Influence Of Hydrothermal Temperature Research Articles

Controllable Shape Evolution of Cu2O Flowers and Their Morphologies-Dependent Selective CO Oxidation

The flower-like Cu 2 O nanostructures were hydrothermally synthesized without using any template or surfactant. The influences of hydrothermal temperature, reaction time and reactants concentrations on the growth of nanostructures were investigated in detail. The samples were characterized by scanning electron microscope (SEM) and X-ray powder diffraction (XRD). Cu 2 O crystals with different shapes, i.e., flower-like (F-product) cubic box (CB-product) and cubic box with holes in each face (CBH-product), were synthesized by controlling the synthesis parameters and explored for CO catalytic oxidation. It was found that F-product showed higher catalytic than others.

Preparation and ethanol sensing properties of flower-like cupric oxide hierarchical nanorods

Flower-like cupric oxide (CuO) hierarchical nanorods (petal size: 60–100nm in diameter and 500–700nm in length) were synthesized by wet chemical-assisted hydrothermal processing. The samples were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The influence of hydrothermal temperature on the formation of CuO nanoflowers was investigated. Sensors based on CuO nanoflowers were fabricated by coating them on SiO2/Si substrate attached with Pt interdigitated electrodes. Sensing characteristics of the samples were measured and evaluated as a function of operating temperature and ethanol vapor concentration. The results revealed that the p-type semiconductor CuO nanoflowers based sensors exhibit high sensitivity and selectivity toward ethanol vapor with the optimum working temperature at about 230°C.

The Influence of Hydrothermal Temperature on CaO-based Adsorbents Synthesized by Sol-Gel-Hydrothermal Method

To capture carbon dioxide (CO2), a major green house gas from flue gas, several kinds of adsorbents have been synthesized, characterized and tested. In this study, CaO-based adsorbents were synthesized via sol-gel-hydrothermal method and different hydrothermal temperatures (100, 120, 140 and 160°C) have been investigated in order to verify their influence on the CaO-based adsorbents. Experimental results showed that the Ca(OH)2 adsorbent with a mixture of CaCO3 synthesized at 120°C hydrothermal treatment possesses high CO2 adsorption capacity (0.52 g-CO2/g-sorbent) and at 160°C hydrothermal treatment, CaC2O4.H2O adsorbent was observed and its CO2 adsorption capacity was 0.46 g-CO2/g-sorbent for first carbonation/calcination cycle.

Synthesis of Graphene Oxide Based CuO Nanoparticles Composite Electrode for Highly Enhanced Nonenzymatic Glucose Detection

CuO nanoparticles (NPs) based graphene oxide (CuO/GO) composites with different CuO NPs loading amount as well as pure CuO NPs with different hydrothermal temperatures were synthesized using a hydrothermal method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy were employed to characterize the morphology and structures of our samples. The influence of hydrothermal temperature, GO sheet, and loading amount of CuO on particle size and structure of CuO was systemically investigated. The nonenzymatic biosensing properties of CuO/GO composites and CuO NPs toward glucose were studied based on glassy carbon electrode (GCE). The sensing properties of CuO NPs were improved after loading on GO sheets. The CuO/GO composites with saturated loading of the CuO NPs exhibited the best nonenzymatic biosensing behavior. It exhibited a sensitivity of 262.52 μA mM(-1) cm(-2) to glucose with a 0.69 μM detection limit (S/N = 3) and a linear range from 2.79 μM to 2.03 mM under a working potential of +0.7 V. It also showed outstanding long term stability, good reproducibility, excellent selectivity, and accurate measurement in real serum sample. It is believed that CuO/GO composites show good promise for further application on nonenzymatic glucose biosensors.

Morphology-controlled synthesis of SnO2 nanostructures using hydrothermal method and their photocatalytic applications

SnO 2 hierarchical architectures were synthesized by a surfactant-free hydrothermal synthesis route. The influence of hydrothermal temperature and treatment time on the final morphology of the nanomaterials was studied. The as-synthesized nanoparticles were characterized by X-ray powder diffraction (XRD), UV–vis spectroscopy, scanning electron microscopy (SEM) and adsorption isotherm measurement. Degradation of aniline, 4-nitroaniline and 2,4-dinitroaniline as model organic pollutants was studied in the presence and absence of ultraviolet radiation. The effects of experimental parameters including irradiation time, solution pH and organics structure on the degradability were studied. The photodegradation of the pollutants followed first-order kinetics. The influence of SnO 2 morphology on its photocatalytic activity was comparatively investigated. The SnO 2 flower-shaped catalysts showed higher activity compared with others suggesting that the morphology of the catalysts exerts a noticeable influence on their performances.

