Spherical Support Research Articles

Oxygen-Reduction Active Carbon Supports for Pt Cathode Catalysts in Polymer Electrolyte Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) have been widely considered one of environmentally friendly and highly efficient electric power sources for a wide variety of power applications ranging from portable and stationary power supplies to transportation. However, some of the most critical barriers to their commercialization are the intrinsic high cost and insufficient long-term performance durability. Among others, the spherical carbon black particle support used for Pt catalyst in MEAs have a number of intrinsic structural disadvantage. It is partially responsible for current insufficient performance and durability of MEAs. They include (1) inefficient O2 transport due to significant tortuosity in carbon black-based cathode, (2) non-uniform distribution of ionomer due to significant microporosity of carbon blacks, (3) catastrophic corrosion during start-up/shut-down events due to low corrosion resistance, (4) low electrical conductivity, and (5) weak binding sites with Pt nanoparticles. University at Buffalo, SUNY has developed a new type of high-surface areas (up to 850 m2/g) and large size nitrogen-diped graphene tubes (NGT) in a highly controlled manner and at high yields. The diameters of these graphene tubes can be tuned from 50 to 500 nm, which is much larger than conventiona carbon nanotubes (20 nm). It should be noted that the graphene tube is low cost using inexpensive dicyandiamide as precursors ($1-2/kg) and the synthesis method is easily scaled up. Apart from the obvious advantage of high electronic conductivity and enhanced corrosion resistance, the large tube size provided better Pt nanoparticle dispersion and more facil mass transfer including O2 and H2O. Importantly, the NGT exhibited oxygen reduction reaction (ORR) activity in acidic media comparable with state of the art PGM-free catalsyts. Thus, the novel ORR active nitrogen-doped graphene tubes are able to not only offer remarkable support effects by geometrically and electronically modifying the deposited Pt nanoparticles, but also provide a large amount of complementary nonprecious ORR active sites, thereby significantly improving the overall activity and durability of the Pt catalysts. Thus, relative to conventional carbon blacks, the highly graphitized and active N-GT is an ideal support for low-PGM catalysts for high-performance MEAs with enhanced mass transport and durability along with ideal interfaces with ionomer.

Turing pattern formation on the sphere for a morphochemical reaction-diffusion model for electrodeposition

The present paper deals with the pattern formation properties of a specific morpho-electrochemical reaction-diffusion model on a sphere. The physico-chemical background to this study is the morphological control of material electrodeposited onto spherical particles. The particular experimental case of interest refers to the optimization of novel metal-air flow batteries and addresses the electrodeposition of zinc onto inert spherical supports. Morphological control in this step of the high-energy battery operation is crucial to the energetic efficiency of the recharge process and to the durability of the whole energy-storage device. To rationalise this technological challenge within a mathematical modeling perspective, we consider the reaction-diffusion system for metal electrodeposition introduced in [Bozzini et al., J. Solid State Electr.17, 467–479 (2013)] and extend its study to spherical domains. Conditions are derived for the occurrence of the Turing instability phenomenon and the steady patterns emerging at the onset of Turing instability are investigated. The reaction-diffusion system on spherical domains is solved numerically by means of the Lumped Surface Finite Element Method (LSFEM) in space combined with the IMEX Euler method in time. The effect on pattern formation of variations in the domain size is investigated both qualitatively, by means of systematic numerical simulations, and quantitatively by introducing suitable indicators that allow to assign each pattern to a given morphological class. An experimental validation of the obtained results is finally presented for the case of zinc electrodeposition from alkaline zincate solutions onto copper spheres.

