Microwave Drying of Borosilicate Gels

1990 ◽  
Vol 189 ◽  
Author(s):  
Srinivas Surapanani ◽  
Michael E. Mullins ◽  
B.C. Cornilsen
Keyword(s):  
Sol Gel ◽  
Structural Evolution ◽  
Microwave Drying ◽  
Novel Technique ◽  
Processing Times ◽  
Hydrolysis Process ◽  
Drying Techniques ◽  
Processing Techniques ◽  
First Time ◽  
State Processing

ABSTRACTMicrowave processing was carried out on SiO2 -B2O3 solutions and gels prepared by sol-gel methods. Monolithic gels were prepared from alcoholic solutions of trimethylborate and tetraethylorthosilicate using a two-step hydrolysis process. A novel technique of Liquid State Processing (LSP) was employed for the first time, and it was found to be faster and more effective than the conventional processing techniques. The structural evolution of the dried products was followed using FTIR. The effect of processing was examined via surface area analysis (BET), electron microscopy, and FTIR. The microwave drying has been compared with conventional oven drying and vacuum drying techniques. Shorter processing times, improved microstructures, and unique properties have been obtained.

Photochemistry Channels of Merocyanine Encapsulated in Sol-Gel Glasses

1994 ◽  
Vol 346 ◽  
Author(s):  
A. M. Mahloudji ◽  
L. B. Meuret ◽  
C. T. Lin
Keyword(s):  
Molecular Form ◽  
Photophysical Properties ◽  
Sol Gel ◽  
Emission Spectra ◽  
Transfer Characteristic ◽  
Optically Transparent ◽  
Quinoid Form ◽  
Gel Glasses ◽  
Processing Techniques ◽  
First Time

ABSTRACTPhotophysical properties of l-Docosyl-4-(4-hydroxystyryl)pyridiniurn bromide (SB), a merocyanine dye in solution and encapsulated in sol-gel derived glass are investigated at 298 and 77 K. In solution, the absorption spectra of SB display an equilibrium between the quinolinium and benzoid forms. The equilibrium can be shifted to either quinolinium or benzoid form under an acidic or basic condition, respectively. The emission spectra of SB, on the other hand, give not only the quinolinium and benzoid forms but also the quinoid form which emits at 500 nm. The existence of excited state quinoid form of SB is also evident in the excitation spectrum while the emission at 500 nm is monitored. Both in solution and in xerogel, the quinoid form of SB is shown to be photochemically unstable as compared to the benzoid form. It is proposed that the photoexcited quinolinium form of SB is a proton dissociative species which transforms readily to become the quinoid form. The results indicate that photochemistry channels of SB are originated from the quinoid form. Moreover, the benzoid form of SB (photochemically stable) exhibits large hyperpolarizability due to its charge-transfer characteristic, and is a desired molecular form for nonlinear optical (NLO) applications. The material processing techniques for stabilizing the benzoid form of SB in optically transparent sol-gel glasses are illustrated for the first time.

scholarly journals Synthesis of novel adsorbent based on tetrasulfide-functionalized fibrous silica KCC-1 for removal of Hg(II) cations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Azam Marjani ◽  
Reza Khan Mohammadi
Keyword(s):  
Effective Interaction ◽  
Sol Gel ◽  
Aqueous Media ◽  
Synthesis Method ◽  
Mercury Ions ◽  
Toxic Heavy Metals ◽  
Uptake Capacity ◽  
Hydrothermal Preparation ◽  
Ultrasonic Assisted ◽  
First Time

AbstractHg(II) has been identified to be one of the extremely toxic heavy metals because of its hazardous effects and this fact that it is even more hazardous to animals than other pollutants such as Ag, Au, Cd, Ni, Pb, Co, Cu, and Zn. Accordingly, for the first time, tetrasulfide-functionalized fibrous silica KCC-1 (TS-KCC-1) spheres were synthesized by a facile, conventional ultrasonic-assisted, sol–gel-hydrothermal preparation approach to adsorb Hg(II) from aqueous solution. Tetrasulfide groups (–S–S–S–S–) were chosen as binding sites due to the strong and effective interaction of mercury ions (Hg(II)) with sulfur atoms. Hg(II) uptake onto TS-KCC-1 in a batch system has been carried out. Isotherm and kinetic results showed a very agreed agreement with Langmuir and pseudo-first-order models, respectively, with a Langmuir maximum uptake capacity of 132.55 mg g–1 (volume of the solution = 20.0 mL; adsorbent dose = 5.0 mg; pH = 5.0; temperature: 198 K; contact time = 40 min; shaking speed = 180 rpm). TS-KCC-1was shown to be a promising functional nanoporous material for the uptake of Hg(II) cations from aqueous media. To the best of our knowledge, there has been no report on the uptake of toxic Hg(II) cations by tetrasulfide-functionalized KCC-1 prepared by a conventional ultrasonic-assisted sol–gel-hydrothermal synthesis method.

