Addition Of Nanoparticles Research Articles

Thermal performance of Falkner Skan model (FSM) for (GOMoS2)/(C2H6O2-H2O) 50:50% nanofluid under radiation heating source

The hybrid base solvent water (H2O) and ethylene glycol (C2H6O2) are highly use in industrial applications due to excellent solvability. Addition of hybrid nanoparticles (GO-MoS2) augments the thermal conductivity of these fluids which ultimately make them very productive. Hence, the current study aims to develop and investigate the novel hybrid nanofluid model (GO-MoS2)/(C2H6O2-H2O) through MRW (moving riga wedge) and SRW (static riga wedge) cases. The traditional Falkner Skan Model (FSM) is modified using the novel effects of solar radiations, internal heating source and fixed magnets which is associated to the concept of Riga wedge. Further, the improved thermal-physical characteristics of hybrid nanofluids will use to enhance the thermal productivity. A mathematical model is developed for the flow situation of (GO-MoS2)/(C2H6O2-H2O) and treated numerically. The results furnished through graphical way and comprehensive discussion provided. It is examined that the movement of (GO-MoS2)/(C2H6O2-H2O) reduced for MRW and observed the rapid velocity near the surface. The heat generating source and solar radiations number enhanced the performance of (GO-MoS2)/(C2H6O2-H2O) and better predicted ranges for these parameters are observed from and . Moreover, the boundary layer region becomes thin for heating source and it increased for stronger solar radiation effects. The nanoparticle amount of GO and MoS2 enhanced the model utilization while higher magnetic number and MRW number controlled the thermal boundary layer. The results for the model dynamics are noticed dominant for MRW case as compared to SRW case.

Colour changes and topography of resin modified glass ionomer cements with the addition of zinc oxide nanoparticles

Background: Resin-modified glass ionomer cement (RMGIC) is one of the restorative materials for cavity restoration in the anterior and cervical areas where aesthetics are crucial, especially for class III (anterior) cavity restorations. Adding zinc oxide nanoparticles (ZnONP) may enhance its mechanical and physical properties. Objective: This study aims to evaluate the color change of RMGIC after the addition of ZnONP as much as 5%, 10% and 15% of the total mixture of RMGIC and ZnONP powder also to examines the topography of ZnONP distribution within RMGIC’s interstitial space using scanning electron microscope (SEM). Methods: Four groups of RMGIC were studied, a control group without ZnONP powder, 3 treatment groups with ZnONP powder as much as 5%, 10%, and 15%. Each group consists of 4 cylindrical samples (diameter of 10 mm, height of 2 mm). Color change was measured using VITA Easyshade V spectrophotometer and SEM was used for topography analysis. Data were analyzed with one-way ANOVA test and Tukey HSD post hoc test. Results: One-way ANOVA test showed significant color differences (p<0.05) among all groups. Tukey HSD test showed significant color differences (p<0.05) in color change between control group and treatment groups also between group 2 and group 4. SEM observations confirmed ZnONP distribution in RMGIC’s interstitial space in treatment groups. Conclusion: Addition of 5%, 10%, and 15% ZnONP powder of the total mixture of RMGIC and ZnONP powders changed RMGIC’s color to be brighter (lightness) and more saturated (chroma) also ZnONP distributed within RMGIC’s interstitial space.

Thermodynamic, Economic and Environmental Assessment of Vapor Compression Refrigeration System Using Mono and Binary Nanolubricants (TiO2-B)

Nowadays, the need for energy is gaining significant importance. However, energy consumption in developed countries is quite high. Almost 40% of this energy consumption comes from heating, refrigeration, and air conditioning systems in buildings. Hence, even a minor enhancement in refrigeration systems will lead to energy savings on a global scale. Many studies are being conducted for this circumstance. One of these is the addition of nanoparticles to refrigerants and lubricants. In this study, the effects of mono and binary nanolubricants obtained from different nanoparticles (TiO2 and Boron) used at different concentrations (3.5 g/L and 7 g/L) in the vapor compression refrigeration system were evaluated in terms of energy, exergy, environment, and economy. As a result, a 16.47% increase in COP value was obtained in 7 g/L TiO2-B binary nanolubricant compared to pure POE. The energy consumption of the compressor in the system reduced by 13.06% in the 7 g/L TiO2-B binary nanolubricant compared to POE. A 35.20% decrease in total exergy destruction was detected in 7 g/L TiO2-B binary nanolubricant compared to POE. 43.44% increase in exergy efficiency occurred in 7 g/L TiO2-B binary nanolubricant compared to POE in the system. When the system was examined from an economic perspective, a 35.84% improvement was observed in the 7 g/L TiO2 binary nanolubricant compared to POE. When the system was examined environmentally, an 11.90% reduction was achieved in 7 g/L TiO2-B binary nanolubricant compared to POE. As a result, it is seen that significant improvements occur in the system as the concentration increases when mono and binary nanolubricants are used compared to POE.

