Showing papers on "Active surface published in 2017"

Activation of surface oxygen sites on an iridium-based model catalyst for the oxygen evolution reaction

Abstract: The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices; however, deeper mechanistic understanding is required to design enhanced electrocatalysts for the reaction. Current understanding of the OER mechanism based on oxygen adsorption on a metallic surface site fails to fully explain the activity of iridium and ruthenium oxide surfaces, and the drastic surface reconstruction observed for the most active OER catalysts. Here we demonstrate, using La2LiIrO6 as a model catalyst, that the exceptionally high activity found for Ir-based catalysts arises from the formation of active surface oxygen atoms that act as electrophilic centres for water to react. Moreover, with the help of transmission electron microscopy, we observe drastic surface reconstruction and iridium migration from the bulk to the surface. Therefore, we establish a correlation between surface activity and surface stability for OER catalysts that is rooted in the formation of surface reactive oxygen.

Ambient Humidity Influence on CO Detection with SnO2 Gas Sensing Materials. A Combined DRIFTS/DFT Investigation

Abstract: Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and first-principles calculations are performed to investigate the different ways in which water reacts with a SnO2 surface and to evaluate the cross-interference of humidity on the detection of CO. Two different materials, chosen because of their very different properties, are investigated. The experimental results are interpreted with the help of theoretical modeling of two clean and defective surfaces, namely, (110) and (101). The experimental results show, and the theoretical calculations confirm, that water vapor can interfere with the CO detection in different ways depending on the active surface and the concentration of oxygen vacancies. This is related to the different ways in which the water vapor reacts with tin oxide: on the one hand, it can reduce the (101) surface; on the other hand, it can heal the oxygen vacancies of the defective (110) surface.

High-Content Metallic 1T Phase in MoS2-Based Electrocatalyst for Efficient Hydrogen Evolution

Abstract: Realizing high-efficiency hydrogen evolution in cost-effective and long-lasting electrocatalysts is critical for global production of clean and sustainable chemical fuels. Here, via modulating the metallic 1T phase in 2H MoS2 nanosheets, we greatly improved the conductivity and effective active sites for highly efficient electrocatalytic hydrogen evolution. The as-synthesized 1T-2H MoS2 electrocatalyst with a high 1T-phase content of 50% can significantly increase the charge concentration by an order of magnitude and triple the effective active surface sites, successfully boosting the hydrogen evolution reaction (HER) at a quite low overpotential of 126 mV at 10 mA/cm2 and a small Tafel slope of 35 mV/dec. Ultraviolet photoelectron spectroscopy and electrochemical characterization reveal that the valence band edges of 1T-2H MoS2 are upshifted by 0.15–0.36 eV, which obviously enhances the charge transfer ability of the surface active sites in the basal plane of MoS2 for high HER performance.

Promoted Iron Nanocrystals Obtained via Ligand Exchange as Active and Selective Catalysts for Synthesis Gas Conversion

Abstract: Colloidal synthesis routes have been recently used to fabricate heterogeneous catalysts with more controllable and homogeneous properties. Herein a method was developed to modify the surface composition of colloidal nanocrystal catalysts and to purposely introduce specific atoms via ligands and change the catalyst reactivity. Organic ligands adsorbed on the surface of iron oxide catalysts were exchanged with inorganic species such as Na2S, not only to provide an active surface but also to introduce controlled amounts of Na and S acting as promoters for the catalytic process. The catalyst composition was optimized for the Fischer–Tropsch direct conversion of synthesis gas into lower olefins. At industrially relevant conditions, these nanocrystal-based catalysts with controlled composition were more active, selective, and stable than catalysts with similar composition but synthesized using conventional methods, possibly due to their homogeneity of properties and synergic interaction of iron and promoters.

