Influence of reaction temperature, proportions of iron, cobalt and KOH on the CoFe2O4 synthesis by hydrothermal method assisted by microwave heating

First, (K,Na)NbO3 (abbreviated as KNN) powders were synthesized by microwave hydrothermal method using Nb2O5, NaOH and KOH as raw materials. The effects of NaOH/KOH mole ratio and reaction temperature on the structure of KNN powders were studied systematically. Near spherical KNN powders of about 800 nm in diameter can be obtained at the optimized processing parameters as follows: NaOH/KOH mole ratio was 1.40/4.60, reaction temperature was 200 °C. Second, the ceramics were successfully prepared from the microwave hydrothermal synthesized KNN powders under 1090 °C for 2 h. This ceramic sample showed the enhanced piezoelectric properties such as piezoelectric constant d33=142 pC/N and planar electromechanical coupling coefficient kp=38%, in addition to other good properties as relative dielectric constant εr=426, Curie temperature Tc=410 °C, remnant polarization Pr=17.45μC/cm2 and coercive field Ec=1.41 kV/mm, indicating that microwave hydrothermal method can improve the properties of KNN ceramics high efficiently.

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Investigation of Bioactive Glass-Ceramic 60SiO2-30CaO-10P2O5 Prepared by Hydrothermal Method

Advances in Materials Science and Engineering ◽

10.1155/2019/1528326 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8

Author(s):

Vuong Xuan Bui ◽

Mai Quang Vo ◽

Tien Anh Nguyen ◽

Hoa Thi Bui

Keyword(s):

Bioactive Glass ◽

Hydrothermal Method ◽

Reaction Temperature ◽

Hydrothermal Reaction ◽

Glass Ceramics ◽

Degree Of Crystallinity ◽

Apatite Phase ◽

Powder Samples ◽

Sbf Solution ◽

The Degree Of Crystallinity

Bioactive glass-ceramics (BGCs) with the composition of 60SiO2-30CaO-10P2O5 (wt. %) have been synthesized by the hydrothermal method. The BGC samples were prepared at two reaction temperatures of 150 and 220°C, named BGC-150 and BGC-220. The XRD and FTIR analyses highlighted that the degree of crystallinity of BGCs increased linearly with hydrothermal reaction temperature. FE-SEM and TEM results indicated that the surface of BGC samples is covered by the nanosized particles which grow into larger sizes as a function of reaction temperature. The bioactivity of BGCs was investigated by the immersion of powder samples in the SBF solution. The results confirmed the dissolution and the interaction of BGC samples in the SBF solution which led to the formation of a new apatite phase on their surface.

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Temperature-controlled hydrothermal synthesis of γ-MnOOH, Mn3O4 and MnCO3 on a carbon cloth for supercapacitor applications

CrystEngComm ◽

10.1039/c9ce01732a ◽

2020 ◽

Vol 22 (23) ◽

pp. 4014-4022

Author(s):

Shujuan Meng ◽

Qiong Su ◽

Ping Zhang ◽

Wanhong Sun ◽

Yanbin Wang

Keyword(s):

Hydrothermal Synthesis ◽

Hydrothermal Method ◽

Formation Mechanism ◽

Reaction Temperature ◽

Controlled Synthesis ◽

Carbon Cloth ◽

Temperature Controlled ◽

Supercapacitor Applications

In this study, a reaction temperature-controlled synthesis of γ-MnOOH, Mn3O4 and MnCO3 (and also their mixture) on carbon cloth via a hydrothermal method is investigated, and the formation mechanism is discussed.

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The Effect of Process Conditions on the Preparation of α-Calcium Sulfate Hemihydrate from FGD Gypsum Using the Hydrothermal Method under Atmospheric Pressure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.881 ◽

2011 ◽

Vol 250-253 ◽

pp. 881-889 ◽

Cited By ~ 2

Author(s):

Xian Feng Liu ◽

Jia Hui Peng ◽

Chen Yang Zou ◽

Leng Bai ◽

Mei Li

Keyword(s):

Hydrothermal Method ◽

Reaction Temperature ◽

Salt Concentration ◽

Atmospheric Pressure ◽

Calcium Sulfate ◽

Ph Value ◽

Fgd Gypsum ◽

Rate Of Reaction ◽

Percent Conversion ◽

Calcium Sulfate Hemihydrate

This paper studies the laws of crystal growth, percent conversion and the rate of reaction of α-calcium sulfate hemihydrate from FGD gypsum under different conditions using the hydrothermal method under atmospheric pressure. The crystal morphology was observed by using SEM, polarizing microscope profile, and percent conversion and the rate of reaction were obtained by assaying crystal water content and calculating. The results showed, (1) with the increase of reaction temperature, the dehydration rate increased and the formed α-calcium sulfate hemihydrate crystal had a larger particle size; (2) with the increase of salt concentration or slurry concentration, the formed α-calcium sulfate hemihydrate crystal was smaller, percent conversion and the rate of reaction was nearly unchanged; (3) with the increase of pH value of solution, the rate of reaction increased and percent conversion was nearly unchanged, and with pH value ranging from 5 to 7 the formed α-calcium sulfate hemihydrate crystal was crassitude. In conclusion, the perfect technological parameters were as follows: reaction temperature ranging from 95°C to 100°C, salt concentration ranging from 15% to 20%, slurry concentration ranging from 15% to 20%, pH value ranging from 5 to 7, and reaction time not exceeding 90min.

