Flat Quartz Plate Research Articles

A Conceptual Catalytic Receiver Reactor for Solar Thermal Sulfuric Acid Decomposition

The highest‐temperature step in iodine–sulfur and hybrid–sulfur thermochemical cycles for hydrogen generation is the sulfuric acid decomposition reaction. To efficiently utilize solar energy directly to operate this step, the development of a catalytic solar receiver reactor is essential. A cavity‐type reactor coupled to a solar dish and a numerical analysis of the reactor predicting the reaction conversion as a function of the solar absorption coefficient is presented in this study. The catalytic receiver reactor consists of a double‐walled quartz cylindrical tube to form the cavity and a flat quartz plate window for entry of the concentrated solar radiation. Two catalysts, Fe1.8Cr0.2O3 and Fe2O3/SiO2, are tested in the solar catalytic receiver reactor and SO2 yields of ≈40% and 38% are observed, respectively. Numerical analysis of the reactor is performed and a reaction conversion–absorption coefficient correlation is established. For the catalytic packed bed assuming absorption coefficient of 0.65, a steady‐state temperature of 1212 K is achieved, accomplishing an approximate theoretical efficiency of ≈56%. The numerical analysis suggests that by utilizing a material of construction with high absorption coefficient, significantly enhanced sulfuric acid decomposition can be achieved by the cavity‐type solar receiver reactor.

Effect of interactions on impingement heat transfer in odd and even element linear arrays of co-axial flames

Experimental and numerical study of linear arrays of co-axial flames impinging on a flat quartz plate have been performed and interactions and heat transfer characteristics are analyzed. High resolution inverse heat conduction procedure (IHCP) has been employed for determining local heat flux distribution. Strong interactions developed amidst adjacent flames led to asymmetric interactions. Combustion simulations revealed differences in the flow structures of four and five element arrays. Asymmetric interactions resulted in bending of all of the inner flames in four element array whereas central inner flame remains undeflected in five element array. Same has also been observed for six and seven element arrays too. Tilted columnar flows have been identified in even as well as odd numbered linear array of co-axial flames. These tilted flow structures resulted in distortion of recirculation zones (RCZ) of all the flames. Impingement heat flux contours are studied for various impingement spacings (H/Dh = 3, 5 and 7). At smallest impingement spacing, these contour maps revealed footprints corresponding to central inner flame due to symmetrical interactions. Thermal efficiency and heat transfer uniformity of four element array has been observed to be higher than five element array at all impingement spacings.

Surface Structures of Cosmetic Standard Poly Methyl Methacrylate UV Evaluation Plates and their Influence on the in vitro Evaluation of UV Protection Abilities of Cosmetic Sunscreens.

Cosmetic standard poly methyl methacrylate (PMMA) UV evaluation plates, i.e., roughened PMMA plates, are used in the EU and the US for the in vitro evaluation of UV protection abilities of sunscreen, such as in vitro UVA-PF and critical wavelength for the Broad-spectrum approval. In our previous studies, inhomogeneity in the thickness of a pseudo-sunscreen layer applied on a flat quartz plate was observed to alter UV transmission. Thus, the surface roughness of the standard plates should have a significant influence on the in vitro evaluation. In the present study, we have analyzed the surface structures of three cosmetic standard PMMA UV evaluation plates: Helioplates HD6 (Sa = 6 µm) and ISO plates (Ra = 2 and 5 µm). A decamethylcyclopentasiloxane and 2-propanol-mixed solvent solution of acrylsilicone resin was prepared, and the solution was added dropwise onto the plates. After the evaporation of the solvents, the plates were cut and the cross section was analyzed using SEM-EDS. The distribution of silicon atoms at the cross-section suggested that the maximum depth of penetrating of acrylsilicone resin was larger than Ra for all the standard plates, and the surface structure was significantly different for each standard plate. In addition, cracks into which the acrylsilicone resin deeply penetrated were observed on the surface of some plates. Clear-solution-type pseudo-sunscreen samples in which UV absorbers and acrylsilicone resin were dissolved were deposited on the standard roughened PMMA plates. It was observed that the addition of acrylsilicone resin drastically changed the net UV transmission. The degree to which the hollows of the roughened surface were filled with the pseudo-sunscreen samples determined the variation of UV transmittance.

Problems on the Evaluation of the Critical Wavelength of Sunscreens for "Broad Spectrum" Approval Brought on by Viscous Fingering During Sunscreen Application.

