The Experts below are selected from a list of 10410 Experts worldwide ranked by ideXlab platform
J. P. Pereira-ramos - One of the best experts on this subject based on the ideXlab platform.
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Enhanced electrochemical properties of ball-Milled γ′-V2O5 as cathode Material for Na-ion batteries: A structural and kinetic investigation
Journal of Power Sources, 2021Co-Authors: Rita Baddour-hadjean, Marianne Safrany Renard, J. P. Pereira-ramosAbstract:The recent intensive research for cathode Materials beyond Li-ion batteries has revitalized interest in V2O5 due to its high reversible capacity. Among the various polymorphs, γ'-V2O5 exhibits a unique corrugated layered structure that promotes the insertion of guest species. However, when used as cathode Material for SIB, this Material suffers from a 50% first charge efficiency that prevents the full benefit of its high discharge capacity of 140 mAh g-1. Herein, we demonstrate and explain the effectiveness of a ball-milling approach to overcome this strong limitation. Several positive impacts of particle size reduction are highlighted: the charge efficiency is increased to 90%, allowing a 2-fold enhancement of the available capacity upon cycling (120 mAh g-1 after 50 cycles at C/2). The Na insertion mechanism investigated by XRD and Raman spectroscopy shows a peculiar behavior with wide solid solution domains at the expense of the diphasic region. The kinetics study reveals a faster diffusivity in the ball-Milled Material and enhanced Na diffusion in the single-phase region. Both structural and kinetic reversibility account for the high performance here achieved for γ'-V2O5: a high working voltage of 3.2 V vs Na + /Na, a high rate capability, excellent charge efficiency and good cycle life.
Helena Sovova - One of the best experts on this subject based on the ideXlab platform.
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rate of the vegetable oil extraction with supercritical co2 i modelling of extraction curves
Chemical Engineering Science, 1994Co-Authors: Helena SovovaAbstract:Abstract During the extraction from Milled vegetable Material, the easily accessible solute from the cells opened by milling is extracted first, and the slower extraction of the solute protected by the cell walls follows. Mathematical models based on the assumption of plug flow of supercritical solvent through a fixed bed of Milled Material were published for both extraction periods. A new model with analytical solution was developed on the basis of these models. Extraction parameters can be evaluated by comparison of extraction curves calculated by the model with experimental data.
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rate of the vegetable oil extraction with supercritical co2 ii extraction of grape oil
Chemical Engineering Science, 1994Co-Authors: Helena Sovova, J Kucera, J JežAbstract:Abstract Grape oil was extracted with carbon dioxide at 280 bar and 40°C. Effect of milling of grape seeds, solvent flow rate and flow direction on the course of extraction was investigated. Mass transfer coefficients in the supercritical and solid phases were evaluated from extraction curves using a plug-flow model. While the assumption of plug flow was confirmed in the experiments with downflow of CO 2 through the bed of Milled Material, the extraction with upflow of CO 2 was retarded due to the natural convection. The smaller was the amount of Milled seeds in the extractor and the slower was the upward flow, the more pronounced was this effect. A model with parallel plug flows was able to give good representation of the extraction curves measured with upflow.
R Schulz - One of the best experts on this subject based on the ideXlab platform.
