Optical Quartz Research Articles

Role of catalyst carriers in CO2 photoreduction over nanocrystalline nickel loaded TiO2-based photocatalysts

Nickel-based TiO2 photocatalysts were immobilized onto carriers (quartz plates and monoliths) in a unique reactor configuration to provide a high ratio of illuminated surface area of catalyst for the reduction in CO2 to fuels under UV and visible light. The incorporation of Ni2+ in the TiO2 matrix inhibits the grain growth of anatase crystallites and suppresses phase transformation. The Ni2+ atom is also found to be replacing some of the Ti atoms in the crystal lattice of TiO2 during the sol–gel method, thus causing a change in optical absorption. Using water as a reductant, vapour-phase CO2 was reduced to fuels with the monolith threaded with optical fibres and quartz plate photoreactor system following 4h of light irradiation. More importantly, the improved conversion efficiency is ascribed to the presence of Ni2+ species which served as electrons traps that suppressed recombination, resulting in effective charge separation and CO2 reduction.

The structural and electrical properties of GDC10 thin films formed by e-beam technique

Gadolinium doped cerium (GDC10) thin film ceramics were prepared by evaporating Gd 0.1 Ce 0.9 O 1.95 powder, using an e-beam evaporation technique. The initial powder of GDC10, with different surface areas (BET: 6.44, 36.2, 201 m 2 /g), were used to prepare thin ceramic films. The GDC10 thin ceramic films (thickness ~ 1.4 μm) were formed on optical quartz substrate (substrate geometry 2.5 × 2.5 cm). The formed GDC10 thin ceramic films structural properties were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical properties of the samples were investigated with an AC impedance spectroscopy in the temperature range 473–873 K and frequency range 10 − 1 –10 6 Hz. The formed GDC10 thin films repeat the crystallographic orientation of evaporated powder and do not depend on the initial powder grain size and deposition rate. It was determined that crystallite size has an influence on conductivity and diffusion coefficient. The ionic conductivity and activation energy depends on crystallite size. The best ionic conductivity and the lowest activation energy are 9.00 · 10 − 1 S/m and 1.13 eV, respectively. The activation energy varies from 1.19 to 1.29 eV, and depends on crystallite size, too. • Formed GDC10 thin films repeat crystallographic orientation of evaporated powder. • Crystallite size and texture coefficient of thin films depends on powders BET and deposition rate. • Ionic conductivity and activation energy decreases decreasing crystallite size. • Ionic conductivity and relaxation frequency depends on evaporated initials powders BET. • Charge carrier concentration depends on the deposition rate and evaporated powders BET.

Correlation between phase and optical properties of yttrium-doped hafnium oxide nanocrystalline thin films

Yttrium-doped hafnium oxide (YDH) nanocrystalline films were produced by sputter-deposition at a substrate temperature of 400°C. The deposition was made onto Si (100) and optical grade quartz substrates with variable deposition time to produce YDH films in a wide range of thickness, dYDH∼25nm to 1.1μm. The effect of dYDH on the crystal structure, surface/interface morphology and optical properties of YDH films was investigated. X-ray diffraction analyses revealed the formation of monoclinic phase for relatively thin films (<150nm). The evolution towards stabilized cubic phase with increasing dYDH is observed. The scanning electron microscopy results indicate the dense, columnar structure of YDH films as a function of dYDH. Spectrophotometry analyses indicate that the grown YDH films are transparent. The band gap was found to be ∼5.60eV for monoclinic YDH films while distinct separation and an increase in band gap to ∼6.03eV is evident with increasing dYDH and formation cubic YDH films. A correlation between growth conditions, phase evolution, and optical properties of the YDH nanocrystalline films is established.

Experimental visualization of sliding bubble dynamics in a vertical narrow rectangular channel

