Si 4 precursor

The low temperature ALD process for hafnium silicate films using HfCl2[N(SiMe3)2]2 and H2O was modified to improve the film properties by two different methods. With hydrogen peroxide, the silicon content in the film increased to Si/(Hf+Si)=0.2 at 2001 and the impurity levels decreased due to its strong oxidation effect. By introducing TBOS as an additional Si precursor, the silicon content in the film increased to Si/(Hf+Si)=0.5 at 200 °C and the hafiiium silicate films became fully oxidized with O/(Hf+Si)=2.0. 

A new preparation of primary and secondary stibines by hydrolysis (methanolysis) of the corresponding silyl compounds was recently reported (equations 24 and 25). This seems to be a useful method as the Si precursors are readily available from the corresponding chlorides and Me3SiCl/Mg in THF. ... 

Fig. 13. Liquid polymer infiltration route for fabrication of SiC composite structures fi-om Si-precursors [fi om 251]...

Fig. 40.3 Morphology of the ECM-made S1O2 particles, (a) Si Precursor is Si02 sols (b) Si precursor is hexamethyldisiloxane. The powder in (a) consisted of submicron to micron-sized porous particles with openings on the surface whereas in (b) only nanoparticles of less than SO nm in diameter were observed. (Reprinted fiorn [4] with permission. Copyright 2003 Springer)...

Just as for the analyte, the choice of product ion for MRM detection of the SIS requires the same considerations. In addition, usually the m/z value of the SIS precursor ion is different from that of the analyte, so there is no problem if the best choice of product ion turns out to be the same for both. This conclusion does not apply if there is appreciable overlap between the isotopic distributions of anal5h e and SIS, i.e. cross-contributions between the precursor ions (Section 8.5.2c), since the latter circumstance requires uniquely different product ions for there to be any hope of distinguishing the two. It is good practice to make a choice of product ion as the primary candidate for the MRM method, but also to choose one or two others as back-up candidates that should be independently optimized (collision energy etc.). Then, during subsequent stages of the overall method development, continue to use aU of these candidate ions until the final optimization, as an insurance against unforeseen selectivity problems with the primary candidate for the real-world samples. 

Madler et al. [127] carried out synthesis of stable ZnO nanocrystallites down to 1.5 nm in diameter by spray combustion of Zn/Si precursors. These crystallites exhibited a quantum size effect a blue shift of light absorption with decreasing crystallite size and the wet-phase-made ZnO QDs nicely followed a correlation between particle size and optical energy gap from the literature. 

As already underlined in the first part of the text, the mesoporosity can be controlled through the sol-gel process conditions, for example, when a two-step catalysis is applied to standard alkoxides such as TMOS [36, 82, 103]. If these simple tetia-alkoxides are mixed with a more exotic functionalized Si precursor, differences in the hydrolysis and condensation rates of the two precursors may drastically influence the final texture of the material. For example, when the functionalized precursor carries basic moieties such as an amine in 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS), 3-aminopropyltriethoxysilane (AES), or 3-aminopropyltrimethoxysilane (AMS), these functionalized precursors can act as nucleation centers for condensation and can lead to generation of large macropores [104, 105]. 

In our laboratory, we have studied recoil Si reactions with butadiene by using PF3 as the Si precursor. From the formation of [ Si]-l,l-difluorosilacyclopent-3-ene as a product, we reasoned that SiFj was formed through stepwise F abstraction by recoil Si atoms as shown in equations (8) and (9). An insertion-decomposition mechanism similar to that shown in equation (7) is also possible. 

Gel Type ol gels" Al-precursor/ Solvent Si-precursor/ solvent SSAs B.E.T (mVg) EDX analysis AI203/SI02 (Virt%)... 

CEPC triblock polymers were prepared by a group at the Shell Oil Company [21]. The SIS precursor polymers were prepared by sequential anionic... 

A procedure to synthesize ordered mesoporous silica denoted COK-12 under mild conditions is presented. A P6m ordered mesoporous silica with uniform pores is synthesized at room temperature and quasi neutral pH. The synthesis makes use of P123 triblock copolymer in an aqneons citric acid / sodium citrate buffer solution and sodium silicate as Si precursor. Synthesis examples of COK-12 materials are presented and the materials characterized using small angle X-ray scattering, nitrogen sorption, electron microscopy. 

---