Effect Of Synthesis Temperature Research Articles

Synthesis, structure and electromagnetic properties of FeCoAl/C nanocomposites

Magnetic nanoparticles play an important role in rapidly developing advanced branches of science and industry, e.g. fabrication of magnetic storage media, synthesis of ferromagnetic liquids, medicine and chemistry. One problem faced in the usage of magnetic nanoparticles is their high chemical activity leading to oxidation in air and agglomeration. The chemical activity of magnetic nanoparticles stems from the contribution of their large specific surface to volume ratio. Carbon coating of nanoparticles reduces the interaction between nanoparticles. FeCoAl/C metal-carbon nanocomposites have been synthesized using IR pyrolysis of polymer/metal salt precursors. The effect of synthesis temperature (IR heating) in the range from 500 to 700 °C on the structure and composition of the nanomaterials has been studied. We show that the forming particles are the FeCoAl ternary solid solution with a FeCo based bcc lattice. An increase in the synthesis temperature from 500 to 700 °C leads to an increase in the coherent scattering region of three-component nanoparticles from 5 to 19 nm. An increase in the aluminum content from 20 to 30% relative to Fe and Co results in an increase in the size of the nanoparticles to 15 nm but this also entails the formation of a Co based solid solution having an fcc lattice. An increase in the nanocomposite synthesis temperature and a growth of the relative Al content as a result of a more complete carbonization and the structure-building effect of metals reduce the degree of amorphousness of the nanocomposite carbon matrix and lead to the formation of graphite-like phase crystallites having an ordered structure. The effect of synthesis temperature and relative content of metals on the electromagnetic properties (complex permittivity and permeability) of the synthesized nanocomposites has been studied. Synthesis conditions affect the radio absorption properties of the nanocomposites, e.g. reflection loss (RL) in the 3–13 GHz range.

Advances in metal-based vanadate compound photocatalysts: synthesis, properties and applications

Among the ongoing research on photocatalysis under visible-light, it has been shown that doped or hybrid catalysts are more active than a single catalyst alone. However, problems including visible light absorption, a low quantity of energetic sites on surfaces, and rapid recombination of the photo-electron hole pair produced by light have prohibited photocatalysts from being used in a practical and widespread manner. To overcome these problems, synthesis of nanostructure hybrid catalyst using several methods has attracted much attention. Several procedures have been suggested for the preparation of photocatalysts with the desired structure and morphology. Preparation methods similar to partial modification may lead to diverse structures and qualities. In this regard, the development of efficient, low-cost photocatalysts and rapid synthesis is the most important issues that should be considered. This review discusses various methods and mechanisms that work with the modification of vanadium compounds as photocatalysts to progress their photocatalytic efficiency. In addition, the effects of synthesis temperature, solution pH and concentration on the photocatalytic performance are also described in detail.

Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites and Their Ultra-Fast Adsorption of Methylene Blue Dye.

The industry development in the last 200 years has led to to environmental pollution. Dyes emitted by pharmaceutical and other industries are major organic pollutants. Organic dyes are a pollutant that must be removed from the environment. In this work, we adopt a facile microwave hydrothermal method to synthesize ZnFe2O4/rGO (ZFG) adsorbents and investigate the effect of synthesis temperature. The crystal structure, morphology, chemical state, and magnetic property of the nanocomposite are investigated by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and a vibrating sample magnetometer. Furthermore, the synthesized ZFGs are used to remove methylene blue (MB) dye, and the adsorption kinetics, isotherm, mechanism, and reusability of this nanomaterial are studied. The optimal ZFG nanocomposite had a dye removal percentage of almost 100%. The fitting model of adsorption kinetics followed the pseudo-second-order model. The isotherm model followed the Langmuir isotherm and the theoretical maximum adsorption capacity of optimal ZFG calculated by this model was 212.77 mg/g. The π–π stacking and electrostatic interaction resulted in a high adsorption efficiency of ZFG for MB adsorption. In addition, this nanocomposite could be separated by a magnet and maintain its dye removal percentage at almost 100% removal after eight cycles, which indicates its high suitability for utilization in water treatment.

Time-Retrenched Synthesis of BaTaO2N by Localizing an NH3 Delivery System for Visible-Light-Driven Photoelectrochemical Water Oxidation at Neutral pH: Solid-State Reaction or Flux Method?

