Search Results (4)

Zinc-based alloys are promising candidates for biodegradable implant applications; however, their rapid initial corrosion and limited cytocompatibility remain major challenges. In this study, a Zn-Ca-P layer in a form of parascholzite (CaZn₂(PO₄)₂·2H₂O) was prepared on a Zn-0.8Mg-0.2Sr alloy via anodic oxidation followed by short-time biomimetic calcium–phosphate deposition. The formation mechanism, corrosion behaviour, and preliminary biological response of the modified surface were systematically investigated. The Zn-Ca-P layer formed a compact and crystalline phosphate layer that significantly altered the corrosion response of the zinc substrate in Leibovitz L-15 medium containing foetal bovine serum. Electrochemical measurements revealed a pronounced improvement in corrosion resistance and a transition from rapid active dissolution to a controlled, ion-exchange-driven degradation mechanism. The moderate solubility of parascholzite enabled the gradual release of Zn²⁺ and Ca²⁺ ions while maintaining surface stability during immersion. Preliminary cell adhesion experiments demonstrated a clear enhancement of cytocompatibility for the Zn-Ca-P-layer-coated samples, where cells readily adhered and spread, in contrast to the bare alloy surface, which showed lower cell attachment. The improved biological response is attributed to the phosphate-rich surface chemistry, favourable surface morphology, and moderated corrosion behaviour. Overall, the parascholzite-like layer provides an effective strategy with which to regulate both corrosion and early cell–material interactions of zinc-based biodegradable alloys, highlighting its potential for temporary biomedical implant applications. Full article

One of the challenges in agriculture practices is guaranteeing an adequate and bioavailable phosphorus supply for plants on phosphorus-deficient soils. A promising alternative lies in the utilization of phosphate nano-fertilizers (NFs) through spray applications. Therefore, this short-term study aimed to investigate the yet undetermined widespread impact of P-NFs on crops characterized by broad leaves, an intensive rate of photosynthesis, and belonging to the oilseed plant, sunflower (Helianthus annuus L.). To achieve this, NFs were applied at lower concentrations of various phosphate-based NFs, including (i) nano-hydroxylapatite (nano-Hap) and (ii) a mixture of nano-calcium zinc phosphate and macro-sized parascholzite (nano/macro-ZnPhos), in comparison to the NF-free control. The study was carried out under authentic field conditions during the 2022 vegetation season at the Dolná Malanta site within the Central European Region. The empirical evidence presented herein indicates that the utilization of biocompatible and bioactive nano-Hap, initially engineered for biomedical applications, and nano/macro-ZnPhos, now foliarly applied at reduced concentrations, elicited a statistically significant elevation in quantitative parameters and seasonal physiological responses. The parameters analyzed included head diameter, dry head weight, seed yield per hectare, nutritional seed oiliness, etc. as well as the physiological normalized difference vegetation index (NDVI), stomatal conductance index (Ig), and crop water stress index (CWSI). In terms of agro-ecological terrestrial bio/diversity, it was evident that the nano/macro-ZnPhos was the most hospitable variant for the terrestric insect community, but surprisingly, the agronomically more popular nano-Hap showed only statistically insignificant changes in the diversity of the detected communities. However, the relevance of outcomes highlighted using nano-fertilizers, supporting the concept of precision and sustainable agriculture under field conditions. Full article

This study was carried out to investigate the effect of a complete exchange of Ca²⁺ with Zn²⁺ ions on the structure of brushite (CaHPO₄·2H₂O), which might be advantageous in the production process of Ca_xZn_1−xHPO₄·nH₂O. To acquire the starting solutions needed for the current study, (NH₄)₂HPO₄, Ca(NO₃)₂·4H₂O, and Zn(NO₃)₂·6H₂O were utilized in several molar concentrations. The findings indicate that Ca is partly substituted by Zn when the Zn/Ca molar ratio is below 0.25 and that Zn doping hinders the crystallization of brushite. A continued increase in the Zn/Ca molar ratio to 1 (at which point the supersaturation of the Zn solution rises) led to a biphasic compound of monoclinic brushite and parascholzite precipitate. Elevating the Zn/Ca molar ratio to 1.5 resulted in a precipitate of a parascholzite-like mineral. Finally, increasing the Zn/Ca molar ratio to 4 and above resulted in the formation of the hopeite mineral. Future biomaterial production with specific and bespoke characteristics can be achieved by adjusting the Zn/Ca ratio in the starting solution. It Rhas been established that the Zn/Ca ratio in the starting solution can be adjusted to obtain minerals with specific compositions. Thus, new synthesis methods for parascholzite and hopeite were introduced for the first time in this manuscript. Full article

The article presents a method for obtaining white phosphate coatings on steel by cold method. The deposition of protective phosphate coatings was carried out from solutions based on the preparation “Majef”, consisting of manganese and iron phosphates. To obtain phosphate films of white color, it is proposed to introduce zinc and calcium nitrates into phosphating solutions at the rate of 25–30 g/L. The surface of phosphate coatings was studied using the SolverP47-PRO atomic force microscope images, and the average grain size was determined. The structural and phase composition of phosphate coatings was been studied using X-ray diffraction analysis. The protective properties of phosphate coatings were estimated by corrosion rate indicators calculated from corrosion diagrams. Fine-crystalline uniform coatings were obtained from modified phosphating solutions at room temperature on steel. The white color of phosphate coatings is due to the increased content of phosphophyllite, hopeite, and parascholzite in their structural and phase composition. By applying protective phosphate coatings of white color on a steel product, corrosion can be slowed down by 4–4.5 times. However, white phosphate coatings are inferior in protective properties to unpainted coatings. The index of change in the mass of samples with white phosphate coatings because of corrosion is 0.371–0.41 g/(m²·h), and with unpainted coatings is 0.128 g/(m²·h). Full article