Li nanodomains reversibly alloying/dealloying with Li, while the Li-conductive matrix ensures stable cycling and good rate capability. Such composition mitigates the challenges associated with Si’s large volume change ensuring long-term cyclic stability.In this study, we demonstrate our approach on the development of silicon-rich, sub-stochiometric, amorphous silicon nitride (SiNx) nanoparticles, as an in-situ convertible-type anode material and its long-term cyclic performance for LIBs. In this approach, the SiNx nanoparticles are produced via the decomposition of silane gas in the presence of ammonia using an industrially scalable, free space reactor (FSR), which is developed and customized in our research institute (IFE) (Fig. 1a). Proper proportions of silane and ammonia gases are introduced into the reactor, leading to the nucleation and growth of SiNx nanoparticles. The synthesized SiNx nanoparticles exhibited Si-rich domain and amorphous structure with particle size between 100 nm - 200 nm (Fig. 1b), as confirmed by SEM, TEM and XRD characterizations. The presence of nitrogen in silicon dominated composition is revealed by energy dispersive electron spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). The scalability and reproducibility of the FSR synthesis method makes it a promising approach for the industrial production of SiNx for advance anode materials for LIBs.The electrochemical performance of the synthesized SiNx anode is evaluated by galvanostatic cycling and electrochemical impedance spectroscopy. The electrochemical performance of the SiNx performed on the electrodes with the active mass loading of 0.987 mg/cm2 and cycled at C/5 rate has preserved its capacity about 852 mAh/g after around 600 cycles. As seen from Fig. 1c, the improved cyclic stability of the SiNx compared with pure silicon indicates that the Li-conductive matrix plays crucial role in stabilizing the anode. The authors emphasize the need for further investigation and collaboration, particularly in advance characterization, to better understand the composition and mechanisms of the Li-conductive matrix in the SiNx anode. Such detailed understanding can significantly benefit the conversion-type anode materials for their widespread use in future LIB technologies.References Zuo, X., Zhu, J., Müller-Buschbaum, P. & Cheng, Y.-J. Silicon based lithium-ion battery anodes: A chronicle perspective review. Nano Energy 31, 113–143 (2017).Ulvestad, A. et al. Stoichiometry-Controlled Reversible Lithiation Capacity in Nanostructured Silicon Nitrides Enabled by in Situ Conversion Reaction. ACS Nano 15, 16777–16787 (2021).Kilian, S. O. et al. Active Buffer Matrix in Nanoparticle-Based Silicon-Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium-Ion Batteries. Advanced Materials Interfaces 9, 2201389 (2022). Figure 1

Comparative Study of Photothermal Conversion Efficiency in Aqueous Suspensions of Silicon and Titanium Nitride Nanoparticles for Biomedical Applications

Comparative Study of Photothermal Conversion Efficiency in Aqueous Suspensions of Silicon and Titanium Nitride Nanoparticles for Biomedical Applications

Effect of silicon nitride nanoparticles on the microstructure, phase, hardness and wear properties of NiCrAlY-based nanocomposite

ABSTRACT Despite the significant oxidation resistance of NiCrAlY alloy, one of the disadvantages of this alloy is its softness and poor mechanical properties, and low wear resistance. Therefore, in this study, silicon nitride nanoparticles have been used to improve the hardness and wear resistance of the NiCrAlY alloy. The present research has examined the effect of different amounts of Si3N4 nanoparticles (1, 3, and 5 wt.%) on the structure and mechanical properties of NiCrAlY alloy. The samples were characterised by scanning electron microscopy, X-ray diffraction, and Vickers microhardness device. Initially, Si3N4 powders with 1, 3, and 5 wt% were mixed with NiCrAlY powder in a mechanical mill. Next, the powdered mixtures underwent spark plasma sintering (SPS) operations at 1100 °C for 6 min. The results of microhardness measurements showed that adding 1% Si3N4 to NiCrAlY caused the elevation of the hardness from 418 to 614 HV. Further, the sample indicated a wear rate of 1.42 × 10−5 (m3/N.m) at room temperature, under a loading force of 9.8 N, and a sliding length of 500 m. However, with an increase in the weight percentage of Si3N4 in the sample from 1 to 5 wt%, the hardness diminished from 614 to 543 HV.

