Effect Of Synthesis Time Research Articles

Effect of synthesis time on the photocatalytic performance of aggregated CuBO₂ microstructures for photo induced hazardous dye removal

Effect of synthesis time on the photocatalytic performance of aggregated CuBO₂ microstructures for photo induced hazardous dye removal

Effects of synthesis time on the optical–electrical and structural properties of silicon carbide/graphite core–shell structures for supercapacitor applications

Effects of synthesis time on the optical–electrical and structural properties of silicon carbide/graphite core–shell structures for supercapacitor applications

The non-crystalline metal-organic framework for corrosion inhibitor behavior in sodium chloride solution

The metal-organic frameworks (MOFs), namely ZIF-62, have the ligand of imidazole and benzimidazole, which are effective corrosion inhibitors. In this context, ZIF-62 is an ideal candidate in marine corrosion protection. However, it is not reported till present. Here, the non-crystalline ZIF-62 ( g -ZIF-62), a novel corrosion inhibitor carrier, is developed by melting the ZIF-62 crystal ( c -ZIF-62) and its corrosion inhibition performance on AZ91 Mg alloy is investigated by electrochemical measurement. The results show that ZIF-62 could effectively inhibit the Mg alloy from corrosion. More significantly, g -ZIF-62 shows a better corrosion inhibition effect, and the corrosion inhibition efficiency ( η ) is up to 83.6%. The glassy grain boundaries of g -ZIF-62 disappear when melting the c -ZIF-62, which hinders the invasion of corrosive media, e.g. H 2 O molecules, Na + and Cl − , to improve the stability in seawater. More importantly, the molar ratio of imidazole to benzimidazole is adjusted by the reaction time ( T m ). Given the significant steric hindrance, the much content of benzimidazole in g -ZIF-62(48 h) have high viscosity under T m , leading to the formation of a pyknotic glass for the corrosion inhibitors. Thus, this study not only highlights the potential of ZIF-62 as a corrosion inhibitor, but also provides fresh insights for the application of non-crystalline MOF in harsh seawater corrosion. • Corrosion inhibitor for metal–organic frameworks is reported. • The stability of MOFs in sodium chloride solution was improved by amorphous method. • The effect of synthesis time and corrosion mechanism were investigated. • ZIF-62 is used for the first time as corrosion inhibitor on the surface of AZ91 Mg alloy.

Synthesis and performance of STT zeolite membranes for He/N2 and He/CH4 separation

Helium (He) extraction from natural gas is energy extensive because of the extremely low He fraction and operating temperature. Membrane gas separation is highly desired because of the atmospheric temperature operation. Herein all-silica STT zeolite membranes were prepared on four-channel hollow fibers for He/N2 and He/CH4 separation. The effect of synthesis time (1–4 days) on the membrane texture and separation performance was investigated. Initially both 7MR and 9MR channels served as the transport pathway, however, 7MR channels became the dominated one once the synthesis period beyond 2 days at synthesis temperature of 453 K. The size-exclusion effect of He over N2 and CH4 was much stronger than the current 8MR zeolite membranes. Therefore, the He/N2 selectivity was up to 25.4 and the He/CH4 selectivity was 87.6. The He concentration could be enhanced by 15 ∼ 18 times towards the simulated stream containing 0.2 % He at 0.7 MPa. Most importantly, the membrane performance was stable in the practical feed containing 1 mol% ethane for up to 450 h.

Effect of synthesis time on plasmonic properties of Ag dendritic nanoforests.

The effects of synthesis time on the plasmonic properties of Ag dendritic nanoforests on Si substrate (Ag-DNF/Si) samples synthesized through the fluoride-assisted galvanic replacement reaction were investigated. The Ag-DNF/Si samples were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, reflection spectroscopy, X-ray diffraction and surface-enhanced Raman spectroscopy (SERS). The prolonged reaction time led to the growth of an Ag-DNF layer and etched Si hole array. SEM images and variations in the fractal dimension index indicated that complex-structure, feather-like leaves became coral-like branches between 30 and 60 min of synthesis. The morphological variation during the growth of the Ag DNFs resulted in different optical responses to light illumination, especially those of light harvest and energy transformation. The sample achieved the most desirable light-to-heat conversion efficiency and SERS response with a 30 min growth time. A longer synthesis time or thicker Ag-DNF layer on the Si substrate did not have superior plasmonic properties.

