Effect of Relative Humidity on the Thickness of Assembled Silica Colloidal Crystal Films

In order for the colloidal crystal films to be better applied, the influence of relative humidity on the preparation of silica colloidal crystal (SCC) films was systematically studied to solve the problem of different thicknesses of SCC films prepared by different batches under the conditions with the same temperature, concentration of suspension and diameter of the particles. SCC films with 190 nm particles were prepared by static vertical deposition method under different humidity regulated by saturated salt solutions, and the thickness of the films was obtained by an interferometric method. The results showed that the increase in humidity would reduce the thickness of the prepared films, which was believed to be caused by the decrease in evaporation rate after the wetting film absorbs water vapor. A new formula for calculating film thickness was proposed and verified from a series of experiments. With the control of humidity, high-quality SCC films with controlled thickness can be repeatedly prepared.

Síntese e caracterização de esferas monodispersas de látex e sua utilização no preparo de filmes de cristais coloidais tridimensionais.

Polystyrene latex spheres were obtained by free-emulsifier polymerization of styrene. Suspension was characterized by Photon Correlation Spectroscopy (PCS) and Transmission Electron Microscopy (TEM) and were observed to be monodisperse with sizes around 463 nm. A vertical deposition method was used in order to prepare films deposited on glass slides from the spheres suspension. High-quality opal-like films were obtained and characterized by Reflectance Spectroscopy, Scanning Electron Microscopy (SEM) and Optical Microscopy.

Fabrication and Optical Properties of NiO-SiO2 Composite Photonic Crystals

NiO-SiO2 composite photonic crystals were fabricated by the self-assembly and the spin coating method. First, the SiO2 monodisperse colloidal spheres were fabricated by the Storber method and the opal structure was obtained by the vertical deposition method. After spin coating and sintering, the electrochromic material NiO was infiltrated in the opal template. The obtained NiO-SiO2 composite photonic crystal was characterized by X-ray diffraction (XRD), and the morphologies of SiO2 opals and the composite structures were characterized by SEM. The reflection spectra were measured and revealed that the periodic arrays exhibit a photonic band gap in the (111) direction.

Electrical Properties of Polycrystalline α-HgI2 Detector

Potentially low cost and large-area polycrystalline mercuric iodide (α-HgI2) is one of the preferred materials for the fabrication of room temperature X-ray and gamma-ray detectors. In this paper, polycrystalline α-HgI2 films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. X-ray diffraction (XRD), scan electron microscopes (SEM) and Raman spectrum were used to characterization the HgI2 films obtained, and I-V characteristics was also tested. Using the polycrystalline α-HgI2 films, we get the detector. According to the detector, on the one hand, a dark current test is made by using KEITHL EY 485 picoammeter; on the other hand, the Agilent 4294A precision impedance analyzer is taken to test the characteristic curve of its capacitor frequency.

Research on Thermal Stress of Slab Heating Process Based on Transient Non-Linear Analysis

Polycrystalline α-HgI2 films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. The influence of the α-HgI2 seed layers on the structural and electrical properties of the polycrystalline α-HgI2 films was investigated. It is found that the α-HgI2 seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI2 films.

Effect of Seed Layers Prepared by Vertical Deposition Method on the Growth and Properties of Oriented Polycrystalline α-HgI2 Films

Polycrystalline α-HgI2films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. The influence of the α-HgI2seed layers on the structural and electrical properties of the polycrystalline α-HgI2films was investigated. It is found that the α-HgI2seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI2films.

Fabrication and Optical Properties of Nb2O5 Inverse Opal Photonic Crystals by PS Opal Template

In this paper, polystyrene (PS) opals template, opal with a closed-packed face centered cubic (fcc) lattice, was prepared using vertical deposition method. The template provided void space for infiltration of Nb2O5 etc. PS colloidal nanospheres was face-centered-cubic (FCC) structure with its (111) planes parallel to the substrate. Finally, the transfer matrix method (TMM) was used to calculate photonic band-gap of PS opal and Nb2O5 inverse opal structure. The calculation results show that the photonic band-gap of Nb2O5 with inverse opal structure is wider than that of PS opals.

Modulation of Three Dimensional Photonic Band Gap in Visible Region

Three dimensional (3D) SiO2 photonic crystals films were fabricated on quartz substrate by vertical deposition method. The effects of various preparation parameters on optical properties were studied by optical transmission measurements. Bragg reflection on parallel sets of (111) planes were observed in all the samples. The center wavelength of [111] photonic band gap (PBG) varied from 450 nm to 680 nm with the increasing sphere size. For a given sphere size, the (111) Bragg reflection of as-deposited sample shifted towards lower wavelengths as the sintering temperature T increased. The role of evaporation temperature on the optical properties of the film was also investigated. The PBG can be correspondingly modulated in visible region by changing various preparation parameters.