Showing papers on "Active surface published in 2016"

Metallic Ni3N nanosheets with exposed active surface sites for efficient hydrogen evolution

Abstract: Ni-Based catalysts have been considered as promising non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean energy devices. Here, atomically thin metallic Ni3N nanosheets are fabricated as the hydrogen evolution cathode, which exhibit remarkable HER activity close to that of a commercial Pt/C electrode. The Ni3N nanosheet catalyst shows an electrocatalytic current density of 100 mA cm2 at a low overpotential of 100 mV vs. RHE, a high exchange current density of 0.32 mA cm−2, a Tafel slope of 59.79 mV dec−1 and remarkable durability (little activity loss >5000 cycles) in acidic media as well as high HER activity in neutral and alkaline media. Through systematic theoretical calculations, the active surface sites of the Ni3N nanosheets are explicitly identified. The Ni atoms accompanied by surrounding N atoms on the N–Ni surface demonstrate a small ΔGH* of 0.065 eV due to the Ni–N co-effect, which act as the most active HER sites. This finding broadens our vision to realize the HER activity of 2D metallic electrocatalysts and paves the way for exciting opportunities in exploring and optimizing advanced catalysts for future energy production.

A low-cost alumina-mullite composite hollow fiber ceramic membrane fabricated via phase-inversion and sintering method

Abstract: With abundant bauxite mineral as starting material, a low-cost alumina-mullite composite hollow fiber ceramic membrane (HFCM) was fabricated via phase-inversion method followed by high temperature sintering. Process parameters, including bore fluid flow rate and air-gap distance, which affect structure and properties of the HFCM were systematically explored. A low bore fluid flow rate would lead to the deformation of inner walls of the HFCM as a result of insufficient solidification, while a large air-gap distance would induce the distortion of finger-like voids. Effects of sintering on the microstructure, pore size distribution, nitrogen gas flux and mechanical properties were investigated in details. Acid-base titration was first proposed to quantitatively determine concentration of surface active sites of membrane surface after sintering. An increase in sintering temperature leads to significantly enhancing strength but almost linearly reduces concentration of active surface hydroxyl sites. Compared with its alumina counterpart, this low-cost composite membrane can be sintered at lower sintering temperature, and exhibits higher mechanical strength and active surface hydroxyl site concentration.

Structure of the Photo-catalytically Active Surface of SrTiO3

Abstract: A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the “gold standard” for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias. While ultrahigh vacuum surface science techniques have provided useful insights, we still know relatively little about the structure of these electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a n-SrTiO3 electrode during water splitting, before and after “training” with an applied positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy at open circuit correlates this training with a 3-fold increase of the activity toward the photo-induce...

Methods and apparatus for continuous liquid interface printing with electrochemically supported dead zone

Abstract: A method of forming a three-dimensional object is carried out by: providing a carrier and an optically transparent member having a build surface, the carrier and the build surface defining a build region therebetween; filling the build region with a polymerizable liquid; irradiating the build region through the optically transparent member to form a solid polymer from the polymerizable liquid while concurrently advancing the carrier away from the build surface to form the three-dimensional object from the solid polymer, while also concurrently: (i) continuously maintaining a dead zone of polymerizable liquid in contact with the build surface by electrochemically generating a polymerization inhibitor therein from a precursor of the polymerization inhibitor, and (ii) continuously maintaining a gradient of polymerization zone (e.g., an active surface) between the dead zone and the solid polymer and in contact with each thereof, the gradient of polymerization zone comprising the polymerizable liquid in partially cured form. Apparatus for carrying out the method is also described.

