Materials Letters: X最新文献

We report the formulation of luminous paints with calcium-based quinoline complex, bis(8-hydroxyquinoline) (calcium) – Caq₂ as a pigment (where Ca = Calcium, q = 8-hydroxy quinoline). Fourier transform infrared (FTIR) spectra, UV–Visible absorption, Photoluminescence (PL) spectra and photometric evaluation of the pigment were probed to evaluate its structural, optical and photometric properties. The excitation spectra of Caq₂ pigment portrays a broad excitation peak at 370 nm, while emission spectra reveal a broad peak, registered at 473 nm which falls in the bluish-green region of the visible spectrum. Further, fluorescent paints were formulated on glass slides with epoxy resin/ urea formaldehyde as binder and toluene as solvent. The results reveal the change in intensity of the painted panels in the following order I_{ZnO Epoxy(50%)} > I_Epoxy based pure pigment > I_UF based pure pigment > I_{ZnO Epoxy(10%)} > I_{ZnO UF(10%)}. These results reveal the potential of the pigment as one of the components of fluorescent paint.

Rare earth diphenylphosphinates – [RE(dpp)₃]_n – are low-dimensional nanostructured luminescent materials with considerable thermal and chemical stability, obtained in powder form, consisting of highly insoluble nanowire/nanorod-shaped particles. As a potential candidate for applications as nanocrystalline scintillator devices, [Eu(dpp)₃]_n has been synthesized by wet route precipitation methodologies. X-ray excited optical luminescence (XEOL) measurements revealed that the samples show intense emission under X-ray excitation, presenting structural and electronic stability against continuous and prolonged exposure to ionizing radiation without changing the chemical environment in which the trivalent europium ion is inserted. Indeed, the self-structuring of [RE(dpp)₃]_n in a polymeric matrix of high thermal stability allowed [Eu(dpp)₃]_n to be a low-dimensional nanostructured luminescent coordination polymer resistant to radiation damage.

The present work reported the synthesis of Eu³⁺-activated K₃Ca₂(SO₄)₃F sulfate-based phosphors via a solid-state reaction method (SSR). The crystal structure of as-synthesized phosphor was studied by XRD analysis. The PL and PLE spectrum were investigated using photoluminescence spectroscopy. The PL excitation spectrum monitored at 616 nm shows sharp line excitation peaks at 395 nm,466 nm and 535 nm, attributes to ⁷F₀→ ⁵L_6, ⁷F₀→ ⁵D_2, and ⁷F₀→ ⁵D₁ transitions respectively. The PL spectrum under UV excitation of 395 nm exhibits emission in the red region centered at 592 nm and 616 nm, corresponding to ⁵D₀→ ⁷F_1, and ⁵D₀→ ⁷F₂ transitions of Eu³⁺ ions in the host. The CIE coordinates confirm the emission in the orange-red region positioned at (0.6824, 0.3175) with color purity of 97.37% and CCT 3872.2 K. The obtained outcome reveals that the reported K₃Ca₂(SO₄)₃F: Eu³⁺ phosphor is the best candidate as UV excitable orange-red emitting phosphor for w-LEDs.

A novel pyrene-based fluorescent chemosensor (pyren-1-ylmethyl)-L-valine (1) has been synthesized. 1 is a highly selective chemosensor for detecting Cu(II) ions through fluorescence quenching over other competitive metal ions and showing aqueous-organic solvent-based gelation properties. Rod-shaped surface morphology may be attributed to intermolecular Hydrogen bonding between the carboxylic acid group and π-π stacking of pyrene moiety. In addition, 1 can also be utilized for the practical detection of Cu²⁺ion in natural water samples.

A space solar array includes GaAs solar cell, interconnector, and stranded Cu wire. Due to the preferential high working efficiency, the assembly of solar array is mostly performed using parallel gap resistance welding (PGRW). Since strengthening of the PGRW joints is the key to further extend service life of solar array, it is necessary to elucidate joining mechanism of each connection. In the present research, to clarify the controversy over PGRW joining mechanism between Ag-plated Kovar interconnector and stranded Ag-plated Cu wire, various advanced material characterization methods are conducted to joining interfaces. Experimental results confirm that, in addition to the known Ag/Cu eutectic interface, solid evidence of metallurgy bonding is also found in Cu/Cu interface. Such finding has significant implication for further enlarge the PGRW process window and produce stronger joints.

