Hydrothermal Annealing Research Articles

In-situ formation of α-Co(OH)2 nanosheet arrays on magnesium cobaltate nanowires for hybrid supercapacitors with enhanced electrochemical performance

In this work, the MgCo2O4@α-Co(OH)2 core–shell structure (MgCo2O4@α-Co(OH)2/NF) on foam nickel was prepared using hydrothermal annealing and chemical bath deposition processes to form a supercapacitor positive electrode. MgCo2O4@α-Co(OH)2/NF-2 composite material, with a deposition time of 20 min in a chemical bath, showed a specific capacitance of 1634.8 F g−1 at 1 A g−1, a long cycle stability of 89.4% (in 10,000 cycles) and a rate performance of 78.29%, with excellent electrochemical impedance performance (Rs ≈ 0.507 Ω). The MgCo2O4@α-Co(OH)2/NF-2//AC asymmetric supercapacitors (ASCs) showed a specific capacitance of 185.46 F g−1 at 1 A g−1, with a good long-cycle stability of 91.7% preservation rate after 10,000 cycles. At a power density of 773.19 W kg−1, the energy density is high (65.94 Wh kg−1). We demonstrated that three prepared ASCs devices can produce a diode with a rated voltage of 3 V that continues to emit light for 10 min. This study shows that the MgCo2O4@α-Co(OH)2/NF-2 electrode can be used as a positive electrode for high-efficiency energy storage devices.

The Improvement of Bonding Strength of W/Cu Joints via Nano-Treatment of the W Surface

W/Cu joining is key for the fabrication of plasma-facing compounds of fusion reactors. In this work, W and Cu are joined through three steps: (1) hydrothermal treatment and reduction annealing (i.e., nano-treatment), (2) Cu plating and annealing in a pure H2 atmosphere, and (3) W/Cu bonding at 980 °C for 3 h. After nano-treatment, nanosheets structure can be found on the W substrate surface. The tensile strength of the W/Cu joint prepared via nano-treatment reaches as high as approximately 93 MPa, which increases by about 60% compared with the one without nano-treatment. The microhardness curves exhibited continuous variations along the W/Cu interface. The TEM images show that the W/Cu interface is compact without any cracks or voids. This work may also be applied for enhancing bonding strength in other immiscible materials.

Zinc oxide nanonets with hierarchical crystalline nodes: High-performance ethanol sensors enhanced by grain boundaries

Researchers commonly enhance the sensitivity of gas sensing nanomaterials by increasing the effective active area. It would be more straightforward to instead optimize the grain boundaries. In this work, Zn4CO3(OH)6·H2O was synthesized as a precursor to ZnO via a facile hydrothermal process and annealing, respectively. ZnO nanonets of hierarchical crystalline nodes with abundant grain boundaries was prepared. The nanonets exhibited an ultra-sensitive response value of 398, and a fast response time (4 s of exposure to 100 ppm ethanol), compared with traditional nanosheets. The sensing enhancement as per the grain boundary was modeled and experiments confirmed the model. Microstructural and microscopic analyses indicated that the sensitivity of the nanonets mainly is attributable to the abundant grain boundaries with lots of hierarchical crystalline nodes. The high-sensitive response and fast response time toward ethanol by the ZnO nanonets is considered to derive from the enhancement effect of grain boundaries in hierarchical crystalline nodes, which creates the additional depletion layers from abundant oxygen vacancies led to a substantial change in the surface potential, referring to the difference between in-air versus in-ethanol. The proposed high-performance sensor is inexpensive to fabricate, straightforward to synthesize, and advantageous for practical use.

Physicochemical properties and in vitro digestibility of hydrothermal treated Chinese yam (Dioscorea opposita Thunb.) starch and flour

The objective of this study was to investigate the effects of hydrothermal treatments (heat-moisture treatment (HMT) and annealing (ANN)) on the physicochemical properties and in vitro digestibility of yam starch and yam flour. Hydrothermal treatments decreased the pasting properties of yam starch and yam flour. Compared with yam starch, HMT significantly (p < 0.05) reduced the pasting viscosities of yam flour. Both HMT and ANN caused an increase of the gelatinization temperatures (To, Tp, and Tc) and a decrease of enthalpy (△H). The increasement in ratio of 1047/1022 cm−1 and 995/1022 cm−1 suggested that HMT and ANN resulted in an increase in short-range order. The crystalline pattern of all samples was still A-type, and HMT yam starch exhibited higher crystallinity (26.20%). The most significant inhibition of in vitro digestibility was found in HMT yam flour, with slowly digestible starch and resistant starch contents increasing by 3.73% and 4.40%, respectively. Hydrothermal treatments made the no-starch ingredients in yam flour agglomerate and adhere to starch granules. Confocal laser scanning microscopy showed that the starch being coated or embedded by protein was a possible reason for the differences in physicochemical properties and in vitro digestibility between yam starch and yam flour.

