Effects Of Transition Metal Elements Research Articles

Electron tailoring of thermal and magnetocaloric properties in Tb55TM17.5Al27.5 (TM = Fe, Co, and Ni) metallic glasses

Transition metal (TM) elements play a key role in determining properties of magnetocaloric materials. However, the effect of TM elements on the thermodynamic behavior and magnetocaloric effect (MCE) of metallic glasses (MGs) remains elusive. In this work, ternary Tb55TM17.5Al27.5 (TM = Fe, Co, and Ni) MGs without the complexities induced by high-entropy effects were designed. It is found that both the glass transition temperature (Tg) and the initial crystallization temperature (Tx) significantly increase with decreasing 3d electron number. It leads to the low values of Trg, γ, and γm for Tb55Fe17.5Al27.5, which is consistent with its poor glass forming ability (GFA) as evidenced by the obvious lattice fringes and structural order. Despite the mediocre value of magnetic entropy change (|ΔSMpk|) for Tb55Fe17.5Al27.5, its broader magnetic transition temperature of 110.4 K associated with ∼26% evident structural order yields the maximum relative cooling power (RCP) of 546.04 J kg−1 among three MGs. Moreover, a novel weighted method for evaluating 3d electron number by consideration of the concentration and species of TM elements was adopted to reveal an inverse correlation between the 3d electron number and Tg/Tx, as well as curie temperature (Tc), |ΔSMpk|, and RCP. It is found that with the decrease of the weighted 3d electron number of TM elements, the thermal stability of rare-earth-base MGs is effectively enhanced ascribed to the strong f - d orbital hybridization effect, along with the enhanced 3d - 3d exchange interaction that induces a high Tc. This work would help us more deeply understand the role of TM elements from the perspective of electronic structure, which is crucial for designing the novel MGs with a tunable MCE and GFA applied in various cryogenic refrigeration fields.

Effects of Transition Metal Elements on Ni Migration in Solid Oxide Cell Fuel Electrodes

Solid oxide cells (SOCs), both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC), have emerged and attracted more and more attentions due to its high energy conversion efficiency and fuel flexibility. However, degradation of fuel electrodes after long-term operation remains as one of the main challenges for their commercial application. Two major types of microstructure evolution, nickel (Ni) migration and Ni coarsening in Ni - yttria-stabilized zirconia (Ni-YSZ) fuel electrodes have been widely reported, which have strong impacts on both cell performance and durability. Therefore, materials-driven research has focused on developing more robust fuel electrodes with good electrocatalytic ability. Utilization of Ni alloys has immersed as a promising concept to enhance the performance and robustness of conventional Ni/YSZ. In the present study, Ni-M (M = Fe, Cu) bimetallic fuel electrodes are applied to investigate the effects of transition metal elements on the morphological evolutions under SOFC and SOEC operations. Ni-Fe, Ni-Cu and pure Ni patterned fuel electrodes are sputtered on YSZ pellets. The electrochemical performance of these Ni-M bimetallic fuel electrodes decreases compared with pure Ni fuel electrode, while the performance degradation rate of Ni-Fe fuel electrodes is smaller than others. Besides, the spreading of Ni film on YSZ surface is observed for all samples under anodic polarization and such Ni migration is suppressed by Fe doping, whereas enhanced by Cu doping. On the other hand, the adhesion is weakened at the electrode / electrolyte interface for Ni-Cu and pure Ni fuel electrodes under cathodic polarization, while good adhesion at the interface is maintained for Ni-Fe, which correlates with the smaller performance degradation rate.

Effects of transition metal elements and O on grain boundary energy and strength of Co by first-principles study

Considering the (210)[001] grain boundary of Co as a model, the influence of transition metals and their coupling with O on the grain boundary energy and strength was investigated by a first-principles-based study. Quantitative characterization was used to explain the transition metal segregation at the grain boundary, and the negative correlation between grain boundary energy and atomic radius was revealed. It has been found that the interaction between the solute and the host atoms at the grain boundary affects the grain boundary strength. Re, W, Os, Cr, Tc, Mo, Ir, Ta, Zr, Ru, Nb, V, Rh, Pt, Pd, and Ni can significantly strengthen the grain boundary, while other transition metals have a weakening effect on the grain boundary. In particular, Cr, Hf, Ta, W, Re, Os, Ir, and Pt can effectively alleviate the weakening of the grain boundary caused by O atoms.