Visual investigation on sliding bubble dynamics in a narrow rectangular channel was carried out in this paper, and the flow direction was vertically upward with deionized water as working fluid. The test section mainly consists of a polyethylene block, optical quartz glass, heating plate and other auxiliary components. The cross section of the narrow rectangular channel is 2mm×8mm, and it was fabricated in an optical quartz glass for observation of the sliding bubble dynamics from the wide side and the gap side of the narrow rectangular channel using a high speed digital camera. The results from the present experimental study show that bubbles always slide along the heating surface after departing from the nucleation sites, and the sliding bubble diameter increases during the sliding process. The phenomenon on bubble lift-off from the heating surface is not observed with low heat flux in the isolated bubble region. What is more, the sliding bubble is spherical according to the observation from the wide side of the channel, but it is elongated in the direction normal to the heating surface according to the observation from the gap side of the channel. During the process of bubble sliding along the surface, the upstream and downstream contact angles are almost equal. It is also found that there is an increase in sliding velocity at the initial moment, and the increase in sliding velocity decreases gradually as the time increases, and the sliding velocity reaches a constant one finally. The sliding bubble velocity is less than that of local liquid velocity on the streamline through the mass center of the bubble at the initial moment. However, it will exceed the local liquid velocity with increasing time, and the shear lift force acting on the sliding bubble pushes the bubble against the heating surface in this case, which is mainly the reason for bubble sliding along the heating surface.

Precise measurement of a magnetic field generated by the electromagnetic flux compression technique

The precision of the values of a magnetic field generated by electromagnetic flux compression was investigated in ultra-high magnetic fields of up to 700 T. In an attempt to calibrate the magnetic field measured by pickup coils, precise Faraday rotation (FR) measurements were conducted on optical (quartz and crown) glasses. A discernible "turn-around" phenomenon was observed in the FR signal as well as the pickup coils before the end of a liner implosion. We found that the magnetic field measured by pickup coils should be corrected by taking into account the high-frequency response of the signal transmission line. Near the peak magnetic field, however, the pickup coils failed to provide reliable values, leaving the FR measurement as the only method to precisely measure extremely high magnetic fields.

Synthesis, crystal structure and thin-film-optical properties of 3-amino-2-(2-nitrophenyl)diazinyl-3-(morpholin-1-yl)acrylonitrile

3-Amino-2-(2-nitrophenyl)diazinyl-3-(morpholin-1-yl)acrylonitrile (ANMA) has been successfully synthesized via conventional solvent method, and its molecular structure has been identified by using various techniques including FTIR, 1H NMR, MS and elemental analysis. The crystal structure of ANMA is characterized by single crystal X-ray crystallography. Crystallographic data revealed that the spatial structure of ANMA belongs to monoclinic, P21 a space group. ANMA thin films were deposited onto optical flat quartz substrates by using thermal evaporation under vacuum pressure of 2×10−4Pa. The optical properties of the films are studied in terms of the measurements of transmittance and reflectance determined at the normal incident of light over the spectral range 200–2400nm. The absorption coefficient of the films is computed and the optical band gap of the films is estimated. In addition, the complex refractive index for the films has been calculated and described. Single oscillator model is found to be applicable for the films in which the dispersion parameters namely; single oscillator energy, dispersion energy, dielectric constant at high frequency, lattice dielectric constant and the ratio of carrier concentration to the effective mass are estimated.

Sedimentation and precipitation of nanoparticles in power-law fluids

Our experiment reported here adopts water, alcohol (100 %), carboxymethyl cellulose (CMC) aqueous solution with different concentrations as the base-fluid of nano-fluids. We show diffusion, aggregation and precipitation of nano-size particles in the optical quartz glass Petri dishes filled with nano-fluids flat with the help of a rotating cone. The experimental results illustrate that nanoparticles are preferably suspended in CMC aqueous solution than in water or alcohol, which means the effective Hamaker constant of water- or alcohol-particle suspensions is bigger than that of CMC-particle suspension. In the experiment with CMC as the base solution, increasing the viscosity of the solution can alleviate the settling velocity of particles and make the suspension better. The experiment also discovers that in static condition, the mutual attractive force between nanoparticles plays an important role in the suspension; however, if external forces, which are higher than the attraction, exist, they are decisive parts. In addition, Al2O3 solution is much more sensitive than the Cu solution with the varying concentration and status in the experiment because the density of Al2O3 particles is smaller than that of Cu-nanoparticles.