MgCo2O4@NiMn layered double hydroxide core-shell nanocomposites on nickel foam as superior electrode for all-solid-state asymmetric supercapacitors

In this work, MgCo2O4@NiMn layered double hydroxide (LDH) core-shell structured nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF is synthesized first via a hydrothermal reaction and annealing treatment, and then utilized to prepare MgCo2O4@NiMn-LDH/NF core-shell structured nanocomposites via the second hydrothermal process. It is found that the MgCo2O4@NiMn-LDH/NF nanocomposite prepared from 6 h hydrothermal reaction (MC@NM-LDH-2) exhibits an excellent specific capacitance of 3757.2 F g−1 (at 1 A g−1). Moreover, a high capacitance retention (86.9% after 6000 cycles) and a low internal resistance (Rs) (0.565 Ω) can be achieved. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@NiMn-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo2O4@NiMn-LDH/NF-2//AC ASC shows a high energy density of 62.33 Wh kg−1 at 750 W kg−1. Meanwhile, the MgCo2O4@NiMn-LDH/NF-2//AC ASC device possesses an outstanding cycling stability of 93.7% retention of the initial capacitance after 6000 cycles and three ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these core-shell structure MgCo2O4@NiMn-LDH nanocomposites could envision huge potential application in energy storage devices.

Multilayered and hierarchical structured NiCo double hydroxide nanosheets generated on porous MgCo2O4 nanowire arrays for high performance supercapacitors

In this work, MgCo2O4@NiCo layered double hydroxide (LDH) hierarchical structure nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF is synthesized first via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@NiCo-LDH/NF hierarchical structure nanocomposites via the second hydrothermal process. It is found that the MgCo2O4@NiCo-LDH/NF nanocomposite prepared from 9 h hydrothermal reaction (MC@NC-LDH-2) exhibits an excellent specific capacitance of 5701.2 F g−1 at the current density of 1 A g−1. Moreover, a high capacitance retention (83.7% maintained after 5000 cycles) and a low internal resistance (Rs) (0.783 Ω) can be achieved. Furthermore, a quasi-solid state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@NiCo-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo2O4@NiCo-LDH/NF-2//AC ASC shows a high energy density of 89.79 Wh kg−1 at 800 W kg−1. Meanwhile, the MgCo2O4@NiCo-LDH/NF-2//AC ASC device possesses an excellent cycling stability of 89.03% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these hierarchical MgCo2O4@NiCo-LDH composites could envision huge potential application in energy storage devices.

Facile construction of MgCo2O4@CoFe layered double hydroxide core-shell nanocomposites on nickel foam for high-performance asymmetric supercapacitors

In this work, hierarchical MgCo2O4@CoFe layered double hydroxide (LDH) core-shell nanowire arrays on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF has been first synthesized via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@CoFe-LDH/NF core-shell nanocomposites via the second hydrothermal reaction. It is found that the MgCo2O4@CoFe-LDH/NF core-shell nanocomposite prepared from 3 h hydrothermal reaction (MC@CF-LDH-3) exhibits an excellent specific capacitance of 903.15 C g−1 (2007 F g−1) at the current density of 1 A g−1. Moreover, a high capacitance retention (80.2% maintained after 5000 cycles) and a low internal resistance (Rs) (0.75 Ω) can be acquired. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@CoFe-LDH/NF-3 as the positive electrode and activated carbon (AC) as the negative electrode. The as-fabricated MgCo2O4@CoFe-LDH/NF-3//AC ASC shows a high energy density of 60.82 Wh kg−1 at 725 W kg−1. Meanwhile, the MgCo2O4@CoFe-LDH/NF-3//AC ASC device possesses an excellent cycling stability of 93.6% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 8 min. Our results manifest that this hierarchical MgCo2O4@CoFe-LDH composite has huge potential application in energy storage devices.

