Increase Of Sc Content Research Articles

Microstructures and properties evolution of spray-deposited Al-Zn-Mg-Cu-Zr alloys with scandium addition

In this work, the effect of Sc content on the microstructures and mechanical properties of Al-Zn-Mg-Cu-Zr alloys prepared using spray deposition was studied. Microstructure observations reveal that not only the grain size, but also the coarse secondary phase can be refined by Sc addition through the formation of a hybrid structure coupled by η-MgZn2 and Al3(Sc, Zr) phases near and at the grain boundaries. It is inferred that the primary Al3(Sc, Zr) particles can act as nucleation sites for the η-MgZn2 phase during the deposition process. With the increase of Sc content, the continuous secondary phase at the grain boundaries converts gradually into small discontinuous particles, which contributes to the considerable improvement in tensile strength and elongation. The alloy with 0.2 wt% Sc exhibits excellent combinations of ultimate tensile strength of 831±3 MPa and elongation of 10.2 ± 0.4% after T6 heat treatment, and the elongation increases by almost 50% compared to the Sc-free base alloy.

A novel silanized CoFe2O4/fluorinated waterborne polyurethane pressure sensitive adhesive

A novel silanized CoFe2O4/fluorinated waterborne polyurethane (SC/FWPU) pressure sensitive adhesive was synthesized and characterized by atomic force microscopy (AFM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and contact angle tester. The adhesive properties were measured in a test machine. Experimental results showed that the hydrophobicity, thermal stability, dynamic mechanical properties, as well as adhesive properties of SC/FWPU were improved with the incorporation of SC into FWPU. The dynamic hydrophobicity can be well described by the wetting kinetic model. The spreading-penetration parameter increased with an increase in SC content. The higher the spreading-penetration parameter is, the faster the contact angle reaches equilibrium, and the faster the SC/FWPU pressure sensitive adhesive penetrates and spreads.

Study on luminescence properties of Nd3+–La3+ and Nd3+–Sc3+ codoped M′-LuTaO4 phosphors

Nd3+ doped M′-LuTaO4 phosphor, with high density (9.8g/cm3) and relatively fast decay time (261ns), is a potential heavy scintillator. In this work, Nd:LuTaO4 is codoped with La3+ or Sc3+ ion and its structure and luminescent properties as a function of their concentration are studied. The structural parameters are obtained by Rietveld refinement. The strongest emission peak is located at 419nm which corresponds to the 4D3/2→4I13/2 transition of Nd3+. The decay times of 4D3/2→4I13/2 transition in Nd/La:LuTaO4 and in Nd/Sc:LuTaO4 are much shorter than that in Nd:LuTaO4, which decrease to 211ns and 163ns, respectively. It is also found that the decay time of 4D3/2→4I13/2 transition in Nd/La:LuTaO4 increases with the increase of La content, and the decay time of 4D3/2→4I13/2 transition in Nd/Sc:LuTaO4 decreases with the increase of Sc content. Besides, the mechanism is discussed respectively.

Tunable optoelectronic and ferroelectric properties in Sc-based III-nitrides

Sc-based III-nitride alloys were studied using density functional theory with special quasi-random structure methodology. ScxAl1−xN and ScxGa1−xN alloys are found to be stable in hexagonal phases up to x ≈ 0.56 and x ≈ 0.66, respectively, above which rock-salt structures are more stable. Epitaxial strain stabilization can prevent spinodal decomposition up to x ≈ 0.4 (ScxAl1−xN on AlN or GaN) and x = 0.27 (ScxGa1−xN on GaN). The increase in Sc content expands the in-plane lattice parameter of ScxAl1−xN and ScxGa1−xN alloys, leads to composition- and strain-tunable band gaps and polarization, and ultimately introduces ferroelectric functionality in ScxGa1−xN at x ≈ 0.625. A modified Becke-Johnson exchange-correlation potential was applied to study the electronic structures, which yielded band gaps comparable to those from hybrid functional calculations, yet in a much shorter computational time. The alloys were found to retain wide band gaps, which stay direct up to x = 0.25 (ScxAl1−xN) and x = 0.5 (ScxGa1−xN). The band gaps decrease with increasing x for ScxAl1−xN, in which the Sc-3d states dominate at the conduction band minimum and lead to flat electron dispersion at the Γ point. Conversely, the band gaps increase with increasing x for ScxGa1−xN (up to x = 0.5), in which Sc-3d states do not contribute to the conduction band minimum at the Γ point.

