Study of ph effect on AZ31 magnesium alloy corrosion for using in temporary implants

Currently, magnesium alloys are gaining great interest for medical applications due to their degrading properties in the human body ensuring a great biocompatibility. These alloys also provide profitable mechanical properties due similarities with human bone. However, a difficulty in applying these materials in the biomaterials industries is the corrosion prior to cell healing. The effect of the chemical composition of Mg alloys on their corrosion behavior is well known. In this study, samples of AZ31 magnesium alloy were cut into chips for elemental chemical analysis by neutron activation analysis (NAA). Concentrations of the elements As, La, Mg, Mn, Na, Sb and Zn were determined in the AZ31 alloy. Visualization tests of agar corrosion development in various media, of 0.90% sodium chloride solution (mass), phosphate buffer saline (PBS) and simulated body fluid (SBF) were performed. Visualizations of the effect of agar gel corrosion revealed pH variation during the corrosion process due to the released into the cathode. The highest released of hydroxyl ions occurred in NaCl solution compared to PBS and SBF solutions indicating that NaCl solution was much more aggressive to the alloy compared to the others.

Development of Solutions for Chemical Phosphating of Carbon Steel

A consumer in Uzbekistan imports concentrates phosphating the surface of carbon steels, such as, for example, Foscon 35 and Foscon 35K. (Russia). Work has been done to create analogs from local raw materials. Having studied the physicochemical properties of the concentrates, a mechanism for the formation of protective phosphate coatings was suggested, and the components of a new phosphating composition were selected. The aim of the work was to develop a composition of a solution for chemical phosphating of the surface of carbon steel at the local resource base. Methods used: elemental chemical analysis, electrochemical and corrosion measurements, conditionally total acidity of solutions was measured according to TU 2149-205-10964029-2004 (Russia). The effect of temperature, pH of the medium, and the exposure time of the sample in the phosphating solution on the quality of the phosphate film was studied. As a result, a phosphating composition FK-1 was developed, functionally similar to imported concentrates Foscon 35 and Foscon 35K, based on local raw materials.

Zapote Seed (Pouteria mammosa L.) Valorization for Thermal Energy Generation in Tropical Climates

According to the Law for the Use of Renewable Energies and the Financing of Energy Transition, Mexico’s goal for 2024 is to generate 35% of its energy from non-fossil sources. Each year, up to 2630 tons of residual biomass from the zapote industry are dismissed without sustainable use. The main purposes of this study were to determine the elemental chemical analysis of the zapote seed and its energy parameters to further evaluate its suitability as a solid biofuel in boilers for the generation of thermal energy in a tropical climate. Additionally, energy, economic, and environmental assessments of the installation were carried out. The results obtained show that zapote seed has a higher heating value (18.342 MJ/kg), which makes it appealing for power generation. The Yucatan Peninsula is the main zapote-producing region, with an annual production of 11,084 tons. If the stone of this fruit were used as biofuel, 7860.87 MWh could be generated and a CO2 saving of 1996.66 tons could be obtained. Additionally, replacing a 200 kW liquefied petroleum gas (LPG) boiler with a biomass boiler using zapote seed as a biofuel would result in a reduction of 60,960.00 kg/year of CO2 emissions. Furthermore, an annual saving of $7819.79 would be obtained, which means a saving of 53.19% relative to the old LPG installation. These results pave the way toward the utilization of zapote seed as a solid biofuel and contribute to achieving Mexico’s energy goal for 2024 while promoting sustainability in universities.

Ammonium Hydroxide Mediated Hydrothermal Crystallization of Hydroxyapatite Coatings on Titanium Substrate

Controlled growth of hydroxyapatite (HAp) coatings on titanium substrate plays an important role in the fabrication of the composites for bone tissue engineering. We describe the synthesis of the crystalline hydroxyapatite coatings on the Ti/TiO2 substrate through a hydrothermal method by using ethylenediamine tetraacetic acid disodium salt (Na2EDTA) and varying concentrations of ammonium hydroxide (NH4OH) in calcium-phosphate precursor solution. Na2EDTA serves as a chelating agent, while NH4OH is used as an alkaline source and crystal growth modifier. We characterized the HAp coatings using x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. We also performed the elemental chemical analysis by means of a particle induced x–ray emission method. Our results show that there is a pH limit for which the hydrothermal deposition of HAp on titanium occurs. Moreover, we observed that NH4OH had a measurable influence on the coating thickness as well as on the size and shape of the HAp crystals. We found that with the increase of NH4OH concentration, the thickness of the Hap layer increases and its morphology changes from irregular flakes to well-defined hexagonal rods.

