Oxide Nanopowders Research Articles

Cracking of Heavy Oil in Supercritical Water in the Presence of Iron Oxide Nanopowder: Asphaltene Transformations and Process Kinetics

Cracking of Heavy Oil in Supercritical Water in the Presence of Iron Oxide Nanopowder: Asphaltene Transformations and Process Kinetics

Effect of nanoparticle on mechanical properties of activated tungsten gas welding of austenite stainless steel 316L and optimization of process parameters

Abstract Austenite stainless steel 316L was developed to improve corrosion resistance and is widely used in automobile components, thermal power plants, and pressure vessels due to their superior toughness and intergranular corrosion resistance. The austenite stainless steel 316L has a low carbon content of 0.03%, which helps in minimizing harmful carbide precipitation during welding. The joint strength of welded joints is poor unless proper care is taken. As a result, an attempt was made to use an activated Tungsten Inert Gas (A-TIG) welding procedure to improve the joint strength of butt welded joints of austenitic stainless steel 316L. The process parameters such as current, the volume of flow, and filler diameter were chosen in the study and generated an L 9 design matrix using MINI Tab software. The welded joints were prepared as per the design matrix using the activated flux of aluminum oxide nano powder as per the combination of process parameters. The mechanical tests such as tensile strength, hardness, and impact strength were evaluated and microstructural evaluation of welded joints was also assessed. The input parameters were optimized for better tensile strength of joints using Taguchi S/N analysis. It is found from the optimization that the highest ultimate tensile strength of 690.40 MPa was obtained at a current of 90 A, shielding gas flow of 13 l min–1, and filler material diameter of 2.5 mm. The model was also validated by conducting experiments.

Phase transformation in air of Bi2O3 nanopowder produced by pulsed electron beam evaporation

The present paper studies the pathways of phase transformation of heterophasic nanopowder (NP) Bi2O3 produced by pulsed electron beam evaporation (PEBE) in vacuum (4 Pa) when annealing in air. The phase transformation after annealing in air of heterophase bismuth oxide NPs leads to the formation of bismuth carbonate at an annealing temperature of 200–300 °C. The effect of NP aging in storage under normal conditions was investigated.

Realization of improved magnetodielectric coupling and electrochemical performance of microwave assisted sol-gel prepared spinel manganese chromium oxide nanopowders

Microwave assisted sol-gel approach is used to successfully produce spinel phase of manganese chromium oxide nanoparticles. Hydrous manganese chloride, hydrous chromium chloride and ethylene glycol are used as precursors and solvent. Ratio of Mn/Cr (0.20–0.65) is varied during synthesis. Microwave radiations (720 W) are used to obtain nanopowders of manganese chromium oxide nanoparticles. Mn/Cr ratios of 0.20–0.25 produce amorphous behavior, while Mn/Cr ratios of 0.30, 0.35, 0.40, 0.45, and 0.65 produce mixed phases. Single phase of spinel MnCr2O4 nanoparticles is observed at Mn/Cr ratios of 0.50, 0.55, and 0.6. Normal dispersion behaviour with high value of dielectric constant (~60 at log f=5), low tangent loss (0.004 at log f =5) and low conductivity values are observed for Mn/Cr ratio of 0.6. Cole-Cole plots show a single semicircle, indicating that grain boundary resistance plays a significant role. The results of the vibrating sample magnetometer show that all the samples have ferromagnetic behavior, with a high saturation magnetization value (~ 15 emu/g) for Mn/Cr ratio of 0.6. Large and positive magnetodielectric response is observed for Mn/Cr ratio of 0.55 & 0.6. Cyclic voltammetry curves demonstrate high specific capacitance for Mn/Cr ratios of 0.55, and 0.6. Results obtained under as-synthesized conditions suggest suitability of the optimized material for magnetic and energy storage applications.

