Segregation of impurities in platinum and platinum-based alloys

This work presents the research results of formation the equilibrium and non-equilibrium segregations of impurities both in pure platinum and platinum alloys. It is shown that segregations strengthen in the case when impurities, absorbed on the surface of crystals, have the same sign or similar values of range deviations regarding to the pure platinum. Equilibrium of segregations occurs as the diffusion result of impurities to the grain boundaries with creation of concentration gradient. Non-equilibrium segregation of impurities occupies the area size of ten micrometers and is generated in the process of metal crystallization or in solid solution as the result of interaction the impurities with vacancies with formation a pair of vacancy-interstitial atom. Segregation of impurities in the platinum alloys is conditioned by the nature of impurities, their concentration, distribution in the volume of metal, interaction with the basic and alloying components as well as the temperature - time factor. The groups of impurities were observed in the form of foreign inclusions along with the equilibrium and non-equilibrium segregation of impurities in the platinum alloys

Analysis of the verification criteria of testing methods by tension of steel wires

One of the criteria in the laboratory practice for laboratory accreditation according to the requirements of the SRPS ISO/IEC 17025:2017 standard is the verification of methods. Verification - standard methods of testing the steel wires, has shown the verification and confirmation of methods in the specific laboratory test conditions, specified in the requirements of the SRPS ISO/IEC 17025:2017 standard. The requirements of the test method standards by verification have proved to the service user to have a confidence in the result obtained by its application. In the paper, the authors present the verification of the test method by tension of metal wires (ropes) at room temperature, Method B, according to the requirements of the SRPS EN ISO 6892-1:2020 standard

X-control charts as a means of static quality control of rope testing for export facilities in mining

Accredited Laboratory for Materials Testing within the Mining and Metallurgy Institute (MMI) Bor has a primary role in testing steel ropes for export facilities in mining. Reliable and valid test results require the possession of correct and high-quality equipment, as well as the competence of the operators for this type of test. Testing of the correctness and reliability of the equipment is carried out using our own reference material of known characteristics, confirmed in other laboratories. The paper presents the results of testing samples of own reference material on a simple twisting test device. The results obtained using the X-control chart showed that the method of twisting the samples is under control, i.e., the acceptability of the results obtained using the tested method was confirmed, which means that the correctness of the device is at the required level

The effect of impurities on high-temperature resistance of platinum and its alloys

This paper presents the testing results of impact both the individual and total content of impurities in platinum and its alloys of different purity. Relative probability is presented of distribution of Al, Si, Fe, Mg, Ni, Pb, Cu, Ag, as well as their maximum content in the alloys of PtRh7, PtRh10, PtRh5Pd15 and PtRh5Pd15Ru1.5 composition. Also, the results of impact the purity degree of platinum to its high temperature resistance are given after applied thermo-mechanical processing regime. The conclusion is that, if content of impurities is higher in platinum metals and alloys, greater is the probability of their negative impact on technological and exploitation properties

Estimation the measurement uncertainty of physico-chemical properties of coals according to ISO 17025

One of the important elements for addressing the requirements of international Standard ISO/IEC 17025:2006, specifically set forth in paragraph 5.4.6.2, is to assess the uncertainty of testing and/or calibration. For determination the coal technical analysis uncertainty (moisture, ash, volatiles and combustible substances, c-fix, total sulfur, gross calorific value and net calorific value), the certified reference materials (CRM) benzoic acid (Ref.: 33 045 and Ref.: C723, Id. No.: 32 430 00) and coal tags GBW 11107k were used. Potential laboratory reference material (RM) was also used for comparison the measurement results and uncertainty in order that, after sufficient number of measurements and statistical analysis, could be used as a laboratory RM. The results showed that both CRM and selected potential laboratory RM could be successfully applied to determine the uncertainty of technical coal analysis, what is significantly cheaper for laboratory work, and in accordance with Standard ISO 17025

Effects of recrystallization annealing on mechanical properties of cold-rolled PdNi5 wires

The aim of this investigation was to determine the influence of the recrystallization temperature and recrystallization time on the microstructure and mechanical properties of the PdNi5 alloy subjected to cold deformation in the process of rolling at a constant deformation degree. The samples of PdNi5 alloy were recrystallization annealed within the temperature range of 200-1000 ºC and annealing time range of 20-45 min after cold rolling with deformation degree of 97%. The tensile test was carried out using universal material testing machine. The hardness was also measured on the combined device for measuring Vickers and Brinell hardness. Metallographic observations were performed on an optical microscope. The analysis of the results of investigations regarding the microstructural changes and corresponding mechanical properties of cold-rolled PdNi5 strips shows that annealing temperature of 500 ºC was sufficient to activate the energy for various recrystallization processes causing a change in the mechanical properties of cold-rolled PdNi5 strips. The annealing time, at constant annealing temperature, almost did not affect a recrystallization temperature and the mechanical properties of the cold-rolled PdNi5 strips

CHANGES IN Pt-Rh CATALYSTS IN THE WORKING ENVIRONMENT

Abstract The surface reconstruction on rhodium-platinum catalyst gauzes has been examined using the scanning electron microscope techniques

Changes in Pt-Rh catalysts in the working environment

The surface reconstruction on rhodium-platinum catalyst gauzes has been examined using the scanning electron microscope techniques. The nucleation and growth of large cage-like features, developed on the gauze surfaces during operation in the ammonia oxidation process, were studied in detail. It is concluded that a vapor phase mechanism involving transport of platinum oxide is responsible for the observed reaction, and the reason why this process operates only over a limited range of temperature and pressure is explained. Some comments are also made on the related reconstruction observed on gauzes, used during the production of hydrogen cyanide by the Andrussow process

Inter-verification of equipment using the x-control card in the Laboratory for Material Testing in the Mining and Metallurgy institute Bor

In the modern business of accredited testing laboratories according to the requirements of the SRPS ISO/IEC 17025 standard - General requirements for the competence of testing laboratories and calibration laboratories, the most important thing is the correctness of the testing equipment. The work procedure of the Laboratory for Material Testing in the Mining and Metallurgy Institute Bor requires checking the correctness of equipment twice a year in order to obtain the reliable and valid test results. This paper presents the procedure of intermediate verification the correctness of a device for testing the metal materials by tensioning, using a X-control card. The Xcontrol card is an auxiliary tool for collecting, processing, analyzing and displaying data in order to ensure the quality of products and processes. It belongs to the Statistical process control - SPC. The control chart that is created as a result of the statistical processing of the obtained data of tensile strength of wire on a tensile testing device shows the measure of quality the device correctness in the laboratory. The main goal of the X-control card is a very fast detection of errors during the work process of the Laboratory for Material Testing in the Mining and Metallurgy Institute Bor, i.e., checking the correctness of device

The influence of novel organic gold complex on photoresist layers of printed circuit boards

The goal of this paper was to study the influence of organic gold complex based on mercaptotriazole on photoresist layers used in manufacturing of printed circuit boards (PCBs). Investigations were performed by immersion the previously prepared boards in electrolytes with different pH values (pH=2, 4, 7, 9 and 12) at gold concentration of 2.5 g/dm3 and in gold complexes with different gold concentrations (1.5; 2.0; 2.5; 3.0 and 3.5 g/dm3) at pH value of pH=9. Investigations showed that photoresist layers on boards are the most resistant at optimal operating conditions, pH=9 and concentration of gold of 2.5 g/dm3