Influence of Hydrothermal Temperature on Phosphorus Recovery Efficiency of Porous Calcium Silicate Hydrate

Porous calcium silicate hydrate (PCSH) was synthesized by carbide residue and white carbon black. The influence of hydrothermal temperature on phosphorus recovery efficiency was investigated by Field Emission Scanning Electron Microscopy (FESEM), Brunauer‐Emmett‐Teller (BET), and X‐Ray Diffraction (XRD). Hydrothermal temperature exerted significant influence on phosphorus recovery performance of PCSH. Hydrothermal temperature 170°C for PCSH was more proper to recover phosphorus. PCSH could recover phosphorus with content of 18.51%. The law of Ca2+ and OH− release was the key of phosphorus recovery efficiency, and this law depended upon the microstructure of PCSH. When the temperature of synthesis reached to 170°C, the reactions between CaO and amorphous SiO2 were more efficient. Solubility of SiO2 was a limiting factor.

Facile Fabrication of Tunable Bi2O3 Self-Assembly and Its Visible Light Photocatalytic Activity

In this article, we report the fabrication of various morphological bismuth oxides (α-Bi2O3) by a self-assembly process using bismuth oxalates as precursors. Barlike Bi2(C2O4)3·7H2O and microrod-like (BiOHC2O4)2·H2O were synthesized by using bismuth nitrate with oxalic acid in a simple mixing and hydrothermal process and are hereafter referred to as bismuth oxalate-1 and bismuth oxalate-2, respectively. The thermal decomposition of bismuth oxalate-2 at 300 and 400 °C for 2 h yields aggregate-free honeycomb brushlike and wormlike morphological Bi2O3, respectively. We first report the formation of both the above-mentioned novel morphological bismuth oxides. However, the decomposition of bismuth oxalate-1 results in microspheres with bundle-shaped particles and wormlike bundles with microflower morphologies at 300 and 400 °C, respectively. The influences of hydrothermal temperature, time, and bismuth precursor on the formation of bismuth oxalate-2 were investigated. The synthesized bismuth oxalates and Bi2O3...

Preparation of Fibrous CaO Sorbent by Hydrothermal Method

Using urea and calcium chloride as precipitator and calcium source, fibrous CaCO3 precursors were prepared using hydrothermal method, then fibrous CaO sorbent was obtained by calcination. The influence of hydrothermal temperature on CO2 absorption properties was discussed. X-ray diffraction analysis showed that pure CaCO3 phase with aragonite and calcite crystal forms was obtained. Scanning electron microscopy analysis showed that the resultant CaO sorbent presented a fibrous microstructure, which inherited the morphologies of CaCO3. The absorption capacity of the resultant CaO sorbent reached 59.86%, being 76% of theoretical absorption capacity. In addition, compared with the CaO sorbent from analytical pure CaCO3, the obtained fibrous CaO-sorbent have the better cyclic absorption properties.

Preparation and Thermodynamic Study of Self-Dispersal Nano-AIOOH

Abstracts: Self-dispersal nano-AlOOH crystal powder was prepared via sol-hydrothermal crystallization and charging method, using aluminum salt and ammonium as raw materials. TEM, XRD and UV-vis absorption spectroscopy were used to study effects of the hydrothermal temperature and hydrothermal time on precursor’s crystallization and charging, the product’s dispersion property and mean particle size. Thermodynamic and dynamic analysis on the preparation process was carried out. Results and analysis suggested that the influence of hydrothermal temperature on product’s dispersion property was larger than that of hydrothermal time. Modification and control of the hydrothermal conditions could make AlOOH crystal grow along the C-axis and form needle-like particle with lowered surface energy and improved dispersion property. Thermodynamic analysis suggested that the phase transition from Al2O3nH2O into crystalline AlOOH could spontaneously occur at a temperature within the range of 100oC - 150oC. In the preparation of AlOOH crystal powder via the hydrothermal crystallization and charging composite dispersion method, the reaction condition was mild with a strong thermodynamic driving force and small activation energy of 24.11kJ/mol.

Hydrothermal synthesis of protective coating on magnesium alloy using de-ionized water

