Values Of Nanocomposites Research Articles

Photodegrading rhodamine B dye with cobalt ferrite-graphitic carbon nitride (CoFe2O4/g-C3N4) composite

The present research utilizes a sol-gel approach to create a CoFe2O4/g-C3N4 nanocomposite (NC) and explored several analytical methods to evaluate physical, chemical and optical based characteristics via XRD, FTIR, UV–vis, SEM/EDS and XPS for the prepared pure CoFe2O4, g-C3N4, and CoFe2O4/g-C3N4 NC. The XRD results show that the prepared g-C3N4, CoFe2O4, exhibits hexagonal and cubic phases respectively, whereas the g-C3N4/CoFe2O4 NC exhibit mixing of two phases. The energy band gaps for pure g-C3N4, CoFe2O4 and g-C3N4/CoFe2O4 NC values are viz., 2.75, 1.3, and 2.4 eV. As photocatalysts, synthesized materials were utilized for the decomposition of Rhodamine-B (RhB) dye. Finally, the CoFe2O4/g-C3N4 NC showed good performance of photocatalysis for RhB dye disintegration under the stimulus of visible light. According to the induced visible light, the rate at which the photocatalytic degradation occurs for the CoFe2O4/g-C3N4 NC was found to be 57% in 120 min and this is greater when compared with pure catalysts like CoFe2O4 (28%) and g-C3N4 (10%). These outcomes suggest that the prepared NC have efficiently worked during the photocatalytic process compared with its pure materials.

Synthesis of Chitosan-TiO2 Nanocomposite for Efficient Cr(VI) Removal from Contaminated Wastewater Sorption Kinetics, Thermodynamics and Mechanism.

A photolysis method was used to prepare a nanocomposite adsorbent (Chitosan-TiO2) and was tested for Cr(VI) removal from aqueous solution. The produce nanocomposite was investigated using, XRD, BET, FTIR, FESEM-EDX and TEM before and after Cr(VI) adsorption. The XRD results shows prepared anatase phase of TiO2 with 12 nm. According to BET measurements, the surface area of the TiO2/chitosan nanocomposite was lower and archived to 26 m2/g, while the TEM and FESEM images show a uniform distribution of TiO2 throughout the chitosan matrix. Adsorption and kinetic experiments were run in batch system under different conditions of pH, contact time, adsorbent dosage and temperature. Experimental Cr(VI) adsorption equilibrium and kinetics data fitted well to Langmuir model. The calculated Langmuir maximum adsorption capacity (qmax) value of nanocomposite was 488 mg/g. Moreover, the highest quantity of Cr(VI) uptake was achieved of pH = 2 and 45℃ and TiO2 and CS-TiO2 had respective removal efficiencies of 94 and 87.5%. The thermodynamic parameters of Cr(VI) adsorption by nanocomposite affirm the spontaneous and endothermic nature of process. Chromium adsorption mechanism by CS-TiO2 nanocomposite were proposed and discussed.

Synthesis of Moringa oleifera coated silver-containing nanocomposites of a new methacrylate polymer having pendant fluoroarylketone by hydrothermal technique and investigation of thermal, optical, dielectric and biological properties

Firstly, silver nanoparticles were synthesized by green synthesis method from Moringa oleifera extract. Nanocomposites containing newly synthesized methacrylate polymer, poly 2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate (PFPAMA) and Ag nanoparticles from M. oleifera in different mass ratios (1, 3, and 5 wt%) were synthesized using the hydrothermal method. The morphological and structural properties of the materials have been examined by SEM, FTIR, UV, TGA, and XRD techniques. The activation energies (Ea ) related to thermal decomposition of the nanocomposites were estimated by the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods by using non-isothermal TGA experiments. The thermal stability, glass transition temperature (Tg ), and the thermal decomposition activation energy (Ea ) values of nanocomposites were increased by increasing the Ag nanoparticles amount on the composite. The dielectric constant (ε′), the dielectric loss factor (ε″) and ac conductivity of neat PFPAMA and nanocomposites were also measured for the frequency range of 100 Hz to 2 kHz at 25 °C. It was seen that the frequency dependence of the dielectric constant and dielectric loss factor decreased with increasing frequency. The biological activities of nanocomposites against gram-positive (Staphylococcus aureus), gram-negative (Escherichia coli) bacteria and Candida krusei yeast were also tested. The antibacterial effect increased against both bacterial species as the amount of Ag nanoparticles from M. oleifera in the nanocomposites increased. In addition, the wound healing properties of nanocomposites were investigated by the scratch wound test.

