Addition Of Gd Research Articles

Microstructure Changes in Sn- or Gd-Modified Cu–11%Al–10%Mn Alloy

The effects of the addition of Sn or Gd on the phase transitions of the Cu–11%Al–10%Mn alloy were studied to identify and characterize the phases formed at each transition observed in the differential scanning calorimetry curves. The characterization was carried out by X-ray diffraction, microhardness tests, and magnetization measurements as a function of the applied field. The microstructure was investigated by optical microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The results showed that the addition of Sn stabilizes the $$\beta $$ phases, and changes the phases present in the Cu–11%Al–10%Mn alloy, whereas the addition of Gd does not interfere with the phase transitions. In addition, Sn improves the alloy saturation magnetization, while addition of Gd deteriorates it.

Microstructural, Electrochemical and In Vitro Analysis of Mg-0.5Ca-xGd Biodegradable Alloys

The subject of Mg-based biodegradable materials, used for medical applications, has been extensively studied throughout the years. It is a known fact that alloying Mg with biocompatible and non-toxic elements improves the biodegradability of the alloys that are being used in the field of surgical applications. The aim of this research is to investigate the aspects concerning the microstructure, electrochemical response (corrosion resistance) and in vitro cytocompatibility of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with controlled addition of Gd as follows: 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%—in order to establish improved biocompatibility with the human hard and soft tissues at a stable biodegradable rate. For this purpose, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM) and X-ray diffraction (XRD) were used for determining the microstructure and chemical composition of the studied alloy and the linear polarization resistance (LPR) method was used to calculate the corrosion rate for the biodegradability rate assessment. The cellular response was evaluated using the 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test followed by fluorescence microscopy observation. The research led to the discovery of a dendritic α-Mg solid solution, as well as a lamellar Mg2Ca and a Mg5Gd intermetallic compound. The in vivo tests revealed 73–80% viability of the cells registered at 3 days and between 77 and 100% for 5 days, a fact that leads us to believe that the experimental studied alloys do not have a cytotoxic character and are suitable for medical applications.

Local atomic structures of Gd and Zn atoms in extruded Mg-Gd-Zn alloys

Minor addition of Gd and Zn can significantly improve the mechanical properties of extruded Mg-1 wt.%Gd-xZn (x = 0, 0.5, 1 wt.%) alloys. However, how they modify the structure of alloys remains elusive. By using x-ray absorption fine structure, we found that Zn atoms tend to bond with Gd and the 0.5 wt.% Zn addition greatly reduces the coordination number (CN) of Gd atoms, forming an enhanced double solid-solution strengthening. Whereas, 1 wt.% Zn not only increases the CNs of Zn and Gd but also promotes the formation of minor Mg3Zn3Gd2 phase. Compared with the grain refinement strengthening, it is found that the solid solution strengthening is not a dominant factor.

Collective dynamics in lipid membranes containing transmembrane peptides.

Biological membranes are composed of complex mixtures of lipids and proteins that influence each other's structure and function. The biological activities of many channel-forming peptides and proteins are known to depend on the material properties of the surrounding lipid bilayer. However, less is known about how membrane-spanning channels affect the lipid bilayer properties, and in particular, their collective fluctuation dynamics. Here we use neutron spin echo spectroscopy (NSE) to measure the collective bending and thickness fluctuation dynamics in dimyristoylphosphatidylcholine (di 14 : 0 PC, DMPC) lipid membranes containing two different antimicrobial peptides, alamethicin (Ala) and gramicidin (gD). Ala and gD are both well-studied antimicrobial peptides that form oligomeric membrane-spanning channels with different structures. At low concentrations, the peptides did not have a measurable effect on the average bilayer structure, yet significantly changed the collective membrane dynamics. Despite both peptides forming transmembrane channels, they had opposite effects on the relaxation time of the collective bending fluctuations and associated effective bending modulus, where gD addition stiffened the membrane while Ala addition softened the membrane. Meanwhile, the lowest gD concentrations enhanced the collective thickness fluctuation dynamics, while the higher gD concentrations and all studied Ala concentrations dampened these dynamics. The results highlight the synergy between lipids and proteins in determining the collective membrane dynamics and that not all peptides can be universally treated as rigid bodies when considering their effects on the lipid bilayer fluctuations.