Engineering MnO/C microsphere for enhanced lithium storage

Designing an anode material with high energy density is the crucial premise for the high-performance lithium-ions batteries (LIBs), however, it remains a formidable challenge. Hence, we synthesize microsphere-like MnO/C composite through successive hydrothermal process and annealing treatment. Benefiting from the introduction of conductive carbon, the conductivity of the as-prepared MnO/C composite can be obviously enhanced and the mechanical stress generated from the repetitive expansion/shrinkage during charge/discharge process can be effectively relieved, which can greatly facilitate the rate property and cycling stability of electrode. Therefore, the as-prepared microsphere-like MnO/C composite exhibits remarkable electrochemical performance when served as anode material for LIBs (1524.1 mAh g−1 after 150 cycles at 0.2 A g−1 and 1366.3 mAh g−1 after 250 cycles even at 1 A g−1). This work proves the great potential of microsphere-like MnO/C composite as high performance anode material for LIBs.

Experimental Evidence of CO2 Photoreduction Activity of SnO2 Nanoparticles.

Tin dioxide (SnO2 ) has intrinsic characteristics that do not favor its photocatalytic activity. However, we evidenced that surface modification can positively influence its performance for CO2 photoreduction in the gas phase. The hydroxylation of the SnO2 surface played a role in the CO2 affinity decreasing its reduction potential. The results showed that a certain selectivity for methane (CH4 ), carbon monoxide (CO), and ethylene (C2 H4 ) is related to different SnO2 hydrothermal annealing. The best performance was seen for SnO2 annealed at 150 °C, with a production of 20.4 μmol g-1 for CH4 and 16.45 μmol g-1 for CO, while for SnO2 at 200 °C the system produced more C2 H4 , probably due to a decrease of surface -OH groups.

IrO&lt;sub&gt;2&lt;/sub&gt;-Based Monolithic Electrodes for Efficient and Stable Oxygen Evolution Reaction in Acid

Monolithic electrodes for oxygen evolution reaction (OER) have been successfully synthesized by hydrothermal method. Prolonging the hydrothermal duration and subsequent annealing treatment can increase the OER activities and stabilities of the samples. The IrO2/Ti-60h@400 shows excellent performance, which requires an overpotential of 391 mV at 100 mA cm-2, and could keep good activity at 200 mA cm-2 for 40 hours in acid electrolyte.

Application of flammulina-velutipes-like CeO2/Co3O4/rGO in high-performance asymmetric supercapacitors

In this study, a novel electrode of flammulina-velutipes-like CeO2/Co3O4/rGO nanoparticles on nickel foam substrate (CCGN) was prepared by hydrothermal synthesis and annealing. Hundreds of CeO2/Co3O4/rGO nanoparticles, which are similar in shape to the flammulina velutipes, form a cluster, and thousands of the clusters grow evenly on the surface of nickel foam substrate. All clusters are kept at similar distances and this arrangement and distribution provides ample expansion/contraction space for active substances during charging/discharging. The specific capacity of CCGN electrode reached 1606.6 F g−1 (964.0 C g−1) at the current density of 1 A g−1. In particular, CCGN//activated carbon (AC) asymmetric supercapacitors showed excellent power density and energy density (8000 W kg−1 at 47.6 Wh kg−1) when the voltage window was 1.6 V. And under the condition of 10 A g−1 current density, the capacitance retention rate is still extremely high 96.4% after 10,000 continuous charge and discharge tests. These remarkable features demonstrate the potential of CCGN electrodes for use in supercapacitors.

Morphology Effect of 1D ZnO Nanostructures Designed by Hydrothermal and Thermal Annealing for Fast Ultraviolet Photodetector Applications

ZnO nanorods are grown on a ZnO seed layer using the hydrothermal method and subsequently annealed at temperatures of 400–800 °C. The ZnO nanorods annealed at 400 °C exhibit a morphology similar to that of the unannealed ZnO nanorods. However, the tips of the ZnO nanorods gradually become rounded and their density and diameter increase with an increase in the annealing temperature. The intensity of the near‐band‐edge emission increases gradually with an increase in the annealing temperature from 400 to 600 °C but decreases sharply in the case of nanorods annealed at 800 °C. With respect to the deep‐level emissions, broad yellow, orange, and green emissions are observed. Further, the low‐temperature photoluminescence spectrum measured at 12 K of the ZnO nanorods annealed at 600 °C contains a donor‐bound exciton emission, as well as emissions related to the donor–acceptor pair (DAP) transition and the first‐order and second‐order longitudinal optical phonon replicas of the DAP transition. Finally, with respect to the photoresponse, the dark current and photocurrent of the nanorods decrease and their photosensitivity increases with the increase in the annealing temperature.