Effect of modification on thermal stabilities and thermal degradation kinetics of poly(buthylmethacrylate)/multi-walled carbon nanotube nanocomposites

ABSTRACT Modified multi-walled carbon nanotubes (MWCNTs) were prepared from commercially purchased MWCNTs with different chemical reactions. Nanocomposites were synthesised by the solvent casting method. The effects of functional groups, filling ratios and surfactants on thermal properties of nanocomposites were investigated. The structural, thermal and morphological properties of MWCNT and nanocomposites were investigated using Fourier transform infrared spectrophotometer, Brunauer–Emmett–Teller surface area measuring device, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The novel increases in the thermal properties of poly(butylmethacrylate) (PBMA) were observed by adding MWCNT samples into a PBMA matrix. T g values of nanocomposites were higher than those of PBMA films. The data obtained from the thermograms of nanocomposites at different heating rates were analysed with Kissinger, FWO and Friedman equations. The activation energies of the nanocomposites were higher than those of PBMA films.

Investigation of friction and wear behavior of hydroxyl-functionalized graphene nanoplatelets filled elastomer nanocomposites

The use of unfilled pure elastomer parts is limited in friction wheels, roller tires, sealing elements, and dynamic friction air suspension applications requiring high wear resistance. This study investigates the mechanical and tribological properties of new nanocomposites obtained by adding hydroxyl-functionalized graphene nanoplatelets at 1, 4, and 8 phr (parts per hundred rubber) ratios to the carbon black filled main rubber compound of sealing elements designed for axle hubs. The synergistic effect of nanofiller materials on the wear behavior of nanocomposites was tested with a block-on-ring wear tester under dry sliding conditions at 1000 rpm and 15 N normal load conditions. The worn surfaces were examined with scanning electron microscopy and circularly polarized light–differential interference contrast topology microscopy to reveal the wear mechanism. The addition of functionalized graphene nanoplatelets to the nanocomposite compound caused significant changes in tensile strength and elongation values by changing the cross-link density. The wear rate of nanocomposites prepared with graphene nanoplatelets at 1, 4, and 8 phr ratios was 11.15%, 25.24%, and 36.54% lower than the main rubber mixture used, respectively. While the hysteresis loss decreased by 14.83% at 1 phr, this value increased in other filler ratios. Significant differences in temperature change occurred as the amount of filler increased. After the test, the temperature values of nanocomposites with 1 and 4 phr filler ratios were between about 85–89°C, while it was measured as 99°C in nanocomposites with 8 phr filler ratios. It has been observed that the homogeneous distribution of two-dimensional carbon allotropes such as graphene nanoplatelet added to the rubber matrix at the optimum rate will improve tribological properties such as better surface lubrication, low wear rate, and low friction coefficient.

High Breakdown Strength and Energy Storage Density in Aligned SrTiO3@SiO2 Core-Shell Platelets Incorporated Polymer Composites.

Dielectric nanocomposites with high energy storage density (Ue) have a strong attraction to high-pulse film energy-storage capacitors. Nevertheless, low breakdown strengths (Eb) and electric displacement difference (Dmax-Drem) values of nanocomposites with incorporating the randomly distributed high dielectric constant additions, give rise to low Ue, thereby hindering the development of energy-storage capacitors. In this study, we report on newly designed SrTiO3@SiO2 platelets/PVDF textured composites with excellent capacitive energy storage performance. SrTiO3@SiO2 platelets are well oriented in the PVDF when perpendicular to the electric field with the assistance of shear force in the flow drawing process to establish microscopic barriers in an inorganic–polymer composite that is able to substantially improve the Eb of composites and enhance the Ue accordingly. Finite element simulation demonstrates that the introduction of the highly insulating SiO2 coating onto the SrTiO3 platelets effectively alleviates the interface dielectric mismatch between filler and PVDF matrix, resulting in a reduction in the interface electric field distortion. The obtained composite film with optimized paraelectric SrTiO3@SiO2 platelets (1 vol%) exhibited a maximum Dmax-Drem value of 9.14 μC cm−2 and a maximum Ue value of 14.4 J cm−3 at enhanced Eb of 402 MV m−1, which are significantly superior to neat PVDF and existing dielectric nanocomposites.