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hydriding behavior of mg al and leached mg al compounds prepared by high energy ball milling
Journal of Alloys and Compounds, 2000Co-Authors: S Bouaricha, Jeanpol Dodelet, Daniel Guay, Jacques Huot, S Boily, R SchulzAbstract:The structure and hydrogen absorption properties of Mg:Al alloys prepared by high-energy ball milling were studied over the whole compositional range. These Materials were prepared in their as-Milled and Al-leached forms. The latter are obtained from the former Materials by leaching out Al in a 1 N NaOH solution. The structure of the various alloys was determined by X-ray diffraction. The structure of the Material in the hydrided state was also determined in some cases. In the as-Milled state, hcp Mg(Al) with a small proportion of Mg17Al12 and fcc Al(Mg) are formed at Mg:Al (90:10) and (20:80) compositions, respectively. At intermediate (58:42) and (37:63) compositions, the intermetallic Mg17Al12 and Mg3Al2 phases are formed, respectively. Following leaching, the Al content of Mg:Al (90:10) and (20:80) varies from 10.4 and 77.0 to 3.0 and 51.0 at.%, respectively. In both cases, noticeable change in the XRD pattern confirms that bulk dissolution of Al has been achieved. There is a two-fold increase in the specific surface area of Mg:Al (90:10) following leaching of Al. In the case of Mg:Al with intermediate compositions, dissolution of Al, if any, does not lead to discernable modification in the structure of the Material. The measured hydrogen capacity of the as Milled Material decreases with Al content, from H/M=1.74 for pure un-Milled Mg, to 1.38 for Mg:Al (90:10), and then to 1.05 for Mg:Al (75:25). In each case, there is a further 10–15% decline of the hydrogen absorption capacity after leaching. In the case of Mg:Al (58:42), which basically only contains a nanocrystalline Mg17Al12 intermetallic phase, hydriding leads to the formation of MgH2 and Al. This reaction is totally reversible and Mg17Al12 is recovered upon de-hydriding. In each case, there is an increase in the kinetics of hydrogen absorption and desorption following Al leaching.
I. R. Pashby - One of the best experts on this subject based on the ideXlab platform.
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abrasive water jet controlled depth milling of ti6al4v alloy an investigation of the role of jet workpiece traverse speed and abrasive grit size on the characteristics of the Milled Material
Journal of Materials Processing Technology, 2005Co-Authors: G Fowler, P.h. Shipway, I. R. PashbyAbstract:Abstract Due to difficulties in the use of traditional mechanical methods to mill of difficult-to-machine Materials (especially in thin section), methods such as chemical milling or etching have commonly been employed. However, increasing legislative restriction on disposal of effluent has resulted in an increase in the environmental costs of such processes, and has prompted examination of alternative processes for milling to a controlled depth. Abrasive water-jet (AWJ) technology is used in a routine manner in manufacturing industry to cut Materials that are difficult to cut by other methods. A similar process, where AWJ is used for controlled depth milling (CDM) is thus considered here. The main problem to be solved in the use of AWJ as a CDM technique is that of tolerance on depth, surface waviness and surface roughness of the Milled area. In the current work, the effects of jet–workpiece traverse speed, number of passes of the jet and abrasive grit size on the Material removal rate, surface waviness and surface roughness are investigated. Traverse speed is shown to govern the operative mechanism of Material removal and thus the Material removal rate. It is also shown that the surface waviness can be reduced as the traverse speed is increased, but it should be noted that waviness increases with number of passes of the jet over the workpiece. The surface roughness is not strongly dependent on traverse speed. Smaller sized grit leads to a reduction in Material removal rate but also to a decrease in both waviness and roughness.
Rita Baddour-hadjean - One of the best experts on this subject based on the ideXlab platform.
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Enhanced electrochemical properties of ball-Milled γ′-V2O5 as cathode Material for Na-ion batteries: A structural and kinetic investigation
Journal of Power Sources, 2021Co-Authors: Rita Baddour-hadjean, Marianne Safrany Renard, J. P. Pereira-ramosAbstract:The recent intensive research for cathode Materials beyond Li-ion batteries has revitalized interest in V2O5 due to its high reversible capacity. Among the various polymorphs, γ'-V2O5 exhibits a unique corrugated layered structure that promotes the insertion of guest species. However, when used as cathode Material for SIB, this Material suffers from a 50% first charge efficiency that prevents the full benefit of its high discharge capacity of 140 mAh g-1. Herein, we demonstrate and explain the effectiveness of a ball-milling approach to overcome this strong limitation. Several positive impacts of particle size reduction are highlighted: the charge efficiency is increased to 90%, allowing a 2-fold enhancement of the available capacity upon cycling (120 mAh g-1 after 50 cycles at C/2). The Na insertion mechanism investigated by XRD and Raman spectroscopy shows a peculiar behavior with wide solid solution domains at the expense of the diphasic region. The kinetics study reveals a faster diffusivity in the ball-Milled Material and enhanced Na diffusion in the single-phase region. Both structural and kinetic reversibility account for the high performance here achieved for γ'-V2O5: a high working voltage of 3.2 V vs Na + /Na, a high rate capability, excellent charge efficiency and good cycle life.