The dependence of the strength of a Cu/Ni/Au|AuSn solder joint on the conditions of the galvanic deposition process for the nickel barrier layer is studied. It is shown that when using a succinic acid-based electrolyte, the introduction of poorly soluble nickel succinate into the deposited layer can reduce the strength of the solder joint. The key factor controlling the occurrence of this undesirable process is the pH of the electrolyte. This paper attempts to reconstruct the relationship between solder joint strength and the conditions for the formation of a galvanic Ni barrier layer. Graphs of the peel force versus the pH of the nickel plating electrolyte, changes in electrolyte pH depending on the number of parts processed, and calculated equilibrium concentrations of nickel complexes in the electrolyte that affect the quality of the resulting coating are presented. Using mathematical modeling, an attempt was made to predict the redistribution of nickel complexes when adjusting the electrolyte composition and pH using various methods. The calculated strength results were compared with those obtained in practice. Approaches to mitigating the negative effect of nickel succinate are proposed.

A comprehensive study of lithium iodate (α-LiIO₃) single crystals grown from mother solutions by the isothermal evaporation method has been conducted. The main focus was on the investigation of the microstructure, optical and mechanical properties, and their anisotropy. Significant microstructural heterogeneity was revealed using methods of selective chemical etching and scanning probe microscopy. It was shown that the lateral crystal growth is characterized by an anomalously high defect density (10⁵–10⁷ cm^-2) and increased surface roughness (25 nm compared to 2 nm in the central part), as well as a complex zonal and sectorial structure. Detailed measurements of Knoop and Vickers microhardness on various crystallographic planes were performed. Anisotropy of the second kind was discovered: maximum values were recorded on pyramidal faces {10Ī1} (278–283 kgf/mm²), while minimum values were found on prismatic faces {10Ī0} (221–248 kgf/mm²). No anisotropy of the first kind was observed on the Z-cut plane. It was demonstrated that microhardness decreases along the crystal height, which is associated with a gradient of microimpurity concentration, maximum at the beginning of growth (near the seed). Based on the analysis of the microstructure and sectorial structure, a mechanism of brittle crystal fracture under mechanical impact (shock) along sector boundaries is proposed, caused by heterogeneity and dislocation pile-ups. The obtained results are important for understanding the relationship between growth conditions, microstructure, and mechanical properties of LiIO₃ crystals, which expands the possibilities for their practical application in nonlinear optical devices and allows for the optimization of processing methods.

The results of a systematic study of propylene carbonate (PC) based organic electrolytes with alkylammonium tetrafluoroborates for use in supercapacitors (SC) designed for wearable electronics and self-charging power supplies are presented. The relevance of the study is due to the requirement to combine high specific energy of SC, electrochemical stability over a wide temperature range and safety during operation, especially as part of miniature autonomous devices. Unlike acetonitrile (AN), which is traditionally used in electrolytes for SC, PC is nontoxic and fireproof, however, its high viscosity limits the electrical conductivity of electrolytes, which makes it critically important to choose the optimal salt. The properties of PC-based electrolytes with tetrafluoroborates of tetraethylammonium (TEA·TFB), methyltriethylammonium (TEMA·TFB), spiro-(1,1')-bipyrrolidinium (SBP·TFB) and 1,1-dimethylpyrrolidinium (DMP·TFB), differing in size and structure of cations (acyclic and cyclic), have been studied. All the salts studied provide similar capacitance characteristics of SC cells, but TEA·TFB exhibits slightly lower values due to the larger size of the cation. Salts with cyclic cations (SBP·TFB and especially DMP·TFB) provide significantly wider operating voltages at temperatures elevated to 85 °C, while electrolytes with TEA·TFB and TEMA·TFB degrade at temperatures above 60 °C. Resource tests (up to 70,000 cycles at temperatures of 50-95 ℃) have confirmed the electrochemical and thermal stability of the DMP·TFB+PC electrolyte: SC cells with this electrolyte retain 80% of their original capacity after 50,000 cycles of galvanostatic charge-discharge and allow the use of an operating voltage up to 3.0 V. The recommended temperature range for the operation of SC with DMP·TFB+PC electrolyte is 0 °C – 85 °C with the possibility of a short-term temperature increase to 95 °C. At temperatures below 0 °C, an increase in viscosity leads to a sharp decrease in capacitance characteristics. Thus, an electrolyte based on PC and DMP·TFB salt is promising for SC in terms of use in wearable electronics devices.