Effects of Transition Metal Elements on Ni Migration in Solid Oxide Cell Fuel Electrodes

In the present study, Ni-M (M = Fe, Cu) bimetallic fuel electrodes are applied to investigate the effects of transition metal elements on nickel (Ni) migration and Ni coarsening under SOFC and SOEC operations. Ni-Fe, Ni-Cu and pure Ni patterned fuel electrodes are sputtered on YSZ pellets. The electrochemical performance of these Ni-M bimetallic fuel electrodes are lower than pure Ni fuel electrode, while the degradation rate of Ni-Fe fuel electrodes is smaller than the others. The spreading of Ni film on YSZ surface is observed for all samples under anodic polarization, and such Ni migration is suppressed by Fe doping, whereas it was enhanced by Cu doping. The adhesion between the electrode/electrolyte interface is weakened for Ni-Cu and pure Ni fuel electrodes under cathodic polarization, while good adhesion at the interface is maintained for Ni-Fe, which correlates with the smaller performance degradation rate.

Effects of Ti, Zr, Ta, and W on elastic properties, stacking fault energy, and ductility of HfC

First principles calculation is carried out to systematically investigate the effects of transition metal elements (Ti, Zr, Ta, W) on elastic properties, hardness, surface energy, stacking fault energy, and ductility of HfC. It is found that the addition of Ti and Zr would decrease the elastic properties and hardness of HfC, while Ta and W could increase. Calculations also reveal that Ti, Zr, and W decrease both surface energy and stacking fault energy of HfC, and such a decrease is mainly attributed to smaller bond energies of Ti-C, Zr-C, and W-C bonds than that of Hf-C. The addition of Ta increases the surface energy of HfC due to a stronger Ta-C bond, and decreases the stacking fault energy of HfC as a result of a more reduction of bond energy of the Ta-C bond than that of the Hf-C bond. In addition, Ta and W have an important effect to considerably increase the ductility of HfC, while such effects of Ti and Zr are much smaller.

Improvement in photo-device properties of CuO thin films for opto-electronic applications: effects of (Ni, Co) co-doping

We report co-doping effects of transition metal elements (Ni, Co) primarily on the opto-electronic properties of CuO thin films. CuO, CuO:Ni(1%), CuO:Co(1%) and CuO:Ni(1%):Co(1%) thin films were deposited via the spray pyrolysis route. Structural studies revealed the monoclinic CuO structure for all films. For all the films scanning electron microscope (SEM) images showed a crack-free and homogeneous surface. Photoluminescence (PL) spectra of all the films exhibited four emission peaks at 415, 451, 477, and 521 nm wavelengths. The optical bandgap (E g) values were around 2.12 eV, 2.18 eV, 2.05 eV and 1.84 eV for CuO, CuO:Ni(1%), CuO:Co(1%) and CuO:Ni(1%):Co(1%)thin films, respectively. CuO:Ni(1%):Co(1%) photo-device displayed a large responsivity (R) of 0.43 AW−1, external quantum efficiency (EQE) of 100% and detectivity (D *) of 9.55 × 109 Jones. Hence, co-doping of transition metal elements would be one of the effective approaches for enhancing opto-electronic properties of metal oxide compounds.

Effects of Fe on L12 phase precipitation and mechanical properties in Al0.3CrFeCoNi high-entropy alloy

The newly developed L12-strengthened high-entropy alloy shows great potential to possess superior combinations of physical and mechanical properties. It has been extensively studied how to control the L12 phase by adjusting L12-phase forming elements such as Al, Ti, Ta and Nb. However, the effect of transition-metal elements on L12 precipitation is still unclear. This work investigated the effect of Fe on the stability and distribution of the L12 phase by reducing the level of Fe in a well-studied high-entropy alloy Al0.3CrFeCoNi. A close examination of the precipitation behaviour in the Al0.3CrFeCoNi and Al0.3CrFe0.6CoNi1.4 alloys was conducted using transmission electron microscopes. When the aging temperature reaches 700 °C in the Al0.3CrFeCoNi alloy, nanosized L12 particles would transition to the B2 phase. By reducing the amount of Fe, the stability and density of the L12 phase were both enhanced. After 700 °C annealing, L12 nanoparticles are still stable in the Al0.3CrFe0.6CoNi1.4 alloy and there is no evidence of B2 phase precipitation. Less Fe can lower the concentration of Al in both the fcc and L12 phases during aging at a lower temperature of 620 °C when the L12 phase in both alloys is stable. A lower Fe concentration can also lead to more Cr and Fe atoms occupying Al sites in the L12 phase, which can result in the formation of more L12 particles. Since more L12 particles were precipitated when the amount of Fe was reduced, the Al0.3CrFe0.6CoNi1.4 alloy exhibits better strength and higher hardness than the Al0.3CrFeCoNi alloy. These findings give us insight into how transition metals affect the behaviour of L12 precipitation and suggest ways to develop and improve L12-strengthened HEAs.