When a viscous liquid is applied to a solid substrate, a patterned liquid layer is usually formed by the phenomenon called viscous fingering, since the moving liquid surface is in far-from-equilibrium conditions to let the morphological fluctuation to grow. Pseudosunscreen solutions were prepared and applied on a flat quartz plate. A spatially periodic stripe pattern was formed on the pseudosunscreen layer when a block applicator was used, whereas a flat surface layer was formed when a four-sided applicator was used. UV absorbance of the patterned layer was lower than that of the flat layer having the same average thickness. In addition, a larger decrease in the UV absorbance by the pattern formation was observed at wavelengths at which the UV absorbance of the flat layer was large, which was consistent with theoretical simulations. In 2011, US FDA introduced a new rule using the term "Broad Spectrum" for labeling the sunscreens. The different decrease in the UV absorbance at each wavelength was found to change the critical wavelength, which is a criterion for sunscreens to be labeled as "Broad Spectrum" protection. The result of this study makes the problem on the evaluation of the critical wavelength come to the surface.

A novel method of estimation of adiabatic wall temperature for impinging premixed flame jets

Impinging flame jets are widely used in industrial and domestic heating applications. Most of the studies in literature report heat flux and the wall temperature which are dimensional parameters. The proper way of presenting this data is in the form of Nusselt number and effectiveness which are non-dimensional parameters. In order to determine the Nusselt number (heat transfer coefficient), the knowledge of adiabatic wall temperature is essential. In the present work, a hybrid analytical–numerical method is proposed to evaluate the adiabatic wall temperature by computing the steady state adiabatic wall heat flux. Circular burner of 11.5mm diameter is used for impingement on a flat quartz plate. The Reynolds number range is 600–2400, ratio of distance from tube burner tip to impingement plate to tube burner diameter is 2–6 and the equivalence ratio is 1. The adiabatic wall temperature estimated by the present hybrid analytical–numerical method is in good agreement (within 3–5%) with the experimentally measured adiabatic wall temperature. Radial distribution of Nusselt number and effectiveness for circular tube burner are presented based on the adiabatic wall temperature estimated by the present hybrid analytical–numerical method.

Radio frequency-driven proton source with a back-streaming electron dump

This article describes an rf ion source with a back-streaming electron dump. A quartz tube, brazed to a metal plug at one end, is fused in the center of a flat quartz plate. rf power (at 13.6 MHz) is coupled to generate hydrogen plasma using a planar external antenna bonded to the window. Bonding the water-cooled rf antenna to the quartz window significantly lowers its temperature. The water-cooled metal plug serves as the back-streaming electron dump. At 1800 W, the current density of extracted hydrogen ions reaches approximately 125 mA/cm(2).

Enhanced efficiency of laser shock cleaning process by geometrical confinement of laser-induced plasma

Surface cleaning based on the laser-induced breakdown of gas and subsequent plasma and shock wave generation can remove small particles from solid surfaces. Accordingly, several studies were performed to expand the cleaning capability of the process. In this work, the cleaning process using laser-induced plasma (LIP) under geometrical confinement is analyzed both theoretically and experimentally. Two-dimensional numerical analysis is conducted to examine the behavior of the LIP shock wave under geometrical confinement for several geometries. As a result of the analysis, we propose a simple and practical method to amplify the intensity of laser-induced shock. In the proposed method, a flat quartz plate placed close to the focal point of the laser pulse confines the expansion of the LIP, allowing the plasma to expand only in one direction. As a consequence of the plasma confinement, the intensity of the shock wave produced is increased significantly. Experiments demonstrate that the enhanced shock wave can remove smaller particles from the surface better than the existing process.

Protein Nanotubes Comprised of an Alternate Layer‐by‐Layer Assembly Using a Polycation as an Electrostatic Glue

