Ag/αFe2O3-rGO novel ternary nanocomposites: Synthesis,characterization, and photocatalytic activity

In this research, novel ternary Ag/αFe₂O₃-rGO nanocomposites with various contents of GO were synthesized via a facile one-pot hydrothermal method. Ag/αFe₂O₃-rGO nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDX), photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR). The results showed that hematite nanoparticles and Ag nanoparticles were well decorated on the graphene surface. Photocatalytic activity of Ag/αFe₂O₃-rGO ternary nanocomposites and pure Ag/αFe₂O₃ was investigated for photodegradation of Congo red dye solution as a model pollutant under UV light irradiation. The ternary nanocomposite with 1.8?mg/ml GO aqueous solution concentration shows higher degradation efficiency under UV light irradiation than the pure Ag/αFe₂O₃ and the nanocomposites with other GO aqueous solution concentrations. It was observed that the adsorption of the dyes on the nanocomposites surface is dependent on the graphene content due to a decrease in the recombination rate, particles size, and increase charge carrier transfer. The results show that the Ag/αFe₂O₃-rGO nanocomposite can be used as an excellent photocatalytic material for degradation of Congo red dye in wastewater. A possible photocatalytic mechanism was proposed for degradation of Congo red dye.     

Preparation of CdS/TiO2 nanotube arrays and the enhanced photocatalytic property

In this paper, a series of CdS/TiO₂ NTs have been synthesized by SILAR method. The as-prepared CdS/TiO₂ NTs have been analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), and ultraviolet–visible (UV–vis). And their photocatalytic activities have been investigated on the degradation of methylene blue under simulated solar light irradiation. XRD results indicate that TiO₂ NTs were anatase phase, CdS nanoparticles were hexagonal phase. FESEM results indicate that low deposition concentration can keep the nanotubular structures. UV–vis results indicate that CdS can be used to improve the absorbing capability of TiO₂ NTs for visible light, and the content of CdS affects the band gap. Photocatalytic results indicate that CdS nanoparticles are conducive to improve the photocatalytic efficiency of TiO₂ NTs, and the highest degradation rate can reach 93.8%. And the photocatalytic mechanism of CdS/TiO₂ NTs to methylene blue is also described.     

Facile Preparation of LaFeO<Subscript>3</Subscript>/rGO Nanocomposites with Enhanced Visible Light Photocatalytic Activity

The present work demonstrates a facile route for preparing LaFeO₃/rGO nanocomposites comprising of metal oxide nanoparticles and graphene. Structural, morphology, optical and photocatalytic studies of the samples were characterized using powder X-ray diffraction (XRD), FT-IR, Raman, high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscope (HRTEM), atomic force microscopy (AFM), thermogravimetry (TGA), X-ray photoelectron spectroscopy, UV–visible and photocatalytic. LaFeO₃/rGO nanocomposites believed as an effective photocatalyst for the degradation of methyl orange (MO) dye under visible light irradiation. The inclusion of carbon enhances the light absorption of LaFeO₃, resulting in the enhanced photocatalytic activity of the nanocomposite. The degradation of MO dye under visible light source was completely achieved using LaFeO₃/rGO as a catalyst.     

Photocatalytic degradation of Brilliant Red M5B using four different nanocomposites (ZnFe2O4, porous ZnFe2O4, ZnFe2O4–TiO2, FeTiO3) coated on glass

This paper presents the preparation, characterization, and application of four different nanocomposites in photocatalytic degradation of the Brilliant Red M5B as a dye contaminant. Nanocomposites include ZnFe₂O₄, porous ZnFe₂O₄, ZnFe₂O₄–TiO₂, and FeTiO₃ prepared and coated on a glass slide by doctor blade method. Different techniques to characterize composites are X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance spectra (DRS). FESEM shows that nanocomposites are nanocrystallines and a narrow dispersion in size. XRD confirms that the prepared nanocomposites are composed of ZnFe₂O₄, FeTiO₃ and TiO₂. Degradation efficiency of composites is evaluated using Brilliant Red M5B as a model pollutant under UV irradiation with homemade photocatalytic apparatus. The results showed that the photocatalytic efficiency of ZnFe₂O₄–TiO₂ is higher than that of other photocatalyst, which is mainly ascribed to ZnFe₂O₄ NPs with the spinel structure.     

