Development Of Sol Research Articles

State-of-the-art and development of sol–gel technology in Uzbekistan (Preface)

State-of-the-art and development of sol–gel technology in Uzbekistan (Preface)

Preparation of mesoporous silica microparticles by sol–gel/emulsion route for protein release

Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol–gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol–gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.

Characterization of Nanoscaled TiO2 Produced by Simplified Sol–Gel Method Using Organometallic Precursor

This work is concerned with development of sol–gel method for preparation of nanoscaled TiO2 using organometallic precursor—titanium tetraisopropoxide (TTIP) and determination of the present crystalline phases depending on the temperature of further thermal treatment. The characteristic processes and transformations during the thermal treatment were determined by means of thermal gravimetric analysis and/or differential thermal analysis (TGA/DTA) method. The crystalline structure and size of the TiO2 crystallites were analyzed by means of Raman spectroscopy and X-ray powder diffraction (XRPD) method. At 250 °C, cryptocrystalline structure was detected, where amorphous TiO2 is accompanied with crystalline anatase. The anatase crystallite phase is stable up to 650 °C, whereas at higher temperature rutile transformation begins. It was observed that at 800 °C, almost the whole TiO2 is transformed to rutile phase. According to XRPD analysis, the increase of the temperature influences on the increase of the size of the crystalline particles ranging from 6 nm at 250 °C to less than 100 nm at 800 °C. The size and shape of the TiO2 crystalline particles were observed by transmission electron microscopy (TEM). The shape of the studied samples changes from nanospheres (250, 380, and 550 °C) to nanorods (650 and 800 °C). Morphology of the formed TiO2 aggregates was observed by scanning electron microscopy (SEM).

Characterisation of thermal barrier sensor coatings synthesised by sol–gel route

Further improvements in the efficiency of gas turbines are recognised to come from increases in turbine entry temperatures. Accurate temperature measurements are crucial to achieve these increases whilst maintaining reliability and economic component life. The combination of phosphor thermometry and thermal barrier coating (TBC) technology has led to the development of functional temperature sensor coatings which have several advantages over conventional temperature measurement techniques. Developments in sol–gel processing indicate that this method could be used for the production, or particularly, the repair of TBCs in the future.This paper demonstrates, for the first time, that sol–gel processing can be used to make sensor TBCs. The optimum concentration of SmO1.5 was 2wt.% in YSZ to achieve the brightest phosphorescence emission. Above this concentration the overall intensity of the emission reduces and the transitions from 4F3/2 were suppressed. Furthermore, a similar suppression of these transitions was observed when the product of the sol–gel was heat treated to 1100°C. This was concluded to be due to a higher degree of crystallinity allowing a greater interaction between the dopant ions. The dependence of the phosphorescence spectrum on heat treatment temperature provides the first indication that YSZ produced through sol–gel could be used to detect historic temperatures.An evaluation of the subsurface measurement and temperature capabilities has shown that the phosphorescence can be detected from relatively thin layers, 20μm, even under 50μm of undoped YSZ coating. Although the temperature detection range, 400–700°C, is too low for advanced TBCs the material could be used in low temperature regimes or for health monitoring purposes.

Effect of vapor thermolysis on microstructure development of sol–gel-derived lead zirconate–titanate (PZT) and PZT-Sr(K0.25Nb0.75)O3 solid solutions

Ceramic granules of PZT (Pb(Zr53,Ti47)O3) and fibers of SKN-doped PZT (1 Mol-% Sr(K0.25Nb0.75)O3 substitution in PZT) were fabricated from sol–gel precursors. The transformation of the metal–organic gel to the oxide and its crystallization behavior was investigated by thermogravitmetry, and XRD. The formation of pyrochlore or perovskite phase was sensitive to the preceeding heat treatment conditions in moist atmosphere (termed vapor thermolysis). Lower thermolysis temperatures resulted in the preferred formation of metastable pyrochlore phase. Higher thermolysis temperatures favored the formation of perovskite. Investigation of sintered materials revealed a superior sintering activity for samples with pronounced intermediate pyrochlore content whereas low-pyrochlore samples remained highly porous after sintering. For constant chemical precursors the vapour thermolysis conditions (220–280 °C) siginificantly affected crystallization and sintering behavior of the PZT and SKN-PZT material.

