Johnson Matthey Technology Review - Fast Track

Abstract: The Ćuk converter is extensively utilized across various applications for its capability to handle a wide range of input voltages and efficiently perform both voltage step-up and step-down conversions. However, the presence of parasitic elements, such as inductor winding resistance, capacitor equivalent series resistance (ESR), and losses in switches and diodes, significantly impacts the converter's performance, stability, and efficiency. This paper addresses these challenges by analyzing the effects of non-idealities in Ćuk converters operated under closed-loop voltage mode control. A detailed mathematical model of a 12 V to 24 V Ćuk converter is developed to evaluate the influence of parasitic elements and their interactions within the control system. This model provides valuable insights into the complexities introduced by these non-idealities and serves as a foundation for designing more resilient control strategies. To ensure output voltage stability and improved dynamic performance, a PID controller is employed with parameters optimized using the Ziegler-Nichols tuning method. The proposed control strategy is validated through MATLAB simulations, showcasing its effectiveness in countering the adverse effects of parasitics. The results indicate a stable operation with a steady-state error of less than 1%, a peak overshoot of 6.31%, a rise time of 6.21 ms, and a settling time of 37.4 ms. This work contributes to enhancing closed-loop voltage mode control strategies for non-ideal Ćuk converters, offering practical solutions to improve their reliability and efficiency in real-world applications.

Accurate measurement of glass transition temperature and coefficient of thermal expansion (CTE) is of great significance in guiding the use and process performance of the materials. This manuscript measures the CTE and glass transition temperature of samples by the thermal expansion method, and systematically researches the measurement factors affecting the glass transition temperature and the CTE, including the shape and size of the samples, the starting furnace temperature, and the heat treatment process, etc. The study shows that the sample shape and size, the starting furnace temperature and the heat treatment process all have an effect on the test results. At the same time, the placement of the sample and the data processing process will also make the test results will deviate from the real value. Therefore, in order to accurately assess the thermal properties of the material, the processing size of the sample is specified to be 6 mm in diameter and 50 mm in length, while the initial temperature of the furnace during the CTE test should be lower than 35 °C. In addition, test samples of the same glass grade should undergo the same heat treatment process to ensure the accuracy of the test results.

Electrical discharge machining (EDM) is a highly effective and widely utilised unconventional manufacturing technology primarily used to produce complicated forms in materials that are challenging to machine. This versatile manufacturing approach finds applications in producing diverse items such as surgical instruments, aerospace components, automotive parts, and dies and moulds. Despite its manifold advantages, this method presents notable drawbacks, including relatively modest material removal rates (MRR), significant tool wear rates (TWR/EWR), and notable surface roughness (SR). The current paper examines numerous approaches used by researchers to enhance the functionality of EDM and the scope for upcoming research. The effects of various circuit and non-circuit characteristics on performance metrics like MRR, TWR, SR, etc., are listed. The impact of different electrode material, dielectrics, and their alterations on machining performance are carefully examined. Furthermore, the paper elucidates a range of advanced EDM iterations developed to enhance performance through cutting-edge technologies. It delves into research findings concerning the environmental sustainability of EDM. It also examines various theoretical models that have been put out to describe EDM's spark generation and material removal processes. The report’s final section provides a summary of the potential areas for EDM research in the future. The investigation has shown that material removal in EDM is a complicated process. The correct electrode and dielectric material must be chosen, and their properties must be adjusted to fit the type of workpiece material for it to be effective. The choice of circuit parameters is also affected by the type of workpiece material. The effectiveness of EDM in machining metal matrix composites, ceramics, and nanomaterials requires more investigation.

By combining formulas known from the literature that relate thermoelectric parameters, the expression n≅1.13∙10¹⁹e^Sr-2/r_H(e^Sr-2-0.17) is obtained. That is, the  concentration of charge carriers can be determined using the Hall resistance and reduced Seebeck coefficient. Since these two parameters are calculated using the Seebeck coefficient, this coefficient is sufficient to determine the  concentration. To demonstrate the use of the obtained new formula, experimental data on SiGe thermoelectric are discussed.

The isothermal section of the ternary systems Au-Pd-Ti and Au-Rh-Ti at 1000°C was studied using the diffusion couple technique. These alloying systems are relevant for various technical applications, as functional materials e.g. high temperature shape memory alloys, brazing filler metals, luxury items or biomedical implants. The research presents, for the first time, a comprehensive determination of phase relations and tie-triangles in these systems, identifying solid solubility of the various intermetallic compounds. The binary intermetallic compounds of Au and Pd with Ti show a large solubility of the third alloying element, where Au and Pd replace each other a fixed Ti content. A complete solid solubility was observed between TiAu2 and αPd2Ti. The binary phases with B2 structure form a large single phase field with (βTi) that surrounds the phase field of Ti3Au. Moreover, this research sets the groundwork for further investigations into these alloys, recommending specific sample compositions for future studies to refine understanding of phase boundary definitions.

In pursuit of enhancing the high-temperature service performance of Pt-10Rh alloys, this study focuses on the preparation of two Pt-10Rh-based alloys through the incorporation of reinforcing elements zirconium and zirconium/yttrium. The investigation into the microstructure, mechanical properties, and strengthening mechanisms of the alloys involved the utilization of analytical tools such as an optical metallographic microscope (OM), X-ray diffractometer (XRD), selected area electron diffraction (SAED), energy spectrum (EDS) and tensile tester, coupled with first-principle computational analysis methods. The research results indicate the presence of Pt5Y precipitate phase and zirconium yttrium oxides in Pt-10Rh-0.5Zr-0.2Y alloy, but not detected in Pt-10Rh-0.5Zr alloy. It was found that adding a small amount of zirconium and yttrium elements to Pt-10Rh alloy can significantly enhance the mechanical properties at room temperature and 1300 ℃, especially the composite addition of zirconium and yttrium elements, which can also improve obviously the high-temperature plasticity of the alloy. The strengthening mechanisms of zirconium and yttrium elements on Pt-10Rh alloy are mainly solid solution strengthening and second phase strengthening. The relationship between the mechanical properties of platinum-rhodium based alloys and their valence electron structure was discussed. The zirconium and yttrium reinforced platinum-rhodium based alloy studied in this work can replace Pt-10Rh alloy in certain fields.