Development of photo-anodes based on strontium doped zinc oxide-reduced graphene oxide nanocomposites for improving performance of dye-sensitized solar cells

The goal of this study was to create highly efficient dye-sensitized solar cells (DSSCs) using strontium doped zinc oxide-reduced graphene oxide (Sr-doped ZnO/rGO) nanocomposites. As photo-anodes of DSSCs, ZnO, ZnO/rGO (with weight percent rGO in composites: 0, 0.01, 0.1, 0.5, and 1 wt%) and Sr-doped ZnO/rGO (with Zn_1-xSr_xO nanoparticle stoichiometry: x = 0, 0.02, 0.04, 0.06 and 0.08) nanocomposites were designed and characterized. AFM, FESEM, XRD, EDS, XPS, PL, and FTIR analyses were used to investigate the morphology and structure properties of prepared nanocomposites. UV–vis spectroscopy and photo-electrochemical measurements were used to investigate the efficiency of prepared photo-anodes. The efficiency (η) and short-circuit photocurrent density (JSC) of DSSCs based on Zn_0.92Sr_0.08O/rGO nanocomposite were 7.98 % and 18.4 mA cm⁻², respectively. The results showed that doping Sr on ZnO/rGO nanocomposites resulted in a wide bandgap energy and increased the values of η, J_SC, IPCE, and photo-anode electron transportability. These findings suggest that Sr-doped ZnO/rGO nanocomposites can provide a novel approach for increasing photo-electrochemical activity in ZnO-based DSSCs.     

Nanostructure composite ZnFe2O4–FeFe2O4–ZnO immobilized on glass: Photocatalytic activity for degradation of an azo textile dye F3B

An efficient and scalable one-pot synthetic method to prepare nanostructure composite of ZnFe₂O₄–FeFe₂O₄–ZnO (ZFZ) has been investigated. This method is based on thermal decomposition of iron(III) acetate and zinc acetate in monoethanolamine (MEA) as a capping agent. Moreover, thermogravimetric analysis (TG-DTG) was performed to determine the temperature at which the decomposition and oxidation of the chelating agents took place. ZFZ was immobilized on glass using doctor blade method and calcinated at different temperatures. The properties of the ZFZ nanocomposite have been examined by different techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance (DRS). FESEM shows that nanocomposite is monocrystallines and a narrow dispersion in size of 48 nm. XRD confirms that the prepared nanocomposite is composed of franklinite, ZnFe₂O₄ (54%), magnetite, FeFe₂O₄ (8%) and wurtzite, ZnO (48%). Photocatalytic activity of ZFZ immobilized on glass was carried out by choosing an azo textile dye, Reactive Red 195 (F3B) as a model pollutant under UV irradiation with homemade photocatalytic apparatus and the results indicated that ZFZ exhibited good photocatalytic activity.     

An Amalgam of Mg-Doped TiO2 Nanoparticles Prepared by Sol–Gel Method for Effective Antimicrobial and Photocatalytic Activity

In this study, undoped and Magnesium doped TiO₂ nanoparticles (Mg-TiO₂ NPs) are successfully synthesized via a simple sol–gel method cost-effectively. The prepared Mg- TiO₂ NPs is characterized by UV–Vis, FTIR, PL, XRD, FESEM, TEM, and EDAX. UV–Visible Spectroscopy showed that an increase in the optical bandgap concerning the concentration of dopant Mg increases. The bandgap values were found to be 3.57–3.54 eV. FTIR spectra shows that the presence of the characteristic stretching and bending vibrational band of Ti–O bonding at 468 cm^?1 and shifts in vibrational bands were observed for Mg-TiO₂ NPs. PL spectra of Mg- TiO₂ NPs at different concentrations exhibit a strong UV emission band. X-ray diffraction confirmed the formation of the tetragonal anatase phase. The average crystallite size of synthesized samples was found to be 22–19 nm. The average crystallite size of Mg- TiO₂ NPs decreases with increasing the concentration of dopant Mg. The FESEM and TEM analysis confirmed that the spherical morphology for both TiO₂ and Mg-TiO₂ NPs. SAED pattern confirms the crystalline nature of prepared samples. EDAX spectra confirm the presence of Ti, O, and Mg and confirm that Mg²⁺ ions are present in the TiO₂ lattices. The prepared samples were investigated against gram-positive and gram-negative bacteria. The prepared samples exhibit potent antibacterial activity against gram-negative bacteria than the gram-positive bacteria. The prepared samples exhibit significant photocatalytic degradation for Methylene blue (MB).