Spectroscopic study of Pu(IV) oxidation to Pu(VI) in 3 mol/dm3nitric acid at 373 K

AbstractOptical absorption spectra of Pu(IV) in 3 mol/dm3(M) nitric acid at 373 K were measured using an optical quartz cell equipped with a thin-film heater. Pu(IV) was oxidized to Pu(VI) by heating at 373 K, and the concentrations of Pu(IV) and Pu(VI) gradually decreased and increased, respectively, with the heating time. The ratio of Pu(IV) oxidized to Pu(VI) was 37% at a heating time of 394 min, and no Pu(III) or Pu(V) characteristic peaks were observed throughout the experiment. The oxidation rate of Pu(IV) in 3 M nitric acid at 373 K could be described by the equation-d [Pu(IV)]t/d t= k′1[Pu(IV)]t-k′2[Pu(VI)]t, where[Pu(IV)]tand[Pu(VI)]twere the concentrations of Pu(IV) and Pu(VI) at a heating time of t min. The apparent rate constants for Pu(IV) oxidation (k′1) and Pu(VI) reduction (k′2) at 373 K were calculated to be 2.3 × 103 min-1and 3.4 × 103 min-1, respectively.

Experimental application of pulsed laser‐induced water jet for endoscopic submucosal dissection: Mechanical investigation and preliminary experiment in swine

A current drawback of endoscopic submucosal dissection (ESD) for early-stage gastrointestinal tumors is the lack of instruments that can safely assist with this procedure. We have developed a pulsed jet device that can be incorporated into a gastrointestinal endoscope. Here, we investigated the mechanical profile of the pulsed jet device and demonstrated the usefulness of this instrument in esophageal ESD in swine. The device comprises a 5-Fr catheter, a 14-mm long stainless steel tube for generating the pulsed water jet, a nozzle and an optical quartz fiber. The pulsed water jet was generated at pulse rates of 3 Hz by irradiating the physiological saline (4°C) within the stainless steel tube with an holmium-doped yttrium-aluminum-garnet (Ho:YAG) laser at 1.1 J/pulse. Mechanical characteristics were evaluated using a force meter. The device was used only for the part of submucosal dissection in the swine ESD model. Tissues removed using the pulsed jet device and a conventional electrocautery device, and the esophagus, were histologically examined to assess thermal damage. The peak impact force was observed at a stand-off distance of 40 mm (1.1 J/pulse). ESD using the pulsed jet device was successful, as the tissue specimens showed precise dissection of the submucosal layer. The extent of thermal injury was significantly lower in the dissected bed using the pulsed jet device. The results showed that the present endoscopic pulsed jet system is a useful alternative for a safe ESD with minimum tissue injury.

Quasi-achromatic superresolving phase only pupil filters

Reported in this paper is a new design of the quasi-achromatic phase-only superresolving pupil filters (QAPSFs) relatively independent of wavelength based on the zero order Bessel function of the first kind. The effect of design parameters of the new filters on the superresolving performance parameters such as the normalized spot size (G) and the Strehl ratio (S) is discussed and analyzed in detail. As an example, the performance parameters of QAPSFs made of optical quartz glass are simulated and compared with phase only pupil filters, which indicate that this kind of filters is less independent of wavelength in the range from 300nm to 589nm for superresolution, and a high Strehl ratio is also obtained. The equivalent performance parameters are derived to characterize the superresolution performance of the quasi-achromatic filter.

Quantitative analysis of trivalent uranium and lanthanides in a molten chloride by absorption spectrophotometry

As an analytical application for pyrochemical reprocessing using molten salts, quantitative analysis of uranium and lanthanides by UV/Vis/NIR absorption spectrophotometry was performed. Electronic absorption spectra of LiCl–KCl eutectic at 773 K including trivalent uranium and eight rare earth elements (Y, La, Ce, Pr, Nd, Sm, Eu, and Gd as fission product elements) were measured in the wavenumber region of 4,500–33,000 cm−1. The composition of the solutes was simulated for a reductive extraction condition in a pyroreprocessing process for spent nuclear fuels, that is, about 2 wt% U and 0.1–2 wt% rare earth elements. Since U(III) possesses strong absorption bands due to f–d transitions, an optical quartz cell with short light path length of 1 mm was adopted in the analysis. The quantitative analysis of trivalent U, Nd, Pr, and Sm was possible with their f–f transition intensities in the NIR region. The analytical results agree with the prepared concentrations within 2σ experimental uncertainties.