Construction of Ti3C2 MXene@C@SnS with layered rock stratum structure for high-performance lithium storage

Tin sulfide (SnS) possesses high theoretical capacity and make it a very potential anode material for lithium-ion batteries. Nevertheless, the poor electrical conductivity of SnS is prone to collapse during lithiation/de-lithiation. Herein, Ti3C2 MXene@C@SnS hybrids with layered rock stratum structure are prepared as an anode electrode for lithium ion batteries through hydrothermal and subsequent annealing. The hybrids integrate large specific surface area and porosity, and accelerate electron/ion transfer. The Ti3C2 MXene@C@SnS anode exhibits a superior capacity (1473 mA h g−1 at 0.1 A g−1), outstanding rate capability (640 mA h g−1 at 5 A g−1 and keeps 1142.2 mA h g−1 for 70 cycles returning to 0.5 A g−1 again) and excellent long-cycle stability (1050 mA h g−1 at 1 A g−1 over 350 cycles). Kinetic analysis reveals that the excellent rate capability is controlled by surface pseudocapacitance behavior at high current. This result indicates that Ti3C2 MXene@C@SnS can be potentially applied in the field of lithium storage.

Low Ni-doped Co3O4 porous nanoplates for enhanced hydrogen and oxygen evolution reaction

In this paper, low Ni-doped Co3O4 (Ni: 2 wt%, 4 wt%, 6 wt% and 8 wt%) porous nanoplates are synthesized by hydrothermal method and annealing treatment. For the low Ni-doped Co3O4, X-ray diffraction (XRD) and Raman data show that the Ni ions are successfully incorporated into the Co3O4 lattices. Electrochemical measurements indicate that Co3O4 with low amount of Ni doping possesses remarkably enhanced activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. And especially, 4 wt% Ni-doped Co3O4 possesses the most efficient activity with an overpotential of 240 mV at the current density of 10 mA cm−2 for OER and 120 mV for HER in 1 M KOH than the pure Co3O4 and other Ni-doped Co3O4 samples. Our study suggests that the low doping would have a great potential in rational design of spinel oxides toward highly efficient electrocatalysis.

Optimization and gas sensing properties of Au nanoparticle modified α-Fe2O3 nanodisk structures for highly sensitive acetone detection

Au nanoparticle (Au NP) modified α-Fe2O3 nanodisk structures are obtained using a facile hydrothermal method and annealing based surface treatment.

Two-dimensional NiSe2 nanosheets on carbon fiber cloth for high-performance lithium-ion batteries

Recent developments of transition metal selenides as potential anode materials for lithium-ion batteries (LIBs) have attracted much attention. In this work, NiSe2 nanosheets grown on carbon fiber cloth (denoted as NiS2 nanosheets/CFC) are successfully prepared via simple hydrothermal and subsequent annealing methods. When investigated as anode for LIBs, NiSe2 nanosheets/CFC exhibits high reversible capacities of 1196 mA h g−1 after 100 cycles at 0.1 A g−1, 811 mA h g−1 after 150 cycles at 0.5 A g−1, corresponding to superior capacity retention of 94%. Besides, a high-rate capability of 682 mA h g−1 at 2 A g−1 is also achieved. The excellent electrochemical performance of NiSe2 nanosheets/CFC is mainly derived from the good electrical conductivity of carbon fiber cloth (CFC), the increased active-surface area and fast Li+ diffusion caused by the nanosheets structure with particle packing. Therefore, NiSe2 nanosheets/CFC is anticipated to be a promising anode material for flexible Li-ion batteries.