Hierarchical carbon and nitrogen adsorbed PtNiCo nanocomposites with multiple active sites for oxygen reduction and methanol oxidation reactions

Abstract: Hierarchical carbon and nitrogen adsorbed PtNiCo nanocomposites with different morphologies and facets were successfully synthesized via a solvothermal method and showed high electrochemical activity and long-term stability towards the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Electrochemical results indicated that the (220) facet-terminated PtNiCo@C–N nanocubes manifest superior electro-catalytic activity compared to other morphologies and facets as well as the commercial state-of-the-art Pt/C catalyst (20%). The surface carbon and nitrogen atoms, multiple active surface sites, and synergistic electronic effects of various elements contribute to the high electro-catalytic performance of the electrocatalysts. It is worth mentioning that the carbon and nitrogen atoms were simultaneously adsorbed onto the surface of the catalysts, which can provide more multiple active sites for these nanocomposites. In order to demonstrate this result, a solvent ligand exchange method was explored to demonstrate that these multiple active sites on the surface of the catalysts can be exchanged into n-hexane solution, and thus the catalytic activity dramatically decreased. The present work highlights the carbon and nitrogen adsorbed PtNiCo@C–N nanocomposites as highly active catalysts for polymer electrolyte membrane fuel cells (PEMFCs).

Unravelling the nature, evolution and spatial gradients of active species and active sites in the catalyst bed of unpromoted and K/Ba-promoted Cu/Al2O3 during CO2 capture-reduction

Abstract: CO2 capture-reduction (CCR) is a recently developed catalytic process that combines two critical functions of the CO2 utilization path in one process, namely CO2 capture and subsequent transformation (e.g. reduction by H2) into chemical fuels or intermediates such as CO. A bifunctional catalyst material is needed and the two functions are activated by means of an isothermal unsteady-state operation (i.e. gas switching). This work employs operando space- and time-resolved DRIFTS, XAFS, and XRD to elucidate the nature and functions of Cu and the promoters. Both unpromoted and K/Ba-promoted Cu/Al2O3 catalysts were studied to illuminate the active surface species varying along the catalyst bed. The K promoter was found to uniquely facilitate efficient CO2 capture in the form of surface formates, dispersion of active metallic Cu and suppression of surface Cu oxidation. The CO2-trapping efficiency of the K-promoted catalyst is so high that CO2 capture takes place gradually along the catalyst bed towards the reactor outlet, hence creating large spatial and temporal gradients of surface chemical species. Understanding these features is of central importance to design efficient CCR catalysts. Furthermore, a completely different path for CO2 reduction was evidenced for the unpromoted and Ba-promoted Cu catalysts where CO2 can directly react with metallic Cu and oxidize its outer surface and thus releasing CO. These results also provide important new mechanistic insights into the widely investigated reverse water–gas shift reaction and the role that K and Ba promoters play.

Light-Controlled ZrO 2 Surface Hydrophilicity

Abstract: In recent years many works are aimed at finding a method of controllable switching between hydrophilicity and hydrophobicity of a surface. The hydrophilic surface state is generally determined by its energy. Change in the surface energy can be realized in several different ways. Here we report the ability to control the surface wettability of zirconium dioxide nano-coatings by changing the composition of actinic light. Such unique photoinduced hydrophilic behavior of ZrO2 surface is ascribed to the formation of different active surface states under photoexcitation in intrinsic and extrinsic ZrO2 absorption regions. The sequential effect of different actinic lights on the surface hydrophilicity of zirconia is found to be repeatable and reversibly switchable from a highly hydrophilic state to a more hydrophobic state. The observed light-controllable reversible and reproducible switching of hydrophilicity opens new possible ways for the application of ZrO2 based materials.

Semiconductor package structure and method for forming the same

Abstract: A semiconductor package structure is provided. The semiconductor package structure includes a first semiconductor die (200) including a first active surface (200a) and a first non-active surface (200b). The semiconductor package structure also includes a second semiconductor die (400) including a second active surface (400a) and a second non-active surface (400b). The second semiconductor die is stacked on the first semiconductor die. The first non-active surface faces the second non-active surface. The semiconductor package structure further includes a first redistribution layer (RDL) structure. The first active surface faces the first RDL structure (800). In addition, the semiconductor package structure includes a second RDL structure (600). The second active surface faces the second RDL structure.

Exploiting Rayleigh Instability in Creating Parallel Au Nanowires with Exotic Arrangements.

