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Hybrid Sol (hybrid + sol)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Improved Aging Characteristics of NTC Thermistor Thin Films Fabricated by a Hybrid Sol,Gel,MOD Process

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006
Dmitry A. Kukuruznyak
Negative temperature coefficient thermistor oxide thin films with improved aging characteristics are described. Better thermal stability has been achieved by incorporating sol,gel techniques with metallo-organic decomposition methods. A compositional range was identified whereby borosilicate may incorporate into the thermistor oxides, forming nanocomposites showing thermistor electrical characteristics. Thermistor thin films, with composition Ni0.48Co0.24Cu0.6Mn1.68O4·0.22SiO2·0.15B2O3 were deposited onto glass substrates from a solution containing organic transition metal salts, tetraethyl orthosilicate and triethyl borate. Electrical resistance measurements verified characteristic thermistor behavior. Nanocomposite thin films exhibited a factor of four improvement as compared with pure oxides after aging at 150°C for 500 h. [source]

Real-time Fourier transform infrared study of the free-radical ultraviolet-induced polymerization of a hybrid sol,gel.

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2003

Abstract Free-radical photocurable hybrid sol,gel materials have gained special interest during the last decades. Compared to thermally processed materials, they present the advantages of fast curing, low energy consumption, and spatiotemporal control of the reaction. Although comprehension of the photochemical step is fundamental, little is known about the characteristic of photochemistry in this kind of material. Real-time Fourier transform infrared spectroscopy was used to study the photopolymerization of a hybrid sol,gel upon ultraviolet irradiation. Various photoinitiator systems were tested for their efficiency in inducing the polymerization of pendant polymerizable moieties anchored on a partially condensed silicate network. The presence of O2 and the nature of the polymerizable function were shown to be crucial factors in the photoinduced process. The effects of the photoinitiator concentration and light intensity were also studied. These results were explained in terms of classical kinetic models developed for all-organic photopolymers to point out the distinctive aspects related to the use of photoinitiated polymerization in hybrid sol,gel materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 831,840, 2003 [source]

Real-time Fourier transform infrared study of free-radical UV-induced polymerization of hybrid sol,gel.

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2003

Abstract Free-radical photocurable hybrid sol,gel materials have gained special interest. They are becoming more and more widely used for applications in coatings, optics, sensors, catalysis, and so forth. The photochemical step is a fundamental step in the elaboration of this kind of hybrid sol,gel. However, little is known about the specifics of the photochemistry in this material. The relation between the organic and the inorganic part is investigated. Hydrolysis and condensation reactions were characterized by 29Si NMR. A precise description of the material before irradiation is of paramount importance to understand photoinduced phenomena. Real-time Fourier transform infrared spectroscopy was used to examine the photopolymerization of hybrid sol,gel under UV irradiation. UV photopolymerization occurred efficiently in hybrid sol,gel although inhibition of free-radical polymerization by molecular oxygen was pronounced. Important structural modifications during irradiation were also measured. They concern both inorganic and organic parts of the hybrid material. The condensation state of the silicate network was of crucial importance. The presence of the silicate backbone did not limit the final conversion ratio. On the contrary, photopolymerization occurred more efficiently for systems with a higher degree of condensation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 716,724, 2003 [source]