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

On the basis of separate fractions of granular foam glass and inorganic binders, various modifications of heat-insulating composite material have been developed. A promising opportunity for potential application of the material is the preparation of composite elements and profiles suitable for installation around doors and windows during the construction or reconstruction of buildings. In connection with the study of the possibilities for optimal distribution of the granules, various options for their arrangement have been analyzed and evaluated. The mathematical tools of stereometry and 3D computer modeling were used. Visualizations of the obtained structures are presented and their compactness is evaluated. Recommendations are made for the ratio between the sizes and quantities of the granules used in order to achieve maximum density.

The development refers to an innovative technology and technological scheme of a workshop for the production of beehives made of amorphous quartz ceramics. The conditions for obtaining stable suspensions from quartz glass are emphasized and investigated. The time for the treatment of the glass in the grinding device, the amount of water, the influence of the modifiers in stabilizing the suspension by adjusting the pH level, as well as the most suitable sedimentary composition of the glass particles are established. The factors determining the speed and degree of sintering of the ceramics are investigated and established. They include the density of the raw products, the dispersion of the quartz glass particles and its purity, as well as the environment in the furnace and the sintering mode.

In view of the practical applications of the piezoelectric ceramics produced from barium titanate (BaTiO3) and barium stannate (BaSnO3), (the BT-BS system), the dielectric behavior of such materials was studied. The starting components (powder of both BaTiO3 and BaSnO3) were synthesizedand structurally characterized in аdvance. Bulk samples of BT-BS (formed as tablets with addition of PVA plasticizer) were prepared using the sol-gel method by varying the BT-BS composition percentage. The samples were characterized by complex electrical impedance spectroscopy and dielectric spectroscopy in the frequency range from 0.1 Hz to 1 MHz. As compared to BaTiO3, an increase with at least 50 % was measured for the value of the room-temperature dielectric constant (e′ – the real part of the dielectric permittivity) of the BT-BS samples containing 15 wt% BaSnO3. In contrast, the 50 wt% content of BaSnO3 led to a decrease of ′ value of BT-BS by a factor of 3.5, due to relatively low e′ value of BaSnO3. Analyses of the frequency spectra of complex electrical impedance and complex dielectric permittivity revealed the dielectric relaxational behavior of the BaTiO3+BaSnO3 system. The results obtained for ′ of BT-BS dielectrics as a function of the temperature were correlated with the data from structural studies. In particular, a specific enhancement of e′ was observed in temperature range around 120C for the BT-BS samples containing 15 wt% BaSnO3. Corresponding conclusions were done. The effects observed show that the synthesized BaTiO3-BaSnO3 ceramics are promising materials for piezoelectric and dielectric applications, e.g., in energy storage devices.

The aim of this paper is to review the cleaning of solar photovoltaic (PV) systems and applied coatings that eliminates costly automated cleaning systems by using nano-sized TiO2 combined with various organic binders.

The results of the plastic forming of ceramic pavers with a large volume and size are observed to produce better compaction of the raw material. The used ceramic mixture is based on a sedimentary rock with relatively high moisture content and firing shrinkage which gives the common yellow colour after a high-temperature liquid phase synthesis. The results of one-fold pressing revealed the occurrence of deformation processes in the drying stage and during the temperature regime. As a consequence, the pressing pressure should be increased and the residual water amount needs to be reduced to an optimal content.

Bees are highly sensitive to noise pollution and in some cases, noise can impact their behaviour. Towards the goal to create optimal living conditions for the bees, we aim to understand how the material of the beehive impacts the microclimate of the beehive. The present paper aims to examine and compare the noise levels inside beehives of the same construction but made out of different materials. Three 10-frame Dadan-Blatt beehives were used in the experiment – a ceramic beehive made out of high-cavity ceramic tiles of marl clay; a ceramic beehive made out of high-cavity ceramic tiles with increased kaolin content and a wooden beehive (pine). The noise was measured in an urbanized area and inside the beehives. The results show that the best performance in terms of noise insulation is the ceramic beehive with increased kaolin content.

The phase and petrographic analysis of a part of previously prepared test samples of coloured petrographic materials coloured with different contents of CuO, SnO2, CoO, Cr2O3 were studied. The raw materials are based on metamorphic rocks – dolomite marbles from the village of Ustrem and the village of Mramor, processed by melting at 1450°C, so that after crystallization, petrographic phases are obtained, which are confirmed by X-ray phase and petrographic analysis. The main characteristics of the colouring aggregates and their effect on the mineral composition and crystal structure are described.

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.

The research is related to the creation of new compounding formulations for the production of “yellow” paving stones. This was necessary due to denied access to a potential source of suitable raw material from the deposit near the village of Svetlen, Popovo municipality. Marlstone raw material from this deposit has the necessary qualities for such production, as a result of which, after hightemperature liquid-phase synthesis, new petrurgic phases with high physicochemical and mechanical properties can be formed. The new compounding formulation of the molding mass was developed on the basis of marlstone sedimentary rock from the Alexandra deposit, located near the village of Lovets, Targovishte district. The use of this compounding formulation makes it possible to obtain appropriate physicochemical and mechanical properties and a yellow coloring equivalent to that of the reference samples.

The use of clay as a structural material has been known for centuries. The authors set the task of studying the applicability of clay as a constructive material in the production of beehives. The study aims to make a comparative analysis of temperature conditions in different types and identical in construction beehives by comparing the indicator for ceramic and wooden hives. For the purpose were used three 10-frame hives type “Dadan-Blat” – two ceramic (one made entirely of marl clay, and the other – with increased kaolin content, both ceramic tiles are with high cavity) and one wooden (pine). Measurements of the air temperature and the temperature inside the hives were made for one month. From the obtained results it is established that for the studied beehives, the ceramic hive with high kaolin content has the best thermal insulation properties.

There has been growing interest in the use of the sol-gel approach to form high-quality dielectric materials. Their tailored properties allow for developing functional electronic devices in a scalable and rapid manner. According to physicochemical principles, the displacement and response behavior of charges under an applied external field can manifest in unique dielectric properties, providing useful information to improve the process, design, and quality of electronic devices. Therefore, a systematic and in-depth investigation of the fundamentals of sol-gel dielectrics is necessary. In this Research Update, we present recent advances in various sol-gel-processed dielectric materials and their applications to functional electronic devices. A brief introduction to sol-gel chemistry to form oxide dielectric films and the basis of physical mechanisms under electrical fields are discussed. Along with the dielectric properties, recent achievements of proofof-concept experiments and their various applications to functional electronic devices are introduced. It is expected that further innovations in solution-processed metal oxide dielectrics will achieve cost-effective high-performance functional electronics in the near future.

Lightweight porous ceramic has a number of advantages over the tightly sintered one depending on the field of application. As a building material with low thermal conductivity and good sound insulation properties, foam ceramic is a suitable material for the production of thermal and sound insulation panels, partition walls, as well as for layers laid under asphalt to protect road and urban square pavements from freezing. As a filling, foamed ceramic materials are also added during the production of lightweight concrete used in construction and architecture and in the manufacture of decorative and non-structural insulation elements. In the present study we consider the characteristics of marl clay, found around the village of Lovets near the town of Shumen, with coal as a foaming additive, and the technological regulation for the manufacture of foam ceramic blocks.