International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The aim of the present work is to study the characteristics and conditions of obtaining thin films in the BaTiO3–BaSnO3 system, deposited by the sol-gel method on monolithic multilayer samples. In laboratory conditions, the structure, phase composition, micromorphology, electrophysical parameters of the prepared experimental samples were studied. The existing possibilities for optimizing the applied technological regime for the synthesis and surface deposition of thin-layer coatings with set characteristics have been analyzed.

An innovative collapsible frame hive was developed, consisting of structural elements made of technical ceramics containing thermal insulation air chambers. Experimental prototypes were prepared using the slip casting method and based on modified recipe compositions, prepared casting molding masses, original gypsum matrices and optimal heat treatment mode. A comparison was performed between the main operational characteristics of the experimental samples and the traditional non-separable hives which have existed throughout history and made primarily of various plant materials and natural plastic raw materials (clays).

A financial project was presented for the construction of a technological line for the production of high-quality replicas of the socalled “yellow paving stones” and an additional assortment of products with different characteristics based on raw materials originating in Bulgaria. After many years of investigation in laboratory and semi-industrial conditions, polycomponent formulations and an original hightemperature technological regime for the preparation of functional and long-lasting silicate products have been developed. The planned technological approach is in accordance with the existing machine park and the qualification of the industrial production personnel, characteristic of the silicate industry. The main possibilities for the realization of the production are the full restoration of the street areas of the central historical part of Sofia and the construction of long-lasting and aesthetic pavements with a variety of functional purposes in different areas of the capital and other populated areas. The current applied development is oriented towards possible potential producers and investors and various specialists from the field of public infrastructure and cultural-historical heritage.

A financial project has been prepared for the construction of a plant equipped with a technological line for the production of foam glass products. It is planned to build a warehouse for raw materials, a sector for preparation of materials, various production workshops for the manufacturing of foamed granules and pieces, a continuous tape or block of foam glass, various composite materials (thermal insulation and color decorative panels, various small and large composite elements, etc.), repair section and two warehouses for finished products. Approximate calculations have been made for the necessary raw materials, technical equipment, electricity, personnel and other costs for the realization and operation of the plant.

Due to force majeure circumstances, new researches of marls from the Alexandra deposit to the village of Lovets (Shumen region) were carried out to replace the marls from the village Svetlen (Targovishte region), which are part of a plastic mass for the production of large, fine-ceramic parts (yellow paving stones) from peturgical phases. Marls are characterized in terms of mineral and chemical composition. Their properties, characterizing them as a ceramic raw material, have been determined. Three test masses with a chemical composition similar to the one with the participation of marls from the village of Svetlen were developed. The test specimens are characterized in terms of sintering and strength characteristics. It has been established that the marls can be used to repla ce the marl from the village Svetlen in the composition of the plastic fine-ceramic masses for the production of yellow pavers.

Barium titanate ceramics doped with samarium were synthesized by low temperature sol-gel method. The physicochemical characterization of the samples was carried out by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). A pure BaTiO3 cubic phase was obtained. A technological regulation has been developed for the preparation of test samples .Monitoring ofthe relative dielectric permittivity of Sm-doped BaTiO3 ceramics with temperature changes (at frequency of 10 kHz) was realized.The resulting curve is typical of ferromagnetic material. The synthesized barium titanate ceramics possesses a high dielectric constant – 17500 at a Curie temperature Tc (65oC). The obtained values for the relative dielectric permittivity and Curie temperature of Sm-doped barium titanate ceramics are much better in comparison to conventionally non-doped BaTiO3-εr = 2000 and Tc = 120°C.

In summary form, some trends in the production and application of foamed silicate materials obtained from recycled waste materials are presented. The existing possibilities for the use of different fractions of foam glass granules for the preparation of various products (lightweight concrete, colored decorative panels, etc.) are considered. Experimental samples are prepared in which the average value of the thermal conductivity coefficient =0.24±0.13 W/m. K was established. The main technological factors determining the operational characteristics of the material and the existing potential prospects for their optimization are analyzed.

A conceptual design of a technological line for the production on the one hand of a continuous flat strip and block and on the other hand granules and pieces of foam glass, including a ware house for raw materials, a workshop for preparation of materials, workshops for foamed granules and a continuous flat strip of foam glass, workshop for composite elements semi O, P and slabs, repair section and warehouse for finished products is presented The necessary equipment and materials, building the technological line and functioning of the plant as a whole, are presented.

The sol-gel process is a well-known and reliable process for obtaining materials and coatings of different structure and properties. An important feature of this method is the choice of starting precursors to obtain the desired compositions. The complexity of the technology is due to the difficult process control. For this purpose it is necessary to accurately calculate the stoichiometry to obtain the final phase. Thus, the sol-gel technology is widely used as in the production of coatings by immersion and spraying, aerogels and others. However, there are many other applications such as electronic materials that have not yet been well studied. In this study, after a brief explanation of the process, some of the most important applications are considered.

Experimental ceramic samples were obtained in which the presence of CaMgSi2O6 (predominant phase), MgCr2O4, CaAl2Si2O8 and quartz was detected by X-ray diffraction analysis. During the microscopic examination of the prepared sections, two mineral phases were established: main – clinopyroxene and secondary – green spinel. The presence of prismatic-granular and skeletal structure was found. In the formed dominant diopside phase the presence of numerous inclusions of magnesium-chromium spinel with green color (sizes up to 0,05 mm) was observed evenly distributed in the sections determining the characteristic green color of the samples.

In this paper we present the results of atomic force microscopy (AFM) characterization of the surface morphology of the nanostructured titanium oxide films featuring with Sm2O3 by the sol-gel method in order to increase the corrosion resistance of stainless steel. Two types of titanium precursors were applied – titanium (IV) isopropoxide Ti[OCH(CH3)2]4 and titanium(IV) butoxide Ti(OCH2CH2CH2CH3)4.

Different corrosion-resistant coatings based on various SiO2, TiO2, ZrO2 and CeO2oxides have been applied to various steels by the sol-gel method and spray pyrolysis. The obtained experimental coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and weight loss measurements in 3.5% NaCl medium. TiO2 / SiO2 and CeO2/SiO2 coatings treated at lower temperatures (500oC) have been shown to exhibit higher corrosion resistance than ZrO2/SiO2 samples. Increasing the treatment temperature decreases the protective properties of the invesitgated coatings. The enhanced protective properties of TiO2/SiO2 are probably due to their low crystallized fine grained structure and relatively dense surface without visible cracks.