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Special Issue "Sol-Gel Synthesis of Materials"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 7867

Special Issue Editor

Prof. Dr. Aivaras Kareiva
E-Mail Website
Guest Editor
Institute of Chemistry, Vilnius University, LT-03225 Vilnius, Lithuania
Interests: sol–gel synthesis; multifunctional metal oxides; optical materials; bioceramic materials; nanomaterials; conservation chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Over the last few decades, the sol-gel techniques have been used to prepare a variety of mixed-metal oxides, nanomaterials and nanoscale architectures, nanoporous oxides, organic-inorganic hybrids. These materials now represent one of the largest manufacturing sectors in the world. One challenge for the high end of the market is the development of alternative synthesis technologies that are not just “greener” but provide environmentally benign processes. It is well known also that physical properties of crystalline materials are strongly dependent on the phase purity, grain size and grain size distribution. Therefore, it is also very important to develop simple, reliable and cost-effective synthesis method for the preparation of products with controllable phase purity and surface morphology. Among different synthesis methods, sol–gel processing route is most convenient method because of its simplicity, good mixing of starting materials, relatively low reaction temperature and easy control of chemical composition of the end product. Sol-gel synthesis is utilized to fabricate advanced materials in a wide variety of forms: ultrafine powders, thin film coatings, fibbers, porous or dense materials. The scope of this Special Issue of Materials is focused on the development of sol-gel synthesis technique, and application of sol-gel processing for the fabrication of multifunctional materials, which are important in all industrial areas. The field of the research in the evolution of inorganic networks through the formation of a colloidal suspension (sol) and gelation of the sol to form three-dimensional, continuous network in a liquid phase (gel) is very much appreciated.

Prof. Aivaras Kareiva
Guest Editor

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Keywords

  • sol-gel synthesis
  • aqueous processing
  • metal alkoxides route
  • mixed-metal oxides
  • nanomaterials
  • organic-inorganic hybrids
  • functional materials
  • ultrafine powders
  • thin/thick films
  • fibbers
  • porous and dense materials

Published Papers (7 papers)

