Inorganic Materials: Applied Research最新文献

Abstract

The results of experimental studies on attenuating neutron and photon radiation in a nuclear reactor using a protective metal hydride composite are presented. The distribution profile of the dose and spatial energy is obtained for primary and secondary gamma radiation. It is shown that the dose of gamma radiation behind the protection is associated with capturing gamma rays generated in the initial layer of the material. Based on the results obtained, the calculation model of the experiment is verified in the two-dimensional geometry for the properties of the material protecting the reactor. The verification involves the discrete ordinate method based on the DORT package. Deviations between the calculated and experimental values of the fast neutron relaxation lengths do not exceed 5%. The same deviations obtained for gamma radiation are under 7%, which confirms the validity of the calculation technique and the potential to apply the data obtained to proceed with designing radiation protection based on the metal hydride composite.

Abstract—Hard-magnetic Fe–30 Cr–20 Co alloys doped with 1 wt % of aluminum have been obtained. The two different aluminum sources used were elemental aluminum powder and an iron‒chromium‒aluminum alloying composition. Study of the density of the samples has shown that the aluminum additive increases the porosity of the material from 2–3 to 4.5–7%. The highest porosity was observed when using the alloying composition. Differences in the pore structure after sintering under the same conditions depending on the aluminum source have been found. When the alloying composition is used, pores acquire a branched structure, which indicates incomplete sintering. When elemental aluminum powder is used, the pores are distributed more uniformly and their shape becomes closer to spherical. According to the X-ray diffraction data, when the alloying composition is used, the material contains traces of the nonmagnetic γ and σ phases after a complete processing cycle. It is shown that aluminum doping of the Fe–30 Cr–20 Co alloy does not improve the magnetic properties and the use of the alloying composition degrades them, mainly the residual induction B_r. The investigated alloys have been found to be sensitive to the heat treatment conditions. The highest magnetic characteristics are B_r = 0.66 T, H_c = 43.2 kA/m, and (BH)_max = 10.2 kJ/m³ with the alloying composition used and B_r = 0.85 T, H_c = 46.7 kA/m, and (BH)_max = 15.1 kJ/m³ with the elemental powder used. During the compression tests, the investigated alloys have been deformed without fracture up to the maximum strain degree of ε = 17.5–20% and have exhibited high yield strengths: σ_0.2 = 1050–1250 MPa.

Abstract

Ingots of highly doped silicon Si:P grown by Bridgman directional crystallization with a small (up to 5 at %) fraction of germanium impurity are studied. The main thermoelectric parameters of the material are measured in the temperature range from 50 to 800°C: Seebeck coefficient, electrical conductivity, and thermal conductivity. On the basis of measurement results, the thermoelectric figure of merit determining the efficiency of thermoelectric conversion was calculated. A study of the electrical properties shows that phosphorus from the SiP compound is incorporated into the lattice as a dopant which provides a high concentration of conduction electrons. Chemical analysis of the ingots shows the presence of additional background impurities in them, the concentration and composition of the impurities vary throughout the bulk of the sample. Despite the presence of impurities, the material demonstrates high thermoelectric characteristics, and the efficiency is at the level of the best world results. Further potential for optimization of thermoelectric characteristics owing to the possibility of forming a fine-grained polycrystalline structure is considered.

Abstract

The morphology of structural components in hot rolled pipes made of 38G2F steel has been studied by optical metallography. It is shown that the sections elongated along the rolling direction with a morphology different from pearlite are sections of upper bainite, the hardness of which is comparable to the hardness of pearlite (~290–300 HV_μ). Plotting the thermokinetic diagrams (TKD) of the decomposition of supercooled austenite, as well as a joint analysis of the microstructure and hardness, allowed us to determine the minimum velocity V_cool ~ 0.5°C/s at which the bainite component in the pipe wall is formed. The temperature–time parameters of the decomposition of supercooled austenite with increasing austenitization temperature from 850 to 1000°C have been determined.

Abstract

The article examines the features of structural formations and their influence on the properties of chlorosulfonated polyethylene (CSPE) films during preparation from solutions in carbon tetrachloride under the influence of a constant electric field. It has been shown that films formed in a directed constant electric field have higher electrical resistance and lower values of electrical capacitance, heat capacity, and electrical loss tangent in relation to films formed outside the field.