Influence of Dispersed Phase Content on the Mechanical Properties of Electroless Nanocomposite Ni-P/Si3N4 and Hybrid Ni-P/Si3N4/Graphite Layers Deposited on the AW-7075 Alloy.

The article presents the results of mechanical testing of Ni-P/Si3N4 nanocomposite and hybrid Ni-P/Si3N4/graphite coatings deposited on AW-7075 aluminum alloy using the chemical reduction method. In terms of mechanical testing, microhardness was measured, and surface roughness and adhesion of the coatings to the aluminum substrate were determined using the "scratch test" method. The surface morphology of the deposited layers was also analyzed using light microscopy and scanning electron microscopy. Samples made of AW-7075 aluminum alloy with electroless deposited Ni-P/Si3N4 nanocomposite, Ni-P/graphite composite and hybrid Ni-P/Si3N4/graphite coatings with different content of dispersed phases were tested, and also, for comparison purposes, the Ni-P layer that constituted the matrix of the tested materials. Reinforcing phases in the form of silicon nitride nanoparticles and graphite particles were used in the layers. The purpose of the research was a thorough characterization of the coating materials used on aluminum alloys in terms of mechanical properties. Graphite is considered in this paper as it enables the reduction of the coefficient of friction through its lubricating properties. Unfortunately, graphite is difficult to use in selected layers as the only dispersion phase, because it has much lower hardness than the Ni-P coating. For this reason, a layer with a single dispersion phase in the form of graphite will be characterized by worse mechanical properties. It is necessary to add particles or nanoparticles with hardness higher than the base Ni-P coating, e.g., Si3N4, which improve the mechanical properties of the coating. The presented analyses of the results of the conducted research complement the previous studies on selected properties of nanocomposite layers with an amorphous structure and supplement the knowledge regarding their suitability for application to aluminum machine parts.

Silicon nitride nanoparticles-based radiative charge recombination chemiluminescence for the highly selective and sensitive detection of diquat

Diquat (DQ) is widely applied in the agriculture industry to ensure crop yield and quality, but this compound poses a serious hazard to human beings. The design of an efficient sensing platform for DQ is essential for food safety and environmental protection. Here, we developed a radiative charge recombination chemiluminescence (CL) using silicon nitride nanoparticles (Si3N4 NPs) as luminophore via hypochlorite (NaClO) activation for DQ quantification. With more active sites (N-Cl) on the surface of Si3N4 NPs, Si3N4 NPs displayed specific CL performance toward DQ. Accordingly, a new CL system for DQ detection was fabricated with satisfactory linearity (10–200 μg/L) and detection limit (6.1 μg/L), relative standard deviation (RSD) was lower than 1%. This new CL assay does not respond to other pesticides, and no interferences from metal ions that have been reported before in the DQ CL sensors. The CL mechanism was proposed that Si3N4 NPs act as the catalyst to accelerate the generation of superoxide radical (O2·−) from DQ, and then the radiative charge recombination of Si3N4 NPs occurs between the O2·− and exogenous holes for extraordinary CL emission. This work provides a general route for the construction of nanoparticle CL probe, which will aid in the monitoring of pollutants.

Bridging a Gap in Thermal Conductivity and Heat Transfer in Hybrid Fibers and Yarns via Polyimide and Silicon Nitride Composites.

The pressing issues of the energy crisis and rapid electronics development have sparked a growing interest in the production of highly thermally conductive polymer composites. Due to the challenges related to the poor processability of hybrid materials and filler distribution to achieve high thermal conductivity, electrospinning is employed to create composite nanofibers and yarns using polyimide (PI) and thermally conductive silicon nitride (SiN) nanoparticles. The thermal performance of the individual nanofibers is evaluated using scanning thermal microscopy (SThM), providing significant insights into their heat transfer performance. Next, the nanofibers are applied as coatings on resistance wires to assess the thermal conductivity and insulation properties. Notably, the samples containing 35 wt.% of SiN exhibit a 25% increase in surface temperature. These innovative materials hold great promise as exceptional candidates for smart textiles and thermal management applications, addressing the growing demand for effective heat dissipation and regulation.