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Synthesis of single-crystalline Pb(Zr0.52Ti0.48)O3 nanocrystals by hydrothermal method

Materials Science-Poland ◽

10.2478/msp-2019-0059 ◽

2019 ◽

Vol 37 (3) ◽

pp. 473-481

Author(s):

Chunyu Deng ◽

Chaoran Qin ◽

Xinyi Li ◽

Shaoqing Li ◽

Zhixiong Huang ◽

...

Keyword(s):

Grain Size ◽

Hydrothermal Method ◽

Reaction Temperature ◽

Single Phase ◽

Reaction Times ◽

Nucleation And Growth ◽

Flexible Substrates ◽

Single Crystalline ◽

Different Temperatures ◽

20 Nm

AbstractPbZr0.52Ti0.48O3 nanocrystals were synthesized by a hydrothermal method. The effect of NaOH concentration, reaction temperature and time on nucleation and growth of PbZr0.52Ti0.48O3 nanocrystals was investigated. As the 0.05 mol/L PbZr0.52Ti0.48O3 precursors were heated at 200 °C for 21 h with NaOH concentration of 0.5 mol/L, the tetragonal PbZr0.52Ti0.48O3 nanocrystals were formed, and the grain size was more than 20 nm. With increasing the NaOH concentration from 0.5 to 1.5 mol/L, the grain size of PbZr0.52Ti0.48O3 nanocrystals decreased. When the precursors were heated at different temperatures (140 °C to 200 °C) for 21 h with 1.0 mol/L NaOH, single-phase PbZr0.52Ti0.48O3 nanocrystals were obtained at 160 °C to 200 °C. With increasing the reaction temperature from 160 °C to 200 °C, the grains size of PbZr0.52Ti0.48O3 nanocrystals increased from 5 nm to 9 nm. When the precursors were heated at 160 °C in different reaction times from 6 h to 21 h, the evolution from amorphous to crystalline PbZr0.52Ti0.48O3 nanocrystals in correlation with the reaction time was observed. Single crystalline PbZr0.52Ti0.48O3 nanocrystals with narrow size distribution (from 5 nm to 9 nm) were synthesized by controlling the NaOH concentration, reaction temperature and time. The obtained results can find potential application in preparing PbZr0.52Ti0.48O3 thin films on flexible substrates.

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Synthesis, characterization and catalytic testing of MCM-22 derived catalysts for n-hexane cracking

Scientific Reports ◽

10.1038/s41598-020-78746-9 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Ali Ahmad ◽

Salman Raza Naqvi ◽

Muhammad Rafique ◽

Habib Nasir ◽

Ali Sarosh

Keyword(s):

Oxalic Acid ◽

Hydrothermal Method ◽

High Temperatures ◽

Reaction Temperature ◽

Catalytic Cracking ◽

Product Distribution ◽

Catalytic Performance ◽

Temperature Range ◽

Novel Materials ◽

Diffusion Limitations

AbstractLayered zeolites and their delaminated structures are novel materials that enhance the catalytic performance of catalysts by addressing diffusion limitations of the reactant molecules. n-Hexane catalytic cracking was observed over MCM-22 layered zeolite and its derivative structures over the temperature range of 450–650 °C for the production of olefins. MCM-22, H-MCM-22, and ITQ-2 zeolites were prepared by the hydrothermal method. Oxalic acid was used as a dealuminating reagent to obtain H-MCM-22 with various Si/Al ratios ranging from 09–65. The prepared samples were characterized by XRD, SEM, TGA, and BET. The cracking of n-hexane was carried out by Pyro/GC–MS. It was observed that the selectivity for olefins was improved by increasing the Si/Al ratio. H-MCM-22–10% produced the highest relative olefinic concentration of 68% as compared to other dealuminated structures. Moreover, the product distribution showed that higher reaction temperature is favorable to produce more olefins. Furthermore, a comparison between ITQ-2 and MCM-22 derived structures showed that ITQ-2 is more favorable for olefins production at high temperatures. The concentration of relative olefins was increased up to 80% over ITQ-2 at 650 °C.

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β-Ni(OH)2 Nanospheres Synthesized via the Easy Hydrothermal Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.510.575 ◽

2012 ◽

Vol 510 ◽

pp. 575-578

Author(s):

Xiao Ming Fu

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Hydrothermal Method ◽

Reaction Temperature ◽

Nickel Nitrate ◽

X Ray Diffraction ◽

Ammonia Water ◽

X Ray ◽

Scanning Electron

β-Ni (OH)2nanospheres have been successfully synthesized with nickel nitrate as nickel source and stronger ammonia water as precipitant by the hydrothermal method. The phase and the morphologies of the samples have been characterized and analyzed by X-ray diffraction (XRD) and Scanning electron microscope (SEM). XRD shows that the phase of the samples isβ-Ni (OH)2. SEM confirms that the increase of the reaction temperature is propitious to the synthesis ofβ-Ni (OH)2nanospheres, which are synthesized at at 180 °C for 48 h with pH=9 by the hydrothermal method.

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