Effect Of Transition Elements Research Articles

Theoretical Investigation of Effects of Transition Elements on Phase Stabilities and Elastic Properties of the γ′ Phase in Co–V–Ta Superalloys

In order to improve the thermal stability and mechanical properties of W-free light-weight Co–V–Ta-based superalloys, the effects of alloying elements including Sc, Ti, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Hf, W, Re, Os, Ir, and Pt on γ′-Co3(V, Ta) stability and elastic properties were studied. The results from the reaction energy indicate that Sc, Ti, Y, Zr, Nb, Mo, Hf, and W tend to occupy the V site, whereas Cr, Mn, Fe, Ni, Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt prefer to occupy the Co site. It was found that Sc, Ti, Y, Zr, Fe, and Mn stabilize the γ′-Co3(V, Ta) phase by raising the phase-transfer energy. The addition of Mo and W increases the bulk modulus, shear modulus, and Young’s modulus. According to Pugh’s classical criterion, the γ′-Co3(V, Ta) phase is an intrinsically brittle material, and the addition of elements such as Tc and Re significantly enhances the ductility. At finite temperature, the doping of Sc, Ti, Mn, Fe, and Hf enhances the relative stability of the γ′-Co3(V, Ta) phase in the whole temperature range from 0 to 1200 K and are candidates for improving the stability of the γ′-Co3(V, Ta) phase.

Effect of Transition Elements on the Thermal Stability of Glassy Alloys 82Al-16Fe-2TM (TM: Ti, Ni, Cu) Prepared by Mechanical Alloying.

In the present study, the thermal stability and crystallization behavior of mechanical alloyed metallic glassy Al82Fe16Ti2, Al82Fe16Ni2, and Al82Fe16Cu2 were investigated. The microstructure of the milled powders was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results showed remarkable distinction in thermal stability of the alloys by varying only two atomic percentages of transition elements. Among them, Al82Fe16Ti2 alloy shows the highest thermal stability compared to the others. In the crystallization process, exothermal peaks corresponding to precipitation of fcc-Al and intermetallic phases from amorphous matrix were observed.

Effects of Transition Elements on the Structural, Elastic Properties and Relative Phase Stability of L12 γ′-Co3Nb from First-Principles Calculations

In order to explore novel light-weight Co-Nb-based superalloys with excellent performance, we studied the effects of alloying elements including Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir and Pt on the structural stability, elastic and thermodynamic properties of γ′-Co3Nb through first-principles calculations. The results of transfer energy indicate that Y, Zr, Hf and Ta have a strong preference for Nb sites, while Ni, Rh, Pd, Ir and Pt have a strong tendency to occupy the Co sites. In the ground state, the addition of alloying elements plays a positive role in improving the stability of γ′-Co3Nb compound. The order of stabilizing effect is as follows: Ti > Ta > Hf > Pt > Ir > Zr > Rh > V > Ni > W > Sc > Mo > Pd > Re > Ru. Combining the calculation results of elastic properties and electronic structure, we found that the addition of alloying elements can strengthen the mechanical properties of γ′-Co3Nb, and the higher spatial symmetry of electrons accounts for improving the shear modulus of γ′-Co3Nb compound. At finite temperatures, Ti, Ta, Hf, Pt, Ir, Zr and V significantly expand the stabilization temperature range of the γ′ phase and are potential alloying elements to improve the high-temperature stability of the γ′-Co3Nb compounds.

Effect of transition elements on dispersoid formation and elevated-temperature mechanical properties in 6082 aluminum alloy

ABSTRACT The effect of transition elements, specifically Mn, Cr, V, and Mo, on dispersoid formation and mechanical properties in 6082 aluminum alloy was studied. The elevated-temperature mechanical properties were evaluated based on the compressive yield strength and creep resistance. The results indicated that the addition of Mn to the 6082 alloy resulted in the formation of a large number of the thermally stable α-Al(MnFe)Si dispersoids, thereby significantly improving the elevated-temperature mechanical properties of the alloy. Subsequent additions of Cr, V, and Mo increased the amount of Mn-bearing intermetallic phases, which decreased the supersaturation levels of Mn and Si in the α-Al, and consequently decreased the volume fraction of the dispersoids. The alloys containing Cr, V, and Mo exhibited similar yield strengths at 300°C and higher yield strengths at room temperature compared to the alloy containing only Mn. The size effect of the smaller dispersoids containing Cr, V, and Mo together with the solid-solution hardening of these elements could balance out the strength decrease resulting from the decreased volume fraction of the dispersoids. The additions of Cr, V, and Mo significantly increased the creep resistance of the Mn-containing 6082 alloy. Vanadium induced the highest creep resistance followed by Cr and Mo. Solute atoms of these elements with low diffusivity in the aluminum matrix contributed significantly to increasing the creep resistance at 300°C.