High corrosion rate is the “Achilles' heel” of magnesium and its alloys, which has severely limited their applications. Coating on these kinds of materials is an effective way to overcome this weakness. Protective coatings were successfully synthesized on AZ31 magnesium alloy by the hydrothermal method with de-ionized water as mineralizer in this paper. The structure, morphology, and composition of the coatings were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive spectroscopy (EDS), respectively. Potentiodynamic polarization tests and immersion tests for 7 and 14days in 3.5wt.% NaCl aqueous solution at room temperature were conducted to evaluate anti-corrosion abilities of coatings. The influences of hydrothermal temperature and time on the thickness of the coating and corrosion resistance were investigated. The results show that the coatings are uniform and compact, composed of hexagonal magnesium hydroxide (Mg(OH)2) and a spot of monoclinic aluminum magnesium hydroxide (Mg2Al(OH)7). The thickness of coating varied from 2.2μm to 27.2μm, increasing with the hydrothermal temperature and time. Polarization curves and results of immersion tests of coated and uncoated AZ31 substrates demonstrate that coatings can improve the corrosion resistance effectively and the corrosion resistances are mainly increased with the thicknesses of the coatings and increased with hydrothermal temperature if the thicknesses are very close to each other. The static water contact angles of the coatings are all less than 13.5°, whereas that of the substrate is 40.5°, indicating that the coatings are highly hydrophilic. Tape test further verifies that there is a strong adhesion between the coating and the substrate.

Controlled Fabrication of α-GaOOH and α-Ga2O3 Self-Assembly and Its Superior Photocatalytic Activity

In this article, we report the fabrication of gallium oxide (α-Ga2O3) microspheres (GOMs) by a self-assembly process. Gallium nitrate with oxalic acid in a hydrothermal process results in α-GaOOH, which was further converted into gallium oxide by calcinations at 450 °C for 3 h. We first report the formation of various morphological α-GaOOH by using the above-mentioned methodology. The influence of hydrothermal temperature and time on the crystal structure and its morphology was studied, and the results indicated that hydrothermal temperature played an important role in the final morphology of α-GaOOH. The flower-like α-GaOOH formed at 175 °C is converted into rodlike α-Ga2O3 after calcination at 450 °C, and the α-GaOOH microsphere and microrod formed at 200 and 225 °C retained their morphology during the calcination process, respectively. The synthesized α-GaOOH and α-Ga2O3 were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission ...

Selective synthesis and growth mechanism of CeVO 4 nanoparticals via hydrothermal method

Selective-controlled structure and shape of CeVO 4 nanocrystals were successfully synthesized via a hydrothermal method from Na 3VO 4·12H 2O and Ce(NO 3) 3·6H 2O. The resulting products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The influence of hydrothermal temperature, precursor solution concentration on the crystal and morphology of products were further studied. The results showed that the as-synthesized products exhibited pure single-crystal CeVO 4 nanoparticles with tetragonal structure. The hydrothermal temperature and precursor solution concentration had important effects on the formation of CeVO 4 nanoparticles. Furthermore, the growth mechanism of CeVO 4 nanoparticles was explained with Ostwald ripening mechanism.

The influence of hydrothermal temperature on SnO 2 nanorod formation

SnO 2 nanorods were successfully prepared by a hydrothermal method using tin chloride, liquid ammonia, sodium hydroxide and cetyltrimethyl ammonium bromide (CTAB) as starting materials. Structural properties and surface morphologies of the SnO 2 nanorods were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). Experimental results showed that the diameter of the nanorods is in the range of 100–300 nm with a length of several micrometers. The hydrothermal treatment temperature was found to play an important role in determining the morphology and diameter of the SnO 2 nanorods. Possible growth mechanisms of SnO 2 nanorods were proposed.

Influence of hydrothermal temperature on structure and microstructure of boehmite

Boehmites (Al 2O 3· xH 2O) were hydrothermally prepared from aluminum alkoxide. The effect of temperature on preparation was studied in the range of 100–180 °C. The XRD analysis shows that with temperature increasing, the transformation of pseudo-boehmite into well-crystallized boehmite takes place. The micro-morphologies change also from irregular clew to thin cubic platelets. From the mass loss of the samples prepared at different temperatures, the value of x is estimated to vary between 1.06 and 1.67. γ-Al 2O 3 obtained by subsequent calcination of boehmite at 600 °C is also characterized by XRD and its morphology remains unchanged.

Influence of hydrothermal temperature on hydroxyapatite coating transformed from monetite on HT-C/C composites by induction heating method

Hydrothermal post-treatment was used to convert monetite coating fabricated by induction heating method on H 2O 2 treated C/C (HT-C/C) composites to an adherent HA coating. The monetite coatings were hydrothermally treated for 4 h at 373 K, 403 K, 423 K, and 453 K in a 50 mL autoclave. After hydrothermal post-treatment, the structure, morphology and the chemical composition of these HA coatings were characterized with XRD, FTIR SEM and EDS. A scratch test was conducted to measure the strength of the adhesion of the coatings to the HT-C/C substrate. The results showed that the degree of crystallinity and the Ca/P ratio of the HA coatings increased with increasing hydrothermal temperature. The submicron-level morphology and adhesion of the HA coatings were highly affected by the hydrothermal temperature. From the results, it can be suggested that 423 K was the best hydrothermal treatment temperature for the HA coatings which were transformed from the monetite coatings produced by the induction heating method on HT-C/C composites.