Electrodeposition of Highly Porous Pt Nanoparticles Studied by Quantitative 3D Electron Tomography: Influence of Growth Mechanisms and Potential Cycling on the Active Surface Area

Abstract: Nanoporous Pt nanoparticles (NPs) are promising fuel cell catalysts due to their large surface area and increased electrocatalytic activity toward the oxygen reduction reaction (ORR). Herein, we report on the influence of the growth mechanisms on the surface properties of electrodeposited Pt dendritic NPs with large surface areas. The electrochemically active surface was studied by hydrogen underpotential deposition (H UPD) and compared for the first time to high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) quantitative 3D electron tomography of individual nanoparticles. Large nucleation overpotential leads to a large surface coverage of roughened spheroids, which provide a large roughness factor (Rf) but low mass-specific electrochemically active surface area (EASA). Lowering the nucleation overpotential leads to highly porous Pt NPs with pores stretching to the center of the structure. At the expense of smaller Rf, the obtained EASA values of these structures are in th...

Sardinia radio telescope finite element model updating by means of photogrammetric measurements

Abstract: The 64 m diameter Sardinia Radio Telescope (SRT), located near Cagliari (Italy), is the world’s second largest fully steerable radio telescope with an active surface. Among its peculiarities is the...

GaN surface states investigated by electrochemical studies

Abstract: We present a systematic study of electrochemically active surface states on MOCVD-grown n-type GaN in aqueous electrolytes using cyclic voltammetry and impedance spectroscopy over a wide range of potentials and frequencies. In order to alter the surface states, the GaN samples are either etched or oxidized, and the influence of the surface treatment on the defect-mediated charge transfer to the electrolyte is investigated. Etching in HCl removes substoichiometric GaO x, and leads to a pronounced density of electrochemically active surface states. Oxidation effectively removes these surface states.

An adjustment method for active reflector of large high-frequency antennas considering gain and boresight

Abstract: The design of the Qitai 110 m Radio Telescope (QTT) with large aperture and very high working frequency (115 GHz) was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision and high pointing precision. In this paper, the properties of active surface adjustment in a deformed parabolic reflector antenna are analyzed. To assure the performance of large reflector antennas such as gain and boresight, which can be obtained by utilizing an electromechanical coupling model, and satisfy them simultaneously, research on active surface adjustment applied to a new parabolic reflector as target surface has been done. Based on the initial position of actuators and the relationship between adjustment points and target points, a novel mathematical model and a program that directly calculates the movements of actuators have been developed for guiding the active surface adjustment of large reflector antennas. This adjustment method is applied to an 8 m reflector antenna, in which we only consider gravity deformation. The results show that this method is more efficient in adjusting the surface and improving the working performance.

From dull to shiny: A novel setup for reflectance difference analysis under catalytic conditions.

Abstract: We have developed an experimental setup for optically monitoring a catalytically active surface under reaction conditions. A flow reactor with optical access allows us to image the behavior of an active catalyst surface down to the millimeter length scale. We use reflectance difference measurements with 625 nm light to investigate CO oxidation on Pd(100) at 300 mbar and 320 °C. We conclude that the changes in visible contrast result from the formation of an oxide layer after surface oxidation.

Electronic component package and manufacturing method for the same

Abstract: The present disclosure relates to an electronic device package including: a frame with a through hole; an electronic component which is arranged in the through hole of the frame and has an active surface on which an electrode pad is formed and an inactive surface facing the active surface; a sealing material which covers the inactive surface of the electronic component and fills a space between the frame and the electronic component in the through hole; a rewiring layer disposed on an active surface side of the electronic component and electrically connected to the electrode pad; and a metal layer which is formed on the surface of the sealing material and faces the inactive surface of the electronic component while interposing the sealing material therebetween. Accordingly, the present invention can effectively discharge heat generated from the electronic component.

