Magnesium Yttrium Research Articles

Effect of Temperature on the Complex Modulus of Mg-Based Unidirectionally Aligned Carbon Fiber Composites.

Composite materials based on magnesium-lithium (MgLi) and magnesium-yttrium (MgY) matrices reinforced with unidirectional carbon fibers were prepared using the gas pressure infiltration method. Two types of carbon fibers were used, high-strength PAN-based T300 fibers and high-modulus pitch-based Granoc fibers. The PAN-based carbon fibers have an internal turbostratic structure composed of crystallites. The pitch-based carbon fibers have a longitudinally aligned graphite crystal structure. The internal carbon fiber structure is crucial in the context of the interfacial reaction with the alloying element. There are various mechanisms of bonding to carbon fibers in the case of magnesium-lithium and magnesium-yttrium alloys. This paper presents the use of the DMA method for the characterization of the role of alloying elements in the quality of interfacial bonding and the influence on the complex modulus at increasingly elevated temperatures (50-250 °C). The complex modulus values of the composites with T300 fibers were in the range of 118-136 GPa. The complex modulus values of the composites with Granoc fibers were in the range of 198-236 GPa. The damping capacity of magnesium-based unidirectionally aligned carbon fiber composites is related to the quality of the interfacial bonding.

The Features of Return after Aging in Magnesium–Yttrium Alloy When Doped with Samarium

The Features of Return after Aging in Magnesium–Yttrium Alloy When Doped with Samarium

Effect of Alloy Microstructure on the Corrosion Behavior of Binary Mg-Y Alloys

In recent years, magnesium alloys continue to receive attention due to their low density and high specific strength compared to other metallic materials. However, the main disadvantage of magnesium alloys originates from the low standard reduction potential of magnesium (-2.37 VSHE), resulting in high reactivity in water-containing environments and susceptibility to corrosion reaction. This kind of corrosion phenomenon exists in most magnesium alloys, thus limiting their practical applications.At present, many studies showed that adding yttrium to magnesium can simultaneously improve its creep and corrosion resistance. Also, the standard reduction potential of yttrium is similar to that of magnesium, which implies that the galvanic corrosion effect due to the second phases or precipitates would be less pronounced with the addition of yttrium. Therefore, in this study, we investigated the influence of alloy microstructure on the corrosion behavior of two binary magnesium-yttrium (Mg-Y) alloys with different yttrium content.To understand the dominant features during corrosion tests, this study used an in situ optical microscope (OM)/three-electrode setup to monitor the evolution in corrosion potential and surface corrosion morphology with immersion times of the Mg-Y alloys. With this setup, serious localized corrosion was observed on the Mg-1wt%Y sample. In contrast, localized corrosion on the Mg-7wt%Y sample is mitigated, and the corrosion rate is maintained at a similar level over time. Even though the addition of more Y results in more second phases or precipitates, which could cause some galvanic effect, the corrosion propagation is delayed by the second phase distribution. Through further observation in scanning electron microscope (SEM) and focused ion beam (FIB) systems, the corrosion mechanism of binary Mg-Y alloys will be discussed based on the distribution of local cathodes and anodes on the alloy surface. Figure 1

Synthesis and Study of Nanocrystalline Mg<sub>2</sub>SiO<sub>4</sub> Powder and Yttrium Aluminum Garnet

The work investigates the characteristics of the porosity of inorganic salts: magnesium silicate and yttrium aluminum garnet (YAG). Using the example of nanocrystalline powders of magnesium silicate and yttrium aluminum garnet, the effect of synthesis parameters on the phase composition and porous characteristics of the obtained powders was studied. The average pore size of adsorbents was obtained: magnesium silicate - 48 nm; YAG, obtained by the standard Pechini method – 44 nm; YAG, obtained by the modified Pechini method – 37 nm; the industrial brand “magnesol” – 32 nm. The resulting materials can be attributed to mesoporous adsorbents.