Selective synthesis and characterization of flower-like ZnO microstructures via a facile hydrothermal route

Flower-like ZnO microstructures with an average diameter of 1 μm assembled from nanorods have been successfully synthesized via a facile hydrothermal method under mild conditions using aqueous zinc nitrate as zinc source, sodium hydroxide as precipitating reagent and triethylamine (TEA) as both alkaline and complexing reagent. The influences of hydrothermal temperature, reaction time, and concentration of NaOH and TEA on the morphology and size of final products have been carefully investigated. The phase structures, morphologies and optical properties of the final products were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscope (HRTEM), and photoluminescence (PL) and UV–vis absorption spectrometer. The probable formation mechanism was also proposed based on the experimental results. The photoluminescence characterization of flower-like ZnO microstructures exhibited a blue emission at 465 nm and a broad visible emission in green region and a red-shift was observed in their UV–vis absorption spectrum.

Template-free synthesis of molybdenum oxide-based hierarchical microstructures at low temperatures

Molybdenum oxide-based hierarchical microstructures assembled radially by anisotropic nanostructures (nanoplates/microprisms/nanorods) have been synthesized at low temperatures for the first time via a facile template-free hydrothermal approach. The influence of hydrothermal temperature, time, concentration of the peroxomolybdic acid solution, and additives on the morphology of products has been investigated. It has been found that the morphology of urchin-shaped microstructures of peroxo-modified molybdenum oxide hydrates can be controlled in the temperature range of 65–75 °C. The as-synthesized uniform microstructures, which are collected from the 0.9 mol/L molybdenum solutions after 14 h at 75 °C, are 35–40 μm in diameter, and they are constructed by nanoscale blocks of 300–400 nm in width and ∼190 nm in thickness. The dimensions of microstructures and their building blocks are dramatically magnified when the molybdenum concentration is reduced, while those dimensions can be efficiently decreased by adding small quantities of HNO 3 or LiNO 3 into the precursor solution. By moderate calcination, α-MoO 3 with a hierarchical microstructure can be achieved. The possible formation mechanism of urchin-shaped microstructures is discussed using the results of UV–visible spectroscopy and electron microscopy.

Synthesis of flower-like CuO nanostructures as a sensitive sensor for catalysis

The flower-like CuO nanostructures were hydrothermally synthesized without using any template. The influences of hydrothermal temperature and time on the growth of nanostructures were investigated. The samples were characterized by means of scanning electron microscope (SEM), X-ray powder diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), selected area electron diffraction (ED), and N2 adsorption isotherm. Interestingly, these architectures are made of three-order structures. The formation mechanism of the flower-like CuO was proposed and explained. Furthermore, the chemiluminescence (CL) and catalysis properties of the flower-like CuO were also investigated. The flower-like nanostructures showed the high-CL intensities and reactive activities for CO oxidation. The flower-like CuO can be used to fabricate a highly sensitive CL detector. This CL mode is a rapid and effective method for the selection of new catalysts from thousands of materials.

Preparation of Hydroxyapatite Coatings on Carbon/Carbon Composites by a Hydrothermal Electrodeposition Process

Hydroxyapatite (HAp) coatings were prepared by a hydrothermal electrodeposition method on Carbon/carbon (C/C) composites. The as-prepared HAp coatings were characterized by XRD and SEM analyses. The influence of hydrothermal temperature on the phase and surface microstructures of HAp coatings and the corresponding deposition kinetics were particularly investigated. Results show that with the increase of hydrothermal temperature, the crystallinity, density and homogenous of the prepared HAp coatings are improved. The deposition rate also increases with the increase of hydrothermal temperature. The deposition activation energy of HAp coatings by the hydrothermal electrodeposition process is calculated to be 25.89 kJ/mol.

One-Step, Low-Temperature Route for the Preparation of Spinel LiMn2O4 as a Cathode Material for Rechargeable Lithium Batteries

A new low-temperature synthetic route has been developed and demonstrated for the production of spinel as a cathode material for Li-ion batteries. The process involves the insertion of lithium into electrolytic manganese dioxide with glucose as a mild reductant in an autoclave. The material resulting from hydrothermal treatment is a spinel-structured with reasonable crystallinity. It exhibits promising electrochemical behavior in nonaqueous liquid electrolyte. The influence of hydrothermal temperature and the effect of glucose in determining the final structural integrity and electrochemical performance have also been systemically explored. Furthermore, the capacity degradation of low-temperature synthesized spinels was studied by cyclic voltammetry and X-ray diffraction. This capacity fading can be mainly attributed to the factors of structural degradation and loss of active materials.