     

TIO2/Nanoclay nanocomposite for phenol degradation in sonophotocatalytic reactor

A TiO₂–nanoclay nanocomposite was used as a photocatalyst for the degradation of phenol in presence of acoustic cavitation. TiO₂–nanoclay nanocomposite was synthesised in benzyl alcohol medium wherein TiO₂ nanoparticles were formed between the nanoclay platelets. The synthesised product was characterised by using FTIR, XRD and TEM techniques. TEM image shows that TiO₂–nanoclay nanocomposite particles were in the range of 30–40 nm. XRD gram confirms the formation of nanocomposite of TiO₂ nanoclay. The effect of cavitation and TiO₂–nanoclay nanocomposite photocatalyst on phenol removal was investigated. The effects of various parameters such as nanocomposite loading, initial concentration, etc., have been studied. On comparing the results obtained with that of nanocomposite without UV, it was found for an initial concentration of 500 mg/L of phenol, the TiO₂–nanoclay nanocomposite exhibited higher percentage of pollutant removal (59%) and for nanoclay it was 47%. © 2011 Canadian Society for Chemical Engineering     

Synthesis of carbon quantum dots/TiO2 nanocomposite for photo-degradation of Rhodamine B and cefradine

Pure TiO₂ and carbon quantum dots (CQDs)-doped TiO₂ nanocomposite (CQDs/TiO₂ nanocomposite) were prepared by a sol-gel approach for photocatalytic removal of Rhodamine B and cefradine. Analyses by Transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), UV–visible spectroscopy and X-ray powder diffraction (XRD) confirmed the successful formation of CQDs/TiO₂ heterostructure. The as-prepared TiO₂ and CQDs/TiO₂ composite possessed small particles, spherical-like shape, and anatase crystal form. Meanwhile, Rhodamine B and cefradine were chosen to evaluate the photocatalytic activity of TiO₂ and CQDs/TiO₂ composite. Results revealed that with the facile decoration of CQDs, the absorption of photocatalyst was extended into visible light region and photocatalytic activity was improved in comparison with pure TiO₂. Furthermore, the mechanism for the improvement of the photocatalytic performance of the composites was discussed on the basis of the results. CQDs play an important role in the photocatalytic process, due to their superior ability to extend the visible absorption and produce more electrons and electron–hole pairs for the degradation of pollutants. In all, the paper offers further insights into the development of CQDs/TiO₂ nanocomposite as photocatalyst for the degradation of antibiotics.     

One-pot synthesis of CdS sensitized TiO2 decorated reduced graphene oxide nanosheets for the hydrolysis of ammonia-borane and the effective removal of organic pollutant from water

A hybrid material of reduced graphene oxide (RGO) sheets decorated with CdS-TiO₂ NPs was prepared through a facile one-pot hydrothermal method. The assembly of CdS-TiO₂ nanoparticles (NPs) on RGO sheets was in-situ produced. As-synthesized nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy disperse X-ray spectrum (EDS), fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). The obtained nanocomposites exhibited a good photocatalytic activity for the visible-light-induced decomposition of methylene blue (MB) dye and hydrolysis of ammonia borane. The results showed that by incorporation of CdS and TiO₂ NPs on graphene oxide sheets the photocatalytic efficiency was enhanced. The significant enhancement in the photocatalytic activity of CdS-TiO₂/RGO nanocomposites under visible light irradiation can be ascribed to the effect of CdS by acting as electron traps in TiO₂ band gap. Reduced graphene oxide worked as the adsorbent, electron acceptor and a photo-sensitizer to efficiently enhance the dye photo decomposition. Such nanocomposite photocatalyst might find potential application in a wide range of fields, including hydrogen energy generation, air purification, and wastewater treatment.     

