Reflux Process Research Articles

The effect of reflux process on the size and uniformity of FePt nanoparticles

FePt nanoparticles attract great research interest for possible application to ultrahigh density magnetic recording media. In this paper, FePt magnetic nanoparticles were synthesized by superhydride reduction of FeCl 2 and Pt(acac)2 at high temperature. Adding superhydride (LiBEt3H) to the phenyl ether solution of FeCl2 and Pt(acac)2 in the presence of oleic acid, oleylamine, and 1,2-hexadecanediol at 200 °C, followed by refluxing at 250 °C, led to monodisperse 3 nm FePt nanoparticles. The effect of reflux process on the size and uniformity of FePt nanoparticles has been investigated. TEM images showed that the size of FePt nanoparticles increase to 4 nm with reflux process and the standard deviation of FePt nanoparticles increase to 10 % which lead to improve the uniformity of FePt nanoparticles. The results of EDS analysis, showed that the Fe shell around FePt nanoparticles increase with increasing reflux time and the composition of FePt nanoparticles gives Fe68Pt32 after 10 min reflux..

Synthesis of Ramsdellite by Refluxing Process and Its Influencing Factors

Nanosized ramsdellite was synthesized by oxidizing 30 mmol Manganese(II) sulfate dissolved in different amounts of hydrochloride(0,10,20 and 40 mmol) with adding 60 mmol sodium hypochlorite solution at constant velocity of 1 mL/min minute using a refluxing process at atmospheric pressure at different temperatures(60,80 and 100℃).The products were characterized by XRD diffraction,scanning electron microscope and automated surface area analyzer.The effects of reflux temperature,time and amount of hydrochloric acid on the crystal structures,micromorphologies and yield of products were investigated.It was observed that nano-particles of conglobated ramsdellite was prepared at 60℃,and particle size increased with elevating the refluxing temperature.Both aggregate level and particle size of ramsdellite decrease after adding hydrochloric acid into the reaction solution.When the reflux reaction was carried out at 100℃ with adding different amount of hydrochloric acid,nano-size particles of ramsdellite were formed firstly,and then needle-like fibers of products came into being formed.The concentration of hydrochloric acid in the reaction system plays an important role in the morphologies of ramsdellite crystal,which acts more remarkably at higher temperatures.It is favorable to the formation of needle-like ramsdellite in nano size and aggregation with loose structures by addition of no less than 10 mmol hydrochloric acid into the reaction solution at 100℃.Ramsdellite particles with high specific surface area(maximum of 66.32 m2/g) are more prone to be formed by adding hydrochloric acid into the reaction solution at lower refluxing temperature.Product yield increases firstly and then decreases with the increase of the amount of hydrochloric acid and refluxing temperature,and the highest yield can be as high as 97.5%.

Nanotubes with hybrid CdTe nanocrystals: Fabrication, property, and surface functional decoration for bioapplications

We have demonstrated a two-step synthesis for preparing morphology- and luminescence-tunable fibers that uses green-emitting CdTe nanocrystals (NCs), Cd2+, thioglycolic acid (TGA), and tetraethyl orthosilicate (TEOS). Hybrid CdTe NCs consisted of a CdTe core and CdS-like clusters in the fibers were created during the synthesis. The CdTe NCs were first coated with a very thin SiO2 shell containing Cd2+ and TGA molecules in an alkaline condition. The SiO2-coated CdTe NCs were assembled together with Cd–TGA clusters for the formation of the fibers. A subsequent reflux process enabled the creation of fibers and caused the formation of CdS-like clusters in the vicinity of CdTe NCs in the fibers. Because of these clusters closed to the CdTe NCs, their effective size increases to reduce the quantum size effect. This special core-shell structure was found to have extraordinary properties: a narrowed photoluminescence (PL) spectrum, a red-shifted PL peak, and a high PL efficiency. The morphology of the fibers (tubal and solid) depends on the concentrations of TGA, Cd2+ ions, and TEOS in the precursor solution together with the concentration of CdTe NCs in a subsequent reflux. These fibers, especially for nanotubes, exhibited not only a tunable morphology and emitting color but also a functional surface, making them well suited for a variety of applications, such as bio-probing and drug delivery. The nanotubes were conjugated with immunoglobulin G (IgG) by using a zero-length cross linker because of carboxyl groups on their surface. The SiO2 component in the nanotubes enables bio-conjugation with IgG through other functional groups, making these nanotubes amenable for bioapplications.