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Research

Article
Crystal Structure and Concentration-Driven Phase Transitions in Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) Prepared by the Sol–Gel Method
Materials 2022, 15(3), 1048; https://doi.org/10.3390/ma15031048 - 29 Jan 2022
Viewed by 376
Abstract
The structural state and crystal structure of Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) compounds prepared by a chemical route based on a modified sol–gel method were investigated using X-ray diffraction, Raman spectroscopy, as well as scanning [...] Read more.
The structural state and crystal structure of Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) compounds prepared by a chemical route based on a modified sol–gel method were investigated using X-ray diffraction, Raman spectroscopy, as well as scanning electron microscopy. It was observed that chemical doping with Sc ions led to a structural phase transition from the orthorhombic structure to the hexagonal structure via a wide two-phase concentration region of 0.1 < x < 0.45. An increase in scandium content above 80 mole% led to the stabilization of the non-perovskite bixbyite phase specific for the compound ScFeO3. The concentration stability of the different structural phases, as well as grain morphology, were studied depending on the chemical composition and synthesis conditions. Based on the data obtained for the analyzed samples, a composition-dependent phase diagram was constructed. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
Magnetic Properties and Morphology Copper-Substituted Barium Hexaferrites from Sol-Gel Auto-Combustion Synthesis
Materials 2021, 14(19), 5873; https://doi.org/10.3390/ma14195873 - 07 Oct 2021
Cited by 2 | Viewed by 566
Abstract
The copper (Cu) substitution in barium hexaferrite (BaFe12O19) crystals from the sol-gel auto-combustion synthesis is demonstrated as a cost-effective pathway to achieve alterable magnetic properties. Subsequent heat treatments at 450 °C and 1050 °C result in irregularly shaped nanoparticles [...] Read more.
The copper (Cu) substitution in barium hexaferrite (BaFe12O19) crystals from the sol-gel auto-combustion synthesis is demonstrated as a cost-effective pathway to achieve alterable magnetic properties. Subsequent heat treatments at 450 °C and 1050 °C result in irregularly shaped nanoparticles characterized as the M-type BaFe12O19 with the secondary phase of hematite (α-Fe2O3). Despite the mixed phase, the substantial coercivity of 2626 Oe and magnetization as high as 74.8 emu/g are obtained in this undoped ferrite. The copper (Cu) doing strongly affects morphology and magnetic properties of BaFe12−xCuxO19 (x = 0.1, 0.3, and 0.5). The majority of particles become microrods for x = 0.1 and microplates in the case of x = 0.3 and 0.5. The coercivity and magnetization tend to reduce as Cu2+ increasingly substitutes Fe3+. From these findings, magnetic properties for various applications in microwave absorbers, recording media, electrodes, and permanent magnets can be tailored by the partial substitution in hexaferrite crystals. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
Lanthanum and Manganese Co-Doping Effects on Structural, Morphological, and Magnetic Properties of Sol-Gel Derived BiFeO3
Materials 2021, 14(17), 4844; https://doi.org/10.3390/ma14174844 - 26 Aug 2021
Cited by 2 | Viewed by 744
Abstract
In this work, lanthanum and manganese co-substitution effects on different properties of bismuth ferrite solid solutions Bi1-xLaxFe0.85Mn0.15O3 (x from 0 to 1) prepared by a sol-gel synthetic approach have been investigated. It was observed [...] Read more.
In this work, lanthanum and manganese co-substitution effects on different properties of bismuth ferrite solid solutions Bi1-xLaxFe0.85Mn0.15O3 (x from 0 to 1) prepared by a sol-gel synthetic approach have been investigated. It was observed that the structural, morphological, and magnetic properties of obtained specimens are influenced by the amount of introduced La3+ ions. Surprisingly, only the compound with a composition of BiFe0.85Mn0.15O3 was not monophasic, and the presence of neighboring phases was determined from X-ray diffraction analysis and Mössbauer measurements. Structural transitions from orthorhombic to cubic and back to orthorhombic were also observed depending on the La3+ amount. Antiferromagnetic behaviour was observed for all of the samples, with the highest magnetisation values for Bi0.5La0.5Fe0.85Mn0.15O3. Additionally, structural attributes and morphological features were evaluated by Raman spectroscopy and scanning electron microscopy (SEM), respectively. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
Optimization of Hybrid Sol-Gel Coating for Dropwise Condensation of Pure Steam
Materials 2020, 13(4), 878; https://doi.org/10.3390/ma13040878 - 15 Feb 2020
Cited by 4 | Viewed by 1234
Abstract
We developed hybrid organic–inorganic sol–gel silica coatings with good durability in harsh environment (high temperatures, high vapor velocities) and with slightly hydrophobic behavior, sufficient to promote dropwise condensation (DWC) of pure steam. DWC is a very promising mechanism in new trends of thermal [...] Read more.
