Sol-gel Production Research Articles

Sol–gel production of aluminium doped zinc oxide using aluminium nitrate

Sol–gel synthesis of aluminium doped zinc oxide was performed via a spin coating process through a precursor solution that consisted of zinc acetate, aluminium nitrate and ammonia. The effects of sintering temperature on the optoelectronic properties of the derived films were investigated through scanning electron microscopy, X-ray diffraction, photoluminescence, UV–vis spectroscopy and Hall effect measurements. It was found that as the process temperature increases the film changes from a grain-like morphology towards a nanowire structure. This trend is also evident in the presented XRD data. Optical measurements revealed the derived films to be highly transparent with an optical transparency ~92%.

Sol–gel production of wrinkled fluorine doped zinc oxide through hydrofluride acid

Wrinkled ZnO:F (FZO) thin films have been derived through sol–gel deposition process, using a mixture of zinc acetate aluminum chloride, hydrofluoric acid and isopropanol. It is found that the deposited FZO thin films are highly transparent with sheet resistivity of around 0.07Ωcm. Scanning electron microscopy images and XRD measurements indicated that these FZO thin films are wrinkled with a preferential growth in the c-axis orientation. Electrical measurements revealed that all of the deposited films are n-type. The best figure of merit can be achieved by using the precursors with 6at% of F. Results of this study show the F incorporation is one of the effective factors to optimize the FZO thin films. As a demonstration crystalline silicon-based solar cells were fabricated using FZO derived from this study.

Synthesis a Sol-Gel for Chemical Fiber Sensor

Sol–gel materials may found plenty of applications, e.g., as carriers for various substances, which can be exploited for sensing purposes or as drug releasing carriers. In this work, the fluorescence properties of two photosensitizers immobilized in silica based sol–gel materials were examined. Sol-gel derived silica possess many promising features, including room-temperature preparation procedure, porosity, chemical and physical stability. The material preparation procedure is described and practical remarks on silica-based sol-gels are included. It is reported that sol-gels with entrapped various molecules may be used in construction of implants and coatings with bioactive properties. It is shown how to exploit the sol-gel production route for construction of sol-gel coated fiber optic applicators for chemical sensor. We used a Sodium silicate(Na2 O3 Si) instead of the Trathyl Ortho Silicate (TEOS ) (Si (OC2 H5)4).We study the optical characteristics for this sample.

Synthesis a Sol-Gel for Chemical Fiber Sensor

Sol–gel materials may found plenty of applications, e.g., as carriers for various substances, which can be exploited for sensing purposes or as drug releasing carriers. In this work, the fluorescence properties of two photosensitizers immobilized in silica based sol–gel materials were examined. Sol-gel derived silica possess many promising features, including room-temperature preparation procedure, porosity, chemical and physical stability. The material preparation procedure is described and practical remarks on silica-based sol-gels are included. It is reported that sol-gels with entrapped various molecules may be used in construction of implants and coatings with bioactive properties. It is shown how to exploit the sol-gel production route for construction of sol-gel coated fiber optic applicators for chemical sensor. We used a Sodium silicate(Na2 O3 Si) instead of the Trathyl Ortho Silicate (TEOS ) (Si (OC2 H5)4).We study the optical characteristics for this sample.

New sol–gel processes in the synthesis of inorganic sorbents and ion exchangers based on nanoporous oxides and phosphates of polyvalent metals

The original competing-templating sol–gel method was proposed based on the idea that the formation of inorganic sols and gels always slower process than the formation of the corresponding precipitations; slowing down of solid phase formation (sol particles) can be realized by the competition with main reagents of the cations and anions added to one of starting precursors. This new sol–gel process can be conducted with water solutions only simplest salts, alkalis and acids without using chelating reagents. The date are also presented on the “oil-drop” and “air-drop” semi plant technologies for continuous sol–gel production of porous spherically granulated sorbents and inorganic ion exchangers such as amorphous titanium and zirconium phosphates. Here are represented also data about their porous structure and the role competing-templating triply charged cations (Al3+, Fe3+) in the ultra pores formation for selective sorption of heavy metals, radionuclides and uranium.

Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials

A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified through the attachment of carboxylic end groups (MPR), is used to tailor the morphological and optical properties of sol–gel synthesized silica materials. Silica microparticles are produced from alkoxide precursors in the presence of PFR or MPR resins, leading to a final material consisting of SiO2 globules entangled inside a polymerized resin matrix. Under appropriate experimental conditions, chemical bonds can be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds. The presence of PFR or MPR resins during the sol–gel production of silica microspheres allows to control: (i) the sizes of final SiO2 particles and (ii) the transparency or opacity properties of the final hybrid products. In this way, either opaque or transparent solid substrates can be obtained, depending on the amounts of reactants used to prepare the hybrid specimens. Solid MPR and SiO2/MPR samples were characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy to determine chemical and textural properties of the hybrid substrates. Under appropriate experimental conditions, chemical bonds could be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds.

Sol-Gel Production and XPS Study of Sodium-Vanadium Oxide Bronze β-Phase

A β-phase of sodium-vanadium oxide bronze thin film has been synthesized by using sol–gel technology from V2O5 and Na2SO4. The powders of these materials in suitable proportion were dissolved in hydrogen peroxide and heated up to 350 K for the dissociation of peroxide complexes. The obtained gel was deposited onto a metallic substrate and dried in air at room temperature. The produced xerogel was heated up to 580 K in air atmosphere for the removal of water from xerogel. Starting materials, xerogel, as well as a final product were investigated by means of X-ray photoelectron spectroscopy method. X-ray photoelectron spectra testify that the chemical bonds of vanadium, oxygen and sodium in the bronze differ from the similar bonds in the starting materials. The sulphur presence was detected in the xerogel but not in the final bronze composition.

Maltose and pectin assisted sol–gel production of Ce0.8Gd0.2O1.9 solid electrolyte nanopowders for solid oxide fuel cells

A novel sol–gel method has been developed for the production of high purity nanopowders of cerium gadolinium oxide (CGO, Ce0.8Gd0.2O1.9) solid solution using maltose as an organic chelating agent and pectin for gelation. The results of this investigation indicate that the final particle size of approximately 10 nm can be obtained after calcination of the predried gel at 500 °C for 2 hours in ambient air. An insight into the calcination process has been obtained by using simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). Powder X-ray diffraction (XRD) confirms that all samples are single phase cubic CGO powders with no trace of impurity. The mean crystallite sizes calculated from XRD analysis using the Rietveld refinement method agree with the morphological features observed by transmission electron microscopy (TEM). The nanopowders produced in this study exhibit negligible strain as indicated by the Rietveld refinement procedure. The nominal composition of CGO has been found to be in excellent agreement with that determined by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma-atomic emission spectrometry analysis (ICP-AES). The XRD and TEM analyses indicate that there is a significant influence of calcination temperature on the particle size which increases with increasing temperature for a fixed annealing time. This new sol–gel method is a cost effective, simple, environmentally friendly and non-toxic route for a large scale production of high purity single phase nanopowders of complex oxide functional ceramic materials at significantly low temperatures.

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO2 electrodes

The ZnO-modified TiO2 electrode was prepared by adding Zn(CH3COO)2·2H2O to the TiO2 colloid during the sol-gel production process, and was used in dye-sensitized solar cells (DSCs). The open circuit voltage (V OC) and fill factor (ff) of the cells were improved significantly. The performances of the ZnO-modified TiO2 electrode such as dark current, transient photocurrent, impedance, absorption spectra, and flat band potential (V fb) were investigated. It is found that the interface charge recombination impedance increases and V fb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO2 film.

The Sol–Gel Production of Bioceramics

Sol–gel synthesis is used for the fabrication of new materials with technological applications including ceramics for implants manufacturing, usually termed bioceramics. Many bioactive and resorbable bioceramics, that is, calcium phosphates, glasses and glass–ceramics, have been improved by using the sol–gel synthesis. In addition, the soft thermal conditions of sol–gel methods made possible to synthesize more reactive materials than those synthesized by traditional methods. Moreover, new families of bioactive materials such as organic–inorganic hybrids and inorganic compounds with ordered mesostructure can be produced. In hybrid materials, the inorganic component ensures the bioactive response whereas the organic polymeric component allows modulating other properties of the resulting biomaterial such as mechanical properties, degradation, etc. On the other hand, the sol–gel processes also allow the synthesis of silica ordered mesoporous materials, which are bioactive and exhibit – as an added value – a possible application as matrices for the controlled release of biologically active molecules (drugs, peptides, hormones, etc.). Finally, by combining the bioactive glasses composition with synthesis strategies of mesoporous materials, template glasses with ordered mesoporosity can be obtained. In this chapter, the advances that sol–gel technology has brought to the silica-based bioactive bioceramics are presented.