On finding an obstacle with the Leontovich boundary condition via the time domain enclosure method

An inverse obstacle scattering problem for the wave governed by the Maxwell system in the time domain, in particular, over a finite time interval is considered. It is assumed that the electric field $\mbox{\boldmath $E$}$ and magnetic field $\mbox{\boldmath $H$}$ which are solutions of the Maxwell system are generated only by a current density at the initial time located not far a way from an unknown obstacle. The obstacle is embedded in a medium like air which has constant electric permittivity $\epsilon$ and magnetic permeability $\mu$. It is assumed that the fields on the surface of the obstacle satisfy the impedance-or the Leontovich boundary condition $\mbox{\boldmath $\nu$}\times\mbox{\boldmath $H$} -\lambda\,\mbox{\boldmath $\nu$}\times(\mbox{\boldmath $E$}\times\mbox{\boldmath $\nu$})=\mbox{\boldmath $0$}$ with $\lambda$ an unknown positive function and $\mbox{\boldmath $\nu$}$ the unit outward normal. The observation data are given by the electric field observed at the same place as the support of the current density over a finite time interval. It is shown that an indicator function computed from the electric fields corresponding two current densities enables us to know: the distance of the center of the common spherical support of the current densities to the obstacle; whether the value of the impedance $\lambda$ is greater or less than the special value $\sqrt{\epsilon/\mu}$.

ПРОЕКТУВАННЯ НОВОЇ АВТОМАТИЧНОЇ СИСТЕМИ ЖИВЛЕННЯ ГІДРОСТАТИЧНИХ ОПОР

Urgency of the research. The development of technological systems requires the designers to automate the labour movement of machinery. Due to this there is a problem of automatic compensation of the gap in the pair "shaft-bearing" dynamic changes in the external load on the shaft simple design means Such design solution allows to compensate the displacement value in a short time and with high accuracy, thereby reducing the wear of the support cranks of the rotating shaft in the hydrostatic support.Target setting. One of the directions of the effective functioning of the hydrostatic support is the automatic control of stiffness and bearing capacity without changing the geometrical parameters of the bearing. In this regard, there arises a problem of increasing operational parameters of the supports due to the improvement of constructive elements of the hydrostatic node using the new controller design stiffness.Actual scientific researches and issues analysis. The problem of creating new power systems of hydrostatic supports are presented in some scientific papers. Thus, the vector field of velocities and static pressure in the well hydrostatic support are determined. The parameters of the motion of viscous fluid in the gap of the spherical support jet regulation and perspectives design of hydrostatic bearings for high speed machining of parts on machine tools are investigated.Uninvestigated parts of general matters defining. There is a problem of improving the control system of the oil wedge compensation process in combination "shaft - slide bearing" appearing during designing of automatic shaft control systems for shifting loads. Its solution would allow to reduce the oscillation, the power load on the shaft and the wear of the support cervixes.The research objective. The main objective of this work is development of theoretical approaches to the design of new power system of hydrostatic bearings for stabilizing the shaft during its displacement under load.The statement of basic materials. To stabilize the gap in hydrostatic bearings it is proposed a new power system with a regulator of stiffness, which allows to control shaft displacement under different loads directly at the point of maximum displacement, that enables timely, automatic compensation of consumption of the lubricant in the support to increase its rigidity in moments of overload. In the proposed controller, there is a primary and secondary supply system of the working fluid to the bearing pockets from one pump. In the main supply system, the fluid is supplied to pockets of support and additional power system supports the flow of liquid coming through the holes made directly in the jumper of the bearing.Conclusions. In the article theoretical bases of design of new power system hydrostatic bearings were given. The simulation of the process of working velocities formation of the fluid in the hydrostatic section of the support for additional supply of working fluid in pair "shaft-bearing" was done. The pressure force of the working fluid that occurs in the wedge-shaped gap of the bearing was defined. The dependences of liquid flow in the pocket of the hydrostatic support against displacement of the shaft under load and the amplitude of its oscillations was built.