In the present work, we have synthesized Ca_1.02Sr_1.98Al₂O₆ phosphors with different doping concentrations of Dy³⁺ (0.5 mol% to 4.0 mol%) by simple combustion method. The phase purity of the prepared phosphor has been confirmed by X-ray diffraction (XRD). Detailed investigations have been carried out to study the photoluminescence (PL) and thermoluminescence (TL) properties of the synthesized phosphors. Under 348 nm excitation, the PL emission spectrum shows two intense emission bands at blue and yellow color region due to the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transition of Dy³⁺ ions. In addition, the TL properties of gamma-irradiated Dy³⁺ doped Ca_1.02Sr_1.98Al₂O₆ phosphors were investigated. According to the obtained PL and TL results, the synthesized phosphors have good prospects for future investigations on white LED and TLD applications.

The effect of nitrogen (N₂) partial pressure on the structure and bandgap tunability of RF magnetron sputtered Cadmium Sulphide (CdS) thin films is investigated by varying N₂ partial pressure in Ar/N₂ mixture. In presence of N₂, films have a polycrystalline structure with (0 0 2) preferential orientation, which leads to defect-free, continuous, dense, and fibrous structures with increased roughness. The average optical transmittance increased to > 80 at 500–2500 nm for 30 % N₂ partial pressure, whereas the band gap decreases from 2.45 eV to 2.30 eV with increasing N₂ concentration. This work shows that the bandgap of sputtered CdS thin films can be tuned with the variation of N₂ concentration for customized applications.

Nickel-copper chromite (NiCuCr₂O₄) was synthesized by the co-precipitation method using sodium hydroxide as a precipitating agent. The composition of ammonium nitrate (AN):NiCuCr₂O₄ (mass ratio 98:2) was used for the comparative thermal analysis study. The results suggested that ammonium nitrate containing nickel-copper chromite (AN + NiCuCr₂O₄) can act as a potential energetic material to replace AN in energetic applications. The activation energy of AN + NiCuCr₂O₄ was decreased by 85.7 kJ mol⁻¹ compared to pure AN along with a reduction in the peak decomposition temperature. The lower activation energy and low pre-exponential factor can fasten AN + NiCuCr₂O₄’s decomposition at a lower temperature.

A novel ultrasonic vibration assisted laser beam oscillation welding (UV-LBOW) method was developed and applied on the butt-welding of Al-Mg alloy sheets. Due to the synergistic enhancement of the molten pool flow by ultrasound vibration and laser beam oscillation, the microstructure morphology of fusion zone (FZ) was comprised of equiaxed grains. Additionly, a uniform element distribution was generated from the boundary to the center of the FZ. An enhanced tensile strength of 347 MPa and a fraction elongation of 19.0 % were obtained due to the grain refinement and solid solution strengthening effects.

Aluminum oxide phosphors were synthesized by solution combustion method using urea and glycine as fuel. XRD results show that the sample synthesized with urea as a fuel is $\alpha -A{l}_2{O}_3$ and glycine as a fuel is $\gamma -A{l}_2{O}_3$ with rhombohedral (R-3c) and cubic (Fd-3m) structures, respectively. The PL spectra of unirradiated and Ni⁷⁺ ions irradiated $\alpha -A{l}_2{O}_3$ show a broad peak between 1.92 and 3.2 eV with maxima at 2.25 eV. This broad emission is assigned to the combination of F₂ and $F_2^{2+}$ centers. In addition, two sharp emissions observed at 1.83 eV (678 nm) and 1.78 eV (695) are due to R-lines of Mn⁴⁺ and Cr³⁺ respectively. The PL intensity is enhanced after Ni⁷⁺ ion irradiation in $\alpha -A{l}_2{O}_3$ and the highest intensity is observed for 1 × 10¹² Ni⁷⁺ cm⁻². PL intensity decreases beyond this fluence. Unirradiated $\gamma -A{l}_2{O}_3$ samples have greater PL intensity, which decreases with Ni⁷⁺ ion irradiation. PL emissions of R-lines of Mn⁴⁺ and Cr³⁺ are missing in $\gamma -A{l}_2{O}_3$ due to a lower crystal field in the gamma phase.