We present the synthesis and structure of various protein nanotubes comprised of an alternate layer-by-layer (LbL) assembly using a polycation as an electrostatic glue. The nanotubes were fabricated by sequential LbL depositions of positively charged polycations and negatively charged proteins into a porous polycarbonate (PC) membrane, followed by release of the cylindrical core by quick dissolution of the template with CH(2)Cl(2). This procedure provides a variety of protein nanotubes without interlayer cross-linking. The three-cycle depositions of poly-L-arginine (PLA) and human serum albumin (HSA, M(w)=66.5 kDa) into the porous PC template (pore diameter, D(p)=400 nm) yielded well-defined (PLA/HSA)(3) nanotubes with an outer diameter of 419+/-29 nm and a wall thickness of 46+/-8 nm, revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The outer diameter of the tubules can be controlled by the pore size of the template (200-800 nm), whereas the wall thickness is always constant, independent of the D(p) value. The (PEI/HSA)(3) (PEI: polyethylenimine) nanotubes showed a slightly thin wall of 39+/-5 nm. CD spectra of the multilayered (PEI/HSA)(n) film on a flat quartz plate suggested that the secondary structure of HSA between the polycations was almost the same as that in aqueous solution. The three-cycle LbL depositions of PLA and ferritin (M(w)=460 kDa) or myoglobin (Mb, M(w)=1.7 kDa) into the porous PC membrane also gave cylindrical hollow structures. The wall thickness of the (PLA/ferritin)(3) and (PLA/Mb)(3) nanotubes were 55+/-5 nm and 31+/-4 nm; it depends on the globular size of the protein (ferritin>HSA>Mb). The individual ferritin molecule was clearly seen in the tubular walls by SEM and TEM measurements.

Anomalous deswelling of porous network polymers

The phenomenon of deswelling (or volume shrinking) of various organic and inorganic materials during removal of water or other solvents is well known. Indeed, since manufacturing of many commercial products includes processes of removal of water or other liquids, all the characteristics of drying have been studied in detail. It is known that, in making many polymer articles, it is necessary to take into account the decrease in their volume during removal of residual solvents and washing liquids. Therefore, it was quite unexpected when we detected a noticeable (sometimes temporary) increase in the volume (which generally decreases in a regular manner) of polymers of various classes with porous structure during removal of water or other solvents. Such an anomalous deswelling is characteristic not only of hydrophobic hypercrosslinked polystyrenes, porous copolymers of styrene with divinylbenzene, and porous polydivinylbenzenes (including the well-known commercial sorbent XAD-4 (Rohm and Haas Co.)), but also of hydrophilic commercial ionexchange materials based on macroporous copolymers of styrene with divinylbenzene: Amberlyst-15, CT-151, and CT-175 (sulfonic cation-exchange resins) (Purolite Int.) and the polyacrylate-type anion-exchange resin A830 (Purolite Int.) [1]. In studying swelling and subsequent drying of polymer sorbents, we first applied a method for automatically recording the sizes of individual granules. Note that, previously, it was universally accepted to observe the behavior of a large sample of a granular material, where increases and decreases in the volumes of individual granules combined, thus completely masking the true behavior of the material. The sample size in swelling and deswelling was determined with a UIP-70 standard instrument for thermomechanical testing of polymers (Central Design Bureau, USSR Academy of Sciences). The sample was a single granule of regular spherical shape. Its diameter (0.6‐0.8 mm) was accurately ( ± 0.001 mm) measured under a microscope. The sample was placed in a specially drilled polished spherical cavity (1.2 mm in diameter, 1.0 mm in radius, and 0.2 mm in depth) in a quartz plate. Changes in the granule diameter were detected with a mobile quartz rod connected to a capacitive transducer of the instrument. The rod with a polished flat end (2.7 mm in diameter) touched the sample with a minimal load of 0.5 g without distorting the regular spherical shape of the sample in swelling or deswelling. Swelling and deswelling were also studied using hypercrosslinked polystyrenes obtained as a block. Test samples ( ~2 × 2 × 2 mm) were cut from a small block of synthesized hypercrosslinked product after its crushing and washing; in measurements, a test sample was placed on a flat quartz plate. The volumetric strain e sw in solvent absorption or desorption was calculated by the equation

Evolution of ordered films of copper phthalocyanine according to EPR data

The procedure for calculating the orientation distribution of molecules using the angular dependence of EPR spectra was employed to study copper(II) phthalocyanine (CuPc) films varying in thickness and obtained by depositing the molecular complex on flat quartz plates. At the first stage of deposition, a layer of the α-CuPc phase with preferable orientation of molecular stacks along the plate surface is formed. At the second stage, a layer with an orthogonal arrangement of molecular stacks is condensed over the first layer. The interaction with NO2 forms CuPc binuclear associates. Analysis of the EPR spectra made it possible to determine the symmetry of the structure and the distance between the paramagnetic Cu2+ ions; the structure of the associates has been proposed. The orientation distribution of CuPc dimers in the film depends both on the initial ordering in the film and on processing conditions. Strong disordering of molecular stacks in ordered films during the α-CuPc to α-CuPc phase transition has been found.