Achieving exceedingly constructional characterization of magnesia-yttria (MgO-Y2O3) nanocomposite obtained via oxalate precursor strategy

Magnesium yttrium oxide (MgO-Y2O3) nanocomposites have been purposefully tailored using an oxalate precursor pathway. Commonly, MgO-Y2O3 nanocomposites possessed a significant technological challenge in electroceramics; particularly remarkable as the anode material for solid oxide fuel cells (SOFC). In this regard, different weight ratios, % of MgO and Y2O3 including (20:80), (50:50) and (80:20) were fabricated based on oxalic acid as a fuel in acidic medium. Indeed, the impact of the annealing temperature on the phase composition, crystallite size, morphology and optical properties was investigated using X-ray diffraction, field emission electron microscope (FESEM), TEM, FTIR and UV–VIS-NIR spectrophotometer. The FESEM results showed the nanocomposite had a cubic like structure with the fine grain sizes of 0–150 nm because of the rapid solidification. The band gap energy was found to be 4.83, 5.10 and 5.08 eV with increasing the ratio of Mg2+ ion from 20 to 50 and 80, respectively. Eventually, our currently studies consider to be an important achievement to investigate and recognize the features of the MgO-Y2O3 system for different applications involving microwave systems, advanced displays (field emission display, plasma display, electroluminescent display), ultra-fast sensors, durable, infrared windows and lasers.

Degradation and interaction with bone of magnesium alloy WE43 implants: A long-term follow-up in vivo rat tibia study.

The aim of this in vivo study was to examine the degradation and biocompatibility of the WE43 magnesium alloy containing magnesium yttrium, rare earth elements, and zirconium over a one-year long-term follow-up period. Additionally, we compared anodized WE43 implants with monolithic ones and clarified the effect of the anodization. WE43 cylindrical implants with and without anodization (length, 10 mm; diameter, 0.3 mm) were transplanted into the rat tibia. In both groups, the development of corrosion and the change in implant volume were evaluated by in vivo micro-computed tomography until 12 months, and the bone tissue reaction was observed histologically. In the monolithic WE43 implants, hydrogen gas was evident until 14 days and the volume loss was 36.3% after 12 months. In the anodized WE43 implants, the development of hydrogen gas was inhibited and the volume loss was 27.7% after 12 months. The anodized WE43 implants showed a significantly slower corrosion process in the early phase. Therefore, these implants may require a prolonged period to degrade completely and may even resist complete degradation. At one year post surgery, bone maturation progressed and lamellar bone structure developed around the implant in both groups. In conclusion, the WE43 implants showed good long-term stability and biocompatibility in bone tissue.

Switching properties of switchable mirrors using palladium-ruthenium catalytic layers

In preparing switchable mirrors, palladium (Pd) was used as a catalyst for hydrogenation and dehydrogenation, and to prevent oxidation of the switchable layer. To reduce the cost, Pd was alloyed with ruthenium (Ru) and used as a catalytic layer, since the price of Ru is approximately one-tenth that of Pd. Switchable mirrors of magnesium-yttrium (Mg-Y) alloy thin films coated with a Pd-Ru layer were prepared by direct-current magnetron sputtering method. Their optical switching properties between reflective and transparent states were studied using gasochromic method. The mirrors coated with Pd1-αRuα of up to α ≈ 0.6 showed nearly the same switching time from reflective to transparent state as those coated with pure Pd, while the mirrors coated with Pd1-αRuα of 0.2 ≤ α ≤ 0.4 showed shorter switching times from transparent to reflective state than those coated with pure Pd. Furthermore, the alloy-coated mirrors with shorter switching times had approximately 2–3 times higher switching durability than those coated with pure Pd. These shorter time and higher durability may be because Pd-Ru alloy prevents oxidation of the underlying layers more effectively than pure Pd. Thus, Pd-Ru alloy is one of the most promising catalysts for switchable mirrors.

Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented \u03b2-Y2Si2O7 Layer and Epitaxial ZrO2

The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3 is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7 (YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2 (Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2 and ε-YS is proven and multiple twinning relationships occur in the YS phases.