scholarly journals How Can the Introduction of Zr4+ Ions into TiO2 Nanomaterial Impact the DSSC Photoconversion Efficiency? A Comprehensive Theoretical and Experimental Consideration

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2955
Author(s):  
Aleksandra Bartkowiak ◽  
Oleksandr Korolevych ◽  
Gian Luca Chiarello ◽  
Malgorzata Makowska-Janusik ◽  
Maciej Zalas
Keyword(s):  
Density Functional ◽  
Sol Gel ◽  
Dye Sensitized Solar Cells ◽  
Positive Influence ◽  
Photoconversion Efficiency ◽  
Doped Tio2 ◽  
Computational Calculations ◽  
Tio2 Nanomaterials ◽  
First Time ◽  
Sensitized Solar Cells

A series of pure and doped TiO2 nanomaterials with different Zr4+ ions content have been synthesized by the simple sol-gel method. Both types of materials (nanopowders and nanofilms scratched off of the working electrode’s surface) have been characterized in detail by XRD, TEM, and Raman techniques. Inserting dopant ions into the TiO2 structure has resulted in inhibition of crystal growth and prevention of phase transformation. The role of Zr4+ ions in this process was explained by performing computer simulations. The three structures such as pure anatase, Zr-doped TiO2, and tetragonal ZrO2 have been investigated using density functional theory extended by Hubbard correction. The computational calculations correlate well with experimental results. Formation of defects and broadening of energy bandgap in defected Zr-doped materials have been confirmed. It turned out that the oxygen vacancies with substituting Zr4+ ions in TiO2 structure have a positive influence on the performance of dye-sensitized solar cells. The overall photoconversion efficiency enhancement up to 8.63% by introducing 3.7% Zr4+ ions into the TiO2 has been confirmed by I-V curves, EIS, and IPCE measurements. Such efficiency of DSSC utilizing the working electrode made by Zr4+ ions substituted into TiO2 material lattice has been for the first time reported.

Sol–gel synthesis of 2-dimensional TiO2: self-assembly of Ti–oxoalkoxy–acetate complexes by carboxylate ligand directed condensation

2021 ◽  
Author(s):  
Ruohong Sui ◽  
Connor E. Deering ◽  
Rohen Prinsloo ◽  
Christopher B. Lavery ◽  
Nancy Chou ◽  
...  
Keyword(s):  
Self Assembly ◽  
Sol Gel ◽  
Carboxylate Ligand ◽  
Sol Gel Synthesis ◽  
First Time

2-Dimensional TiO2 is synthesized for the first time by a sol–gel self-assembly of Ti–oxoalkoxy–acetate complexes.

Synthesis, crystal structure and photoluminescence properties of Eu2+-activated RbCaGd(PO4)2 phosphors

RSC Advances ◽  
2016 ◽  
Vol 6 (14) ◽  
pp. 11211-11217 ◽  
Author(s):  
Xue Chen ◽  
Qidi Wang ◽  
Fengzhu Lv ◽  
Paul K. Chu ◽  
Yihe Zhang
Keyword(s):  
Crystal Structure ◽  
Sol Gel ◽  
Dipole Interaction ◽  
Concentration Quenching ◽  
Photoluminescence Properties ◽  
Gel Method ◽  
Sol Gel Method ◽  
First Time

RbCaGd(PO4)2:Eu2+ was prepared by the Pechini-type sol–gel method. The crystal structure was determined in the first time. The dipole–dipole interaction plays a major role in the mechanism of concentration quenching of Eu2+ in this phosphor.

