Perovskite-type AlFeO3 powders are synthesized by a modified polyacrylamide gel route using different chelating agents at different pHs. X-ray diffraction and Raman results indicate that the AlFeO3 powders synthesized with oxalic acid are rhombohedral structure, while the AlFeO3 powders fabricated by using the other chelating agents exhibit an orthorhombic structure. The scanning electron microscopic images indicate that the morphology of the AlFeO3 samples depend on the choice of chelating agent and pH value. In addition, the particle size of samples with rhombohedral structure is larger than that of the samples with orthorhombic structure. X-ray photoelectron spectroscopy and scanning electron microscopic analysis indicate that the AlFeO3 powders fabricated at pH = 7 have good phase purity and uniform size. Photocatalytic activities of the AlFeO3 samples are determined by the degradation of rhodamine B dye in the presence of hydrogen peroxide and the results show that the samples will probably be applicable in the development of highly efficient photocatalyst. In addition, the rhombohedral AlFeO3 samples exhibit better photocatalysis than the orthorhombic samples, which is probably because that the crystal structure of AlFeO3 samples play a more important role than particle size in photocatalytic activity. The as-prepared AlFeO3 photocatalyst exhibits a pronounced photocatalytic activity for the decomposition of rhodamine B under visible-light irradiation, which is expected to widen the potential applications for perovskite-type oxide AlFeO3.A novel perovskite-type photocatalyst AlFeO3 is synthesized by a modified polyacrylamide gel route using different chelating agents. The crystal structure of AlFeO3 sample depend on the choice of chelating agent and AlFeO3 photocatalyst, in the presence of hydrogen peroxide, exhibit a pronounced photocatalytic activity for the decomposition of rhodamine B under simulated sunlight.Open image in new window

In order to achieve paper-like spin devices, it is rather critical to develop new two-dimensional (2D) spin materials. In this study, the geometrical structure, stability, and electronic and magnetic properties of 2D nickel dihalides of NiX2 (X = Cl and Br) type were investigated using density functional theory (DFT) calculations. We found that after optimization, geometries of NiCl2 and NiBr2 sheets that are obtained from their bulk counterparts are well kept. Phonon dispersion calculations demonstrated that both NiCl2 and NiBr2 sheets are dynamically stable. Magnetism calculations showed that ferromagnetic (FM) coupling is ground state for both structures in which per NiCl2 and NiBr2 unit cells can possess the moments of 1.91 and 1.88 μB, respectively. Density of states (DOS) and band structure calculations revealed that both structures are magnetic semiconductors with large band gaps. In addition, strain effect also showed that the moments of NiCl2 and NiBr2 sheets can be effectively tuned by applying the biaxial strain. A unique combination of integrated geometry, dynamical stability, intrinsic ferromagnetism, a magnetic semiconductor and tunable magnetism makes NiCl2 and NiBr2 sheets promising candidates for next-generation paper-like spin devices.

The electronic and magnetic properties of different arsenene nanoribbon (As NR) structures were investigated systematically using the density functional theory (DFT) method. Our results reveal that the nanoribbons' geometrical structure and chemical termination have significant impacts on their electronic and magnetic properties. Specifically, the unpassivated armchair nanoribbons (a-NRs) and reconstructed zigzag nanoribbons (zz-o-RNs) are nonmagnetic indirect and direct bandgap semiconductors, respectively. Considering the magnetic interaction between the edge states, the normal and one-atom terminated zigzag nanoribbons (z-NRs) are determined to be a weak antiferromagnetic (AFM) semiconductor. H passivation at the edge sites results in nonmagnetic and semiconducting properties of a-NRs, z-NRs, and zz-o-NRs. External strain has significant effects on both the band gap and the orbital characteristics of the band edge of a-NRs, zz-o-NRs and H passivated z-NRs, owing to the competition between the As px, py, and pz bonding/anti-bonding states. For the bare z-NRs, the tensile strain stabilizes the AFM state with enhanced magnetic moments. These versatile electronic and magnetic properties suggest possible potential of the As NRs for application in nanoelectronic devices.

