scholarly journals Research and simulation of hydrated alumina homogeneous precipitation and its application to obtain a carrier for catalysts in the petrochemical industry

2019 ◽  
Vol 4 (2) ◽  
pp. 72-79
Author(s):  
Pavel Kudryavtsev
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Colloidal Particles ◽  
Specific Model ◽  
Precipitation Process ◽  
Homogeneous Precipitation ◽  
Dissociative Mechanism ◽  
Hydrated Alumina ◽  
Hydrolytic Precipitation

The results of studies of the process of hydrated alumina homogeneous precipitation were presented in this work. The variants of this process are considered. The most convenient embodiment of this process is the precipitation of hydrated alumina from its salts with the use of auxiliary substances, such as urea. Urea hydrolysis allows a homogeneous precipitation process under the most mild conditions. It is shown that the process of hydrolytic precipitation in the aluminum salt-urea system proceeds according to the dissociative mechanism SN1. This article analyzes the regularities of precipitation of solid colloidal particles of hydrated metal oxides on the surface of various substrates. Two models of this process are proposed. The proposed α-model is a process of continuous nucleation of interaction centers, at random points of a free surface throughout the process. The proposed β-model provides for the instantaneous nucleation of these centers when they are randomly distributed over the entire surface of the substrate. Based on the proposed models, the average values of the following values are calculated: the thickness of the gel film; its roughness and specific surface area. The calculations carried out in the article showed that these parameters are universal functions of the degree of filling of the surface and do not depend on the specific model of the mechanism of the process. Studies have been conducted on the use of homogeneously precipitated aluminum hydroxide as a binder in the preparation of porous materials. The resulting materials have a developed specific surface area and porosity.

scholarly journals Impact of Agromeliorative Measures on the Specific Surface of Soil

2020 ◽  
Vol 6 (10) ◽  
pp. 135-142
Author(s):  
S. Gurbanov
Keyword(s):  
Soil Fertility ◽  
Physical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sandy Soil ◽  
Colloidal Particles ◽  
Soil Layer ◽  
First Year ◽  
Special Surface

The article is devoted to the study of the regularity of changes in the specific surface of soil under the influence of agromeliorative measures, mainly irrigation and agrotechnical works carried out in the gray-brown soils of the Absheron Peninsula of Azerbaijan. Based on four years of experiments, it was determined that changes occur in the specific surface of the soil in the plowed layer as a result of the agromeliorative measures taken. Thus, a decrease in the specific surface area was observed in the 0–20 cm soil layer, and an increase in the specific surface area was observed in the 20–40 cm soil layer. In the first year of the experiments, the value of the average specific surface in the 0–20 cm soil layer was 3,098–3,988 cm2/g, and in the 20–40 cm soil layer it was 1,056–3,567 cm2 /g. However, after four years, the value of the special surface was 1,949–3,340 cm2/g in the 0–20 cm soil layer and 3,290–5,023 cm2/g in the 20–40 cm layer. The increase in the specific surface area in the lower layers of the soil is due to the gradual washing of dust, silt and colloidal particles from the plow layer to the lower layers. The reduction of the specific surface in the topsoil leads to the degradation of the topsoil, the deterioration of the water-physical properties, the formation of compaction below the topsoil, and ultimately the reduction of soil fertility. The article makes specific suggestions to prevent this process. It was also identified based on the calculations that the specific surface area of the soil, rich in silt, dust and colloidal particles, is many times larger than the specific surface area of sandy soil. The specific surface area of colloidal silt is 43,000 times larger than the specific surface area of dust and 130,000 times larger than the specific surface area of sand.

Synthesis and Characterterization of Flower-Like NiO Nano-Architectures by Homogeneous Precipitation

2010 ◽  
Vol 434-435 ◽  
pp. 554-557 ◽  
Author(s):  
Ling Hong Luo ◽  
Ye Fan Wu ◽  
Fei Wei ◽  
Ji Jun Shi ◽  
Liang Cheng
Keyword(s):  
Specific Surface ◽  
Porous Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Average Diameter ◽  
Hexagonal Structure ◽  
Homogeneous Precipitation ◽  
Self Assembled ◽  
Xrd Patterns

Flower-like NiO powders with nano-architectures, self-assembled nano-sheets, were synthesized using Ni (NO3)2•4H2O and urea in mix solvents of ethanol and water by homogeneous precipitation. XRD patterns showed that the NiO powders were of hexagonal structure. FESEM and TEM confirmed that the average diameter of the flower-like NiO was 10μm, and the ultra-thin nano-sheets had micro-porous structure, with the thickness less than 100nm and the size of 2μm×3μm. Specific surface area (BET) was around 130.92m2/g.

Organic Robotics Based on Conducting Polymers

2012 ◽  
Vol 79 ◽  
pp. 87-93
Author(s):  
Hidenori Okuzaki
Keyword(s):  
Water Vapor ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Colloidal Particles ◽  
Water Vapor Pressure ◽  
Isosteric Heat ◽  
Water Vapor Sorption ◽  
Vapor Sorption ◽  
Free Standing

Free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by casting water dispersion of its colloidal particles. Specific surface area, water vapor sorption, and electro-active polymer actuating behavior of the resulting films were investigated by means of sorption isotherm, and electromechanical analysis. It was found that the non-porous PEDOT/PSS film, having a specific surface area of 0.13 m2/g, sorbed water vapor of 1080 cm3(STP)/g, corresponding to 87 wt%, at relative water vapor pressure of 0.95. A temperature rise from 25 to 40 °C lowered sorption degree, indicative of an exothermic process, where isosteric heat of sorption decreased with increasing water vapor sorption and the value reached 43.9 kJ/mol, being consistent with the heat of water condensation (44 kJ/mol). Upon application of 10 V, the film underwent contraction of 2.4% in air at 50% relative humidity (RH) which significantly increased to 4.5% at 90% RH. The principle lay in desorption of water vapor sorbed in the film due to Joule heating, where electric field was capable of controlling the equilibrium of water vapor sorption.

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