Effect of Synthesis Time on Synthesis and Photoluminescence Properties of ZnO Nanorods

With the hydrothermal method, the p-type silicon <100> wafer was used as the substrate to synthesize ZnO nanorods in different synthesis times. To prepare the ZnO seed layer on the p-type silicon <100> wafer, a prepared ZnO gel was deposited as the seed layer using the spin coating method. A 0.2 M solution of zinc acetate dihydrate (Zn(CH3COO)2-2H2O) and hexamethylenetetramine ((CH2)6N4) were used as the source materials at a synthesis temperature of 90 °C. The synthesis time was changed from 10 to 60 min as the synthesis parameter. X-ray diffraction patterns, scanning electron microscopy, and a focused ion beam system were used to analyze and compare the crystal characteristics and the heights and widths of synthesized ZnO nanorods. We found that the crystal characteristics, the heights and widths, and the photoluminescence properties of synthesized ZnO nanorods were dependent on the synthesis time.

Tuning parameters for the synthesis of MIL-53(Al): Mn doped MIL-53(Al) as a high potential catalyst for methanol dehydration

Abstract Recently, many studies are dealing with developments of Metal-Organic Frameworks (MOFs), especially MIL-53(Al), which shows high thermal and mechanical stability. Among these, optimizing the synthesis condition of MIL-53(Al) to obtain appropriate characteristics has attracted much attention in academia and the industry. Here, the effect of synthesis time and ligand to metal molar ratio on the hydrothermal synthesis of MIL-53(Al) are pursued. The synthesized MIL-53(Al) samples are characterized by X-ray diffraction (XRD), the Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), thermal gravimetric analysis (TGA), and nitrogen adsorption-desorption technique (BET). The present study shows that MIL-53(Al) can be conventionally synthesized with a high yield within a shorter reaction time than the previous studies. Furthermore, the catalytic activity of the optimized MIL-53(Al) in the pure and Mn-doped form is studied in a methanol dehydration reaction. It is thus inferred that this popular MOF in the Mn/MIL-53(Al) form has a high activity and DME selectivity during methanol conversion. Our present results confirm the merits of employing the MIL-53(Al) as a catalyst in methanol to DME conversion, which can be an avenue for the practical application of acidic catalyst.

Mechanochemical synthesis of SrFe12O19 from recycled mill scale: Effect of synthesis time on phase formation and magnetic properties

In the present study, the strontium hexaferrite (SrFe12O19) has been successfully produced from recycled mill scale and strontium carbonate (SrCO3) powders with stoichiometric ratio (SrCO3/Fe2O3) of 1:6 by mechanochemical synthesis process, followed by annealing at 975 °C temperature. As the mechanochemical synthesis time increased, the phase ratio of hard magnetically SrFe12O19 in the structure increased after the annealing, according to the XRD analysis. The SrFe12O19 phase formation temperature decreased from 851 °C to 762 °C with increasing mechanochemical synthesis time. Also, FTIR analysis showed that The C═O bond peaks are only visible for a 2 h synthesis time at 854 cm−1 wavenumbers. Magnetic properties have changed according to particle size, activation energy, and phase ratios. The best magnetic properties were obtained with the application of 16 h of synthesis time. The coercivity values of 3.3, 3.6, 4.6, 5.5, 5,4, and 3.7 kOe were obtained for 2, 4, 8, 16, 32, and 64 h of mechanochemical synthesis times, respectively. The residual magnetization density (Br) values under 1 T magnetic field for the same synthesis times were obtained as 168, 221, 292, 347, 314, 258 mT, respectively.

A fundamental exploration on carbon nanotube formation via pyrolysis of ferrocene and glycerol: Experimental and theoretical viewpoints

To gain insights into formation of carbon nanotubes (CNTs) via pyrolysis of ferrocene and glycerol, experimental analyses on chemical constituents and theoretical investigation using a fundamental mathematical model based on thermodynamics and kinetics were conducted. A systematic calculating algorithm was verified based on comprehensive data sets of previous experimental works. Effects of synthesis time, initial concentration of ferrocene and glycerol as well as temperature on the CNT formation were analyzed. The proposed model reveals that with temperature above 700 K, the formation rate of CNTs rises rapidly. However, the CNT formation rate starts to decrease slightly when the temperature exceeds 1000 K due to the competitive step of their reversible decomposition.