Graphene-Based TiO2 Nanocomposite for Photocatalytic Degradation of Dyes in Aqueous Solution under Solar-Like Radiation

This study presents a novel method for the development of TiO2/reduced graphene oxide (rGO) nanocomposites for photocatalytic degradation of dyes in an aqueous solution. The synergistic integration of rGO and TiO2, through the formation of Ti–O–C bonds, offers an interesting opportunity to design photocatalyst nanocomposite materials with the maximum absorption shift to the visible region of the spectra, where photodegradation can be activated not only with UV but also with the visible part of natural solar irradiation. TiO2@rGO nanocomposites with different content of rGO have been self-assembled by the hydrothermal method followed by calcination treatment. The morphological and structural analysis of the synthesized photocatalysts was performed by FTIR, XRD, XPS, UV-Vis DRS, SEM/EDX, and Raman spectroscopy. The effectiveness of the synthesized nanocomposites as photocatalysts was examined through the photodegradation of methylene blue (MB) and rhodamine B (RhB) dye under artificial solar-like radiation. The influence of rGO concentration (5 and 15 wt.%) on TiO2 performance for photodegradation of the different dyes was monitored by UV-Vis spectroscopy. The obtained results showed that the synthesized TiO2@rGO nanocomposites significantly increased the decomposition of RhB and MB compared to the synthesized TiO2 photocatalyst. Furthermore, TiO2@rGO nanocomposite with high contents of rGO (15 wt.%) presented an improved performance in photodegradation of MB (98.1%) and RhB (99.8%) after 120 min of exposition to solar-like radiation. These results could be mainly attributed to the decrease of the bandgap of synthesized TiO2@rGO nanocomposites with the increased contents of rGO. Energy gap (Eg) values of nanocomposites are 2.71 eV and 3.03 eV, when pure TiO2 particles have 3.15 eV. These results show the potential of graphene-based TiO2 nanocomposite to be explored as a highly efficient solar light-driven photocatalyst for water purification.

Comparative evaluation of manganese oxide and its graphene oxide nanocomposite as polyphenol oxidase mimics

Manganese oxide nanoparticles (Mn3O4 NPs) are widely used in catalytic reactions due to their electron transfer activity. In the present study, Mn3O4 NPs, graphene oxide (GO) and their nanocomposite (NC) were synthesized by sol-gel, modified Hummer’s and ultra-sonication methods respectively. Their polyphenol oxidase (PPO) mimic activity was comparatively analyzed. The synthesized NPs and NC were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy-Energy dispersive spectroscopy (SEM-EDS), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS) techniques. FT-IR spectra and elemental analysis of NC revealed the existence of oxygen containing functional groups of pristine GO and Mn-O bonds of Mn3O4 NPs. Saturation magnetization value of NC was lower than pristine Mn3O4 due to the presence of non-magnetic GO. XRD analysis of synthesized materials depicted crystalline nature. TEM micrographs of NC showed Mn3O4 NPs with average particle size of 10 nm on the surface of GO with low aggregation and better dispersion. NC possessed higher BET surface area (45.12 m2/g) than pristine Mn3O4 NPs (25.81 m2/g) which could be attributed to inhibited aggregation of Mn3O4 NPs in the presence of GO. The PPO-like activity of synthesized compounds were analysed using catechol as a substrate. Pristine Mn3O4 NPs were observed to be the best PPO mimic followed by NC. Presence of GO in NC, hindered the electron transfer process. Kinetic analysis under optimized conditions indicated higher binding affinity of NC as compared to Mn3O4 with Michaelis constant values of 0.93 mM and 0.7 mM, respectively. The results of present studies have demonstrated potential of Mn3O4 NPs and NC as PPO mimics.

Synthesis and thermal characterization of monosubstituted octaphenyl POSS/polystyrene nanocomposites

Four novel polyhedral oligomeric silsesquioxanes/polystyrene (POSS/PS) nanocomposites, having formula R7R′1(SiO1.5)8/PS (where R = C6H5– and R′ = p-C6H4-X, with X = –CH3, –OCH3, –F, –Cl) were synthesized by in situ polymerization of styrene, in the presence of 5% w/w of POSS. The obtained nanocomposites were characterized by 1H-NMR spectroscopy and by the glass transition temperature (Tg) determination. The thermal degradations of nanocomposites were thus carried out in thermobalance, in the scanning mode, in the temperature range r.t.—700 °C, in both flowing nitrogen and static air atmospheres. Temperature at 5% mass loss (T5%) was determined as parameter measuring the resistance to thermal degradation. The obtained T5% values of nanocomposites were largely higher than those found for PS, which was also degraded for comparison in the same experimental conditions, thus indicating higher resistance to thermal degradation in respect to neat polymer. Also, the sameness of nanocomposites T5% values was interpreted and explained.

Effect of Milling Time on the Microstructure, Physical and Mechanical Properties of Al-Al₂O₃ Nanocomposite Synthesized by Ball Milling and Powder Metallurgy.