Abstract: New types of nanowire arrangements are explored via active surface growth, where the use of Au seeds at room temperature means that the seed shape has major impacts on the subsequent nanowire growth. When Au nanorods are used as seeds, the original stripe-shape contact line with the substrate (the active surface) splits into a series of circular dots as the result of Rayleigh instability, giving coplanar nanowire bundles. The influence of a solid system by Rayleigh instability is exceptional, permitted by the dynamic active surface. The splitting is driven by the tendency to minimize the surface of the newly emerged nanowire section, whereas Rayleigh instability is responsible for overcoming the kinetic barriers. As a result, the average distance between the nanowires is only a few nanometers, much smaller than conventional lithographic methods. Conical and tubular bundles of nanowires are formed at low seed density, where the excessive growth material available for each seed leads to expansion and splitting of the active surface under the influence of both the diffusion limited growth and Rayleigh instability. Further designs of nanowire-based Au architectures demonstrate the feasibility of combining the multiple control of the system for new synthetic advances.

Metrological Aspects of Abrasive Tool Active Surface Topography Evaluation

Abstract: Analysis of the shape and location of abrasive grain tips as well as their changes during the grinding process, is the basis for forecasting the machining process results. This paper presents a methodology of using the watershed segmentation in identifying abrasive grains on the abrasive tool active surface. Some abrasive grain tips were selected to minimize the errors of detecting many tips on a single abrasive grain. The abrasive grains, singled out as a result of the watershed segmentation, were then analyzed to determine their geometric parameters. Moreover, the statistical parameters describing their locations on the abrasive tool active surface and the parameters characterizing intergranular spaces were determined.

Surface State Mediated Electron Transfer Across the N-Type SiC/Electrolyte Interface

Abstract: Understanding the mechanisms of charge transfer across the semiconductor/electrolyte interface is a basic prerequisite for a variety of practical applications. In particular, electrically active surface states located in the semiconductor band gap are expected to play an important role, but direct experimental evidence of surface states has proven to be challenging, and further experimental studies are required to verify their influence on the exchange of charge carriers between semiconductor and electrolyte. Due to its wide band gap, chemical stability, and controllable surface termination, silicon carbide (SiC) provides an excellent model system for this purpose. In this report, we provide a fundamental electrochemical study of n-type 6H-SiC and 4H-SiC electrodes in aqueous electrolytes containing the ferricyanide/ferrocyanide redox couple. Cyclic voltammetry and impedance spectroscopy measurements are performed over a wide range of potentials to determine the energetic positions of the SiC band edges a...

Standalone ethanol micro-reformer integrated on silicon technology for onboard production of hydrogen-rich gas

Abstract: A novel design of a silicon-based micro-reformer for onboard hydrogen generation from ethanol is presented in this work. The micro-reactor is fully fabricated with mainstream MEMS technology and consists of an active low-thermal-mass structure suspended by an insulating membrane. The suspended structure includes an embedded resistive metal heater and an array of ca. 20k vertically aligned through-silicon micro-channels per square centimetre. Each micro-channel is 500 μm in length and 50 μm in diameter allowing a unique micro-reformer configuration that presents a total surface per projected area of 16 cm(2) cm(-2) and per volume of 320 cm(2) cm(-3). The walls of the micro-channels become the active surface of the micro-reformer when coated with a homogenous thin film of Rh-Pd/CeO2 catalyst. The steam reforming of ethanol under controlled temperature conditions (using the embedded heater) and using the micro-reformer as a standalone device are evaluated. Fuel conversion rates above 94% and hydrogen selectivity values of ca. 70% were obtained when using operation conditions suitable for application in micro-solid oxide fuel cells (micro-SOFCs), i.e. 750 °C and fuel flows of 0.02 mlL min(-1) (enough to feed a one watt power source).