Enhancement of optoelectronic performance by plasmonic effect in TiO2-rGO/Ag-TiO2 based on UV detectors

Abstract In this paper, the plasmonic effect in UV detectors based on titanium dioxide (TiO2) and reduced graphene oxide (rGO) is investigated. The studies have shown that a TiO2-rGO nanocomposite material is obtained by the method of hydrothermal synthesis. The addition of silver nanoparticles (NPs) and Ag- TiO2 core-shell nanostructures (NS) leads to the plasmonic effect and an increase in the optoelectronic parameters is observed. The TiO2-rGO images were obtained with the help of SEM, Raman spectroscopy found the ratio ID/IG. AFM images showed the morphology surface of the rGO. rGO sheets are visible in the SEM and AFM images. Hydrothermal synthesis results in a long-term reduction of rGO, i.e. the amount of oxygen-containing groups decreases. Raman spectroscopy shows the presence of peaks characteristic of the starting materials. The absorption properties when adding plasmonic nanoparticles to the films show changes in the absorption spectrum in the visible region of light, due to the transparency of rGO.
The current-voltage characteristics show that the presence of plasmonic particles in the nanocomposite material leads to an increase in the photoinduced current of about 94 μA, which is almost 3.0 times greater. When irradiated, the multicomponent nanocomposite material with plasmonic nanoparticles responds to light three times faster than TiO2- rGO. The obtained results can be used in the development of new light-sensitive devices for optoelectronic and photocatalytic applications.

Preparation of Highly Stable Wood with Fast Curing, Ultraviolet, and Mildew Resistance through Copper-Montmorillonite Nanoparticles Hybridized with Tung Oil.

Wood has a number of undesirable inherent properties that limit its ability to be used in a wider range of applications. For this reason, in this study, copper-montmorillonite nanoparticles were prepared from natural biomass tung oil and the natural mineral montmorillonite by the ion exchange method. Modified wood with tung oil intercalated with copper-montmorillonite was prepared by a simple and environmentally friendly impregnation and natural curing process. The natural curing rate of tung oil was greatly accelerated by the addition of copper-montmorillonite nanoparticles. The surface contact angle of the wood increased from 85.0° to 152.2° after copper-montmorillonite-tung oil treatment, and remarkably, it remained at 144.2° after 180 s. After 192 h of immersion, the water absorption decreased by 90.0% compared with the control group, of which the resistance to swelling was as high as 59.00%, which significantly improved the dimensional stability of the wood. After 15 days of ultraviolet irradiation, the copper-montmorillonite-tung oil-treated wood showed a 68.89% reduction in redness value compared to the control and a significant increase in ultraviolet resistance. Copper-montmorillonite-tung oil-treated wood showed greatly enhanced effectiveness against mildew. On the eighth day of Aspergillus niger infestation, the control wood was already full of mildew, whereas the copper-montmorillonite-tung oil-treated wood was not infested with mildew. In particular, after 28 days of infestation by Penicillium oryzae, the modified wood remained free of the fungus, with 100% mildew prevention efficiency. In addition, after 2 weeks of leaching, the leaching rate of the impregnated material was only 0.22%, facilitating long-term protection of the wood. The present study by the copper-montmorillonite synergistic tung oil treatment strategy provides innovative methods and potential ideas for extending the service life of wood products and high-value utilization of wood and also has the potential to scale up wood protection.

A coarse-grained molecular dynamics simulation on the mechanical and thermal properties of natural rubber composites reinforced by fullerene nanoparticles.