Among 600 nm class transition-metal oxynitrides, BaTaO2N with a cubic Pm3̅m perovskite-type structure is promising for solar water oxidation due to its absorption of visible light up to 660 nm, narrower band gap (Eg = 1.9 eV), appropriate valence band edge position for oxygen evolution, good stability in concentrated alkaline solutions, and nontoxicity. However, high defect density stemmed from long high-temperature ammonolysis limits the separation and transfer efficiency of photogenerated charge carriers in BaTaO2N. Here, a NH3 delivery system is specifically localized just above the synthesis mixture to reduce the synthesis time and defect density of BaTaO2N by a fresh supply of more active nitriding species and minimizing the generation of N2 and H2. Particularly, the effects of synthesis temperature (700–950 °C), synthesis time (1–8 h), and gas composition are systematically investigated to gain insights into the formation of single-phase BaTaO2N by solid-state reaction and flux method. Time-dependent experiments conducted at 950 °C show that single-phase BaTaO2N can be synthesized ≥6 and ≥4 h by solid-state reaction and flux method, respectively, revealing the advantage of the flux method over solid-state reaction in a localized NH3 delivery system. Subsequently, the separation and transfer efficiency and kinetics of photogenerated charge carriers are studied in BaTaO2N samples. Photoelectrochemical studies made it possible to resolve trends during visible-light-induced water oxidation, evidencing the inverse relationship between recombination and charge transfer phenomena. Transient absorption spectroscopy reveals that the dynamics of the photogenerated charge carriers in both types of BaTaO2N samples are different: (i) BaTaO2N synthesized by flux method has a greater number of holes despite the similar number of deeply trapped charge carriers and (ii) solid-state reaction led to the formation of a higher number of free electrons in BaTaO2N. The findings demonstrate the advantage of reducing the transfer distance of active nitriding species to the surface of the synthesis mixture for enhancing the photoelectrochemical water oxidation of BaTaO2N at neutral pH.

Preparation of GdCoO3 by Sol-Gel Method and Its Photocatalytic Activity

Using gadolinium nitrate, cobalt acetate, citric acid as main raw materials, GdCoO3 was successfully prepared by sol-gel method. The prepared samples were characterized by thermogravimetric differential scanning analysis (TG-DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy(FT-IR). Using methyl orange solution as simulated sewage, it was investigated that the effects of synthesis temperature and illumination time on photocatalytic activity of GdCoO3. The results show that the pure cubic perovskite GdCoO3 samples can be prepared at calcination temperature of 700 °C to 1000 °C. The GdCoO3 calcined at 900 °C has uniform particles and an average grain size of about 0.5 μm to 1 μm. The photocatalytic performance of GdCoO3 calcined at 900 °C sample was the best. Under the condition of UV-light for 120 min, the photocatalytic degradation rate of methyl orange reached more than 96% in presence GdCoO3 calcined at 900 °C. This indicates that GdCoO3 has good photocatalytic performance.

Characterization and Photocatalytic Activity of TmVO4 Prepared by Hydrothermal Method

Using thulium oxide, nitric acid, ammonium metavanadate and citric acid as main raw materials, TmVO4 was successfully prepared by hydrothermal method. TmVO4 samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetry differential scanning calorimetry (TG-DSC), and Fourier transform infrared spectroscopy (FT-IR). Taking methyl orange solution as simulated sewage, the effects of synthesis temperature and illumination time on the photocatalytic activity of TmVO4 were studied. The results show that pure tetragonal zircon TmVO4 samples can be obtained under hydrothermal conditions of 120 °C to 180 °C. The sample prepared at 140°Chas uniform grain size, and the average grain size is about 50 nm. Under ultraviolet light illumination for 30 min, the degradation rate of 10 mg/L methyl orange can reach more than 77% in the presence of TmVO4. The photocatalysis experiment indicated that TmVO4 has good photocatalytic degradation activity for methyl orange.

The effect of synthesis temperature on the structural and electrochemical properties of S and N doped rGO electrodes

As the demand for alternative energy sources grows, new electrode materials for electrochemical supercapacitors are being developed. Heteroatom doped rGO sheets have attracted much attention in recent time. S and N doped rGO was prepared at various temperatures by a simple and low cost hydrothermal method in the present work. The successful formation of S and N doped rGO sheets is confirmed by structural characterization of prepared samples. The EDX and BET surface analysis shows the optimum doping of S and N and the highest surface area in SNrGO-140 sample, respectively. The electrochemical profile study shows that the SNrGO-140 has the maximum specific capacitance value of 332.5 F/g at a scan rate of 10 mV/s. The result observed suggested that S and N doped rGO prepared at 140 °C is the suitable electrode material to be used in high energy electrochemical supercapacitors.

Synthesis of High-Quality Mg-MOF-74 Thin Films via Vapor-Assisted Crystallization.