Toxic Effects of Nanographene Oxide on Testes of Rats

The current study aimed to examine the effects of nanographene oxide on the testes. A total of 48 male albino rats were randomly divided into 6 groups. The first, second, third, fourth, and sixth groups were treated with graphene oxide nanopowder at 20, 30, 40, 50, and 60 mg/kg concentrations, respectively. The sixth group was considered the control group. The results indicated a significant decrease in the average testis weight of rats treated with different nanographene oxide dosages, compared to the control group. There was also a significant decrease in the level of FSH and testosterone of treated rats with nanographene oxide, while there was no significant difference in the level of LH hormone when compared to the control group. The histological examination of the testes in the treated rats indicated hemorrhage, decreased sperm count, decreased thickness of the tubular epithelium, dissociation of connective tissue between the seminiferous tubules, in addition to hematological congestion, necrosis of the tubular epithelium, divergence of the seminal tubules, absence of sperm, shattering of the seminal tubule wall and degeneration sperm-forming cells and edema formation. Using the transmission electron microscope, the findings revealed a range of cellular changes, such as the presence of two-headed spermatids, the destruction of the nucleus membrane, spermatoblasts, the destruction of the cell membrane, and the denting of the nucleus membrane. It can be concluded that the nanographene oxide at 20-60 mg/kg concentrations can have harmful effects on spermatogenesis and normal function testis in rats.

Hydrothermal Synthesis of Nickel Oxide and Its Application in the Additive Manufacturing of Planar Nanostructures

The hydrothermal synthesis of nickel oxide in the presence of triethanolamine was studied. Furthermore, the relationship between the synthesis conditions, thermal behavior, crystal structure features, phase composition and microstructure of semi-products, and the target oxide nanopowders was established. The thermal behavior of the semi-products was studied using a simultaneous thermal analysis (in particular, using one that involved thermogravimetric analysis and differential scanning calorimetry, TGA/DSC). An X-ray diffraction (XRD) analysis revealed that varying the triethanolamine and nickel chloride concentration in the reaction system can govern the formation of α- and β-Ni(OH)2-based semi-products that contain Ni(HCO3)2 or Ni2(CO3)(OH)2 as additional components. The set of functional groups in the powders was determined using a Fourier-transform infrared (FTIR) spectroscopy analysis. Using microextrusion printing, a composite NiO-(CeO2)0.80(Sm2O3)0.20 anode film was fabricated. Using XRD, scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses, it was demonstrated that the crystal structure, dispersity, and microstructure character of the obtained material correspond to the initial nanopowders. Using Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM), the local electrophysical properties of the printed composite film were examined. The value of its conductivity was evaluated using the four-probe method on a direct current in the temperature range of 300-650 °C. The activation energy for the 500-650 °C region, which is of most interest in the context of intermediate-temperature SOFCs working temperatures, has been estimated.

Effect of dopant concentrations on structural and optical properties of iron doped tin oxide nano powder for optoelectronic device applications

Effect of dopant concentrations on structural and optical properties of iron doped tin oxide nano powder for optoelectronic device applications

Microplotter Printing of Hierarchically Organized NiCo2O4 Films for Ethanol Gas Sensing

Using a combination of chemical coprecipitation and hydrothermal treatment of the resulting dispersed system, a hierarchically organized NiCo2O4 nanopowder was obtained, consisting of slightly elongated initial oxide nanoparticles self-organized into nanosheets about 10 nm thick, which in turn are combined into hierarchical cellular agglomerates of about 2 μm. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HR-TEM) allowed to confirm the formation of NiCo2O4 powder with the desired crystal structure via additional heat treatment of the intermediate product. Energy-dispersive X-ray spectroscopy (EDX) was used to confirm the target metal ratio, and the uniform distribution of the elements (Ni, Co and O) was shown by mapping. The resulting nanopowder was employed to prepare functional inks suitable for microplotter printing of the NiCo2O4 film. It was found that an oxide film morphology is fully inherited from the hierarchically organized oxide nanopowder used. Atomic force microscopy (AFM) revealed the film thickness (15 μm) and determined the maximum height difference of 500 nm over an area of 25 μm2. Kelvin probe force microscopy (KPFM) showed that the surface potential was shifted to the depths of the oxide film, and the work function value of the material surface was 4.54 eV, which is significantly lower compared to those reported in the literature. The electronic state of the elements in the NiCo2O4 film under study was analyzed by X-ray photoelectron spectroscopy (XPS). Chemosensor measurements showed that the printed receptor layer exhibited selectivity and high signal reproducibility for ethanol detection. As the relative humidity increases from 0 to 75%, the response value is reduced; however, the sensor response profile and signal-to-noise ratio remain without significant changes.

