Materials Letters: X最新文献

This letter examines the potential and challenges of using additive friction stir deposition for large-scale near-net-shaping of 7xxx Al alloys, particularly AA7075 and AA7050. Compared to fusion-based additive manufacturing, which is unable to print these alloys without feedstock modification or composition change, additive friction stir deposition is an emerging solid-state additive process with a thermomechanical processing nature that can render fully-dense AA7075 and AA7050 in the as-deposited state. More importantly, wrought-like tensile properties have been demonstrated in the deposited AA7075 based on the original composition. The process is well-suited for large-scale printing due to its high build rate and scalability. Significant challenges nevertheless exist in process and post-process control, in addition to the impurity from lubrication.

In this report, we present a comprehensive explanation of the luminescent features of Dy³⁺-ions doped Zinc Sodium Lead Borate (ZnNaPbB) glasses through various characterizations like UV–Vis-NIR, absorption and emission spectroscopy. The absorption spectra were used to determine the optical bandgap (E_opt) and Urbach energy (ΔE). The emission spectra are dominated by three peaks (strong yellow, blue and weak red) in the visible range at 481 nm, 575 nm and 664 nm. The CIE coordinates lie in the pure white region of the chromaticity diagram indicating that the as-prepared glasses have possible applications for optoelectronic devices.

Borate glass doped with Praseodymium (Pr³⁺) having different concentration were synthesized via melt quenching method. The density of the glass is proven to enhance with the abundance of the Pr³⁺ ions resulting in structural compactness of the glass. Variation of the dielectric constant, reflection loss, molar refraction and polaron radius has been analyzed with the concentration of Pr³⁺ ions. Absorption spectra were recorded in the range of 200 nm-1800 nm and seven peaks were observed. Band gap is evaluated using Tauc plot. Absorption spectra are used to assess the bonding parameter and Judd-Ofelt intensity parameter. The results of the Judd Ofelt theory are consistent with the bonding parameters. Variation of the Urbach energy with the band gap has been analyzed. The known result affirms the glasses potential as a green component in reddish orange luminescent devices.

Photoacoustic spectroscopy is an essential technique for material characterization by measuring acoustic noise inside a cell. In this work, we have fabricated a photoacoustic cell and a pre-amplifier circuit and optimized both for maximum sensitivity. The cavity volume is measured ∼4.90 × 10⁻⁶ m³ at optimum condition. After that, the thermal diffusivity of undoped ytterbium oxide is measured by recording photoacoustic voltages. It is found 42.22–44.90 mm²/s for the excitation pump power 150–300 mW range by 980 nm diode laser source.

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 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.

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.

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.