The unique features of metal-organic frameworks (MOFs), such as their large surface areas and diversity of structures, make them suitable for a broad range of applications including storage, separation, and sensing of gases. Among all the MOFs, Mg-MOF-74 with the highest CO2 uptake at 1 bar and 25 °C would be particularly beneficial for CO2-related applications. One of the most critical enabling technologies for implementing Mg-MOF-74 is the preparation of dense and continuous films that would maximize the sorption behaviors. However, Mg-MOF-74 thin films present significant challenges in demonstrating large-scale coatings. Herein, we demonstrate for the first time high-quality Mg-MOF-74 films synthesized via a vapor-assisted crystallization (VAC) process. The VAC process described herein provides dense and highly crystalline layers of the Mg-MOF-74 thin film with a low coefficient of variation of film thickness below 7%. By minimizing the solvent use, the VAC process is also more environmentally friendly than conventional techniques. In this work, we first optimized a precursor solution for the VAC process and then investigated the effects of synthesis temperature, time, and droplet volume on the growth, crystallinity, and thickness of VAC Mg-MOF-74 films. The porosity of the MOF film was assessed by measuring the CO2 uptake at room temperature and 1 bar. The obtained VAC Mg-MOF-74 films possess a well-defined microporosity, as deduced from CO2 adsorption studies via quartz crystal microbalance (QCM) and comparison with bulk Mg-MOF-74 reference data. Furthermore, CO2 cyclic adsorption-desorption experiments on the VAC Mg-MOF-74 films showed scaled uptakes to a wide range of CO2 concentration without showing significant variations in the baseline. We specifically demonstrate how the film's quality of the MOF affects adsorption behavior of CO2 on VAC Mg-MOF-74 and drop-cast Mg-MOF-74 films.

Effect of synthesis temperature on catalytic activity and coke resistance of Ni/bio-char during CO2 reforming of tar

Understanding how the synthesis parameters affect nickel particle distribution is critical to the synthesis of Ni/bio-char with excellent catalytic performance. In this work, the influence of synthesis temperature on catalytic activity and coke resistance of Ni/bio-char during CO2 reforming of tar was explored. With the increase of synthesis temperature from 200 °C to 250 °C, the dispersion of nickel precursor into bio-char was promoted, resulting in an increase in crystallite size of metallic nickel particle from 51.98 nm to 62.45 nm. Besides, parts of the metallic nickel particles were oxidized to nickel oxides, providing more lattice oxygen to oxidize the coke deposited on the catalyst. However, further increasing the synthesis temperature to 300 °C would aggravate the oxidation of active nickel particles. The increase in crystallite size of nickel oxide particle from 23.25 nm to 43.38 nm could block the pore structure and hinder the access of reactants, resulting in a drop in the tar conversion rate from 40-51% to 13–27%.

Rapid synthesis of Nd-doped Y3Fe5O12 garnet waste forms by microwave sintering

The garnet structure is a promising solid material for nuclear waste because it can contain all kinds of actinides. Yttrium iron garnet Y3Fe5O12 (YIG) is the model component of this kind of substitute. In this study, Nd-doped YIG ceramic samples were prepared by microwave sintering at different sintering temperatures (1100 °C, 1200 °C, and 1300 °C) for different sintering time (0.5 h, 2 h, 4 h, and 6 h). The effects of synthesis temperature and sintering time on the solubility and microstructure of Y3-xNdxFe5O12 (0 ≤ x ≤ 3.0) were evaluated. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and backscattering scanning electron microscopy (EBSD) results show that single phase garnet structure can be synthesized and enhanced solubility of Nd in YIG was found at higher temperatures. The solubility of Nd in garnet is 50 mol% (x = 1.5) and 60 mol% (x = 1.8) at 1200 °C and 1300 °C, respectively. There is no significant dependence of the solubility on sintering time. The SEM analysis and Archimedes drainage test show that the relative density of Y1.2Nd1.8Fe5O12 ceramics is 88.15% and 99.94% at 0.5 h and 6 h, respectively, indicating dense YIG could be obtained with a relatively long sintering time. The results show that microwave sintering can rapidly and efficiently synthesize the YIG ceramic samples.

Crystal phase, morphology evolution and luminescence properties of Eu3+ -doped BiPO4 phosphor prepared using the hydrothermal method.

