Controllable synthesis of elongated hexagonal bipyramid shaped La(OH)<Subscript>3</Subscript> nanorods and the distribution of electric property by off-axis electron holography

Rare earth oxides/hydroxides are important emerging materials owing to their unique properties. Shape-controlled synthesis of elongated hexagonal bipyramid shaped La(OH)₃ nanorods with different aspect ratios and trigram-shaped LaCO₃OH nanosheets was systematically carried out by controlling the reaction conditions. Hydrazine and polyvinylpyrrolidone (PVP) surfactants used in synthesis are assumed to play a key “dual-template” role in determining the aspect ratio and shape of the resulting nanostructures. Elongated hexagonal bipyramid shaped La(OH)₃ nanorods were found to grow along the preferred orientation [0001]. Six equivalent crystallographic facets, \((20\bar 20)\), \((02\bar 20)\), \((2\bar 200)\), \((0\bar 220)\), \((\bar 2200)\), and \((\bar 2020)\) lattice planes, were found to be exposed on the side surfaces on each nanorod as confirmed by combined transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) analyses. A double-polarization phenomenon was found to occur at the nanorod surfaces by employing off-axis electron holography, implying that the material could be used as an effective dielectric microwave absorber. La(OH)₃ nanorods with larger aspect ratios exhibit better absorption properties with respect to the maximum reflection loss and effective absorbing bandwidth. Thus, a novel method towards the reasonable design of bipyramid shaped La(OH)₃ nanorods exhibiting tunable microwave absorption properties is proposed based on our synthesis strategy.

Open image in new window

     

Effect of different surface shapes formed by femtosecond laser on zirconia-resin cement shear bond strength

Objective: The purpose of this study was to evaluate the effect of different surface shapes formed by femtosecond (FS) laser on zirconia (Y-TZP)-resin cement shear bond strength (SBS). Background data: All ceramic restoration is used as an alternative to metal-ceramic restorations, due to its better aesthetics, strength, and toughness properties. However, bond strength of restoration to tooth and other materials is effective to long term success of the restoration, and to achieve it surface treatment is required on ceramic surface. Materials and methods: Forty square-shaped zirconia samples were prepared and assigned to four groups of 10. The details of the groups are as follows: Group A, square-shaped recessed surface; Group B, square-shaped projection surface; Group C, circular-shaped recessed surface; Group D, circular-shaped projection surface. The SBSs values were performed with a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed statistically using analysis of variance (ANOVA) and Tukey HSD multiple comparisons tests. Results: The one-way ANOVA results on SBSs of the zirconia material bonded with resin cement revealed significant differences among the groups (p < 0.05). The Tukey HSD test results revealed that Group B and D had significantly higher SBS values than other groups (p < 0.05), but there were no significant differences between each other (p > 0.05). Additionally, Group A and C had significantly lower values than other groups (p < 0.05). Conclusions: Different surface shapes formed by FS laser provided a significant increase in SBSs. The SBS values of projection surfaces of circular and square-shapes are greater than that of recessed surfaces of circular and square-shapes.     

An investigation on general corrosion and pitting of iron with the in-line digital holography

In the anodic processes of the iron electrode in both neutral and acidic solutions, general corrosion and pitting dynamical processes in the presence of chloride ions were observed in situ with the in-line digital holography. The dynamic processes such as formation and dissolution of the passive film, initiation and propagation of pitting have been studied. During the general corrosion, not only is the temporal structure in order, evidenced by the regular change of current with time, but also the spatial structure, indicated by the uniform fringes in the holograms at the electrode/electrolyte interface. However, during the pitting processes, the order of the spatial structure is destroyed, which is indicated by the wrinkled fringes in the holograms; the temporal order is broken as well evidenced by the irregular change of current with time. The experimental result shows that there is synergistic effect between H⁺ and Cl⁻ on both the initiation stage and the propagation stage. With the presence of chloride ions, pitting occurs much more easily in acidic solution than in neutral solution.     