Nature of Active Sites and Their Quantitative Measurement in Two-Dimensional Pt Metal Catalysts

Abstract: Quantitative measurement of the number of active surface sites on two-dimensional (2D) catalysts is one of the most crucial points in heterogeneous catalysis because it is used to determine the turnover frequency (TOF), which refers to the catalytic activity of model catalysts. However, because of the difficulty in identifying the effective active surface area on 2D heterogeneous catalysts, there is still the assumption that each metal atom is an active site. To shed light on these issues and to bridge the activity gaps between 2D and three-dimensional (3D) heterogeneous catalysts, we present an experimental approach that uses Pt nanoparticle (NP) arrays on a thin silicon wafer probed with CO pulse chemisorption, a widely used surface-sensitive technique, to determine the number of active sites and the area of the effective active surface. A Pt thin film and Pt NP arrays with two different NP sizes (i.e., 2.1 and 4.5 nm) were prepared as model systems for 2D catalysts. The effective active metal surface area determined using CO pulse chemisorption for these 2D catalysts is 53–79% of the apparent metal surface area that was obtained by measuring the surface area based on scanning electron microscopy images. This discrepancy between the active and apparent surface area is attributed to the presence of hydrocarbon contamination and organic capping layers on the catalysts. The results indicate that estimating the active sites of 2D catalysts by apparent surface area is reasonably in agreement with the number measured by chemisorption that is used to characterize 3D nanocatalysts. This experimental technique on 2D catalysts can be expected to provide information for extracting the true TOF of product molecules on 2D catalysts in gas-phase catalytic reactions.

Effect of spatial distribution of porous matrix surface charge heterogeneity on nanoparticle attachment in a packed bed

Abstract: In this study, the effect of spatial distribution of the porous matrix surface heterogeneity on nanoparticle deposition is numerically explored using lattice Boltzmann simulation methods and tracking of individual particles with Lagrangian algorithms. Packed beds with four different patterns of surface charge heterogeneity, on which favorable surfaces for particle attachment are located at different locations, are generated. The heterogeneity is binary, so that the porous surface can either accommodate nanoparticle attachment or not. It is found that the heterogeneity pattern has a stronger effect when the rate constant for particle attachment is high, when the particle size is small, and/or when the fraction of the surface area that is favorable to attachment is about 0.5. At fixed conditions, the heterogeneity pattern with randomly and uniformly distributed active surface area is the most favorite for particle attachment, compared to those where the active surface areas are banded perpendicularly to the...

Fan-out back-to-back chip stacked packages and the method for manufacturing the same

Abstract: Disclosed is a fan-out back-to-back chip stacked package, comprising a back-to-back stack of a first chip and a second chip, an encapsulant, a plurality of vias disposed in the encapsulant, a first redistribution layer and a second redistribution layer. The encapsulant encapsulates the sides of the first chip and the sides of the second chip simultaneously and has a thickness not greater than the chip stacked height to expose a first active surface of the first chip and a second active surface of the second chip. The encapsulant has a first peripheral surface expanding from the first active surface and a second peripheral surface expanding from the second active surface. The first redistribution layer is formed on the first active surface and extended onto the first peripheral surface to electrically connect the first chip to the vias in the encapsulant. The second RDL is formed on the second active surface and extended onto the second peripheral surface to electrically connect the second chip to the vias in the encapsulant. Accordingly, the structure realizes a thin package configuration of multi-chip back-to-back stacking to reduce package warpage.

Fan-out sensor package and camera module including the same

Abstract: A fan-out sensor package includes: a first interconnection member having a through-hole; a sensor disposed in the through-hole of the first interconnection member and having an active surface having connection pads and microlenses disposed thereon and an inactive surface opposing the active surface; an encapsulant encapsulating at least portions of the first interconnection member and the active surface or the inactive surface of the sensor; and a second interconnection member disposed on the first interconnection member and the inactive surface or the active surface of the sensor. The first interconnection member and the second interconnection member include, respectively, redistribution layers electrically connected to the connection pads of the sensor. A camera module includes the fan-out sensor package.

