High extinction-ratio microstructure fiber based on chalcogenide glasses

Extinction ratio (ER) is one of the important parameters to characterize the polarization-maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled-off extrusion method. The core and cladding material of the fiber are Ge₉As₂₃Se₆₈ and Ge₁₀As₂₂Se₆₈. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid-infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18-cm-long PM fiber for the first time.     

Analysis of layer splitting in x and z-cut KTiOPO4 implanted by H+ ions

H⁺ ions with various fluences are implanted into x and z-cut KTP crystals to achieve KTP film. Post-implantation annealing under different temperature is imposed on the samples to induce layer splitting and surface morphology modification. Layer exfoliation is observed in freestanding z-cut samples. Layer splitting is obtained using bonding method in x-cut sample implanted with 117 keV H⁺ ions at ion fluence of 6 × 10¹⁶ ions/cm². Optical microscopy, scanning electron microscope and atomic force microscopy are used to observe splitting phenomenon. Rutherford backscattering spectroscopy/channeling method is employed to measure lattice damage and to investigate the relationship between implantation-induced defects and layer splitting.     

A tetranuclear nickel(II) complex for water oxidation: Meeting new challenges

Ni complexes are promising catalysts for water splitting. Herein, a tetranuclear nickel(II) complex with bis-[(E)-N′-(1-(pyridin-2-yl)ethylidene)]carbohydrazide (HL), was synthesized and characterized by spectroscopic methods and single crystal X-ray analysis. The complex is a tetranuclear complex and the ligands are coordinated to the metal ions in the mono-negative form, (L)^- to form a tetranuclear [NiL]₄⁴⁺ unit. Each Ni(II) ion is six-coordinated by pyridine nitrogen, azomethine nitrogen and oxygen atoms of two perpendicular carbohydrazone ligands in the mer configuration. The complex was studied as a water-oxidizing catalyst. In the next step, the role of the Ni-based compound for water oxidation on the surface of fluorine doped tin oxide as one of the true catalysts was investigated by scanning transmission electron microscopy, scanning transmission electron microscopy, spectroelectrochemistry, and electrochemistry. The electrode after water oxidation by the complex was studied and a relation between the decomposition of the Ni complex and water-oxidation reaction was proposed. The experiments show that under water-oxidation condition in the presence of the complex, a Ni-based compound on the electrode is a candidate as a contributor to the observed catalysis.     

Luminescence and energy transfer of color-tunable Lu_2MgAl_4SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+) phosphors

Energy transfer among the co-doped activators is an efficient route to achieve color-tunable emission in inorganic phosphors.Herein,photoluminescence tuning from blue to cyan has been achieved in the Lu_2MgAl_4 SiO_(12);Eu~(2+),Ce~(3+)phosphors by varying the Ce~(3+) concentration with a fixed Eu~(2+)content.With the further introduction of a Mn~(2+)-Si4+couple into the host lattice,the emission color can be tuned to red through the energy transfer of Eu~(2+)and Mn~(2+).The luminescence properties and the energy transfer mechanism were studied in detail.The energy transfer from Eu~(2+)to Ce~(3+)is certified as a dipolequadrupole interaction with the energy transfer efficiency of 41.4% and Eu~(2+)to Mn~(2+)belongs to a dipole-dipole interaction with the energy transfer efficiency of 94.3%.The results imply that this singlephased Lu_2MgAl4 SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+)phosphor has a potential prospect for application in near-UV chip pumped white light emitting diodes.     

Galvanic corrosion of carbon steel coupled to antimony

Galvanic corrosion of carbon steel coupled to antimony was studied in aerated and N₂-purged electrolytes at ambient and 60 °C temperatures. Free corrosion potential of antimony and carbon steel shifts to more active values with increasing temperature and N₂ purging of the electrolyte. Under all experimental conditions, antimony remains less electronegative than carbon steels. Aeration and temperature affect potentiodynamic behaviour of both materials. As a consequence, the corrosion current for the antimony–carbon steel couple increases with increasing temperature and with aeration. There was a good agreement between the corrosion currents obtained through the Evans’ experiment and super-imposed potentiodynamic scans.     