Interaction of ranked copper phthalocyanine films with dry nitrogen dioxide on the basis of ESR data

The calculation procedure of the orientation distribution of molecules by the angular dependence of electron spin resonance (ESR) spectra was used to study copper(II) phthalocyanine (CuPc) films of different thickness, obtained by the molecular complex deposition on flat quartz plates. In the first stage of the deposition, the formation of the layer of the α-phase of CuPc with the predominant orientation of molecular stacks (theb-axis of the crystalline lattice) along the plate surface was formed. In the second stage, the layer with the normal disposition of molecular stacks is condensed over the first layer. The copper binuclear associates were formed during the reaction of CuPc with NO2. The ESR spectra analysis allows us to make an assumption about the construction of associates and to calculate the distance between paramagnetic copper(II) ions. It was shown that the orientation distribution of axially symmetric CuPc associates in the film depends both on the initial film order and the conditions under which it was treated.

The measurement of volume fraction profiles for adsorbed polymers under compression using neutron reflectometry

A new surface force apparatus is described which enables simultaneous measurement of the interaction forces between adsorbed polymer layers as well as their surface structure by neutron reflectometry. The apparatus utilises two optically flat quartz plates that are brought together by applying a known external force. Surface force and structural profiles have been obtained for polystyrene adsorbed on quartz from cyclohexane, i.e. a poor solvent.

New crystal spectrograph designs and their application to plasma diagnostics (invited)

A special crystal monolith was fabricated for absolute measurements of x-ray wavelength. It consists of two flat quartz plates, accurately cut relative to reflecting net planes, with a fixed distance between them. Absolute wavelengths (i.e., without use of reference lines) of L-shell laser produced spectra of Cu, Ge, As, etc. have been measured in the 7.5–8.5 Å with an accuracy of Δλ/λ=10−5. Our Johann type x-ray spectrometer with a cylindrically bent quartz has been used to reveal line coincidences necessary for photopumping processes. In this scheme source-size influences are smaller, therefore, line profiles have been measured at a spectrometer resolution better than 5000. Because of its focusing in the sagittal plane, a von Hámos type x-ray spectrometer has been used to detect the small x-ray emission of subpicosecond laser-produced plasmas (E=2 mJ, t=100 fs). X-ray spectra of Al both Kα, Kβ lines and Heα-resonance line with its satellites. Finally, a multichannel x-ray microscope has been designed and fabricated. It consists of several two-dimensionally bent crystals where each of them images one x-ray line emitted by a laser-produced plasma. The spatial resolution of x-ray line images is about 5 μm, and the width of the spectral ranges is Δλ/λ=10−4 to 10−2. Thus, the spatial distribution of ions radiating in selected x-ray lines have been found being of interest in the study of population inversions.

Fabrication of microlenses by laser chemical vapor deposition

A new laser-based method was developed for fabrication of microlenses on flat quartz plates. In this method, a CO(2) laser is used to heat a quartz surface and induce thermal reactions for source gases of SiH(4) and NO. Even as-grown silicon oxide deposits have the spherical thickness distribution required for a lens at the center and this useful area can be further increased by wet etching. Microlenses were checked on a Fizeau interferometer for surface accuracy and aberrations. As a demonstration, a 14-microm thick microlens was used for collimating light from an optical fiber.

Recombination kinetics of OH radicals on a quartz wall in a propaneoxygen flame at 25 Torr

The boundary layer between a thin flat quartz plate and a propaneoxygen premixed flame at 25 Torr has been studied, under conditions where the flow is parallel to the surface of the plate. Profiles of velocity, temperature, and OH concentration have been determined. First order recombination kinetics of OH on the quartz wall are determined from these data by three different procedures: the gradient method, the integral method, and through Rosner's theory. An extension of Rosner's theory has been developed for the last of these three methods.

Determination of velocity profiles above a thin flat plate in a low pressure flame

The boundary layer between a thin flat quartz plate and a propaneoxygen premixed flame at 25 Torr has been studied, under conditions where the flow is parallel to the surface of the plate. Profiles of velocity, temperature, and OH concentration have been determined. First order recombination kinetics of OH on the quartz wall are determined from these data by three different procedures: the gradient method, the integral method, and through Rosner's theory. An extension of Rosner's theory has been developed for the last of these three methods.