INFLUENCE OF NI AS MINORITY ALLOYING ELEMENT ON THE CORROSION BEHAVIOR OF AMORPHOUS AL-CU-MG ALLOYS IN CHLORIDE SOLUTION

The influence of nickel as minority alloying element on the corrosion behavior of amorphous alloys (Al74Cu16Mg10)99Ni, (Al74Cu16Mg10)98Ni2 and (Al74Cu16Mg10)97Ni3 was investigated. The amorphous alloys were obtained as ribbons by Chill Block Melt Spinning (CBMS). The amorphous structure of the alloys was proven by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corrosion rate was calculated gravimetric using continuous immersion tests for 360 hours in 3.5% NaCl solution at a temperature of 25oC. The lowest corrosion rate was found in the alloy containing 3 at. % Ni. The chemical composition of the accumulated corrosion products was studied using XRD.The influence of nickel on the local corrosion resistance of the amorphous ribbons of (Al74Cu16Mg10)100-хNiх x = 0, 1, 2, 3% alloys was investigated electrochemically in a solution of 3.5% NaCl at 25°C. Pitting potential (Epitt) and repassivation potential (Erp) were determined. It was found that most resistant to pitting corrosion was the (Al74Cu16Mg10)97Ni3 alloy, which showed the noblest pitting potential (Epitt -0.332 V) and repassivation potential (Erp -0.530 V).All obtained corrosion test results of the nickel-containing amorphous alloys were compared to the base amorphous Al74Cu16Mg10 alloy.

INVESTIGATION OF THE INFLUENCE OF DIFFERENT MODIFIERS ON THE EUTECTIC SI IN THE COMPOSITION OF ALSI18 ALLOY

The structure of hypereutectic aluminum-silicon alloys consists of primary silicon crystals arranged in a eutectic matrix. In the present work the influence of different types of modifiers on the size and shape of the silicon crystals in the composition of the eutectic of the AlSi18 alloy has been studied. The classic for this type of alloys modifier (phosphorus), as well as the nanomodifiers SiC and nanodiamonds (ND) have been used. The results of the microstructural analysis show that the three modifiers used affect differently the shape and size of the eutectic silicon of the investigated alloy

EFFECT OF CU AS МINORITY АLLOYING ЕLEMENT ON GLASS FORMING ABILITY AND CRYSTALLIZATION BEHAVIOR OF RAPIDLY SOLIDIFIED AL-SI-NI RIBBONS

The influence of copper as a minority alloying element in the process of rapid solidification of Al-Si-Ni ribbons produced by Chill Block Melt Spinning (CBMS) was investigated. XRD and TEM analyses proved a completely amorphous structure of the alloys Al74Ni16Si10 and (Al74Ni16Si10)98Cu2. The crystallization behaviour of these alloys was studied by DSC analysis. It was found that the crystallization of the amorphous alloys (Al74Ni16Si10)100-xCux, x=0, 2 runs in two steps. The temperatures Tx1 and Tx2 of each of the crystallization steps were determined. It was proven that the addition of 2 at. % copper does not significantly change Tx temperatures. The temperature difference ΔTx was calculated and it showed that more thermally stable is the copper containing alloy. Crystalline analogues of the amorphous alloys were obtained by annealing of the melt-spun amorphous ribbons at a temperature which exceeded by 170°C the onset crystallization temperature. The type and size of separated crystalline phases were determined by XRD. It was found that the addition of 2 at. % Cu to Al74Ni16Si10 alloy causes a separation of new phases - Cu3.8Ni and (Al, Cu)Ni3 and 54%, 24% and 7% size increase of the phases Al, Al3Ni, NiSi2 respectively

Rheological Behavior of a New Amorphous Alloy (Al74Cu16Mg10)99,7Zr0.3

A new amorphous alloy (Al74Cu16Mg10)99,7Zr0.3 was prepared the applying a melt-spinning technique. Temperature dependence of viscosity of the alloy was determined using data from a PerkinElmer TMS2 thermo-mechanical analyzer processed according to a methodology based on the Free Volume Model (FVM). The strength of the alloy was calculated according to the Yang equation and the glass-forming ability was calculated according to the values of the Angell index mA. The activation energy of crystallization and the activation energy of the glass transition were computed using data from differential scanning calorimetry and thermomechanical experiments respectively. The activation energy of crystallization Еx = 168 ± 3.7 kJ/mol, was found to be higher than the activation energy of the glass transition Еg = 156 ± 1.4 kJ/mol, which means a dominant contribution of the atomic transport barrier, compared to the nucleation barrier. The relatively high temperature interval of the supercooled melt state Tx-Tg = 32 K and the low viscosity values in the same range ƞ(Тg) = 3.40E + 11 Pa.s and ƞ(Тx) = 1.87E + 10 Pa.s would allow thermomechanical treatment of the alloy in the temperature range of supercooled melt

Modified Approach Using Mentha arvensis in the Synthesis of ZnO Nanoparticles—Textural, Structural, and Photocatalytic Properties

Zinc oxide arouses considerable interest since it has many applications—in microelectronics, environmental decontaminations, biomedicine, photocatalysis, corrosion, etc. The present investigation describes the green synthesis of nanosized ZnO particles using a low-cost, ecologically friendly approach compared to the classical methods, which are aimed at limiting their harmful effects on the environment. In this study, ZnO nanoparticles were prepared using an extract of Mentha arvensis (MA) leaves as a stabilizing/reducing agent, followed by hydrothermal treatment at 180 °C. The resulting powder samples were characterized by X-ray diffraction (XRD) phase analysis, infrared spectroscopy (IRS), scanning electron microscopy (SEM), and electron paramagnetic resonance (EPR). The specific surface area and pore size distribution were measured by the Brunauer–Emmett–Taylor (BET) method. Electronic paramagnetic resonance spectra were recorded at room temperature and at 123 K by a JEOL JES-FA 100 EPR spectrometer. The intensity of the bands within the range of 400–1700 cm−1 for biosynthesized ZnO (BS-Zn) powders decreased with the increase in the Mentha arvensis extract concentration. Upon increasing the plant extract concentration, the relative proportion of mesopores in the BS-Zn samples also increased. It was established that the photocatalytic performance of the biosynthesized powders was dependent on the MA concentration in the precursor solution. According to EPR and PL analyses, it was proved that there was a presence of singly ionized oxygen vacancies (V0+) and zinc interstitials (Zni). The use of the plant extract led to changes in the morphology, phase composition, and structure of the ZnO particles, which were responsible for the increased photocatalytic rate of discoloration of Malachite Green dye