Bacterial Cellulose‐Based Janus Films with Radiative Cooling and Solar Heating Properties for All‐Season Thermal Management†

Comprehensive SummaryAdvanced radiative cooling materials with both heating and cooling mode is of pivotal importance for all‐season energy‐saving in buildings. In this work, we report the design and fabrication of bacterial cellulose‐based Janus films (J‐BC) with radiative cooling and solar heating properties, which were developed by two‐step vacuum‐assisted filtration of modified MXene‐doped bacterial cellulose and modified silicon nitride (Si3N4)‐doped bacterial cellulose, followed by hot‐pressing and drying treatments. The as‐prepared J‐BC films show a unique Janus structure where modified MXene nanosheets and cellulose nanofibers are on the bottom surface, and modified silicon nitride (Si3N4) nanoparticles and cellulose nanofibers are on the top surface. The radiative cooling effect of J‐BC films is enabled by the Si3N4‐doped bacterial cellulose due to the high mid‐infrared emissivity of Si3N4 nanoparticles, which shows a high solar reflection of ~98.1% and high emissivity of ~93.6% in the atmospheric transparency window (8—13 μm). Thanks to the enhanced photothermal conversion of the modified MXene nanosheets, a reduced solar reflection (6.6%) and relatively low thermal emissivity in the atmospheric window (71.4%) are achieved, making sure the solar heating effect of J‐BC films. In the outdoor tests, J‐BC films achieve a sub‐ambient temperature drop of ~3.8 °C and an above‐ambient temperature rise of ~14.2 °C. Numerical prediction demonstrated that the J‐BC films with dual modes have great potential of all‐season energy saving for buildings and a corresponding energy‐saving map in China is also created. The work disclosed herein can provide an avenue for the shaping of advanced radiative cooling materials for emerging applications of personal thermal management, sustainable energy‐efficient buildings, and beyond.

Optimizing the Rheological and Thermomechanical Response of Acrylonitrile Butadiene Styrene/Silicon Nitride Nanocomposites in Material Extrusion Additive Manufacturing.

The current research aimed to examine the thermomechanical properties of new nanocomposites in additive manufacturing (AM). Material extrusion (MEX) 3D printing was utilized to evolve acrylonitrile butadiene styrene (ABS) nanocomposites with silicon nitride nano-inclusions. Regarding the mechanical and thermal response, the fabricated 3D-printed samples were subjected to a course of standard tests, in view to evaluate the influence of the Si3N4 nanofiller content in the polymer matrix. The morphology and fractography of the fabricated filaments and samples were examined using scanning electron microscopy and atomic force microscopy. Moreover, Raman and energy dispersive spectroscopy tests were accomplished to evaluate the composition of the matrix polymer and nanomaterials. Silicon nitride nanoparticles were proved to induce a significant mechanical reinforcement in comparison with the polymer matrix without any additives or fillers. The optimal mechanical response was depicted to the grade ABS/Si3N4 4 wt. %. An impressive increase in flexural strength (30.3%) and flexural toughness (47.2%) was found. The results validate that these novel ABS nanocomposites with improved mechanical properties can be promising materials.

Thermophysical study of neutron irradiated silicon nitride nanoparticles

Silicon nitride (Si3N[Formula: see text] nanoparticles were irradiated with neutrons at different energy fluxes. Differential thermal analysis of non-irradiated and neutron irradiated samples was performed in the temperature range of 300–1400 K. Based on the obtained experimental results, relevant thermophysical parameters were calculated and discussed in detail. All analyses were comparatively discussed for non-irradiated and neutron irradiated nano-Si3N4 particles. On the basis of endotherms observed in DTA spectra, entropy and enthalpy in Si3N4 are interpreted in detail. Compared with the non-irradiated sample, slightly negative values of enthalpy indicate the formed [Formula: see text]P isotope due to neutron irradiation. In the mentioned temperature range, the values of the free Gibbs energy were calculated for all samples, and it was determined that it is varied around zero up to 600 K. Moreover, the effect of neutron transmutations on heat transfer in Si3N4 nanoparticles has been studied.