Sol-gel synthesis,spark plasma sintering,structural characterization,and thermal conductivity measurement of heavily Nb-doped SrTiO3/TiO2 nanocomposites

Heavily Nb-doped strontium titanate (SrTi_1-xNb_xO₃) nanoparticles and SrTi_1-xNb_xO₃/TiO₂ nanocomposite powders were synthesized by a sol-gel method. Structural characterization of the obtained powders was performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. The powders were densified by spark plasma sintering (SPS) method up to 98% of the relative density. Upon composite production, the thermal conductivity of the un-doped samples was effectively decreased for SrTiO₃/TiO₂ nanocpmposite from 12 to 8 W/m.K. On the other hand, thermal conductivity of the Nb-doped SrTi_0.8Nb_0.2O₃/TiO₂ composite was decreased by about 50% down to 3.4 W/m.K in comparison to SrTiO₃/TiO₂ due to the phonon scattering at the point defects originated from both Nb atoms and TiO₂ nanoparticles.     

A novel approach for the synthesis of highly active ZnO/TiO2/Ag2O nanocomposite and its photocatalytic applications

The present work is focused on the preparation of hybrid ZnO/TiO₂/Ag₂O nanocomposite for enhanced photocatalytic activity. The resultant samples are characterized by using XRD, SEM, EDX, HR-TEM, UV-DRS, BET and XPS techniques. X-ray diffraction analysis indicates the co-existence of wurtzite, anatase and cubic phases in ZnO/TiO₂/Ag₂O nanocomposite. The band gap energy value of the photocatalyst is 3.39 eV, which has been evidenced from UV–visible diffuse reflectance spectroscopy measurements. Photocatalytic degradation of methylene blue dye has been investigated by using UV–visible spectrophotometer. From the result, it has been concluded that ZnO/TiO₂/Ag₂O nanocomposite has proven to be an efficient photocatalyst under UV irradiation when compared to that of mono and binary oxide systems. Further, the possible photodegradation mechanism is proposed to support the enhancement of photocatalytic activity towards degradation of dyes.     

Room temperature in situ chemical synthesis of Fe3O4/graphene

A simple, cost-effective, efficient, and green approach to synthesize iron oxide/graphene (Fe₃O₄/rGO) nanocomposite using in situ deposition of Fe₃O₄ nanoparticles on reduced graphene oxide (rGO) sheets is reported. In the redox reaction, the oxidation state of iron(II) is increased to iron(III) while the graphene oxide (GO) is reduced to rGO. The GO peak is not observed in the X-ray diffraction (XRD) pattern of the nanocomposite, thus providing evidence for the reduction of the GO. The XRD spectra do have peaks that can be attributed to cubic Fe₃O_4. The field emission scanning electron microscopy (FESEM) images show Fe₃O₄ nanoparticles uniformly decorating rGO sheets. At a low concentration of Fe²⁺, there is a significant increase in the intensity of the FESEM images of the resulting rGO sheets. Elemental mapping using energy dispersive X-ray (EDX) analysis shows that these areas have a significant Fe concentration, but no morphological structure could be identified in the image. When the concentration of Fe²⁺ is increased, the Fe₃O₄ nanoparticles are formed on the rGO sheets. Separation of the Fe₃O₄/rGO nanocomposite from the solution could be achieved by applying an external magnetic field, thus demonstrating the magnetic properties of the nanocomposite. The Fe₃O₄ particle size, magnetic properties, and dispersibility of the nanocomposite could be altered by adjusting the weight ratio of GO to Fe²⁺ in the starting material.     

Ternary Ag@SrTiO3@CNT plasmonic nanocomposites for the efficient photodegradation of organic dyes under the visible light irradiation

In this research, carbon nanotube (CNT)-modified plasmonic silver-strontium titanate (Ag@ SrTiO₃) nanocomposites for the degradation of the organic dye were prepared by the sol-gel method. The characterization of all products was carried out using the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption test (BET), field emission-scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), and transient photocurrent (TPC) studies. It was found that the incorporation of Ag in and introducing CNT into the SrTiO₃ nanoparticles reduced the crystallite size to 21 nm and the band gap energy to 2.7 eV. The Reduced PL peak intensity, increased photocurrent value, and reduced charge transfer resistance approved that the Ag@SrTiO₃@CNT nanocomposite had a greater charge transfer efficiency than other samples. The optimal dosage of the photocatalyst, for the complete degradation of 5 ppm of the methylene blue (MB) solution after 30 min of the visible light irradiation, was decided as 0.5 g/L. Besides, in the experimental environment, the Ag@SrTiO₃@CNT sample illustrated the most significant photocatalytic performance of the degradation of methyl orange (MO) and Rhodamine B (RhB) dyes. The detailed mechanism and kinetics of the degradation procedure were clarified. Finally, the prepared system displayed increased stability and reusability in the entire cyclic degradation experiment.     