Structural,elastic, and thermodynamic properties of ZnSexTe1−x: A first-principles study

The structural, elastic, and thermodynamic properties, as well as optical bowing parameters of ZnSe_xTe_1?x ternary alloys are investigated. We adopt the Landau–Lifshitz structural models using the first-principles method, and show that alloys of different structures but identical compositions exhibit highly similar parameters. Results also reveal that the structural relaxation effect plays a crucial role in the gap bowing parameter. The different constituents of the alloys are all mechanically stable. However, they exhibit phase separation at low temperatures because of thermodynamic reasons. The calculated phase diagram shows the temperature at which a stable alloy may be formed for the different compositions of Se. It also demonstrates that the lowest temperature indicating the thermodynamic stability of alloys over the whole composition range (the critical temperature) is about 757 K.     

Luminescence properties of Eu3+ or Dy3+/Au co-doped SiO2 nanoparticles

Silica nanoparticles, prepared by the Stober method, have been doped with Eu³⁺, Dy³⁺, or processed to result in Au nanoparticles on the silica surface. The luminescence of the rare earth (RE)-doped SiO₂ particles has been studied as a function of the nature of the RE, their concentration and also of the presence of Au nanoparticles at the surface of the SiO₂ nanoparticles. We have shown that the Eu³⁺ emission is observable over the experimental conditions examined, whereas it was not possible to observe any emission for Dy³⁺ doped materials. No enhancement of the Eu³⁺ emission was observed following the adsorption of gold nanoparticles at the surface of the SiO₂ nanoparticle, however an excitation at 250 nm leads to both the emission of the matrix and Eu³⁺ showing an energy transfer from the SiO₂ matrix to Eu³⁺ ions.     

Effect of the slurry composition on the piezoelectric properties of PZT ceramics fabricated via materials extrusion 3D printing

Herein, the effect of the binder content in lead zirconate titanate (PZT) slurry has been systematically studied to improve the piezoelectric properties of PZT ceramics prepared via material extrusion 3D printing. For smooth printing, a slurry with a binder concentration ranging from 6 to 12 wt% was proposed. The porosity of the green body first decreased and then increased with an increase in the binder concentration, and the minimum porosity was obtained when the binder concentration reached 10 wt%. Samples with increased density were obtained after debinding and lead-rich atmosphere sintering. PZT piezoceramics fabricated using a binder content of 10 wt% exhibit the maximum relative density (96.9%), largest piezoelectric constant (342.6 pC/N) and dielectric constant (1621). Based on the above process, the wood pile structure and helical twentytetrahedral structural components were successfully fabricated using the material extrusion process. This research lays the foundation for the engineering application of 3D printing to fabricate high-performance piezoceramics with complex shapes.     

Study on thermal shock resistance of Sc2O3 and Y2O3 co-stabilized ZrO2 thermal barrier coatings

In order to reveal the effect of Sc₂O₃ and Y₂O₃ co-doping system on the thermal shock resistance of ZrO₂ thermal barrier coatings, Y₂O₃ stabilized ZrO₂ thermal barrier coatings (YSZ TBCs) and Sc₂O₃–Y₂O₃ co-stabilized ZrO₂ thermal barrier coatings (ScYSZ TBCs) were prepared by atmospheric plasma spraying technology. The surface and cross-section micromorphologies of YSZ ceramic coating and ScYSZ ceramic coatings were compared, and their phase composition before and after heat treatment at 1200 °C was analyzed. Whereupon, the thermal shock experiment of the two TBCs at 1100 °C was carried out. The results show that the micromorphologies of YSZ ceramic coating and ScYSZ ceramic coating were not much different, but the porosity of the latter was slightly higher. Before heat treatment, the phase composition of both YSZ ceramic coating and ScYSZ ceramic coating was a single T′ phase. After heat treatment, the phase composition of YSZ ceramic coating was a mixture of M phase, T phase, and C phase, while that of ScYSZ ceramic coating was still a single T′ phase, indicating ScYSZ ceramic coating had better T′ phase stability, which could be attributed to the co-doping system of Sc₂O₃ and Y₂O₃ facilitated the formation of defect clusters. In the thermal shock experiment, the thermal shock life of YSZ TBCs was 310 times, while that of ScYSZ TBCs was 370 times, indicating the latter had better thermal shock resistance. The difference in thermal shock resistance could be attributed to the different sintering resistance of ceramic coatings and the different growth rates of thermally grown oxide in the two TBCs. Furthermore, the thermal shock failure modes of YSZ TBCs and ScYSZ TBCs were different, the former was delamination, while the latter was delamination and shallow spallation.