Introducing ecodesign in silica sol–gel materials

Over the last decade, ecodesign has been introduced as a concept and a methodological framework to identify and improve sustainability in product development. In this context, the 12 principles of green chemistry provide suitable guidelines for the elaboration of molecules and materials in conditions that meet some ecodesign-related criteria. Sol–gel chemistry is an interesting domain to be examined in this perspective because it was early identified as an eco-friendly process compared to traditional routes to ceramics and glasses. Thus it is not surprising that many recent developments in sol–gel technology have, explicitly or not, addressed sustainability issues. In this review, we present an overview of these advances, focusing on the chemistry of silica. Starting from the typical reaction involving tetraethoxysilane hydrolysis and condensation in hydro-alcoholic media in the presence of inorganic catalysts, the current alternatives in terms of precursors, solvents, catalysts and activation sources are presented. As an example of hybrid materials, the synthesis of surfactant-based mesostructured silica is commented. Manufacturing methods to nanoproducts, including sol–gel technology are also discussed in terms of sustainability. Finally, the recyclability and degradation of sol–gel silica are briefly commented on. As a conclusion, some perspectives and current limitations for the development of a “greener” sol–gel chemistry are provided, extending the discussion to non-silica materials.

From Montpellier 1985 to Montpellier 2007

Since the pioneering meeting in 1981 in Padova, the international sol–gel community (now represented by the ISGS—International Sol–Gel Society) has celebrated advances in sol–gel science and technology in what has now become an important biannual conference series. The aim of the first meeting was to bring together eminent scientists working in this field throughout the world, to promote the exchange of ideas and the development of sol–gel materials with new potential applications. In September 1985, the third meeting in this series (the ‘‘Third International Workshop on Glasses and Glass Ceramics from Gels’’) was held in Montpellier (France). Twenty-two years later (in 2007), it returned to Montpellier as the ‘‘14th International Sol–Gel Conference’’. The outstanding success of this most recent meeting makes it tempting to offer a brief overview of the striking evolution of sol–gel science and technology over the past two decades. Thus, the original ‘‘workshop’’ has now become a ‘‘conference’’, with two parallel sessions featuring nearly 80 talks and more than 450 posters by delegates from 41 countries. This reflects the interest of the scientific community in the multidisciplinary field now simply referred to as ‘‘sol–gel’’, which has now grown well beyond its origins in traditional materials science underpinning development in glasses and ceramics. Historically the ninth workshop held in 1997 in Sheffield (England) was the first to extend the focus of the workshops to include ‘‘Hybrids and Nanocomposites from Gels’’, acknowledging the considerable developments in organic– inorganic materials. Combining organic and inorganic functionalities through a sophisticated ‘‘bottom up’’ approach, such hybrid materials considerably extended the range of accessible properties and inherent versatility of sol–gel materials. This approach led to new applications in photonics, sensing and electrochemistry. In the field of macromolecular chemistry, it led to hybrid nanocomposites, including polymers reinforced with inorganic nanofillers, as well as inorganic nanoparticles coated with an organic layer, and even systems with two interpenetrating continuous phases. The burst of research on nanoporous materials, synthesised by using self-assembling organic species as supramolecular templates stood out in the late nineties. It led to the development of materials with periodic porosity and hierarchical structures resulting in considerable technical developments, especially in the implementation of nanostructured films. In more recent times, the evolution of the field towards medical applications (drug delivery, bio-imaging etc.) and biomaterials is striking. Following the pioneering works of David Avnir and Jacques Livage, there is currently a growing interest in materials at the interface with biology such as those stemming from the encapsulation of enzymes and living cells in gels. This volume is the first of the Special Issues of the Journal of Sol–Gel Science and Technology devoted to the 14th International Sol–Gel Conference. It features work presented by Keynote and Invited speakers, including the work of the recipients of the Ulrich Awards and the Life Achievement Award. It is intended to provide an overview of the current state of—and key developments in—sol–gel science and technology and to illustrate the unique ‘‘melting pot’’ of knowledge, skills and concepts which will stimulate the development of tomorrow’s innovative technologies. We hope that you share our sense of excitement about the directions in which the field is evolving, as it continues to build up on its strong foundations in physics, biology and molecular chemistry. M. W. C. Man A. Vioux (&) Institut Charles Gerhardt, Montpellier, France e-mail: vioux@univ-montp2.fr