Effects of transition elements on the site preference, elastic properties and phase stability of L12 γ′-Co3(Al, W) from first-principles calculations

We performed a systematic study of alloying effects on the site preference, elastic properties and phase stability of L12 γ′-Co3(Al, W) in terms of the first-principles calculations. Up to twenty-one transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Tc, Ru. Rh, Pd, Hf, Ta, Re, Os, Ir and Pt) were considered in this work. We find that Sc, Ti, V, Cr, Mn, Y, Zr, Nb, Mo, Tc, Hf, Ta, Re and Os favor to occupy the Al site, and Fe, Ni, Ru. Rh, Pd, Ir and Pt favor to occupy the Co site, except for Y, Fe and Ru, other transition metal elements can stabilize the L12 γ′-Co3(Al, W) at 0 K. By using stress-strain method, the elastic properties including bulk modulus, shear modulus and Young’s modulus were evaluated. It is verified that the elastic properties of L12 γ′-Co3(Al, W) depend on not only volume change but also electron density as well as electronic configurations. The thermodynamic results of phase stability of L12 γ′-Co3(Al, W) reveal that Hf, Ti and Ta are the promising alloying elements to improve the stability of L12 γ′-Co3(Al, W).

Effect of Transition Elements on Biochemical Oxygen Demand

The results of model experiments on the effect of transition elements (iron, manganese) and sulfide ions on the values of chemical (COD) and biochemical oxygen demand (BOD) are presented. It is shown that, in the presence of transition elements in water, BOD is overestimated. In the presence of 100 mg/L of iron(II) and >0.05 mg/L of sulfides in water, the BOD values exceed those of COD.

The effect of ambient temperature on the optical properties and crystalline quality of ZnSe and ZnSe:Cu NCs grown by rapid microwave irradiation

ZnSe nanocrystals (NCs) of size about 1.8 nm were prepared in aqueous media and were grown using microwave irradiation, which is simple and inexpensive method in which it needs very short reaction time. In this method, using selenium powder and NaBH4 the source of Se ions has been provided and then, the present solution has been injected to Zn ions source. Also solutions of sodium hydroxide (NaOH) and thioglycolic acid were used to adjust the pH of samples and capping agent, respectively. To study the effect of transition elements on the properties of these nanoparticles, Cu ions were used as impurity. After the completion of nucleation and formation of nanoparticles, the ultimate solution was microwave irradiated for 6 min. To investigate the nanoparticles morphology and their optical properties, X-ray diffraction (XRD) and UV–Visible (UV–Vis) optical spectroscopy were used. UV–Vis spectra were recorded at different ambient temperatures. XRD analysis demonstrated cubic zinc blende NCs and field emission scanning electron microscopy (FESEM) image indicated round shape NCs. Using the UV–Vis outputs, the optical band gap (Eg DASF) and also the exact nature of charge carriers optical transitions were studied and evaluated in ZnSe and ZnSe:Cu nanocrystals, by employing an accurate new method [called in literatures as derivation of absorption spectrum fitting (DASF)]; this method only requires the measurement of the absorbance spectrum of the sample, avoiding any needs to film thickness or any other parameters. According to the UV–Vis analysis, band gap of the nanoparticles was determined and was in the range of 3.350–3.652 eV depending on the temperature and Cu dopant, showing the decreasing trend of energy gap with increasing ambient temperature and impurity. The decreasing trend of Eg DASF with ambient temperature, confirm the semiconducting nature of the present samples. Also, the direct gap nature of their optical transitions was justified. moreover, the band tailings (Urbach energy: ETail) was estimated and was within the range of 0.052–0.106 eV, which was so small comparing to the corresponding band gap values; these small ETail valus confirm the sharpness of valence and conduction band edges, and so good degree of crystallinity of the studied samples. Furthermore, optical transition index (m), dielectric constant (e), size of the nanoparticles and the refractive index (n) were evaluated.