A series of Bi1-x Eux PO4 phosphors was successfully prepared using an easy citric acid- assisted hydrothermal method. The effects of synthesis temperature, amount of citric acid, and Eu3+ concentration on the crystal phase, morphology, and luminescence properties were investigated. X-ray diffraction results revealed that BiPO4 :Eu3+ formed a hexagonal phase at 80°C, although it transformed to a monoclinic phase when the hydrothermal temperature was increased to 160°C. Moreover, it was found that a small amount of Eu3+ doping and the addition of citric acid introduced no secondary or related phases. The morphologies of the samples varied from nanoparticles to spherical microparticles to polyhedrons after the synthesis temperature was adjusted. Particle size was controlled by adding different amounts of citric acid. Under 394 nm excitation, the Bi0.95 Eu0.05 PO4 phosphor prepared at 160°C with 0.3 g of citric acid had excellent luminescence properties. A possible crystal growth mechanism during this reaction is proposed.

Influence of Synthesis Temperature on the Phases Developed and Optical Properties of Manganese Sulfide and Zinc Sulfide

AbstractNano MnS and ZnS samples are prepared through a simple thermolysis procedure. The effect of synthesis temperature on the different phases formed and their percentages, and on the lattice parameters and crystallite size of MnS and ZnS is examined using Rietveld analysis for X‐ray diffraction patterns. The minimum synthesis temperature at which MnS can be formed by the present simple procedure is 250 °C, while ZnS can be prepared at a lower temperature of 200 °C. For manganese sulfide, traces of Mn3O4 phase appear at 300 °C and increase with temperature, while ZnS resists oxidation until 500 °C; pure ZnO forms at 700 °C. The MnS and ZnS samples, obtained at all temperatures, are found to be biphasic; cubic and hexagonal. The nano nature of the samples and the particle morphology are investigated by high‐resolution transmission electron microscopy. Fourier‐transform infrared spectroscopy is applied to follow the characteristic vibration bands in both systems. The values of the different energy gaps depend on the crystallite size, phases’ percentages, and the preparation temperature. The photoluminescence intensity and the emitted colors from MnS and ZnS depend on the synthesis temperature.

Effect of synthesis technique on developing lanthanum magnesium hexaaluminate powders as an alternative for thermal barrier coating

AbstractCitric acid sol-gel technique and solid-state reaction method were used for synthesizing high purity lanthanum magnesium hexaaluminate powders. The samples were calcined at 1150°C, 1250°C, and 1350°C to understand the effect of synthesis temperature on the LaMgAl11O19(LMA) samples. The collective effect of the synthesis technique and the synthesis temperature on developing lanthanum magnesium hexaaluminate powders were analyzed using XRD, FTIR, SEM, TGA-DSC, and Particle analyzer. LMA powders obtained through sol-gel techniques showed better uniformity and pure LMA phase, while the ball milling method displayed traces of intermediate phases. The synthesized powders in the crystallite size of 150 nm and 280 nm were obtained through the sol-gel and ball milling technique, respectively. Citric acid sol-gel technique aided in the early onset of phase formation and the required closely packed platelet formation with a particle size of around 150 nm with good uniformity.

Effect of Synthesis Temperature on Luminescent Properties of Carbon dots Originated from Sucrose

Effect of Synthesis Temperature on Luminescent Properties of Carbon dots Originated from Sucrose

Controllable synthesis of sulfurized polyacrylonitrile nanofibers for high performance lithium–sulfur batteries

Sulfurized polyacrylonitrile (SPAN) is regarded to be one of the most promising cathode materials for lithium–sulfur (Li–S) batteries because of its unique chemical structure and high cyclic ability. However, the physicochemical properties of SPAN correlate with the synthesis and process conditions. In this work, flexible and freestanding SPAN nanofiber cathodes are prepared via the electrospinning technique followed by a sulfurization process. And the effect of synthesis temperatures on microstructure and electrochemical performance of SPAN are systematically investigated. According to the spectroscopic analysis, short –Sx– (2 ≤ x ≤ 3) chains are covalently bonded to the cyclized and dehydrogenated PAN backbones through C–S bonds during the synthesis temperature between 300 and 600 °C. Among which, the SPAN nanofiber prepared at 500 °C shows not only a low charge transfer resistance but also the best cell performance. Upon 200 cycles, it displays a high reversible capacity of 1280 mAh g–1 with a fading rate as low as 0.02% per cycle at 400 mA g–1. Highly stable long-term cycling at higher current densities and good rate capability are also achieved. The work provides significant guidance for the development of advanced SPAN cathode materials.

Role of Curing Temperature of Poly(Glycerol Sebacate) Substrates on Protein-Cell Interaction and Early Cell Adhesion.