Improved performance of Mg–Y alloy thin film switchable mirrors after coating with a superhydrophobic surface

The magnesium based switchable mirrors can reversibly change their optical properties between the transparent and the reflective state as a result of hydrogenation and dehydrogenation. These films can potentially be applied as new energy-saving windows, by controlling the transmittance of solar radiation through the regulation of their reflective state. In this study, magnesium–yttrium (Mg–Y) alloy thin films were prepared using a DC magnetron sputtering method. However, the luminous transmittance in the transparent state and the switching durability of switchable mirrors are too poor to satisfy practical demands. In order to improve the films switching durability, luminous transmittance and the surface functionalization, polytetrafluoroethylene (PTFE) was coated with thermal vacuum deposition for use as the top layer of Mg–Y/Pd switchable mirrors. The PTFE layer had a porous network structure and exhibited a superhydrophobic surface with a water contact angle of approximately 152°. By characterization, PTFE thin films shows the excellent protection role against the oxidization of Mg, the switching durability of the films were improved 3 times, and also shows the antireflection role the luminous transmission of films was enhanced by 7% through the top covered with PTFE.

Emission analysis of RE3+ (RE=Eu, Sm, Dy):MgY4Si3O13 phosphors

A series of Eu3+, Sm3+, and Dy3+ ion doped magnesium yttrium silicate [MgY4Si3O13] phosphors was synthesized using the solid-state reaction method with a grain size of approximately 500nm in hexagonal symmetry. The photoluminescence (PL) spectra of the Eu3+, Sm3+, and Dy3+:MgY4Si3O13 phosphors exhibit bright red, orange-red and yellow emissions at 615nm (5D0→7F2), 603nm (4G52→6H7/2), and 574nm (4F9/2→6H13/2), respectively. The thermoluminescence (TL) of the phosphors displays the maximum intensity consistently at 10mol% of the ion concentrations, with a single glow peak around 165°C (Eu3+-activated phosphor), 230°C (Sm3+-activated phosphor), and 230°C (Dy3+-activated phosphor), respectively. The trap parameters such as the order of kinetics (b), activation energy (E), frequency factor (S), and Balarin parameter (γ) associated with the most intensive glow peak of these phosphors were finally determined by analyzing their line-shapes on the basis of Chen's method.

Evaluation of Critical Resolved Shear Stresses for Various Plastic Deformation Mechanisms To Understand Mechanical Properties of Magnesium-Yttrium Alloys

ABSTRACTIn order to understand enhanced mechanical properties of magnesium-yttrium (Mg-Y) alloys, applied stresses which were required to operate independent plastic deformation mechanisms on various stress axes were evaluated. Moreover, for this analysis, mechanical tests including newly-established testing method “pure-shear test” were conducted to evaluate Critical Resolved Shear Stresses (CRSSes) for various plastic deformation mechanisms of Mg-Y solid solution alloy single crystals with various Y concentration. Relatively higher solid solution strengthening of dominant plastic deformation mechanisms such as basal slip and extension twin at room temperature, results in increase in the activation of non-basal slip system. By a simple analysis based on von-Mises criterion with experimental CRSS values, it is revealed that enhanced mechanical properties of Mg-Y alloys might be attributed to the decrease of difference in the activity of plastic deformation mechanisms by Y addition.

Influence on optical properties and switching durability by introducing Ta intermediate layer in Mg–Y switchable mirrors

Magnesium–yttrium alloy switchable mirrors capped with a Pd layer with a thickness of 7.5nm have been shown to have a high switching durability of over 10,000 cycles between reflective and transparent states. However, the durability decreased considerably when the Pd thickness was decreased to improve the transmittance in the transparent state. Switchable mirrors with a thin Ta intermediate layer inserted between Mg–Y alloy layer and thinner Pd layers were then prepared by a direct-current magnetron sputtering method, and the optical switching durability was studied. Such a mirror capped by a Pd layer with a thickness of 3nm had a high switching durability of over 10,000 cycles, although a mirror without the Ta intermediate layer capped by a Pd layer with the same thickness never changed from the reflective to the transparent state. Owing to the decrease of the Pd thickness from 7.5 to 3nm, the visible transmittance in the transparent state increased, respectively, from 32% to 44% with high switching durability. The results of X-ray photoemission spectroscopy and transmission electron microscopy showed that the inserted Ta layer fully inhibits alloying between the Pd and Mg–Y layers, and that the Pd existed at the surface region and scarcely diffused into the Ta and Mg–Y layers even after switching of 10,000 cycles. Because alloying is one of the main reasons for the reduction in durability with decreasing Pd thickness, the prevention of alloying is expected to cause high switching durability.

