Papers by Keyword: Impurities

Abstract: The cathode sediments (CS), obtained as a result of industrial processing of gold-polymetallic raw material with complex chemical and mineral composition, contain a significant amount of impurity metals (copper, lead, zinc, iron, etc.), which leads to a significant increase in the cost of subsequent refining of these materials. The authors carried out experimental work on preliminary acid treatment of CS for the purpose of leaching impurities and increasing the share of precious metals in them. The objects of research were cathodic sediments (bypass solutions of the enterprise) containing copper and lead in the amount,% wt., respectively: 21.29 and 4.11. We tested nitric acid as a solvent in laboratory tests. For the selection of optimal leaching parameters, studies were carried out at various concentrations of the agent (from 50 to 350 kg/m3) and the ratio of L:S - (3-7):1. The duration of the experiments was 2 h, the experiments were carried out with vigorous stirring and standard ambient temperature (25°C). The experimental data processing was carried out with the help of STATISTICA 6.0 software; As factors of variation, we chose: concentration of acid, ratio of liquid and solid phases. It has been determined that nitric acid provides effective purification of CS from impurities. After the chemical enrichment, the content of precious metals in leaching cakes increased, the CS became compliant with the requirements of TU 117-2-3-78. When processing cathode sediments with nitric acid, 99% of silver passes into solution, which then allows it to be recovered from solutions by cementation and, consequently, to obtain alloys of gold and silver separately.

Abstract: One strategy to make PM titanium components competitive in terms of mechanical properties is the addition of suitable alloying elements. PM offers the possibility to adapt the alloy composition in order to achieve the required properties. In this study, different alloying elements were introduced into α/β titanium alloys and fatigue behaviour was evaluated. Four-point bending fatigue tests with a stress ratio of 0.2 were performed on specimens manufactured by metal injection moulding (MIM) and shot peening. Results showed an enhanced sintering activity of Ti-6Al-7Nb by adding small amounts of iron. The impact on fatigue properties was evaluated. The increase of oxygen in Ti-6Al-7Nb from 0.15 wt.% to 0.45 wt.% caused a decrease in elongation from 16% to 6%. However the fatigue strength at 10⁷ cycles is just slightly reduced from 450 to 350 MPa. The addition of 0.5 wt.% yttrium powder to gas atomized Ti‑6Al‑4V powder led to a noticeable refinement of the microstructure of the sintered parts, due to the formation of Y₂O₃ particles, which hinder grain growth. In spite of a slightly higher residual porosity, the microstructural refinement increased the fatigue strength at 10⁷ cycles from 450 to 470 MPa. At 10⁶ cycles, the fatigue strength increased even from 705 to 765 MPa. The addition of yttrium did not result in a higher oxygen pick up, which indicates a scavenging of oxygen from the titanium matrix by formation of Y₂O₃ during sintering. Contrary to the fatigue strength results, the scavenging effect led to a decrease in tensile strength of about 70 MPa. The microstructure of fatigue-tested specimens was characterized by using optical and scanning electron microscopy.

Abstract: The impact of impurities on the microstructure and thermal shock resistance of YSZ TBCs was investigated. ZrO₂-7.5wt%Y₂O₃ (7.5YSZ) coatings of 5 spices of compositions (4 of them were doped with one type of impurity, namely, Al₂O₃, Fe₂O₃, SiO₂ and TiO₂, and the other was not doped) were manufactured by APS. Thermal shock tests of these TBCs were carried out at 1100 °C, and the samples were quenched in cold water in the temperature range from 20 to 25°C. The microstructure evolution and phase analysis were performed before and after the thermal shock tests by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results showed that the thermal shock lifetime of YSZ TBCs doped with impurities was obviously reduced compared to that of no-impurity TBCs. Additionally, the differences in the microstructure and phases of YSZ TBCs were ascertained and the elements distribution was tested by Energy Dispersive Spectrometer (EDS) and Energy Dispersive X-Ray Spectroscopy (EDX).

Abstract: We describe the operation of a simple near-field interference microwave microscope. The microscope contains two identical probes which are connected to the ends of segments of the coaxial transmission line. The probes are constructed from an open-ended conical coaxial line and are excited by applied microwave voltage in the frequency range of 0.6 – 7.0 GHz. The computer simulation of the field distribution near the aperture of a separate probe was performed. The test objects are placed in the gap between the probes apertures. The main attention was concentrated on motor fuels to detect other impurities. In particular, diesel fuel was studied with impurities in the form of kerosene and synthetic motor oil in different proportions. It is shown that the microscope can reliably detect these impurities even if their content is relatively small. It was also demonstrated that the microscope can be used for determination of the alcohol quality and spirit-based solutions.