Exact finite volume particle method with spherical-support kernels

The Finite Volume Particle Method (FVPM) is a meshless method for simulating fluid flows which includes many of the desirable features of mesh-based finite volume methods. In this paper, we develop a new 3-D FVPM formulation that features spherical kernel supports. The formulation is based on exact integration of interaction vectors constructed from top-hat kernels. The exact integration is obtained by an innovative surface partitioning algorithm as well as precise area computation of the sphere subsurfaces. Spherical-support FVPM improves the recently developed cubic-support version in two main aspects: spherical kernels have no directionality and result in smooth interactions between particles, leading to an improved method. We present three test cases that illustrate the improved accuracy and robustness brought by the spherical kernel. Although computations are 1.5 times slower on spherical support than cubic support, the cost is more than compensated by lower error with a higher convergence rate.

CLASSIFICATION OF PHOTOGRAMMETRIC POINT CLOUDS OF SCAFFOLDS FOR CONSTRUCTION SITE MONITORING USING SUBSPACE CLUSTERING AND PCA

This paper presents an approach for the classification of photogrammetric point clouds of scaffolding components in a construction site, aiming at making a preparation for the automatic monitoring of construction site by reconstructing an as-built Building Information Model (as-built BIM). The points belonging to tubes and toeboards of scaffolds will be distinguished via subspace clustering process and principal components analysis (PCA) algorithm. The overall workflow includes four essential processing steps. Initially, the spherical support region of each point is selected. In the second step, the normalized cut algorithm based on spectral clustering theory is introduced for the subspace clustering, so as to select suitable subspace clusters of points and avoid outliers. Then, in the third step, the feature of each point is calculated by measuring distances between points and the plane of local reference frame defined by PCA in cluster. Finally, the types of points are distinguished and labelled through a supervised classification method, with random forest algorithm used. The effectiveness and applicability of the proposed steps are investigated in both simulated test data and real scenario. The results obtained by the two experiments reveal that the proposed approaches are qualified to the classification of points belonging to linear shape objects having different shapes of sections. For the tests using synthetic point cloud, the classification accuracy can reach 80%, with the condition contaminated by noise and outliers. For the application in real scenario, our method can also achieve a classification accuracy of better than 63%, without using any information about the normal vector of local surface.

CLASSIFICATION OF PHOTOGRAMMETRIC POINT CLOUDS OF SCAFFOLDS FOR CONSTRUCTION SITE MONITORING USING SUBSPACE CLUSTERING AND PCA

Abstract. This paper presents an approach for the classification of photogrammetric point clouds of scaffolding components in a construction site, aiming at making a preparation for the automatic monitoring of construction site by reconstructing an as-built Building Information Model (as-built BIM). The points belonging to tubes and toeboards of scaffolds will be distinguished via subspace clustering process and principal components analysis (PCA) algorithm. The overall workflow includes four essential processing steps. Initially, the spherical support region of each point is selected. In the second step, the normalized cut algorithm based on spectral clustering theory is introduced for the subspace clustering, so as to select suitable subspace clusters of points and avoid outliers. Then, in the third step, the feature of each point is calculated by measuring distances between points and the plane of local reference frame defined by PCA in cluster. Finally, the types of points are distinguished and labelled through a supervised classification method, with random forest algorithm used. The effectiveness and applicability of the proposed steps are investigated in both simulated test data and real scenario. The results obtained by the two experiments reveal that the proposed approaches are qualified to the classification of points belonging to linear shape objects having different shapes of sections. For the tests using synthetic point cloud, the classification accuracy can reach 80%, with the condition contaminated by noise and outliers. For the application in real scenario, our method can also achieve a classification accuracy of better than 63%, without using any information about the normal vector of local surface.