Modification of Cotton and Leather Surfaces Using Cold Atmospheric Pressure Plasma and TiO2-SiO2-Reduced Graphene Oxide Nanopowders

Surface modification of textile fabrics and leathers is very versatile and allows the products quality improvement. In this work, cotton and leather substrates were pre-treated with cold atmospheric pressure plasma (CAPP) and further coated with TiO2-SiO2-reduced graphene oxide composites in dispersion form. By using a Taguchi scheme, this research evaluated the effect of three significant parameters, i.e., the pre-treatment with CAPP, organic dispersion coating and TiO2-SiO2-reduced graphene oxide (TS/GR) composites, that may affect the morpho-structural properties and photocatalytic activity of modified cotton and leather surfaces. The characteristics of cotton/leather surfaces were evaluated by morphological, structural, optical and self-cleaning ability using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray powder diffraction (XRD), attenuated total reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) and UV-Vis spectroscopy. The self-cleaning performance of the obtained cotton and leather samples was evaluated by photocatalytic discoloration of berry juice surface stains under UV light irradiation for 12 h. The successfulness of coating formulations was proven by the SEM analysis and UV-Vis spectroscopy. The XRD patterns and ATR-FTIR spectra revealed the cellulose and collagen structures as dominant components of cotton and leather substrates. The CAPP treatment did not damage the cotton and leather structures. The photocatalytic results highlighted the potential of TiO2-SiO2-reduced graphene oxide composites in organic dispersion media, as coating formulations, for further use in the fabrication of innovative self-cleaning photocatalytic cotton and leather products.

Optical, Dielectric and Structural Properties of SnO2 Nanoparticles Via Sol-Gel Method

This paper discuss the optical parameters of tin oxide nanopowder prepared by the sol-gel method. Tin oxide nanopowder shows 81 % transmittance in the near IR region. In this region, tin oxide nanopowder shows the highest reflectance, 81 %. The optical band gap was 3.43 eV. The cut-off wavelength of the tin oxide nanopowder is 362.15 nm. The refractive index and the extinction coefficient of the tin oxide nanopowder were calculated. The real and imaginary values of dielectric constants were calculated and the real value of the dielectric constant is higher than the imaginary value of dielectric constants. The average crystallite size from the XRD pattern was 15.93 nm. FESEM analysis shows that the average particle size was 17.21 nm.

Tailored Synthesis of Catalytically Active Cerium Oxide for N, N-Dimethylformamide Oxidation.

Cerium oxide nanopowder (CeOx) was prepared using the sol-gel method for the catalytic oxidation of N, N-dimethylformamide (DMF). The phase, specific surface area, morphology, ionic states, and redox properties of the obtained nanocatalyst were systematically characterized using XRD, BET, TEM, EDS, XPS, H2-TPR, and O2-TPO techniques. The results showed that the catalyst had a good crystal structure and spherelike morphology with the aggregation of uniform small grain size. The catalyst showed the presence of more adsorbed oxygen on the catalyst surface. XPS and H2-TPR have confirmed the reduction of Ce4+ species to Ce3+ species. O2-TPR proved the reoxidability of CeOx, playing a key role during DMF oxidation. The catalyst had a reaction rate of 1.44 mol g-1cat s-1 and apparent activation energy of 33.30 ± 3 kJ mol-1. The catalytic performance showed ~82 ± 2% DMF oxidation at 400 °C. This work's overall results demonstrated that reducing Ce4+ to Ce3+ and increasing the amount of adsorbed oxygen provided more suitable active sites for DMF oxidation. Additionally, the catalyst was thermally stable (~86%) after 100 h time-on-stream DMF conversion, which could be a potential catalyst for industrial applications.