Active surface geometrical control of noise in nanowire-SAW sensors

Abstract: ZnO nanowires were grown on equal areas of the active surface of a surface acoustic wave (SAW) sensor, using a range of patterns: parallel lines, perpendicular lines, curved stripes and a fully covered square zone. The sensor’s frequency shift proved to be a geometry-independent parameter while noise depended significantly on geometry. A 2.5-fold variation in noise was obtained between the best (parallel stripes) and worst (compact area) patterns. A film deposited over such structures led to a further increase in noise, up to a comparable and pattern-independent value. Correlating the frequency shift increase with the sensor’s covered active area, our results suggest that patterns with a filling factor above 40% could enhance SAW sensor performance via efficient noise reduction.

Probing the electrochemical behavior of {111} and {110} faceted hollow Cu2O microspheres for lithium storage

Abstract: Transition metal oxides with exposed highly active facets have become of increasing interest as anode materials for lithium ion batteries, because more dangling atoms exposed at the active surface facilitate the reaction between the transition metal oxides and lithium. In this work, we probed the electrochemical behavior of hollow Cu2O microspheres with {111} and {110} active facets on the polyhedron surface as anodes for lithium storage. Compared to commercial Cu2O nanoparticles, hollow Cu2O microspheres with {111} and {110} active facets show a rising specific capacity at 30 cycles which then decreases after 110 cycles during the cycling process. Via advanced electron microscopy characterization, we reveal that this phenomenon can be attributed to the highly active {111} and {110} facets with dangling “Cu” atoms facilitating the conversion reaction of Cu2O and Li, where part of the Cu2O is oxidized to CuO during the charging process. However, as the reaction proceeds, more and more formed Cu nanoparticles cannot be converted to Cu2O or CuO. This leads to a decrease of the specific capacity. We believe that our study here sheds some light on the progress of the electrochemical behavior of transition metal oxides with respect to their increased specific capacity and the subsequent decrease via a conversion reaction mechanism. These results will be helpful to optimize the design of transition metal oxide micro/nanostructures for high performance lithium storage.

Semiconductor package and fabrication method thereof

Abstract: A semiconductor package includes a semiconductor die having an active surface and a bottom surface opposite to the active surface; a plurality of bond pads distributed on the active surface of the semiconductor die; an encapsulant covering the active surface of the semiconductor die, wherein the encapsulant comprises a bottom surface that is flush with the bottom surface of the semiconductor; and a plurality of printed interconnect features embedded in the encapsulant for electrically connecting the plurality of bond pads. Each of the printed interconnect features comprises a conductive wire and a conductive pad being integral with the conductive wire.

Surface of a catalyst in a gas phase

Abstract: Chemistry and structure of surface of a catalyst under a reaction condition is the crucial information for understanding catalytic mechanism since in many cases an authentic, active surface catalyzing a catalytic reaction is formed in a pretreatment or/and in a reaction between nominal catalyst and reactants. Ambient pressure X-ray photoelectron spectroscopy can be used to track surface of a catalyst under a reaction condition as the instrumentations in the last a few decades have made characterization of catalyst surface in a gas phase at Torr pressure or higher possible. It can characterize surface chemistry of a catalyst including surface composition, surface phase and surface oxygen vacancies and other information under a reaction condition and track their evolutions when the reaction condition is changed to another.

Reducing the V2O3(0001) surface through electron bombardment--a quantitative structure determination with I/V-LEED.

Abstract: The (0001) surface of vanadium sesquioxide, V2O3, is terminated by vanadyl groups under standard ultra high vacuum preparation conditions. Reduction with electrons results in a chemically highly active surface with a well-defined LEED pattern indicating a high degree of order. In this work we report the first quantitative structure determination of a reduced V2O3(0001) surface. We identify two distinct surface phases by STM, one well ordered and one less well ordered. I/V-LEED shows the ordered phase to be terminated by a single vanadium atom per surface unit cell on a quasi-hexagonal oxygen layer with three atoms per two-dimensional unit cell. Furthermore we compare the method of surface reduction via electron bombardment with the deposition of V onto a vanadyl terminated film. The latter procedure was previously proposed to result in a structure with three surface vanadium atoms in the 2D unit cell and we confirm this with simulated STM images.