Catalytic deep oxidation of NO by ozone over MnOx loaded spherical alumina catalyst

The deep oxidation of NO by ozone, converting NO into N2O5, combined with wet flue gas treatment is an attractive method for simultaneously reduction of NOx and SO2 to ultra-low concentrations. However, the long residence time required, excessive ozone usage and consequent ozone leakage are serious problems for this technology. A catalyst of MnOx loaded onto spherical alumina support material was prepared, which displayed excellent properties that would reduce the associated problems of deep oxidation of NO by ozone. Experiments performed with the stoichiometric O3/NOx ratio, 1.5, showed an NO2 concentration reduction from 600ppm to 100ppm at 100°C after 0.12s residence time, and an ozone leakage of less than 20ppm. The NO deep oxidation efficiency exceeded 95% for O3/NOx >1.57, and the catalyst showed good stability, even with SO2. A mechanism for catalytic deep oxidation of NO by ozone was proposed, with two pathways based on the catalytic decomposition of ozone. In the first pathway, ozone is decomposed into active oxygen atoms on the catalyst surface; in the second pathway, the manganese(ΙІІ) was oxidized into manganese(IV) and manganese(VII) by the decomposition of ozone. Subsequently, NO2 adsorbed on the catalyst surface is oxidized by active oxygen atoms or oxidized manganese ions, generating NO3 and nitrates. Finally, N2O5, formed by the combination of NO2 and NO3, is desorbed from the catalyst surface. The results of several characterizations, including XRD, XPS, H2-TPR, TGA, TPD, FTIR, and BET, revealed that the second mechanism was the most dominant during the catalytic ozonation process. Additionally, the presence of ozone improved the catalyst adsorption of NOx, and O2, especially with exposure to SO2, and demonstrated better performance regarding SO2 poisoning than catalytic oxidation of NO by O2.

Immobilized lysozyme for the continuous lysis of lactic bacteria in wine: Bench-scale fluidized-bed reactor study

Lysozyme from hen egg white (HEWL) was covalently immobilized on spherical supports based on microbial chitosan in order to develop a system for the continuous, efficient and food-grade enzymatic lysis of lactic bacteria (Oenococcus oeni) in white and red wine. The objective is to limit the sulfur dioxide dosage required to control malolactic fermentation, via a cell concentration typical during this process.The immobilization procedure was optimized in batch mode, evaluating the enzyme loading, the specific activity, and the kinetic parameters in model wine. Subsequently, a bench-scale fluidized-bed reactor was developed, applying the optimized process conditions. HEWL appeared more effective in the immobilized form than in the free one, when the reactor was applied in real white and red wine. This preliminary study suggests that covalent immobilization renders the enzyme less sensitive to the inhibitory effect of wine flavans.

Support and Catalyst for the alkylation of benzene by ethylene process

<p>A method for preparation of a spherical alumina support with preset porous structure for a catalyst of benzene alkylation with ethylene has been developed. The process of the support manufacture has been adjusted in a pilot installation, and an industrial installation for production of alumina support for the alkylation catalyst has been designed and built at the Shevchenko Plastics Plant (Aktau, Kazakhstan).</p>

Analytical, numerical and experimental stress assessment of the spherical tank with large volume

Original scientific paper This paper presents designing of spherical tank using combination of analytical procedure with FEM analysis and experimental testing in order to minimize design time and verify design strength. Analytical procedure for calculation of the tank strength in the initial stages of design process is briefly presented. Based on analytical results, tank is dimensioned and FEM model is created. FEM analysis is used to identify areas with high concentration of stresses. FEM results showed that equivalent value of stress at the points of spherical tank support exceeds the values of yield stress, but this exceedance is not significant and in very small area, so overall design was deemed worthy. Experimental measurements verified FEM results that it is not necessary to reinforce the spherical tank at the points of support. After 8 months experiments were repeated giving the same results as the original measurements, thus justifying decision not to reinforce tank supports.

