scholarly journals Influence of molar ratio on dielectric, ferroelectric and magnetic properties of Co0.5Mg0.5Fe2O4/Ba0.85Sr0.15TiO3 composite ceramics

2019 ◽  
Vol 13 (3) ◽  
pp. 257-268
Author(s):  
Lang Bai ◽  
Rongli Gao ◽  
Qingmei Zhang ◽  
Zhiyi Xu ◽  
Zhenhua Wang ◽  
...  
Keyword(s):  
Sol Gel ◽  
Peak Position ◽  
Relaxation Peak ◽  
Molar Ratio ◽  
Composite Ceramics ◽  
Molar Ratios ◽  
Mean Grain Size ◽  
Higher Temperature ◽  
Two Phases ◽  
Two Peaks

In the present work, Co0.5Mg0.5Fe2O4/Ba0.85Sr0.15TiO3 (CMFO/BST) composite ceramics with different molar ratios (1:1, 1:2, 1:4, 1:6 and 1:8) were prepared by sol-gel method and sintered at 1150?C. The effects of molar ratio on the structure, dielectric and multiferroic properties were comparatively studied. The results indicate that all the synthesized composites mainly show bi-phase structure except slight presence of impurity phases. The surface of the specimens is relatively dense and the mean grain size is about 2 ?m. It decreases at first and then increases with the increased molar ratio. The dielectric constant shows decreased trend with increasing the molar ratio, while the dielectric loss presents the opposite behaviour. With the increase of molar ratio, the height of the relaxation peak decreases while the peak position shifts to higher temperature range. The relaxation peak evolves gradually from one to two peaks. The residual polarization increases with voltage but decreases with frequency. The maximal polarization of 1.28 ?C/cm2 is obtained in the specimen with the molar ratio of 1:8, due to the largest concentration of ferroelectric phase BST. The magnetization shows abnormal behaviour with the change in molar ratio. The largest saturation and remnant magnetization are 20.89 and 12.66 emu/g, respectively when the molar ratio is 1:2 due to the stronger interface interaction effect between the two phases.

scholarly journals Effects of molar ratio on dielectric, ferroelectric and magnetic properties of Ni0.5Zn0.5Fe2O4-BaTiO3 composite ceramics

2020 ◽  
Vol 14 (2) ◽  
pp. 91-101
Author(s):  
Xiaodong Luo ◽  
Hong Wang ◽  
Rongli Gao ◽  
Xinliang Li ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Low Frequency ◽  
Molar Ratio ◽  
Composite Ceramics ◽  
Molar Ratios ◽  
Magnetoelectric Composite ◽  
Relaxation Polarization ◽  
Two Peaks

Ni0.5Zn0.5Fe2O4-BaTiO3 (NZFO-BTO) magnetoelectric composite ceramics with different molar ratios (mNZFO:mBTO = 1:1.5, 1.5:1 and 2:1, defined as N1B1.5, N1.5B1 and N2B1, respectively) were prepared successfully by using a joint hydrothermal method and sol-gel technique and sintering at 1000 ?C. Meanwhile, the dielectric, ferroelectric and magnetic properties of the composites were investigated. The presence of bi-phase structure in the composites was verified with X-ray diffraction analyses. The scanning electron microscopy images and energy dispersion spectrum results confirmed that the bulk-like grains (2 to 5 ?m) and spherelike grains (_0.5 ?m) could be attributed to NZFO and BTO, respectively. The dielectric constant and loss increased with increasing NZFO/BTO molar ratio because the carrier concentration of NZFO is higher than that of BTO. Thus, the dielectric constant of the N2B1 ceramics is more than 7800 at low frequency of 100Hz and room temperature, while only less than 2000 for the N1B1.5 composite. Two peaks can be observed in the temperature dependence of the dielectric constant curves. One is near 120 ?C, which corresponds to the Curie temperature of BTO, while the other peak occurs at about 320 ?C, corresponding to the relaxation polarization. The remanent polarization increases with increasing the content of ferroelectric BTO. The maximum value at 1 kHz was observed for the N1B1.5 sample and it is larger than 4.5 ?C/cm2, while the minimal value was obtained for the N2B1 composite and is only 1.2 ?C/cm2. Magnetic properties were also measured and it was observed that magnetization increases with increasing the molar ratio. The largest saturation magnetization has the N2B1 composite (_51.74 emu/g) due to the larger concentration of NZFO phase. However, the sample N1B1.5 shows the largest coercive field due to the highest interface interaction. This study provides guidelines for the fabrication of NZFO-BTO magnetoelectric composite ceramics.

