Materials Science Forum Vol. 970

Abstract: A comparative analysis of the efficiency of zirconia ceramics high-energy electron beam sintering by one-step mode and two-step mode sintering was performed for compacts prepared from commercial TZ-3Y-E grade and plasmo-chemical powders. The electron energy was 1.4 MeV. The samples were sintered in the temperature range of 1100–1300°C. The extent of influence of one-step and two-step sintering mode on the characteristics of sintered ceramics depends on the initial powders. Сorrectly chosen the temperature mode of two-step sintering (T_s1=1300°C t = 15 min, T_s2=1200°C t=1 h) leads to an increase of the density and microhardness values of ceramics relatively considered of results at one-step and two-step mode of sintering.

Abstract: The characterization of natural zeolite from Badinsk deposit was carried out by means of X-ray diffraction, scanning electronic microscopy, thermal analysis, Fourier transform infrared spectroscopy. The possibility of water purification from phosphates in dynamic conditions using of natural zeolite as a filtering bed was studied. The effect of the filtration rate of phosphates solution on purification efficiency is investigated. The mechanism of phosphates and ammonium removal with the participation of the zeolite is discussed: in case of phosphates it is the formation of insoluble compounds by reacting of calcium cations and phosphate anions; in case of ammonium ions it is ion exchange.

Abstract: This article shows a study of the effect of mechanical activation of the initial mixture of reagents NiO and Fe₂O₃ at different speeds of grinding bowl rotation on synthesis of nickel ferrite. Nickel ferrite was produced by the solid-phase synthesis at a temperature of 900 °C for 240 minutes. The obtained ferrite samples were investigated by thermal gravimetric and X-ray phase analysis. The Curie temperature values are obtained, as well as the magnitude of the change of detected instrument weight at the magnetic phase transition (ferromagnetic-paramagnetic) of nickel ferrite using thermal gravimetric curves (TG/DTG) with applied external magnetic field. Increasing of the homogeneity degree of ferrite materials with an increase in the mechanical activation rate is shown based on the data of X-ray phase analysis. The experimental results obtained from thermal, magnetic, and X-ray analyzes were compared.

Abstract: Welding is the basic process of metal working and metal structural repair in mechanical engineering and other industrial settings. However, welding is considered to be potentially hazardous work. Welding can be a source of injury causing eye damage, body burns, mechanical injuries and poisoning. The present paper identified the possible causes of burns by the Causal tree method. The probability of initial events, leading to burn, was estimated by the expert evaluation method. The severity of the injury consequences for welder's health was assessed. The severity of the consequences was defined as the financial loss of a company depending on the damage to worker's health during the welding work performance. The risk of burn of various severities was estimated and measures for its reduction were offered. The estimation of efficiency for the offered safety measures was carried out based on the cost for their implementation.

Abstract: Most dielectric materials and heterogeneous dielectric structures are operated under mechanical loads. Therefore, the usage of acoustic monitoring of the presence of defects and the destruction of such materials is difficult because of the high ultrasound damping decrement in these materials. This article presents assess the influence of the location of steel inclusions relative to the loading axis.

Abstract: The article considers the issues of receiving nanosized Ba_0,8Sr_0,2TiO₃ ferroelectric films and diamond-like films in the range of 10‒60 GHz with various thickness between 0.1‒10 μm and their dielectric properties. Peculiarities of SHF dissipation measuring method in dielectric films are discussed. It shows the influence of structural perfection of films on the value of losses of SHF energy.

Abstract: The paper assesses the possibility of using the reverberation phenomenon to control the imperfections and the stress-strain state of solid dielectric materials by the method of mechanoelectrical transformations. The main advantage of reverberation is the repeated intersections of the excitation zones of inhomogeneities by acoustic waves, that is displayed in response parameters. The reverberation makes it possible to accumulate distortions of wave fronts. A comparative analysis of the responses from the sample under condition of uniaxial compression under different loads was performed. Differential analysis for the deterministic time component of the response in the interval (0–0.3) ms, and a statistical analysis of the differences for the pseudo-random component in the interval (0.8–1.8) ms were performed. For the statistical analysis, the distribution of the pulse flow is selected. The response was calculated according to the mathematical model under the conditions of a change in the speed of sound, which simulates a change in the sample inhomogeneity under load. The calculation showed a qualitative similarity with changes in responses in a real experiment. According to the obtained results, it was concluded that it is possible to use the deterministic and pseudo-random components of the responses in the reverberation condition to control the change in defectiveness and the degree of heterogeneity under the action of the mechanical load on the sample.

Abstract: The kinetic and morphological peculiarities of polytetrafluoroethylene (PTFE) coating growth onset from the active gas phase on differently pretreated substrates are considered. The substrate surface energy was found to exert an effect on distribution of polymer micro-and nanoparticles both at the initial stage so during coating growth. The substrate surface activation was proved to result in the increasing growth rate and formation of a continuous coating with a thinner apparent thickness. The physicomathematical model of presented regularities was elaborated.

Abstract: Many industries apply pressure tanks for the storage of various types of liquids [1]. It can be toxic, chemically active liquids or food products. Storage conditions of these liquids can have a wide range of pressures and temperatures; therefore it is preferable to control the liquids levels from the outside of the tank. The most optimal solution in this case is the ultrasonic pulse time method [2-6], which is also widely used in robotics [7], fishing, shipping [8-9], archeology [10-11], non-destructive testing [12-17] and manometric method [18].