Effect of metal cations on the kinetics of formation and structure of gels formed during the acid hydrolysis of Tetraethoxysilane

The hydrolysis and polycondensation of tetraethoxysilane are studied at low pH values in the presence of doping additives (cations of various metals). The period of gel formation is found via viscometry, and the activation energy is calculated. It is shown that the doping additives affect both of these parameters. A change in particle size during the hydrolytic polycondensation of tetraethoxysilane in the presence of metal cations is studied via dynamic light scatterin

Novel cerium-containing layered double hydroxid

Nickel-aluminum-cerium layered double hydroxide (LDH) in carbonate form was successfully synthesized by co-precipitationfollowed by hydrothermal treatment. The predetermined molar percentage was the following: Ni²+/( Al³+ + Ce³+) = 3 and Ce³+/( Al³+ + Ce³+) = 0.05. The XRD data indicated that the cerium-containing single-phase product with a hydrotalcite structure could be obtained by hydrothermal treatment for 48 h at 120 °

Eco-friendly iron-humic nanofertilizers synthesis for the prevention of iron chlorosis in soybean (Glycine max) grown in calcareous soil

Iron deficiency is a frequent problem for many crops, particularly in calcareous soils and iron humates are commonly applied in the Mediterranean basin in spite of their lesser efficiency than iron synthetic chelates. Development and application of new fertilizers using nanotechnology are one of the potentially effective options of enhancing the iron humates, according to the sustainable agriculture. Particle size, pH, and kinetics constrain the iron humate efficiency. Thus, it is relevant to understand the iron humate mechanism in the plant–soil system linking their particle size, characterization and iron distribution in plant and soil using 57Fe as a tracer tool. Three hybrid nanomaterials (F, S, and M) were synthesized as iron-humic nanofertilizers (57Fe-NFs) from leonardite potassium humate and 57Fe used in the form of 57Fe(NO3)3 or 57Fe2(SO4)3. They were characterized using Mössbauer spectroscopy, X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS), transmission electron microscopy (TEM) and tested for iron availability in a calcareous soil pot experiment carried out under growth chamber conditions. Three doses (35, 75, and 150 mmol pot-1) of each iron-humic material were applied to soybean iron deficient plants and their iron nutrition contributions were compared to 57FeEDDHA and leonardite potassium humate as control treatments. Ferrihydrite was detected as the main structure of all three 57Fe- NFs and the plants tested with iron-humic compounds exhibited continuous long-term statistically reproducible iron uptake and showed high shoot fresh weight. Moreover, the 57Fe from the humic nanofertilizers remained available in soil and was detected in soybean pods. The Fe-NFs offers a natural, low cost and environmental option to the traditional iron fertilization in calcareous soilsThe Russian Science Foundation (16-14-00167), the Russian Foundation for Basic Research (18-29-25065), and the Spanish Ministry of Science and Innovation (AGL2013-44474-R) have financially supported this research

Состояние палладия и меди в свежеприготовленном катализаторе PdCl2−CuCl2/γ−Al2O3 низкотемпературного окисления монооксида углерода

The EXAFS/XANES, XRD, SEM methods were used for examination of freshly prepared low temperature carbon monoxide oxidation in air catalyst PdCl2-CuCl2/γ-Al2O3 active components states. The Cu2Cl(OH)3 phase with particle size 100-300 nm and tetrachloropalladat particles were identified on γ-Al2O3 surface. According to EXAFS data one of the palladium chloride bonds is longer then another ones. There is no direct interaction between palladium and copper, i.e. there is no common active center including palladium and copper on the γ-Al2O3 surface responsible on the low temperature carbon monoxide oxidation in air.Методами рентгеновской спектроскопии поглощения (EXAFS/XANES), порошковой рентгеновской дифрактометриии, растровой электронной микроскопии (РЭМ) изучено состояние активных компонентов свежеприготовленного катализатора PdCl2−CuCl2/γ−Al2O3 низкотемпературного окисления монооксида углерода в воздухе. Показано, что на поверхности γ−Al2O3 находится кристаллическая фаза Cu2Cl(OH)3 с размерами частиц 100-300 нм и палладий в аморфном состоянии. По данным EXAFS, локальное окружение палладия - четыре атома хлора, образующие плоский квадрат с одной более длинной связью Pd-Cl. Прямого контакта между палладием и медью не обнаружено, то есть, на поверхности катализатора отсутствует единый активный центр, ответственный за проведение реакции окисления монооксида углерода кислородом

PhysSoSt5_09LebedevLO

Abstract -The local environment of Pb impurity atoms in BaTiO 3 , SrTiO 3 , and CaTiO 3 crystals was studied by XAFS technique. It is shown that, in both polar and nonpolar phases of BaTiO 3 and in SrTiO 3 , the Pb atoms are displaced from the A lattice sites by ~0.15 Å; in CaTiO 3 this displacement is absent. Large values of DebyeWaller factors (0.05-0.10 Å 2 ) for the atoms in the first shell of Pb observed in all the three crystals indicate the distortion of the oxygen environment of Pb atoms. The appearance of these features was explained by the fact that the Pb-O chemical bond has a noticeable covalent component and a Pb atom can form strong bonds only with four of the 12 surrounding oxygen atoms. The obtained data were used to determine the main factors responsible for the occurrence of ferroelectric phase transition in SrTiO 3 and CaTiO 3 and for the increase of the Curie temperature of BaTiO 3 when it is doped with Pb