• Peculiarities of the technological process in the preparation of metal powders

    pg(s) 93-95

    This publication traces the peculiarities of metal powder production for powder metallurgy. Of the variety of methods, particular attention is paid to those that are most widely used in practice – reduction and powdering methods. Metallurgical photo of iron powders obtained by different technological processes are presented, as well as tables with the basic technological properties of iron powders obtained by reduction and powdering.

  • Thermal conductivity of the ceramic beehives

    pg(s) 90-92

    Beehive made of ceramic is a relatively novel concept in the feed of the beekeeping industry. One of the reasons behind the idea of changing the classical construction material of the beehives is the relatively better thermal conductivity of the ceramic material in comparison with the wooden. Previous field observations show that in wintertime the temperature in the ceramic beehive is with 1oC to 2oC warmer than the temperature measured in a wooden beehive from the same field. The present study aims to examine the thermographic characteristics of a ceramic beehive and to compare them with the most spread wooden type of hives. For the purpose, it was conducted a thermographic diagnostic of three beehives (two ceramic and one wooden) from the same field. The measurement is conducted with a thermal imaging infrared camera. For the analysis is used a licensed software FLIR Reporter Pro. The results of the comparative analysis show that in terms of balanced thermal distribution and creating a better internal environment, the ceramic beehives outperform the wooden one. What is more, the higher porosity of the ceramic material is proved to be a factor in the provision of a balanced thermal environment for the bee family.

  • Synthesis and investigation of BiTeSe single crystal doped with As obtained using bridgman method

    pg(s) 87-89

    Researches in this paper included synthesis and characterization of bismuth telluride single crystal doped with arsenic, obtained using Bridgman method. Compounds based on bismuth telluride are very important materials for thermoelectric refrigerators and devices for electricity production. For the monocrystal characterization, SEM – EDS, Hall and Van der Pauw method were used. The results presented in paper show the synthesis of monocrystal ingot, BiTeSe doped with arsenic. An analysis of energy dispersive spectrometry (EDS) was used to determine the chemical composition of the samples studied, as well as checking and confirming the homogeneity of the samples. Measurements of X-ray diffraction (XRD) showed that the resulting crystalline ingot represent a single crystal and confirm the compound of Bi2Te3 type. Mobility, concentration, resistivity/conductivity, of majority of charge bearers and Hall coefficient of single crystal, were determined using a Hall Effect measurement system based on the Van der Pauw method. For the sample of BiTeSe doped with arsenic Hall effect was measured at room temperature with an applied magnetic field strength of 0.37 T at different current intensities. Further characterization of the BiTeSe sample doped with arsenic was not performed, because the expected improvement in the mobility of this sample in comparison with the theoretical value of the n type Bi2Te3, was not obtained.

  • Improving the Linearized stresses resistance by Nano-Coating, Part-2

    pg(s) 44-54

    The part-2 research is a continuation of part-1 of using a simulation of Nano coating effect on linearized stresses resistance using Finite Element Analysis (FEA) software was carried out. The prime focus here was on exposing a thin Aluminum (Al7075-T6) walled spherical vessel to internal pressure before and after coating, this spherical vessel was coated by Nano- layer using two different materials such as Titanium (Ti) and Nickel (Ni) with thicknesses ranging (100 nm, 500 nm, and 900 nm). Then a comparison of the obtained results was made before and after coating. The results showed that the aluminum Al7075-T6 thin walled spherical vessel successfully coated with Titanium and Nickel separately using ANSYS software. In addition, the results have shown that 100,500 and 900 nm thickness Nickel coated aluminum 7075-T6 thin walled spherical vessel has a better improvement in linearized stresses resistance. These improvements in linearized stresses resistance were equal to 42% with Nickel coating in comparison with Titanium coating of thickness (100, 500 1nd 900 nm). The improvement of the linearized stress highest resistance is about 2.5% and 5% for Ti and Ni, respectively.

  • Literature survey of fatigue analysis approaches of vehicle components made of rubber under the influence of temperature

    pg(s) 40-43

    Vehicle components made of rubber usually exhibit large deformations. Cyclic finite deformations generate temperature in hyperelastic materials. Furthermore it is necessary to take into consideration the effects of ambient temperature. The mechanical properties of rubber depend on temperature and temperature changes can accelerate chemical alteration processes which lead to the material deterioration and fatigue processes. Research on fatigue behavior and fatigue properties of rubber has a great significance for predicting fatigue life and improving durability of rubber products. First purpose of this paper is summarizing the influence of temperature and temperature changes on the fatigue behavior of rubber. The second purpose of this study is to provide an overview of the state of the art on the fatigue life prediction of rubber with primary focus on the different methods available for prediction of fatigue life under the influence of temperature and temperature changes.