Abstract: Ruthenium is widely used as catalyst, magnetic recording and electrode materials. In this study, high-purity (≥99.995 wt%) ruthenium sponge was synthesized from crude ruthenium (≤99.9 wt%) by chemical refining technique. Initially, crude Ru was transformed into H₂RuCl₆ by distilling treatment. The H₂RuCl₆ was, then, added with NH4Cl powder to precipitate (NH₄)₂RuCl₆ powder. Afterward, the (NH₄)₂RuCl₆ powder was ignited in air and transformed into RuO₂. Finally, RuO₂ was changed to Ru by hydrogen reduction method. Impurities included in the starting Ru powder were eliminated after distillation and precipitation treatments. As-obtained ruthenium particles were spherical-like agglomeration, the average size was about 6 μm and the powder density was 11.83 g/cm³. The details of chemical transforming mechanisms in the refining process were described.

Abstract: As it is well known the grain mixture entered for processing, is a mechanical mixture of different components, which can be up to 20% of different impurities. Modern cleaning machines of various modifications do not always provide high quality separation of grain mixture. Imperfection of these machines does not allow get the maximum effect of purification. In order to improve the quality and achieve a more stable and independent processes grain cleaning, it is proposed a new device for cleaning grain. The device comprises a chamber with air aspiration inclined perforated shelves and a boot device. In the study of moving grain particles doped with an inclined perforated shelf is advisable to use the general law of dynamics for the bodies of variable mass. Movement of the selected grains center of mass mixed with particles in the direction of the shelves as described in the fundamental equation of dynamics. While moving mass of particles with a mixture of grains, will be reduced by removing light impurities retracting force of the air flow. This mass is a function of time. Taking into account the reduction of total mass of grain particles, because of impurities reduction the motion equation used in the form of variable mass. There will be the same equations of motion along the other shelves, respectively, the equations are written for the first leg, but with different masses, as well as with other forces retraction.

Abstract: We show experimentally that dislocations in Si crystals can generate some unknown vacancy complexes Vx_trail in their slip planes during their motion at 600°C. Most of these “dislocation trail defects” are not electrically active but can be detected by their reaction with gold atoms during in-diffusion experiments. It was also shown that contrary to gold, the Vx_trail-complexes do not react with interstitial Ni atoms. It means that the binding energy E_bind of Vx_trail complexes is quite high (E_bind>2.5eV), higher than the binding energy of vacancy complexes generated during FZ-Si crystal growth. It was also shown that Ni in-diffusion results in a strong increase of electron-hole recombination at dislocations and in a strong increase of dislocation-related DLTS C-line.

Abstract: Introduction of Mn²⁺ ions into ZnO in the form of Zn_(1-x)Mn_xO (0.00≤x≤0.25) has been done by means of coprecipitation method at low temperature using Zn(CH₃COO)₂·2H₂O, Mn(CH₃COO)₂·4H₂O, HCl, and NH₄OH as starting materials. The XRD analysis showed that the produced Zn_(1-x)Mn_xO (0.00≤x≤0.09) samples were crystallized in single phase of wurtzite with hexagonal structures. Besides the wurtzite, the presence of the secondary phase of hetaerolite ZnMn₂O₄ with tetragonal structures was detected in the samples having 0.10≤x≤0.25. The nanometer-sized Zn_(1-x)Mn_xO crystals obtained from XRD analysis were well confirmed by SEM and TEM images. The electron diffraction data showed that the secondary phase formed even for 0.01 and 0.10 Mn-doping samples were ZnMn₂O₄ and MnO₂. The VSM data indicate that the paramagnetic properties of Mn doping occurred at 0.00≤x≤0.06 and 0.10≤x≤0.25 as well as superparamagnetic properties occur in Mn doping 0.07≤x≤0.09. The most interesting fact in this study was the formation of secondary phases in all Mn-doped ZnO samples, even for the smallest x of 0.01.

Abstract: Lap joints are most used joints in automotive industry. These types of welds are usually created by spot welding, but new technologies who came to automotive industry considerably do weld process faster. Paper deals with laser welding parameters and their influence of weld seams. The parameters of welding are readjusting according to shape of weld, impurities of surface and gap. Steel S500MC with thickness of 1.0 and 2.2 mm was used as the base material. For welding was used fiber laser Ytterbium Laser System YLS with power of 6000 watt from IPG Company. Research was oriented on changing weld parameters and their influence of welds quality. It was found that butt welding joints are sensitive to gap and the gap tolerances which in turn is dependent on material thickness, beam diameter, welding speed and beam quality.

Abstract: Due to the particularity of its percolation of low permeability reservoirs, water injection is very difficult and damage to the reservoir, especially the impurities in injection Wells, at the same time affect the injection efficiency, it will ultimately affect the recovery of the reservoir and the oilfield production. So it is necessary to carry out the ingredients and the causes of impurities in injection wells, clearing the Source for different kinds of impurity to provide the basis for reduce the impurity content in injection wells. In this paper, the author analyzed impurities particle size, composition and content in oilfield injection water In Longhop Oilfield through the indoor experiment, and with the comparison between the ion content and composition of the filtered water samples, analyzing the cause of the impurity within the wellbore. Experimental results show that in oil field water injection well, impurities particle size are mainly distributed between 2.6 and 5.4 um, impurity content mainly changes between 0.003746% and 0.017189%, the main ingredients of impurities is Fe₂O₃ and acid insoluble substances (SiO₂). Fe₂O₃ mainly comes from the injection water; acid insoluble substances mainly come from the formation sand production.