Self-assembly of CdCO3-dye hybrid nanotubes based on Trypan Blue dye

CdCO3-dye hybrid nanotubes were successfully synthesized through a simple reflux process using Trypan Blue (TB) dye as template. The dye was crucial to the formation of CdCO3 hybrid nanotubes. The samples were characterized using thermogravimetric analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy. The effect of different aspects on the crystal morphology of the CdCO3–TB hybrid materials was primarily investigated. A rational mechanism was proposed for the selective formation of CdCO3–TB hybrid nanotubes.

Magnetite (Fe3O4) tetrakaidecahedral microcrystals: Synthesis, characterization, and micro-Raman study

A novel and simple method to prepare Fe3O4 tetrakaidecahedral microcrystals has been demonstrated using a two-step refluxing and calcination process. Firstly, Fe(NO3)3∙9H2O was dissolved in diethylene glycol by refluxing at 190°C for 3h. Secondly, the above solutions were injected into covered quartz crucibles and placed in a tube furnace, and the as-prepared Fe3O4 tetrakaidecahedra were obtained after calcination at 800°C in an N2 atmosphere for 3h. Fe3O4 tetrakaidecahedra were studied with Raman scattering spectroscopy, and a clear direct phase transition from magnetite to hematite (α-Fe2O3) due to laser irradiation was observed in the Raman scattering measurements. This oxidation route is specific to magnetite of larger crystalline size, which is coincident with the microcrystalline feature revealed by scanning electron microscopy measurements.

Shape‐controlled Synthesis of Nanostructure Ramsdellite‐type Manganese Oxide at Atmospheric Pressure

AbstractRamsdellite (R‐MnO2) was prepared by oxidizing bivalent manganese salts, such as MnCl2, MnSO4 and Mn(NO3)2, with NaClO solution using a refluxing process at atmospheric pressure. The products were characterized by X‐ray diffraction, fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and flame photometry. R‐MnO2 microstructure and morphology were controlled by adjusting reaction temperature, the amount of hydrochloric acid (HCl) and anions of bivalent manganese salts. Ramsdellite grain was formed with three different bivalent manganese salts oxidized by NaClO solution at 60°C, and increased with the increase of reflux temperature. R‐MnO2 nanorod and nanowire crystals were obtained when MnCl2 and MnSO4 were used as bivalent manganese salts at 100°C respectively. Nanosized flake of R‐MnO2 came into being when Mn(NO3)2 was applied at 80°C. When 30 mmol MnCl2 was oxidized by 60 mmol NaClO solution with adding 20 mmol HCl in refluxing solution, specific surface area of R‐MnO2 grain obtained at 60°C was greater than 140 m2/g, and the self‐assembly of nanorod bundles into interesting flowerlike architectures was achieved at 100°C. The process of dissolution‐precipitation equilibrium might be the primary cause for the morphology transformation.

ChemInform Abstract: Synthesis of MnPO4·H2O by Refluxing Process at Atmospheric Pressure.

AbstractDepending on the HCl content, aqueous solutions containing Mn(H2PO4)2, 2 equiv.

Preparation and characterization of graphene/CdS nanocomposites

Graphene-based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this paper, we present a facile approach for the preparation of graphene/CdS nanocomposites through simple reflux processes, in which thiourea (CS(NH 2) 2) and thioacetamide (C 2H 5NS) act as a sulphide source, respectively. The samples were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrum (FT-IR), ultraviolet–visible (UV–vis) spectroscopy and thermogravimetry analysis. It was shown that in the nanocomposites, the CdS nanoparticles were densely and uniformly deposited on the graphene sheets, and the sulphide source used has a great influence on the morphology, structure and property of the graphene/CdS nanocomposites. The good distribution of CdS nanoparticles on graphene sheets guarantees the efficient optoelectronic properties of graphene/CdS and would be promising for practical applications in future nanotechnology.

Synthesis of graphene soluble in organic solvents by simultaneous ether-functionalization with octadecane groups and reduction

Octadecane-functionalized graphene (OD-G) soluble in organic solvents was produced by combining the Hummers process for graphite oxidation and a simultaneous ether-functionalization and reduction approach with 1-bromooctadecane in pyridine and dimethylformamide (DMF). The exfoliated OD-Gs were testified to be monolayer sheets by transmission electron microscope (TEM) and atomic force microscopy (AFM). The functionalization with octadecane (OD) groups and the effective deoxygenation of graphene oxide (GO) were confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It is proved that the effective reduction and functionalization of GO could be simultaneously completed during the refluxing process. The functionalization with OD groups can effectively prevent the aggregation of GO during the reduction.