XPS and cathodoluminescence studies of HfO2, Sc2O3and (HfO2)1-x(Sc2O3)xfilms

X-ray photoelectron spectroscopy (XPS) and cathodoluminescence (CL) method have been employed to study the chemical composition and the oxygen vacancy concentration of HfO2 , Sc2 O3 and (HfO2 )1−x (Sc2 O3 )x films. It was found that the increase of Sc content led to monotonic decreasing the Hf4 f7/2 and Sc2 p3/2 binding energies indicating to form solid solution (HfO2 )1−x (Sc2 O3 )x . All the samples characterized by the intensive CL spectra with maximum around 3 eV which originated due to some radiative recombination emission caused by oxygen deficiency. The concentration of oxygen vacancy in the Sc-doped HfO2 is sensitive to the Sc content and as a result the intensity of CL spectra of (HfO2 )1−x (Sc2 O3 )x is lower that those of pure HfO2 and Sc2 O3 .

Effects of scandium on the bandgap and location of Ce3+ levels in Lu1−xScxBO3:Ce scintillators

Transparent Lu1−xScxBO3:Ce (x = 0.3, 0.5, 0.7, 0.8) scintillation crystals were grown by Czochralski method. Vacuum ultraviolet excitation spectra and thermoluminescence glow curves revealed the narrowing of bandgap and the redshift of the first electric dipole-allowed fd transition of Ce3+ with the increase of Sc content. The ionization energy evaluated from the photoluminescence decays as a function of temperature indicated that, with increasing Sc content, the thermal ionization probability occurring from 5d1 relaxed state of Ce3+ was enhanced, which degraded the scintillation efficiency of Lu1−xScxBO3:Ce crystals.

Thermal Expansion and Phase Transition Behavior of Al2-xMx(WO4)3 (M=Y, Ga and Sc) Ceramics

In order to obtain materials with a tailored thermal expansion, in particular zero-thermal-expansion between -50~100°C, the possibility of preparation, thermal expansion behavior and phase transition of Al2-xMx(WO4)3 (M: Y, Ga and Sc) have been examined. Y was not substituted for the Al site in Al2(WO4)3. Al2-xGax(WO4)3 single phase could be prepared in x range as high as 0.4. The phase transition temperature involving abrupt expansion increased with an increase of Ga content, resulting in no phase transition for Al1.6Ga0.4(WO4)3 between -50~100°C. However, zero-thermal expansion could not be obtained in Al2-xGax(WO4)3 at the temperature range. Al2-xScx(WO4)3 single phase was obtained for the whole x range. The temperature of the phase transition decreased with an increase of Sc content and the abrupt expansion due to the phase transition disappeared above -50°C for the specimen with x larger than 0.3. The thermal expansion coefficient could be controlled with Sc content and zero-thermal-expansion was observed for the specimens with x around 0.1 and 1.5.

Microstructure, tensile strength and wear behaviour of Al–Sc alloy

A systematic study on the behaviour of commercial pure Al with the addition of scandium (Sc) was carried out and the effects of Sc addition on tensile and wear behaviour were investigated. The Sc addition up to 0.4 wt.% did not show any grain refinement and at higher addition levels, remarkable grain refinement due to the presence of Al3Sc precipitates during solidification was observed. The SEM, TEM studies showed a uniform distribution of Al3Sc intermetallics in Al matrix. Sc addition to Al exhibited excellent results of grain refinement as compared to the addition of TiBAl master alloy. A continuous increase in mechanical properties as well as wear resistance behaviour was noticed with the increase of Sc content. Remarkable improvement was observed after homogenization of Sc added Al alloys.

Scandium bioaccumulation and its effect on uptake of macro- and trace elements during initial phases of plant growth

Uptake of scandium (Sc) by wheat seedlings was studied during 6-d germination of wheat seeds in Sc supplemented medium and during 1-week growth of wheat seedlings germinated under normal conditions in soil amended with Sc. The most significant increase in Sc content in the seedlings was observed during germination of seeds in Sc supplemented medium. Transfer of the seedlings to normal soil resulted in a decrease of Sc level in upper plant parts, but Sc concentration in roots remained rather high. Scandium bioaccumulation caused variations in concentrations of Na, K, Ca, and Zn 0n different parts of the seedlings. The least variations were observed in leaves.

Electrical properties and the metal-insulator transition in(ScxTi1−x)2O3

The resistivity, thermoelectric power, and lattice parameters of ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ doped with varying amounts of scandium have been measured between 77 and 700 K. A metal-to-insulator transition has been encountered in all specimens between approximately 400 and 600 K. The magnitude of the transition is nearly independent of Sc doping up to 0.33 at.% and grows with further increase in Sc content of the specimens. The activation energy for conduction at first declines and then increases with increasing Sc content. Since Sc doping has no large effect on the transition temperature, it is concluded that the transition is largely lattice dominated.