Thin fan-out stacked chip package and its manufacturing method

Abstract: Disclosed is a thin fan-out stacked chip package. The stacked chip package comprises a plurality of chips stacked to each other. The electrodes of the chips and an active surface of a top chip are exposed when stacking the plurality of chips. A dummy spacer is disposed on the active surface. A plurality of partially complete bonding wires may each have a ball bond and a vertical wire formed on the ball bond. The ball bond is directly coupled to an electrode of a chip. A molding compound encapsulates the stacked chips and the partial bonding wires. The molding compound has a planar surface. And, the terminals of the partial bonding wires and a surface of the dummy spacer are exposed from the planar surface. A redistribution layer (RDL) structure is formed on the planar surface where a passivation layer covers the planar surface and the surface of the dummy spacer but the terminals of the partial bonding wires exposed from. A plurality of traces are formed on the passivation layer and are electrically connected to the terminals of the partial bonding wires. Accordingly, the risk of wire sweeping during can be lessened.

TM65 m radio telescope microwave holography

Abstract: Microwave holography is a valuable technique used in the diagnostics and adjustment of large antennas. A brief outline of the technique is given first. Then detail simulations for surface deviation and sub-reflectorr offsets solving method that applied on the TianMa 65 m are described. After several rounds of adjustments, a reflector surface accuracy 0.28 mm and repeated measurement error 0.13 mm were achieved for the TM65 antenna. At last the antenna efficiency on Ka band was measured at elevations between 45 and 60 degrees. The efficiency improved from 37% to 56% when the active surface model is loaded that is consistent with the theoretical predictions.

On the interaction of self-assembled C 60 F 18 polar molecules with the Ni(100) surface

Abstract: The current work is dedicated to investigation of the interaction between self-assembled polar molecules of fullerene fluoride C60F18 with the chemically active surface Ni(100) under radiation and heat treatments. X-ray photoelectron spectroscopy is used in combination with quantum-chemical simulation. For the first time, the transformation of an as-deposited dielectric continuous 2D thin film to a 3D island-type assembly with molecular ordering within the islands is shown to take place. The degree of coverage of the Ni surface by C60F18 islands (0.6–0.7) and their height (~6 nm) are estimated. Quantum-chemical simulation shows that the chemisorption energy of the C60F18 molecule on the Ni surface equals ~6.6 eV and fluorine atoms are located at a distance of 1.9 A above the Ni surface. The results of the investigation provide an opportunity to create nanoscale ordered structures with local changes in the work function.

In situ structural studies and gas phase visualization of model catalysts at work

Abstract: This thesis reports on in situ structural studies relevant to a catalytic surface during CO oxidation. The materials that have been studied are palladium, rhodium and an alloy of palladium and silver, with applications in emission cleaning by catalytic converters in vehicles. The studies are performed in situ allowing for observation of the gassurface interaction, which is essential when active catalysts are studied. Due to the vital role of the gas interaction for the surface structure, the gas phase in the vicinity of the catalytically active surface has also been studied in detail with spatial resolution using Planar Laser Induced Fluorescence, PLIF.In this thesis, the CO oxidation reaction has been investigated by a step-by-step approach where the oxidation and reduction of the surfaces have first been studied separately. The systematic in situ oxidation studies at high pressure(up to 1 mbar) of the Pd, Rh and Pd75Ag25 provide information about oxide growth and the chemical composition of oxide structures that may be present during CO oxidation. To achieve a better understanding of the CO oxidationreaction, the gas distribution over the surface has been studied. The results show that the pressure, gas flow and the reaction itself determine the gas phase interacting with the surface, which influences the surface structure. At highgas flow and pressure, a boundary layer is formed in the mass transfer limited regime of CO oxidation, in which the gas composition is completely different from the gas composition measured by the mass spectrometer at the outletof the reactor. If the conditions are oxygen rich, the CO concentration close to the surface, in this regime, is low. Nevertheless, a metallic Pd and Rh surface covered with chemisorbed oxygen is detected in a 1:1 ratio of CO and O2 at total pressures up to 1 mbar. Only in more oxygen rich conditions (4:1 of O2:CO), a surface oxide may be detected. (Less)