Effect of calcination temperature and atmosphere on crystal structure of BaTiO3 nanofibers

Barium titanate (BaTiO3, BT) nanofibers with a diameter range of 160 nm to 300 nm were prepared by drying electrospun BT/polyvinylpyrrolidone (BT/PVP) composite fibers for 1 h at 80 °C in vacuum with a subsequent calcination in air for 1 h at a temperature range of 650 °C to 750 °C. The morphology and crystal structure of calcined BT nanofibers were characterized with the aid of XRD, FT-IR, SEM, and TEM. The XRD and FR-IR measurements confirm that BT nanofibers with a diameter of about 160 nm and a tetragonal perovskite structure were present in the electrospun fibers after calcination for 1 h at 750 °C. The FR-IR analysis of the BT fibers reveals that the intensity level of the O-H stretching vibration bands (at 3430 cm−1 and 1425 cm−1) become weaker as the calcination temperature is increased and that a broad band at 570 cm−1, which represents the Ti-O vibration, appears sharper and narrower after calcination at 750 °C due to the formation of metal oxide bonds. In contrast, BT fibers prepared by a refluxing process in a nitrogen atmosphere show a dramatic change in crystal structure: the tetragonal structure changes to a cubic perovskite structure, probably due to the suppression of carbonate contamination. Thus, the calcination temperature and atmosphere appear to have a significant influence on the crystal structure of BT.

Ternary Morphological Diagram for Nano(tube−ribbon−sphere) Sodium Titanate Deduced from Raman Spectra Analysis

In this study, sodium hydroxo titanates were synthesized using the reflux process in an alkaline medium. Three distinct morphologies were obtained, nanotubes and nanoribbons as classically encountered in the literature and a new nanosphere-like morphology. After ionic exchange of Na+ ions by protons and annealing, sodium titanates transform into TiO2 nanoparticles with anatase and TiO2(B) structures. We clarified the origin of this polymorphism. Nanoribbons transform into TiO2(B) at 400 °C, whereas nanospheres and nanotubes are converted to TiO2 anatase at 400 and 500 °C, respectively. The quantification of the anatase/TiO2(B) ratio performed by Raman spectroscopy allows us to establish an original ternary morphological diagram. The latter depicts the relative proportion of nanotubes, nanoribbons, and nanospheres composing each titanate and is of great utility in controlling the morphologies of the sodium titanates and correlating them to the synthesis parameters.

Synthesis of MnPO 4·H 2O by refluxing process at atmospheric pressure

Serrabrancaite (MnPO 4·H 2O) was synthesized by oxidizing Mn(H 2PO 4) 2 with NaClO solution using a refluxing process at atmospheric pressure, and a mixed solution of MnCl 2 and H 3PO 4 could substitute for Mn(H 2PO 4) 2 in the process. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Hureaulite was formed when single solution of Mn(H 2PO 4) 2 was refluxed for 12 h at 60 °C. Rodlike hureaulite was fabricated by refluxing reaction of 30 mmol Mn(H 2PO 4) 2 and 60 mmol NaClO solution with adding hydrochloric acid within 40 mmol. Granular hureaulite was formed by refluxing of 30 mmol MnCl 2 and 60 mmol NaClO solution with adding phosphoric acid within 30 mmol. For the two above-mentioned reaction systems, MnPO 4·H 2O was prepared by adding hydrochloric acid no less than 80 mmol and phosphoric acid no less than 60 mmol respectively. MnPO 4·H 2O yield increased with elevating reflux temperature, and increased firstly and then decreased with increasing additional amount of acid. The highest recovery yield of MnPO 4·H 2O reached 84.1% when Mn(H 2PO 4) 2 was performed as bivalent manganese source, and approached 74.0% when MnCl 2 and H 3PO 4 were used instead.

Photocatalytic study of two-dimensional ZnO nanopellets in the decomposition of methylene blue

We report several significant photodecomposition rates of methylene blue (MB) obtained before and after the refluxing process of own-synthesized two-dimensional (2D) zinc oxide (ZnO) nanopellets. Each photodecomposition rate of MB was found highly dependent on the weight of photocatalyst. The existing photodecomposition rate has been successfully improved to a factor of 22.0 times through refluxing process in excessive pyridine where the surface capping ligand (oleic acid) is removed from the 2D ZnO nanopellets. On the other hand, the refluxed photocatalyst (0.04 g) in this study was found to exhibit excellent recyclability up to three cycles. Furthermore, X-ray powder diffraction spectrums for the refluxed photocatatalyst, respectively, before and after three cycles of photocatalytic reactions, has generated the same patterns showing that the photocatalyst is stable and feasible to be used as an efficient photocatalyst material. Hence, these 2D ZnO nanopellets would provide a new alternative route as a highly efficient photocatalyst for wastewater treatment.