A method and new parameters for assessing the active surface topography of diamond abrasive films

Abstract: This paper describes the methodology and results of research on the tribological characteristics of the surfaces of diamond abrasive films using a stereometric analysis. Abrasive films are used in various finishing processes of surfaces with very high smoothness and accuracy. A morphological analysis of surface vertexes in the plane that is parallel to the film surface and the perpendicular direction allowed an assessment of the distances between particles by means of a decomposition of the surface into Voronoi cells. When studying the formation of the aggregates of diamond particles and the spaces between them, one may infer about the machining potential of the abrasive film and determine the recommended kinematic conditions of the film that ensures the maximum use of this potential. Owing to the investigations related to the morphology of diamond abrasive films, one can observe relevant characteristic abrasive aggregates that vary in term of size and shape depending on particle sizes. Units with elongated shapes have a superior machining ability in relation to spherical-shaped units. One of significant parameters proposed that describe the technological potential of abrasive films is the edge length to width ratio of diamond units. Different operating modes are discussed. A statistical analysis of the dynamics observed of abrasive interfaces allowed a pertinent description of the abrasive process taking into consideration nominal and apparent as well as abrasively efficient morphologies.

2D sparse array optimization and operating strategy for real-time 3D ultrasound imaging

Abstract: Today, the use of 3D ultrasound imaging in cardiology is limited because imaging the entire myocardium on a single heartbeat, without apnea, remains a technological challenge. A solution consists in reducing the number of active elements in the 2D ultrasound probes to lighten the acquisition process: this approach leads to sparse arrays. The aim of this thesis is to propose the best configuration of a given number of active elements distributed on the probe active surface in order to maximize their ability to produce images with homogeneous contrast and resolution over the entire volume of interest. This work presents the integration of realistic acoustic simulations performed in a stochastic optimization process (simulated annealing algorithm). The proposed sparse array design framework is general enough to be applied on both on-grid (active elements located on a regular grid) and non-grid (arbitrary positioning of the active elements) arrays. The introduction of an innovative energy function sculpts the optimal 3D beam pattern radiated by the array. The obtained optimized results have 128, 192 or 256 active elements to help their compatibility with currently commercialized ultrasound scanners, potentially allowing a large scale development of 3D ultrasound imaging with low cost systems

Calibration and operation of the active surface of the Large Millimeter Telescope

Abstract: The Large Millimeter Telescope relies on an active primary surface to achieve its specified surface accuracy. The active primary has two functions: (1) it provides a means to correct the surface for gravitational deformations with changing elevation; and (2) it provides a capability to improve the shape of the surface in real time due to transient effects of thermal gradients within the structure. At LMT, our development work has addressed both problems and in this paper we describe the derivation of the gravity deformation model and the schemes developed to measure and improve the antenna surface during regular scientific observations.

Semiconductor package and manufacturing method thereof

Abstract: The invention relates to a semiconductor package and a manufacturing method thereof. The semiconductor package comprises a first chip, an interposer substrate, a second chip, a package and a signal line. The first chip comprises an active surface and a non-active surface which are opposite to each other. The interposer substrate comprises a first surface and a second face which are opposite to each other, and a signal electric conductive hole, and the second surface is arranged on the active surface of the first chip. The second chip is arranged on and electrically connected with the first surface of the interposer substrate. The package coats the first chip and the second chip and comprises an outer lateral surface, and the signal electric conductive hole of the interposer substrate exposes from the outer lateral surface of the package. The signal line is arranged on the outer lateral surface of the package and is electrically connected with the exposed signal electric conductive hole and the active surface of the first chip.