The effect of milling time on the morphology, microstructure, physical and mechanical properties of pure Al-5 wt % Al2O3 (Al-5Al2O3) has been investigated. Al-5Al2O3 nanocomposites were fabricated using ball milling in a powder metallurgy route. The increase in the milling time resulted in the homogenous dispersion of 5 wt % Al2O3 nanoparticles, the reduction of particle clustering, and the reduction of distances between the composite particles. The significant grain refining during milling was revealed which showed as a reduction of particle size resulting from longer milling time. X-Ray diffraction (XRD) analysis of the nanocomposite powders also showed that designated ball milling contributes to the crystalline refining and accumulation of internal stress due to induced severe plastic deformation of the particles. It can be argued that these morphological and microstructural variations of nanocomposite powders induced by designated ball milling time was found to contribute to an improvement in the density, densification, micro-hardness (HV), nano-hardness (HN), and Young’s modulus (E) of Al-5Al2O3 nanocomposites. HV, HN, and E values of nanocomposites were increased by ~48%, 46%, and 40%, after 12 h of milling, respectively.

Preparation and characterization of platinum (Pt) and palladium (Pd) nanoparticle decorated graphene sheets and their utilization for the elimination of basic fuchsin and indigo carmine dyes

In this study, graphene nano sheets, prepared with chemical oxidation and reduction routes via modified-Hummer method, were successfully decorated with platinum (Pt) and palladium (Pd) nanoparticles. Structural and morphological features of resulted graphene-metal nanocomposites were characterized with FT-IR, XRD, SEM and TEM methods. Anti-oxidant activity (AOA) values of nanocomposites were determined. The IC50 values of Pt-graphene and Pd-graphene nanocomposites were found to be 46.1 and 90.2 μg/mL, respectively based on the ABTS method and 80.2 and 143.7 μg/mL according to the DPPH method. It was found that the graphene-metal nanocomposites exhibited superior free radical scavenging activity compared to several types of noble metal nano particles although the nanocomposites consist of much lower amount of active metal sites than the nano-crystalline metal powders. It was consequently reported that the graphene-metal nanocomposites could be successfully used for the photocatalytic elimination of fuchsin and indigo carmine dyes under light irradiation.

Isoconversional kinetic analysis of DSC data on nonisothermal crystallization: Estimation of Hoffman-Lauritzen parameters and thermal transitions in PET/MMT nanocomposites

The differential isoconversional method of Friedman is applied to non-isothermal melt crystallization DSC data to obtain effective activation energy ΔE. In comparison to neat PET, ΔE of intercalated 93A MMT clay nanocomposites (PCNs) decreased and highly dependent on the clay content. Hoffman-Lauritzen (H–L) secondary nucleation theory parameters, Kg and U* were evaluated using isoconversional approach of Vyazovkin and Sbirrazzuoli. Crystallization regime transition from regime III is observed at 190°C for neat PET, which shifted to higher temperature range 200°C–208 °C for PCNs. The Kg parameters for both regimes for PET are consistent with our isothermal experiments and reported in literature. However, the Kg values of nanocomposites are highly sensitive to the temperature dependent nucleation activity and ΔE of PET chain motion in melt and are not very much comparable with our isothermal results. Nevertheless, the observed results clearly indicate that the 93AMMT clay layers predominantly act as heterogeneous nucleating sites.

Preparation and Infrared Emissivity Study of Optically Active Polyurethane/Multiwalled Carbon Nanotubes Nanocomposites

This paper described the preparation of optically active polyurethanes (BPUs)/multiwalled carbon nanotubes (MWCNTs) composites through the high-intensity ultrasound. SEM and TEM observations showed the homogeneous coating of MWCNTs by BPU. The infrared emissivity (8-14μm) study revealed that the composites possessed much lower infrared values compared with those of the polyurethanes and nanotubes, due to the special interface effect. The lowest infrared emissivity values of nanocomposites were S-BPU/MWCNTs εmin=0.461 and R-BPU/MWCNTs εmin=0.418, respectively.