The influence of fullerene C60 on the mechanical and thermal properties of natural rubber was systematically investigated using coarse-grained molecular dynamics simulations. The tensile results demonstrate that systems with longer NR chains exhibit reduced tensile strength. Moreover, the addition of C60 nanoparticles significantly enhanced the mechanical properties, with Young's modulus, yield strength, and tensile strength increasing by approximately 24.03%, 23.21%, and 51.61%, respectively, at a C60 concentration of 0.2 phr under a strain rate of 1e-6. Furthermore, the mechanical response was found to be strain rate-dependent, with higher strain rates leading to increased Young's modulus, yield strength, and tensile strength. Therefore, excessively high strain rates should be avoided in simulations to ensure consistency with real conditions. In terms of thermal properties, the addition of C60 nanoparticles was shown to significantly improve the thermal conductivity of natural rubber, with the optimal enhancement of 17.17% achieved at an inclusion level of approximately 0.1 phr. A comprehensive microstructural analysis, including mean square displacement, radial distribution function, coordination number, and interaction energy, revealed the reinforcement mechanisms of C60 on the mechanical and thermal properties of the nanocomposites. This study provides valuable insights into the rational design and fabrication of fullerene-reinforced natural rubber nanocomposites with superior mechanical and thermal performance. In this study, coarse-grained molecular dynamics simulations were performed using the LAMMPS software. The system used the real unit system with periodic boundary conditions. The interatomic interactions were described using the lj/expand model. The simulations were conducted at a temperature of 300K with a time step of 1fs.

Bioactivity and Mechanical Performance of Centrifugally Spun Poly(D,L‐Lactide)/Poly(3‐Hydroxybutyrate) Submicrometric Fibers Containing Zinc Oxide and Hydroxyapatite Nanostructures

ABSTRACTThis study investigates the morphological, thermal, mechanical, and bioactive properties of centrifugally spun fibrous composites made from poly(D,L‐lactide)/poly(3‐hydroxybutyrate) (PLA/PHB) blends with zinc oxide (ZnO) and hydroxyapatite (Hap) nanoparticles. A 75/25 PLA/PHB weight ratio was chosen to balance mechanical and thermal properties. The precursor solution viscosities ranged from 0.25 to 0.50 Pa s, increasing with nanoparticle incorporation probably due to polymer‐nanoparticle interactions. SEM revealed a uniform fibrous morphology, with diameters of 1.21 for PLA/PHB, 2.65 for PLA/ZnO/Hap, and 1.80 μm for PLA/PHB/ZnO/Hap. TGA showed two‐step degradation for PLA/PHB fibers, while PLA/PHB/ZnO/Hap degraded in a single step at 249°C, leaving a residue of 9.95%. DSC indicated partial miscibility, with cold crystallization at 85°C (enthalpy: 7.72 J/g), slightly modified by nanoparticle addition. PLA/PHB fibers achieved a Young's modulus of 24.96 ± 3.91 MPa, three times that of pure PLA, but adding ZnO and Hap reduced modulus and tensile strength to 6.03 and 0.29 MPa, retaining suitability for biomedical applications. PLA/PHB/ZnO/Hap fibers exhibited 90% Escherichia coli growth inhibition and enhanced MC3T3‐E1 cell viability by 120% on day 7. These results highlight their potential for antimicrobial, biocompatible medical devices.

Nanoparticle-Doped Antibacterial and Antifungal Coatings.

Antimicrobial polymeric coatings rely not only on their surface functionalities but also on nanoparticles (NPs). Antimicrobial coatings gain their properties from the addition of NPs into a polymeric matrix. NPs that have been used include metal-based NPs, metal oxide NPs, carbon-based nanomaterials, and organic NPs. Copper NPs and silver NPs exhibit antibacterial and antifungal properties. So, when present in coatings, they will release metal ions with the combined effect of having bacteriostatic/bactericidal properties, preventing the growth of pathogens on surfaces covered by these nano-enhanced films. In addition, metal oxide NPs such as titanium dioxide NPs (TiO2 NPs) and zinc oxide NPs (ZnONPs) are used as NPs in antimicrobial polymeric coatings. Under UV irradiation, these NPs show photocatalytic properties that lead to the production of reactive oxygen species (ROS) when exposed to UV radiation. After various forms of nano-carbon materials were successfully developed over the past decade, they and their derivatives from graphite/nanotubes, and composite sheets have been receiving more attention because they share an extremely large surface area, excellent mechanical strength, etc. These NPs not only show the ability to cause oxidative stress but also have the ability to release antimicrobial chemicals under control, resulting in long-lasting antibacterial action. The effectiveness and life spans of the antifouling performance of a variety of polymeric materials have been improved by adding nano-sized particles to those coatings.