Synthesis,characterization and optical properties of Zr+4/La+3/Nd+3 tri-doped yttria nanopowder by sol–gel combustion method

In this research, zirconium lanthanum and neodymium tri-doped yttria nanopowder was synthesized using the sol–gel combustion method. Citric acid (CA) and glycine (G) were used for the gel and fuel agent, respectively. The effect of CA:G:TM (TM=transition metal) mole ratios on the particle size and morphology of the product was evaluated. As-synthesized samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), energy dispersion spectrum (EDS), photoluminescence (PL) spectrum, Inductively coupled plasma (ICP), UV–visible (UV–vis spectroscopy), thermal gravimetric-differential thermal analysis (TG/DTA) and Fourier transform infrared (FTIR)analysis. The optimized sample synthesized with CA:G:TM mole ratio of (1.06:1.06:1) had the average particle size of 30–40 nm with a spherical morphology. Moreover, the optimized sample showed visible photoluminescence, at 400–800 nm.     

Mg3Y2Ge3O12:Bi3+ UV fluorescent phosphor as the TiO2 “sensitizer” for enhancing the heavy oil viscosity reduction

Nowadays, visible fluorescent materials based on rare earth (RE) and non-RE ions doping have been extensively explored for white LEDs. As for the UV fluorescent materials, it is well known that they are not suitable for the lighting applications. As a result, when compared to the visible fluorescent materials, previous works paid little attention to the UV fluorescent materials. In this work, we report a type of Mg₃Y₂Ge₃O₁₂:Bi³⁺ UV fluorescent phosphor. To understand the crystal structural information and photoluminescence (PL) properties of samples, we have used the X-ray diffraction (XRD), scanning electronic microscope (SEM), UV–visible diffuse reflectance and PL spectra to characterize them. The structural results reveal that the Bi³⁺ doped sample show their particle size at about 30 μm. The PL results show that the Bi³⁺ doped sample upon excitation at 230 nm can show a broad emission band that can almost cover the whole UV spectral region from 290 nm to 410 nm. Since this UV fluorescent band is exactly in agreement with the UV absorption region of TiO₂ semiconductor, we have fabricated several Mg₃Y₂Ge₃O₁₂:Bi³⁺/TiO₂-based ceramic plates and proposed used them to serve as an efficient UV irradiation source for photocatalytic application. As a result, we find that the TiO₂ can exhibit the significantly enhanced photocatalytic property for the heavy oil viscosity reduction after adding the Mg₃Y₂Ge₃O₁₂:Bi³⁺ UV fluorescent phosphor.     

A combined experimental and theoretical optimization of the refractive index of NixMg1-xO solid solution for transparent nanocomposite applications

The main objective of this work is to optimize the refractive index of MgO/NiO solid solution to increase the transparency of Y₂O₃–MgO (Y: M) nanocomposite in the visible region. First, various effective medium approximation theories (EMA) are applied to calculate the refractive index of Ni_xMg_1-xO solid solution as a function of NiO fraction and then determine those fractions giving the lowest refractive index mismatch with Y₂O₃ in the visible region. Thereafter, the theoretically predicted optimized solid solutions were experimentally synthesized by the sol-gel combustion method and the effect of NiO fraction on the morphology, structural properties, and band gap of the samples were investigated by the field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), Fourier transform infrared (FTIR), and diffuse reflectance spectroscopy (DRS). We argued that increasing the NiO fraction will decrease the band gap of Ni_xMg_1-xO samples from 5.83 to 5.67 eV. Finally, we applied four phenomenological models to predict the static refractive index of the samples from their measured band gaps and concluded that NiO fraction of 28.5% likely minimizes the light scattering and consequently maximizes the transparency of the Ni_0.285Mg_0.715O–Y₂O₃ nanocomposite in the visible region.     