Sol-gel synthesis and characterization of Ag nanoparticles in ZrO2 thin films

2009 ◽  
Vol 24 (8) ◽  
pp. 2541-2546 ◽  
Author(s):  
Eisuke Yokoyama ◽  
Hironobu Sakata ◽  
Moriaki Wakaki
Keyword(s):  
Thin Films ◽  
Sol Gel ◽  
Composite Films ◽  
Dip Coating ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Silver Surface ◽  
Molar Ratios ◽  
Sol Gel Synthesis

ZrO2 thin films containing silver nanoparticles were prepared using the sol-gel method with Ag to Zr molar ratios [Ag]/[Zr] = 0.11, 0.25, 0.43, 0.67, 1.00, 1.50, and 2.33. After dip coating on glass substrate, coated films were annealed at 200 and 300 °C in air. X-ray diffraction peaks corresponding to crystalline Ag were observed, but a specific peak corresponding to ZrO2 was not observed. At the molar ratio [Ag]/[Zr] = 0.25, the particle size of Ag distributed broadly centered at 17 nm for an annealing temperature of 200 °C and at 25 nm for 300 °C. The films annealed in air at 200 °C showed an absorption band centered at 450 nm because of the silver surface plasmon resonance, whereas films heated at 300 °C in air caused a red shift of the absorption to 500 nm. The absorption peak was analyzed using the effective dielectric function of Ag-ZrO2 composite films modeled with the Maxwell-Garnett expression.

scholarly journals Photocatalytic Improvement under Visible Light inTiO2Nanoparticles by Carbon Nanotube Incorporation

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Mathana Wongaree ◽  
Siriluk Chiarakorn ◽  
Surawut Chuangchote
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Sol Gel ◽  
Multiwall Carbon Nanotubes ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Calcination Temperatures ◽  
Photocatalytic Activities ◽  
Multiwall Carbon

Photocatalytic activity ofTiO2nanoparticles was successfully enhanced by addition of multiwall carbon nanotubes (MWCNT) to make CNT/TiO2nanocomposites by sol-gel method at ambient temperature. CNT treated by HNO3 : H2SO4treatment (1 : 3 v/v) was mixed withTiO2nanoparticles at various molar ratios and calcination temperatures. The optimal molar ratio of CNT : TiO2was found at 0.05 : 1 by weight. The optimal calcination condition was 400°C for 3 h. From the results, the photocatalytic activities of CNT/TiO2nanocomposites were determined by the decolorization of 1 × 10−5 M methylene blue (MB) under visible light. CNT/TiO2nanocomposites could enhance the photocatalytic activity and showed faster for the degradation of MB with only 90 min. The degradation efficiency of the MB solution with CNT/TiO2nanocomposite achieved 70% which was higher than that with pristineTiO2(22%). This could be explained that CNT preventsTiO2from its agglomeration which could further enhance electron transfer in the composites. In addition, CNT/TiO2nanocomposites had high specific surface area (202 m2/g) which is very promising for utilization as a photocatalyst for environmental applications.

Phase transformation and characterization of TiO2 and ZrO2 addition in the Li2O–Al2O3-SiO2 gels

1996 ◽  
Vol 11 (10) ◽  
pp. 2611-2615 ◽  
Author(s):  
Ming-Hong Lin ◽  
Moo-Chin Wang
Keyword(s):  
Phase Transformation ◽  
Sol Gel ◽  
Peak Position ◽  
X Ray Diffraction ◽  
Transformation Behavior ◽  
Ceramic Powders ◽  
Higher Temperature ◽  
Gel Technique ◽  
Dta Curves

Glass-ceramic powders with a composition of Li2O · Al2O3 · 4SiO2 (LAS) have been synthesized by the sol-gel technique using LiOCH3, Al(OC2H5)3, Si(OC2H5)4, Ti(OC2H5)4, and Zr(OC2H5)4 as starting materials and the phase transformation behavior during calcination has been investigated. Differential thermal analysis (DTA), x-ray diffraction (XRD), and scanning electron microscopy (SEM) were utilized to determine the thermal behavior of the gels. Considering the LAS gels with 6.0 wt. % TiO2 and various wt. % ZrO2 content, and peak position of the β-spodumene phase formation in DTA curves was shifted to a higher temperature when the ZrO2 content was increased. The activation energy of β-spodumene crystallization was 283.8 kcal/mol for LAS gels with 6.0 wt. % TiO2 and 2.0 wt. % ZrO2. Unlike foregoing studies for LAS gels, during calcination of the dried LASTZ gels from 800 °C to 1200 °C neither β-eucryptite nor γ-spodumene was noted to be present. The crystallized phases comprised of β-spodumenes as the major phase and rutile (TiO2) together with zirconia (ZrO2) are precipitated as minor phases.