Hybrid Solder Joints: Viscosity Studies of the Nanocomposite Flux with Fe Nanoparticle Additions

Viscosity is one of the most important physical characteristics of choosing a flux for solder paste. However, not in all cases do the producers give information about the viscosity of commercial flux. A recent promising trend is to mix various kinds of nanoparticles with solder paste or flux and investigate the produced solder joints. However, the impact of nanosized inclusions on the viscosity of the flux has practically not been investigated. In this study, the temperature and shear rate dependencies of the viscosity of the nanocomposite flux were measured. For this purpose, the commercial flux has been mixed with Fe nanoparticles up to 2.0 wt.% of inclusions. It has been shown that viscosity increases with the addition of Fe nanoparticles. However, it is valid only for first heating up to circa 340 K. The viscosity values of the flux with and without nanosized inclusions are practically similar by further heating to 360 K as well as by subsequent cooling. Additionally, the performed differential thermal analysis has shown the heat effects, which are in good agreement with viscosity behavior.

High-Performance Hydrogen Sensing at Room Temperature via Nb-Doped Titanium Oxide Thin Films Fabricated by Micro-Arc Oxidation.

Metal oxide semiconductor (MOS) hydrogen sensors offer advantages, such as high sensitivity and fast response, but their challenges remain in achieving low-cost fabrication and stable operation at room temperature. This study investigates Nb-doped TiO2 (NTO) thin films prepared via a one-step micro-arc oxidation (MAO) with the addition of Nb2O5 nanoparticles into the electrolyte for room-temperature hydrogen sensing. The characterization results revealed that the incorporation of Nb2O5 altered the film's morphology and phase composition, increasing the Nb content and forming a homogeneous composite thin film. Hydrogen sensing tests demonstrated that the NTO samples exhibited significantly improved sensitivity, selectivity, and stability compared to undoped TiO2. Among the fabricated samples, NTO thin film prepared at Nb2O5 concentration of 6 g/L (NTO-6) showed the best performance, with a broad detection range, excellent sensitivity, rapid response, and good specificity to hydrogen. A strong linear relationship between response values and hydrogen concentration (10-1000 ppm) highlights its potential for precise hydrogen detection. The enhanced hydrogen sensing mechanism of NTO thin films primarily stems from the influence of Nb2O5; nanoparticles doping in the anatase-phase TiO2 structure on the semiconductor surface depletion layer, as well as the improved charge transfer and additional adsorption sites provided by the Nb/Ti composite metal oxides, such as TiNb2O7 and Ti0.95Nb0.95O4. This study demonstrates the potential of MAO-fabricated Nb-doped TiO2 thin films as efficient and reliable hydrogen sensors operating at room temperature, offering a pathway for novel gas-sensing technologies to support clean energy applications.

Zinc-doped hydroxyapatite loaded chitosan gelatin nanocomposite scaffolds as a promising platform for bone regeneration

The advancement in the arena of bone tissue engineering persuades us to develop novel nanocomposite scaffolds in order to improve antibacterial, osteogenic, and angiogenic properties that show resemblance to natural bone extracellular matrix. Here, we focused on the development of novel zinc-doped hydroxyapatite (ZnHAP) nanoparticles (1, 2 and 3 wt%; size: 50-60 nm) incorporated chitosan-gelatin (CG) nanocomposite scaffold, with an interconnected porous structure. The addition of ZnHAP nanoparticles decreases the pore size (∼30 µm) of the CG scaffolds. It was observed that with the increase in the concentration of ZnHAP nanoparticles (3 wt%) in CG scaffolds, the swelling ratio (1760% ± 2.0%), porosity (71% ± 0.98%) and degradation rate (35%) decreased, whereas mechanical property (1 MPa) increased, which was better as compared to control (CG) samples. Similarly, the high deposition of apatite crystals especially CG-ZnHAP3nanocomposite scaffold revealed the excellent osteoconductive potential among all other scaffolds. MC3T3-E1 osteoblastic cells seeded with CG-ZnHAP nanocomposite scaffolds depicted better cell adhesion, proliferation and differentiation to osteogenic lineages. Finally, the chorioallantoic membrane (CAM) assay revealed better angiogenesis of ZnHAP nanoparticles (3 wt%) loaded CG scaffolds supporting vascularization after 7th day incubation in the CAM area. Overall, the results showed that the CG-ZnHAP3nanocomposite scaffold could be a potential candidate for bone defect repair.