Predominant role of grafted iron(III) Schiff-base complex in oxidation of gaseous and aqueous reactants: A visible light responsive photocatalyst

Abstract: The visible light response and photocatalytic activity of covalently bonded iron(III) Schiff-base complex were evaluated by UV-DRS and photooxidation of nitric oxide under visible light exposure, respectively. In addition, this study reports the existing of dominant active sites on the surface of grafted complex toward water adsorption, which leads to the generation of hydroxyl radicals under the illumination. Moreover, the morphological analysis exhibits high surface area (575 m2/g) with an average pore diameter of 21 nm. In addition, XRD analysis shows that the characteristic peaks of the Schiff-base complex are covered by the amorphous structure of the silica network, however, the microscopic analysis reveals the crystalline structure along with the irregular shape of the particles in the grafted catalyst. Furthermore, the catalytic activity was evaluated by photooxidation of reactive blue 13 dye in aqueous solution under visible light irradiation. Also, the reaction variables such as the amount of catalyst, pH value, concentration and temperature of the dye solution were studied and discussed in detail. It seems, the enhanced activity of the photocatalyst toward the dye decolourization is a consequence of its uniform surface, large surface area, fine particles and active surface for the water adsorption.

Corrosion behaviour of the nickel based materials in an alkaline solution for hydrogen evolution

Abstract: Experimental investigations on the nickel based materials in the form of foam and solid plate have been performed. Their application as the electrodes material in an alkaline electrolyzer has been studied. Corrosion potential and Tafels parameters are defined using DC methods, and Ohmic resistance of the electrolyte using AC methods. Active surface area of the foam is defined using BET method. Obtained polarizations curves result in decrease in the resistance to charge-transfer during increasing of electrodes overvoltage. A 1500 times larger active surface of foam insured higher hydrogen evolution at the same overvoltage. As long as it is used high concentrated aqueous media of wt 25% potassium hydroxide solution, corrosion stability of used electrodes material is the first priority.

Sensor package and method of manufacturing the same

Abstract: A sensor package includes a sensor, an encapsulation layer, a redistribution layer, a photo-imageable dielectric (PID) layer and via plugs. The encapsulation layer exposes the active surface of the sensor, and the top surface of the encapsulation layer is coplanar with the active surface of the sensor. The redistribution layer covers the top surface of the encapsulation layer and the active surface of the sensor. The PID layer covers the redistribution layer, the encapsulation layer and the active surface of the sensor. The via plugs are disposed around the sensor and through the encapsulation layer. The via plugs are electrically connected to the redistribution layer and the active surface of the sensor. The cross section of the via plug at the top surface of the encapsulation layer has a first hole diameter, and the cross section of the via plug at the bottom surface of the encapsulation layer has a second hole diameter. The first hole diameter is less than the second hole diameter.

Development of active surface technology of large radio telescope antennas

Abstract: Aperture expanding and frequency upgrading of full steerable antennas make the electrical performance of the antennas difficult to guarantee, and that radio telescopes operate in a complex environment, so it has to improve the performance by some methods like mechanical or electronic compensation. To control the pointing accuracy and the detecting distance of antennas, we must adjust the position and the surface shape of shaped reflectors, in another word, the active surface adjustment is the most effective way. Therefore, this article describes the situation and status of applications of active surface adjustment. Then, it summarizes the basic principle and the applications of active surface adjustment and particularly analyzes the key technologies which include the calculation of actuator movement, the block design of main surface, the actuator design, the active surface control system and the surface profile measuring. The comparisons among four large radio telescopes of the world are discussed, which have used active surface technology. At last, it points out some suggestions on the future research of active surface technology of large radio telescopes such as QTT.