Hot carrier relaxation in InP and GaAs on a subpicosecond time scale

Hot carrier relaxation in InP and GaAs is investigated in a comparative study using three different time resolved optical techniques. At carrier densities between 10¹⁷ to 10¹⁸ cm⁻³ in both materials the relaxation is strongly influenced by carrier-carrier-scattering. Internal thermalization of electrons and holes occurs on a femtosecond time scale comparable to the duration of the excitation. The temperatures of electrons and holes, however, remain different on a time scale of picoseconds.     

An electro-optic holography system with real-time arithmetic processing

This paper reports the use of a real-time arithmetic image processor in an electro-optic holography system. A speckle interferometer is used to combine an image of an object, lit by laser light, with a mutually coherent reference beam. A CCD TV camera detects the interference pattern, and the phase of the reference beam is advanced by 90° between frames. An image is generated from each set of four sequential TV frames by subtracting alternate frames, squaring, and adding the two results. The result is improved picture quality compared with the use of binary pixels and compared with electronic speckle pattern interferometry. Experimental results are shown.     

Dynamics of photoinduced motions in azobenzene grafted polybutadienes

The goal of the investigations was to measure the dynamics of photoinduced motions in semicrystalline polybutadiene backbone based polymer grafted with various degree of mesogenic thiols. We studied the influence of the grafting degree of the azobenzene-containing side groups and the length of terminal oxyaliphatic substituent in the side groups on the dynamics of the laser holographic volume and surface gratings recording. Measurements were performed in a typical laser degenerate two-wave mixing experiment, in which light self-diffraction efficiency during holographic recording was monitored. Mathematical model for grating formation based on coupling of three gratings has been assumed to elaborate the obtained results. Theoretical estimations and experimental results have shown very good agreement.     

Off-axis and inline electron holography: Experimental comparison

Electron holography is a very powerful technique for mapping static electric and magnetic potentials down to atomic resolution. While electron holography is commonly considered synonymous with its off-axis variant in the high energy electron microscopy community, inline electron holography is widely applied in low-energy electron microscopy, where the realization of the off-axis setup is still an experimental challenge. This paper demonstrates that both inline and off-axis holography may be used to recover amplitude and phase shift of the very same object, in our example latex spheres of 90 and 200 nm in diameter, producing very similar results, provided the object does not charge under the electron beam.     

Photopolymerizable glass with high refractive index species: Optical performance and emerging implementations

The properties of a photopolymerizable glass modified with high refractive index species incorporated at molecular level, including a wide range of spatial frequencies and the recording kinetics, are analyzed. Implementation of emerging applications is proposed. The article is published in the original.     

干燥对不同明胶的DCG全息图衍射效率影响的研究

通过自由干燥脱附除水法对几种不同明胶的ＤＣＧ全息图进行了干燥实验，结果发现干燥大幅度地增加了ＤＣＧ全息图的衍射效率。对衍射效率本来就较高的活性胶和改性胶的ＤＣＧ全息图来说，干燥后使其大多数的衍射效率都在８５％以上，有的甚至接近理想值１００％。但一般来说，在相同曝光量下，惰性胶的比活性胶的增加更多；对于同一明胶来说，一般是曝光量不足和曝光量过度的低衍射效率片比曝光量适度的高衍射效率片增加更多     

Contouring of Diffused Objects by Using Lensless Fourier Transform Digital Holography and Dual‐Index Immersion Method

Abstract: A simple method for contouring of diffused objects by using lensless Fourier transform digital holography and dual‐index immersion method is presented. It is noticed that to get more accurate results speckle noise should be eliminated/reduced from the reconstructed phase map from digital holograms. Speckle noise is handled by 5 × 5 median filtering. Depth contour interval up to a maximum of 0.12 mm could be achieved without making the interference phase fringes overcrowded.