Thermal Solvent Reflux and Thermal Solvent Hybrid Experiments

Abstract The experiments and numerical simulations described in this paper were performed to determine the effectiveness of the thermal solvent reflux and steam solvent hybrid processes and to determine the key parameters involved in these two processes. Steam-assisted gravity drainage (SAGD) is the current technology of choice for Athabasca reservoirs. It is commercially proven and delivers high oil rates and high ultimate recoveries. However, it is energy intensive. In addition, steam injection may be limited by lack of water, by regulatory issues or by the fact that some reservoirs are water sensitive. Vapour-assisted petroleum extraction (VAPEX) does not have the energy and water problems associated with SAGD. However, it is inherently slower than SAGD. One solution to the above difficulties is to combine processes by heating the horizontal wellbores. The heat serves to initiate communication between the injector and the producer. In addition, it will increase the rate of diffusion of the solvent into the oil. Heat may be applied by electric heaters, with a closed steam or glycol loop, or by direct injection of steam. In the first three of four experiments described in this report, the wells were electrically heated. In the fourth experiment, steam was co-injected with the solvent. Two experiments using Hillmond oil showed that similar results were obtained whether heating was obtained by electrically heating the wells (thermal solvent reflux process) or by direct steam injection (steam solvent-hybrid process). For these two experiments, the oil rate and recovery were similar. Numerical simulations were used to history match the experiments and effective diffusivity values were estimated. Introduction The objective of the thermal solvent reflux experiments was to develop a solvent-assisted process for recovery of heavy oil from thick, cold reservoirs such as Cold Lake and Athabasca. The thermal solvent process concept (Figure 1) is • Inject solvent and produce oil through horizontal wells • Heat the injection and production wells to reboil the solvent in situ (solvent reflux) (i.e., in-situ recycle of solvent) The advantages of the thermal solvent reflux process are • Requires less heat than SAGD • Less steam plant emissions • Smaller solvent recycle plant on surface • Smaller injection facility needed • Does not inject water into the reservoir • Suitable for reactive reservoirs • No treatment of boiler feed water required • Minimal water disposal • Minimal oil/water separation facilities required • Heat will speed mass transfer over cold VAPEX

A Facile and Generic Strategy to Synthesize Large‐Scale Carbon Nanotubes

An easy method to prepare carbon nanotubes (CNTs) has been demonstrated using a two‐step refluxing and calcination process. First, a readily available inorganic salt, , used as the catalyst precursor was dissolved in the high‐boiling‐point organic solvents (alcohols or polyhydric alcohol) by refluxing at 190∘C for 3 hours. After refluxing, NiO nanoparticles obtained in the solution act as the catalyst, and the organic refluxing solvents are used as the carbon source for the growth of CNTs. Second, CNTs are prepared by calcining the refluxed solution at 800∘C in an N2 atmosphere for 3 hours. Results show that CNT growth possibly originates from carbon rings, with the nanotube walls growing perpendicular to these rings and forming a closed tube at the end.

GaOOH, and β- and γ-Ga2O3nanowires: preparation and photoluminescence

A composite methodology using laser ablation followed by a solution refluxing process was demonstrated to prepare GaOOH and (β-, γ-) Ga2O3 nanowires, where GaOOH and γ-Ga2O3 nanowires were prepared for the first time. The CTAB surfactant and PVP polymer facilitated the nucleation and growth of GaOOH nanorods, and played different roles in selectively controlling the growth rates of different facets. In the PVA/CTAB-assisted reaction, a high aspect ratio (of at least 200) of GaOOH nanowires was approached. The calcination of GaOOH nanowires at a temperature of 500 °C (6 h) transformed them into γ-Ga2O3 nanowires and converted them further into β-Ga2O3 nanowires at 750 °C (18 h). Photoluminescence measurements were conducted at room temperature for the GaOOH and (β-, γ-) Ga2O3 nanowires using a high resolution synchrotron X-ray source. The blue emissions from the GaOOH and (β-, γ-) Ga2O3 nanowires were resolved into a few sharp peaks, and may provide a valuable reference for further understanding the PL mechanisms. Although luminescence spectra of the GaOOH and γ-Ga2O3 nanowires were recorded for the first time, the similar optical band gap and emission contour observed for β-Ga2O3 nanowires suggests that the optical behavior of GaOOH and γ-Ga2O3 nanowires are likely to closely follow the PL mechanisms of β-Ga2O3 nanowires.