The structural, mechanical and electronic properties of Ti-Al-based compounds by first-principles calculations.

The first-principles calculations with density functional theory were performed to investigate the effects of transition metal elements (Mo, Cu, Fe, Ni and Nb) on the physical properties of the Ti-Al-based compounds. Our optimized crystal parameters are in good agreement with the previous theoretical and experimental values. The mechanical stability is verified by the independent elastic constants. The B/G and Poisson's ratio ν both show that Al6TiMo is brittle, while other compounds exhibit ductility. The values of compression anisotropy of the compounds are small, but the shear anisotropy of AlCu2Ti and AlNi2Ti is much more intense than that of other compounds. The anisotropy in elastic properties of AlFe2Ti and AlNbTi2 is smaller than that of the others. It can be seen that the capacity to compress along c-axis is smaller than that along a-axis and b-axis for AlNbTi2. For AlNbTi2, the anisotropy of the bulk modulus along a-axis relative to b-axis is more insignificant than that along c-axis relative to b-axis. The hardness and Debye temperature verify that AlFe2Ti has the greatest resistance to the plastic deformation and more intense inter-atomic bonding force, respectively. Band structures and DOS are used to investigate the electronic properties. The band structures without band gaps show that these ternary Ti-Al-based compounds are conductors. DOS shows the interactions between elements and gives the bond properties. Density of states and charge density both show the strong covalent properties of AlFe2Ti by the hybridization between Fe-3d and Ti-3d states.

Effect of Transition Metal Elements on High-Temperature Properties of Al–Si–Cu–Mg Alloys

In the present work, we studied the effects of transition metal elements on microstructure evolution and high-temperature mechanical properties via the preparation of new modified alloys with micro-additions of Cr, Ti, V, Zr, Mo, and Mn to address the poor high-temperature performance of Al–Si–Cu–Mg alloys for automotive engines. The results show that the addition of transition metal elements formed a variety of new intermetallic phases that were stable at high temperatures, such as (AlSi)3(TiVZr), (AlSi)3Ti, (AlSi)3(CrVTi), Al74Si6Mn4Cr2Fe, Al85Si5Mn2Mo2CrFe, Al0.78Fe4.8Mn0.27Mo4.15Si2, (AlSi)2(CrVTi)Mo, and Al13(MoCrVTi)4Si4, and these phases evidently improved the ultimate high-temperature tensile strength and yield strength. The ultimate tensile strength and yield strength of the modified alloy increased by 17.49% and 31.65% when the test temperature increased to 240 °C, respectively, and by 71.28% and 74.73% when the test temperature increased to 300 °C, respectively. The fundamental reason for this change is that the intermetallic phase hinders the expansion of cracks, which can exist stably at high temperatures. When a crack extends to the intermetallic phases, it will break along with the intermetallic phases or propagate along the morphological edge of the intermetallic phases.

Transition Metal Elements as Ni/GDC Dopants for the H2O Electrolysis Process in SOECs: Fe-Ni vs Au-Mo-Ni Interaction

The presented study focuses on the effect of transition metal elements as dopants of the commercial NiO/GDC powder for the Solid Oxide H2O electrolysis. Specifically, the experimental comparison is between Au, Mo and Fe doping. Comparative electrocatalytic measurements with I-V curves and Electrochemical Impedance Spectra (EIS) analysis are presented in the range of 800-900 °C between electrolyte-supported cells with Ni/GDC, 3Au-3Mo-Ni/GDC and 2Fe-Ni/GDC, as the fuel electrode. In summary, the cell comprising the ternary 3Au-3Mo-Ni/GDC electrode performed significantly better while 2wt% Fe-Ni/GDC proved to be not successful. The superior performance of the Au-Mo-Ni ternary sample is primarily ascribed to the enrichment of the surface with Au and of the bulk phase with Mo, through the formation of Ni-Au-Mo solid solution. The involved elements modify the physicochemical properties of the electrode, improving the: (i) H2O re-oxidation rate, (ii) electronic conductivity and (iii) electrochemical interface. In regards to the Fe-doping, it is worth to be stressed that there are key preparation/modification parameters, which can tune the properties of Fe-Ni/GDC as a promising SOEC fuel electrode.