Synergistic behavior of dual filler system (n‐Si3N4/COOH‐MWCNT) on the mechanical, tribological, curing, and corrosion characteristics of epoxy hybrid nanocomposites

AbstractEpoxy hybrid nanocomposites reinforced with silicon nitride nanoparticles (SiN) and carboxylic acid‐modified multiwalled carbon nanotubes (COOH‐MWCNT) were prepared by hand layup. These hybrid nanocomposites have not undergone thorough investigation in the fields of mechanical, tribological, and corrosion‐resistant characteristics. The 0.25/0.5 SiN/MWCNT hybrid nanocomposite displayed improvement in elongation by 190% and fracture toughness by 360%. The effect of dual filler system on the wear and friction properties of the composite was investigated. The influence of silicon nitride and hybrid fillers the curing characteristics of epoxy was examined using Fourier transform infrared spectroscopy (FTIR). From differential scanning calorimetry (DSC), it was found that the use of dual fillers in the epoxy system reduced the residual heat of reaction and curing time by 15%. In a highly corrosive environment (3.5% NaCl), TAFEL polarization showed that 0.5/0.5 SiN/MWCNT epoxy hybrid coating on mild steel (MS) increased protection against corrosion by 30%. The dispersion of nanofillers and their interactions were verified using high‐resolution transmission electron microscopy (HR‐TEM). The morphology of the fracture, wear, and corroded surfaces were examined by field emission scanning electron microscopy (FE‐SEM). SiN manifested a synergistic effect with MWCNTs making it a superior reinforcement at very low content.

Influence of content of silicon nitride nanoparticles into micro-arc oxidation coating of titanium on bactericidal capability and osteoblastic differentiation

Bone implants with osteogenic and bactericidal capability are particularly promising for orthopedic applications. Herein, micro-arc oxidation (MAO) coatings containing silicon nitride (Si3N4) on titanium (Ti) surface (MSN) were fabricated by dispersing different content of Si3N4 nanoparticles in the electrolyte. Compared with pure Ti and MAO coating, incorporation of Si3N4 nanoparticles into the MAO coating caused significant change in surface characters (e.g., nano-topography, hydrophilicity and surface energy) of MSN, and the change depended on the content of Si3N4 nanoparticles. MSN with the changed surface characters exhibited remarkable improvement of cell response (e.g., multiplication and osteoblastic differentiation), which significantly enhanced with the increase of Si3N4 content. Furthermore, MSN displayed excellent bactericidal ability, which improved with the increase of Si3N4 content. As a result, the enhancements of cellular response and bactericidal capability were ascribed to the increase of Si3N4 content in the coating, and MSN with high content of Si3N4 possessed outstanding osteogenic and anti-bacterial effects. The study demonstrated that incorporation of Si3N4 nanoparticles into the MAO coating led to novel implantable materials of MSN, which exhibited excellent cytocompatibility, osteogenic bioactivity, bactericidal ability, suggesting that MSN possessed a promising potential for applications in orthopedics.

Inorganic Adsorption on Thermal Response and Wear Properties of Nanosilicon Nitride-Developed AA6061 Alloy Nanocomposite

Inorganic-based ceramic reinforcements are promising superior thermal behaviour and are lightweight and developed with aluminium alloy matrix for automobile applications. The AA6061 alloy nanocomposite containing 0 wt%, 4 wt%, 8 wt%, and 12 wt% of silicon nitride nanoparticles(50 nm) was synthesized by stir cast. The influences of thermal adsorption on silicon nitride (nano) additions, density, thermal response, hardness, and wear characteristics of AA6061 matrix nanocomposites are studied. Based on the rule of mixture, the density of nanocomposites is evaluated. The differential thermal and thermogravimetric analysis techniques are used to find the thermal response nanocomposite. The differential scanning calorimeter is used to find the heat flow between 400°C and 700°C. The micro Vickers hardness and wear characteristics of AA6061 nanocomposite were experimentally investigated by ASTM E384 and ASTM G99-05 standards. The adsorption of inorganic nanosilicon nitride particles (12 wt%) in AA6061 alloy showed a decreased mass loss with increased temperatures 0° to 700°C. The differential thermal analysis of nanocomposite reveals the transformation of solid-to-liquid phase under high temperature (528°C).

