The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
O'dwyer Colm - One of the best experts on this subject based on the ideXlab platform.
-
The influence of colloidal opal template and substrate type on 3D macroporous single and binary vanadium oxide inverse opal electrodeposition
Electrochemical Society, 2017Co-Authors: O\u27hanlon Sally, Mcnulty David, O'dwyer ColmAbstract:We report on the electrodeposition of 3D macroporous vanadium oxide inverse opals and binary inverse opals on transparent conducting oxide substrates and stainless steel and thermally oxidized stainless steel substrates. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of a colloid photonic crystal template of self-assembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 μm to 6 μm, and binary inverse opals were also electrodeposited using binary mixtures of sphere sizes. We demonstrate that the ionic diffusion that leads to growth has charge-to-mass Coulombic efficiency ranging from 60–90%, depending on the voltage used. Additionally, the tortuosity in ionic diffusion through the opal to the substrate is significantly increased when large sphere diameter templates and binary opal templates are used. Analysis of the contribution of true substrate active area and the influence of template structure on ionic diffusivity confirms that inverse opal growth is dictated by the size of opal spheres, Interstitial Void clogging by smaller spheres in binary opals, and the conductivity of the substrate active area. The crystallinity of the inverse opal is consistent and a function of applied voltage, and attains phase pure orthorhombic V2O5
-
3D vanadium oxide inverse opal growth by electrodeposition
'The Electrochemical Society', 2015Co-Authors: Armstrong Eileen, O'sullivan Maria, O'connell John, Holmes, Justin D., O'dwyer ColmAbstract:Three-dimensional vanadium pentoxide (V2O5) material architectures in the form of inverse opals (IOs) were fabricated using a simple electrodeposition process into artificial opal templates on stainless steel foil using an aqueous solution of VOSO4.χH2O with added ethanol. The direct deposition of V2O5 IOs was compared with V2O5 planar electrodeposition and confirms a similar progressive nucleation and growth mechanism. An in-depth examination of the chemical and morphological nature of the IO material was performed using X-ray crystallography, X-ray photoelectron spectroscopy, Raman scattering and scanning/transmission electron microscopy. Electrodeposition is demonstrated to be a function of the Interstitial Void fraction of the artificial opal and ionic diffusivity that leads to high quality, phase pure V2O5 inverse opals is not adversely affected by diffusion pathway tortuosity. Methods to alleviate electrodeposited overlayer formation on the artificial opal templates for the fabrication of the porous 3D structures are also demonstrated. Such a 3D material is ideally suited as a cathode for lithium ion batteries, electrochromic devices, sensors and for applications requiring high surface area electrochemically active metal oxides
Gert Desmet - One of the best experts on this subject based on the ideXlab platform.
-
Use of pressure drop profiles to assess the accuracy of Total Pore Blocking measurements of the external porosity of chromatographic columns.
Journal of chromatography. A, 2011Co-Authors: Anuschka Liekens, Joeri F. M. Denayer, Gert DesmetAbstract:By comparing the pressure drop in a column where the meso-pores of the particles have been blocked using the Total Pore Blocking (TPB) method to measure the Interstitial volume of the column with that in the same column when the particle meso-pores are fully open, it could be demonstrated in a very sensitive way that the Interstitial volume is completely deVoid of any significant amount of remaining pore blocking agent in the final phase of a TPB experiment. Monitoring the pressure signal until it returns to its original value can hence be used as a reliable indicator that all blocking agent has been removed from the Interstitial Void at the end of the flushing period. As a consequence, any small molecular weight dead volume marker that is employed in this phase can explore the full Interstitial volume, so that the value of the latter can be measured without being underestimated by the fact that some fractions of the Interstitial Void would still be occupied by the blocking agent.
-
Total pore blocking as an alternative method for the on-column determination of the external porosity of packed and monolithic reversed-phase columns.
Journal of chromatography. A, 2007Co-Authors: Deirdre Cabooter, Frédéric Lynen, Pat Sandra, Gert DesmetAbstract:An alternative method to determine the Interstitial Void volume and the external porosity inside a packed or a monolithic column was developed. The method is based on the total blocking of the mesopores of a porous support by filling them with a hydrophobic solvent. The strong interaction of the latter with the hydrophobic coating inside the pores keeps the solvent in position during the subsequent measurements. With the pores of the stationary phase material completely inaccessible for any type of polar molecules, the method allows to perform Interstitial Void measurements using small molecular weight (MW) molecules instead of the large MW molecules that need to be used in inverse size exclusion chromatography (ISEC). These small MW molecules are able to penetrate every corner of the Interstitial volume and therefore lead to a very accurate determination of the external porosity. Since only one type of molecules needs to be injected, the often troublesome regression analysis needed in ISEC is omitted as well. In the present contribution, the method has been applied to a packed bed and a monolithic column to investigate the optimal conditions of flow velocity, liquid compositions, and unretained marker selection. The robustness and the repeatability of the method are discussed as well.