Integrated fan-out package and method of fabricating the same

Abstract: An integrated fan-out package including an integrated circuit, an insulating encapsulation, and a redistribution circuit structure is provided. The integrated circuit includes an active surface, a plurality of sidewalls connected to the active surface, and a plurality of pads distributed on the active surface. The insulating encapsulation encapsulates the active surface and the sidewalls of the integrated circuit. The insulating encapsulation includes a plurality of first contact openings and a plurality of through holes, and the pads are exposed by the first contact openings. The redistribution circuit structure includes a redistribution conductive layer, wherein the redistribution conductive layer is disposed on the insulating encapsulation and is distributed in the first contact openings and the through holes. The redistribution conductive layer is electrically connected to the pads through the first contact openings. A method of fabricating the integrated fan-out package is also provided.

A simulation tool assisting the design of a close range photogrammetry system for the sardinia radio telescope

Abstract: . The Sardinia Radio Telescope (SRT) is a 64 m diameter antenna, whose primary mirror is equipped with an active surface capable to correct its deformations by means of a thick network of actuators. Close range photogrammetry (CRP) was used to measure the self-load deformations of the SRT primary reflector from its optimal shape, which are requested to be minimized for the radio telescope to operate at full efficiency. In the attempt to achieve such performance, we conceived a near real-time CRP system which requires the cameras to be installed in fixed positions and at the same time to avoid any interference with the antenna operativeness. The design of such system is not a trivial task, and to assist our decision we therefore developed a simulation pipeline to realistically reproduce and evaluate photogrammetric surveys of large structures. The described simulation environment consists of (i) a detailed description of the SRT model, included the measurement points and the camera parameters, (ii) a tool capable of generating realistic images accordingly to the above model, and (iii) a self-calibrating bundle adjustment to evaluate the performance in terms of RMSE of the camera configurations.

The active surface control system for the Tian Ma Telescope

Abstract: The Tian Ma Telescope (TM) is the largest fully steerable radio telescope in Asia. It has a primary reflector of 65-m in diameter with a shaped Cassegrain configuration. The primary reflector of the TM is an active surface with 1104 actuators for the 1008 surface panels. The panels of the telescope are divided into 18 rings, and 24 fan sections. Each section includes three sub-sections. The active surface system adopts TCP/IP Ethernet network and RS-485 bus as a dominating mode of communication. The control software works on the Windows system, and adopts the object-oriented technology. The photogrammetry and phase-coherent holography has been used to set the surface to about 0.3mm at the rigging angle. The FEM model is testing now. The Out-of-Focus holography and other techniques will be used to modify the dynamic surface deformation.

Thin fan-out multi-chip stacked package structure and manufacturing method thereof

Abstract: A thin fan-out multi-chip stacked package structure including a plurality of stacked chips is provided. The electrodes of the stacked chips and the active surface of the top chip are exposed. A dummy spacer is disposed on the active surface. Each bonding wire has a bonding thread bonded to a chip electrode and an integrally-connected vertical wire segment. A flat encapsulant encapsulates the chip stacked structure and the bonding wires. Polished cross-sectional surfaces of the bonding wires and a surface of the dummy spacer are exposed by the flat surface of the encapsulant. A redistribution layer structure is formed on the flat surface. A passivation layer covers the flat surface and the surface of the dummy spacer but exposes the polished cross-sectional surfaces. Fan-out circuits are formed on the passivation layer and are connected to the polished cross-sectional surfaces of the bonding wires.

Systems and Methods for Suppressing Magnetically Active Surface Defects in Superconducting Circuits

Abstract: Systems and methods for suppressing magnetically active surface defects in superconducting quantum circuits are provided. A method includes providing one or more superconducting quantum circuits, and arranging the one or more superconducting quantum circuits in a hermetic enclosure capable of isolating the one or more superconducting circuits from ambient surroundings. The method also includes controlling an environment in the hermetic enclosure to suppress magnetically active surface defects associated with the one or more superconducting quantum circuits. In some aspects, the method further includes introducing an inert gas into the hermetic enclosure to passivate a surface of the one or more superconducting quantum circuits. In other aspects, the method further includes coating a surface of the one or more superconducting circuits with a non-magnetic encapsulation layer. In yet other aspects, the method further includes irradiating the one or more superconducting circuits using ultraviolet light.