Pd–Ni catalyst over spherical nanostructured Y2O3 support for oxy-CO2 reforming of methane: Role of surface oxygen mobility

Various sizes of monodisperse spherical Y2O3 particles were synthesized using homogeneous precipitation method as support of Pd–Ni catalysts for oxy-CO2 reforming of methane reaction. Characterization results show that particle size and crystal size of Y2O3 particles decreases with decreasing pH of precursor solution from Y5 to Y3. TPR results of Y2O3 particles show that the intensity of reduction peaks increases from Y5 to Y3 while the position of those peaks shifts to lower temperature from Y5 to Y3, suggesting that the surface oxygen mobility of Y2O3 particles increases from Y5 to Y3 due to decrease in crystal size of Y2O3 particles. Catalytic activity results show that CH4 and CO2 conversions as well as H2 and CO production rates increase from Pd–Ni/Y5 catalyst to Pd–Ni/Y3 catalyst. In contrast, the H2/CO ratio and carbon deposition rate decreases from Pd–Ni/Y5 catalyst to Pd–Ni/Y3 catalyst. These results show that the highest surface oxygen mobility on Pd–Ni/Y3 catalyst plays important roles in high catalytic activity and suppression of carbon deposition on Pd–Ni/Y3 catalyst in oxy-CO2 reforming of methane reaction.

Asymmetric nanoparticle assembly via simple mechanical pressing using relative hardness of materials

We report a new strategy to achieve asymmetric assembly of nanoparticles on spherical support using the relative hardness of silica particles and aluminum plate. The mechanical pressing of a two-dimensional monolayer of amine-modified silica spheres resulted in partial embedding of silica spheres in the aluminum plate as silica has higher hardness than aluminum plate. The resulting partial embedding of silica spheres provided a template for asymmetric surface decoration with gold nanoparticles. The attachment of gold nanoparticles on the exposed amine modified silica spheres and the subsequent retrieval of silica spheres resulted in asymmetric silica spheres partially decorated with gold nanoparticles. This simple approach provides a potential tool to prepare asymmetric modification of various colloidal particles with various functional nanoparticles.

A simple and promoter free way to synthesize spherical γ-alumina with high hydrothermal stability

It is of great industry interest to develop spherical γ-Al2O3 support with high surface area and high hydrothermal stability. In this work, we developed a simple and promoter free way to prepare spherical γ-Al2O3 support with high hydrothermal stability from homemade pseudoboehmite with high surface area. The structure, morphology, pore structure and hydrothermal stability of the prepared materials were characterized and analyzed by various techniques such as XRD, SEM, TEM and low temperature N2 adsorption. The pseudoboehmite has a large BET surface area (SBET) of 444m2g−1 and the spherical γ-Al2O3 has high hydrothermal stability under the investigated conditions. After hydrothermal treatment at 600°C for 192h, the SBET of the spherical γ-Al2O3 remains 183m2g−1, which is much higher than that of 148m2g−1 for the commercial γ-Al2O3 from Sasol.

Effect of a double‐structured microporous polymer support on the catalytic activity, stability and aggregation behavior of immobilized enzymes

AbstractA double‐structured microporous polymer composite support consisting of a microporous skeleton for protection of immobilized enzymes and a gel‐like polymer bearing different functionalities has been synthesized for immobilization of various enzymes. Among three approaches based on two types of interactions (physical and chemical), we found that under our experimental conditions the covalent bonding between amine moieties of enzymes and epoxide groups of the support was the best, with enzyme leaching being reduced to as low as zero for nine enzymes and catalytic activities increased by factors of 1–4 for two lipases. The improvement in catalytic activity could be attributed to the amphiphilic soft gel which might create a kind of lipid–water interface or microenvironment in aqueous solution, favoring the interfacial activation of certain lipases. Furthermore, the thermal and operational stability, and reusability of all the enzymes could be enhanced to varying degrees. We also found that enzyme aggregates of different sizes could be formed on the spherical support surface at quite low enzyme concentrations, which might also influence the final catalytic activities of the immobilized enzymes. © 2015 Society of Chemical Industry

The heterogeneous gas with singular interaction: generalized circular law and heterogeneous renormalized energy