Production of High-Density Uranium Carbide Compacts for Use in Composite Nuclear Fuels

Composite nuclear fuel consisting of uranium carbide (UC) fuel microspheres dispersed in an inert matrix is one of the fuel forms being actively considered for use in gas-cooled fast reactors (GFRs). High-density UC electrodes were required for the production of fuel microspheres by the rotating electrode method as an alternate method to the sol-gel particle production route. These compacts (to serve as electrodes) were fabricated by the exothermic combustion synthesis reaction of uranium hydride and graphite powders. Ignition of combustion synthesis was then followed by solid-state sintering at different temperatures of 1521, 1779, and 1929°C. During the course of testing the electrodes for microsphere production, it was found that the structural integrity of the electrodes and thus their suitability for microsphere production depended on the microstructural characteristics of the electrodes. Those produced at higher temperatures (1929°C) had higher densities (86.6% theoretical density) and lower open porosities (2.3%) and were shown to withstand the mechanical forces and thermal stresses imposed by this microsphere production method. The processing conditions were chosen to evaluate sintering characteristics of UC and to the extent possible to find the lowest possible process temperature. Here it is understood that the intended future GFR fuel form should involve recycled fuels including minor actinides (MAs). Concern over MA volatility in high-temperature processes thus motivated investigating the effects of lower processing temperatures. It was deduced from this study that a delicate balance exists between the processing parameters, the microstructural characteristics of the electrodes, and microsphere production.

Sol-Gel Production of Bioactive Nanocoatings for Medical Applications. Part II: Current Research and Development

Over the years, the use of hydroxyapatite as coatings for medical devices and drug-delivery systems has gone through a revolution - from being a rarity to being an absolute necessity. Without these coatings, many medical implants and devices would never reach their true potential in their intended applications, such as in the dental and orthopedic fields. Coatings of hydroxyapatite are often applied to metallic implants to alter their surface properties. The aim of this article is to present an evaluation of the published work regarding current research and applications and to review the methods used for the production of hydroxyapatite nanocoatings.

Synthesis and characterization of titanium dioxide optical films by sol–gel processes

AbstractThe main purpose of this study is to synthesize the front panel of monitor with a high refractive index optical film. Our experiment uses titanium dioxide nanoparticles mixed with methyl methacrylate (MMA), 2‐hydroxyethyl methacrylate (2‐HEMA), and tri(ethylene glycol) dimethacrylate (TEGDMA) of the wet type and economical sol–gel production process. Our product has a superior mechanical, thermal, and optical properties was demonstrated by Fourier transform infrared spectrum (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UV/visible spectrum, and Spectro Ellipsometer. In addition, we found the surface of the two series of thin film with the organic and inorganic high refractive index (TiO2) mixed materials, has high transmittance for visible light above 90%, refractive index <1.65 and the hardness test 6H. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2271–2280, 2007

Sol-Gel Production of Bioactive Nanocoatings for Medical Applications. Part 1: An Introduction

Coatings offer the possibility of modifying the surface properties of surgical-grade materials to achieve improvements in performance, reliability and biocompatibility. Sol-gel-derived coatings demonstrate promise owing to their relative ease of production, ability to form a physically and chemically pure and uniform coating over complex geometric shapes and potential to deliver exceptional mechanical properties owing to their nanocrystalline structure. Other advantages unique to sol-gel include the production of a homogeneous material, since mixing takes place on the atomic scale, and its relatively low processing temperature avoids decomposition of the coating materials and limits the damage to metallic substrate materials as a result of exposure to elevated temperatures. A range of materials can be adapted easily for a number of biomedical and engineering applications.