Effect of transition metal elements (Cu, Ni, Co and Fe) on the mechanical properties of Ti-based bulk metallic glass composites

A series of Ti-based Ti45Zr25Nb6Sn2TM5Be17 (at.%, TM = Cu, Ni, Co and Fe) BMG composites were studied to show the effect of transition metal elements on the microstructure, intrinsic properties and mechanical properties of Ti-based BMG composites. The research shows that the transition metal elements are distributed mainly in the glass-matrix, substitution of which influences significantly the Young's modulus and hardness of glass-matrix. Different from the load-bearing model, the yielding strength of the BMG composites relates highly to not only the yielding strength of the dendrite-phase but also that of the glass-matrix. The plasticity of the BMG composites is highly dependent on the average stress concentration factor of the dendrite-phase. A useful rule for preparing of BMG composite with high strength and excellent plasticity is herein proposed, where tailoring simultaneously the properties of dendrite-phase and glass-matrix is suggested to be a better choice to obtain a good compromise between strength and plasticity.

Effect of transition metal elements on the structural and optical properties of ZnO nanoparticles

Undoped and transition metal (TM)-doped ZnO nanoparticles (Zn0.98X0.02O-NPs, X = Mn, Cr, Co and Fe) were synthesized from a metal nitrate precursor and gelatin by a sol–gel method. The compounds were synthesized at calcination temperatures of 550∘C for 6 h. The synthesized undoped/doped ZnO-NPs were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). XRD results indicated that the sample products were crystalline with a hexagonal wurtzite phase. SEM images showed the ZnO-NPs nearly spherical shapes and a non-uniform shape for doped ZnO-NPs. The crystalline development in the ZnO-NPs was investigated by X-ray peak broadening. The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain of the undoped and doped ZnO-NPs. The obtained results showed that strain of the NPs plays an important role in peak broadening; moreover, the mean crystalline size of the undoped and doped ZnO-NPs estimated from the SEM and the SSP method was highly inter-correlated. Finally, optical properties of the samples were studied by a UV–Vis spectrometer.

Effect of transition metal element addition upon liquid phase reforming of methanol with water over TiO2 supported Pt catalysts

Addition effects of various transition metal elements were investigated upon catalysis of TiO2 supported Pt metal for the liquid phase reforming of methanol. Addition of Mo or Fe increased the catalytic activity and selectivity of Pt/TiO2 remarkably, while added Ni or Co showed poor improvement. The addition methods of transition metal elements, i.e. co-impregnation or successive impregnation, also exhibited significant effect on the catalytic behavior. XRD, XPS, FT-IR and XAFS measurements revealed that the added Mo or Fe species that formed a low valent thin oxide layer over TiO2 surface and Pt metal were highly dispersed on the layer, while added Ni or Co formed alloys with Pt. Pt species on the oxide overlayer are supported as highly dispersed stable cationic particles, and their cationic state may depress the inhibition with strongly adsorbed CO for the reforming reaction.

Effect of transition-metal elements on the superconductivity of Y-Ba-Cu-O.

We have fabricated samples of the form ${\mathrm{YBa}}_{2}$(${\mathrm{Cu}}_{0.9}$${\mathrm{A}}_{0.1}$${)}_{3}$${\mathrm{O}}_{6+\mathrm{y}}$ where A=Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn. The superconducting state was investigated by both resistance and magnetization measurements. In addition, the magnetic susceptibility above ${T}_{c}$ has been measured. ${T}_{c}$ was found to be strongly correlated with the size of the paramagnetic moments, largely due to scattering from the magnetic sites. In the sample containing Zn, however, ${T}_{c}$ was dramatically reduced due to filling of the antibonding d band.