Synthesis of Silicon Nitride Nanoparticles by Upcycling Silicon Wafer Waste Using Thermal Plasma Jets.

Silicon (Si) waste generation is a critical issue in the development of semiconductor industries, and significant amounts of Si waste are disposed via landfilling. Herein, we propose an effective and high value-added recycling method for generating nitride nanoparticles from Si waste, such as poor-grade Si wafers, broken wafers, and Si scrap with impurities. Si waste was crushed and used as precursors, and an Ar-N2 thermal plasma jet was applied at 13 kW (300 A) under atmospheric pressure conditions. A cone-type reactor was employed to optimize heat transfer, and Si waste was injected into the high-temperature region between the cathode and anode to react with free/split nitrogen species. Spherical Si3N4 nanoparticles were successfully synthesized using isolated nitrogen plasma in the absence of ammonia gas. The crystalline structure comprised mixed α- and β-Si3N4 phases with the particle size <30 nm. Furthermore, the influence of ammonia gas on nitridation was investigated. Our findings indicated that Si3N4 nanoparticles were successfully synthesized in the absence of ammonia gas, and their crystallinity could be altered based on the reactor geometry. Therefore, the as-proposed thermal plasma technique can be used to successfully synthesize high value-added nanopowder from industrial waste.

Sliding wear characteristics of Mg/Si3N4 nanocomposites at room and elevated temperatures

• Mg/Si 3 N 4 nanocomposites were prepared through ultrasonic-assisted stir casting. • A uniform dispersion of Si 3 N 4 nanoparticles was achieved for the composites. • Si 3 N 4 nanoparticles increased the microhardness at room and elevated temperatures. • The wear rate of the Mg/Si 3 N 4 nanocomposites was almost constant up to 200 °C. Magnesium's future use in automobile powertrain applications will necessitate superior wear resistance at elevated temperatures. To address this problem, the current work utilized Silicon Nitride (Si 3 N 4 ) nanoparticles to increase the wear resistance of magnesium at room and elevated temperatures (100 °C, 150 °C, and 200 °C). Using the ultrasonic-assisted stir casting process, 1.5 vol% of Si 3 N 4 nanoparticles were homogeneously reinforced in the pure magnesium matrix. Notably, the hardness of the nanocomposites increased at both room and higher temperatures. Furthermore, the inclusion of Si 3 N 4 nanoparticles resulted in a nearly constant wear rate up to 200 °C, indicating enhanced wear resistance of nanocomposites at high temperatures. The worn pin surfaces of pure magnesium revealed abrasion, severe adhesion, and delamination wear as the dominant mechanisms, whereas oxidation was prevalent in nanocomposites.

Lithium-Ion Battery Anodes Based on Silicon Nitride Nanoparticles as Active Material and Vertically Aligned Carbon Nanotubes as Electrically Conductive Scaffolding

As part of lithium-ion battery research, especially in the field of electromobility, the improvement in battery capacity and rate capability is increasingly important to, e.g., be able to travel further and charge faster. Silicon in the form of nanoparticles as anode active material is therefore heavily investigated due to its high gravimetric capacity and tolerance against pulverization. However, the low electrical conductivity of silicon nanoparticle-coated layers, as a consequence of numerous point contacts between particles with and without a native oxide shell, has a negative impact on the silicon anode’s rate capability. To achieve silicon anodes with a high rate performance, vertically aligned carbon nanotubes with their intrinsically beneficial electrical properties, grown via chemical vapor deposition on copper foil and structured by solvent spray treatment, are used as an electrically conductive scaffolding in conjunction with silicon nanoparticles. The aim of this approach is to expand the two-dimensional surface of copper current collectors. Compared to conventional anodes, the carbon nanotube concept offers a higher proportion of active material in good electrical contact with the current collector and hence superior performance at higher C-rates. In our case, instead of using pure silicon nanoparticles, silicon-rich silicon nitride nanoparticles are integrated into this carbon nanotube structure by ultrasonic spray coating due to their superior cycling stability. As proof of principle, the first cycling results of half-cells with the silicon nitride/carbon nanotube composite anode structure are discussed, which show a capacity retention of 52% at a current of 10C. This corresponds to an improvement of 20% over a copper/silicon nanoparticle reference anode without vertically aligned carbon nanotubes.