Role of Gd addition on machinability of Al-15%Mg2Si in-situ composite during dry turning

Recently, Al-Mg2Si in-situ composites have achieved considerable attention due to their excellent physical and mechanical properties. In fact, there are some limitations of knowledge regarding the machinability characteristics of these composites - particularly when being inoculated with rare earth additions. This study in turn aimed to investigate the influence of machining parameters as well as Gd addition on the machinability of Al-15%Mg2Si composite. To examine the effect of modifier (1.0 wt. % Gd) and machining parameters (feed rate, cutting speed), microstructural evolution, surface roughness (Ra) and cutting force (Fc) were evaluated during dry turning. The results revealed that Gd addition as modifier element led to better surface roughness and higher cutting force owning to the modification of Mg2Si particle structure as well as the formation of Gd intermetallic compounds.

Restoration Mechanisms at Moderate Temperatures for As-Cast ZK40 Magnesium Alloys Modified with Individual Ca and Gd Additions

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 °C and 300 °C. Compression tests were carried out at 0.0001 s−1 and 0.001 s−1 using a modified Gleeble system during in-situ synchrotron radiation diffraction experiments. The deformation mechanisms are corroborated by post-mortem investigations using scanning electron microscopy combined with electron backscattered diffraction measurements. The restoration mechanisms in α-Mg are listed as follows: the formation of misorientation spread within α-Mg, the formation of low angle grain boundaries via dynamic recovery, twinning, as well as dynamic recrystallisation. The Gd and Ca additions increase the flow stress of the ZK40, which is more evident at 0.001 s−1 and 300 °C. Dynamic recovery is the predominant restoration mechanism in all alloys. Continuous dynamic recrystallisation only occurs in the ZK40 at 250 °C, competing with discontinuous dynamic recrystallisation. Discontinuous dynamic recrystallisation occurs for the ZK40 and ZK40-Gd. The Ca addition hinders discontinuous dynamic recrystallisation for the investigated temperatures and up to the local achieved strain. Gd addition forms a semi-continuous network of intermetallic compounds along the grain boundaries that withstand the load until their fragmentation, retarding discontinuous dynamic recrystallisation.

Enhancing the stabilization of nanostructured rocksalt-like high entropy oxide by Gd addition

In this work, nanostructured single phase high entropy oxide was easily synthesized by a fast polymeric solution method. Despite the higher ionic radius, coordination and oxidation state, gadolinium was homogeneously distributed in crystallites. Their effect on the lattice was studied by Raman spectroscopy, transmission electron microscopy and X-ray diffraction. The configurational entropy increased with the addition of Gd3+, but the expansion in the lattice is mostly associated to the diffusion of copper to the crystal. However, gadolinium enhances the asymmetry on longitudinal-optic (A1g) Raman mode and also prevents the excessive growth of crystallites.

Crystallization behavior, soft magnetic properties and good bending ductility of high Fe content FeSiBCuPC alloys induced by composition design

Effects of the minor addition of similar ferromagnetic elements (Fe, Co, Ni, and Gd), metal element with strong non-metallic properties (Al), and transition metal elements with large atomic radius (V, Hf, Ti, and Cr) on crystallization behavior, magnetic properties and bending ductility of Fe85Si0·5B9P4Cu0·5C0.1M0.9 alloys were systematically investigated. The addition of Al, Ni, and Co improves the thermal stability and inhibits the growth of the α-Fe grains. Besides, Gd addition causes a large temperature interval, which suppresses the precipitation of secondary phase. Through the optimum heat treatments, the nanocrystalline alloys exhibit excellent soft magnetic properties, such as higher Ms of 191.7–208.7 emu/g and lower Hc of 6.7–12.1 A/m. Due to the nature of brittleness, the shear morphology induced by elemental microalloying is critical for understanding microscopic mechanism of plastic deformation and achieving high toughness amorphous alloys. We demonstrate that the formation of shear bands are related to the degree of amorphization, shear transformation zones and Poisson’s ratio.

Hot deformation constitutive analysis and processing maps of extruded Mg–Gd binary alloys

Hot shear deformation behavior and optimum processing parameters of the binary Mg–xGd (x = 0.5, 1, and 2 wt%) alloys were studied through the development of constitutive equations and processing maps. Shear punch tests (SPT) were performed in the temperature range of 573–723 K and shear strain rate range of 1.7 × 10−2–1.3 × 10−1 s−1. It was observed that increasing the Gd content retarded the dynamic recrystallization (DRX), leading to smaller DRXed grain size, higher amounts of unDRXed elongated patches, as well as higher shear strength. Based on the stress exponent and deformation activation energy values, calculated through constitutive analysis, the dominant controlling mechanisms were suggested as climb-controlled deformation for the Mg–0.5Gd alloy, and dislocation viscous glide for the Mg–1Gd and Mg–2Gd alloys. The processing maps were plotted to obtain the optimum processing conditions for all tested materials. The results show that the temperature of the safe region with maximum efficiency increased by increasing the amount of Gd addition.