SURFACE MORPHOLOGY OF MGF2/YF3 MULTI LAYER THIN FILMS BY THERMAL EVAPORATION METHOD

Magnesium fluoride and Yttrium fluoride antireflec tion multilayer thin films have been deposited on t o well cleaned BK-7 Glass substrate in Vacuum of 2x10 -5 mbar using physical vapour deposition technique. S urface morphology analysis by AFM of different multilayer structures deposited by thermal evaporat ion method i.e., Single layer, double layer, three layer and four layer thin films were presented in this study. The main object ive of this study was to investigate the influence of thickness of various antireflection multilayer thin films on the effect of surface roughness and grain size of the particle s. The thickness of the films has been determined by quartz crystal monitor method. T he surface morphology studies are performed using A tomic force Microscopy (AFM) techniques. AFM was the best tool to investig ate the surface smoothness and to find the grain si ze of the particles. The grain size is calculated for all the films of different thickness. Index Terms: Multilayer’s, AFM, MgF 2/YF 3, Roughness, Grain size, BK-7, Antireflection

Pd distribution of switchable mirrors based on Mg–Y alloy thin films

Pd-capped magnesium–yttrium alloy switchable mirrors were found to have high switching durability of over 10,000 cycles between reflective and transparent states. However, the durability decreased with the decreasing Pd thickness. Switchable mirrors with various Pd thicknesses were then prepared by a direct-current magnetron sputtering method, and the degradation in durability was studied by observing the distribution of each element of the switchable mirrors from the film surface to the substrate. X-ray photoemission spectroscopy and transmission electron microscopy showed that Pd with a short sputtering time (corresponding to layer thickness of 3nm) resulted in surface oxidation of Mg and Y, and no Pd was present at the surface. The deposited Pd was alloyed with the Mg–Y layer and after taking the sample out from the vacuum chamber a Pd-rich layer appeared between the surface oxides and the Mg–Y layers. With increasing deposition time, a Pd layer was formed on the oxide layer and the Pd layer thickness increased. The mirror with switching durability of over 10,000 cycles had a sufficiently thick Pd top layer of ~7nm and a very thin oxide layer. This thick Pd layer is believed to be the reason for the high switching durability.

Film thickness change of switchable mirrors using Mg3Y alloy thin films due to hydrogenation and dehydrogenation

Switchable mirrors based on magnesium–yttrium alloy thin films were prepared by a direct-current magnetron sputtering method. The changes in the film thickness of the mirrors due to hydrogenation and dehydrogenation have been investigated using atomic force microscopy and X-ray reflectometry. As a result of first hydrogenation of a switchable mirror, the thickness was expanded by ~15%, while as a result of dehydrogenation, the thickness was compressed by only ~2%. From the switching processes, the thickness changed by ~2% on the following optical switching. This small change may cause high switching durability of Mg–Y switchable mirrors.

Optical switching durability of switchable mirrors based on magnesium–yttrium alloy thin films

Switchable mirrors based on magnesium–yttrium alloy thin films were prepared using a direct-current magnetron sputtering method. The optical switching durability between reflective and transparent states using a gasochromic method has been investigated. Pd-capped Mg1−zYz (0.14<z<0.81) films showed excellent switchable mirror properties. The switching durability increased with Y composition, z, and reached over 10,000 cycles at z>0.5. The mirrors with the Y composition in the wide range of 0.27–0.70 have visible transmittance values of about 35% in the transparent state. The difference in visible transmittance between the reflective and transparent states decreased with z, especially over 0.7. In the transparent state, all prepared switchable mirrors had relatively flat optical transmittance spectra in the visible range and showed nearly neutral color appearance. Thus, the optimal Y composition is in the range of 0.5–0.7 for switchable mirrors with high switching durability and large dynamic range between the reflective and transparent states.