Advances in Blade-Coated Organic Photovoltaics

Organic photovoltaics (OPVs) are a type of solar cell technology that uses organic semiconducting materials to convert sunlight into electricity. Unlike traditional silicon-based solar cells, OPVs are lightweight, flexible, and can be fabricated using cost-effective solution-processing techniques such as blade coating, enabling large-area device fabrication and is compatible with roll-to-roll manufacturing, making it ideal for OPV production. However, key challenges for OPVs, such as achieving high efficiency and scalability, maintaining film uniformity, enhancing material stability, optimizing processing techniques, mitigating environmental and health impacts, improving charge transport and reducing recombination losses, and overcoming performance degradation in large-area production are still under investigation. Recent developments include high-efficiency copolymer donors, ternary additives for optimized morphology, and the integration of novel interlayers and electrodes. Scalable processes such as accelerated blade coating and green solvents like o-methylanisole are also explored, highlighting their role in enhancing efficiency, stability, and sustainability. Additionally, insights into nanoparticle additives, solvent engineering, and molecular design underscore the potential for blade-coated OPVs to achieve high performance while maintaining environmental compatibility. These advancements collectively address challenges in efficiency and scalability, paving the way for OPVs to meet industrial demands and contribute to a greener energy landscape.

Synergetic effects of nano-boehmite and Y nano-zeolite on catalytic cracking of residue oil

Boehmite nanoparticles and NaY nanozeolite were synthesized by co-precipitation and hydrothermal methods, respectively, and characterized by XRD, FT-IR, TG-DTA, BET, and SEM techniques. XRD and BET analyses demonstrated the formation of boehmite nanoparticles with a surface area of 350 m2/g and high crystallinity NaY nanozeolite with a surface area of 957 m2/g. In order to evaluate the effect of the content of the mesoporous boehmite nanoparticles on the catalytic performance of the Residue Fluid Catalytic Cracking (RFCC) catalyst, alumina active matrix-based and silica inactive matrix-based catalysts were prepared. Results actually demonstrated that the acidity of the zeolite composition improved with the addition of boehmite nanoparticles. On the other hand, in equal zeolite content, the alumina active matrix-based catalyst possessed higher acidity (NC30B20, 3.44 mmol NH3/g catalyst) than the silica inactive matrix-based catalyst (NC30B0, 2.31 mmol NH3/g catalyst). Microactivity tests (MAT) demonstrated that, with equal zeolite content, active matrix-based catalysts exhibited higher catalytic performance than inactive matrix-based catalyst. Furthermore, the active matrix-based catalyst (NC30B20) with a surface area of 370 m2/g showed the optimum catalytic performance in the RFCC process. The synthesized NC30B20 catalyst with 20 wt% mesoporous boehmite nanoparticles as an active matrix and 30 wt% zeolite nanoparticles balanced with silica had the highest gasoline yield (42 wt%) and gasoline selectivity (65.1 wt%). The catalytic performance test results showed that in equal MAT conversion (almost 64 wt%), the synthesized NC30B20 catalyst had higher catalytic performance than the commercial catalyst.

Numerical Investigations of Superconducting Material Cooling Using Buoyancy-Driven Heat Transport in Cryogenic Nanofluids

This study explores the effect of nanoparticle addition on the overall heat-carrying capacity of base liquid nitrogen in natural convection. Moreover, the work also addresses the nanoparticle sedimentation problem that is prominent in natural convection and proposes subtle modifications in heat source location to avoid sedimentation. For this, a 6 mm superconducting material is immersed in a cooling tub filled with liquid nitrogen. The cooling capacity of cryogenic fluids without boiling is considerably low. Hence, the alumina, silicon oxide, and titania nanoparticles are suspended in the base liquid nitrogen. A computational model, which relies on phase-averaged Eulerian tracking of nanoparticle suspensions, is employed to accurately predict the enhancement in heat transfer characteristics. Furthermore, the study addresses the influence of nanoparticle sedimentation in natural convection and proposes modifications to the cooling domain and superconducting material locations to mitigate sedimentation issues. The findings reveal a remarkable 70% increase in the heat transfer coefficient for 0.5% alumina nanoparticles suspension in the base liquid nitrogen. These results demonstrate the potential for significantly improving heat transfer performance in superconducting systems while minimizing the adverse effects of nanoparticle sedimentation.