Characterization of SrBi2Nb2O9 Thin Films Prepared by Sol Gel Technique

1996 ◽  
Vol 459 ◽  
Author(s):  
E. Ching-Prado ◽  
W. Pérez ◽  
A. Reynés-Figueroa ◽  
R. S. Katiyar ◽  
D. Ravichandran ◽  
...  
Keyword(s):  
Thin Films ◽  
Raman Band ◽  
Sol Gel ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Ft Ir ◽  
Gel Technique ◽  
High Degree ◽  
First Time

ABSTRACTThin films of SrBi2Nb2O9 (SBN) with thicknesses of 0.1, 0.2, and 0.4 μ were grown by Sol-gel technique on silicon, and annealed at 650°C. The SBN films were investigated by Raman scatering for the first time. Raman spectra in some of the samples present bands around 60, 167, 196, 222, 302, 451, 560, 771, 837, and 863 cm−1, which correspond to the SBN formation. The study indicates that the films are inhomogeneous, and only in samples with thicknesses 0.4 μ the SBN material was found in some places. The prominent Raman band around 870 cm−1, which is the A1g mode of the orthorhombic symmetry, is assigned to the symmetric stretching of the NbO6 octahedrals. The frequency of this band is found to shift in different places in the same sample, as well as from sample to sample. The frequency shifts and the width of the Raman bands are discussed in term of ions in non-equilibrium positions. FT-IR spectra reveal a sharp peak at 1260 cm−1, and two broad bands around 995 and 772 cm−1. The bandwidths of the latter two bands are believed to be associated with the presence of a high degree of defects in the films. The experimental results of the SBN films are compared with those obtained in SBT (T=Ta) films. X-ray diffraction and SEM techniques are also used for the structural characterization.

scholarly journals Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

2016 ◽  
Vol 34 (1) ◽  
pp. 164-168
Author(s):  
Raz Muhammad ◽  
Muhammad Uzair ◽  
M. Javid Iqbal ◽  
M. Jawad Khan ◽  
Yaseen Iqbal ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Sintered Sample ◽  
First Time ◽  
Alkoxide Precursors ◽  
Room Temperature Dielectric Constant

AbstractCa2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

scholarly journals Electrochemical Impedance of Hydrogenated Phases of ZnO and CuO Nanoparticles for Electrode Applications

2020 ◽  
pp. 1-6
Author(s):  
L. I. Menegbo ◽  
J. L. Konne ◽  
N. Boisa
Keyword(s):  
Electrochemical Impedance ◽  
Sol Gel ◽  
Low Frequency ◽  
High Gain ◽  
High Frequency Region ◽  
Nyquist Plots ◽  
Eis Measurements ◽  
Xrd Patterns ◽  
Straight Lines ◽  
First Time

The Electrochemical Impedance Spectroscopy (EIS) measurements of Sol-gel synthesized ZnO, CuO and their respective hydrogenated phases (ZnO:H and CuO:H) for  a proton-type battery model has been reported for the first time. The XRD patterns confirmed that CuO and ZnO were phase pure with minor impurities. However, that of CuO:H showed mixed phases of CuO and Cu2O with the later  appearing prominent. The estimated particle sizes of ZnO, ZnO:H, CuO and CuO:H obtained using Scherrers’ equation were 17.83, 17.75, 21.63 and 15.42 nm respectively, showing remarkable particle size reductions upon hydrogenation as oxygen vacancies were substituted with smaller hydrogen ions. Nyquist plots from the EIS experimental data recorded over a frequency range of 100 kHz – 5 mHz showed expected flat semicircles at the high frequency region and straight lines at the low frequency regions while resistance estimations from the intercepts of the Bode plots were 12.10, 7.80, 16.00 and 10.80 Ω for ZnO, ZnO:H, CuO and CuO:H respectively. It also indicated high gain margins suggesting impressive electrochemical properties for battery applications.

Effects of drying methods on color retention and chlorophyll of celery (ApiumgraveolensL.), spinach (Spinacia oleraceaL.), Malabar spinach (Basella albaL.)

2020 ◽  
pp. 53-61
Author(s):  
Dat Q Tran
Keyword(s):  
Microwave Drying ◽  
Drying Methods ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Color Retention ◽  
Hot Air ◽  
Drying Techniques ◽  
Dried Vegetables

Dried vegetables are considered convenient for storage, transportation and preservation. The different drying techniques could influence the quality of resulting products. This study aimed to evaluate the effects of three distinguish drying methods as hot-air drying, foam-mat drying and microwave drying on the color retention and chlorophyll of green vegetables powder. Fresh spinach(Spinacia oleraceaL.), celery (Apium graveolensL.), Malabar spinach (Basella albaL.) were dried by different methods: hot air at 60oC, foam-mat at 60oC and microwave at 270 W until the samples reached approximately 9% of moisture content (wb). The drying time of the dried samples by microwave, foam-mat and hot-air method were 60, 210 and 240 min, respectively. Foam-mat dried vegetables were found to have the best quality in terms of color and the residual chlorophyll content. The findings suggest that foam-mat drying is promising in dried vegetable processing

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