The Influences of Different Precursors on Morphology of Bi3TiNbO9 Powders Prepared by a Sol-Gel Method

2013 ◽  
Vol 815 ◽  
pp. 765-772 ◽  
Author(s):  
Zuo Dong Li ◽  
Dan Liu
Keyword(s):  
Ethylene Glycol ◽  
Chemical Method ◽  
Single Phase ◽  
Perovskite Phase ◽  
Sol Gel ◽  
Particle Morphology ◽  
Deionized Water ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Baking Process

Bi3NbTiO9 (BNTO) powders were synthesized by a sol-gel chemical method using niobium oxalates, bismuth nitrate and tetra-n-butyl-titanate as starting materials. In order to determine the influence of the molar ratio of the deionized water to ethylene glycol on the particle morphology and crystallization, different molar ratios, the deionized water/ethylene glycol, were chosen to prepare BNTO powders. Single phase BNTO powders could be obtained at a calcinations temperature of 600°C. Moreover, the possible formation mechanism of BNTO powders was also proposed in this paper. In the baking process, perovskite phase BNTO was formed via a reaction between oxides and bismuth niobium.

Morphology and Phase Composition of Sol-Gel Derived Aluminum Borate Nanowhiskers

2015 ◽  
Vol 659 ◽  
pp. 121-126 ◽  
Author(s):  
Pat Sooksaen
Keyword(s):  
Fourier Transform ◽  
Phase Composition ◽  
Sol Gel ◽  
Molar Ratio ◽  
Aluminum Borate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Higher Temperature ◽  
Sol Gel Synthesis ◽  
Scanning Electron

Aluminium borate nanowhiskers with varying aspect ratio were synthesized via sol–gel synthesis. The morphology of aluminum borate (Al4B2O9 and Al18B4O33) nanowhiskers could be controlled by varying the aluminum to boron (Al:B) molar ratio in the sol–gel derived precursors. Sintering temperatures (850 and 1100°C) and sintering times (4 and 32 hours) also affected the phase composition and size of the nanowhiskers. Citric acid was also added in the sol–gel derived precursors as a surface stabilizer for obtaining uniform finely dispersed nanostructures. Fine nanowhiskers were obtained by the calcination at 850°C, whereas higher temperature of 1100°C led to thicker and longer nanowhiskers and became rod-like crystals. The morphology and phase composition were investigated by field emission scanning electron microscope and X-ray diffraction. Chemical bond vibrations in the synthesized nanowhiskers were investigated by Fourier-transform infrared spectroscopy.

Characterization and Photocatalytic Activity of Composite La-TiO2/ITO Thin-Film Electrodes

2009 ◽  
Vol 79-82 ◽  
pp. 899-902
Author(s):  
Ming Yi Chang ◽  
Wei Fu Wang ◽  
Yung Hsu Hsieh ◽  
Chen Yu Chang
Keyword(s):  
Sol Gel ◽  
Dip Coating ◽  
Molar Ratio ◽  
Xrd Pattern ◽  
Molar Ratios ◽  
Sem Image ◽  
Uniform Particles ◽  
Spherical Structure ◽  
Coating Method ◽  
Dip Coating Method

The different molar ratios of La/Ti (0.025, 0.050, 0.075 and 0.100) photocatalytic electrodes use in this study were synthesized by sol-gel method and dip-coating method. The XRD pattern of TiO2/ITO presents only anatase phases, [1] but for La-TiO2/ITO presents both anatase and rutile phases. The SEM image of the La-TiO2/ITO showed particles of regular shapes with smaller size (＜10nm) compared to the TiO2/ITO, which presented uniform particles of spherical structure and larger size （20nm）.The La-TiO2/ITO photocatalytic electrode with molar ratio 0.050 shows the best ability both on the absorbtion and photocatalytsis. Applied potential 2.0V would effectively increase the photoelectrocatlaytic activity under visible light irradiation.