Ab initio and atomistic study of generalized stacking fault energies in Mg and Mg–Y alloys

Magnesium–yttrium alloys show significantly improved room temperature ductility when compared with pure Mg. We study this interesting phenomenon theoretically at the atomic scale employing quantum-mechanical (so-called ab initio) and atomistic modeling methods. Specifically, we have calculated generalized stacking fault energies for five slip systems in both elemental magnesium (Mg) and Mg–Y alloys using (i) density functional theory and (ii) a set of embedded-atom-method (EAM) potentials. These calculations predict that the addition of yttrium results in a reduction in the unstable stacking fault energy of basal slip systems. Specifically in the case of an I2 stacking fault, the predicted reduction of the stacking fault energy due to Y atoms was verified by experimental measurements. We find a similar reduction for the stable stacking fault energy of the non-basal slip system. On the other hand, other energies along this particular γ-surface profile increase with the addition of Y. In parallel to our quantum-mechanical calculations, we have also developed a new EAM Mg–Y potential and thoroughly tested its performance. The comparison of quantum-mechanical and atomistic results indicates that the new potential is suitable for future large-scale atomistic simulations.

On the precipitates and mechanical properties of magnesium–yttrium sheets

Light-weight wrought magnesium alloys is an important part of the weight reduction in automobiles industry for improve their fuel efficiency. Yttrium containing magnesium alloy is a potential material in this perspective. In this work, two magnesium–yttrium alloys (C and D alloys) were cast and rolled to 2mm thick sheets. The mechanical properties of these hot rolled and annealed sheets were determined. Optical microscope and scanning electron microscope equipped with EDX were used to investigate microstructure evolution during thermo-mechanical processing in the studied alloys. Precipitates evolution during hot rolling and annealing processes were analyzed and compared with those calculated using thermo-chemical software (FactSage). Schiel phase distribution diagrams of C and D alloys were calculated using FactSage.

Corrosion studies of modified organosilane coated magnesium–yttrium alloy in different environments

Magnesium (Mg) and its alloys have numerous potential applications as biodegradable implants, but the fast degradation rate of Mg alloys at the initial implanted stage could be a problem. This paper describes the modification of the water-based bis-[triethoxysilyl] ethane (BTSE) silane applied to the surface of magnesium–yttrium (Mg–4Y) to increase its corrosion resistance. Surface characterization by SEM, FTIR, and EDX showed that the hydrolysis and condensation of the silane resulted in a covalent bonding to the Mg–4Y surface. Corrosion behavior of the uncoated and coated Mg–4Y alloy was evaluated in different environments by using a novel self-developed corrosion probe. Based on the electrochemical results of DC polarization and electrochemical impedance spectroscopy (EIS), we conclude that the epoxy-modified BTSE silane coating successfully increases the corrosion resistance at the initial stage of implantation. The corrosion rates in the flesh of dead mice environments such as body cavity and subcutaneous tissue of the mice were lower than the corrosion rates in in vitro environments.

Novel sol–gel derived calcium phosphate coatings on Mg4Y alloy

Calcium phosphates (CaPs) and silicon containing calcium phosphates (Si-CaPs) coatings on a biodegradable magnesium yttrium alloy (Mg4Y) were prepared by a sol–gel technique to improve the bioactivity of the alloy surface. The experimental results show that thick porous coatings comprised of nano-sized calcium phosphate particles can be prepared by heating the as dip coated substrates at 450 °C. The in vitro degradation results show that the coatings do not alter the degradation kinetics of the substrates significantly and the release of magnesium and yttrium ions at initial time points was very similar for both the coated and bare substrates. The cyto-compatibility studies using MC3T3-E1 osteoblasts show that the coated substrates were more bioactive than the uncoated substrates as the cells begin to grow and form a matrix on the coated substrates more easily than on the bare metal. These preliminary results collectively show the potential of use of sol–gel derived calcium phosphate coatings on magnesium based degradable scaffolds to improve their surface bioactivity.