Development of hybrid materials consisting of SiO 2 microparticles embedded in phenolic-formaldehydic resin polymer matrices

A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified by the incorporation of carboxylic end groups (MPFR), is used to influence the morphological and optical properties of sol-gel synthesized SiO 2 materials. Silica microparticles are formed from the hydrolysis of silicon alkoxide solutions in ethanol and in the presence of polymerizing PFR or MPFR resins, hence rendering a final product consisting of SiO 2 globules entangled inside a resin network. Under appropriate experimental conditions, chemical unions are established between silanol groups anchored on the surface of the SiO 2 particles and MPFR carboxylic chains, to provide SiO 2/MPFR core-shell compounds. The presence of PFR or MPFR resins during the SiO 2 sol-gel production influences: (i) the size of SiO 2 particles; and (ii) the transparency, translucency or opacity properties of the final hybrid products. Either one of the latter optical conditions is established by the amounts of reactants used to prepare a given hybrid specimen. FTIR, TGA and SEM are employed to determine the chemical and textural properties of SiO 2/PFR and SiO 2/MPFR solids. Results confirmed the existence of chemical bonds at the interface between silica and MPFR resin, as well as superior properties of these hybrid materials with respect to pure PFR or MPFR polymerized materials.

Examination of sol-gel production repeatability by statistical pattern recognition methods

We examine the repeatability of the sol-gel production pro- cess. Methods based on statistical pattern recognition are used to evalu- ate microscopic images of sol-gel matrices. The applied classification is a two-steps scheme: dimensionality reduction of the data and cluster analysis. Two methods of dimensionality reduction and five methods of cluster analysis are used. We show that the repeatability varies between 82 and 93.77%. The obtained results demonstrate that the molar ratio R of the number of solvent moles to the number of substrate moles influ- ences the stability of sol-gel materials, thus enabling us to reach a higher repeatability in the production process in the case of sol-gel produced with the addition of detergent. © 2003 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1555996)

Tem Observation of Metal-Loaded Carbon Aerogels Prepared by an Ion-Exchange Method

Cu-loaded carbon aerogel was prepared by soaking sol-gel production, obtained from K-salt of 2,4-dihydroxybenzoic acid, into Cu(NO 3 ) 2 solution. XPS measurement demonstrated that Cu concentration is higher in the outside region of bulk samples, indicating that Cu may be incorporated through an immersing process rather than ion-exchanging. TEM observation showed that, like an aerogel sample with K ions, Cu-loaded organic aerogels had porous texture in which gel particles about 20-30 nmφ were interconnected with each other. Metal-loading process used in this study was considered as a promising method to disperse metals without changing original structure of carbon aerogels.

Fast, Radiation‐Hard Scintillating Detector: A Potential Application for Sol‐Gel Glass

To meet the present‐day rate and radiation dose requirements, one would like to have a scintillator with the high radiation resistance of pure silica glass and the short fluorescence decay time of organic fluors. The new technology of sol‐gel glass production permits the preparation of organic/inorganic composite materials by doping the silica gels with organic fluors. The procedure of production of monolithic organic/inorganic composite materials, such as 2‐(4‐tertbutylphenyl)‐5‐(4‐biphenylyl)‐1,3,4‐oxadiazole/SiO2, p‐terphenyl/SiO2, p‐quaterphenyl/SiO2, and 3‐hydroxyflavone/SiO2, and the associated characterization techniques are described. The efficiency of light production, the light attenuation, the time width of light pulse, and the radiation resistance of the scintillating sol‐gel glass are discussed. Preliminary results indicate that this technical advance will permit the creation of new materials with potential application such as particle detectors which are both radiation hard and fast.

Sol-gel production of titanosilicate glass-ceramics for nuclear waste immobilization

Titanosilicate glass-ceramics designed for radioactive waste immobilization have been fabricated by a sol-gel route. Calcination and wet-milling, followed by drying, cold-pressing and sintering, produced material having very nearly the theoretical density. A maximum sintering temperature of 900° C was used, which is considerably less than the temperature of ⩾ 1300° C required for production by melting. The materials were characterized by differential thermal analysis, X-ray diffraction, infrared spectroscopy and scanning electron microscopy.