Optical properties of ZnO nanoparticles synthesized by varying the sodium hydroxide to zinc acetate molar ratios using a Sol-Gel process

Open Physics ◽  
2011 ◽  
Vol 9 (5) ◽  
Author(s):  
Francis Dejene ◽  
Abdub Ali ◽  
Hendrik Swart ◽  
Reinhardt Botha ◽  
Kittesa Roro ◽  
...  
Keyword(s):  
Zno Nanoparticles ◽  
Sol Gel ◽  
Visible Region ◽  
Blue Emission ◽  
Molar Ratio ◽  
Broad Emission Band ◽  
Photoluminescence Intensity ◽  
Molar Ratios ◽  
Quantum Confinement Effects ◽  
Sol Gel Process

AbstractMaterial property dependence on the OH−/Zn2+ molar ratio of the precursor was investigated by varying the amount of NaOH during synthesis of ZnO. It was necessary to control the water content and temperature of the mixture to ensure the reproducibility. It was observed that the structural properties, particle size, photoluminescence intensity and wavelength of maximum intensity were influenced by the molar ratio of the precursor. The XRD spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes of wurtzite ZnO, indicating a single phase. UV measurements show the absorption that comes from the ZnO nanoparticles in visible region. The absorption edge of these ZnO nanoparticles are shifted to higher energies and the determined band gap energies are blue shifted as the OH−/Zn2 molar ration increases, due to the quantum confinement effects. The photoluminescence characterization of the ZnO nanostructures exhibited a broad emission band centred at green (600 nm) region for all molar ratios except for OH−/Zn2+ = 1.7 where a second blue emission around 468 nm was also observed. The photoluminescence properties of ZnO nanoparticles were largely determined by the size and surface properties of the nanoparticles.

Measurement and Characterization of CeO2-TiO2 Ion Storage Films for Electrochromic Devices

2017 ◽  
Vol 726 ◽  
pp. 276-281
Author(s):  
Wei Shan Wu ◽  
Xiao Ping Liang ◽  
Jun Wang ◽  
Peng Chen ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Sol Gel ◽  
Dip Coating ◽  
Optical Measurements ◽  
Molar Ratio ◽  
Nitrate Hexahydrate ◽  
Electrochromic Devices ◽  
Molar Ratios ◽  
Ion Storage ◽  
The Stability ◽  
Dip Coating Technique

CeO2-TiO2 sols and films were prepared by sol-gel method. The precursor sols consist of a mixture of cerium nitrate hexahydrate Ce(NO3)3·6H2O, butyl titanate Ti(OC4H9)4 and anhydrous ethanol CH3CH2OH. The films were deposited using the dip-coating technique and calcined at 310 °C in an oxygen atmosphere. The effects of the molar ratios of cerium to titanium（0.55:1, 0.70:1, 0.85:1, 1:1）on the microstructure and properties of (CeO2)x-TiO2 films were investigated. The surface morphology, electrochemical performance and optical property were characterized by FE-SEM, cyclic voltammetry (CV) and UV-Visible spectrometer, respectively. The results show that the properties of the films are tightly related to cerium to titanium ratio. When the molar ratio of cerium to titaniumis 0.85:1, the ion storage capacity value of CeO2-TiO2 film is 19.99mC/cm2, whereas the pure TiO2 film is 11.52mC/cm2. The stability tests and optical measurements confirm that the developed CeO2-TiO2 films can be use as ion storage-counter eletrodes in electrochromic devices.

scholarly journals Effect of parameters on butyl butyrate synthesis using novel Aspergillus niger lipase as biocatalyst

2018 ◽  
Vol 40 (1) ◽  
pp. 35999 ◽  
Author(s):  
Beatriz Medeiros Travalia ◽  
Mercia Galvão ◽  
Alvaro Silva Lima ◽  
Cleide Mara Faria Soares ◽  
Narendra Narain ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Sol Gel ◽  
Molar Ratio ◽  
Free Form ◽  
Butyl Butyrate ◽  
Pumpkin Seeds ◽  
Higher Temperature ◽  
Substrate Molar Ratio ◽  
Esterification Reactions ◽  
Butyrate Production

 A novel “green” Aspergillus niger lipase, obtained from the fermentation of pumpkin seeds, was used in a free form and encapsulated in sol-gel matri x in butyl butyrate (pineapple flavor) synthesis. Esterification reactions were performed with varying substrate molar ratio (butanol: butyric acid) ranging between 1:1 and 5:1; temperature between 30 and 60°C and biocatalyst mass between 0 and 1g, respectively, according to experimental design 23 with 6 axial and 3 central points. Maximum butyl butyrate production was obtained when substrate molar ratio (butanol:butyric acid) 3:1, temperature at 60°C and 0.5 g free or encapsulated lipase as biocatalyst, were used. Temperature was the most significant parameter for production with the two biocatalysts, indicating that higher rates mean greater compound synthesis. Response surface plots showed that higher butyl butyrate production may be obtained with higher temperature and molar ratio rates (butanol:butyric acid) and with lower rates of biocatalyst mass in reactions catalyzed by free or encapsulated lipase. Aspergillus niger lipase obtained from agro-industrial waste could be employed as biocatalyst in esterification reactions in the production of natural aroma as butyl butyrate.  

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