•The optical performances of contaminated fused silica were investigated.•The photo-thermal absorption of the contaminated layer was investigated.•The light intensity modulation is numerically calculated.•The damage mechanism was discussed.The influence of oil contamination on the optical performance of fused silica and laser induced damage threshold (LIDT) at 355 nm is studied. The liquid vacuum oil is artificially spun on the fused silica surface. Optical microscopy and ultraviolet–visible (UV–vis) spectrophotometer are used to identify and understand the potential influence of oil contamination on the optical performance of fused silica. The results show that a large number of oil droplets are observed on the surface of fused silica after spin-coating, and the transmissivity of fused silica decreases with the increasing oil quantity. The LIDTs of fused silica decrease with the increasing oil mass for both on input and output surfaces at 355 nm, and the LIDT of fused silica with oil on input surface is lower than that on output surface at same contamination level. The damage mechanisms are also discussed by the photo-thermal measurement and three dimensional finite difference time domain (3D-FDTD) method. The experimental and simulated results show that the electric-field modulation by oil droplets, rather than its photo-thermal absorption, is mainly responsible for the oil contamination induced laser damage of fused silica.

The (0 0 0 1) sapphire samples are irradiated with 60 keV helium ions at the fluences of 5 × 1016, 1 × 1017and 5 × 1017 ions/cm2 at room temperature. After implantation, two broad absorption bands at 320–460 and 480–700 nm are observed and their intensities increase with the increasing ion fluence. The grazing incidence X-ray diffraction results indicate that the {0 0 0 1} diffraction peaks of sapphire decrease and broaden due to the disorientation of the generated crystallites after ion irradiation. The microstructure evolution is examined by the scanning and transmission electron microscopes. The surface becomes rough because of the aggregation of helium bubbles and migration towards the surface. There is a lattice expansion up to ∼4.5% in the implanted area and the lattice distortion measured from dispersion of (1 1 0) diffraction is ∼4.6°. Such strain of crystal lattice is rather large and leads to contrast fluctuation at scale of 1–2 nm (the bubble size). The laser induced damage threshold (LIDT) is investigated to understand the effect of helium ion beam irradiation on the laser damage resistance of sapphire components and the results show that the LIDT decreases from 5.4 to 2.5 J/cm2 due to the absorptive color centers, helium bubbles and defects induced by helium ion implantation. The laser damage morphologies of samples before and after ion implantation are also presented.

This work demonstrates the synthesis of porous monolithic α-alumina by a modified polyacrylamide gel route at different reaction parameters. Various Al2O3 phases are synthesized by a modified polyacrylamide gel route using different organic additives and solutions with different pH values (3, 7, and 11). After calcination at 1150 °C, the pure α-Al2O3 is obtained at pH = 3 and 7 while there is still θ-Al2O3 at pH = 11. The organic additive has nothing to do with the purity of α-Al2O3phase. The scanning electron microscopic images indicate that the pore size and morphology of the samples depend on the choice of organic additive and pH value. The photoluminescence spectra show that two emission peaks located at 330 and 368 nm are observed when the excitation wavelength is 228 nm. Interestingly, the intensity of emission peak at 368 nm decreases with the decrease of full width at half-maximum or pore size.

A 10.6 μm CO2 laser has been reported to effectively mitigate the laser damage growth of fused silica. Two zones of the laser irradiated area are defined in this work: the distorted zone and the laser affected zone. The parameters of the two zones are studied at different CO2 laser beam sizes, irradiation times, and powers by microscopy, profilometry, and photoelastic method. The results show that the diameter of laser affected zone is almost completely determined by the laser beam size and the distorted zone is associated with the mitigation range of CO2 laser beam. The diameter and depth of the distorted zone increase as the laser power and irradiation time increase. The depth grows exponentially depending on the irradiation time. The maximum residual stress discrepancy is located near the boundary of the laser affected zone. The laser damage resistance test results show that the distorted zone and the laser affected zone have a better damage resistance than the original substrate.

Two-dimensional reduced graphene oxides (RGO) decorated with well-dispersed Ni nanoparticles were facilely fabricated via low temperature annealing of Ni(OH)2/Graphene composites in flowing H2. Ni@Graphene core-shell nanostructures were obtained following a self-catalyzed growth mechanism. The kinetic epitaxial growth of RGO layers on Ni(111) facets originates from annealing-driving phase transition from NiO to Ni at temperature ≥ 450 °C, which was revealed by utilizing comprehensive characterizations including X-ray diffraction, X-ray photoelectron spectroscopy, as well as aberration-corrected scanning transmission electron microscopy. This distinct core-shell structure shows extraordinary catalytic activity in reduction of 4-nitrophenol with the efficiency reaching up to 45.0 L g−1 min−1 at room temperature. Atom-resolved microscopy evidences disclose that such outstanding catalytic activity could be attributed to the synergetic cooperation between Ni phase and epitaxial graphene shell. This work provides general inspiration on the facile fabrication of highly active and non-noble metal-graphene catalysts.