We developed hybrid organic–inorganic sol–gel silica coatings with good durability in harsh environment (high temperatures, high vapor velocities) and with slightly hydrophobic behavior, sufficient to promote dropwise condensation (DWC) of pure steam. DWC is a very promising mechanism in new trends of thermal management and power generation systems to enhance the heat transfer during condensation as compared to film-wise condensation (FWC). The sol–gel coatings have been prepared from methyl triethoxy silane (MTES) and tetraethyl-orthosilicate (TEOS) and deposited on an aluminum substrate. The coatings were optimized in terms of precursor ratio and annealing temperature highlighting potentials and limits of such mixtures. A comprehensive surface characterization before and after saturated steam condensation tests has been performed and related to the thermal measurements for evaluating the heat transfer augmentation as compared to FWC obtained on untreated aluminum surfaces. The results showed that the developed hybrid organic-inorganic sol–gel silica coatings are promising DWC promoters. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
The Effect of Chitosan’s Addition to Resorcinol/Formaldehyde Xerogels on the Characteristics of Resultant Activated Carbon
Materials 2019, 12(23), 3847; https://doi.org/10.3390/ma12233847 - 22 Nov 2019
Cited by 1 | Viewed by 1033
Abstract
Hybrid chitosan-resorcinol/formaldehyde xerogels were synthesized, and the effect of including minor quantities of chitosan on the consequent activated carbon was investigated. The resulting activated carbon were characterized by different techniques. Clear changes were found in the structure of activated carbon as a result [...] Read more.
Hybrid chitosan-resorcinol/formaldehyde xerogels were synthesized, and the effect of including minor quantities of chitosan on the consequent activated carbon was investigated. The resulting activated carbon were characterized by different techniques. Clear changes were found in the structure of activated carbon as a result of including chitosan in the synthesis. The results showed that the disorder ratio of crystal lattice decreased from 0.750 to 0.628 when increasing the concentration of chitosan from 0 to 0.037 wt%. The micropores increased from ~0.3% to ~1.0%, mesopores increased from ~11.2% to ~32.9% and macropores decreased from ~88.4% to ~66.1%. The total pore volume decreased from 1.040 to 0.238 cm3/g and the total pore surface area decreased from 912.3 to 554.4 m2/g. On the other hand, the average pore width decreased from 2.3 to 0.8 nm and the average particle size decreased from 224 to 149 nm. Nano-scale Scanning Electron Microscope (NanoSEM) morphology indicated a critical composition of chitosan (0.022 wt%) that affects the structure and thermal stability of activated carbon produced. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
Undoped and Eu3+ Doped Magnesium-Aluminium Layered Double Hydroxides: Peculiarities of Intercalation of Organic Anions and Investigation of Luminescence Properties
Materials 2019, 12(5), 736; https://doi.org/10.3390/ma12050736 - 04 Mar 2019
Cited by 11 | Viewed by 1474
Abstract
The Mg3/Al and Mg3/Al0.99Eu0.01 layered double hydroxides (LDHs) were fabricated using a sol-gel chemistry approach and intercalated with different anions through ion exchange procedure. The influence of the origin of organic anion (oxalate, laurate, malonate, succinate, [...] Read more.
The Mg3/Al and Mg3/Al0.99Eu0.01 layered double hydroxides (LDHs) were fabricated using a sol-gel chemistry approach and intercalated with different anions through ion exchange procedure. The influence of the origin of organic anion (oxalate, laurate, malonate, succinate, tartrate, benzoate, 1,3,5-benzentricarboxylate (BTC), 4-methylbenzoate (MB), 4-dimethylaminobenzoate (DMB) and 4-biphenylacetonate (BPhAc)) on the evolution of the chemical composition of the inorganic-organic LDHs system has been investigated. The obtained results indicated that the type and arrangement of organic guests between layers of the LDHs influence Eu3+ luminescence in the synthesized different hybrid inorganic–organic matrixes. For the characterization of synthesis products X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy, fluorescence spectroscopy (FLS), and scanning electron microscopy (SEM), were used. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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Article
Synthesis and Characterization of TiO2-ZnO-MgO Mixed Oxide and Their Antibacterial Activity
Materials 2019, 12(5), 698; https://doi.org/10.3390/ma12050698 - 27 Feb 2019
Cited by 22 | Viewed by 1888
Abstract
TiO2-ZnO-MgO mixed oxide nanomaterials (MONs) were synthetized via the sol-gel method and characterized by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), nitrogen physisorption analysis, X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Fourier [...] Read more.
TiO2-ZnO-MgO mixed oxide nanomaterials (MONs) were synthetized via the sol-gel method and characterized by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), nitrogen physisorption analysis, X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Fourier transform infrared spectroscopy (FTIR), and color (Luminosity (L), a, b, Chrome, hue) parameters. Furthermore, the antimicrobial activity of the MONs was tested against Escherichia coli (EC), Salmonella paratyphi (SP), Staphylococcus aureus (SA), and Listeria monocytogenes (LM). The MONs presented a semi globular-ovoid shape of ≤100 nm. Samples were classified as mesoporous materials and preserved in the TiO2 anatase phase, with slight changes in the color parameters of the MONs in comparison with pure TiO2. The MONs exhibited antimicrobial activity, and their effect on the tested bacteria was in the following order: EC > SP > SA > LM. Therefore, MONs could be used as antimicrobial agents for industrial applications. Full article
(This article belongs to the Special Issue Sol-Gel Synthesis of Materials)
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