Effect of transition elements on the microstructure and tensile properties of Al–12Si alloy cast under ultrasonic melt treatment

This paper shows that the addition of transition elements significantly influences the microstructure and tensile properties of Al–12Si alloy cast under ultrasonic melt treatment (UST). The alloys contained primary Si, eutectic Si and a variety of intermetallic compounds (IMCs); the addition of Mn and Ni changed the solidification sequence by forming primary α-Al15(Fe,Mn)4Si2 and ε-Al3Ni prior to primary Si formation. The primary Si and primary IMCs competitively consumed the nucleation sites introduced by UST, thereby influencing their refining efficiencies; the efficiency of primary Si refinement by UST increased with increasing the fraction of primary Si formed prior to IMC formation, whereas it deteriorated with increasing primary IMC fraction. The refining efficiency of eutectic Si and eutectic IMCs was not affected by the type and fraction of the primary phase. Using a Ti sonotrode for UST caused Ti contamination, resulting in grain refinement by forming Ti(Al,Si)3 particles and increasing the amount of Ti solutes. Regardless of transition elements content, the application of UST improved the tensile strength at 25 °C and 350 °C. The refinement of IMCs caused by UST allowed the alloy to contain more IMCs without deterioration of room-temperature tensile strength. This enhanced the increment of high-temperature tensile strength by IMCs. Ductility of heavily alloyed systems was also improved by UST.

The Effect of Transition Elements on High‐Temperature Mechanical Properties of Al–Si Foundry Alloys–A Review

The high temperature mechanical performance of Al–Si alloys can be enhanced by alloying with transition metals, induced by the formation of thermally stable and coarsening resistant precipitates in the microstructure. However, the binary dispersoids such as Al3Zr can be less effective due to limitations encountered during conventional manufacturing processes. Further improvements can be achieved through the transformation of these binary trialuminides into ternary or quaternary forms by alloying with appropriate elements. The role of transition elements in improving high temperature mechanical properties of Al–Si alloys from both theoretical and practical viewpoints is critically reviewed.

Mechanical properties of 7475 aluminum alloy sheets with fine subgrain structure by warm rolling

The effect of transition elements on grain refinement of 7475 aluminum alloy sheets produced by warm rolling was investigated. The alloy which contains zirconium instead of chromium showed ultra fine structures with stable subgrains after warm rolling at 350 °C, followed by solution heat treatment at 480 °C. The average subgrain diameter was approximately 3 μm. It became clear that zirconium in solution has the effect of stabilizing subgrains due to precipitation of fine Al3Zr compounds during warm rolling. On the other hand, chromium-bearing compounds precipitate before warm rolling and they grow up to relatively large size during warm rolling. The warm rolled sheets with fine subgrains have unique properties compared with conventional 7475 aluminum alloy sheets produced by cold rolling. The warm rolled sheets solution heat treated had subgrain structures through the thickness with a high proportion of low-angle boundary less than 15°. The strength of the warm rolled sheets in T6 condition was about 10% higher than that of conventional 7475 aluminum alloy sheets. As the most remarkable point in the warm rolled sheets, the high Lankford (r) value of 3.5 was measured in the orientation of 45° to rolling direction, with the average r-value of 2.2. The high r-value would be derived from well developed β-fiber textures, especially with the strong {011}«211» brass component. The warm rolled sheets also had high resistance to SCC. From Kikuchi lines analysis and TEM images, it was found that PFZs were hardly formed along the low-angle boundaries of the warm rolled sheets in T6 condition. This would be a factor to lead to the improvement of resistance to SCC because of reducing the difference in electrochemical property between the grain boundary area and the grain interior.

Modification of aluminium and aluminium alloys by AL-B master alloy

Chemical compositions and microstructures affect on mechanical – physical and working properties of aluminium and aluminum alloys. Transition elements, such as Ti, V, Cr, Zr in solid solution greatly reduce the electrical conductivity of aluminium and its alloys. For reduction of detrimental effects of transition elements, Al-B master alloys are added into molten aluminium to occur reactions of boron and transition elements to form diborides of titanium, vanadium, chromium and zirconium, which are markedly insoluble in molten aluminium, then these transition elements have an insignificant effects on conductivity. In addition, Al-B master alloys is also used as a grain refiner of aluminium and aluminium alloys. Aluminium borides particles in Al-B master alloys act as substrates for heterogeneous nucleation of aluminium and its alloys. Al-B master alloys are prepared from low cost materials, such as boric acid H3BO3 and cryolite Na3AlF6, by simple melting method, easily realize in electrical wire and cable factories.