Research on Removal Characteristic of the Optical Quartz with Atmospheric Pressure Plasma Jet

The Atmospheric Pressure Plasma Jet (APPJ) is an innovative technology in advanced optics manufacturing; it is a non-contact precision machining method based on the chemical reaction between a reactive neutral radical generated by the plasma and substrate surface atoms for atom-scale material removal. The APPJ involves a complicated process; therefore, the controllability of the technical process was investigated to describe the accuracy of machining efficiency that is the uniformity and repeatability for machining systems, the linearity relation between the removal rates and dwell time. Moreover, the experimental result of the fused quartz removal function variation trend with different processing parameters was discussed. The results of experimentation indicate that the APPJ method has good repeatability within a short dwell time, the removal depth increases with the dwell time and a linearity relation seems appropriate, and the radio frequency (RF) power and the flux of assistant gas oxygen have a great influence on removal efficiency. However, the removal rate remains stable under small perturbation of flux of plasma gas He and reactive gas SF6. And the surface roughness is improved from Ra 9.3nm to Ra 3.7nm.

Synthesis of poly-p-xylylene + CdS nanocomposites and studing of their surface structure

Thin-film polymeric nanocomposites based on a poly-p-xylylene matrix (PPX) and nanoparticles of cadmium sulfide (CdS) have been obtained using solid-phase cryochemical synthesis on optical quartz substrates. The optimal conditions for the formation of PPX + CdS nanostructured polymeric films have been determined. The topography and surface characteristics of PPX + CdS nanocomposites have been studied by scanning atomic force microscopy (AFM). The characteristics of the morphological and structural changes of the film surfaces have been found at different CdS nanoparticle concentrations. These changes point to a reorganization of the PPX + CdS polymeric matrix. It is shown that at 2–10 vol % CdS concentration, the elements of the surface’s structural organization are polymeric nanofibers, parallel to the substrate plane, and a small number of nanoglobules, locally positioned directly on the nanofiber surfaces. Ordering of the surface structure accompanied by the formation of a periodic surface relief in the shape of nanoglobules was observed at a CdS concentration of 13.5 vol %. A mechanism of the formation of nanostructured PPX + CdS films is proposed. Based on the AFM experimental data, one can assume that during co-condensation of a p-xylylene monomer, CdS nanoparticles initiate radical polymerization of the PPX matrix, when the substrate is heated from 77 K to 300 K. The type of surface structure (fibrillar, fibrillar + globular and globular) depends on the nanoparticle concentration in the polymeric matrix.

Photoresist modification by silver colloid solution: the role of silver nanoparticles content

The aim of this work was to investigate the influence of silver nanoparticles deposited from a colloid solution into a photoresist composition on the morphology and optical properties of the grating. The Ag colloid was produced by chemical reduc- tion of silver nitrate and incorporated in the photoresist composition by mixing. The film of Ag colloid solution modified photoresist was obtained by spin coating on an optical quartz substrate and dried at 100 °C for 20 min. The grating with a period of 4 µm was formed by contact lithography. The synthesized Ag nanoparticles were spherical or roughly spherical with diameters varying from 10 nm up to 60 nm. The content of Ag nanoparticles in the photoresist rose from 0.02 wt% to 4.66 wt% when the concentration of the Ag colloid solution increased from 10 to 30 wt%. Analysis performed with atomic force microscope and scanning electron microscope showed that Ag nanoparticles changed geometrical parameters and optical properties of the gratings: their height decreased and diffraction efficiency increased in all orders. However, the increase of the Ag content up to 4.66 wt% considerably changed the grating geometry. In this case the ridges of the grating became concave, probably due to the Ag nanoparticles light diffusion. For this reason secondary reflections appeared during photolithography and the ridge of grating is affected by exposure. Therefore the ridge surface becomes soluble to etching solvents, and exposure areas are removed.

Method for synthesizing optical quartz glass

A method for producing optical quartz glass by synthesizing monodisperse silica particles and centrifuging the particles followed supercritical drying and sintering of porous material is described. The optical transmission spectrum of the optical quartz glass produced by this method is compared with the spectra of several glasses obtained by commercial methods. The advantages of this method over methods based on silicon dioxide aerogels and xerogels for producing quartz glass are indicated.