New Synthesis and Magnetic Properties of NiFe2O4/SiO2 and Co0.5Zn0.5Fe2O4/SiO2 Nanocomposites Using Tetraglycolatosilane as Precursor

AbstractIn this work the new synthesis and magnetic properties of NiFe2O4/SiO2 and Co0.5Zn0.5Fe2O4/SiO2 nanocomposites using a water‐soluble silica precursor, tetraglycolatosilane (THEOS), by the sol‐gel method were reported. Nanocomposite were obtained by the thermal decomposition of the organic part at different annealing temperatures varying from 400 to 900 °C. Studies carried out using XRD, FT‐IR, TEM, STA (TG‐DTG‐DTA) and VSM techniques. XRD patterns show that NiFe2O4 and Co0.5Zn0.5Fe2O4 have been formed in an amorphous silica matrix at annealing temperatures above 600 and 400 °C, respectively. It is found that when the annealing temperature is up to 900 °C NiFe2O4/SiO2 and Co0.5Zn0.5Fe2O4/SiO2 samples show almost superparamagnetic behavior with a magnetization 4.66 emu/g and ferromagnetic behavior with a magnetization 10.11 emu/g, respectively. The magnetization and coercivity values of nanocomposites using THEOS were considerably less than previous reports using TEOS. THEOS as a silica matrix network provides an ideal nucleation environment to disperse ferrite nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS over the currently used TEOS and TMOS, organic solvents are not needed due to the entire solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of ferrites even more versatile.

An evaluation of nanocomposites as pit and fissure sealants in child patients

Dental caries affects populations of all ages in all the regions of the world, with the child patient being at the highest risk. Fifty percent of the permanent molars are decayed by the age of 12, due to lack of information about protection and occlusal morphology. Pit and fissure sealing undoubtedly plays a fundamental role in preventing occlusal caries. The most common approach to assess the sealing ability of pit and fissure sealants of tooth/restoration is the measurement of dye penetration along the interface. The present study aims to evaluate the microleakage and penetration depth of three different types of dental materials, namely (A) Conventional pit and fissure sealant, (B) Flowable composite, (C) Flowable nanocomposite. This in-vitro comparative study comprised of extracted human posterior teeth mounted as blocks. In the present study, microleakage and penetration depths of conventional sealants/flowable composite and nanocomposite were measured with the help of a dye under stereomicroscope. A student't' test and Analysis of variance (ANOVA) tests were performed to compare the mean microleakage and penetration depth. Microleakage was found to be highest for the flowable composites, and least for the conventional sealant. The nanocomposite values were intermediate. Penetration depth was highest for nanocomposite and least for flowable composite. According to the results, the nanocomposite was found to be an excellent dental material for penetration in deep pits and fissures, though it exhibits mild microleakage. Hence, it can be recommended for use in pediatric dental patients, as a pit and fissure sealing agent.

Study on the Effect of Nano and Active Particles of Alumina on Natural Rubber–Alumina Composites in the Presence of Epoxidized Natural Rubber as Compatibilizer

Natural rubber composites with alumina of different particle sizes (28 nm nano particles, 200 nm active particles and > 1000 nm raw alumina) were prepared by the usual rubber processing technique. Epoxidized natural rubber (ENR) was used in the composites as compatibilizer. Cure characteristics and mechanical properties of all composites were analyzed. The values of minimum rheometric torque (ML), maximum rheometric torque (MH) and torque difference (MH – ML) increased. Maximum enhancement was observed for the nano-filled composites. It endorses the view that nano alumina reveals highest interaction with natural rubber in presence of ENR. Scorch time and optimum cure time values for nano-composites were highest among all types of composites. Vulcanization reaction for the sulfur curing system of the composites was found to follow first order rate kinetics. Specific rate constant decreased with decreasing particle size in composites. Crosslink densities of composite-vulcanizates showed increasing trend with decreasing particle size of alumina. Mechanical properties of the composite vulcanizates increased with decreasing particle size of alumina - nano composites exhibiting much higher mechanical strength. Results of oxidative resistance reveal that particle size of alumina in composite vulcanizates has a significant impact on aging behavior.

Synthesis of PVP/IO-MMT Nanocomposite using Industrial Organic Montmorillonite

Industrial organic montmorillonite (IO-MMT) was characterized by X-ray diffraction (XRD) and thermogravimetry (TG). The results indicate that IO-MMT could prepare nanocomposite directly in theory. As dispersants, different nonionic surfactants were used to disperse IO-MMT. The result shows that nonionic surfactant TO-10 was selected as optimum dispersant. Then, vinyl polymer/industrial organic montmorillonite nanocomposite (PVP/IO-MMT) was prepared by vinyl polymer (PVP) and IO-MMT which dispersed in nonionic surfactant TO-10. The structure of PVP/IO-MMT nanocomposite was characterized by XRD and TEM. The result of XRD shows that the basal spacing d value of nanocomposite is 3.53 nm. The result of TEM indicates that composite was intercalated nanocomposite. Finally, PVP/IO-MMT was applied in the leather making process to examine its properties. The pickled sheepskin was tanned with 6% PVP/IO-MMT associated with 2% chromate, the shrinkage temperature of leather can be raised to 88°C. The application results show that it is an effective way to decrease the use of chromate for nanocomposites.