Abstract

In this paper, an algorithm for macrofractographic study of materials is proposed on the basis of analysis and sampling of functions and means of measurement of a digital optical microscope. It consists of a consistent implementation of methods developed in this work for studying the fracture surface of materials in a 3D image using digital image processing and using automatic lens recognition and proximity functions. To evaluate the applicability of developed algorithms, dispersion-strengthened composites with an aluminum matrix with different particle sizes and volume fractions fractured under tension were studied. On the basis of results of research, features were established in the mechanisms of fracture and locations of foci and crack nucleation zones during tensile tests depending on the amount content of solid phase in the structure of dispersion-hardened composite materials obtained using internal oxidation technology.

Abstract

The article summarizes the results of experimental studies of the temperature dependence of the thermophysical properties and thermodynamic functions of lead babbitt BLa (PbSb15Sn10) with lanthanum additives. The heat capacity of lead babbitt was determined in the “cooling” mode according to the known heat capacity of a reference sample of C2C lead. For this purpose, by processing the cooling curves of lead babbitt samples and reference, equations were obtained that describe their cooling rates. Further, on the basis of the experimentally found cooling rates of the reference and alloy samples, knowing their masses, polynomials for the temperature dependence of the heat capacity of the alloys and the standard were established, which are described by a four-term equation. Using integrals of specific heat capacity, the temperature dependence of changes in enthalpy, entropy, and Gibbs energy is determined. The data obtained show that, with increasing temperature, the heat capacity, heat transfer coefficient, enthalpy, and entropy of babbitt BLa (PbSb15Sn10) increase, and the Gibbs energy decreases. At the same time, lanthanum additives from 0.01 to 1.0 wt % increase the heat capacity, enthalpy, and entropy of babbitt BLa (PbSb15Sn10), while the value of the Gibbs energy decreases.

Abstract

The results obtained using the developed mathematical model of a detailed change in the temperature field and the phase transitions during cooling and crystallization of a melt droplet under cooling in the water and water–steam environment are analyzed. The presented mathematical model not only allows one to establish temperature fields in the droplet or granule body but also determines the velocity of motion of a droplet in a coolant at each specific instant of time, the intensity of heat removal, the cooling rate, and the melt crystallization rate at different points in the volume. The aforementioned ultimately makes it possible to predict dendrite sizes and the properties and phase composition of a material of synthesized granules. The mathematical model has been tested in granulation of aluminum superalloys (D1 and D16 alloys of the Al–Cu–Mg system and V95 and V96Ts alloys of the Al–Zn–Mg–Cu system) obtained by centrifugal spraying of melt and the drop method upon cooling in a water environment. The rate of crystallization in natural samples has been measured by analyzing the dendritic parameter of the material structure. The mathematical model has demonstrated a high degree of convergence of the results of simulation modeling and the results of real experiments for production of granules. The model has yielded, in particular, fairly accurate results of the formation of granules at ultrahigh crystallization rates without a “steam jacket,” i.e., a vapor layer appearing between the granule body and the coolant, reducing the heat removal intensity and preventing the growth of the crystallization rate owing to the lower thermal conductivity of water vapor.

Abstract

The history of occurrence and technological features of obtaining transparent aluminum oxynitride ceramics are examined in detail. It is concluded that high-purity single-fraction powders should be used to obtain optically homogeneous aluminum oxynitride ceramics. The introduction of additives regulating the microstructure and properties of transparent ceramics is recommended. The application area of such ceramics is given.

Abstract

The doped crystals of the Ge_1–x–Si_x〈Ga〉 and Ge_1–x–Si_x〈Sb〉 solid solutions have been prepared by the hybrid method. The Hall measurements have been carried out on the samples at room temperature, from which the distributions of gallium and antimony impurities along the prepared crystals of Ge_1–x–Si_x〈Ga〉 and Ge_1–x–Si_x〈Sb〉, respectively, have been determined experimentally. At the same time, in the Pfann approximation, the one-dimensional problem on the axial distribution of the gallium and antimony impurities in crystals of the Ge–Si solid solutions grown by the hybrid method has been solved. The results obtained demonstrate good agreement between experimental and calculated data. This fact allows us to conclude, that mathematical modeling gives an opportunity to control, over a wide range, the concentration profile of impurities in the Ge–Si crystals grown by this method by changing the starting concentrations of impurities and creating the respective gradient of temperature in the melt in the section of crystal growth by the directional constitutional supercooling of the melt method and the ratio of the replenishment and crystallization rates of the melt in the section of the homogeneous crystal growth.