Enhanced dielectric properties of Be-doped magnesium oxide nanopowder

Owing to its applicability in refractory ceramic synthesis, nanoelectronics, optoelectronic and sensing devices, and superconducting products, magnesium oxide (MgO) is recognized to be an important ceramic material. However, it has a relatively low dielectric constant compared to other metal oxide semiconductors, which restricts the range of its bandgap and limits its applicability. Therefore, in this study, we propose and verify a method to improve the dielectric constant of MgO. A sample of MgO powder doped with Be ions was prepared using the Pechini method. The crystal structure of the doped MgO powder was analyzed by x-ray diffraction. Through structural analysis, it was confirmed that a substitution amount of up to 5% of Be ions was possible without breaking the cubic structure. The bonding structure in the lattice of the sample was identified through x-ray photoelectron spectroscopy, and the change in the bonding structure according to the amount of substitution was identified. The dielectric properties of the samples were analyzed as a function of frequency at room temperature. The real and imaginary parts of the dielectric constant were studied at room temperature as a function of frequency and composition. It was confirmed that the dielectric constant increased as the Be ions were substituted. Our results show that improving the low dielectric properties of pure MgO can enable its application to wide bandgap and high voltage applications simultaneously.

Conditions for the open pores formation in medical textile materials for the treatment of wounds using iron oxide nanopowders

One of the tasks of dressings in the process of wound treatment is to remove exudate. In the optimal case, this intensity is determined individually for each wound. Active medical textiles take advantage of the capillary effect that occurs in thin channels. For these purposes, medical materials are created from porous structures. To create back pressure in foamed medical materials, the pores must be in the form of channels, which is not realized with conventional technologies. The purpose of this study is to analyze the performance of magnetic nanopowders on the pore structure in the production of porous materials. Research methods include methods of chemical synthesis, methods of microscopic analysis, methods of modeling, statistical analysis. The main result is the study of the formation of necessary forms in foamed materials during the use of magnetic nanopowders as additives. This effect makes it possible to increase the efficiency of foam structures when used as medical materials.

Study on the effect of zinc oxide nanopowder doped with different concentrations of cobalt, on the properties of implants

The aim of this study was to improve the physical, mechanical and chemical properties of biomaterials used in medical applications, by depositing thin films with superior properties on the surface of the materials. Starting from the antibacterial effect of ZnO nanopowders, doped or not with different concentrations of cobalt, five thermally treated thin films were deposited at 500°C, on a metallic titanium substrate, by the spin coating technique, a simple method that does not involves too many costs of depositing thin films on metal surfaces, starting from precursor liquids that gel over time. From the analysis of the resulting films, from a compositional, microstructural, morphological point of view, an increase in the antimicrobial activity of the materials used in impantology was found.

Исследование наноразмерного порошка оксида железа в качестве биологически активного материала

A polydisperse nanopowder of iron oxide, consisting of hematite α-Fe2O3 and magnetite Fe3O4, was obtained by the method of solid-phase reduction of iron hydroxide Fe(OH)3. On the basis of the obtained iron oxide nanopowder, aqueous suspensions were prepared in the concentration range of 0.25 – 1.25 mg/l with a particle dispersion of 100 – 400 nm. To assess the biological activity of iron oxide nanopowder, pre-sowing treatment of corn seeds Zéa máys was carried out. It has been established that the treatment with nanoparticles has a stimulating effect on the development of the plant organism, making it possible to achieve an increase in germination by 15% and root mass by 23%. Determination of the quantitative content of iron in different parts of the plant was carried out using atomic emission and atomic absorption spectroscopy. It was shown that as a result of treatment of plants with iron nanoparticles, its accumulation in the root mass with subsequent redistribution to the leaves to stimulate the process of photosynthesis is observed.

Ultrathin α-Bi2O3 Nanosheets Prepared via Hydrothermal Method for Electrochemical Supercapacitor Applications

Monoclinic bismuth oxide nanosheets (α-Bi2O3 NSs) of average thickness 28 nm were successfully synthesized via hydrothermal method. Various characterization techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Ramman spectroscopy, UV–vis spectroscopy, and Field Emission scanning electron microscopy (FE-SEM) coupled with Energy dispersive X-ray spectroscopy (EDXS) were employed to investigate the prepared bismuth oxide nanopowder in terms of its structural, morphological and optical properties. Electrochemical measurements of α-Bi2O3 NSs deposited on nickel foam substrate were carried out in a 6 M KOH electrolyte to examine its supercapacitive performance. The α-Bi2O3 NSs based electrode with 90 wt% active material exhibited excellent electrochemical performance with pronounced oxidation and reduction peaks, confirming the pseudocapacitive behavior with a high specific capacitance of 764.5 Fg−1 at 5 mVs−1 scan rate. The electrode also presented good cycling stability of about 69% capacitive retention after 3000 cycles measured at 10 mAcm−2 current density. This enhanced specific capacitance, excellent cycling stability and high specific energy (Es = 164.2 Whkg−1) rendered by the electrode which is attributed to widely open and ultrathin nanosheet like morphology, reveals that such a material is instrumental in energy storage applications.