Microstructure and Gd-rich phase evolution of as-cast AZ31-xGd magnesium alloys during semi-solid isothermal heat treatment

The microstructure and Gd-rich phase evolution of as-cast AZ31-xGd (x=0, 1.5 wt.%, 2.0 wt.% and 2.5 wt.%) magnesium alloys during semi-solid isothermal heat treatment were investigated deeply in the present work. Results showed that the lamellar (Mg,Al)3Gd phases transformed into the particle-like Al2Gd phases in AZ31 magnesium alloys with Gd addition during semi-solid isothermal heat treatment, leading to yielding more spherical α-Mg grains. When Gd content is 2.0 wt. %, the size of semi-solid spherical grains reaches the minimum. The main mechanism of grain refinement lies in the remelting of dendritic branches as well as the auxiliary effect of a small number of Al2Gd particles as grain refining inoculants. Meanwhile, Al2Gd particles enriched at the solid-liquid interfaces can remarkably retard the growth rate of α-Mg grains. A reduction of deformation resistance has been successfully achieved in AZ31-2.0Gd magnesium alloy after semi-solid isothermal heat treatment, which shows a moderate compressive deformation resistance (230 MPa), comparing to the as-cast AZ31 magnesium alloy (280 MPa) and semi-solid AZ31 magnesium alloy (209 MPa).

Effects of ECAP Extrusion on the Microstructure, Mechanical Properties and Biodegradability of Mg–2Zn–xGd–0.5Zr Alloys

Effects of equal channel angular pressing (ECAP) extrusion on the microstructure, mechanical properties and biodegradability of Mg–2Zn–xGd–0.5Zr (x = 0, 0.5, 1, 2 wt%) alloys were studied in this work. Microstructure analysis, tensile test at ambient temperature, immersion test and electrochemical test in Hank’s solution were carried out. The results showed that Gd could further enhance the grain refinement during the ECAP extrusion. Both Gd addition and ECAP extrusion could improve the mechanical properties of the alloys, and the extrusion played the dominant role. Minor addition of Gd (0.5–1 wt%) could obviously enhance the corrosion resistance of the alloys. To some extent, ECAP extrusion improved the corrosion resistance of the alloys due to the change of second phases distribution and the refinement of grains. Further increase in extrusion pass was detrimental to the improvement of the corrosion resistance as a result of increment of the grain boundaries.

Effect of Gd addition on the microstructure and age hardening behavior of Mg-6Zn-1Mn-4Sn (wt.%) alloy

The microstructure evolution and age hardening behavior of Mg-6Zn-1Mn-4Sn (wt.%, ZMT614) through various Gd addition were investigated. The as-cast ZMT614 alloy was mainly composed of Mg2Sn, Mg7Zn3 and α-Mg solid solution, and new MgSnGd phases were detected with Gd addition. The MgSnGd phase nucleated prior to Mg2Sn during solidification, resulting in consumption of Sn element and reduction of Mg2Sn phase. Owing to the pinning effect of MgSnGd phase, some dislocations were preserved during solution treatment. The retained dislocations could act as heterogeneous nucleation sites for the rod-like β1´ precipitates. A trace of Gd addition could enhance the peak hardness and shorten the peak aging time, while excessive Gd addition would weaken the age hardening response. The ZMT614-0.2Gd alloy exhibited the optimum mechanical properties with yield strength of 373 ± 4 MPa and ultimate tensile strength of 405 ± 6 MPa.

Chemical Solution Deposition of YBCO Films with Gd Excess

Chemical solution deposition of Gd-doped YBCO, Y1GdyBa2Cu3O7−δ, (YBCO-Gd), film was carried out following the metal-organic decomposition approach and in situ route. Two dopant concentrations, 5 and 10 mol %, were evaluated. The morphology and crystalline structure of the superconductor films were deeply investigated. In general, a homogeneous and well c-axis oriented film was observed by using scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction. However, compared to pure YBCO, YBCO-Gd samples showed an increased stacking faults concentration, as recognized by TEM. X-ray photoelectron spectroscopy allowed studying the Gd distribution in the films and gathered information about the Gd electronic environment. Superconducting properties were evaluated at different temperatures, magnetic field directions, and intensities. Higher zero-field critical current densities were measured with respect to undoped samples in the temperature range from 10 to 77 K with both Gd concentrations (i.e., 28, 27, and 13 MA·cm−2, respectively, for YBCO-Gd 5%, YBCO-Gd 10%, and undoped YBCO at 10 K in self field condition). At low temperatures, this improvement was maintained up to 12 T, confirming the efficacy of Gd addition for the enhancement of transport properties of YBCO film.