  • Alkali and acid activated geopolymers based on iron-silicate fines – by-product from copper industry

    pg(s) 37-39

    Geopolymer based on iron-silicate fines (fayalite slag) were synthesized in alkaline and acidic media using activation solution
    comprised of respectively alkali silicate and phosphoric acid solutions. The raw material consists of fayalite, magnetite and pyroxene which could be a conglomerate in some particles. The alkali activation occurs very slow at room temperature, while acid activation take place very rapid. The acid activated geopolymer binder phase include cracks probably formed by thermal gradient because of the rapid exothermal reaction. The morphology of the alkali activated geopolymers were presented by porous structure.

  • Investigation of anticorrosive behavior of zirconia-titanium coatings in NaCl medium

    pg(s) 34-36

    Sol gel TiO2-ZrO2 composite films were dip coated on stainless steel substrates and treated at 300, 400 and 500oC. The morphology and surface features were examined by Scanning electron microscopy (SEM) and X ray photoelectron spectroscopy (XPS). Xray diffraction analyses (XRD) was applied to investigate the phase composition. The corrosion resistances of the coatings were studied by evaluation of the weight loss in NaCl medium. According to XRD while the Zr-Ti composites are amorphous after treatment even at 500oC. The surfaces of the coatings possess typical island structure. The coatings, treated at 500oC ehxibit higher corrosion resistance than the other two type of samples. This could be explained by the amorphous structure of the composites, which lowers ion and electron conduction, high hydrophobicity and lower oxygen content.

  • MODIFIED PETRURGICAL MATERIALS BASED ON SEDIMENTARY ROCKS USED FOR BALLISTIC PURPOSES

    pg(s) 566-568

    Bulgaria has a variety of deposits (mainly in northeastern Bulgaria) of sedimentary rocks (marls) suitable for the development of compounding formulations and technology for the production of stone products. On the basis of some of these sedimentary rocks (marls), experimental technologies for innovative formulations with modifiers for usable petrurgical materials are developed and tested. The first prototypes of ballistic protection products are obtained, with physic-mechanical properties better than those when only natural sedimentary rock is used, and lighter and cheaper than in the case of corundum and silicon carbide.
    The properties of these materials allow for certain alternative applications such as the ballistic protection of ground-based mobile and stationary objects. They also make possible the production of quality articles with protective properties against high-speed kinetic effects, but at significantly lower cost than when traditional materials are used.

  • CERAMIC SUPERCAPACITOR

    pg(s) 564-565

    This report examines the characteristics of powerful supercapacitors, which are used in electric vehicles to perform their driving dynamics, as well as to power starter motors of powerful internal combustion engines in large trucks, military vehicles and more. Main requirement for supercapacitors is tobe able to deliver a large amount of electricity for about ten seconds, and for very powerful motors (over 100 kW) – for up to 15 seconds. Various technological methods have been reported for supercapacitorsproduction, including the onedeveloped by the current authors, which is based on a ceramic dielectric with a high relative dielectric constant.

  • PROTECTION OF TITANIUM AGAINST HYDROGEN EMBRITTLEMENT

    pg(s) 561-563

    The protective coatings of Al2O3 and AlN on iodide titanium in initial state and after annealing in a hydrogen atmosphere were investigated by scanning electron microscopy. It was found that the coatings protect titanium from the interaction with hydrogen at a pressure of 0.6 MPa up to 650 °C. It was shown that at 700 °C and pressure 0.6 MPa cracking of the protective coatings occurred, and the process of active absorption of hydrogen started.

  • QUALITY MANAGEMENT OF NEW CERAMIC MATERIALS BY USING STATISTICAL EXPERIMENTAL DATA PROCESSING PROGRAMS

    pg(s) 515-518

    In this paper, we consider the theoretical foundations of the synthesis of ceramic materials from natural aluminosilicates with the addition of technogenic materials (lead and copper slag) using powder metallurgy methods. The characteristics of the feedstock, properties are presented, the geographical deposits of natural components are shown. The possibility of obtaining pelletized, granular, and block ceramic materials based on natural and technogenic sorbents of Kazakhstan is shown by powder metallurgy methods.

  • ON THE EFFECT OF INTERMEDIATE PRESSING OF PREFORMS ON THE FORMATION OF A DEFECT-FREE STRUCTURE OF FINISHED PRODUCTS FROM CARBON FIBER-FILLED POLYTETRAFLUOROETHYLENE

    pg(s) 511-514

    This article describes a method for producing composite materials based on polytetrafluoroethylene with high performance properties. One of the obstacles to achieve this result had been the accumulation of moisture in the semi-finished product, which subsequently led to the appearance of defects in products made of fluorine composites. It is proposed to produce semi-finished preforms under reduced specific pressure, in which the moisture content is easier, cheaper and more efficient to control than with the current technological regulations. It is shown that the use of these semi-finished preforms allows getting almost defect-free products with high performance characteristics.