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Gel Precursor (gel + precursor)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Dielectric Properties of a Printed Sol,Gel Matrix Composite,

ADVANCED ENGINEERING MATERIALS, Issue 5 2010
Tobias Lehnert
Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol,gel derived network. The exemplary optimization of the properties by varying the sol,gel precursor illustrates the potential of sol,gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response. [source]

Tuning and Transcription of the Supramolecular Organization of a Fluorescent Silsesquioxane Precursor into Silica-Based Materials through Direct Photochemical Hydrolysis,Polycondensation and Micropatterning

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009
Xavier Sallenave
Abstract A new fluorescent silsequioxane precursor with tuned optical properties and controlled aggregation properties is designed. The two cyclohexyl moieties introduced in the molecular structure allow the formation of very good quality films. The J-aggregated structure is transcribed into the solid by photoacid-catalyzed hydrolysis,polycondensation. Aggregation of the chromophores is reduced and highly fluorescent materials are obtained. The photoacid generator lies on the surface of the homogeneous layer of the sol,gel precursor. This phase separation presents several advantages, including UV protection of the chromophore and easy removal of the PAG. The first example of chemical amplification in the photolithography of the conjugated silsesquioxane precursor is demonstrated. As hydrolysis,polycondensation could be achieved in a controlled way by UV exposure, chemically amplified photolithography is achieved by irradiating a composite film (,110,nm thick) on silicon wafer by using a copper TEM grid as shadow mask. The pattern is produced uniformly on a miscroscopic scale of 3,mm, the photopatterned pixels remaining highly fluorescent. The sizes of the photolithographed pixels correspond to the sizes of the rectangular holes of the 300,×,75 mesh grid (hole: 63,<$>,<$>m,×,204,<$>,<$>m). [source]

Anatase and Rutile TiO2 Macrocellular Foams: Air,Liquid Foaming Sol,Gel Process Towards Controlling Cell Sizes, Morphologies, and Topologies,

ADVANCED MATERIALS, Issue 1 2005
F. Carn
Titania foams (see Figure) can be produced using a non-static air,liquid foaming sol,gel process where nitrogen is bubbled through a mixture of a surfactant and a sol,gel precursor. Either anatase or rutile phase mesoporous titania foams are produced upon thermal treatment. Macroscopic cell morphologies can be tuned by changing the air-to-liquid-foam ratios and the size of the nitrogen bubbles, while wall topologies can be varied by changing surfactant. [source]

A Covalently Interconnected Phosphazene,Silicate Hybrid Network: Synthesis, Characterization, and Hydrogel Diffusion-Related Application,

ADVANCED MATERIALS, Issue 6 2003
Y. Chang
Sol,gel precursors of poly[bis(methoxyethoxyethoxy)phosphazene] have been synthesized by incorporating triethoxysilane in the polymer side groups. Studies of the water-swelling (see Figure, dry left, water-swollen, right) behavior and dye-release of the hybrid network indicate that the polyphosphazene,silicate network has potential as a biomaterial and for use in both passive and responsive membranes. [source]

Kinetic Studies of Mullite Synthesis from Alumina Nanoparticles and a Preceramic Polymer

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008
Flavio Griggio
The crystallization kinetics of mullite formation in a diphasic precursor consisting of a silicone resin filled with commercial ,-alumina nanoparticles (15 nm mean particle size, specific surface area of 100 m2/g), heated in air from 1250° to 1350°C, was studied by X-ray diffraction. Transitional ,-alumina and amorphous silica from the pyrolysis of the preceramic polymer exhibited a remarkable reactivity, as demonstrated by a very low incubation time (from 500 s at 1250°C to 20 s at 1350°C), a high mullite yield (about 80 vol%, after 100 s at 1350°C), and a low activation energy for nucleation (677±60 kJ/mol). The activation energy values found were lower than those reported previously for other diphasic systems, including sol,gel precursors. Besides the high specific surface of nanosized ,-alumina particles, the low energy barrier could be attributed to the highly reactive silica deriving from the oxidation of Si,CH3 bonds in the silicone and to the homogeneous dispersion of the nanosized filler inside the preceramic polymer. Furthermore, the possibility of applying plastic shaping processing methods to the mixture of a preceramic polymer and nanosized filler makes this approach particularly valuable, in comparison, for instance, with sol,gel based alternatives. [source]