Zinc-Reduced Anticorrosive Primers—Water-Based Versus Solvent-Based

Coating systems used for anticorrosion protection usually consist of a primer, intermediate layers, and topcoats. Zinc-rich primers, which serve as cathodic and barrier protection, are widely used for the corrosion protection of steel structures. Due to the fact that the functioning of the above-mentioned coatings is related to the conduction of galvanic current, these types of coatings are highly pigmented with zinc (up to 80 wt% in the dry coating). This may result not only in a deterioration of the performance of the coating system but also have a negative impact on the environment. Taking the above into account, solvent-based and water-based organic epoxy primers with zinc content reduced to approximately 50% have been developed. Zinc pigments of different shapes and with different surface treatments were used in the primers, as well as pigments without chemical treatment but with the addition of nanoparticles. It was found that, depending on the type of zinc pigment, both the developed solvent-based and water-based primers demonstrate good protective properties comparable to traditional zinc-rich coatings. Water-based paints tend to absorb more moisture compared to solvent-based systems, but their water uptake reversibility is limited. Moreover, the organic treatment of zinc flakes helps to improve this water uptake reversibility, improving the mechanical properties of coatings.

Optimization of Toxicity, Biodegradability, and Skin Irritation in Formulations Containing Mixtures of Anionic and Nonionic Surfactants Combined with Silica Nanoparticles.

Surfactants play a crucial role in various industrial applications, including detergents and personal care products. However, their widespread use raises concerns due to their potential environmental impact and health risks, particularly in aquatic ecosystems, where they can disrupt the balance of marine life and accumulate in water sources, posing challenges to sustainable development. This study investigates the environmental and health implications of anionic and nonionic surfactants, focusing on their toxicity, biodegradation, and skin irritation potential profiles, especially when combined with silica nanoparticles. Toxicity assessments were conducted using bacteria Vibrio fischeri for aquatic toxicity and Lepidium sativum seeds for terrestrial plant effects, revealing that individual surfactants like the anionic alkyl ether carboxylic acid EC-R12-14E3 exhibit high toxicity levels, while the nonionic fatty-alcohol ethoxylate FAE-R12-14E11 shows comparatively lower environmental impact. The toxicity of surfactant mixtures was analysed, revealing both antagonistic and synergistic effects depending on the surfactants used. The addition of silica nanoparticles generally mitigates the overall toxicity of surfactants, whether used individually or in mixtures. Biodegradation studies followed OECD 301E and 301F guidelines, indicating that individual surfactants generally meet or approach the mineralization threshold, whereas the addition of nanoparticles reduced biodegradation efficacy. Potential skin irritation was predicted through the zein number (ZN), finding that some surfactant combinations with silica nanoparticles reduce irritation levels, highlighting their potential for safer formulation in products that come into direct contact with the skin. Overall, the findings emphasize the need for careful selection of surfactant mixtures and nanoparticle integration to minimize environmental toxicity and potential skin irritation and increase their biodegradability.

A Multi-Phase Analytical Model for Effective Electrical Conductivity of Polymer Matrix Composites Containing Micro-SiC Whiskers and Nano-Carbon Black Hybrids.

Multifunctional polymer composites containing micro/nano hybrid reinforcements have attracted intensive attention in the field of materials science and engineering. This paper develops a multi-phase analytical model for investigating the effective electrical conductivity of micro-silicon carbide (SiC) whisker/nano-carbon black (CB) polymer composites. First, CB nanoparticles are dispersed within the non-conducting epoxy to achieve a conductive CB-filled nanocomposite and its electrical conductivity is predicted. Some critical microstructures such as volume percentage and size of nanoparticles, and interphase characteristics surrounding the CB are micromechanically captured. Next, the electrical conductivity of randomly oriented SiC-containing composites in which the nanocomposite and whisker are considered as the matrix and reinforcement phases, respectively, is estimated. Influences of whisker aspect ratio and volume fraction on the effective electrical conductivity of the SiC/CB-containing polymer composites are explored. Some comparison studies are performed to validate the accuracy of the model. It is observed before the percolation threshold that the addition of nanoparticles with a uniform dispersion can improve the electrical conductivity of the polymer composites containing SiC/CB hybrids. Moreover, the results show that the electrical conductivity is more enhanced by the decrease in nanoparticle size. Interestingly, the composite percolation threshold is significantly reduced when SiC whiskers with a higher aspect ratio are added. This work will be favorable for the design of electro-conductive polymer composites with high performances.

