Hybridization matrices

In the case of good adhesion between fiber and matrix, brittle fracture of the fibers is observed. A further disadvantageous behavior was found in composites used in ultracentrifuges running at high temperature (60). Internal fracturing destroyed the integrity of the matrix, and loss of matrix as carbon dust was observed. These observations led to systematic studies of carbon/carbon composites with hybrid matrices (34). 

Carbon/Carbon Composites with Hybrid Matrices... 

It is hoped that the concept of hybrid matrices will open new fields of application for carbon/carbon composites. 

Innocenzi, P., Brusatin, G., Abbotto, A., Beverina, L., Pagani, G.A., Casalboni, M., Sarcinelli, F., Pizzoferrato, R. Entrapping of push-pull zwitterionic chromophores in hybrid matrices for photonic applications. Journal of Sol-Gel Science and Technology, 26, 967-970 (2003)... 

The adsorption affinities of the hexagonal zirconia matrix toward Ni(II) and Cu(II), Cu(II) >>Ni(II), are opposite to those observed for LS samples [6] Ni(II) > Cu(II) (in this case the respective chlorides were used for both Ni and Co). This indicates that the nanostructure of the templated substrate can exert remarkable effects not only on the total amount of adsorbed cations, but also on the selectivity of the adsorption process. It could be inferred that hexagonal nanostructures, as well as lamellar ones, do not favor cobalt adsorption (or the adsorption of other cations with coordination number 6, forming octahedral compounds). However, lamellar nanostructures favor Ni(II) adsorption, whereas Cu(II) adsorption is favored by templated hybrid matrices with hexagonal nanostructures. 

Hereafter, the six hybrid matrices will he named as MoDMGl, MoDMG2, Mocaffl, Mocaff2, and MoRODB from (a) to (e), respectively. 

The spectrometer XRD patterns for the hybrid matrices are shown in F. 6.13. In the M0O3 diffraction pattern (not shown), peaks at 14.8° and 29.9° are associated with the 001 and 002 diffraction planes. Taking into account the 001 diffraction peak position, the interlayer distance can be calculated as 0.69 nm. As can be verified by inspection of the XRD patterns, there is no intercalation (the interlayer distance is unchanged after reaction) in the hybrid matrices. 

The morphology of the oxide grains was affected by the reaction processes, and, as illustrative examples, the SEM micrographs for the pure oxide and MoDMG2 are shown in Fig. 6.14. Due to the very intense infrared bands form M0O3 the infrared spectra for the hybrid matrices (not shown) are not conclusive or indicative of the reaction processes. 

Table 6.3 Thermogravimetric data summary for M0O3 hybrid matrices...

The TG and derivative curves for M0O3 and the synthesized hybrid matrices are shown in Fig. 6.19. 

A new dimension in sol-gel chemistry has been opened up with sol-gel alkoxide precursors consisting of functional organic groups [R -Si(OR)3] or organic spacers directly bound to siloxanes [(RO)3Si-R -Si(OR)3j [19-21]. Figure 2 shows some examples of the precursors with trialkoxyl silanes attached to alkyl and phenyl groups. The hybrid matrices can be readily prepared by the cocondensation of these... 

Other types of organic molecnles nsed as sol-gel dopants to form NLO materials are phthalocyanines, porphyrins and fnllerenes. For the phthalocyanines entrapped in hybrid matrices prepared from trifnnctional silane precnrsors , a very good stability was observed. Porphyrins doped in alnminosUicate gels showed a concentration-dependent nonlinear absorption behavior ". Fnllerenes have recently incorporated into silica matrices of high porosity (aerogels), also showing a concentration effect. 

In this chapter we will shortly summarize the nonlinear optical properties of macromolecular systems and some of the main experimental techniques for their optical characterization. Some basic optoelectronic patterns will be reported in order to give a brief account of the advances in the realization of active waveguide systems and telecommunication devices based on organic materials. The main optoelectronic devices based on nonlinear optical properties of chromophores in polymeric and hybrid matrices will be illustrated. In particular Mach-Zehnder modulators, microring resonators, switches and wavelength filters will be reviewed. 

Furthermore, we mentioned in Hybrid Organic/inorganic Routes of this chapter that in the case of hybrid matrices, crack-free thick films of 1 fj,m or more in thickness can... 

Figure 7-9. Schematic structure of the precursors used in the synthesis of type IIHPS hybrid matrices.

Effect of the Polarity and the Degree of Inorganic Crosslinking of the Hybrid Matrices on the Barrier Properties... 

One of the most attractive properties of the sol/gel process is its unique low-temperature processing capability. The soft-chemistry characteristic of the sol/gel route provides opportunities to develop molecular level organic-inorganic materials wherein chemical modification allows physical encapsulation of biological molecules in these hybrid matrices. Another key property of sol/gel-derived materials is die freedom to tune the properties of the micro environment where the organic- or bio-molecules are confined and/or immobilized. The scale of porosity can be tailored from the nano to the micro scale for specific applications. 

Polymer alloys may be considered as hybrid matrices or binders of the second generation because they themselves are composite materials. The processes... 

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