Study of the mechanical, wear and corrosion behaviour of silicon nitride nanoparticles reinforced copper surface composite through friction stir processing

The present work is focused on synthesizing Copper/Silicon Nitride (Si3N4) Nano Surface Composite (NSC) by friction stir processing. All the four copper plates had a groove width of 0.6, 0.9, and 1.2 respectively. A dual-pass FSP was carried out, the rotational speed of the tool is 1400 rpm, an axial force of 10 k N, and a traverse speed of 15 mm min−1. The microstructure and the distribution of silicon nitride nanoparticles were studied using a field emission scanning electron microscope (FESEM). The results indicate that the tensile strength of Cu/Si3N4 NSC increased and they exhibit superior micro hardness, corrosion resistance, and wear resistance compared to pure copper.

Assessing Mg/Si3N4 biodegradable nanocomposites for osteosynthesis implants with a focus on microstructural, mechanical, in vitro corrosion and bioactivity aspects

Magnesium-based biodegradable implant materials for the osteosynthesis process (fixation or stabilizing of a fractured bone) are on the verge of being used clinically. However, the rapid degradation of magnesium-based materials in the physiological environment results in a loss of mechanical integrity before the complete healing of the fracture site. To address this issue, the present study used Silicon Nitride (Si3N4) nanoparticles to improve the in-vitro degradation resistance along with the mechanical strength and ductility of Magnesium. The Si3N4 nanoparticles were homogeneously reinforced in the pure Magnesium matrix through the ultrasonic-assisted stir casting method. Moreover, the effect of Si3N4 nanoparticles on microstructure, mechanical, in-vitro corrosion and bioactivity response of Mg/Si3N4 nanocomposites was studied. Notably, the inclusion of 1.0 vol% Si3N4 nanoparticles increased tensile strength by 1.4 times and ductility by two times. In addition, the elastic modulus of Mg/Si3N4 nanocomposites is within the range of local cortical bone elastic modulus. In-vitro immersion experiments in simulated physiological fluids revealed a 2.2-fold reduction in degradation rate compared to pure Magnesium. Moreover, the addition of Si3N4 nanoparticles enhanced the in-vitro bioactivity, as the surface of the nanocomposites showed a high needle-like Ca–P apatite layer with a 1.41 Ca/P ratio of the deposited layer close to hydroxyapatite's Ca/P ratio (1.64). Overall, this study provides the basis for the fabrication of stable yet completely biodegradable Mg/Si3N4 nanocomposite bone implants for the osteosynthesis process.

Silicon nitride nanoparticles reinforced the corrosion resistance of Ni-Cu composite coating in simulated seawater solution

A new type of Ni-Cu/Si3N4 nanocomposites was prepared by pulse electrodeposition technology, which can be used for corrosion protection in seawater environment. XRD, SEM, AFM, EDS and XPS were used to study the structure, morphology, and surface composition of the deposited layers. The hardness and anti-corrosion performance of the deposits were evaluated using a microhardness tester and an electrochemical workstation. Meanwhile, the samples were characterized by EIS, SEM, EDS and XPS after immersion in simulated seawater for 7 days, 14 days, and 28 days. The results show that the average crystallite size of the nanocomposite with face-centered cubic structure is 13.2 nm, and has a dense granular nodular structure without obvious defects. EDS and XPS demonstrated the successful embedding of Si3N4 nanoparticles with uniform distribution in the coating. Besides, it was found that embedding Si3N4 particles in Ni-Cu alloy coatings can significantly strengthen the microhardness and anti-corrosion performance of the material. Furthermore, the Ni-Cu-Si3N4 (0.7 g·L−1) nanocomposite exhibited excellent corrosion resistance even after immersion in simulated seawater medium for 28 days.