Tuning the morphology and magnetic properties of single-domain SrFe8Al4O19 particles prepared by a citrate auto-combustion method

Single-domain particles of SrFe8Al4O19 were prepared by thermal treatment of porous products of citrate–nitrate autocombustion at 1200 °C, and the effect of synthesis time on the particle morphology and magnetic properties was estimated. The procedure allows one to obtain SrFe8Al4O19 particles with mean diameters of 100–460 nm and coercivity ranges from 14.5 to 18.4 kOe, while ferromagnetic resonance frequencies vary from 149 to 164 GHz.

Electrical conductivity of poly(methyl methacrylate) nanocomposites containing interconnected carbon nanohybrid network based on Pickering emulsion strategy

ABSTRACT The formation of three-dimensional (3D) interconnected carbon network throughout insulative polymer matrix is advantageous to elaborating electrically conductive nanocomposites. Herein, oil-in-water (O/W) Pickering emulsion stabilized by carbon nanohybrids assembled with reduced graphene oxide (RGO) and carbon nanotubes (CNTs) was utilized as a template to achieve core-shell structured poly(methyl methacrylate) (PMMA) microsphere. The effect of synthesis time on the amphiphilicity of carbon nanohybrid stabilizer is studied. Investigations on the as-prepared Pickering emulsion and the electrical conductivity of the derived carbon nanohybrid composites were directed with respect to the concentration and formulation of carbon nanohybrid stabilizer, respectively. Considering a balance between electrical and mechanical properties, 0.74 wt% of carbon nanohybrid stabilizer was used to form O/W Pickering emulsion, which was responsible for the electrical conductivity of 4 × 10−8 S m−1 for the resulting RGO/CNTs/PMMA nanocomposites. The processing-structure-property relationship of carbon nanocomposites based on O/W Pickering emulsion strategy is further demonstrated in scanning electron microscopy (SEM) observation and thermo-mechanical analysis. The processing and functional synergies between GO and CNTs are identified to efficiently construct interconnected electrically conductive pathway in polymer matrix.

Surfactin as a Green Agent Controlling the Growth of Porous Calcite Microstructures.

This study presents a new, simple way to obtain mesoporous calcite structures via a green method using an eco-friendly surface-active compound, surfactin, as a controlling agent. The effects of synthesis time and surfactin concentration were investigated. The obtained structures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) coupled with gas mass spectrometry (QMS) analysis. The experimental data showed that surfactin molecules significantly changed the morphology of the calcite crystals, roughening and deforming the surface and creating a greater specific surface area, even at low biosurfactant concentrations (10 ppm). The size of the crystals was reduced, and the zeta potential value of calcium carbonate was more negative when more biosurfactant was added. The XRD data revealed that the biomolecules were incorporated into the crystals and slowed the transformation of vaterite into calcite. It has been shown that as long as vaterite is present in the medium, the calcite surface will be less deformed. The strong influence of surfactin molecules on the crystal growth of calcium carbonate was due to the interaction of surfactin molecules with free calcium ions in the solution as well as the biomolecules adsorption at the formed crystal surface. The role of micelles in crystal growth was examined, and the mechanism of mesoporous calcium carbonate formation was presented.

Nanoporous bimetallic metal-organic framework (FeCo-BDC) as a novel catalyst for efficient removal of organic contaminants

In this work, we report on the synthesis and characterization of nanoporous bimetallic metal-organic frameworks (FeCo-BDC). Effects of synthesis time and temperature on the structures, morphology, and catalytic performance of FeCo-BDC were investigated. Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) were used to reveal the morphological and textural characteristics. The crystal structure and chemical composition of FeCo-BDC were determined by means of X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measurements. Interestingly, FeCo-BDC grew into the same crystal structure with different morphology in the temperature of 110–150 °C with 12–48 h. The heterogeneous catalytic activity of FeCo-BDC was tested to activate peroxydisulfate (PDS) and peroxymonosulfate (PMS) for removal of methylene blue (MB). The results found that FeCo-BDC synthesized at 150 °C with 24 h exhibited the best catalytic performance for PMS and obtained 100% of MB removal within 15 min. The abundant unsaturated metal active sites of Fe(II) and Co(II) in the skeleton of FeCo-BDC made a great contribution to the generation of sulfate (▪) and hydroxyl radicals (OH), which resulted in the excellent performance for MB degradation.

