Influence Of Hydrothermal Time Research Articles

Influence of hydrothermal time on anti-corrosion property of slippery liquid-infused porous surfaces on AZ31 magnesium alloys

To enhance anti-corrosion property of AZ31 magnesium alloys, slippery liquid-infused porous surfaces (SLIPSs) were prepared on benzoate-intercalated Mg-Al layered double hydroxides (LDHs). The typical morphology of SLIPSs was determined using a scanning electron microscope, and the successful loading of benzoate ions was confirmed by an X-ray diffractometer (XRD). Especially, this work focused on revealing how hydrothermal time affected the resistance to corrosion of SLIPSs. The electrochemical results indicated that when the hydrothermal duration was 24 h, the developed SLIPS exhibited remarkably improved corrosion resistance accompanied by the lowest corrosion current density of 2.5 × 10−3 μA cm−2. Furthermore, the results of immersion test demonstrated the superiority of SLIPSs in anti-corrosion durability. Based on the obtained results, the prepared SLIPSs can be promising candidates for the improvement in anti-corrosion performance of magnesium alloys.

Influence of hydrothermal time on the formation of SAPO-56 structure and its catalytic activity of removal NOx by NH3-SCR with Cu/SAPO-56

The SAPO-56 molecular sieve material was prepared under hydrothermal conditions at 200 °C with different hydrothermal times using precursors including Al(OH)3, LUDOX AS-30, H3PO4, and TMHD (N,N,N′,N′-tetramethyl-hexane-1,6-diamine) as an organic structure-directing agent. The samples were characterized by X-ray diffraction, field emission scanning electron microscopes, Energy-dispersive X-ray spectroscopy, NH3 temperature - programmed desorption, N2 adsorption-desorption, and UV-Vis Diffuse Reflectance Spectroscopy methods. Electron paramagnetic resonance technique was applied to determine isolated Cu2+ ions in the framework. Although materials shared the same AFX framework structure, they owned different physicochemical properties, especially in terms of crystal size, surface area, and acidity. Next, the catalytic activity of removal NOx of Cu/SAPO-56 and Cu/ZSM-5 using commercial ZSM-5 as support with the loading of 3 wt%Cu synthesized by aqueous ion-exchange method was assessed in the selective catalytic reduction with NH3.

Hierarchical CuCo2S4 Nanoflake Arrays Grown on Carbon Cloth: A Remarkable Bifunctional Electrocatalyst for Overall Water Splitting

AbstractFabricating self‐supporting electrocatalysts with double functions for overall water splitting is a promising strategy for clean energy generation. Herein, spinel‐based CuCo2S4 nanoflakes were grown vertically on carbon cloth (CC) substrate to obtain hierarchical self‐supporting CuCo2S4/CC electrocatalysts through a hydrothermal process. The influence of hydrothermal time on the surface morphology and electrocatalytic properties of the CuCo2S4/CC was investigated. The rational synthetic approach can significantly reduce the diffusion path and promote the transfer of charge. As a result, the optimized CuCo2S4/CC exhibits a significantly higher electrocatalytic activity than the control single metal sulfide catalysts (CoS1.097/CC and CuS/CC) in 1.0 M KOH solution, and relatively overpotentials of 204 and 280 mV are demanded to generate a current density of 10 mA cm−2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. The significantly enhanced electrocatalytic activity benefits from the synergetic effect of the fast charge transport and abundant catalytic active sites. Moreover, in an overall water splitting system, a two‐electrode setup constructed using CuCo2S4/CC as both cathode and anode shows a low voltage of 1.58 V at 10 mA cm−2 and high durability. This study provides a rational strategy for improving the overall water splitting performance by constructing self‐supporting spinel‐based catalysts.

Construction of CoMoO4@Ni3S2 core-shell heterostructures nanorod arrays for high-performance supercapacitors

The core-shell CoMoO4 nanorods@Ni3S2 nanosheets (CMO@NS) for supercapacitor were prepared by a facile two-step hydrothermal process accompanying with annealing treatment. The influence of hydrothermal time on structures and electrochemical properties was studied in detail. Benefiting from the synergism-enhanced action of CoMoO4 and Ni3S2 and the novel core-shell heterostructure of the composite, the prepared electrode exhibits excellent electrochemical performance. CMO@NS employed as positive electrode for supercapacitor exhibits excellent areal specific capacitance (11.02 F cm−2 at 5 mA cm−2), exceptional rate performance (70.8% retention, even increasing the current density to 30 mA cm−2) and enhanced cycle performance (57.7% retention rate after 3000 cycles). Furthermore, an asymmetric supercapacitor device was fabricated, which achieves an ultra-high energy density of 0.412 mWh cm−2 at the power density of 4 mW cm−2 and a great cycle life with 81.25% capacitance retention over 3000 cycles. Thus, the core-shell CMO@NS could be a hopeful candidate for practical supercapacitor electrode materials.

Synthesis TiO2 -SiO2 Composites Using The Method Sol-Gel-Hydrothermal

Titanium dioxide (TiO2) is a transition metal oxide material which has been researched extensively and can be used for various applications. In this research, synthesis of TiO2 -SiO2 using TTIP and TEOS precursor. Research aims to determine the characteristics of composite materials generated based on the influence of hydrothermal time and precursor composition. Synthesis is done by variation of hydrothermal time (4 hours, 8 hours, 18 hours, 24 hours and without hydrothermal) and TEOS precursor composition variation (1:1, 1:2 and 2:1). Synthesis is made by dissolving the two precursors through the sol-gel-hydrothermal method and continued with the calcination process. Characterization using FT-IR showed a bonding Ti-O-Si at a wavelength of 950 cm-1 . This bond is formed from the interaction between TiO2 and SiO2 which indicates the success of the synthesis. The XRD characterization results show formed of a peak at 2θ° the range 25° for all composites. The results of the dr-uv characterization on the TiO2 -SiO2 composite comparison of 2:1 showed absorption at 387 nm and obtained band gap energy of 3,20 eV. Based on the data obtained it can be concluded that synthesis of TiO2-SiO2 hydrothermally obtained the optimum time 24 hours and the best comparison is contained in the composition 2:1, which produces an anatase structure with a crystal size of 15,899 nm, so that the resulting composite can be used as a photocatalyst. Keywords: Hydrothermal, Sol-gel, TiO2 -SiO2.