Improving the corrosion resistance of MgZn1.2GdxZr0.18 (x = 0, 0.8, 1.4, 2.0) alloys via Gd additions

Effects of Gd addition on microstructure, corrosion behavior and mechanism of cast and extruded MgZn1.2GdxZr0.18 alloys are investigated through microstructure observation, weight loss and electrochemical tests. Increasing Gd from 0 to 2.0 at.%, grains are refined, MgZn2 phase, W-phase and X-phase are formed successively, and basal texture intensity is decreased. The significantly decreased grain size by extrusion and Gd addition induces formation of protective Gd2O3 and MgO layer. The extruded MgZn1.2Gd2.0Zr0.18 alloy shows decreased corrosion rate of 3.72 ± 0.36 mm/year, owing to fine and homogeneous microstructure, dual-role (micro-anode and barrier) of X-phase, compact oxidation layer and basal crystallographic texture.

Corrosion behavior characterization of as extruded Mg-8Li-3Al alloy with minor alloying elements (Gd, Sn and Cu) by scanning Kelvin probe force microscopy

The effects of Gd, Sn and Cu on the corrosion behavior of as extruded Mg–8Li–3Al (LA83) alloy were characterized by scanning Kelvin probe force microscopy, weight loss, hydrogen evolution, and electrochemical measurements. Result revealed that many Al2Gd, Mg2Sn, and AlCuMg particles were discovered in modified alloys, respectively. The combined experimental results of weight loss, hydrogen evolution, and electrochemical analysis indicated that the addition of Gd and Sn improve the corrosion resistance of as extruded LA83 alloy while the addition of Cu weaken its corrosion resistance. The corrosion mechanisms of different elements in as extruded samples were discussed.

Influence of Superheating Melt Treatment on Microstructure of Gd-Modified Al-15wt.% Mg2Si In-Situ Composite

The influence of melt superheating treatment with different superheating temperatures (750, 800, 850, and 900°C) on the microstructure of Al-15wt. % Mg2Si composites before and after addition of Gd (1.0 wt.%) were studied. Microstructure characterisation was carried out via optical microscopy (OM) and x-ray diffraction (XRD).The results showed that in the unmodified composite, when the temperature of superheating raised from 750°C to 900°C, the primary Mg2Si experienced a decrease of the average grain size from 40 to about 32 µm, while, in the Gd-modified composite, the particle size was refined considerably from 27 to 13 µm by increasing the temperature from 750°C to 850°C. Furthermore, with a further increase in temperature to 900°C, the particle size slightly increased to about 15 µm which might be due to the burning loss of Gd in the melt. Nevertheless, for both unmodified and Gd-modified composites, the superheating temperature exhibited minor influence on the Mg2Si crystals morphologies. It is believed that compiling of Gd addition and superheating melt treatment is efficient to improve the composite properties that could encounter the application requirements.

Achieving fine-grained Ti-V-Al light weight shape memory alloys with higher transformation temperature, superior performances by doping Gd

Effect of Gd addition on microstructure, martensitic transformation and strain recovery characteristics was investigated. Gd addition resulted in the significant reduction of grain size and formation of Gd-rich phase. The Gd-rich phase was identified as Gd3(Ti,V) phase with an orthorhombic structure. The solution treated (Ti-13V-3Al)100−xGdx alloys underwent a α″ → β transformation during heating, irrespective of Gd content. But Gd addition led to a slight drop of martensitic transformation temperatures. In addition, the moderate Gd addition can promote the achievement of outstanding mechanical and functional properties due to the combination of the grain refinement and precipitation strengthening of Gd-rich phase in grain interior. Ti-V-Al alloy with an optimal Gd content, which was Ti-V-Al alloy containing 0.3 at.% Gd, showed the largest recoverable strain of 4.9% at a pre-strain of 6% and the ultimate tensile stress of 925 MPa. Meanwhile, Ti-V-Al alloy had a superior elongation of 20.7%, as 0.3 at.% Gd was added.