Room temperature UV-Vis activated NO2 gas sensor-based Mg-doped zinc oxide nanopowders

Room temperature UV-Vis activated NO2 gas sensor-based Mg-doped zinc oxide nanopowders

A new electrolytic process for the synthesis of tungsten oxide nanopowder from WC-6Co scrap

An improved process was developed for the synthesis of hydrated tungsten oxide nanopowder from WC-6Co scrap at room temperature. This process is relatively less expensive and energy efficient. The conventional processes used for synthesizing tungsten oxide nanopowder are performed at high temperatures. In this study, tungsten oxide nanopowders are produced via electrolysis of WC-6Co pellet using sulfuric acid as an electrolyte; followed by dehydration at 150 °C. The dehydration treatment resulted in phase transformation. High purity nanorods and nanoplates of hydrated tungsten oxide were produced. The crystal size in the range of 9.6–13.8 nm was produced. The effect of process parameters on phase, crystal size, lattice strain, and morphology of tungsten oxide nanopowder is discussed.

Physiochemical characterization of sodium doped zinc oxide nano powder for antimicrobial applications

Zinc oxide (ZnO) is one of the semiconductor materials with unique antimicrobial properties towards various microorganisms. In this article, pure and Na doped ZnO nanopowders were synthesized by easiest and cost-effective co-precipitation process. X-ray diffraction (XRD),Fourier transform infrared spectroscopy(FT-IR), ultraviolet – visible (UV – Vis) spectroscopy, scanning electron microscopy(SEM), and Energy dispersive X-ray analysis (EDAX) techniques were used to characterize the particle size, surface morphology and chemical composition of prepared materials. The XRD analysis revealed that the samples exhibiting hexagonal wurtzite crystal structure with high crystallinity and the average crystallite size values increased from 23.51 to 28.118 nm. The UV – Vis spectroscopy results exposed that the bandgap energy (Eg) of the samples with the values in the range of 3.068–3.301 eV. The SEM micrographs showed that the morphology of the of synthesized particles are hexagonal and spherical in nanometric size. The EDX spectra confirmed the elemental composition of Na, Zn and O in the crystal lattice and FTIR spectroscopic data proved the formation of functional groups and the presence of chemical bonding at the ZnO interface.Antibacterial activity of pure and Na doped Zinc oxide nanoparticles against Gram-negative pathogenssuch as Escherichia coli, Pseudomonas aeruginosa & Klebsiella pneumoniae and Gram-positive pathogens such as Staphylococcus aureus reveal that the zone of inhibition increases with increasing Na concentration. The antifungal activity against Aspergillus and Candida was investigated.These results demonstrated that the pure and Na doped ZnO samples exhibit enhanced antibacterial and antifungal activity with increasing particle sizein presence of visible light and they could be used as good antibacterial as well as antifungal agents.

Assessment of Sago Wastewater Treatment Process in an Aerobic Bio-Reactor with the Support of Chemisorbent

The Performance of an Aerobic Bio-Reactor (ABR) for the behavior of synthetic sago processing wastewater was investigated. The system with 13.3 liters of working volume was accomplished by attached as well as suspended growth process. The experimental analysis was carried out with the influent Chemical Oxygen Demand of 3920 mg/l, 4360 mg/l and 4640 mg/l at Hydraulic Retention Times (HRT) of 11, 14, 17, 21, 28, 42, 84 and 141 hours. During the experiment, pH plays an important role and the Dissolved Oxygen was maintained within the permissible limit continuously. In an ABR, the maximum COD removal efficiency was attained 91.20% with an Organic Loading Rate (OLR) of 1.518 kg COD/m3. To achieve the goal of reusing the wastewater, again the treated effluent was analyzed by the technology of adsorption process using zinc oxide nano powder as a Chemisorbent and the maximum COD removal efficiency of 100% was observed with 0.75 g of dosage content at the pH of 6 at the contact time of 180 minutes.