Enhanced mechanical properties of Nb-18.7Si alloy by addition of ceramic nano particles for microstructural control

The phase composition, microstructure and mechanical properties of arc-melted eutectic Nb-18.7Si (at.-%) alloys with different nano-ceramic particle addition (Al2O3, TiC, SiC, 5 mol.-%) were investigated. The results showed that ceramic Al2O3 and TiC nanoparticle are thermally and chemically stable and can be used to tailor phase composition and refine the microstructure, while SiC dissolves completely in the melt. Al2O3 and TiC nanoparticle were found mainly in two different areas: (1) at grain boundaries of eutectic structures and (2) on the phase boundaries of silicides inside the eutectics. The presence of the particles refined the microstructure down to nano-scale lamellae by functioning as heterogeneous nuclei for the silicide phase. Without nano particle addition, the Nb-18.7Si alloy was mainly composed of Nb solid solution (Nbss) and Nb3Si. The addition of 5 mol.-% Al2O3 promoted the decomposition of the Nb3Si phase and an ultrafine nano-scale lamellar eutectic structure (Nbss + α-Nb5Si3) formed. With the addition of 5 mol.-% TiC, primary Nb3Si and coarse Nbss were observed, as well as fine eutectic Nbss + γ-Nb5Si3 structures. The complete dissolution of SiC led to a hypereutectic alloy with primary Nb3Si and γ-Nb5Si3 phase, coarse Nbss and eutectic Nbss + γ-Nb5Si3 structures. The compressive strength was increased from 3068 MPa to 3446 MPa by adding 5 mol.-% Al2O3 due to the formation of the high strength α-Nb5Si3 phase, the ultrafine nano-scale lamellar structures of Nbss + α-Nb5Si3 and the strong interface of Nbss/α-Nb5Si3. However, the small grain size of the Nbss phase was not effective in inhibiting crack propagation. Crack bridging and branching seem to be important mechanisms at the Nbss phase to inhibit crack propagation. Therefore, the size and distribution of Nbss play a key role. The results indicate that a continuous Nbss phase with embedded silicide phase and coarse Nbss phases can inhibit crack propagation.

COMPARISON OF THERMOPHYSICAL PROPERTY MODELS OF NANOFLUIDS FOR THERMAL PERFORMANCE IN A MICROCHANNEL

Different thermophysical property models for nanofluids and several dimensionless parameters have been compared in the case of heat transfer for laminar flow in a microchannel. Addition of nanoparticles, including Al<sub>2</sub>O<sub>3</sub>, CuO, and TiO<sub>2</sub>, to water has been considered for volumetric concentrations up to φ = 7%. The numerical analyses have been conducted via the finite difference method for a transient regime. The heat transfer results have been obtained in terms of the interfacial heat flux, bulk temperature, and the Nusselt number. The parametrical effects of Péclet number values, wall thickness ratios, thermal diffusivity ratios, thermal conductivity ratios, and Brinkman number values have been evaluated. Based on the results, the influence of axial conduction has been clearly observed for lower Péclet numbers. Furthermore, the increment of the thermal conductivity ratio and the decrement of the wall thickness ratio have enhanced thermal performance. Nevertheless, the thermal characteristics have not been significantly influenced by the thermal diffusivity ratio. The viscous dissipation has altered the heat transfer direction due to the change in the Brinkman number. The required time to reach the steady state for numerical solution increased because of decreasing Brinkman number values. Heat transfer augmentation has been obviously obtained due to ascending nanofluid volumetric concentrations. The CuO nanoparticles have been recommended owing to their higher thermal performance for the fixed volumetric concentration. According to the thermophysical models compared for each type of nanoparticles, the models for Al<sub>2</sub>O<sub>3</sub> nanoparticles presented the closest results to each other. Nonetheless, it has been observed that one model for CuO nanoparticles and one model for TiO<sub>2</sub> nanoparticles are inadequate.

Enhanced wear resistance, hydrophobic properties and corrosion resistance of plasma electrolyte oxidation coatings on Ti6Al4V alloys via addition of ZrO2 nanoparticles

Enhanced wear resistance, hydrophobic properties and corrosion resistance of plasma electrolyte oxidation coatings on Ti6Al4V alloys via addition of ZrO2 nanoparticles