Inactivation effect and mechanisms of combined ultraviolet and metal-doped nano-TiO2 on treating Escherichia coli and Enterococci in ballast water.

The discharge of ship ballast water (containing large amounts of alien organisms) has caused severe ecological hazards to marine environments. In this study, three metal elements (Ag, Fe, and Gd) were doped to nano-TiO2 material respectively (content: 0.4%, 0.7%, and 1.0%) to improve inactivation effect of Escherichia coli and Enterococci in ballast water. Experimental results indicate that compared with the sole ultraviolet (UV) and the UV and original nano-TiO2, the UV and metal-doped nano-TiO2 increased the bacterial inactivation rate to different extents. For each metal element, high external metal content (1.0%) corresponded to high inactivation effort. The doping of Ag resulted in optimal inactivation effort, and the addition of Fe and Gd caused unobvious effort. At the end of the inactivation process (20 s), the UV and 1% Ag-doped nano-TiO2 reached the highest logarithmic sterilization rates (0.915 for Escherichia coli and 0.805 for Enterococcus). The doping of Ag, Fe, and Gd did not change the anatase phase TiO2 crystal form, and 1% Ag-doped nano-TiO2 had the smallest particle diameter and the evenest distribution of nanoparticles. Compared with the sole UV, the UV and Ag-doped nano-TiO2 treatment resulted in higher malondialdehyde contents (0.0646 μmol/L for Escherichia coli and 0.0529 μmol/L for Enterococci) and lower superoxide dismutase activities (0.672 U/mL for Escherichia coli and 0.792 U/mL for Enterococci), which were in accordance with high inactivation rates in these cases.

Prediction of on-treatment disability worsening in RRMS with the MAGNIMS score

Background: The magnetic resonance imaging in multiple sclerosis (MAGNIMS) score combines relapses and magnetic resonance imaging (MRI) lesions to predict disability outcomes in relapsing–remitting multiple sclerosis (RRMS) treated with interferon-β. Objective: To validate the MAGNIMS score and extend to other disease-modifying therapies (DMTs). To examine the prognostic value of gadolinium contrast-enhancing (Gd+) lesions. Methods: This RRMS MSBase cohort study (n = 2293) used a Cox model to examine the prognostic value of relapses, MRI activity and the MAGNIMS score for disability worsening during treatment with interferon-β and three other DMTs. Results: Three new T2 lesions (hazard ratio (HR) = 1.60, p = 0.028) or two relapses (HR = 2.24, p = 0.002) on interferon-β (for 12 months) were predictive of disability worsening over 4 years. MAGNIMS score = 2 (1 relapse and ⩾3 T2 lesions or ⩾2 relapses) was associated with a greater risk of disability worsening on interferon-β (HR = 2.0, p = 0.001). In pooled cohort of four DMTs, similar associations were seen (MAGNIMS score = 2: HR = 1.72, p = 0.001). Secondary analyses demonstrated that the addition of Gd+ to the MAGNIMS did not materially improve its prediction of disability worsening. Conclusion: We have validated the MAGNIMS score in RRMS and extended its application to three other DMTs: 1 relapse and ⩾3 T2 lesions or ⩾2 relapses predicted worsening of disability. Contrast-enhancing lesions did not substantially improve the prognostic score.

Microstructure evolution and mechanical property of Mg-3Al alloys with addition of Ca and Gd during rolling and annealing process

Abstract The formability of magnesium alloys at ambient temperature can be enhanced by alloying additions such as Ca and RE elements, which is ascribed to the weakened basal texture. To produce magnesium alloy sheets with excellent comprehensive performance, the evolution of texture characterization during fabrication process and subsequent effect of texture on mechanical properties are vital controlling factors. In this investigation, three experimental Mg-3Al series alloys were hot rolled and annealed to sheets with 1 mm thickness. The microstructure evolution during rolling and annealing process was investigated. Furthermore, the influence of texture on tensile properties along different tensile directions was also studied. The results show that weakened basal texture and refined grains were achieved with the co-addition of Ca and RE element. However, strengthening of mechanical properties wasn't obtained. During hot rolling process, microstructure was refined, second phase particles broken, and basal texture was increased. While basal texture was weakened during annealing process. Recrystallization behavior influenced by formation of second phase was dominated to attenuate basal texture. Tensile deformation behavior was controlled by basal slip and followed Schmid factor criterion. Moreover, the weakened basal texture and activation of non-basal slips during hot rolling process can contribute to diminish the anisotropy of tensile properties.