Effects of newly synthesized nanocomposites containing multifunctionalized silicon nitride nanoparticles: A study on structural, thermal, electrochemical, mechanical, morphological, water repellent properties for aerospace components

AbstractThe silicon nitride (Si3N4) nanoparticles modified by 2,5‐Bis‐(4‐aminophenyl)‐1,3,4‐oxadiazole (BAPOD) investigated by scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM/EDX), transmission electron microscopy, thermogravimetry (TGA), X‐ray diffraction (XRD), and atomic force microscopy (AFM) were reinforced with polyurethane (PU). The newly synthesized formulations such as PU‐Si3N4, PU‐BAPOD, and PU‐BAPOD/Si3N4 nanocomposite coated AA7055 aluminum alloy were electrochemically studied by scanning electrochemical microscopy (SECM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) for their anticorrosion behaviors and compared with pure PU coating. EIS studies revealed excellent protection behavior for the PU‐BAPOD/Si3N4 coated AA7055 aluminum alloy in 3.5% NaCl solution. The coating resistance of PU‐BAPOD/Si3N4 nanocomposite was found to be 5995.23 kΩ.cm2 whereas lower coating resistance was observed for the pure PU coating (141.24 kΩ.cm2). It is found that the coating resistance of PU‐BAPOD/Si3N4 nanocomposite is over 42% higher than that of the PU. The measured current for aluminum ions by SECM investigation over the EP‐BAPOD/Si3N4 nanocomposite coating was very low (1.6 nA) compared with PU‐Si3N4 (7.6 nA) and pure PU coated AA7055 (14.9 nA). The surface morphological studies of the coated AA7055 by SEM/EDX analysis and XRD analysis revealed that the Si3N4 nanoparticles were enriched at the corrosion products which prevented corrosion initiation processes. The enhanced mechanical properties were noticed by mechanical analysis for the PU‐BAPOD/Si3N4 nanocomposite coating when the concentration of nanoparticles was 2 wt%. However, there was a decrease in their mechanical properties beyond 2 wt% due to the aggregation of nanoparticles in the PU coated specimen. The results showed that the newly developed PU‐BAPOD/Si3N4 nanocomposite coating possessed superior corrosion protection and enhanced hydrophobic behaviors (WCA: 149°). Therefore, it was concluded that the newly synthesized PU‐BAPOD/Si3N4 nanocomposite provided excellent barrier, hydrophobic, and mechanical properties due to the addition of BAPOD/Si3N4 nanoparticles to the PU resin which prevented the degradation of materials and helped to prolong the life of the coated AA7055 aluminum alloy.

Physical, Mechanical and Morphological Characterization of A356/Si3N4 Nanoparticles Stir Casting Composites

A356 alloy based composites are extensively used in different component industries like components of automobile parts owing to pronounced strength to weight ratio. In the current paper, A356/Si3N4 nanocomposites are fabricated by means of stir casting by varying Si3N4 reinforcement nanoparticles. Silicon Nitride (Si3N4) nanoparticle is intermixed to Al powder mechanically to develop their wettability among the particles of A356/Si3N4 nanocomposites. The Si3N4 nanoparticle is integrated by altering weight percentage. The electomechanical stirring process to produce the vortex is taken up to spread Si3N4 nanoparticles in the liquefied matrix dispensed into a permanent mould. Morphological investigation of the composite specimen is accomplished by TEM. Based on the study, it can be acquired that the strengthening by Si3N4 nanoparticles promotes the strength and hardness of the fabricated nanocomposites. The maximum tensile strength is depicted to be 319 MPa for A356/5%Si3N4 nanocomposites whereas hardness is increased from 43 HBN to 86 HBN. The physical properties such as density and porosity are also increased due to the presence of Si3N4 nanoparticles. The maximum porosity of 1.12% was predicted at 5 wt. % of Si3N4. The TEM examination discloses the presence of Si3N4 nanoparticles in the fabricated composites. Additionally, the current research guidance has ability to afford a monitor to the industrialized preparation of A356/Si3N4 nanocomposites.