Manufacturing method of package structure

Abstract: A manufacturing method of a packaging structure is provided. First, a carrier is provided. A conductive layer is formed on the carrier. A conductive frame is formed on the conductive layer. The conductive frame is in contact with and electrically connected to the conductive layer. A chip is placed on the conductive layer. The conductive frame surrounds the chip. An insulation encapsulation is formed to encapsulate the chip, and the insulation encapsulation exposes an active surface of the chip. A redistribution layer is formed on the active surface of the chip. The redistribution layer extends from the active surface to the insulation encapsulation.

Substrate-integrated catalyst including nanocrystal metal oxide complex, production method therefor, and catalyst component

Abstract: The present invention provides a base material-integrated nanocrystalline metal oxide composite-containing catalyst and the liked, in which the surface area of a main surface (active surface) can be effectively enlarged; nanocrystalline pieces do not readily detach; the entire shape thereof can be maintained; and excellent catalytic activity is exhibited. A catalyst (1) of the present invention includes: a base material (20); and a nanocrystalline metal oxide composite (10) having a plurality of accumulated flake-like nanocrystalline pieces (12), (12) in a connected state on the surface of the base material, the flake-like nanocrystalline pieces containing a metal oxide to accumulate (20), wherein the nanocrystalline metal oxide composite (10) is configured such that an end surface of at least one of the nanocrystalline pieces (12) is connected; the nanocrystalline pieces (12) include a plurality of stacked surfaces stacked in a direction in which a main surface (14) becomes an uppermost stacked surface; and when metal atoms or oxygen atoms forming the metal oxide are regarded as main constituent atoms, a proportion by number of the main constituent atoms to the metal atoms and the oxygen atoms forming the metal oxide existing on each stacked surface is 80% or more, and the main constituent atoms have a specific crystal orientation which changes in each stack.

Adjustment amount fast determining method of large-sized shaped surface antenna active panel facing paraboloid

Abstract: The invention provides an adjustment amount fast determining method of a large-sized shaped surface antenna active panel facing a paraboloid The method comprises the steps that an antenna model and the support node of an actuator are determined; a shaped surface fitting equation and a target paraboloid standard equation are determined; the node information of all active panels of a shaped reflection surface is extracted; the node information of the e-th panel is extracted; the optimal fitting paraboloid of the active panel is calculated; the actuator support node of the e-th panel is determined; corresponding nodes of a shaped surface antenna panel and the target paraboloid are determined; the actuator adjustment amount and the root-mean-square error of all nodes of the whole adjusted reflection surface are calculated; whether antenna gain satisfies a requirement is judged; and the optimal adjustment amount of the actuator is output According to the invention, the optimal adjustment amount of the large-sized shaped surface antenna active surface actuator for the paraboloid can be directly and accurately calculated; the electric performance of the antenna is obviously improved; the precise conversion function of the antenna under two different working modes is ensured; and the method has an important academic significance and an engineering application value

Magnetic absorbing intelligent glass cleaning robot active surface

Abstract: The invention discloses a magnetic absorbing intelligent glass cleaning robot active surface. The active surface includes an active surface body, a drive mechanism, a floating structure, a circuit board, dual micro moving structures, a power source, a magnetic member, small suckers, and a micro moving upper fixing plate; the active surface body is of a rectangular hollow structure; the drive mechanism is electrically connected to the circuit board; the magnetic absorbing intelligent glass cleaning robot active surface is simple in structure, the drive mechanism of the robot active surface adopts a wheel type structure, the smaller suckers are added on the travelling wheels so as to enhance the absorbing force, and skidding due to less water on a glass surface can be avoided; damage to a robot can be reduced, and the robot can clean and wipe corners; a support wheel structure is designed into a floating structure, and the problem that the active surface cannot support an uneven glass plane well can be solved; and the glass panel can be wiped well, and the adaptive capacity of the robot to the uneven glass plane can be enhanced.