La<sub>1.5</sub>Sr<sub>1.5</sub>Mn<sub>2</sub>O<sub>7−</sub><i><sub>σ</sub></i>の粒子状物質酸化に及ぼす遷移金属元素置換の効果

The effect of transition element (TE = Fe, Ni, Cu) doping on the particulate matter (PM) oxidation in the Ruddlesden-Popper-type (RP - type) compound La1.5Sr1.5Mn2O7−σ was investigated for a dopant concentration fixed of 0.05 %. Though there is no structural change accompanied by doping, thermogravimetry curves show the noticeable difference according to the dopant. Then, Cu doping is found to be more effective than Fe and Ni doping. Finally, it was found that La1.5Sr1.5Mn1.95Cu0.05O7−σ is one of the promising PM oxidation catalysts for the catalyzed soot filter.

The Effects of Transition Elements & PBL on Problem-Solving Skills and Class Participation Attitude of High School Students in Special Class

The Effects of Transition Elements & PBL on Problem-Solving Skills and Class Participation Attitude of High School Students in Special Class

The Effects of Transition Elements and PBL on Problem-Solving Skills of High School Students with Mental Retardation

강혜경·김정효·이경순. 전환교육 요소를 적용한 문제중심학습이 정신지체 고등학생의 문제해결력에 미치는 영향 및 중재 교사의 경험. 『특수교육』, 2011, 제10권, 제3호, 143-175. 본 연구에서는 전환교육 요소를 적용한 문제중심학습(PBL) 프로그램을 개발하고 이를 정신지체 특수학교 고등학생을 대상으로 사회과 수업시간에 적용한 후, PBL 적용이 정신지체 고등학생의 문제해결력에 미치는 영향을 살펴보고자 하였다. 본 연구의 참여자는 서울 시내 정신지체 특수학교 고등부에 재학 중인 학생 24명과 이들을 담당하는 교사 12명으로, 이 중 참여 학생은 실험집단과 비교집단에 각 12명씩, 중재자인 교사는 각각 4명, 8명으로 총 12명이었다. 실험집단에는 전환교육 요소를 적용한 사회과 PBL 수업이, 비교집단에는 일반적인 사회과 수업이 이루어졌다. 본 연구의 결과 PBL 수업에 참여한 실험집단 문제해결력 점수는 비교집단보다 통계적으로 유의하게 높았다. 이로써 본 연구에서 개발, 적용한 PBL의 교수방법과 절차가 정신지체 특수학교 고등학생의 문제 해결력과 전환성과 향상을 위한 교육에 적용 가능성이 높았다고 볼 수 있다. 중재 교사들은 전환 교육 요소를 적용한 PBL 수업에 대해 긍정적인 특성을 피력하였고, 아울러 몇 가지 개선점과 요구를 제안하였다.

ESR Studies on ${\rm Bi}_{0.5}{\rm Ca}_{0.5}{\rm Mn}_{0.95}{\rm TE}_{0.05}{\rm O}_{3}$ (${\rm TE}={\rm V}$, Cu and Zn)

In this work, the effect of transition element ( TE=V, Cu, and Zn) substitution at Mn site on the electron spin resonance (ESR) of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> was explored. The temperature (T) dependent double integrated intensity (DI) and peak to peak linewidth provide the estimation of charge ordering (CO) temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> , long-range antiferromagnetic (AFM) onset temperature, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> , ordering temperature, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> , and the information about the magnetic interactions. The T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> values are 317 K, 317 K, 321 K, and 311 K for undoped, V, Cu, and Zn doped samples, respectively. It is noticed that V doping sharpens the CO transition, whereas Cu and Zn doping smears the CO transition. The temperature dependent magnetization measurements support the ESR observations. In the temperature range T >; T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> , ferromagnetic (FM) correlations dominate. In the temperature range T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CO</sub> >; T >; T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</sub> , the samples are in the paramagnetic (PM+CO) phase. The AFM interactions dominate in the doped samples in this temperature range. The orbital ordering (OO) sets in progressively with decreasing temperature leading to onset of long-range AFM ordering at ~ 200 K for undoped and in the range 190-170 K for doped samples. The present study shows the strong competition between FM and AFM correlations as a function of temperature and composition of the sample.

