Nanocomposite organomineral hybrid materials. Part 3

Abstract

PART III ExtEndEd AbstrAct:The paper addresses the issues of alkoxide method of sol-gel synthesis and non-hydrolytic method of sol-gel synthesis and colloidal method of sol-gel synthesis. The authors also consider an alternative approach based on the use of soluble silicates as precursors in the sol-gel technology, of nanocomposites. It was shown that nanocomposites can be produced through aerogels. The paper also analyzes the mixing technologies of nanocomposites preparation. It has been demonstrated the possibility to change the types of nano-phase which is used for obtaining nanocomposites in different approaches. Various models of packaging spherical, fibrous and layered nanoparticles, introduced into the structure of the nanocomposite, in the preparation thereof were examined.Key words: Nanocomposites, sol-gel synthesis, soluble silicates, metal alkoxide, sols, gels, aerogels, packing of spherical nanoparticles, packing of fibrous nanoparticles. THE RESULTS OF THE SPECIALISTS' AND SCIENTISTS' RESEARCHES MAchinE-rEAdAblE inforMAtion on cc-licEnsEs (htMl-codE) in MEtAdAtA of thE pApErThe first and the second parts of the paper are published in the issues 1/2016 and 2/2016. INFLUENCE OF VARIOUS FACTORS ON STRUCTURE AND PROPERTIES OF HYBRID MATERIALS Packing of spherical nanoparticles of the fillerThe system of pores in a solid is entirely determined by the nature of the packing of the primary particles. For example, when the hexagonal closest packing of spherical particles between disposed in a plane, the three nearest tetrahedral cavities is octahedral cavity. In subsequent accretions over the octahedral cavity occurs again octahedral cavity. Superimposed on top of each other octahedral cavities form channels that permeate the whole body of matter in the orthogonal directions [151]. In cubic structures of the closest packing may also indicate the formation of interconnected channels. In the package of this type the void volume is 25.95%. From here it is possible to calculate the bulk density of the material (ρ):, where: ρ k -crystallographic density of the material used as a basis. L -void fraction in the structure of the package. INTERNATIONAL EXPERIENCE 18http://nanobuild.ruIf the lightest of refractory materials has crystallographic density close to 3 g/cm 3 , the bulk density of the product with the densest packing is 2.2 g/cm 3 . From here, to obtain a materials with a bulk density less than 0.5 g/cm 3 , it is necessary to achieve a greater porosity of 83%.Let's try to analyze what kind of particle packing can achieve the desired porosity.Typically with decrease in the coordination of number of particles packed in the packaging structures of particles increases the pore volume. In the case of the densest packings, the coordination number of the package is 12. Consider the following options for the coordination numbers of the package. Classically, such a packing density was 74%, respectively; the porosity of such package is 26%. For monodisperse materials denser packaging does not happen.The coordination...

Silicon mitigates iron deficiency in two energy cane cultivars by modulating physiological and nutritional mechanisms

“…This fact was evidenced in this research because the supply of Si induced an average Si content of 10.83 and 10.48 g kg -1 in cultivar VX2 and 11.91 and 12.35 g kg -1 in cultivar VX3 for the Fe sufficiency and deficiency conditions, respectively. The optimal uptake of Si by plants was also due to the applied solution at an adequate concentration (2.5 mmol L -1 ), which avoided the polymerization that occurs when Si is found at concentrations above 3.0 mmol L -1 ( Birchall, 1995 ), in addition to the acid pH of the nutrient solution used in the experiment that resulted in the production of monomeric species of Si (H 4 SiO 4 ) ( Kudryavtsev and Figovsky, 2016 ), favoring its uptake.…”

“…However, in an alkaline solution, Si species predominates in the form of monovalent (H 3 SiO 4 - ) and divalent (H 2 SiO 4 -2 ) anions. These monomeric species can be absorbed, mitigating the deficiency of Fe, in case the concentration is maintained up to 3 mmol L -1 of Si, considering that all monomeric species, regardless of pH value, induce the formation of polysilicon acid forming silanol groups (Si-O-Si) with polymerization, and are no longer absorbed by plants ( Kudryavtsev and Figovsky, 2016 ).…”

“…Fifteen Si fertirrigation events were performed considering 4-days intervals, starting 10 days after full sprout emergence (DAE) ( Figure 1 ), by applying 10 mL per seedling via substrate and 1.5 mL per seedling via foliar spraying, using a hand sprayer. The pH value of the solution containing fertirrigated Si was adjusted to 5.5 ± 0.2, in order to increase monomeric Si species in the solution, which is the absorbable form of the element by plants ( Kudryavtsev and Figovsky, 2016 ). The amount of potassium present in the Si source was balanced in treatments that did not have the element, using a KCl solution (1.0 mol L -1 ), applied in the roots and leaves in the seedling production phase and via roots after transplanting.…”