A novel procedure to obtain smooth, continuous polymeric surfaces from poly(glycerol sebacate) (PGS) has been developed with the spin-coating technique. This method proves useful for separating the effect of the chemistry and morphology of the networks (that can be obtained by varying the synthesis parameters) on cell-protein-substrate interactions from that of structural variables. Solutions of the PGS pre-polymer can be spin-coated, to then be cured. Curing under variable temperatures has been shown to lead to PGS networks with different chemical properties and topographies, conditioning their use as a biomaterial. Particularly, higher synthesis temperatures yield denser networks with fewer polar terminal groups available on the surface. Material-protein interactions were characterised by using extracellular matrix proteins such as fibronectin (Fn) and collagen type I (Col I), to unveil the biological interface profile of PGS substrates. To that end, atomic force microscopy (AFM) images and quantification of protein adsorbed in single, sequential and competitive protein incubations were used. Results reveal that Fn is adsorbed in the form of clusters, while Col I forms a characteristic fibrillar network. Fn has an inhibitory effect when incubated prior to Col I. Human umbilical endothelial cells (HUVECs) were also cultured on PGS surfaces to reveal the effect of synthesis temperature on cell behaviour. To this effect, early focal adhesions (FAs) were analysed using immunofluorescence techniques. In light of the results, 130 °C seems to be the optimal curing temperature since a preliminary treatment with Col I or a Fn:Col I solution facilitates the formation of early focal adhesions and growth of HUVECs.

Features of Structure and Phase Formation during Synthesis of AIN–Al2O3–Y2O3 Composites in a Combustion Regime

Results are given for synthesis of AlN–Al2O3–Y2O3 composites in a combustion regime in an industrial reactor. The effect of synthesis temperature on formation of the microstructure, phase composition, and impurity oxygen content dissolved in the crystal lattice of aluminum nitride is studied. The optimum synthesis temperature is determined. Experimental batches of composite powders are produced for the manufacture of dielectric ceramics with high thermal conductivity.

Formation of phosphonate coatings for improved chemical stability of upconverting nanoparticles under physiological conditions.

Upconverting nanoparticles (UCNPs) are being extensively investigated for applications in bioimaging because of their ability to emit ultraviolet, visible, and near-infrared light. NaYF4 is one of the most suitable host matrices for producing high-intensity upconversion fluorescence; however, UCNPs based on NaYF4 are not chemically stable in aqueous media. To prevent dissolution, their surfaces should be modified. We studied the formation of protective phosphonate coatings made of ethylenediamine(tetramethylenephosphonic acid), alendronic acid, and poly(ethylene glycol)-neridronate on cubic NaYF4 nanoparticles and hexagonal Yb3+,Er3+-doped upconverting NaYF4 nanoparticles (β-UCNPs). The effects of synthesis temperature and ultrasonic agitation on the quality of the coatings were studied. The formation of the coatings was investigated by transmission electron microscopy, zeta-potential measurements, and infrared spectroscopy. The quality of the phosphonate coatings was examined with respect to preventing the dissolution of the NPs in phosphate-buffered saline (PBS). The dissolution tests were carried out under physiological conditions (37 °C and pH 7.4) for 3 days and were followed by measurements of the dissolved fluoride with an ion-selective electrode. We found that the protection of the phosphonate coatings can be significantly increased by synthesizing them at 80 °C. At the same time, the coatings obtained at this temperature suppressed the surface quenching of the upconversion fluorescence in β-UCNPs.

The Effect of Synthesis Temperature on Carbon Nanospheres from Palm Kernel Fiber

The Effect of Synthesis Temperature on Carbon Nanospheres from Palm Kernel Fiber

Effect of Synthesis Temperature on Size, Structure, and Volume Phase Transition of Polysaccharide Microgels

High-molecular-weight polysaccharide microgels were synthesized at a range of temperatures above the polymer lower critical solution temperature (LCST) (ΔT = 0.6–18.1 °C), and ΔT was found to strongly influence the structure, dynamics, and volume phase transition temperature of the resulting particles. Static and dynamic light scattering studies and mean field theory analysis of the microgels below and above volume phase transition revealed several distinct regimes. At small ΔT, lower density, larger, and more polydisperse microgels that deswell by a factor 10 in volume were synthesized. At intermediate ΔT = 5–8 °C, the formed microgels were the smallest, densest, and most monodisperse below the transition, but exhibited deswelling only by a factor of 5 above the transition. Synthesis at high ΔT led to the formation of nonuniform microgels with small density, a high degree of polydispersity, and in some cases the apparent presence of the un-cross-linked polymer. Furthermore, the volume phase transition temperature dropped significantly as ΔT increased. This work suggests that synthesis temperature can be used to tune the size, deswelling capacity, and volume phase transition temperature of the polymeric microgels.