The effect of transition elements on the superplastic behavior of Al–Mg alloys

Research on the high temperature superplastic deformation behavior of Al–Mg–X (X: Cr; Zr; Mn) alloys was carried out and the effect of transition elements and thermomechanical processing on the microstructure and superplastic behavior of Al–Mg–X alloys were also examined. In Al–Mg–Cr alloy, which was thermomechanically processed with an intermediate annealing, the maximum elongation (close to 730%) was observed at 530 °C. The strain rate at which the maximum elongation occurred was faster in Al–Mg–Cr (1×10 −3 s −1) alloy than in Al–Mg–Mn (1×10 −4 s −1) alloy. The observation of the maximum elongation at a lower temperature (500 °C) in Al–Mg–Zr alloy may be associated with the finer size of dispersoids in this alloy. The superplastic behavior of Al–Mg–X alloys was found to be greatly influenced by the nature of intermetallic particles.

The high-temperature work function of sintered dilute solution tungsten-lridium alloys

The effect of transition element additives molybdenum, rhenium, iridium, and osmium on the effective work function of tungsten has been the focus of thermionics research for several years.[1- 5] In this study, iridium-added tungsten powder mixtures were cold compacted and sintered to produce a range of tungsteniridium electrodes. An electron emission study was subsequently carried out to evaluate the work function behavior of the consolidated alloys. The work function was obtained from measurements of the current emitted from the electrode surface under ultrahigh vacuum conditions in the temperature range of 1800 to 2500 K using a vacuum emission vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature. Microstructural evaluation of the alloys indicated that the tested surfaces displayed accentuated thermal etching of the grain boundaries together with the fact that the final grain sizes in the sintered alloys were three to five times smaller than those found in equivalent are-melted alloys that were studied in earlier work.[4,5] Scanning electron microscopy (SEM) micrographs of the tested surfaces of the sintered alloys containing the highest iridium levels (~2 wt % ) show a high level of structural distortion, particularly in the vicinity of grain boundaries and corners. The extent of these distortions was found to vary with the iridium content, i.e., the W-IR3M and W-IR2M. The samples with compositions lower than 0.5 wt % Ir were virtually devoid of distortions. It is proposed that, during homogenization carried out prior to testing, a net accumulation of iridium occurs near the surface, particularly in the vicinity of structural heterogeneities. Subsequent cooling leads to the precipitation of iridium-rich second phase sources, which when reheated to the testing temperatures supplies iridium to a surface monolayer. This mechanism is capable of explaining the observed work function trends during high- temperature testing.

Electrodeposition of Ni-transition alloys for the oxygen evolution reaction

The oxygen evolution reaction (OER) is the anodic reaction in several industrial electrolytic processes. The objective of this work was to develop a new electrocatalytic material for long-lasting and economical high performance electrodes. New electrodes were prepared by electrodeposition of nickel, nickel-ruthenium and nickel-iridium alloys. They were then activated by anodic polarization at 100 mA cm−2 to form an oxide layer. The electrocatalytic activity was characterized for the OER in 5M KOH solution. The results show that nickel-iridium alloys provide greater electrocatalytic activity for the OER and better corrosion resistance than nickel-ruthenium in alkaline solution. The effects of transition elements on improving the performance of the nickel electrode are then discussed.

Studies on the redox properties of the heteropolytungstosilicates substituted by transition elements

The redox properties of the tri-heteropolytungstosilicates of transition elements KnSiZ(H2O)W11O39 (Z Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+). In solution have been studied with polarography and cyclic voltammetry as well as with ultraviolet spectroscopy and X-ray photoelectron spectroscopy. The order of the polarographic half-wave potentials (E1/2) of these heteropolyanions is as follows: ZNi2+>Co2+>Zn2+>Fe2+>Mn2+. We have found that the E1/2 of heteropolyanions could be correlated linearly with both the electronegativities X of the transition elements and the logarithm of the rate constants (log ke) of reaction of transition metal ions with hydrated electrons. The reduction mechanism and effects of transition elements on the redox properties of the heteropolyanions have been discussed.

Effect of transition elements on the properties of MC carbides in IN-100 nickel-based superalloy

Effect of transition elements on the properties of MC carbides in IN-100 nickel-based superalloy