In this work, we review the latest progress in single atom alloy (SAA) catalysis and its applications to thermal, photo- and electro-catalysis in processes. We also discuss SAA catalyst preparation methods as well as characterisation techniques and provide perspectives on scalability and potential manufacturing routes. Lastly, we provide perspectives on challenges and opportunities in SAAs, when moving towards industrial exploitation and realising the benefits offered by SAAs beyond laboratory-based research.

The article presents the results of a study of the influence of normalizing at 900 °C and high-temperature tempering at 650 °C on the microstructure and mechanical properties of cast steel 20GL. Heat treatment modes with and without high-temperature tempering were analyzed taking into account the geometric dimensions of the specimens. The microstructure and structural-phase composition of cast steel specimens after heat treatment were studied using transmission and scanning electron microscopy and X-ray diffraction analysis. Results showed that the selected mode ensures noticeable changes to ferrite-pearlite, homogeneous, fine-grained structure with grain size number 9 and Brinell hardness 170 HB. Mechanical tests for static tensile and impact strength resulted in selection of the optimal content of manganese in studied cast steel as 1.2 wt. %. It has been established that the processes of final deoxidation have the greatest influence on the mechanical properties of steel determining the nature and character of non-metallic inclusions.

Slurry erosion (SE) is a mechanically induced wear observed in concerned industries transiting the mixture of liquid and erodent particles, either naturally or affectedly. The kindred equipment and pipelines need frequent monitoring and slurry erosion prediction to check the severity of erosion for implementing preventive measures to minimize the damage of erosion wear. Experimental investigation/online condition monitoring is very high priced and provide fair idea about the extent of slurry erosion wear; nevertheless, precise prediction of slurry erosion wear requires in-situ operating conditions. To minimize expenditure on slurry erosion testing/monitoring and accurate slurry erosion prediction, tribological modeling of slurry erosion wear by mathematical approach or computer-based simulations has proved to be an excellent approach by numerous researchers to foresee the slurry erosion wear and control its severity. Several authors in the past have aligned their efforts in this direction. This review is an attempt to estimate the progress in the variety of tribological modeling (primarily mathematical models) of slurry erosion for its forecasting, monitoring and to suggest the apt approach for the modeling of slurry erosion wear, especially for hydro-turbine components. This article covers the research studies pertaining to mathematical wear models for solid particle erosion recommending a commencing approach for slurry erosion wear modeling.

This study evaluates the antimicrobial efficacy of Ta-Cu and Nb-Cu coatings, applied via magnetron sputtering on 3D-printed porous Ti6Al4V alloy scaffolds and gas-abrasive treated Ti6Al4V alloy, against Staphylococcus aureus and Candida albicans. Scanning electron microscopy with energy-dispersive X-ray analysis verified the application of coatings with 25 wt.% Cu, at thicknesses of 2 μm and 10 μm, to scaffolds (72% porosity) and roughened Ti6Al4V alloy (mean areal roughness of 4.6±1 µm). Thicker coatings showed superior antimicrobial activity; however, thin Nb-Cu coatings and uncoated alloy did not exhibit inhibitory effects. The release dynamics of Cu ions from Ta-Cu coatings into physiological solution, analysed over three days via inductively coupled plasma mass spectrometry, matched the inhibition zone growth. These findings support the potential of these coatings in developing endoprosthesis implants with enhanced antimicrobial properties.

The present work adopts friction stir processing to process SS304 with CoCrFeCuTi and AlSiBeTiV High Entropy Alloy (HEA) and analyse its erosion performance. The processed samples with CoCrFeCuTi and AlSiBeTiV display refined grain structure with uniform distribution of the reinforced HEAs. The microhardness for the sample with CoCrFeCuTi is 22.1% better than the AlSiBeTiV. The slurry jet erosion test conducted through different process parameters revealed 90° impingement angle and 10 m/s impact velocity with 10 wt% slurry concentration on the processed sample with CoCrFeCuTi offered better erosion resistance. Oblique angle endured high erosion rate due to the ploughing effect of abrasive erodent than normal angle deforming the surface. Increasing velocity increased the erosion rate by increased material removal. Slurry concentration forms a cloud-like layer at higher concentrations lowering the erosion rate. The subsequent microstructural evaluation showed the failure mode through the formation of platelets, micro-cuts, ploughing, and plastic deformation.

This study aims to coat Ti6Al4V alloy with Ti-xHA (x=2.5-10wt.%) mixture to improve its surface properties. A new approach using a powder metallurgical pressure-assisted sintering method was applied to the coating process. The in-situ sintering and coating process was performed at 950°C for 45 min in a vacuum atmosphere of 10-4 mbar. A pressure of 50MPa was applied during the sintering process. Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922) cultures were used to determine the antibacterial activity of the sintered and coated samples. The electrochemical properties of the samples were studied by Tafel extrapolation and potentiodynamic polarization tests. The results showed that the coating layer containing wt.%7.5 of HA increased the antibacterial property against gram-positive and gram-negative bacterial cultures. Furthermore, it was determined that the icorr value of the material decreased, and the corrosion resistance improved with an increasing HA ratio. In addition, no active-passive oxidation zone formation was observed up to 2000 mV in the HA-added samples.