Effect of Small Additions of Cr, Ti, and Mn on the Microstructure and Hardness of Al–Si–Fe–X Alloys

The Al–Si–Fe system has drawn the attention of the scientific community due to its capacity to replace parts in several manufacturing industries, as this alloy system is very sensitive to small additions of transition metals. Therefore, the aim of this work is to study the effect of Cr, Ti, and Mn additions in the Al–20Si–5Fe (wt. %) alloy and to study the modification of the iron intermetallic and the microstructural refinement through the formation of secondary phases. Al–20Si–5Fe–X (X = Cr, Mn and Ti at 1.0, 3.0, and 5.0 wt. %) alloy ingots were prepared by arc melting furnace. The elemental chemical analysis was performed by X-ray fluorescence spectrometry (XRF). The microstructure of all samples was investigated by scanning electron microscopy and X-ray diffraction. Finally, microhardness was measured in order correlate the hardness with the formation of the different compounds. The highest hardness was found for the alloy with the 5 wt. % Cr. The addition of Ti and Mn raised the hardness by ~35 HVN (Vickers microhardness) when compared to that of AlSiFe master alloy. Important changes were also observed in the microstructure. Depending on the Cr, Ti, and Mn additions, the resulting microstructure was dendritic (CrFe), acicular (Ti5Si3), and “bone like” (Mn0.2Fe0.8), respectively.

The use of rapid prototyping in the joining of fractured historical silver object

Purpose This paper aims to present a proposal for the restoration of a silver crown by means of fitting pieces produced by the process of 3D modelling and rapid prototyping. It also analyses the benefits of this procedure in restoration of objects weakened by corrosive processes. Design/methodology/approach Elemental chemical analysis was carried out in the alloy used in the manufacture of the crown and the constructive and corrosive processes present were studied. Three fitting pieces were modelled and prototyped in wax casting by the stereolithography apparatus system aiming to restore the part and protect the original metal against impacts and external tensions which could speed up some deterioration processes. Findings The procedure presented in this paper has shown that formal and dimensional accuracy, only achieved by means of 3D technologies, made the restoration and mechanical stability of the crown possible without the use of adhesives or welding. Originality/value The proposed procedure is a new restoration alternative which causes minimal impact to the object and abides by the main standards for modern conservation. It is made with metal which is compatible with the original piece, retractable and easily identifiable.

Elemental Chemical Analysis by X-ray Fluorescence of Calcarenite Stones Used in Historical Monuments Building of Rabat (Morocco)

A good knowledge of chemical properties, thermophysical and petrophysical parameters, makes it possible to understand the mechanisms of alteration of historical monuments, and to predict solutions limiting their evolution. The main objective of this work is chemical analysis by X-ray fluorescence spectrometry on calcarenite stones, often used as a building material for historical monuments of Rabat (Morocco), in order to identify the nature of the rock. The elemental chemical composition shows high concentrations of CaO and SiO2, which confirms that the main phases of the calcarenite rock studied are calcite and quartz. These are the characteristic minerals of calcareous rocks.

Authentication and Evaluation of the Technique of Minting the Romanian Coins of the 20th Century. I

The present work highlights the results of optical and electronic microscopy analyses performed on fifteen selected outdated 20th century Romanian coins. The obtained results brought significant contributions in establishing specific archaeometric characteristics of corrosion coins products generated within the in-use and demonetization periods, under the action of both natural and anthropogenic factors. The work was mainly aimed in identifying the nature of the alloy and of the raw material used during coins minting, with specific emphasize on their resistance toward the action of various natural and anthropogenic factors. Emphasize is also given to the manufacturing techniques, edition characteristics and the in-use-interval. Performed elemental chemical analysis clearly showed that major elements abundances are highly correlated with coins origin area and their minting period.

Doped Ti-pillared clays as effective adsorbents – Application to methylene blue and trimethoprim removal

Environmental contextWater is an essential compound for life; however, several factors limit the amount available for human consumption. Every day, thousands of pollutants are discharged into drinking water. Here, new materials that are efficient as adsorbents and photocatalysts for pollutants are reported. AbstractMontmorillonite was treated with Ti-based solutions doped with various transition metal cations, leading after calcination at 500°C to new doped Ti-pillared montmorillonite solids. These solids were characterised by elemental chemical analysis, powder X-ray diffraction, Fourier-transform (FT)-IR spectroscopy, thermal analyses, nitrogen adsorption, acidity evaluation and electron microscopy. The performance of these solids in the degradation of methylene blue and the adsorption of trimethoprim was evaluated.