Structure and properties of bio-based polyamide 69 after treated with water under different states

The structure and properties of bio-based polyamide 69 after subjecting to water treat at room temperature and under superheated (140 °C–280 °C) condition were studied in order to get effective information about processing and treatment of polyamides in water. They were characterized by differential scanning calorimetry, small-angle x-ray scattering, Fourier transform infrared spectroscopy, and wide-angle x-ray diffraction. Water treated at room temperature exerted a swelling effect on polyamide 69, and led to a transition in the crystallization of polyamide 69 from amorphous to α crystalline form. Polyamide 69 was dissolved in superheated water at 170 °C, and at a temperature lower than the above it led to an annealing effect, resulting in an increase in the lamellar thickness, melting temperature, and crystallinity. Besides, the dominant crystal structure was transformed from γ to α crystalline form. Above 170 °C, polyamide 69 was dissolved completely, and hydrolytic degradation was more prominent especially above 240 °C, which led to the dominant γ crystalline form was severely damaged and the amide bonds of polyamide 69 cleaved gradually to produce oligomers. Therefore, this investigation can provide potential applications information on plasticization and hydrothermal annealing treatment, low temperature melting extrusion processing, and hydrolysis and recycling of polyamides.

Hierarchical holey Co9S8@S-rGO hybrid electrodes for high-performance asymmetric supercapacitors

Here we report the novel design of Co9S8 nanoparticles anchoring onto three dimensional (3D) porous sulfur-doping reduced graphene oxide network (Co9S8@S-rGO) by the facile hydrothermal reaction and heat annealing process, during which the abundant pores on the S-rGO framework and Co9S8 nanoparticles can be obtained simultaneously. This may be attributed to the Co9S8 nanoparticles as the catalyst, which can contribute to the transformation of the S atoms in rGO into S-relative gases (such as H2S or SO2), resulting in the pores-rich nanostructures. Furthermore, the holey network S-rGO matrix effectively facilitate electron/ion transport, and the Co9S8 nanoparticles intercalating in S-rGO framework can drastically reduce the agglomeration of S-rGO nanosheets and provide abundant pseudocapacitance reaction sites simultaneously. The results demonstrate that the Co9S8@S-rGO-800 electrode delivers a higher gravimetric capacitance of 348.45 F g−1 and an outstanding cycling stability of 92.6% after 5000 charge/discharge cycles at 1 A g−1. As expected, an asymmetric supercapacitor is assembled and exhibits a high energy density of 39.51 Wh kg−1 at a power density of 260 W kg−1 (23.13 Wh kg−1 at 8410 W kg−1), as well as the excellent cycling stability with 90.6% of the initial specific capacitance after 5000 cycles.

Effect of hydrothermal annealing on structure and magnetic properties of RF sputtered Mn-Zn Ferrite thin films

The Mn0.9Zn0.1Fe2O4 (MZF) films were deposited by RF-magnetron sputtering on quartz substrates in argon atmosphere at 12 mTorr of partial gas pressure using RF power of 100 W. Thickness of the as-grown MZF films were 300, 650 and 970 nm. X-ray diffraction patterns confirm the presence of single-phase cubic spinel structure in all the as-grown films. The magnetization at 300 K is found to decrease with increasing film thickness. Whereas, the magnetization at 80 K is found to increase with increasing film thickness. The strong angular dependence of M(H) plots indicate the presence of anisotropy in the as-grown MZF films. The studies on the hydrothermally heat treated film of 970 nm thickness reveals an increase in crystallite size, homogeneity and magnetization as compared to the as-grown film. The magnetic hysteresis, M(H) curve for the hydrothermally heated film show more isotropic behavior with improved magnetic properties as compared to the as-grown film. The ferromagnetic resonance data complements the magnetization results. The optical transmission studies show an increase in the bandgap of the film from 1.9 to 2.1 eV on hydrothermal annealing.

Porous Co3O4 nanowires with launching-like structure grown on its self-support for high-performance supercapacitors

Novel porous Co3O4 nanowire with launching-like structure is vertically grown on its self-support via hydrothermal method and annealing precursors of Co(CO3)0.5(OH)⋅H2O nanowires in air atmosphere. Here, crosslinked dense Co3O4 self-support is first freely grown on nickel foam. The Co3O4 nanowires are about 20 nm in diameter and composed of nanoparticles of 8 nm in diameter. Electrochemical test results show that the as-prepared Co3O4 nanowire structure has excellent specific capacitance of 2630 F/g at a current density of 1 A/g. After 5000 charge/discharge cycles, cycle stability is 98.7% at a current density of 50 A/g and 98.4% at a current density of 10 A/g.