Influence of hydrothermal time on structural properties of ZnO nanorods grown on spin-coated ZnO seeding layer

Most of the recent nanodevices are fabricated by using high-efficiency deposition methods and patterned via high-resolution lithography. However, there are drawbacks for the methods including small-scale product, high cost consumption, and multi-step processes. To reduce these disadvantages, this work focuses on the usage of sol-gel synthesis and spin coating method to fabricate ZnO seed layer onto glass substrates. All of substrates were patterned by conventional UV photolithography at exposure time of 7 seconds, then ZnO nanorods were hydrothermally grown at 90°C for 2, 3, and 4 hours, respectively. All of samples were characterised by scanning electron microscope (SEM) which revealed the sharp and smooth tip hexagonal structure at different hydrothermal time. The evolution of the nanorods’ growth was investigated, and the diameters were estimated. Moreover, crystal quality was revealed by x-ray diffractograms. It was clear that the domination of c-axis plane occurred for all the samples associates with the crystallinity of the nanostructures. This indicated escalating of the non-monodirectional growth plane in increasing nanorods’ diameter as the nanorods are polycrystal. Furthermore, the optical properties of the samples were observed by UV-visible spectroscopy and photoluminescence technique (PL). UV-visible spectroscopic data showed diminishing of the energy band gap when the diameter grew up. PL data revealed the reduction of the intensity ratio at near-band-edge peak versus oxygen vacancy peak. This information pointed to the decreasing trend of the crystal quality with escalating growth time.

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B2O3·H2O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn4B2O7·H2O (4ZnO·B2O3·H2O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B2O3·H2O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B2O3·H2O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm−2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm−2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm−2 after 10 h for direct comparison with the coated samples.

Novel synthesis of AB-type carbonated hydroxyapatite hierarchical microstructures with sustained drug delivery properties

In this study, AB-type carbonated hydroxyapatite (CHAp) nanosheet-assembled hollow microstructures were rapidly synthesized via a hydrothermal process without sintering. Urea was employed as both a pH adjusting agent and a CO32− source during hydrothermal reaction. The influence of hydrothermal time on the final morphologies of the products was systematically investigated. The as-prepared CHAp hollow microstructures with a diameter of about 3–4 μm consist of numerous radially oriented CHAp nanosheets as building units with an average thickness of about 10 nm. The morphology of the product can vary from a hollow microstructure to a solid dandelion-like structure with increasing hydrothermal time. Possible mechanisms for the formation of a nanosheet-assembled CHAp hollow microstructure and a solid dandelion-like microstructure in the presence of both urea and ethylenediaminetetraacetic acid (EDTA) are illustrated. Moreover, the as-prepared CHAp hollow microstructures exhibit a high drug loading capacity and sustained drug release properties.

Hydrothermal synthesis and up-conversion luminescence properties of NaYF4:Yb3+,Tm3+ phosphors

An up-conversion luminescent material, NaYF4 doped with rare-earth (RE), possessed a high luminescence efficiency and excellent stability. As described herein, a series of hexagonal nano-prismatic NaYF4:Yb3+,Tm3+ up-conversion phosphors had successfully been synthesized through mild hydrothermal method. The influence of hydrothermal time, the content of sodium tartrate, activator, sensitizer and ammonium fluoride on the luminescence properties of the target product were systematically investigated by means of single factor experiments. Based on the single factor experiments, the orthogonal method was used to obtain the optimal preparation conditions of the sodium tartrate/RE mole ratio, the sensitizer Yb3+ ions content, the NH4F/RE mole ratio, and the hydrothermal time which were 0.5, 23%, 11, 13 h, respectively. The fluorescent emission spectra analysis results showed that the strongest blue up-conversion luminescence emission peaks (1G4→3H6 transition of Tm3+ ion) of the NaYF4:Yb3+,Tm3+ phosphors using sodium tartrate as complexing agent was located at 477 nm under 980 nm near infrared (NIR) laser diode excitation. Finally the target products using different complexing agent were prepared at optimum preparation condition, and characterized by X-ray diffraction, scanning electron microscope. The crystal structure of products using tartaric acid and citric acid as complexing agent was hexagonal, consisting of spheres with 100 nm diameter.

Hydrothermal Synthesis of Hydroxyapatite Urchins and its Drug Release Property

Hydroxyapatite (HAP) urchins were synthesized by a facile hydrothermal method using calcium nitrate, ammonium dihydrogen phosphate, diamine tetraacetic acid disodium salt as complexing agent and ethonalamine as alkaline source. The influence of hydrothermal time on crystallinity and morphology of HAP have been investigated. The results indicate that well-crystallized HAP urchins can be synthesized at 180°C for 24h. SEM images show a large area of urchin-like microspheres consisted of a number of ribbons with lengths ranging from 2 to 5μm. Based on XRD and SEM results, the formation mechanism of HAP crystals has been discussed. A typical anti-inflammatory drug, ibuprofen, was used for drug loading, and the release behaviors of ibuprofen in a simulated body fluid (SBF) were studied. The results indicate that HAP urchins showed a favorable sustained release property for ibuprofen.