We introduce and analyze d-dimensional Coulomb gases with random charge distribution and general external confining potential. We show that these gases satisfy a large-deviation principle. The analysis of the minima of the rate function (which is the leading term of the energy) reveals that, at equilibrium, the particle distribution is a generalized circular law (i.e. with spherical support but not necessarily uniform distribution). In the classical electrostatic external potential, there are infinitely many minimizers of the rate function. The most likely macroscopic configuration is a disordered distribution in which particles are uniformly distributed (for d = 2, the circular law), and charges are independent of the positions of the particles. General charge-dependent confining potentials unfold this degenerate situation: in contrast, the particle density is not uniform, and particles spontaneously organize according to their charge. In this picture the classical electrostatic potential appears as a transition at which order is lost. Sub-leading terms of the energy are derived: we show that these are related to an operator, generalizing the Coulomb renormalized energy, which incorporates the heterogeneous nature of the charges. This heterogeneous renormalized energy informs us about the microscopic arrangements of the particles, which are non-standard, strongly dependent on the charges, and include progressive and irregular lattices.

Retrofitting of Fixed-Bed Heterogeneous Reactors for Glucose Isomerization

A retrofitting strategy is proposed here that can enhance the conversion level while significantly reducing the pressure drop in fixed-bed glucose isomerization reactors. The proposed strategy utilizes hollow support matrix for enzyme immobilization instead of commonly used solid spherical support. The absence of core in hollow catalytic support helps to lower diffusional resistances, thus ensuring a better utilization of the catalytic material. This leads to higher conversion in the reactor. Moreover, the use of hollow packing yields high bed void fraction, which helps to substantially lower the pressure drop. Specifying the proposed hollow support matrix as being either cylindrical or ring shaped, a rigorous heterogeneous model for the glucose isomerization reactor is developed here. The model validity is first tested by using reported experimental data for spherical support. Using the present model, the reactor performance can be optimized in terms of shape parameters of the proposed hollow support for enzyme immobilization.

In situ synthesis and properties of ZSM-5/α-Al2O3 composite

In this work, we have developed an in situ growth method to synthesize spherical ZSM-5/α-Al2O3 composite on spherical α-Al2O3 and investigated the morphology, structure, and properties of this composite using scanning electron microscope (SEM), powder X-ray diffraction analysis (XRD), NH3-temperature program desorption (NH3-TPD) and low temperature N2 adsorption–desorption isotherm (BET). The results show that ca. 2.4wt% ZSM-5 has been formed in the composite with a Si/Al ratio of 46.5 and an average particle size of 8.04μm. Furthermore, the formed ZSM-5 markedly enhances the surface acidity and the BET surface area of spherical α-Al2O3 support.

A facile one‐step method for spherical support preparation of Ziegler‐Natta catalyst

ABSTRACTThis study reports a novel one‐step method to synthesize a new spherical support for Ziegler‐Natta catalyst under moderate condition. The support is obtained from a dispersion system where the particle stabilizer polyvinylpyrrolidone plays a main role to stabilize the spherical particles. The new chemical of the support is CH3CH2OMgOCH(CH2Cl)2, which is first reported here, has been approved by newly filed patents and also confirmed by solution NMR, solid state NMR, pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS), and ICP‐MS. The support and catalyst particles have uniform distributions. The catalyst prepared from this support has been evaluated with high activity. The polypropylene obtained has high isotacticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41014.

Pore Structure and Bifunctional Catalyst Activity of Overlayers Applied by Atomic Layer Deposition on Copper Nanoparticles

We present a model system, based on spherical nonporous supports, to facilitate the characterization of supported metal catalysts stabilized by atomic layer deposition (ALD) against sintering and leaching under liquid-phase conditions. Calcination at high temperatures (973 K) produces pores in the ALD overcoat, and we image these pores using scanning transmission electron microscopy and electron energy loss spectroscopy (STEM/EELS). We determine the size of these pores to be ∼1 nm using small-angle X-ray scattering (SAXS). Finally, we demonstrate the use of ALD to synthesize novel bifunctional catalysts by the addition of an acidic oxide layer to the stabilizing overcoat.