Mechanical Analysis and Corrosion Analysis of Zinc Alloys for Bioabsorbable Implants for Osteosynthesis

Zinc alloys have recently been researched intensely for their great properties as bioabsorbable implants for osteosynthesis. Pure zinc (Zn) itself has relatively poor strength, which makes it insufficient for most clinical use. Research has already proven that the mechanical strength of zinc can be enhanced significantly by alloying it with silver. This study evaluated zinc silver alloys (ZnAg) as well as novel zinc silver titanium alloys (ZnAgTi) regarding their mechanical properties for the use as bioabsorbable implants. Compared to pure zinc the mechanical strength was enhanced significantly for all tested zinc alloys. The elastic properties were only enhanced significantly for the zinc silver alloys ZnAg6 and ZnAg9. Regarding target values for orthopedic implants proposed in literature, the best mechanical properties were measured for the ZnAg3Ti1 alloy with an ultimate tensile strength of 262 MPa and an elongation at fracture of 16%. Besides the mechanical properties, the corrosion rates are important for bioabsorbable implants. This study tested the corrosion rates of zinc alloys in PBS solution (phosphate buffered solution) with electrochemical corrosion measurement. Zinc and its alloys showed favorable corrosion rates, especially in comparison to magnesium, which has a much lower degradation rate and no buildup of hydrogen gas pockets during the process. Altogether, this makes zinc alloys highly favorable for use as material for bioabsorbable implants for osteosynthesis.

STUDY OF THE PROPERTIES OF DIFFUSION-HARDENING COMPOSITE SOLDERS MODIFIED WITH A Ti-Mo POWDER MIXTURE

В статье обсуждается возможность регулирования свойств диффузионнотвердеющего припоя на основе легкоплавких сплавов галлий-олово, галлий-индийолово, галлий-олово-цинк и твердой компоненты состоящей из порошка сплава медь-олово посредством введения смеси инертных порошков металлического титана и молибдена после термической обработки при различных температурах. Оценена микротвердость и термическая устойчивость композиционных диффузионнотвердеющих припоев. Показано, что термическая обработка при более высоких температурах способствует переходу припоя в равновесное состояние, при этом происходит резкое увеличение твердости. Методом рентгенофазового анализа определены образующиеся в результате диффузионного твердения фазы. Показано, что при различных температурах обработки образуются разные фазы - наноразмерные интерметаллические соединения. За счет небольших добавок наполнителей, инертных или слабовзаимодействующих с галлием, но хорошо им смачиваемых, характеристики диффузионно-твердеющего припоя значительно улучшаются. The article discusses the possibility of regulating the properties of diffusion-hardening solder based on low-melted gallium-tin, gallium-indium-tin, gallium-tin-zinc alloys and a solid component consisting of a copper-tin alloy powder by introducing a mixture of inert powders of metallic titanium and molybdenum after the heat treatment at various temperatures. The microhardness and thermal stability of composite diffusion-hardening solders are evaluated. It is shown that the heat treatment at higher temperatures contributes to the transition of the solder to an equilibrium state, while a sharp increase in hardness occurs. The phases formed as a result of diffusion hardening were determined by the method of X-ray phase analysis. It is shown that at different processing temperatures, different phases are formed - nanoscale intermetallic compounds. Due to small additives of fillers that are inert or weakly interacting with gallium, but are well wetted by it, the characteristics of the diffusion-hardening solder are significantly improved.

Anodic behaviour of Zn0.5Al doped with molybdenum in acidic, neutral and alkaline media

The paper presents the results of a potentiodynamic study of the anodic behaviour of Zn0.5Al doped with molybdenum in the acidic (0.1 M, pH = 1; 0.01 M, pH = 2; 0.001 M, pH = 3), neutral (0.03, 0.3, 3%, pH = 7) and alkaline (0.001 M, pH = 10; 0.01 M, pH = 11; 0.1 M, pH = 12) media of HCl, NaCl and NaOH electrolytes. In the potentiodynamic mode with an electrode potential sweep rate of 2 mV/s, all Zn0.5Al-Mo samples containing from 0.01 to 1.0 wt% of molybdenum demonstrated a shift in the potentials of corrosion, pitting formation and repassivation. These potentials shift towards negative values in acidic and alkaline media, while shifting to positive values in a neutral medium. It was established that an increase in the concentration of electrolytes led to a shift of all the considered potentials towards negative values in all media - acidic, neutral and alkaline. This dependence is associated with the specific features of the process of anodic dissolution of alloys during the formation of an oxide film on their surface. The significance of the dependence of the stationary potential of free corrosion of alloys on time for establishing the passivity of surfaces in acidic, neutral and alkaline media was shown. It was determined that zinc alloys doped with molybdenum are resistant to pitting corrosion in all the investigated media. This resistivity is particularly high in acidic (0.001 M), neutral (0.03%) and alkaline (0.001 M) media of HCl, NaCl and NaOH electrolytes. The favourable effect of molybdenum on both the anodic behaviour of Zn0.5Al and the overall increase in the corrosion resistance of alloys was demonstrated. In comparison with undoped Zn0.5Al alloys, the corrosion rate of alloys doped with molybdenum (0.01-1.0 wt%) is 2-2.5 times lower. The proposed compositions of Zn0.5Al-Mo alloys can be used as noncorrosive coatings for steel products.

New data on the chemical composition of the non-ferrous metal products of the X–XVIII centuries on the territory of Northern and Central Belarus

The article presents the results of analysis of new data on the elemental composition of non-ferrous metal products on the territory of certain archaeological sites in Northern and Central Belarus. The author distinguishes two main stages in the non-ferrous metalworking of the region: the X–XIII centuries and XIV–XVIII centuries. It is noted that the period of the X–XIII centuries is characterized by a significant predominance of copper-zinc alloys with average and high concentrations of zinc in metal. Meanwhile, bronze alloys also play an important role, accounting for 35 % of the total number of the items studied. Samples made of copper-zinc and bronze alloys are also characterized by a significant amount of lead. As a result of the analysis of the data on the elemental composition of non-ferrous metal products of the XIV–XVIII centuries, it is concluded that non-ferrous metalworking of this period is characterized by the continuity of traditions with handicraft production of the previous period, which manifested itself in the widespread use of copper-zinc alloys, as well as of tin-lead and multicomponent bronzes. At the same time, a significant difference is the increase in the proportion of alloys with high concentrations of alloying components.