Nanocrystalline transition metal oxides and their composites with reduced graphene oxide and carbon nanotubes for photocatalytic applications

Transition metal oxide nanoparticles (CuO, ZnO & Fe₂O₃) and mixed metal oxides CuO. ZnO.Fe₂O₃ were fabricated by facile co-precipitation approach for photocatalytic treatment of organic dyes. The structural features, phase purity, crystallite size and morphology of individual and mixed metal oxides were analysed by X-rays diffraction patterns (XRD) and scanning electron microscopic (SEM) analysis. Electrical behaviour of CuO, ZnO, Fe₂O₃ and mixed metal oxides CuO. ZnO.Fe₂O₃ was explored by current-voltage (I-V) measurements. Functional groups present in the synthesized metal oxides were investigated by Fourier transform infrared spectroscopy (FTIR) which ensures the existence of M-O functional groups in the samples. The optical bandgap analysis was carried out by UV–visible spectroscopic technique which revealed that the blend of three different transition metal oxides reduced the bandgap energy of mixed metal oxides. The reason behind this reduced bandgap energy is formation of new electronic state which arises due to the metal-oxygen interactions. Moreover, the nanocomposites of CuO.ZnO.Fe₂O₃ with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) were prepared to study the effect of the carbonaceous materials on the rate of photodegradation. These carbonaceous nanomaterials have plethora properties which can bring advancement in sector of photocatalytic treatment of wastewater. The photocatalytic experiments were performed using methylene blue (MB) as standard dye for comparative study of metal oxides and their composites with rGO and CNTs. The percentage degradation of methylene blue (MB) by nanocomposite CuO.ZnO.Fe₂O₃/rGO is 87% which is prominent among all samples. This result ascribed the photocatalytic aspects of reduced graphene oxide along with mixed metal oxides.     

UV-assisted sonochemical synthesis and optoelectrical properties of Bi2S3/rGO nanocomposites

In the present study, a simple UV-assisted sonication method is used for the development of bismuth sulfide (Bi₂S₃) nanostructures on graphene sheets. X-ray diffraction (XRD) and Raman results indicated that graphene oxide (GO) layers are reduced. Field emission scanning electron microscopy (FESEM) images also indicated that Bi₂S₃ particles without rGO sheets are agglomerated. In comparison, when adding these sheets, the particles are uniformly spread (decorated) and their size is reduced significantly due to the incorporation of rGO sheets. UV–Vis studies reveal that the band gap in Bi₂S₃/rGO nanocomposites compared with Bi₂S₃ has a shift toward shorter wavelengths, suggesting some changes in the electronic band structure of Bi₂S₃ due to the existence of rGO sheets. Photoluminescence (PL) analysis indicated emission bands in infrared and visible regions resulting from the band edge emission and crystal defects in the samples, respectively. The electrical investigations showed reduced recombination of photogenerated carriers in the nanocomposites. Moreover, the results indicated that the concentration of rGO is an important factor in determining the optoelectrical behavior of these devices.     

Toughening of MgAl2O4 spinel/ Si3N4 nanocomposite fabricated by spark plasma sintering

The main objective of this work is to compare the hardness, fracture toughness, and optical transparency of MgAl₂O₄ spinel (magnesium aluminate), MgAl₂O₄ spinel/ Si₃N₄ nanocomposite, and the heat-treated spinel/Si₃N₄ nanocomposite. For this purpose, the commercial spinel nanopowder and the laboratory-made spinel/ Si₃N₄ nanocomposite powder were sintered using spark plasma sintering (SPS). A heat treatment at 1000?°C for 4?h was carried out on the as-sintered nanocomposite. The field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Nanoindentation, and Vickers microhardness analyses were used to determine microstructure, elemental analysis, functional group, hardness, and indentation toughness of the samples. The results showed that the hardness and toughness of the heat-treated sample are more than those of the as-SPSed nanocomposite as much as 15.7% and 25.7%, respectively. Also, the values of optical transmission of the nanocomposite sample in the visible range (400–800?nm) and infrared region (800–2000?nm) were lower than those of pure spinel.