Solid‐state lasers based on inorganic–organic hybrid materials obtained by combined sol–gel polymer technology

AbstractSol–gel glass matrices in which organic laser dyes are embedded can be used as the gain medium in solid‐state, continuously tunable lasers. Such lasers are very simple to construct, and potentially very compact and efficient. Unlike the commonly used liquid dye laser systems, solid‐state dye lasers can be made mechanically robust and portable. In this article, the development of sol–gel/dye lasers, including the sol–gel technology, dye properties, and laser operation, is reviewed. In addition, new solid‐state hosts (such as polyurethane/silica ORMOSILs), additional organic dyes (cyanines), and new studies on the stability of the dyes are presented. Copyright © 2004 John Wiley & Sons, Ltd.

Characterization of pitting corrosion in bare and sol–gel coated aluminum 2024-T3 alloy

The prevention of pitting corrosion in aerospace aluminum alloys by the application of protective sol–gel coatings requires a thorough understanding of pit formation kinetics and morphology developments in such surface coating systems. This study reports results of chemical and electrochemical methods of pitting corrosion tests for bare and sol–gel coated Al 2024-T3 alloy. Specific attention is focused on the characterization of pitting in samples coated with vinyl-silicate and epoxy-silicate sol–gel coatings. Specimens were exposed to a variety of chemically aggressive environments, based on 3–5% NaCl solutions with addition of HCl and H 2SO 4, including a standard CASS solution. The exposure of bare samples to these environments produced extensive surface corrosion, but pits were not observed for sol–gel coated samples. Anodic polarization tests with potentials above that required for pitting in bare samples were used to initiate pitting corrosion in sol–gel coated samples. A corrosion current monitoring test provided a method of controlling the pit formation process, which provides well-defined pits in terms of spatial density and geometry. A two-stage kinetic phase in pit development was observed and correlated with pit morphological developments in sol–gel coatings. An initial low current stage was associated with pit penetration through the coating to the surface and the secondary high current stage was associated with an active growth stage which grew in sub-coating surface interface regions. Results of this research provide a basis for designing and improving corrosion protection systems based on the application of sol–gel coatings.

Electrochromic characterization of sol–gel deposited coatings

Electrochromic devices have increasing application in large-area display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol–gel process offers an alternative approach to the synthesis of low-cost, high-quality electrochromic device layers. This paper discusses the developments in sol–gel-deposited electrochromic films and a prototype all sol–gel device with switching from 80% to 50% (550nm). The sol–gel process involves the formation of oxide networks upon hydrolysis–condensation of alkoxide precursors. In this study, we cover sol–gel-deposited oxides of WO3, TiO2, Nb2O5, V2O5, Ni(OH)2, Co(OH)2 and CuOx. The coloration reaction voltammetry and spectral optical properties are presented for selected films.

“Figure/Ground” Study of Colloidal Silica Nanoparticles and Corresponding Microporous Xerogels

A critical hurdle in the development of sol−gel techniques for the preparation of microporous inorganic materials is elucidating the effect of key synthesis and processing parameters on the structure of the resulting sols. Characterization of colloidal particles with diameters of less than approximately 10 nm is problematic using conventional techniques such as dynamic light scattering. Similarly, quantitative determination of pore size distribution in the resulting materials using gas adsorption isotherms is difficult in the microporous regime. The present work extends these traditional methods with the objective of obtaining information both on the particle size in an inorganic sol and on the pore size distribution in the resulting microporous xerogel. Silica sols synthesized at pH 3 and an H2O/TEOS ratio of r = 83 were shown by atomic force microscopy to have a distribution of particle diameters centered around approximately 4−6 nm. Nitrogen and molecular probe adsorption studies on xerogels derived fr...

The development of SOL—a support expert system for designing wire rolling sequences

The use of the SOL expert system for designing copper wire rolling sequences has provided support to the production planning tasks related to the rolling process at the Magneto plant of Condumex. The operators' own methodologies for wire processing were included, and are being used by the expert system, as well as historical and statistical data of the rolling process. The SOL expert system currently performs the design of all of the rolling sequences at the Magneto plant. The effectiveness achieved by the system is 95%, and its valid wire dimensions range can be increased every time a new effective design is incorporated into its knowledge base.