Rui Zhang - One of the best experts on this subject based on the ideXlab platform.
-
facile synthesis of yolk shell ni Void sno2 ni3sn2 ternary composites via galvanic replacement kirkendall effect and their enhanced microwave absorption properties
Nano Research, 2017Co-Authors: Biao Zhao, Xiaoqin Guo, Wanyu Zhao, Jiushuai Deng, Bingbing Fan, Gang Shao, Zhongyi Bai, Rui ZhangAbstract:Yolk–shell ternary composites composed of a Ni sphere core and a SnO2(Ni3Sn2) shell were successfully prepared by a facile two-step method. The size, morphology, microstructure, and phase purity of the resulting composites were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected-area electron diffraction, and powder X-ray diffraction. The core sizes, Interstitial Void volumes, and constituents of the yolk–shell structures varied by varying the reaction time. A mechanism based on the time-dependent experiments was proposed for the formation of the yolk–shell structures. The yolk–shell structures were formed by a synergistic combination of an etching reaction, a galvanic replacement reaction, and the Kirkendall effect. The yolk–shell ternary SnO2 (Ni3Sn2)@Ni composites synthesized at a reaction time of 15 h showed excellent microwave absorption properties. The reflection loss was found to be as low as–43 dB at 6.1 GHz. The enhanced microwave absorption properties may be attributed to the good impedance match, multiple reflections, the scattering owing to the Voids between the core and the shell, and the effective complementarities between the dielectric loss and the magnetic loss. Thus, the yolk–shell ternary composites are expected to be promising candidates for microwave absorption applications, lithium ion batteries, and photocatalysis.
O\u27hanlon Sally - One of the best experts on this subject based on the ideXlab platform.
-
The influence of colloidal opal template and substrate type on 3D macroporous single and binary vanadium oxide inverse opal electrodeposition
Electrochemical Society, 2017Co-Authors: O\u27hanlon Sally, Mcnulty David, O'dwyer ColmAbstract:We report on the electrodeposition of 3D macroporous vanadium oxide inverse opals and binary inverse opals on transparent conducting oxide substrates and stainless steel and thermally oxidized stainless steel substrates. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of a colloid photonic crystal template of self-assembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 μm to 6 μm, and binary inverse opals were also electrodeposited using binary mixtures of sphere sizes. We demonstrate that the ionic diffusion that leads to growth has charge-to-mass Coulombic efficiency ranging from 60–90%, depending on the voltage used. Additionally, the tortuosity in ionic diffusion through the opal to the substrate is significantly increased when large sphere diameter templates and binary opal templates are used. Analysis of the contribution of true substrate active area and the influence of template structure on ionic diffusivity confirms that inverse opal growth is dictated by the size of opal spheres, Interstitial Void clogging by smaller spheres in binary opals, and the conductivity of the substrate active area. The crystallinity of the inverse opal is consistent and a function of applied voltage, and attains phase pure orthorhombic V2O5
Zhengwang Liu - One of the best experts on this subject based on the ideXlab platform.
-
hierarchical fe3o4 tio2 yolk shell microspheres with enhanced microwave absorption properties
Chemistry: A European Journal, 2013Co-Authors: Jiwei Liu, Renchao Che, Huajun Chen, Mengmei Liu, Zhengwang LiuAbstract:A facile and efficient strategy for the synthesis of hierarchical yolk-shell microspheres with magnetic Fe3O4 cores and dielectric TiO2 shells has been developed. Various Fe3O4@TiO2 yolk-shell microspheres with different core sizes, Interstitial Void volumes, and shell thicknesses have been successfully synthesized by controlling the synthetic parameters. Moreover, the microwave absorption properties of these yolk-shell microspheres, such as the complex permittivity and permeability, were investigated. The electromagnetic data demonstrate that the as-synthesized Fe3O4@TiO2 yolk-shell microspheres exhibit significantly enhanced microwave absorption properties compared with pure Fe3O4 and our previously reported Fe3O4@TiO2 core-shell microspheres, which may result from the unique yolk-shell structure with a large surface area and high porosity, as well as synergistic effects between the functional Fe3O4 cores and TiO2 shells.