A novel poly(o-anisidine)/CoFe 2O 4 multifunctional nanocomposite: Preparation, characterization and properties

A novel poly(o-anisidine) (POA)/CoFe 2O 4 nanocomposite was synthesized by a facile in situ polymerization of o-anisidine in the presence of CoFe 2O 4 nanoparticles which were obtained by a simple refluxing process in ethylene glycol. The structures of the resulting nanocomposite were investigated by means of X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra. The optical, thermal and magnetic properties of the POA/CoFe 2O 4 nanocomposite were characterized by UV–visible spectrometer, thermogravimetry analyzer (TGA) and vibrating sample magnetometer (VSM). It was indicated the existence of CoFe 2O 4 in the POA/CoFe 2O 4 nanocomposite. The scanning electron microscopy (SEM) observation illustrated that POA layers were wrapped on the surface of CoFe 2O 4 nanoparticles appearing as small aggregated globules. The POA/CoFe 2O 4 nanocomposite exhibited a ferromagnetic behavior under applied magnetic field at room temperature. The saturation magnetization of POA/CoFe 2O 4 nanocomposite was lower than that of pure CoFe 2O 4 nanoparticles due to the contribution of non-magnetic POA layers.

Synthesis of solid solutions of Dy xBi 2−xO 3 with x=0, 1 and 2: Structural, optical and ac impedance analysis

Dysprosium hydroxide, bismuth hydroxide and mixed dysprosium bismuth hydroxide are prepared in the form of a gel by means of chemical precipitation technique. A simple gel to crystalline conversion technique has been followed by means of refluxing process. The synthesized hydroxides are characterized by thermogravimetry and differential thermal analysis. The formed hydroxides are converted into its oxides by calcining at a temperature of 700 °C for 2 h and solid solutions of Dy x Bi 2− x O 3 with x=0, 1 and 2 are formed. The hydroxides and oxides of these solid solutions are investigated by means of XRD and found to be polycrystalline in nature. The Nyquist plot shows a single relaxation process. The enhanced conductivity is observed in dysprosium-based oxides and hydroxides. The optical band gap energy is in agreement with the ac conductivity values.

Accurate Methods for Quantifying the Relative Ratio of Anatase and TiO2(B) Nanoparticles

Nanoparticles of TiO2 crystallizing as anatase and TiO2(B) phases with different ratios were synthesized by a three step treatment including an initial reflux process in highly alkaline medium. For the first time, the ratio of each variety has been quantified by analysing the galvanostatic curves during the lithium electrochemical insertion. The weight percentage of TiO2(B) reaches 95% (110 m2 g−1 specific surface area). In order to get quantitative information based on the ratios deduced from electrochemistry, the same TiO2 samples have also been investigated by Raman spectroscopy. This technique shows a sensitivity seven times higher for anatase than TiO2(B) detection compared to electrochemical method. The equation deduced from Raman refinement and electrochemical quantification permits, for the first time, to quantify the anatase/TiO2(B) ratio simply by using Raman spectroscopy.

Factors governing the formation of lithiophorite at atmospheric pressure

AbstractLithiophorite is a naturally occurring Mn oxide mineral commonly found in soils and sediments. The usual method of synthesizing lithiophorite is via a hydrothermal process in an autoclave at relatively high temperature and pressure. In the present study, an alternative, reflux method, at atmospheric pressure, for synthesis of lithiophorite was developed successfully. The influence of reaction duration, temperature, type of precursor birnessite (H-birnessite, Na-birnessite, aged Na-birnessite), and pH on the formation of lithiophorite were investigated by reflux treatment of lithium-aluminum hydroxide complex ion ( )-exchanged birnessite. The results show that the degree of conversion of lithiophorite decreases with decreasing reaction temperature. Lithiophorite can be obtained at pH values from 5.0 to 9.0, but a circumneutral pH is more favorable for formation at atmospheric pressure. Conversion of Na-birnessite (Bir-OH) to lithiophorite is more favored than aged Na-birnessite (Bir-OH-A). Lithiophorite was not obtained by refluxing the ion-exchanged H-birnessite (Bir-H) sample. The rate of conversion of lithiophorite increases with increasing reflux time. Lithiophorite synthesized by a reflux process has pseudo-hexagonal crystals of 0.1–0.5 µm with a chemical composition of Li0.24Al0.46MnO2.67(H2O)1.25. The results have important implications for the origin and underlying mechanism of lithiophorite formation in the environment.