Structural and electrical properties of BCZT ceramics synthesized by sol–gel-hydrothermal process at low temperature

A novel method, sol–gel-hydrothermal process, was employed to prepare Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powders at a rather lower temperature of 180 °C. The effects of synthesis time on the structure, morphology and size distribution of the powders were studied by the means of XRD, SEM and FTIR. BCZT powders could be obtained at a suitable synthesis time of 12 h, which were well-crystallized and compositional uniform with an average particle size of 93 nm. BCZT ceramics sintered from the synthesized powders had a dense microstructure with a density of 5.59 g/cm3 (> 95%) and excellent properties (2Pr = 25.12 μC/cm2, 2Ec = 4.31 kV/cm, d33 = 492pC/N, er = 9173), indicating the high activity of the BCZT powders by sol–gel-hydrothermal process.

Effect of synthesis time on morphology of CeO2 nanoparticles and Au/CeO2 and their activity in oxidative steam reforming of methanol

Ceria (CeO2) supports, synthesized by hydrothermal treatment with different synthesis time (CeO2-X h, where X is the synthesis time in h) in the presence of the surfactant cetyltrimethyl ammonium bromide, were used as supports for gold (Au) catalysts. The synthesis time significantly affects the morphological structure and crystallite size of CeO2, where CeO2-2 h has the smallest crystallite size with coexisting nanorods and nanoparticles. Transmission electron microscopy analysis confirms the morphology of CeO2 with distinctive (110), (100) and (111) planes, in agreement with interplanar spacings of 0.19, 0.27 and 0.31, respectively. However, the morphology of CeO2-8 h and CeO2-48 h is mainly a truncated octahedral with crystal planes (111) and (100) accompanied by an interplanar spacing of 0.31 and 0.27 nm, respectively. The CeO2-X h supports and those with a 3 wt% Au loading (Au/CeO2-X h) were investigated in the oxidative steam reforming of methanol at temperatures between 200 and 400 °C. The Au/CeO2-2 h gave the highest methanol conversion level and hydrogen yield at a low temperature of 250 °C. This superior catalytic performance results from the good interaction between the metal and support and the well-distributed Au species on the CeO2 support.

Synthesis of greigite (Fe3S4) particles via a hydrothermal method

Greigite (Fe3S4) particles, with strong ferrimagnetic behavior, have been found to have desirable uses in the areas of biomedical and environmental applications. Size-dependent magnetic properties of greigite can play a crucial role in efficiency of its applications. This study reviews two synthetic approaches to producing such particles. The methods tested within this study include a coprecipitation synthesis and a hydrothermal process. While the coprecipitation method proved to be ineffective at producing greigite, the hydrothermal process showed promise after consistently producing greigite. For the hydrothermal process, the effects of synthesis time, autoclave atmosphere, and polyvinylpyrrolidone (PVP) addition as a capping agent to control particle growth were investigated using X-ray diffractometry (XRD) with Rietveld refinement, vibrating sample magnetometry (VSM), and scanning electron microscopy (SEM). The results show that, while pyrite (FeS2) forms as an impurity phase, increasing the synthesis time up to 18 hours increases the greigite fraction up to 70 wt% and saturation magnetization up to ∼ 35 emu/g for the powder synthesized in argon. The SEM micrographs of this sample reveal a mean greigite particle size of ∼ 700 nm. It was found that adding PVP brings about a much more uniform microstructure of agglomerated plate-shape particles with nano-sized features.

Synthesis and room temperature NO2 gas sensitivity of vanadium dioxide nanowire structures by chemical vapor deposition

Vanadium dioxide (VO2) nanowire structures were synthesized by chemical vapor deposition on unpolished quartz substrates. The effects of synthesis time, from 2 h to 6 h, on VO2 nanowires structure and room temperature NO2 gas sensing properties were studied. We used field emission scanning electron microscope and X-ray diffraction to characterize the morphology and crystal structure of the nanowires. The results show that networked VO2 nanowire structure was obtained at deposition time of 4 h. The structure evolution process was related to the strong interfacial interaction and continuing growth on the rough substrate surface. We explored the sensitivity of nanowires structure to 1–5 ppm NO2 gas at room temperature. The samples at deposition time of 4 h had the highest sensitivity for the networked structure. This study provides a reference for the fabrication of high performance NO2 gas sensor based on metal oxide semiconductor nanowire structures.

