-
Details
-
Hits: 7175
Using the method of self-propagating high-temperature synthesis (SHS), porous metal-ceramic membranes based on a mixture of powders of aluminum oxide, silicon carbide, and magnesium oxide have been obtained. The membranes obtained are catalytically active, the surfaces of open pores in them are modified with rhenium-tungsten active components using the alkoxo method. At a temperature of 600 & # 176; C, the highest selectivity to propylene (& # 8776; 60 & # 37;) is achieved. In this case, the optimal conditions for the implementation of the propane dehydrogenation process is a temperature of 650 ° C, at which a fairly high selectivity for the most important monomers is maintained with a relatively small proportion of side processes
-
Details
-
Hits: 7190
The processes of melting of various types of igneous rocks that make up gabbro-basalt raw materials are considered. The role of the main rock-forming elements in the formation of these melts for the production of mineral fibers and petrurgy products is shown. Particular attention is paid to their influence on the viscosity and crystallization ability of industrial melts, as well as iron - the only element present in two oxidation states Fe (II) and Fe (III), which can participate, respectively, in the isomorphism of Mg and Al. Information on the influence of the ratio of these oxides on the crystallization of mineral fibers of stone casting products is given.
-
Details
-
Hits: 7390
The preparation of a composite filling material consisting of an inorganic filler in the form of finely ground glass and a polymer matrix is ??considered. The results of experimental studies on the comparative assessment of the value of water absorption and water solubility of various composite dental materials of chemical curing are presented.
-
Details
-
Hits: 7865
A sol-gel process for producing aluminum-magnesium spinel fibers from a fiber-forming precursor based on aluminum and magnesium polycarboxylates is considered. The principal possibility of obtaining discrete fibers of stoichiometric spinel by the method of aerodynamic spraying is shown. The results of studies of surface morphology, fine structure and phase composition of fibers are presented. It is shown that the structure of the fibers obtained is uniform, polycrystalline, and there are practically no non-fibrous inclusions in the pulp. The phase composition corresponds to the spinel stoichiometry
-
Details
-
Hits: 8062
One of the reasons for the relatively low quality of dense ceramic materials (porcelain stoneware, facade tiles and floor tiles) due to the appearance of a black core is the presence of unburned coal particles in them, which remain in the products after firing due to poorly selected compositions and heat treatment regime. Studies have shown that the largest mass content of C (carbon) in relation to other layers of porcelain stoneware is in the black porous core (9.68 & # 37;). The appearance of a black core is explained by the fact that during heating, organic impurities are carbonized mainly in the inner layers of porcelain stoneware, isolated from the access of air oxygen. In addition, the formation of a black core will also be facilitated by a sintering process with the participation of a liquid phase, which will isolate the carbonaceous material from the air before it is completely oxidized.
-
Details
-
Hits: 8253
The activity of foamed ceramics and foam glass to silicate-alkaline interaction in concrete has been investigated. It was found that in a humid concrete environment, vitrified walls of the pores of the aggregates are chemically active. Transformations of foam ceramics include gelation of the pore walls with the formation of an alkaline aluminosilicate gel followed by its crystallization. This ensures the fixation of the active components of such a filler in crystalline phases that are inert in a humid environment. The final stage of foam glass transformation is a non-crystallizing alkaline hydrated silicate gel
-
Details
-
Hits: 8793
The use of alkaline glass in the construction of micromechanical sensors, in particular, accelerometers, is presented. Alkaline glass is used in the design of the sensitive elements of these devices. The main process step for assembling such sensing elements is the electrostatic connection, also known as the anode connection. At the same time, a number of complex physical effects occur in the glass. The reliability of the functioning of the manufactured devices depends on the quality of performance of parts made of alkaline glass and silicon.
-
Details
-
Hits: 8771
A comparison is made of the main characteristics of aluminum oxides and hydroxides obtained by mechanochemical oxidation of aluminum powder, both in the initial state and after their heat treatment in the range 150 - 1100 ° C. The conditions for obtaining pseudoboehmite by thermal activation of a mechanochemically oxidized product have been established. The structure, morphology and texture of the pseudoboehmite structure of aluminum hydroxide synthesized from a mechanically oxidized product and aluminum oxides obtained on its basis in the temperature range 450 - 1100 ° C are characterized.
-
Details
-
Hits: 8734
The increased carbon content (9.59 & # 37;) in the inclusions indicates the introduction of fuel into the raw material, which increases the porosity of the products and contributes to the uniform sintering of ceramics, and the increased content of alkali oxides (R
2 O> 4 & # 37;) - the formation of a glass phase up to 1000 & # 176; С. X-ray phase analyzes showed the presence of: anorthite, hematite and wollastonite, which contribute to an increase in strength indicators. In addition, the presence of isometric pores and oval closed porosity in ceramic specimens contributes to an increase in durability.
-
Details
-
Hits: 9465
An alumina-graphite composite was obtained by the method of spark-plasma sintering. The influence of the size of graphite particles, the compaction temperature and the holding time on the formation of aluminum carbide is revealed. It is shown that the use of larger graphite plates reduces the formation of Al
4 C
3 by almost 2 times. The influence of the graphite content on the density, thermal expansion coefficient and thermal conductivity of the composite is considered. It was found that with a mass content of graphite above 70 & # 37; thermophysical properties of compacts significantly deteriorate due to the formation of a large number of pores