Protein Encapsulation by Humic Substances

Protein encapsulation by natural organic matter is hypothesized to preserve the activity of proteins in terrestrial and aquatic environments. Direct molecular-level evidence for encapsulation of net positively charged proteins lysozyme, trypsin, and ribonuclease A by a diverse set of humic substances (HS) in nanostructured films was collected using a combination of optical waveguide lightmode spectroscopy and quartz crystal microbalance measurements. The results suggest that protein-HS electrostatic attraction drives encapsulation of positively charged lysozyme by a soil humic acid at pH 5 to 8 and by six additional humic and fulvic acids from terrestrial and mixed terrestrial aquatic sources at pH 5 and 6. Encapsulation of trypsin and ribonuclease A, which had negatively charged surface patches under the studied conditions, suggested that localized protein-HS electrostatic repulsion is overcompensated by attractive forces, likely including contributions from the hydrophobic effect. Evidence is provided showing that encapsulation of lysozyme at pH 8 and of ribonuclease A at pH 5 and 6 involved partial disassembly of HA supramolecular associations. This work advances a molecular-level picture of protein encapsulation by HS and presents a novel approach to study the effects of encapsulation on protein enzymatic activity and susceptibility to abiotic and biotic transformations.

A comparative study on comb electrodes devices made of MWPECVD diamond films grown on p-doped and intrinsic silicon substrate

Diamond is considered as a very promising material for the development of devices for radiation detection. Unlike other conventional photoconductive detectors diamond-based devices should provide high discrimination between UV and visible radiation. In this work we present the electro-optical properties of devices based on randomly oriented diamond films, synthesized in a microwave plasma enhanced chemical vapor deposition reactor. A comparative study on devices with coplanar interdigitated Cr/Au electrodes (with different interelectrode pitches) made of films grown simultaneously on intrinsic and p-doped silicon (100) substrates has been performed. The chemical–structural, morphological, electrical and optical properties of ROD films have been studied. In particular, the optical response has been measured in air using a Xe flash lamp coupled with an optical quartz fiber and a properly tailored front-end electronics based on a charge sensitive amplifier. Experimental results gave indications on how the device performances are dependent on the two types of employed substrates.

Humidity Detection by Using a Hybrid Sensor Employing Optical Waveguide Spectroscopy and Quartz Crystal Microbalance

Humidity Detection by Using a Hybrid Sensor Employing Optical Waveguide Spectroscopy and Quartz Crystal Microbalance

Development of a grinding–drilling technique for holing optical grade glass

This study presents the development of a grinding–drilling technique for an innovative bench-top drill that combines micro-EDM with grinding and drilling to fabricate micro-holes in optical grade glass. Firstly, a novel diamond-tool, made with copper-based sintered alloy, is designed and fabricated on-line into a harbor-shaped structure with a hollow shaft and negative back rake-angles. Constructed reverse co-centric micro-hole EDM-drilling and reverse w-EDM facilitate on-line machining of the diamond-tool, which can then be directly utilized to drill micro-holes in optical glass and quartz. Application of a load-cell that detects the drilling force in real-time, providing feedback for fine tuning the feed-rate of the tool is proposed. Experimental results show that excellent geometric and dimensional accuracy of micro-holes can be achieved. The estimated reasonable tool life is determined at a machining number of 30 times. The proposed grinding–drilling technique is simple, cost effective, and can significantly contribute to the precision micromachining industry.

The properties of scandium and cerium stabilized zirconium thin films formed by e-beam technique

Scandium and cerium stabilized zirconium (10Sc1CeSZ) thin ceramic films were formed evaporating (ZrO 2) 0.89(CeO 2) 0.01(Sc 2O 3) 0.10 micro powder using e-beam evaporation technique. The influence of deposition rate on formed thin films electrical properties and microstructure was studied. 10Sc1CeSZ thin films were deposited on two types of different substrates: optical quartz (SiO 2) and Alloy 600 (Fe–Ni–Cr). Deposition rate was changed from 2 to 16 Å/s to understand its influence on thin film formation and other properties. The formed 10Sc1CeSZ thin films keep the cubic crystal structure as the initial evaporated powder material but change the main crystallographic peak from (111) to (200) for both types of substrate and used deposition rates. It was determined that the crystallites size increases from 19.0 to 24.9 nm and from 15.6 to 19.9 nm on optical quartz and Alloy 600 respectively by increasing the deposition rate (in range from 2 to 16 Å/s). The thin film density decreases by increasing the deposition rate. The ionic conductivity of 10Sc1CeSZ thin films was determined by impedance spectroscopy in the frequency range from 0.1 Hz to 1.0 MHz in temperature range from 473 K to 873 K. The best ionic conductivity σ tot = 4.91 · 10 − 2 Sm − 1 at 873 K temperature and the lowest value of activation energy ΔE a = 0.88 eV were found for 10Sc1CeSZ thin films formed at 4 Å/s deposition rate.