Preparation, Photoelectrochemical Properties and Biosensor Applications of Oriented 2-D ZnIn2S4 Nanosheet Arrays for Detecting Glutathione (GSH)

In this study, two-dimensional (2-D) ZnIn2S4 nanosheet arrays (NSAs) have been prepared on the arbitrary substrates directly through a facile one-pot hydrothermal route. The effect of synthesis time, synthesis temperature and substrate type were investigated on the surface morphologies of the obtained ZnIn2S4 membranes. It was found that the optimal growth conditions were 200°C, 2 h and fluorine doped tin oxide (FTO) used as the substrate. Besides, the influence of growth time on the photoelectrochemical (PEC) properties of ZnIn2S4 was investigated. It was demonstrated that the best PEC performance was achieved in the 2 h sample (200°C, FTO substrates), which displayed a photocurrent density of ∼ 1.0 mA/cm2 versus reversible hydrogen electrode under a simulated solar irradiation (AM1.5G, with an intensity of 100 mA/cm2). The Mott–Schottky (M–S) plots indicated that the 2 h sample owned the highest donor density (ND) and the most positive flat-band potential (VFB), suggesting that the enhanced PEC performance might be resulting from a better n-type conductivity of the ZnIn2S4 electrode. Further, the PEC biosensors were fabricated by using a ZnIn2S4 photoanode for detection of the glutathione (GSH), leading to an excellent detect limit of 1500 mA cm−2 M−1 and sensitivity of 33 nM.

Pervaporation dehydration of acetic acid through hollow fiber supported DD3R zeolite membrane

Abstract All-silica Decadodecasil 3R (DD3R) zeolite membranes were prepared on four-channel ceramic hollow fibers by seeding with ball-milled Sigma-1 zeolites and hydrothermal synthesis method. Effect of synthesis time on membrane structure and morphology was investigated and the membrane quality was evaluated by CO2/CH4 binary gas separation. The as-prepared membranes were further used in pervaporation dehydration of acetic acid (AcOH) for the first time. Although behaving strong hydrophobicity, the defect-free DD3R zeolite membrane exhibited a good water-selective permeability based on molecular-sieving mechanism. A water permeation flux of 0.58 kg m−2 h−1 as well as a separation factor of 800 was achieved in dehydration of 70 wt% water/AcOH mixture at 368 K. Both experimental and molecular simulation studies were explored to investigate the influence of pervaporation condition on membrane separation performance. The results showed that both high temperature and feed water content were beneficial for improving the water flux and separation factor. The long-term pervaporation test revealed that hydrophobic DD3R zeolite membrane behaved stable permeation flux and separation factor in dehydration of AcOH, even in the presence of inorganic acid, confirming the excellent acid-resistance of its all-silica framework structure.

Novel ternary g-C3N4/Ag3VO4/AgBr nanocomposites with excellent visible-light-driven photocatalytic performance for environmental applications

Novel visible-light-induced photocatalysts were fabricated by integration of Ag3VO4 and AgBr semiconductors with graphitic carbon nitride (g-C3N4) through a facile refluxing method. The fabricated photocatalysts were extensively characterized by XRD, EDX, SEM, TEM, FT-IR, UV–vis DRS, BET, TGA, and PL instruments. The photocatalytic performance of these samples was studied by degradations of three dye contaminants under visible-light exposure. Among the ternary photocatalysts, the g-C3N4/Ag3VO4/AgBr (10%) nanocomposite displayed the maximum activity for RhB degradation with rate constant of 1366.6 × 10−4 min−1, which is 116, 7.23, and 38.5 times as high as those of the g-C3N4, g-C3N4/AgBr (10%), and g-C3N4/Ag3VO4 (30%) photocatalysts, respectively. The effects of synthesis time and calcination temperature were also investigated and discussed. Furthermore, according to the trapping experiments, it was found that superoxide anion radicals were the predominant reactive species in this system. Finally, the ternary photocatalyst displayed superlative activity in removal of the contaminants under visible-light exposure, displaying great potential of this ternary photocatalyst for environmental remediation, because of a facile synthesis route and outstanding photocatalytic performance.